There is, it is called mutualism. Our intestines are lined with millions of bacteria, they help us break down our food and make it easier to digest. Oral flora can, for some people, prevent cavities or plaque buildup. There are many other bacterium and parasites that can benefit us. If you’re at the store, take a look at the “probiotics” section.
Monday, 29 February 2016
ELI5: When someone loses a hand/arm etc., and the wound is cauterised, what happens to the blood flow? Wouldn't the arteries leading to the wound clog up with blood, leading to extremely high blood pressure and a heart attack?
Our circulatory system is a lot like a big road system. Now imagine you’re taking a trip in a car. Along the way there’s a wreck that no one can pass. It slows cars down and there’s traffic buildup so you take a detour. You exit off the highway and try to find a different way to go. In very simple terms this is how circulation works in the body. Red blood cells behave a lot like people in cars - they hate traffic, and they always want to take the least congested route. In the body, what path these cells take is determined mostly by pressure, traveling from areas of highest pressure (left ventricle) all the way back to areas of lowest pressure (the right atrium). So what happens when there’s a kink in the system? To answer your question about cauterization, this is like a whole road being closed. Red blood cells build up behind the blockage, increasing crowding, which increases the pressure. Blood cells coming into the jam are more likely to be detoured into another vessel branch that has less pressure. Now our circulatory system is incredibly connected by branches that we call “collaterals.” This connectivity prevents the problem of “extremely high pressures” that you’re talking about because there are literally millions of release valves that keep the pressure manageable. They’re essentially branches in parallel, if you know something about circuits.
The amazing thing about collateral circulation is that if there is still high pressure, the body will make completely new vessels to reduce the pressure over time. It will even remodel existing blood vessels to handle more blood than they could originally. A great example of this is the rib notching phenomenon in patients with coarctation of the aorta. This is a disease where the aorta has a spot that looks like someone tied a rubber band around it. So instead of passing through this tight squeeze, blood takes a detour through vessels that go around your ribs. The vessels get bulkier from all the new blood they have to carry, eventually causing them to create “notches” in the rib where the vessel bulges against it.
There are some cases where the catastrophe you described can happen though, and this typically only occurs where there are no alternative branches for blood to escape. The best example I can think of is a saddle embolus, often happening from a clot in your leg veins that breaks off and travels all the way to your heart. Some background, there is only one route to get from the heart to the lungs - the single pulmonary trunk that branches off into the right and left pulmonary arteries. If a clot is large enough to get caught at this branch point it will “saddle” both arteries, cutting off blood supply to the lungs and left heart which kills you almost instantly.
So the main idea here is that collateral circulation is the key to keeping your blood flowing when there is a blockage. I mentioned two examples that show the role collaterals play. In coarctation of the aorta, the body may divert blood through pre-existing collaterals as an emergency pressure release, and remodel/make new ones as a long term fix. But in a saddle embolus there are no collaterals and there is no time to make new ones. The pressures build up to dangerous levels on the right side of the heart and fall to near zero on the left side. Eventually the heart stops pumping altogether and you die.
Saturday, 27 February 2016
ELI5: How come it takes years to make a 2 hour movie, but shows like Game of Thrones can release up to ten hours of movie-grade entertainment every year?
First, it doesn’t take years per se to make a movie. But there can be some delays - perhaps principal shooting only takes 2 months, but you have to wait 3 months for your lead actor to be available.
Shows like GoT get benefits over movies since the sets are all pre-built (past the 1st season) - actors have contracts stating they need to be available during a predictable time schedule if the show is renewed for the next season. GoT in particular also gets to benefit from the fact there are several plot lines that are independant - the Wall stuff, the Khalesi plot, the Westeros stuff, can all film in parallel. Not possible with a movie, where your lead actors can’t be in two places at once.
- multiple production teams for pre, post and shooting.
- multiple scriptwriters working on multiple episodes at once, television schedules being more demanding, less flexible to delays.
- a lot of the upfront preproduction and ‘selling’ of the show (aka the development hell) is out of the way before the pilot gets shot. Long running series don’t have to sell the production each season - just point to a rabid fanbase clamouring for more. Each movie has to churn through what could be years of this stuff. Production stuff.
- a movie could be 10 hours long, but noone would sit through it. But people will sit through 10 1 hr episodes no problem. So writing, timing and storytelling can be radically different.
Tuesday, 23 February 2016
ELI5:Why is the Kondratieff Cycle (families losing wealth within 3 generations) so accurate?
First generation earns it, second generation grows up being taught to appreciate it while being encouraged to take their own risks to try and create their own fortunes, and then the third generation grows up squandering both without being taught either lesson.
Monday, 22 February 2016
ELI5: Why do horses need to be put down when they break a leg while most other animals don't?
Horse bones are incredibly dense and fairly difficult to break, but when they do break they do not heal well, easily, or quickly and are very prone to infection. Most would die a slow painful death from infection, even with antibiotics and other medical care. Those that survive would most likely not have full use of the leg, and have a leg prone to break again.
Founder is another big reason why it’s hard to rehab a horse with a broken leg. Hooves are meant to withstand a certain amount of pressure, they’re not meant to distribute the 1/3 or the horses weight and the horse will founder. This causes the coffin bone to rotate causing the horse permanent lameness. Horses spend most of their life standing so a sling typically doesn’t work as it puts a lot of pressure on their sensitive digestive situation and horses don’t like to stand around for a long time.
And horses bear two thirds of their weight on their front legs, so if one is injured, there’s a lot more pressure on the remaining front leg. Back leg injuries (short of a break) are typically less serious.
But even under ideal conditions, the horse can still get laminitis (founder). The race horse Barbaro had a back leg injury and the prognosis was pretty good, but his owners spent over a million dollars on about 12 surgeries, and after that he still got laminitis and had to be put down.
Another aspect is anesthesia; horses don’t always come out of it well. Ruffian woke up out of anesthesia and immediately tried to run, breaking another leg, and then had to be put down.
ELI5: How do hackers find/gain 'backdoor' access to websites, databases etc.?
Gunna try doing this like ELI10. Back door access is just a way of saying “not-expected"access. Sometimes its still done through the front door, and sometimes its through a window.
Something like the front door would be if your Mom told you you could have one glass of coke, and you went and got the big glass flower vase, and poured 6 cokes into it. By following the rules in an unexpected way, you’ve tricked the machine. When mom asks you later how many glasses of coke you had, (of course with her trusty polygraph), you can truthfully answer, "One”. This might be like an SQL injection. Instead of answering 5+8=__ with “14”, you might answer with “14&OUTPUT_FINAL_ANSWER_LIST”. Since it has no spaces and starts with numbers, it might satisfy the rules.
Another way would be if your Mom said you could invite some friends over to play. After the 5th friend walks in, your Mom declares, “That’s it, not another kid walks through that door!” If you open a window and let Johnny climb in with his crayons, technically you didn’t break the rules (for the eventual polygraph) AND when you and your 5 friends go downstairs for homework, Johnny can color all over the walls without someone suspecting he’s there. This is as though you made new login names and used one of the names to give another person administrative, or Mommy, rights. Sometimes you need to make a new login screen, or just knock open a hole in the wall and cover it with a poster, but the idea is still to break the intention of the rules while following them to the letter.
What’s also important to remember is this goes very smoothly when someone lives in the house already, but becomes much harder when you’re trying to get into a stranger’s house. You might have to try to sell them cookies or magazines and then write down where the windows are. Or you might have to offer to clean their whole house for only $5, and then leave a window unlocked for your friend to come back later. Getting inside is a major step.
Sunday, 21 February 2016
ELI5: How can animals with fairly thin coats, such as deer, survive outside all winter in freezing temperatures - but humans would die pretty quickly if they wore nothing but a deer hide outside in the same freezing temperatures?
A thicker coat is only one piece of the puzzle - winter animals will:
- Put on extra fat
- They will save up extra food stores (e.g. squirrels, birds)
- They might expend less energy moving or foraging, instead directing that energy towards heat production
- They might even go into a nightly “hibernation” called torpor (e.g. chickadee birds)
- They might huddle together for warmth (e.g. penguins)
- They might find shelter in a tree or below ground (e.g. mice, birds)
- They might have a counter-current heat exchange blood flow (e.g. this explains why birds’ feet don’t fall off)
But the truth is a lot of animals suffer in the winter…having worked at a wildlife centre we see quite a number of winter related injuries. Frostbite, starvation, low body temperatures…even death.
Saturday, 20 February 2016
ELI5:If fruits are produced by plants for animals to eat and spread seeds around then why are lemons so sour?
A lemon is not a naturally occurring fruit, it’s actually bred from a sour orange and a citron, the sour orange itself being bred from a pomelo and mandarin. So it’s not the product of evolution, but selective breeding.
Saturday, 13 February 2016
ELI5: Why is today's announcement of the discovery of gravitational waves important, and what are the ramifications?
Since I actually tried to explain this to a pair of 5-year-olds today, I figure why not share :)
You know how when you throw a rock in a pool, there are ripples? And how if we throw bigger rocks in, they make bigger ripples?
Well, a long time ago, a really smart guy named Einstein said that stars and planets and stuff should make ripples in space, and he used some really cool math to explain why he thought that. Lots of people checked the math and agree that he was right.
But we’ve never been able to see those ripples before. Now some people built a really sensitive measuring thing that uses lasers to see them, and they just proved that their device works by seeing ripples from a really big splash. So now we know how to see them and we can get better at it, which will help us learn more about space. /cr
If Einstein is right (hint: HE IS), gravitational waves would travel outward from (for instance) two black holes circling each other just like the ripples in a pond. When they come to Earth and pass through the detectors, a signal can tell us not only that the gravitational wave has been found, but it can also tell us lots of information about the gravitational wave!
As you track what the gravitational waves look like over a (very) short amount of time, you can tell what kind of event caused them, like if it was two black holes colliding or a violent supernova… along with other details, like what the mass of these stars/black holes would have been!
This discovery has ushered in an awesome new era of astronomy. BEFORE we started detecting gravitational waves, looking out at the universe was like watching an orchestra without any sound! As our detectors start making regular observations of this stuff, it will be like turning on our ears to the symphony of the cosmos! /cr
Wednesday, 10 February 2016
ELI5: Why do we have to have a very varied diet in order to live a healthy lifestyle when all other animals tend to eat the same thing all the time and get all the nutrients they need?
You don’t actually HAVE to eat a varied and healthy diet. As a species, humans will do just fine if we all eat a very unhealthy diet, reproduce six times between 15 and 20, have three babies die, and drop dead ourselves at 27. This is a valid survival strategy for many species.
The problem crops up when you actually want to live till you’re 80. Then you’ll have to take much better care of yourself.
Car analogy: You don’t have to maintain your car, clean it or buy quality oil and gas if you plan on scrapping it when its three years old. But if you still want to drive it in 30 years, you have to take good care of it.
Monday, 8 February 2016
ELI5: Why humans are relatively hairless?
It is difficult to ELI5 because no one actually knows the answer for sure. Every answer presented as fact is really a hypothesis. More than that, they are just-so stories, because they are almost untestable and thus unfalsifiable. All of that being said, there are three major hypotheses, which are not mutually exclusive:
- The running man hypothesis: Walking on two-legs helped us throw spears and see far, and also let us separate our breathing from our stride. When most four-legged animals sprint, their bodies expand and contract such that their breathing is forced to follow their stride; we can decouple those two motions, which is a luxury. Furthermore, hairlessness helps us to sweat, as hair would slow down evaporative cooling.
- The aquatic ape hypothesis: Another idea holds that humans became bipedal because an elevated head helped them when wading and fishing. Aquatic mammals tend to either have very dense hair or no hair at all (whales, dolphins, pigs - kinda, etc.). This idea is not as crazy as it sounds, and some random observations support that we evolved to be in or near wet environments. For example, you know how your fingertips get wrinkly when they’re in water for a while? Well, that reaction is regulated by your nervous system, and is not a direct effect of wetness. Furthermore, those wrinkles have been demonstrated to aid your ability to grip wet rocks.
- The filthy fur hypothesis: Fur is not as good as clothing, because you can remove and clean clothing. Fur, on the other hand, is always full of parasites. Consider the two hairiest parts of the body, the scalp and the crotch; both are subject to lice. This argument holds that we lost fur because of the terrible parasite load associated with dense fur. It also argues that the few remaining hairs can help you feel crawling parasites and impede their progress (I have a hairy back, and can attest to this. Good luck, ticks!) We either replaced fur with clothing gradually, or else picked it up later to cover our nakedness, especially as we went into colder climates, depending on the timeline (which I will admit isn’t known to me).
The remaining hair may serve a number of purposes, but it seems to help prevent sunburn, demonstrate sexual maturity, channel water flow, filter air, increase sensation and sensory range, and possibly trap aroma (while many probably no longer find this desirable, body odor was considered sexy even in historical times, and still is in some places). Some people here have asked if (or argued that) a trait must have been selected for if we see it today, but that’s not always the case. As hard as it is to accept, some things are the way they are purely by chance. Red hair is frequent in Ireland in spite of no known selective benefit. Eyebrow shapes could be in the same category. Again, no one knows.
ELI5: Listerine kills bacteria in my mouth, but I know it's not killing 100%. Aren't I genetically engineering superbug bad breath bacteria by using it?
A massive dose of alcohol isn’t like an antibiotic.
Antibiotics work by targeting very specific proteins that the bacterium needs to survive. If it can figure out a way to change that one protein so that the antibiotic doesn’t work anymore but the protein still gets its job done then it’s progeny will be highly resistant to the antibiotic.
Something like an alcohol solution just straight up tears the cells apart. Some organisms like yeast can deal with decently high alcohol concentrations, but it’s a lot more difficult for organisms to deal with and pretty much nothing’s surviving what’s in mouthwash (the amount of alcohol in mouthwash way outstrips even what something alcohol-tolerant like yeast can survive).
“99%” or whatever percentage they state that will be killed is due to the coverage of the alcohol. That is, it kills 100% of the bacteria it touches, and it touches about 99% of what you are trying to kill, NOT that 1% is touched but somehow impervious.
Thursday, 4 February 2016
ELI5: Getting sick from a 'bacteria' vs. 'virus'
Bacteria produce harmful chemicals as part of their life processes. They use up your body’s resources (like eating your sugar or even eating your cells) and spit out toxic waste. Sometimes that waste is specifically designed to protect the bacteria by killing your immune system cells that try to attack it. But it also just basically poops all up in your body, which causes some damage. The symptoms of bacterial infections are related to what waste products the bacteria produces and where the bacteria is living. Your body fights bacterial infections by basically eating them, along with some other toxic chemicals that destroy them.
Viruses hijack the DNA in your cells to make more of the virus. They invade the cell and tell it to stop doing whatever it’s doing that your body needs it to do, and instead all it does is manufacture more of that virus. Eventually, the cell dies - usually by literally exploding - when it fills up with copies of the virus. Those viruses go on to infect other cells. Viral symptoms are caused by your body’s own attempt to kill them, and by the deaths of the cells they’re infecting. Your body fights viruses also by eating them, but it’s harder because they’re a lot smaller and have special protein shells that disguise them as “totally not a virus don’t eat me you guys”.
For extra fun, there are also prion diseases! Prions are proteins that folded the wrong way. When properly-folded proteins come into contact with prions, they re-fold into the same wrong shape as the prion. Your body can’t do anything about it because although it’s folded wrong, it’s still a protein that’s supposed to be there. Proteins are the way your body communicates and accomplishes certain things, so folding them wrong can really muck-up what is supposed to happen. In the case of Mad Cow Disease, as more and more proteins turn into prions, your brain turns to mush and gets holes in it until you go crazy and die.
If you think of your body as a factory that builds cars: bacteria are like a drunk hobo sneaking into your factory and dumping empty wine bottles into the machinery so it breaks. Viruses are like a roomba wandered in and reprogrammed your factory to start making more factory-invading roombas instead of cars. Prions are like a weird European car showed up and crashed into one of your factory’s cars after it left the factory, and now they both keep crashing into other cars (which then go on to crash into more cars) and also they all keep crashing into your factory.
Also fungal infections. Fungi can’t produce their own food, so they steal yours. Often that means invading parts of your body to get to it, and dumping toxic waste like bacteria. In the factory, a fungus would be someone building a shed attached to your factory and stealing your power so your factory doesn’t have enough to run and dumping garbage into your factory.
Also also, parasites. Parasites do the same thing as bacteria, but they’re [often] multicellular, so they’re much larger. Instead of a bunch of them, it’s usually a few big ones (although sometimes also a lot of them). In the factory, a parasite would be like the mafia moving into your factory, breaking stuff, and punching you right in the kidneys (or more likely, in the intestines) while they steal your money.
ELI5: Why does releasing an empty bow shatter it?
A bow pulled back is storing a lot of energy. With an arrow in place, that energy is transferred (mostly) to the arrow, and it happens much more slowly. Without an arrow, the bulk of the energy gets absorbed by the string and limbs, and it happens much more quickly, so it’s more of a sudden shock. Sudden shocks can be more damaging.
