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6bkchf
Why does the typical wooden house built today (or buildings I've seen built as new developments) look like there isn't enough there to hold it up, yet stand to hold a fair amount of weight?
Background: I'm in the process of buying a house that is being built and have been tracking its process, week by week. I've also seen multiple apartment homes built recently and noticed that a a good chunk of the building is wooden, despite being many, many stories tall. I'm sure I have an irrational fear of it all collapsing upon itself (too many games of Jenga bias my opinion, I'll admit) out of the sheer fact that I misunderstand how structures are built today. Explain like I'm 5, just how it looks like so little wood can hold so much weight and won't collapse while I'm sleeping at night.
Engineering
explainlikeimfive
[ "dhndeu2" ]
[ "Civil engineer here. There are two parts to this: 1. There has been a shift in the way things are designed over time. When we started building things centuries ago, we didn't quite understand material properties, so we over designed our structures i.e. we put in extra to make sure it would stand up. That's part of the reason many ancient structures are still standing, they are far stronger than they need to be. As we have tested and learnt more about materials, we are able to design structures closer to what they need for their purpose. This was mostly driven by cost during recession periods, where work was more competitive, so being able to build the same structure with less material meant you could bid a lower price on the job, so you were more likely to get selected. 2. For wood in particular, we have always known it is strong (100ft redwoods for example), but the problem has been knowing how strong a particular piece of wood is. For concrete or steel, you can try a particular method of manufacture, test the product to destruction, and know with reasonable certainty that if you use the same method again you will get a product of a certain strength. Wood is grown, so every tree will be slightly different, so when we used wood before, we over designed to make sure it was strong enough. Then we developed glulam, or laminated sheets of wood that were glued together to form​ structural members. This allowed for more certainty in the strength, therefore we can design wooden structures more efficiently. TL;DR - cost pushed us to design more efficient buildings, and wood was made more reliable by gluing sheets of it together instead of just cutting trees to the required shape." ]
[ 6 ]
[ [] ]
[ "url" ]
[ "url" ]
ec87wo
What is accelerationism?
Other
explainlikeimfive
[ "fb9r340", "fbaha78" ]
[ "Some believe that capitalism inherently leads to economic injustice with a few super-rich and the rest of us dirt poor and living in servitude. They further believe that this situation will inevitably lead to an uprising of the masses and the end of capitalism. Now, accelerationists believe this too, but they also believe that instead of *fighting* this process, we should *speed it up*. They believe the process is painful but inevitable and will eventually benefit society, so it is best to get it over with as quickly as possible." ]
[ 18 ]
[ [], [ "https://prospect.org/power/bernie-hillary-ghost-ernst-thalmann/" ] ]
[ "url" ]
[ "url" ]
c04kyi
radiation causes cancer, but radiation therapy is used to beat cancer?
Biology
explainlikeimfive
[ "er16uwe", "er11rxz", "er112kv", "er11civ", "er2u6qp" ]
[ "Radiation causes DNA damage. DNA damage causes mutations. Mutations *can* cause cancer... but usually trigger apoptosis; cell suicide. Tumors are a concentrated mass of cancerous cells. In radiation therapy, *many* relatively weak beams of radiation are aimed at the tumor from all angles. They are aimed so that they ***only*** converge on the tumor; this means that the target tissues are affected tens of times more powerfully than the non-target tissues. Essentially, you irradiate the tumor with such an absurd dose of radiation that the DNA damage goes beyond the realm of mutations, and into the realm of, \"What the fuck is that molecule anymore? Certainly not DNA.\" This kills the cancer cells." ]
[ 154 ]
[ [], [], [], [], [] ]
[ "url" ]
[ "url" ]
94bffc
[deleted by user]
Other
explainlikeimfive
[ "e3jrj5e", "e3jozfy", "e3jpjw1", "e3jq290" ]
[ "The main thing that the other answers are missing is that it's not required for the jury to make decisions about the law in jury trials. the judge decides the law, they jury decides the facts. Here is a really simple example: > The Crime: Baking an unlawful cookie. > The judge's responsibility is to interpret the law, in this case, the judge determines that the law requires cookies to be baked with chocolate chips or sprinkles, but not raisins. > The jury's responsibility is to determine of the accused baked a cookie with raisins or not. That's it. So really, a jury doesn't decide if the law was broken or not, the jury decides what happened and is told whether or not that constitutes the crime. So, to get to your specific example of tax fraud, here are the jury instructions for the crime of filing a false tax return in my jurisdiction of California: > The defendant is charged with supplying fraudulent information to the Franchise Tax Board in violation of Revenue and Taxation Code section 19701(a). > To prove that the defendant is guilty of this crime, the People must prove that: > 1. The defendant repeatedly supplied information to the Franchise Tax Board over a period of two years or more; > 2. The information was fraudulent; > 3. When the defendant supplied the information, (he/she) knew that it was fraudulent; AND > 4. The defendant’s supplying of fraudulent information resulted in an estimated delinquent tax liability of at least fifteen thousand dollars. So the jury gets this info written down. All the jury has to decide then is what actually happened. It's still complicated, but it doesn't actually involve the jury making legal determinations. The jury just has to hear the evidence, decide who they believe when the evidence conflicts, and conclude if what the jury thinks happened matches up with these written requirements." ]
[ 21 ]
[ [], [], [], [] ]
[ "url" ]
[ "url" ]
7ks8vw
The theory of time travel via High Speeds
Repost
explainlikeimfive
[ "drgroki" ]
[ "Basically, by travelling really fast, time slows down for the traveller. The formula for it is [here]( URL_0 ). As you get closer and closer to the speed of light, time for you slows down faster and faster. Note that it is not a linear relationship, so travelling at 10% of the speed of light does not slow your time down by 10%. Now, for example, if you travel at 80% of the speed of the light, following the formula you see that your time slows down by 40% relative to a stationary person. In other times, the other people are going through time 60% faster than you are. So if you traveled for 1 year at the speed of the light and arrived at another planet, the people on the planet would actually have aged 1.6 years, and you had *traveled* into the future by 0.6 years." ]
[ 3 ]
[ [ "http://www.walter-fendt.de/ph14e/timedilation.htm" ] ]
[ "url" ]
[ "url" ]
cnqcbv
how audio books are made?
I just finished Stephen King's The Stand audio book on spotify (damm good listen, go check it out if you like). It had a run time of roughly 54 hours. Are these books really read word for word? I can't imagine one narrator doing this all by himself, so are there any tricks like Text to speech or something?
Technology
explainlikeimfive
[ "ewcwpn9", "ewcwuw4" ]
[ "Yes they are read word for word. It can be a long, rough grind to do it all. There's no AI tech nonsense magic. Someone literally reads it into a microphone in a booth." ]
[ 7 ]
[ [], [] ]
[ "url" ]
[ "url" ]
mr8agw
Are photons emitted from a source at infinite angles?
As I understand it, a photon is a massless particle constantly emitted in a linear direction, from any light source. When considering that the light source hits all objects, potentially billions of LY away, does this mean photons are emitted at infinite angles?
Physics
explainlikeimfive
[ "gukrjus" ]
[ "Kinda...photons are somewhat particle like but also somewhat wavelike so they have some spatial extent. They're not a point, they have \"area\" in the sense you're talking about. But if you go far enough away then the photon flux (photons per area) will drop away to below 1 and then the light is so dim that you're only getting sporadic photons, not a continuous stream. On average, they're emitted at infinite angles but any particular photon does have a direction." ]
[ 5 ]
[ [] ]
[ "url" ]
[ "url" ]
av7rlc
If Processed Meats like Salami and Ham are Class 1 Carcinogens, why do Italy and Spain have lower rates of Cancer than other countries?
Biology
explainlikeimfive
[ "ehd8o7u", "ehd7rhx" ]
[ "Your problem seems to stem from misunderstanding what a group 1 carcinogen is. it has basically nothing to do with the risk of the carcinogen. Rather, a \"group 1 carcinogen\" is one that a consensus of a particular group of appointed members of a particular board considers proven as carcinogenic to humans. What is also fairly accepted, however, is that the excess mortality of processed meats is *very low*. It is not at all like smoking, for example. So tobacco smoke and processed meats may both be group 1 carcinogen, but that does not mean eating 10g of processed meat/day is going to increase your risk like 1 cigarette/day. A small variation in smoking rates, therefore, would likely have a much higher impact on cancer rates than even a large variation in processed meat consumption between two populations." ]
[ 11 ]
[ [], [] ]
[ "url" ]
[ "url" ]
hmhi4j
Why do blacksmiths need to 'hammer' blades into their shape? Why can't they just pour the molten metal into a cast and have it cool and solidify into a blade-shaped piece of metal?
Technology
explainlikeimfive
[ "fx5uhj5", "fx58mjg", "fx5825m", "fx5nswl", "fx6eo9u", "fx577hh", "fx5jmpj", "fx57bfk", "fx5mtei", "fx57cxt", "fx58ak4", "fx5ezd1", "fx5x6dd", "fx6qe8u", "fx6uvh9", "fx6r029", "fx6wg6f", "fx7e9yq", "fx76iho", "fx5742k" ]
[ "For an analogy (obviously not a perfect one), think about pizza dough. Why not just mix the flour and water together a little bit and pour it onto a pizza-sized platter? Why spend all that effort kneading it and stretching it out? Because kneading and stretching the dough changes the form of the gluten molecules, making them all stretchy. It gives the pizza crust that nice chewy texture." ]
[ 1747 ]
[ [], [], [], [], [], [], [], [], [], [], [ "https://www.imetllc.com/training-article/phase-diagram/" ], [], [], [], [], [], [], [], [], [] ]
[ "url" ]
[ "url" ]
5ojn69
When someone talks about rendering a video, or an animation, what does that mean? And how would not rendering it affect it?
Technology
explainlikeimfive
[ "dcjsysc", "dcjs1dc", "dcjwq1l", "dcjuxzb", "dcjroi3", "dcjukz8" ]
[ "Let's compare video editing to building a car. So you're editing your video, but really it's a collection of parts. Multiple footage clips, effects like color correction, etc. The computer is able to tell you that \"yes, these parts put together make a car\" but rendering is where the parts actually get put together and consolidated into one piece. It's a little more complicated than that I think, but ELI5. If you try to play your video/move your car without rendering, the smoothness really depends on if your computer is strong enough to pick up x amount of parts at the same time. Rendering is like putting some of the car together so it can drive a little smoother." ]
[ 61 ]
[ [], [], [ "https://www.youtube.com/watch?v=4405qEhBmEM" ], [], [], [] ]
[ "url" ]
[ "url" ]
etwiev
Why is it that operating a car or bike in lower gears is better for going uphill?
I’ve had this explained to me before but I just don’t get it. Gears and transmissions in general are confusing to me.
Engineering
explainlikeimfive
[ "ffj2cwd", "ffiyuqg" ]
[ "Next time you open a door try this. First, open the door normally by pushing roughly in line where the handle is. Then, open the door by pushing close the hinges. It will be noticably harder. What your experiencing is “torque.” Essentially, it is easier to rotate an object if you apply a force farther from the axis of rotation (i.e. this is why you push a door open far from the hinges) since you produce greater torque, which is essentially a rotational force. Now look at your bike gears. If you look at the gears near the back wheel, your “lower” gears are the big gears close to the wheel, and the “higher” gears are the smaller gears farthest from the wheel. When you’re in low gear, the larger gear means you chain is pulling on the gear at a larger distance from the center of the axis of rotation, thus generating more torque and making it easier to turn the wheel. As you get faster, however, higher gears will help you produce greater speed. A smaller (higher) gear turning the same distance as a larger gear (not angular distance but actual distance around the gear) will result in greater angular velocity and thus greater angular velocity on your wheel, which means greater speed. It’s a bit tricky to explain without a physics education, but hope this helps!" ]
[ 13 ]
[ [], [] ]
[ "url" ]
[ "url" ]
fusbzi
When talking about engine sizes in a car, what is "litres" refering to?
Engineering
explainlikeimfive
[ "fmeed1m", "fmee9hb", "fmehw47", "fmeh53n", "fmeiy74", "fmehp7q", "fmej3qg", "fmeps96", "fmek047", "fmeq3b9", "fmek4yp", "fmejr37", "fmemkui" ]
[ "Car engines have spaces inside them, called cylinders, which are used to burn fuel and provide power. The total volume of those cylinders is what gives an engine its size." ]
[ 2079 ]
[ [], [], [], [], [], [], [], [], [], [], [], [], [] ]
[ "url" ]
[ "url" ]
iwhfge
How do you write a research paper without plagiarising, but all the ideas need to be found in literature?
Other
explainlikeimfive
[ "g5zz4kc", "g603shm", "g5zz611", "g60j2gt" ]
[ "Basically, when you use ideas from other books, you say them again in your own words, and you give credit to the people you got those ideas from." ]
[ 9 ]
[ [], [], [], [] ]
[ "url" ]
[ "url" ]
74tqr2
Oftentimes my grandma will tell me eating certain specific combinations of fruits and other foods will enhance sourness or sweetness. Has my grandmother developed a supreme mastery of flavors over the years or is there a trick to this?
Biology
explainlikeimfive
[ "do12o8x" ]
[ "Good chefs do this. Basically balancing flavors together so it's not all sweet or salty or sour or umami but a mixture of them. But it would still work if they were separate foods. This is the basis for wine pairing. A good BBQ sauce is tangy and sweet and spicy and savory. As an example." ]
[ 7 ]
[ [] ]
[ "url" ]
[ "url" ]
caqtej
Why did underwear become a huge standard in society? How did the notion of wearing clothes under our clothes become a huge success?
Technology
explainlikeimfive
[ "etagmzi", "etagp40" ]
[ "I seem to remember reading that it was down to having a layer in between clothes you would wear for multiple days and those you could wash/change on a regular basis so the outer clothes stayed fresher for longer." ]
[ 7 ]
[ [], [] ]
[ "url" ]
[ "url" ]
e1p0lp
Where do astronauts in space get their air from?
Everybody has to breathe and we on earth have an atmosphere, how is it done in space?
Technology
explainlikeimfive
[ "f8qvile" ]
[ "They bring up water, which is converted into oxygen & hydrogen using electricity (from solar power). They also extract O2 from waste CO2." ]
[ 9 ]
[ [] ]
[ "url" ]
[ "url" ]
5zsv39
Which doctors and nurses work in the Intensive Care Unit of a hospital? Do they all have to be experts in everything?
If the most high risk cases come through the ICU, are there specialists in each area of medicine working there?
Biology
explainlikeimfive
[ "df0qny8", "df0srdh" ]
[ "No doctor is an expert in everything. A patient will receive care from the most relevant doctors. An ICU will have doctors with a variety of specialties." ]
[ 5 ]
[ [], [] ]
[ "url" ]
[ "url" ]
h7q7i3
how does traffic start?
Other
explainlikeimfive
[ "fumjo0q", "fumk9eg" ]
[ "You said it yourself \"IF everyone moves at the same speed.\" We don't, that's not how cars or driving work. Some people see the speed limit and match it, some see it as the limit and stay below it, some people seem to see it as a challenge and go faster... crashes happen, animals/people cross the road, potholes exist, weather changes... so much can happen that will influence driving conditions." ]
[ 6 ]
[ [], [] ]
[ "url" ]
[ "url" ]
l45lrb
Why do “streaks” feel so important for quitting vices/addictions or achieving goals? For example, why does it feel like a bigger achievement to say “I haven’t had any fast food for an entire year”, than “I’ve limited the amount of fast food I’ve had in general”.
Biology
explainlikeimfive
[ "gkmitws", "gkmhfah", "gkmhwnw", "gkmixro", "gkmpbhi", "gkmla8g" ]
[ "I didn't smoke cigarettes for 425 days, which means 80,000 times that I wanted to smoke, I didn't do it. That's pretty impressive. It also helps to be like \"well shit I'm not gonna break the combo now\"" ]
[ 151 ]
[ [], [], [], [], [], [] ]
[ "url" ]
[ "url" ]
62804t
Why do large telecom, cable, and internet providers have such a culture of poor customer service?
Culture
explainlikeimfive
[ "dfkgfwv", "dfkicl0", "dfkl6fs" ]
[ "In the most simple terms, customer services does not make the company any money. In fact it COSTS them money, so they try to find ways to reduce that cost the most they are able. They only want to keep it so that the cost of lost customer revenue is less than the cost of operating the service. If lost customer revenue is more than service, they will pay to get better service, if less, they will skimp on the service budget until it reaches an equilibrium." ]
[ 15 ]
[ [], [], [] ]
[ "url" ]
[ "url" ]
818cev
Why does the pitch of a motor engine increase as I increase the revs?
After all, all I am doing is making more quick ‘bangs’ per second.
Engineering
explainlikeimfive
[ "dv18181" ]
[ "The pitch of a sound is its frequency. Higher tones have higher frequencies. So, as you rev up the engine, it's creating 'bangs' more frequently, and your ears perceive that as increased pitch." ]
[ 3 ]
[ [] ]
[ "url" ]
[ "url" ]
73qv0g
How does the Atkins Diet work?
Biology
explainlikeimfive
[ "dnsfsap", "dnt0q6p" ]
[ "Protein takes a long time to digest and can make you feel full for a long time. Carbs are sort of the opposite, they stretch your stomach if you eat a lot of them and they digest quickly leaving you feeling hungry. Low carb diets are statistically the best for losing weight consistently and often the recommended diets from dietitians however the speed difference wasn't any higher than a low fat diet, it was just more consistent. [Harvard studies]( URL_1 ) [compiled studies]( URL_0 ) The original idea of the Atkins diet was to have you eat more proteins and less carbs to feel full on less calories. The secondary goal of the new Atkins diet was a high fat versions of it which was meant to put you into ketosis. This had become almost a fad diet as of late, you can learn a lot more on the keto subreddit. Many people are very successful on it." ]
[ 8 ]
[ [ "https://www.healthline.com/nutrition/23-studies-on-low-carb-and-low-fat-diets#section2", "https://www.hsph.harvard.edu/nutritionsource/carbohydrates/low-carbohydrate-diets/" ], [] ]
[ "url" ]
[ "url" ]
7482ri
What Happens where Predators eat body parts of animals that contain large dose of Venom, like the head of a Snake or the tail of a Scorpion?
Biology
explainlikeimfive
[ "dnwdixd", "dnwmoi8", "dnwa1bn", "dnw5zje", "dnwbnrt", "dnwa4ia", "dnwao1x", "dnwmjcq", "dnwcrnq", "dnwbnsz", "dnwrw4y", "dnwf5ou", "dnwgd22", "dnx1noe", "dnwi5he", "dnw694h", "dnwfbfa", "dnwlbua" ]
[ "If the venom doesn't get stabbed into the bloodstream, then it will seem like nothing happened, and the predator will be OK. But what really happens is pretty neat. Putting something in your mouth and then swallowing it is ALWAYS safer than poking it into your bloodstream. Just like humans, many predators have a whole line of \"digesters\" that can make things safer to eat. First, there is spit - chewing and mixing with spit is important for digestion because it helps make big chunks smaller, it helps smaller chunks slide down into the stomach, and the spit helps some things start to dissolve. If you are chewing a venomous animal, there is a good chance that the chewing will burst the tissues where the venom is stored - that makes it less likely that the fangs or stingers can actually inject the venom. Once the venomous parts get into the stomach, the acids within the stomach are often strong enough to \"de-nature\" many venom proteins. \"De-nature\" basically means it changes shape to that it doesn't react the same way that it would have. Then other enzymes begin to break everything down into even smaller chemical bits. Those small chemical bits are mostly turned into new proteins that you need to rebuild your own cells, or energy that helps you move. So eating venomous animals is not a super idea, because there are some risks of the venom getting through your skin (or digestive tract lining) but the venom itself is usually not dangerous to digest. On the other hand, if you inject beef stew into your bloodstream, you could get very sick. EDIT: I'm forced to amend my dangerous comments, as follows - 1) Putting something in your mouth and then swallowing it is ALMOST ALWAYS safer than poking it into your bloodstream. If a doctor tells you otherwise, listen to your doctor. 2) Don't eat sacks of venom and don't inject things into yourself. EVER. If a doctor tells you otherwise, listen to your doctor. 3) Putting things in your butt is not quite the same as eating. But it is ALMOST ALWAYS safer to put something in your butt than it is to inject it. If a doctor tells you otherwise, listen to your doctor. 4) If you aren't sure whether to eat something, put it in your butt, or inject it, move on to something you are more familiar with. 5) I'm really surprised there weren't many responses talking about scorpions. They are good examples of animal magnetism in this crazy world." ]
[ 7347 ]
[ [], [ "https://en.wikipedia.org/wiki/Gastric_acid" ], [], [], [], [], [], [], [], [ "http://ufwildlife.ifas.ufl.edu/venomous_snake_faqs.shtml" ], [], [], [], [], [], [], [], [] ]
[ "url" ]
[ "url" ]
amjntq
How do Binoculars work
I recently wanted to buy some binoculars. How do they work and how much do they zoom in on an Image. In case i want to recognise somebody from 200m away
Technology
explainlikeimfive
[ "efmfc80", "efmhqdc" ]
[ "Common binoculars are about 7X or 8X, so a person at 200m would look like they were 25m - 30m away. Except that binoculars can't compensate for atmospheric distortion. You know that heat-wave shimmering look you see on a summer highway? There will be that kind of distortion on a figure at 200m, that you can't magnify away. But you should be able to recognize a person at that range." ]
[ 3 ]
[ [], [ "https://en.wikipedia.org/wiki/Refracting_telescope" ] ]
[ "url" ]
[ "url" ]
79hxvl
Why do burns blister and why do burn wounds remain warm long after the injury occurred?
Edit: Thanks, this is the first time I ever got more than 100 upvotes on anything. Ever.
Biology
explainlikeimfive
[ "dp23mbv", "dp28bzx", "dp2oq4z", "dp2brot", "dp2ddx0", "dp2wau6", "dp2niex" ]
[ "Burn blisters occur when the second layer of the skin is damaged, they occur to protect the underlying skin layers from more damage and infection. You could see it as the bodys/skins natural bandage, so never pop them. The skin remain warm because of the increased blood in the area to repair and replace the damaged skin." ]
[ 8036 ]
[ [], [], [], [], [], [], [] ]
[ "url" ]
[ "url" ]
grm0ft
Why do some birds like owls chickens and arachnids like wolf spiders look so "twitchy" almost like they are missing frames from a video when they move?
Biology
explainlikeimfive
[ "frzp2xp" ]
[ "Because they move faster than they can see. Once they reach a new position, they have to wait for their brains time to process the visual information from the new vantage point and decide where to go next. Move, sit still, process, move again, sit still, process. It is the same reason many birds bob their heads." ]
[ 4 ]
[ [] ]
[ "url" ]
[ "url" ]
5z7p2m
Why does the picture of high frequency TV's look like a soap opera?
Technology
explainlikeimfive
[ "dew610p", "dewj2ok" ]
[ "You could read [this article about the soap opera effect]( URL_0 ) but I'm going to eli5 this, too. Newer HD tvs have a pretty remarkable ability to transform shows that are shot in fewer frames per second (that's most shows) into more frames per second by predicting/inserting extra frames. A few important things to know: A) You can turn this effect off. See above link and lots of videos on YouTube. B) Some cinematographers & directors firmly believe that stuff shot in more frames per second is actually ideal/prettier. Avatar is a great example. It's rich and dense, but our brains are super not used to that effect. Yet. Might we someday have the bulk of our tv and cinema shot in more frames per second? Possibly. C) You're not crazy; lots of people hate the predictive technology. And now that you've seen it, you'll spot it everywhere in public tvs that have that setting turned on." ]
[ 4 ]
[ [ "https://www.cnet.com/news/what-is-the-soap-opera-effect/" ], [] ]
[ "url" ]
[ "url" ]
btnwcp
How does cutting steak against the grain affect the texture?
Biology
explainlikeimfive
[ "ep0e7lj" ]
[ "Long grain makes the meat chewy. Cutting it with the grain will leave long grains, but against it will make them smaller." ]
[ 4 ]
[ [] ]
[ "url" ]
[ "url" ]
ew42wd
Why does “cleaning” our ears with a cotton swab feel so good when we’re told not to put anything in them?
Biology
explainlikeimfive
[ "ffzsh7l", "ffzoa9p" ]
[ "Because you are touching the Vagus nerve. It's a cranial nerve and one of the longest in your body. It controls a lot of stuff, like heart rate and swallowing. Stimulation to this nerve can feel good! To the point that some women have reported to had orgasms from just stimulation to the Vagus nerve. This nerve is also the reason why touching your breasts and armpits can feel good, or makes you giggle." ]
[ 1215 ]
[ [], [] ]
[ "url" ]
[ "url" ]
c7zy6n
How does whistling produce sound?
Physics
explainlikeimfive
[ "esinmqe" ]
[ "There is some friction between your lips and the air that passes through them. This friction can cause your lips/cheeks to vibrate kinda like a violin bow on a string. You can change the note by changing the volume of your mouth, like shortening a string by placing your finger on it." ]
[ 7 ]
[ [] ]
[ "url" ]
[ "url" ]
9egq9f
Why is compiled code impossible to access unless the uncompiled source code is available. Can’t game devs get a retail ROM and decompile the code from that?
Technology
explainlikeimfive
[ "e5orjuz", "e5owrai", "e5os7ej", "e5pdlj2", "e5osdzd", "e5oweg2" ]
[ "It's not that easy. Once it's been compiled, you can't decompile it. Think of the code like the recipe for a cookie. If you have that recipe, you can make that cookie any time you want. But if the cookie is baked, you can't just look at it and figure out the recipe. You'd have hints, sure, but the full recipe can't be figured out by looking at the end product. Compiling code is complicated, and the end result can't easily be reversed." ]
[ 99 ]
[ [], [], [], [], [ "https://en.wikipedia.org/wiki/Decompiler" ], [] ]
[ "url" ]
[ "url" ]
j4mvub
If trains take so long to stop, how do subway trains stop so quickly
I know subway trains probably weigh alot less than freight trains, but I'd imagine they are still super heavy so how do they manage to stop so quick?
Engineering
explainlikeimfive
[ "g7k4nhs", "g7kub0y" ]
[ "I mean, it's an understatement to say they weigh a lot less than a freight train. A subway train car is SUBSTANTIALLY lighter than a freight train car, and the subway train is not nearly as long as a freight train normally is. A freight train can be 100+ cars, with each car weighing over 100 tons, compared to 30 or 40 tons for a subway car. A full freight train would be many multiple times heavier than a subway train." ]
[ 9 ]
[ [], [] ]
[ "url" ]
[ "url" ]
992dcj
What's the difference between platform/cliff jumping and suicide by jumping off a bridge?
Other
explainlikeimfive
[ "e4kddys", "e4kg1sb" ]
[ "One, athletes absolutely can die from cliff diving, just as suicidal people can survive jumps from bridges. The difference is that those who habitually jump from cliffs are experienced at it, and know the proper actions to reduce the likelihood of injury. In addition, they usually have friends or supporters near by to lend assistance quickly if they do come into trouble. Suicides from jumping off bridges etc. tend to lack these things - think of how many suicides aren't discovered until hours after the event." ]
[ 6 ]
[ [], [ "https://en.wikipedia.org/wiki/High_diving", "https://en.wikipedia.org/wiki/Suicides_at_the_Golden_Gate_Bridge" ] ]
[ "url" ]
[ "url" ]
ls7jgg
Why does newly formed skin on a wound feels more sensitive?
Biology
explainlikeimfive
[ "gophk23" ]
[ "New skin is actually thinner then old skin, so the nerve endings beneath it are closer to the surface and thus more sensitive to the touch." ]
[ 9 ]
[ [] ]
[ "url" ]
[ "url" ]
6a6w7h
What is/are "alternative news/facts" and why have i just started hearing the phrases in the last year or so?
Culture
explainlikeimfive
[ "dhc5jhk", "dhc8wou", "dhc575r" ]
[ "A Trump press representative, I thought it was Conway, complained that the press were focused on the facts that portrayed President Trump in a negative light. They said that \"alternative facts\" would show him in a better light, and argued for a more balanced treatment. I think they meant \"don't focus on how the Russians are working with Flint unless you also mention that the Russians aren't working with Pence\". It was an odd turn of phrase, but not actually wrong. Then the next day Sean Spicer was called called out for a false statement, and said he was promoting some \"alternative facts\" that the press wasn't covering. But, since the \"alternative fact\" in question turned out to be false, it's become a meme for \"lie\". I don't think that was the plan. Spicer was supposed to use the line on a fact that the press was ignoring, but he messed up." ]
[ 7 ]
[ [], [], [] ]
[ "url" ]
[ "url" ]
6bkfaw
Why are warm showers very sedative and cold showers very stimulating?
Biology
explainlikeimfive
[ "dhnf15q" ]
[ "The heat from a hot shower helps tightened or inflamed muscles (from stress or injury) relax and also promotes better blood flow and circulation. This, naturally, has a relaxing affect on the body. Cold water can stimulate oxygen intake via the physical shock from the temperature and can also increase heart rate, circulating blood flow. Cold water might also help relieve some muscle soreness." ]
[ 8 ]
[ [] ]
[ "url" ]
[ "url" ]
grzbgh
Why Is There No Cure for Allergies? What Makes It So Challenging to Find One?
Biology
explainlikeimfive
[ "fs282b0", "fs25gty" ]
[ "This is a good one! Put simply, allergies are a byproduct of a misguided (but well-functioning) immune system. It's difficult to find a cure because separating the immune system's natural functions to keep toxic foreign debris out (bacteria, microorganisms, dirt, etc) from its bogus overreaction to dust mites, nuts and pollen is not easy. By stopping one, you are more than likely diminishing the other. Depending on the allergy, taking antihistamines counteracts the onslaught of inflammation, sneezing and itchiness that results from the immune system's overreaction. As with all things, too much of anything is bad. It also varies between each person and among different types of allergies. As a side note, the last century's biggest war in medicine was infectious disease - bacteria, viruses, etc. This next century's biggest battles lie in genetic disease - Parkinson's, allergies, cancer, so I wouldn't be surprised if eventually we found a cure that was tailored to each individual!" ]
[ 6 ]
[ [], [] ]
[ "url" ]
[ "url" ]
menqgf
How is light bent by gravity if photons have no mass?
Physics
explainlikeimfive
[ "gsimfeg", "gsio433" ]
[ "In the theory of General Relativity (GR), gravity is not a force at all, but a curvature of spacetime. To understand how a curvature of spacetime can lead to the effects we observe around us, we have to understand how curved surfaces change the behaviour of straight lines. First things first: an object that has no force acting on it is force-free. Force-free objects do not accelerate and, therefore, move along straight lines. In a flat geometry, two straight lines which are parallel at one point will remain parallel for all times. That is, two parallel straight lines will never cross on a flat surface. So far so intuitive, right? But what happens, if those straight lines do not move across a flat surface, but instead along a curved surface? We call such straight lines on curved surfaces [geodesics]( URL_1 ). Imagine a [sphere]( URL_2 ) with two lines perpendicular to the equator. As they are both perpendicular to the same line, they are parallel at that altitude. Imagine two objects that are moving along the lines perpendicular to the equator. They start out parallel, and move in a straight line upwards. Despite the fact that neither of them is turning, the two objects that started out moving along parallel lines will meet at the north pole. Hence, despite the fact that both objects are force-free at all times, they experience relative acceleration. Such trajectories, that lead across curved surfaces without turning are called geodesics and they can be thought of as straight lines on curved surfaces. Objects under the influence of gravity follow [geodesics]( URL_1 ). As gravity curves spacetime, geodesics can experience relative acceleration despite the fact, that both objects following said geodesics are force-free. And this relative acceleration of force-free bodies is what Newton mistook for the gravitational force. According to GR, though, there is no force, only curvature which causes force-free objects to move along paths that seem accelerated to outside observers. This explains why photons are affected by gravity despite having zero mass: photons travel through spacetime and spacetime is affected by gravity. ----- For a great video on the basics of GR, check out [this]( URL_0 ) video by PBS Spacetime." ]
[ 18 ]
[ [ "https://www.youtube.com/watch?v=NblR01hHK6U", "https://en.wikipedia.org/wiki/Geodesic", "http://pi.math.cornell.edu/%7Edwh/books/eg99/Ch06/3776c40d.jpg" ], [] ]
[ "url" ]
[ "url" ]
e86g0i
With the recently made work of art using a banana taped to a white canvas being worth $100,000+ many have speculated it to be used for money laundering. How could you launder money using this piece of art? What would the process look like?
Other
explainlikeimfive
[ "fa9iobm", "fa9ifzz" ]
[ "Art in general is a great way to launder money because you can say it's worth whatever you want, and most art sales are private and anonymous. This makes it extremely easy to hide the origin of ill-gotten money. Let's say you have a million dollars of money you made from drug smuggling you need to launder. You can go to an artist and buy a bunch of their art for however much you want to pay. It's a private sale, so no one will know how much you paid or where that money came from. You can then turn around and resell that art at auction or to private collectors, and boom, you've got clean money earned from selling art. You can repeat that as many times as you like to turn that million dollars of drug money into clean money." ]
[ 10 ]
[ [], [] ]
[ "url" ]
[ "url" ]
f5d8w5
How can hackers crack a password through brute force if there's a limit of attempts?
Other
explainlikeimfive
[ "fhxy3f4", "fhxyl96", "fhxy8ri", "fhymogt" ]
[ "In some cases, a hacker might gain control of the server and be able to execute their own commands directly to the software on the server or obtain a copy of the database storing the hashed passwords. In either case, the webpage's limitations on password attempts doesn't matter because the hacker may not be using the webpage to check password attempts." ]
[ 46 ]
[ [], [], [], [] ]
[ "url" ]
[ "url" ]
5oktez
What causes the temporary inability to breathe when you've "gotten the wind knocked out of you"?
Yesterday a 250+lb dude fell right on my chest during a soccer game and for a solid ten seconds I couldn't gasp for a breathe of air. That sucked.
Biology
explainlikeimfive
[ "dck3zh4", "dckj029" ]
[ "When somebody strikes your chest, specifically the solar plexus, this makes your diaphragm contract and spasm, making you lose control over your breathing." ]
[ 35 ]
[ [], [] ]
[ "url" ]
[ "url" ]
hxjb29
What does it mean that we share 60% of our DNA with Bananas and Chickens?
Biology
explainlikeimfive
[ "fz6igmu", "fz6innr" ]
[ "There is some merit to that 60% statistic, but it's not the whole truth. First, it's important to understand the difference between DNA and protein products. DNA is like the blueprint, and proteins are the actual creations, all the bits and pieces that make organisms work. Cell walls, mitochondria, etc. The second thing to keep in mind is that genes, which are the regions of the DNA that code for these proteins, only make up 2 percent of your DNA. For the 60% statistics' source, scientists compared the genes of a banana to human genes. About 60 percent of our genes have a recognizable counterpart in the banana genome. Not 60% of DNA, but 60% of gene products. This still may sound shocking, but it really isn't. These genes encode the basic functions that keep plants and animals alive, like consuming oxygen. You share 50 percent of your DNA with each of your parents. But with bananas, we share about 50 percent of our genes, which turns out to be only about 1% of our DNA. And we pretty much share at least 1% of our DNA with all living things. [source]( URL_0 )" ]
[ 6 ]
[ [ "https://science.howstuffworks.com/life/genetic/people-bananas-share-dna.htm" ], [] ]
[ "url" ]
[ "url" ]
64ekbv
Pleading not guilty and then being found guilty.
If someone's pleads not guilty to a crime (trial-worthy) and then through the court proceedings they're found guilty (no plea deal), shouldn't they also then be convicted of obstruction of justice or Perjury, or some other serious offense....? Assuredly this can then be overturned if the ruling is repealed... Let's assume this is a clear-cut, non-circumstantial case. e.g. They're caught on tape + DNA evidence + credible eye witness.
Other
explainlikeimfive
[ "dg1iei2", "dg1ijgj" ]
[ "A guilty plea is not under oath and is not testimony. It's also not a factual claim; in the context of a trial, it's really a statement that you're going to require the government to meet its obligation to convict you. So it's not perjury, which is false testimony." ]
[ 38 ]
[ [], [] ]
[ "url" ]
[ "url" ]
7escds
How do Car Keys hold their charge? Do they get charged by the car?
Technology
explainlikeimfive
[ "dq72k1w", "dq72lps", "dq72lih", "dq73lew" ]
[ "The battery holds charge like any other battery, it just lasts a long time because it uses so little electricity. You can open your key fob and change the battery if it runs out." ]
[ 6 ]
[ [], [], [], [] ]
[ "url" ]
[ "url" ]
ax4y40
What the hell does 8/7c mean in America? Like, when a tv show is airing at 8/7c, what does that mean?
Other
explainlikeimfive
[ "ehr8lf3", "ehr8mpl" ]
[ "8pm eastern time, also known as 7pm central time zone (and 6pm mountain time zone, 5pm Pacific if those are broadcasting at the same time)" ]
[ 30 ]
[ [], [] ]
[ "url" ]
[ "url" ]
5p5grq
why Vinyl is so popular in music media
Is the quality better than digital? Or is it a "gee this is old and kool" thing?
Culture
explainlikeimfive
[ "dcokvyf", "dcoixgc" ]
[ "I like it because: * I own the media. * It forces me to get up and actually interact e.g. changing sides, putting it back, etc. I like that for some reason. * It's a commitment more or less so I feel like maybe I pay more attention to the music rather than having something on in the background. * While I can buy records online, stopping in record stores is fun. * There are records of albums that are readily available and those that aren't. Tracking down the rare ones, making trades, etc. is fun. I read a comic somewhere where this guy was talking about his record player and collection to another guy with the caption \"I mostly got into vinyl for the cost and inconvenience.\" I totally understand that point of view, but it's still a fun hobby." ]
[ 5 ]
[ [], [] ]
[ "url" ]
[ "url" ]
6fuks3
Is there something inherently rewardy about dopamine or is it arbitrarily set as a happiness chemical similar to how words in a language are arbitrary?
Why dopamine? Could it really have been any other chemical if things had worked out differently (like how the word 'happy' could really have been any other combination of sounds/symbols if things had worked out differently) or is there something that makes dopamine the correct chemical for happiness? If there is some inherent benefit of dopamine, why only reward it in bursts?
Biology
explainlikeimfive
[ "dilawft", "dil2fcz", "dilc5f6", "dilhe3r" ]
[ "That system came about via evolution. Put simply it's a system of a chemical released by certain brain cells that bonds to receptors on other cells altering their activity. Basically a signal and a receiver. A vast number of other chemical-receptor systems could accomplish the same task (we have a lot of similar systems with different functions already). The receptor and signaling molecule must match but otherwise there's not usually anything special about either one. It's likely entirely due to random chance that evolution settled on dopamine for that role." ]
[ 4 ]
[ [], [], [], [] ]
[ "url" ]
[ "url" ]
70hu2k
What is the difference between an irrational number and a transcendental number?
Mathematics
explainlikeimfive
[ "dn388kr", "dn3hhov" ]
[ "> All transcendental numbers are irrational. not all irrational numbers are transcendental. > Trancendental numbers cannot be written as roots of polynomials Eli6: Irrational numbers are a class of numbers that are (among other things) defined by the fact that you cannot represent them as a ratio of integers. Transcendental numbers are a class of numbers that are defined by the fact they are not algebraic. algebraic numbers are numbers that can be written as a root of a polynomial with rational coefficients: So any number that can be represented as the answer (x) to an equation of the form a + bx + cx^2 + dx^3 + ex^4 + fx^5 ... + ðx^n = 0 Where the coefficients a,b,c,d,e....ð are all rational numbers. So, root 2 is irrational, but it is algebraic because it is the answer to the equation x^2 = 2 and thus is not transcendental. Similarly the more or less random number ~ 1.27367020598447 is also not trancendental, because it is a valid solution to the equation x^4 + 5x - 9 ( ~1.273...^4 + 5(~1.2736..) - 9= 0 ) Trancendental numbers like pi can't be written as solutions to equations of this form. They will always need at least one irrational number as a coefficient to be written like this." ]
[ 9 ]
[ [], [] ]
[ "url" ]
[ "url" ]
cy42jq
The relation between half-life and radioactivity
Uranium has a half-life of 4.5 billion years and it's very radioactive, but Bismuth has a half-life of 15 quintillion years and is very weak radioactively, is half-life not related to radioactivity or is there something i'm not taking into consideration?
Chemistry
explainlikeimfive
[ "eypk6po" ]
[ "Half life is how long it takes for an individual atom to have a 50/50 chance of decaying. That means that a chunk of stuff with a shorter half life will have more radiation, since it is decaying quicker." ]
[ 5 ]
[ [] ]
[ "url" ]
[ "url" ]
e88vvo
How does the Meselson-Stahl experiment prove that DNA replication isn't dispersive?
To clarify, english isn't my first language; the title might sound like I assume that it should be dispersive, which would make this a question about an opinion and therefore against the rules, but I know and understand that it's semi conservative, I just don't understand how its proven. thanks in advance for replies :)
Biology
explainlikeimfive
[ "faa6esj" ]
[ "I'm surprised you didn't get any replies yet. Okay well I'll explain the experiment. You have two DNA strands. When the cell replicates, you could either end up with the strands separating and acting as template for the new strands, where you have two sets of strands, each containing an original parental one. This is called semi conservative, the correct model. Or, you have the double stranded DNA just photocopies itself as is, and you end with two sets of strands, one is the original pair and one is a totally new pair. That's the conservative model. Or you could have the double stranded DNA just chop itself up in pieces and the pieces are then duplicated. Then these pieces, old and new, are randomly dispersed to each pair of DNA strands. You end up with a cocktail of DNA strands containing segments from parent and new. This is the dispersive model. Now to know which is true, Meselson and Stahl did this beautiful experiment. They got ecoli and incubated them with heavy nitrogen, it contains an extra neutron. Functionally this is the same as normal nitrogen, but you can tell them apart when you centrifuge on a density gradient. So anyway, when the ecoli were incubated with N15 for several generations, virtually all DNA in these bacteria was built with N15. Then they got these ecoli and let them divide once in N14 media (20 min), then again (20 min) and so on. They isolated the DNA, and centrifuged it on the gradient to see what you got. Now let's look at how the results would look like if each model was true: assume a single N14 Strand is like 100 AU (arbitrary mass or density or whatever units) and N15 is 200 AU. Semi conservative: the end result should be that all the progeny of the bacteria have DNA whose half is N14 and other half is N15. So on the gradient you should get only one band, and its density should be 300 AU. As the more and more bacteria divide, you should get a second band that keeps getting more intense, one at 100 AU. You have to draw this to understand. Conservative: here you should get two bands for the first cycle, equal bands, one at 200+200 AU (400) and one at 100+100 (200 AU). Next cycles you'll just keep getting a more and more intense 200 AU band. Dispersive: here you should get theoretically one band in the first cycle, where half each Strand or so is N15 and the other N14. So should be 300 AU. And as you go to higher cycles, you should be approaching the pure N14 Band gradually, which is at 200 AU. So you'll have many intermediate bands along the way. If you draw this it'll get very clear. Anyway, they did this and found the results predicted by the semi conservative." ]
[ 6 ]
[ [] ]
[ "url" ]
[ "url" ]
mdsrjl
Why is it hard to breathe when it’s windy?
Biology
explainlikeimfive
[ "gsb5kc2" ]
[ "We have a reflex to not breathe in, when what feels like water hits our face. A strong, colder wind can apply the kind of pressure to your face to make your brain think that you're underwater." ]
[ 5 ]
[ [] ]
[ "url" ]
[ "url" ]
ldobcq
I’m not someone who thinks the moon landing was fake, but why haven’t we gone back yet?
Other
explainlikeimfive
[ "gm6yojy", "gm709fh", "gm6yve4", "gm6z2sh" ]
[ "Going to the moon was a race between the USA and the USSR. When the USA made it to the moon, they won the race. Without the race, there is no longer a good enough reason to drop hundreds of millions of dollars to put people on a rock that they have already been to. The space agencies would rather spend the money, time, and resources on new space projects." ]
[ 8 ]
[ [], [], [], [] ]
[ "url" ]
[ "url" ]
du2yda
antioxidants in foods
Biology
explainlikeimfive
[ "f71d35k", "f72f5l5" ]
[ "In the body, a certain type of chemical can form called a *free radical.* This refers to any atom, molecule, or ion with an unpaired electron in its outer shell. These unpaired electrons can produce oxidizing damage due to their interactions with other parts of your body. *Anti-oxidants* work to sequester and convert free radicals back to non-radical forms, and thus help prevent this damage." ]
[ 4 ]
[ [], [] ]
[ "url" ]
[ "url" ]
6y3i14
How do humans retain the skill of riding a bicycle even with long periods of unuse?
Biology
explainlikeimfive
[ "dmkh77i", "dmky6zo" ]
[ "Bike riding is 95% confidence. You get on a bike, it's unstable it tips over, no way you're going to pick your feet up an barrel forward on that precarious contraption. After much cajoling from your parents or whoever, you learn that once the wheels start turning, the angular momentum keeps you stable. The faster you go, the more the bike wants to stay up. It's not a skill you learn, it's a secret you discover. The other 5% is steering, and that's just too easy to unlearn. (I'm of course talking about the skill of riding a bike at all, not suggesting that becoming Lance Armstrong is 95% confidence)" ]
[ 13 ]
[ [], [] ]
[ "url" ]
[ "url" ]
968a62
how do emergency vehicles turn traffic lights red so they can get through?
I work outside by a hospital and a few times a day I see ambulances and firetrucks go through the intersection by my work and they always turn all the traffic lights to red so they can get through faster. How do they do that?
Technology
explainlikeimfive
[ "e3yh6e6", "e3ykenp", "e3yuyh5", "e3ygiqy" ]
[ "It’s called an OptiCon. Fire, ems and police use them, but not every emergency vehicle has them. The vehicle has to have a special light in its lightbar in order to activate the mechanism over the light to change it for their benefit. Source: am firefighter/EMT. That being said, I don’t know the absolute specifics behind it because all I need to know is if my truck has it lmao" ]
[ 12 ]
[ [], [], [], [] ]
[ "url" ]
[ "url" ]
9h47rj
how do deep sea creatures survive under the enormous pressure?
Biology
explainlikeimfive
[ "e68ycn5", "e691yy5", "e69337f", "e690rn4", "e68ydkt", "e695rei", "e694anw", "e6920lr", "e6944un", "e693j8u", "e696vua" ]
[ "They're acclimated. The pressure inside their bodies is the same as the pressure outside their bodies. Since there's no pressure difference, they can breathe and function normally down there, although the ~~increased water resistance from the high pressure~~ *difference in the water's 'slipperiness' (called \"viscosity\") at that depth due to pressure and temperature* (edited, with props to /u/agate_ for the correction) from the high pressure (plus lack of high-calorie food) likely makes most of them generally move slower than surface creatures. This is why deep-sea species are almost assuredly dead when you capture them and bring them to the surface unless you take extraordinary precautions. As they rise through the water, the pressure inside their bodies becomes tremendously higher than the pressure outside their bodies, and their internal organs rupture like an overfilled balloon as they're dragged up." ]
[ 2129 ]
[ [], [], [], [], [], [], [], [], [], [], [] ]
[ "url" ]
[ "url" ]
g8fdje
Why do flu shots come out every year and bypass clinical trials?
Biology
explainlikeimfive
[ "fon4orr", "fon4pzo" ]
[ "Because flu vaccines are not brand new vaccines, they are minor tweaks to the previous one to adapt it to the new strain of flu. When Tylenol changes the colouring of their pills, they don't go through clinical trial either, it's the same logic. Plus, if you went through 3 month of trials every year for the flu shot, it would be past flu season by the time ithits the market..." ]
[ 7 ]
[ [], [] ]
[ "url" ]
[ "url" ]
8vau50
When you get a shot, like the flu shot or b12, why do you have to get it in certain areas like the arm?
Biology
explainlikeimfive
[ "e1lvdsl", "e1lx1fk", "e1lws3k" ]
[ "It depends on what kind of shot you get, but often if you get a shot in the arm it is because it is easiest and least irritating for the patient" ]
[ 9 ]
[ [], [], [] ]
[ "url" ]
[ "url" ]
5m0sah
Why do the web addresses for subreddits need an /r/ before them?
Technology
explainlikeimfive
[ "dbzvd05" ]
[ "They don't \"need to\" necessarily, but that's just how Reddit has their site mapping set up" ]
[ 3 ]
[ [] ]
[ "url" ]
[ "url" ]
jc71wp
How can the universe be infinite and expanding at the same time?
Physics
explainlikeimfive
[ "g8zkzyx", "g8znhtb", "g8zmrf8", "g8zkuh1" ]
[ "Expansion means that everything in the universe is moving away from everything else. We do not need a border for this to work. Consider the number line of whole numbers. This number line is infinite in the positive and negative direction. Yet, we could re-arrange it in a way that the distance between any two neighboring whole numbers increases from one unit to two units. That is we re-arrange the number line from this ... -5\\_-4\\_-3\\_-2\\_-1_0_1_2_3_4_5..... to this ...-5\\_\\_-4\\_\\_-3\\_\\_-2\\_\\_-1\\_\\_0\\_\\_1\\_\\_2\\_\\_3\\_\\_4\\_\\_5.... This re-arrangement is an expansion of the number line, since each object (each number) has been moving away from all other numbers. Since the number line is infinite in both directions, however, we have seen that infinite objects can expand." ]
[ 30 ]
[ [], [], [], [] ]
[ "url" ]
[ "url" ]
6vdx60
Why do giant characters in movies and tv shows seem to move in slow motion rather than at normal speed?
Repost
explainlikeimfive
[ "dlzi9ns" ]
[ "Something that is far away from you looks like it's moving slowly, even when it isn't. Think of watching a plane move across they sky; it's going 500mph, but seems to crawl across your view. A giant who's far enough away to fit on the screen will be moving fast, by virtue of being huge, but will still seem to move more slowly because they're further away. Also, it's just a visual trick/cue used to add perceived mass and size to something when you aren't actually there to see it in 3D with proper perspective to the things around it." ]
[ 10 ]
[ [] ]
[ "url" ]
[ "url" ]
9176bo
How did the name "Jesus Christ" come to be equated to expressing shock and surprise?
Culture
explainlikeimfive
[ "e2vxs0i", "e2vwxub" ]
[ "Invoking the name of Jesus, God, or other deities is a common reaction to shock and surprise. In its original religious context you are literally calling on them to bless you and protect you in that moment, or you are calling on them to condemn or curse someone or something in that moment. As the habits became ingrained into common practice it took on the secular meaning of exclaiming shock, but many religious people still hold to the original uses and that is why you get admonitions of \"do not use the Lords name in vain\" when you use it simply to show shock." ]
[ 24 ]
[ [], [] ]
[ "url" ]
[ "url" ]
9ik0zl
Why can't we think properly when we get angry?
Biology
explainlikeimfive
[ "e6k6thb", "e6k7ags" ]
[ "Your adrenal glands are producing adrenaline, which in turn stimulates fight-or-flight response. It is so, because in the cavemen days when somebody was in danger, people who were quick to act rather than think things through survived long enough to produce offspring and pass their genes and by extend their behaviour." ]
[ 16 ]
[ [], [] ]
[ "url" ]
[ "url" ]
6fmeez
Why do we have that little groove between our noses and lips?
Biology
explainlikeimfive
[ "dij96s3" ]
[ "It is called the philtrum and is caused by the nasomedial and maxillary processes meeting during development. If they don't meet a cleft lip can occur. As for its function in some organisms this channel can carry dissolved oderants from the nose pad to a sensing organ within the mouth. In short when something like a dog sticks its nose into something whatever sticks onto the nose can flow down the groove into the mouth for tasting/smelling. For humans it is just a leftover structure that doesn't really have much use." ]
[ 7 ]
[ [] ]
[ "url" ]
[ "url" ]
6irtey
is there anything to prevent unknowingly receiving a relative's sperm donation?
A similar question has already been asked in relation to offspring of sperm donors engaging in accidental incest, but my question specifically relates to preventing relatives from receiving relatives' sperm donations. I'm aware that in many places sperm can be, and often is, donated anonymously. How do industry employees know if they are giving an anonymous donor's sperm to someone who is biologically related to the donor??
Other
explainlikeimfive
[ "dj8pa05", "dj8vftb", "dj96tko", "dj8sdp5", "dj8pfp3" ]
[ "There really aren't any safeguards. Safeguards against 'what-if's tend to only be put into place after some kind of tragedy, so I wouldn't expect to see anything legislated until someone's kid comes out badly inbred. One would suppose that over time this will become a larger and larger problem; as sperm donation is objectively more evolutionary fit behaviour, so a small number of donors with the desire to donate will produce legions of new donors. It's likely that we'll start doing whole genome scans of everyone before it becomes a problem though." ]
[ 36 ]
[ [], [], [], [], [] ]
[ "url" ]
[ "url" ]
ihmyky
What first needs to happen to a planet, say the moon, for life to start?
Other
explainlikeimfive
[ "g313qgc", "g317she" ]
[ "We don't know. We have one sample, ever. Makes for difficult science. We hypothesize that chemical diversity, pressure, water, and a certain range of temperatures are (if not necessary) very helpful for the formation of life. However, what exactly can cause life to form is difficult to determine." ]
[ 7 ]
[ [], [] ]
[ "url" ]
[ "url" ]
8q84vt
Why does your saliva start to run when/before you have to throw up?
Biology
explainlikeimfive
[ "e0h6u26", "e0h6nxn" ]
[ "Your saliva glands go into overdrive when you're about to spew to not only protect you from high velocity carrot chunks but also to help you to abandon optimism and get your behind to a bathroom stat." ]
[ 10 ]
[ [], [] ]
[ "url" ]
[ "url" ]
mcz6ac
Why do we instinctually shake our hands when we hurt them, like when we punch something?
Biology
explainlikeimfive
[ "gs6sulp", "gs6xaj2" ]
[ "Okay. So when you hurt your hand, nerves send signals to your brain that somethings wrong. We perceive that as pain. When we flail our hands, your nerves feel more stimuli, drawing the affects of pain away from your brain. To dumb it down even more. Shaking your hands is essentially **masking** the pain with more nerves sending signals." ]
[ 34 ]
[ [], [] ]
[ "url" ]
[ "url" ]
5tl03e
Why does society enjoy watching violence?
From gladiatorial shows in the Colosseum to modern day film it seems as a society we enjoy watching violence being inflicted upon others. Why is that?
Other
explainlikeimfive
[ "ddnac6d" ]
[ "it's actually kinda basic, if you watch fight club you can see it through the messages the movie sends. It's just how humans work. It's a mix of morbid curiosity and interest to participate, humans somehow are naturally predisposed to violence, it could be a link to our primal years, where violence usually could solve many problems. so in summary, humans are just violent beings and many people for some reason or another are subconcuoisly drawn to violence." ]
[ 6 ]
[ [] ]
[ "url" ]
[ "url" ]
8o93dj
How to explain the action of catalytic promoters and poisons?
Chemistry
explainlikeimfive
[ "e01sxsz" ]
[ "A promoter is something that helps the main catalytic ingredient to do its job, for example some metal oxides that help iron to break down the N2 molecule in 2 single N atom in the catalyst used in making ammonia. A poison is something that change the catalyst proprieties, eg forming stable compounds that no longer have catalytic activity" ]
[ 3 ]
[ [] ]
[ "url" ]
[ "url" ]
fy1qb3
Is any of the stuff Mark Watney did in Martian actually doable? I figure the botany stuff is but anything else?
Other
explainlikeimfive
[ "fmxrovz", "fmxu3af" ]
[ "Actually, the science shown in *The Martian* is all very accurate. In fact, the least plausible element is the storm that starts the story; the martian atmosphere is too thin to produce winds with that much power. Everything else, though - at least insofar as the book is concerned - is pretty spot-on. In large part, it was because Andy Weir, the author, worked with NASA representatives as he wrote, making sure he was getting his science correct. The movie is also pretty realistic except for two items (in addition to the storm): 1. Martian gravity is about 1/3 that of Earth's. So everything you see falling, jumping, bouncing, etc. would behave very differently in reality. However, since editing the gravity of Namibia was, well, impossible, we need to just overlook that. 2. The Iron Man flight at the end was practically impossible. To be able to control that kind of thrust with any kind of accuracy at all would be improbable in the extreme. Everything else though? Incredibly accurate." ]
[ 12 ]
[ [], [] ]
[ "url" ]
[ "url" ]
6jupyz
Why has airline service gotten so much worse over the years when more and more people are paying to fly?
Other
explainlikeimfive
[ "djh4kwd" ]
[ "Airlines were deregulated in 1978. Before that, the government was heavily involved in setting the prices for tickets. For that reason, airlines couldn't lower their prices to compete with each other. Since the airlines charged basically the same prices, they competed on service and amenities to win customers. After deregulation, they started competing on price like those in other industries. They quickly found that they could attract more customers by offering a cheap flight than a comfortable flight." ]
[ 8 ]
[ [] ]
[ "url" ]
[ "url" ]
nb7qx5
why do we say “uhm” when we’re thinking? I’m multilingual and it seems to apply to most languages. What makes it so “universal”?
Other
explainlikeimfive
[ "gxxvisb", "gxxv5oh", "gxy4xf4", "gxy9tt3", "gxykcjs" ]
[ "Uhm and similar sounds are [filler words]( URL_0 ). Their main purpose is to signal that the speaker isn't done speaking. Often times we need a half second to think of what we want to say next. If we let that moment fill with silence, others may take that as a sign we are done talking and then start with their own thread. Filler words serve the purpose of signifying we have more to say. This is a universal problem. It is not surprising other languages have come up with their own filler words. Eliminating filler words from important speeches has the benefit of making the speaker sound more worth listening to. Someone who is used to being worth listening to wouldn't be worried about others interrupting their speech with their own. So we naturally give more weight to those who don't use filler words. In day to day conversations between friends though, filler words serve an important function." ]
[ 33 ]
[ [ "https://en.wikipedia.org/wiki/Filler_\\(linguistics\\)" ], [], [], [], [] ]
[ "url" ]
[ "url" ]
jmt3os
How is radioactivity induced in an originally non-radioactive object? Like Marie Curie's body.
Physics
explainlikeimfive
[ "gax6pyu", "gax6tue" ]
[ "Through [neutron activation]( URL_0 ). The ELI5 version is that a big 'ol neutron hustling around smacks the nucleus of an atom, and gets stuck. That makes the atom unstable, and causes it to start popping off little pieces of itself (radiation) until it can be stable again. In the example of Marie Curie though it isn't her body that's radioactive. It's all the radioactive stuff that's in her body. She did *a lot* of work around radioactive material without safety equipment like masks, gloves, and ventilation. That caused her to inhale or ingest a whole lot of nasty little radioactive particles." ]
[ 8 ]
[ [ "https://en.wikipedia.org/wiki/Neutron_activation" ], [] ]
[ "url" ]
[ "url" ]
6t1jaa
How do cartoonist sync up the voice actors with the drawings?
Technology
explainlikeimfive
[ "dlh99eo", "dlh60nr" ]
[ "I'm an animator! I can answer this! Most of the dialogue for a cartoon is recorded and sequenced before any drawing takes place. The visuals must reflect what the voice actors were trying to convey, so the drawings are done after any recording sessions to more accurately mirror the actors' choices. It is a long and tedious process of switching out mouths, going back a frame or two, replacing drawings, listening carefully for phonetics, etc. It takes a while, but it looks good in the end. There are instances where a voice actor may record a line or sound to match pre-existing visuals, but for the most part, the acting is done first." ]
[ 15 ]
[ [], [] ]
[ "url" ]
[ "url" ]
nyaukn
Can someone explain how the higher units of the US Army are organised?
What is a command? A field army is made of 2-3 corps, but the only active field army has just 1 division and some other stuff in it and a bunch of other confusing stuff like divisions not being part of corps contrary to what the official US Army site suggests. Why is it all so confusing?
Other
explainlikeimfive
[ "h1j6fzc", "h1j8a8g" ]
[ "There is organization as it could/should be, and there's organization as it is. In general, there are divisions, then corps, then field armies, then army groups, then theaters. In practical usage, those levels can be skipped if needed. If there is a single division deployed in Elbonia (far from any other US forces) as part of peace-keeping operations, you don't need those intermediate levels of organization; it can report directly to the Europe theater commander. There's no reason to have the divisional commander report to a corps commander who reports to a field army commander who reports to the army group commander who then reports to the theater commander. The \"could/should be\" organization is sort of the worst-case scenario: \"if you have a massive army fighting a complex war, it should be organized like this.\" Divisional commanders reporting to a corps commander makes sense if there are tons of divisions on the field; that way, the field army commander doesn't have to deal with 20 different divisional commanders giving him reports, only 5-7 corps commanders. It also makes command easier; the field army commander can order 1st Corps to take X region, and the details are up to them. They don't have to order 1st Division to secure Y City, 2nd Division to advance to the Z river and hold against a counterattack, 3rd Division to detach their artillery support for 1st Divisions attack, etc." ]
[ 6 ]
[ [], [] ]
[ "url" ]
[ "url" ]
9grq55
What’s the point of one video game company buying a smaller company and then dissolving said smaller companies?
Other
explainlikeimfive
[ "e66ecz0" ]
[ "Reducing potential competition, absorbing technology or resources, obtaining complimentary resources or market segments, expanding, increasing share value, lots of business reasons." ]
[ 7 ]
[ [] ]
[ "url" ]
[ "url" ]
j5rsi7
How does gravity (or a lack thereof) affect blood flow?
Also, what about increased gravity? What would happen if you got a cut in different types of gravity?
Biology
explainlikeimfive
[ "g7ty03c" ]
[ "The effect of gravity depends how alive you are, and the consequences of a cut depends on what kind of cut. The body maintains a blood pressure by pumping it around and constricting the walls of the arteries (send blood away from the heart). If you cut a big artery or a big enough vein (returns blood to the heart), you will bleed out about the same, in space or on the ground. If you die on earth, the blood pressure drops to zero. Your blood will run downhill over time like water and pool in the lowest lying areas of the body. This causes changes in skin colour (blotchiness, pallor). In space, likely that won’t happen. That said, no human has ever died in a zero gravity environment, so other unexpected things might happen that we don’t know about. That said, zero gravity does mess with circulation in the living. Fluids, including blood, tends to pool in the body’s tissues (edema), which causes some swelling. This is because veins don’t work quite as well in space, which also means there’s some increased risk of clotting in them too. For the most part it’s not been anything life-threatening, but it’s part of why astronauts exercise on the ISS. Increased gravity will cause humans to pass out quickly, fighter pilots experience this in training. Turning a plane fast puts a lot of extra “gravity” onto their body, and this can lead to a “grey out” where they lose vision, or a complete blackout. This is because the heart and the muscles in the arteries aren’t effecting at counteracting such extreme forces. When blood can’t reach the brain, it’s lights out. Also speaking of pilots, if they push the stick down instead of pull it up, they can get *negative* gravity. That is probably the most dangerous one, because it causes blood to rush into the vessels in the brain. Those vessels aren’t good at dealing with that at all, so there’s a good chance that one might burst (stroke) if the force is high enough. That can kill someone quite fast. It takes much less negative gravity to kill a human than positive gravity, so fighter pilots avoid it." ]
[ 4 ]
[ [] ]
[ "url" ]
[ "url" ]
5vs21e
Why is it so challenging for developed nations to completely eliminate poverty?
Economics
explainlikeimfive
[ "de4g9lk", "de4mzz0" ]
[ "Poverty is a moving target. As a country's standard of living increases, the standard for what is considered poverty also increases. Poverty is often defined relative to national averages, which means mathematically it can never be eliminated." ]
[ 6 ]
[ [], [] ]
[ "url" ]
[ "url" ]
8coc6b
why rubbing your head after banging it helps in reducing pain?
Biology
explainlikeimfive
[ "dxggv49" ]
[ "When you whack your head, your nerves are sending pain signals to your brain. Nerves can only send one signal at a time. By pressing/rubbing on your head, you override the pain signals and replace them with pressure signals. That's why as soon as you stop, the pain comes back." ]
[ 36 ]
[ [] ]
[ "url" ]
[ "url" ]
92khaa
How are we so sure we all see the same colors? like, the color of the sky is blue but how are we sure that the blue we see is the same?
Physics
explainlikeimfive
[ "e36dftj", "e36dmow", "e36ettj", "e36d9hl" ]
[ "We're not, and we don't. Take colorblind people for example, they don't see the same colours as those without the blindness. Moreover, in my personal experience people often have discussions whether a colour is for example blue or green, meaning that they either don't see it as the same colour or they have different concepts of the colours. Also, some people have an extra photoreceptor meaning that they see additional colours. In general, it doesn't matter whether you see the same colour - as a child you're taught the sky is blue and leaves are green, so whatever you perceive those colours as are now blue and green for you. These articles might help: URL_1 URL_0" ]
[ 21 ]
[ [ "https://wonderopolis.org/wonder/do-you-see-what-i-see", "http://www.bbc.com/future/story/20120209-do-we-all-see-the-same-colours" ], [], [ "http://www2.lbl.gov/images/MicroWorlds/EMSpec.gif" ], [] ]
[ "url" ]
[ "url" ]
df9xwu
- how does the Earth's core produce a magnetic field when iron loses its magnetic field when it reaches "Curie temperature"?
Physics
explainlikeimfive
[ "f31unr6", "f31uymo" ]
[ "The Earth is full of molten iron, which spins along with the rest of the planet. Molten iron is conductive of electricity, and the result is a massive electromagnet. Iron's magnetism is *not* the source of the Earth's magnetic field." ]
[ 38 ]
[ [], [] ]
[ "url" ]
[ "url" ]
jczowq
How does a RT-PCR test work?
How does an RT-PCR test work? Are samples dead or alive? What does lysing do?
Chemistry
explainlikeimfive
[ "g95bkv4" ]
[ "PCR: So RT-PCR is a variation of a method called PCR. PCR stands for Polymerase Chain Reaction. Polymerase Chain Reaction is method used in science and diagnostics because it allows us to make a lot of copies of a certain DNA sequence, that way we can easily work with it. The 'copying' itself is called 'amplification'. It usually requires the DNA you want amplified, a mix of 'DNA building blocks (dATP, dTTP, dCTP, dGTP)', an enzyme called Polymerase that 'builds' the other copies of the DNA and Primers. Primers work as a sign for the Polymerase that say where they should start 'building' the strand from those affirmationed building blocks, also calles nucleotides. This allows you to select what sequence you want amplified based on the primer you choose. PCR is done in a machine called the thermocycler and usually has 3 stages: 1. Denaturation By heating up the double stranded DNA to (usually) 95°C you seperate them into single strands (denature the DNA) which is important in the next step. 2. Hybridization/Annealing Mixture is rapidly cooled down to 55-65 °C so the primer can bind to the single stranded DNA. 3. Elongation Raising temperature to around 70 °C activates the polymerase (usually Taq polymerase is used for it's thermostability) and it starts synthesis of complementary strands to the single stranded DNA to make it double stranded DNA again. Thus by the end of the cycle we have 2x more of the sequence than at the beginning. And each PCR is usually 25-30x cycles so the amplification is exponential. RT-PCR is just a variation of this, when its you need to amplify mRNA instead of DNA and uses an enzyme called Reverse Transcriptase to that effect. For instance the notorious SARS-CoV-2 has a genome in the form of an mRNA (+ssRNA to be accurate) so it is amplified like this. LYSING: And lysing means basically 'breaking apart' the cell to release the DNA within so it can be accessed in the reaction. Usually done with a mix of chemicals called 'lysing buffer'. THIS ALWAYS KILLS THE SAMPLE Sorry it's so chaotic, I've tried explaining it simplest I could but there is some pretty complicated and awesome science behind this wonderful tool but I hope I atleast shed some light on it." ]
[ 3 ]
[ [] ]
[ "url" ]
[ "url" ]
b8z89k
How do we know what the exterior of dinosaurs actually looked like just based on their bones?
Biology
explainlikeimfive
[ "ek10hmh", "ek164sh" ]
[ "In a lot of cases we don't. & #x200B; In some cases we can the imprint of feathers or other surface features imbedded in mud that has turned to stone." ]
[ 25 ]
[ [], [] ]
[ "url" ]
[ "url" ]
87vbyc
Why is every first episode of a show titled the "pilot" episode?
Other
explainlikeimfive
[ "dwft6xs", "dwftgqn", "dwftfem" ]
[ "It's a Hollywood tradition. You label it \"Pilot\" so that people in the industry know that it's the first episode being made as a test run to see if the show is popular enough to convince the network to spend the full amount of money to make it a full series." ]
[ 7 ]
[ [], [], [] ]
[ "url" ]
[ "url" ]
7agpix
Why do lightbulbs go out, but not the lights that illuminate screens on TVs and phones?
Is it even possible for them to go out?
Technology
explainlikeimfive
[ "dp9tkyo", "dpa0gud", "dp9uqdi" ]
[ "it is, DLP tvs for example used a honest bulb (though very bright and powerful), and it had a life of a few years. LCD screens use edge lighting, most are LEDs these days (all cell phones), but they used to use compact florescent lights (rarely still do). both have absurdly long lifespans, longer than the devices they are in. but its possible for the backlight to fail. the newest phones (and some TVs) are OLED, which means the screen itself are itsy bitsy LEDs that generate the light themselves. again, super long life." ]
[ 17 ]
[ [], [ "https://en.wikipedia.org/wiki/Phoebus_cartel" ], [] ]
[ "url" ]
[ "url" ]
ihyoco
Why do you sometimes taste blood when you over-exert yourself during exercise
Biology
explainlikeimfive
[ "g33cxs1" ]
[ "The small sacs called alveoli in your lungs is where blood exchanges CO2 and oxygen. The blood is brought to the alveoli through small capillaries sometimes only 1 blood cell wide. These capillaries are incredibly thin to allow for the CO2/oxygen exchange. When you exercise your heart rate and blood pressure can increase quite a bit. Especially with intense activity. This increase in pressure can sometimes cause these capillaries to burst and blood will leak into the alveoli. The more/faster you exhale the more blood you’ll taste. The blood doesn’t actually get into your mouth. If you have blood in your mouth while exercising and it’s not from an open wound you’ve got bigger problems." ]
[ 62 ]
[ [] ]
[ "url" ]
[ "url" ]
6wxpxo
Considering air friction, why do fans make air feel cooler and not warmer?
Physics
explainlikeimfive
[ "dmbjgvy", "dmbkmoj", "dmbjzoj" ]
[ "The effect of friction on the air is negligible. Fans don't cool the air overall, but they make you *feel* cooler by moving the air around. You heat the air immediately above your skin to well above room temperature, and a fan blows cooler air in to replace that." ]
[ 23 ]
[ [], [ "https://en.wikipedia.org/wiki/Convective_heat_transfer" ], [ "https://en.wikipedia.org/wiki/Perspiration#Mechanism" ] ]
[ "url" ]
[ "url" ]
5ybraz
Why do storage devices have capacities that are multiples of 8?
Strictly speaking about gigabytes (8GB, 16GB, 32GB etc.)
Technology
explainlikeimfive
[ "deot0ck", "deosl4x", "deoufcb" ]
[ "storage is a collection of 1's and 0's (bits) and 8 bits form a byte. all the information about your files, programs and anything else is stored in this binary form. lets just call this the data. however just storing the data isn't enough. you have to be able to manage all this data, and how to find it all. that way when you open a file, the computer knows where to go to find all the data that comes together to form the file. this is done by giving each location on the storage device an address. and since there are SO many addresses, we actually need a way to label them all. which we do - in binary. and because of this, a storage device has a certain number of locations we are able to reference before we run out. and without getting technical about binary (with 8 bits you can address 2^8, or 256 locations), multiples of 8 means we are using every single available location to store data. so if we had a 16GB USB and wanted to make it bigger, to expand it to 20GB would be silly. since we are already making more locations available to reference, we might as well use every single location and expand it to 32GB. *thougt id add this in in case you do want to get technical: so like i said, 8 bits mean you can address 256 locations. if we add one more bit, we get 2^9 different locations available to us, or 512. this continues... 1024, 2048, 4096..... so you can see that with the addition of each bit we get a twice as many more locations to store the data. this is why you often see 512mb, 1GB, 2Gb, 4Gb, 8Gb etc... sizes for storage!" ]
[ 45 ]
[ [], [], [] ]
[ "url" ]
[ "url" ]
nfg4al
A whole orange will float on water but a peeled orange will sink. Why?
Physics
explainlikeimfive
[ "gylayzt" ]
[ "The air pockets and oil content in the orange peel keep the entire orange afloat. When you remove the peel, you remove the buoyant part of the entire orange . The peeled orange will sink as a result." ]
[ 6 ]
[ [] ]
[ "url" ]
[ "url" ]
9kmtu1
What is the meaning of our existence in the context of the physical universe?
Culture
explainlikeimfive
[ "e709e40" ]
[ "We are the apex predator on the third planet from a minor star. Meaning comes from how we treat each other and care for our planet." ]
[ 3 ]
[ [] ]
[ "url" ]
[ "url" ]
6ack8l
What is IGMP snooping?
I'm not that technically inept, but this stumps me. Is it a good thing or a bad thing? How and will it help me in life as a casual gamer. I saw it in my router settings and it got me curious.
Technology
explainlikeimfive
[ "dhdfcnu" ]
[ "When a switch doesn't know what to do with a packet, it sends it to everyone on the switch. A multicast only sends it to the ports that needs it. IGMP snooping allows the switch to determine who is part of the multicast group, and only send it to those people. Since all your traffic is going out one port on your router, it will not help you as a gamer." ]
[ 3 ]
[ [] ]
[ "url" ]
[ "url" ]
bge6mc
Why do rockets use low specific impulse - high thrust engines to reach orbits? Why can't High specific impulse and low thrust engines be used for the same purpose in a bit longer time?
I believe it could lead to fuel savings as High specific impulse means better fuel efficiency. Please correct me if I am wrong.
Physics
explainlikeimfive
[ "elk6urq", "elk7exf", "elk6pxg" ]
[ "> Please correct me if I am wrong. You are wrong. Rockets have to have a minimum thrust-to-weight ratio above 1 on the launch pad to go anywhere. That means if you have a 500,000kg rocket, you need at least 500,001 kilograms-force of thrust (although realistically you need more than that). A high specific impulse engine with thrust lower than that is taking you exactly nowhere, and there are no rocket engines that are both high IsP and thrust. You pretty much always have sacrifice one for the other, and you need thrust to get off the pad and into orbit. Once in orbit, you can use your high IsP, low thrust ion engines all you want, but they'll never get you off the launch pad." ]
[ 8 ]
[ [], [ "https://en.wikipedia.org/wiki/Electron_(rocket\\)", "https://en.wikipedia.org/wiki/Sea_Dragon_(rocket\\)" ], [] ]
[ "url" ]
[ "url" ]
nrz1fr
What does an MRI of the head make images of exactly, and what is it used to look at/diagnose?
Is there sometimes dye used in an MRI? What is this test used to diagnose/see versus for example a PET scan? TIA.
Technology
explainlikeimfive
[ "h0ji0yh" ]
[ "MRI scans are physically mapping the concentration of hydrogen, what this means for the human body is mostly measuring water and fat. They produce a structural image for example in the brain you can see all of the grey and white matter (and they appear different which is useful diagnostically). They’re using for diagnosing pretty much anything which causes a structural change in the brain like Alzheimer’s. MRI does occasionally use contrast agents but it’s rare as most MRI imaging doesn’t require it. A PET scan on the other hand measures the distribution of the tracer you inject, eg some sugar analog with a radioactive isotope. This lets you map metabolic processes, seeing where that tracer gets concentrated in the body. For example cancer cells use a tonne of sugar because they are growing so much, so if you image them with a PET scan then they can be easily identified. My experience in this is from studying physics involving medical imaging so someone with a medical background may be able to elaborate on exactly what they can be used for." ]
[ 6 ]
[ [] ]
[ "url" ]
[ "url" ]
m7jr2l
why does it matter if air is in the bloodstream?
I know that it can like cause you to die, but I don’t understand why, your blood has oxygen in it already. It always seems like they waste some when they’re about to inject (insert drug here)
Biology
explainlikeimfive
[ "grbmnvg", "grbmzjr" ]
[ "Oxygen and air bubbles are not the same thing. Think of it like a car engine. If the gas is flowing through the engine properly then the engine works fine, but if there's an air bubble in the gas line, then it causes the engine to \"miss\" and sputter. When the heart \"misses and sputters\" - that's a heart attack" ]
[ 16 ]
[ [], [] ]
[ "url" ]
[ "url" ]
cdw2ju
If we've discovered recently that modern humans are actually a mix of Homo Sapiens Neanderthalensis and Homo Sapiens Sapiens DNA, why haven't we created a new classification for ourselves?
We are genetically different from pure Homo Sapiens Sapiens that lived tens of thousands of years ago that had no Neanderthal DNA. So shouldn't we create a new classification?
Biology
explainlikeimfive
[ "etwoc7n", "etwy703", "etx1m8l", "etx5ad6", "etx4wzx", "etxk79j", "etxd40m", "etxw75s", "etye5yl", "ety51vj", "etyzmun", "etxtxrn" ]
[ "Two subspecies that don't fully diverge into new species generally won't get a separate name if they then create a hybrid. Look to man's best friend: all dogs are *Canis Lupus Familiaris*, and a hybrid with the original *Canis Lupus* (a wolf) doesn't get a new third designation, it's either mostly wolf or mostly dog and is treated as such. All modern humans are mostly *Sapiens Sapiens* by a massive margin, so they retain that name even though some have a low level of Neanderthal hybridization. More generally, subspecies designation is sloppy work since the line between subspecies is typically very blurry. Unlike bespoke species that typically can't produce fertile hybrids, subspecies usually can and sometimes this is a significant percentage of the population." ]
[ 2859 ]
[ [], [ "https://en.wikipedia.org/wiki/Denisovan" ], [], [], [], [], [], [], [], [], [], [] ]
[ "url" ]
[ "url" ]
cvc4j1
why are the 4 inner planets in the solar system are so much smaller than the 4 outer planets?
Sorry Pluto
Physics
explainlikeimfive
[ "ey39gvh", "ey384tl", "ey3oe6u", "ey38s84" ]
[ "Basically it was a combination of two things. In the early years of our solar system you could think of it as a giant cloud of hot dust and gas spinning very fast. As the solar system spun, lighter elements such as the gasses were pushed outwards to the edge of the solar system and heavier elements like metals were not pushed as far. Think of how when you spin a ball on a string and if you let go it will fly away. Same concept. In addition to this the sun helped push these elements as well throguh what's called solar wind. This is basically the light from the sun impacting the elements and pushing them. This act the same way, pushing lighter elements more than heavier elements. After the universe was separated like this, dust and gas started to coalesce into larger and larger bodies until we got the planet we know today with mostly gas in the outer region and mostly rocks in the inner region." ]
[ 86 ]
[ [], [], [ "https://en.wikipedia.org/wiki/Planetesimal", "https://en.wikipedia.org/wiki/Protoplanetary_disk", "https://en.wikipedia.org/wiki/Frost_line_(astrophysics)" ], [] ]
[ "url" ]
[ "url" ]
n1pg0j
Why do bees sting you even if it means their death? Don't they have a sense of survival?
Biology
explainlikeimfive
[ "gweig59", "gwehh5o", "gwehczk", "gwehk3a", "gwew7e1" ]
[ "**TL;DR:** *Bees don't \"think\" like we do. Most of their behaviours are automatic.* Think of a bee as about 99% robot that's been programmed to respond to what goes on around them in a certain way. That programming comes from millions of years of previous bees surviving based on what worked for them, collectively as a species. And in addition to the whole build-hives, collect-pollen, make-honey stuff, it has a basic instruction in it that says \"attempt to sting if the hive is in danger\". And the programming is so strong that it doesn't consider what happens to the bee itself, because it's easier to make more replacement bees than it is to not drive away the destructive intruder. If the target is small, the bee can actually pull its stinger out after injecting some poison. But if it's large, the barb in the stinger stays embedded and the bee's poison gland actually stays attached to it when the bee tries to leave, killing the bee. This sounds weird, so why? Even if the attacking bee is brushed away, the larger attacker gets more poison from the stinger which is left, which makes it feel worse. And that increases the odds that the attacker will stay the hell away from beehives in the future." ]
[ 39 ]
[ [], [], [], [], [] ]
[ "url" ]
[ "url" ]
5snyo1
What are charter schools?
Culture
explainlikeimfive
[ "ddgkr4q" ]
[ "Public schools are given money from city, county, state and federal governments on a per-kid and per-square-foot basis. Charter schools are private schools that meet a given standard to be considered equivalent to public schools. Parents can choose to enroll their children into these private charter schools, with a large portion of the tuition paid for by the per-kid rate that would have gone to their public school. Ideally, this means parents can choose the best school for their children without being restricted by arbitrary boundaries, while not \"wasting\" the per-kid tax payment their public school would have received. By the virtues of capitalism, only the best schools will succeed and children everywhere will receive the finest education! Unfortunately, this has yet to be proven true in a large scale. Studies of many charter schools have shown their students have objectively worse performance in almost every category. However, their marketing departments are world-class, and can drive sales which is what really matters because God Bless America." ]
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k6t10o
If we know the algorithm used for current day password hashing, how can we not just undo it to get the password?
I have read that SHA-2 is currently unbroken due to the amount of resources and time it would take to crack the hashing, but if we have the step by step algorithm, why can we not just do the steps backwards?
Technology
explainlikeimfive
[ "gemtcjw", "gemtgr6", "gemvcqr" ]
[ "Because it is a one way function. This means that it is - at least - practically infeasible to invert it. Optimally it would be a function that doesn't even have an inverse. There is one operation called \"modulo\" where one basically divides a number x by y and receives the remainder. So for example 7 mod 2 would be 1 because it is 3 with remainder 1. This means I can have an infinite amount of numbers mapping to the same output, but you can't reverse it. If I give you 7 mod 2 you can easily see it's 1. But if I said \"I received 1 when doing modulo 2\" you can't know it's 7, it could as well be 9, 11 or literally any odd number there is. So even though you know the \"algorithm\" to get from 7 to 1 by using modulo 2, you simply can't reverse the process. This is the main principle hashing functions use, thus you can't just invert them." ]
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