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One day, all friction ceases to exist on earth. While I'm sure that the occasional sliding coffee would annoying, life on earth would change. However would this mean the end of mankind? Would there be any survivors?

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closed as too broad by JDługosz, Hohmannfan, Thucydides, Frostfyre, Josh King Sep 5 '16 at 2:42

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Questions in the form of "What if we lived in a world exactly like this, except physics rule ____________ was different" have a long history on this SE of not having good answers because the answer is always "The universe ends" You just can't pick and choose physical laws that way. This one has a strong risk of going the same way as the other questions. In particular, as Nobody pointed out, there is no fundamental "law of friction" in modern science. Friction is an effect that is derived from the application of other laws. Do you intend to undo those underlying laws, which will certainly $\endgroup$ – Cort Ammon Sep 4 '16 at 17:03
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    $\begingroup$ end in answers of "the universe ends," or are you looking to bring magic into the story, creating a magical process which counteracts friction? If so, we would need more clarification on what exactly that magical process is doing (since it is by definition not physical, so we can't look its laws up). We'd need to know exactly what it considers to be friction. $\endgroup$ – Cort Ammon Sep 4 '16 at 17:04
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    $\begingroup$ It puts the lotion on its skin. $\endgroup$ – Xplodotron Sep 4 '16 at 17:33
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    $\begingroup$ At which level friction is gone, after all, friction is molecule to molecule collision. What about friction of rough surfaces? As things get coarser, you will end up removing collision altogether, destroying the universe with it. $\endgroup$ – Cem Kalyoncu Sep 4 '16 at 18:31
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    $\begingroup$ @CortAmmon Well I guess for some laws you might get lucky, mostly if you are just altering a constant by like 10% or 20%. In my opinion the problem is mainly that you don't build stories like this, you get a thought experiments about physics instead (which I do like, that's why I answered :-). For building stories, either you know enough so you don't need to ask the question or you should stick to making fantasy stories about the way the author imagines science and the world. $\endgroup$ – Nobody Sep 4 '16 at 19:41
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In short: You can make it disappear, but friction will take a large part of physics, all of chemistry and microbiology with it when it goes. This could be an interesting fantasy world, but you definitely wouldn't find anything which works as you are used to. No humans, animals, plants, Earth-like planets, not a sun which works the way ours does. You could invent something very abstract and alien and explore it from psychological, sociological, etc angles.

Long answer:

Friction can't disappear.

There is no physical law you could change to make it disappear.

Friction is not a natural constant or something, but a consequence of the very way our world fundamentally works.

Friction is basically like gear wheels skipping teeth. Everything has a rough surface to some degree (because it's built from atoms and molecules), so when you rest two surfaces against each other those irregularities interlock like the teeth on the gear wheels. This keeps surfaces from sliding against each other. When you put too much work into making them slide, they slip out of each other and start skipping over each other.

If you want to make friction disappear you need to build up completely new physical models from scratch, ditching the whole atom->molecule->macro world structure and substituting something which is not based on little particles so it can be smooth.

I think some ancient Greek philosophers had some ideas like this, maybe look at those. Essentially the world would consist of homogeneous blobs of matter (which stay homogeneous no matter how you look at them, this likely implies that they can be divided infinitely for example).

Once you got such a model there is probably a parameter which you could tune to add/remove friction. If created very carefully, a large change in friction over a shorter than evolutionary timespan might not kill everything, but such a live-configurable model would be multiple times more complicated to construct. In both cases:

Creating such a model in a reasonably self consistent if not very detailed way would probably take a team of natural scientists months if not years. So you'll be doing a lot of hand waving (and still have to think very hard) and unless (or even if) you've got a very good general knowledge of the natural sciences anyone trained in any natural science will still casually spot problems in your model. You would be reinventing almost all of science's models for everything on the microscopic level and would probably have lots of trouble if you want to keep the macroscopic world similar to the one we know.

Then, you still keep a lot of friction like effects. Those are sometimes also called just friction, but they work completely differently and I consciously decided to exclude them for reasons detailed below:

  1. Fluid drag: You probably know that fast moving objects in an atmosphere, like cars, bikes, trains and planes spend most of their power overcoming "friction", once they are at speed (so are not accelerating and not moving very slowly). This is not true. Overcoming friction is a small part of the power they need and it becomes smaller as vehicles move faster. They spend their power moving air out of the way, accelerating that air. This is not friction, this is inertia. This directly is Newtonian motion. You've got multiple possibilities here: a) You accept this. b) You ditch Newtonian motion and if you do that, stuff gets seriously weird. c) You construct your model so that the predominant "gas" in the atmosphere behaves like a super fluid which probably solves part of that problem but raises a whole load of other ones (for example concerning the organisms which maybe still do something like breathing). If you want a model with parameters which you can tune from "friction" to "no friction" without killing everything in it, don't do it.
  2. Macroscopic friction: Using an other physical model for the world you could claim that those small irregularities which I previously explained stop existing, so friction disappears. But this would just be friction on a molecular level. When you have macro level (visible) irregularities, like on asphalt roads and tires, then those would still show some (greatly reduced) "friction" effects. You couldn't properly drive a car anymore, but it would probably not slide over asphalt as over ice. You could still walk (especially barefoot, clinging to irregularities in the ground). Assuming something like vehicles and humans still exists, which as mentioned is not easy. You could try to remove that kind of friction too, but this would mean that all of your world would need to be smooth on a macro level too. And once one macro level is smooth, you can always go one more macro level up, until everything is just one huge round blob and no world remains.

That said, if you are very good at explaining just a few reasonably easy things and hand waving the whole complicated rest in a way which doesn't make scientifically inclined readers cringe, then this could lead to a very interesting, novel fantasy world.

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    $\begingroup$ "You probably know that fast moving objects in an atmosphere, like cars, bikes, trains, planes spend most of their power overcoming "friction", once they are at speed (so are not accelerating and not moving very slowly). This is not true." — Of course it is true. It is one of the effects that are subsumed under the name "friction". $\endgroup$ – celtschk Sep 4 '16 at 13:57
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    $\begingroup$ @celtschk I chose a definition of friction for my answer which is common enough among physicists and applied it consistently. What I mean with it is clear from the context; I explained it at the beginning of my answer. $\endgroup$ – Nobody Sep 4 '16 at 14:10
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    $\begingroup$ "This is not true" is not the same as "this is not included in the specific model of friction I'm describing above". You are accusing everyone who makes that claim of telling things that are not true. $\endgroup$ – celtschk Sep 4 '16 at 14:27
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    $\begingroup$ @celtschk I concur the phrase is a little simplistic, but the point remains. Calling fluid drag friction is at least misleading. While those four words may be debatable, their very precise meaning is not central to my answer and especially with the revised context clear enough. I'm not going to change them. $\endgroup$ – Nobody Sep 4 '16 at 14:37
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    $\begingroup$ @Xplodotron I don't know much about superfluids and the impression I got is that other people don't know much more either. Because I don't know how they work, I couldn't tell what switching from a particle to a smooth physical model would change about them. Likely answer: Everything. When developing a fictional physical model for a story you would likely omit them because they don't occur in everyday live. But this makes me think that maybe, just maybe, you could plausibly turn off fluid drag with a reasoning like this. It wouldn't be superfluids but inspired by them. $\endgroup$ – Nobody Sep 4 '16 at 15:45
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Yes, everyone would probably die.

Without friction you can't grip against the ground so if you try to walk you will fall you will slide without stopping until you hit an uphill. At that point you will decelerate due to gravity and them slide back down. You will slide back down and along until you hit another uphill. You will then pendulum up and down the two hills until you eventually stop by hitting something like a wall. Everyone will end up either at the bottom of walls, rocks or holes or sliding around. Unable to move and slowly dying through lack of water or dying from broken bones.

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  • $\begingroup$ You mistake the force of opposites with the force of friction, one is sliding the other is pushing/pulling $\endgroup$ – TrEs-2b Sep 4 '16 at 8:33
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    $\begingroup$ @UncleTres I don't see your point. Without friction people can't grip so they will fall and any speed they have will cause them to slide. $\endgroup$ – Bellerophon Sep 4 '16 at 8:35
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    $\begingroup$ Well I would assume they would walk, just that it would look like one of those ice slip montage videos Everyday... $\endgroup$ – Skye Sep 4 '16 at 8:42
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    $\begingroup$ Without friction, there is no way they will come to rest at the bottom of the hill, as it is exactly friction that would cause that. A frictionless pendulum would simply oscillate until eternity (or until something else stops it). $\endgroup$ – celtschk Sep 4 '16 at 13:53
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    $\begingroup$ Eventually someone would sneeze and go flying off like a rocket. People would figure out that instead of walking you would simply blow in one direction to move in the opposite direction. $\endgroup$ – Xplodotron Sep 4 '16 at 14:51
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If earth suddenly lost friction we'd all die in massive earthquakes and tsunamis as all the pent up tectonic energy everywhere is released at once. But after that we'd never have an earthquake again since now the plates are perfectly lubed. Not that we'd be around to care. Don't worry, the mud slides will give us a proper burial.

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  • $\begingroup$ Well there are countries which don't have natural disasters and I live in one :D $\endgroup$ – Skye Sep 4 '16 at 13:32
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    $\begingroup$ Dunes, hills, mountains, landfill garbage heaps would be blown flat by the wind. $\endgroup$ – Xplodotron Sep 4 '16 at 14:54
  • $\begingroup$ Not to mention my house. Suppose this happened while someone was skipping a stone? Would it ever stop? Friction is how kinetic energy turns into heat. Without it, where does the energy go? $\endgroup$ – candied_orange Sep 4 '16 at 15:24
  • $\begingroup$ @CandiedOrange - I was just thinking about people in San Francisco sliding down those lovely hills right into the ocean (if they didn't slam into something first). Once they hit the ocean, gravity would still pull them under the ocean surface. A stone would also sink into the water due to gravity. A stone skips because of resistance from surface tension. Gravity is constant so as energy is lost to the surface of the water the stone will not hop up as much each time (think of dropping a stone on a trampoline). $\endgroup$ – Xplodotron Sep 4 '16 at 15:53
  • $\begingroup$ Friction is WHY things lose energy after a bounce. $\endgroup$ – candied_orange Sep 4 '16 at 15:58
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I suspect a whole bunch of biological functions will go haywire, because they are designed to operate in the presence of friction. Chewing, how bones and cartilage move against each other, how food passes through the gut, how blood flows in your veins, and so on.

Biotribology is apparently the study of friction in biological systems. And here's a paper which discusses friction at micro and macro scale in living things.

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Things get very difficult.

Everything loose slides downhill, trading potential energy for kinetic energy as gravity accellerates it downhill, then goes uphill on the other side, being slowed by gravity converting kinetic energy back into potential energy until it slows to a stop and starts sliding down again.

With no friction, pebbles, sand and soil grains slide freely like a liquid. so all the beaches run down into the depths of the ocean. No more beaches. And plant cover doesn't help - soil or sand particles can flow out between the roots if there are big enough gaps and its downhill. If not, then the rest of the sand/soil just runs out from underneath.

With no friction at all, I suspect things will work like a giant newtons cradle (remember those? a set of balls in a line where an impact at one end sends the same number of balls bouncing off the other end of the line. The only damping factor would presumably be where distortion from impact turns some of the energy into heat - but does that need friction between atoms? I have this vision of beaches sliding into the sea only to come sliding back out on the other side of the ocean (or maybe more likely bouncing back when the sand hits the sand from the other side...)

Picking things up is hard - unless there's a closed loop handle, or a bulge above on something you can get your hand more than halfway round, they'll just slide away. If you manage to pick up a slanting sided glass, don't squeeze to hard or you'll overcome the weight from gravity and squirt the glass out of your hold.

There is nothing holding nails, screws, nuts, or bolts in place, except gravity. Any downward facing nails fall out. Any downward facing nuts, screws, or bolts unscrew and fall off or out. Anything else just has some of the weight of the nail/screw holding it in place, so that's not going to be good either - any noticable force pulling outward and out it comes.

You can't walk anywhere - you're sliding, and can only exert a force perpendicular to the surface you're on. And there are no brakes.

Given enough advanced warning, you could probably set something up to allow people to function = an environment with lots of grab handles, so you can move around from handle to handle (Though you may end up penduluming if you only hold on to one). hydroponics (or a sealed tub to stop the soil floating away - though the soil would act like a liquid anyway) would let you grow stuff (though you'd need tools to catch and handle seeds. Eating might be challenging...

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Well first, on the macro scale, we have cars. Without friction, cars will not be able to gain or lose momentum, this means two things; one, all emergency vehicles cannot help people and two all currently moving cars will not be able to stop.

An benefit is the remaining existence of pressurized movement, which will allow most technology and (most importantly) the biological technology to go unaffected, so your heart will still pump blood. Do not think this means that you will be fine, sound will move much faster as their is much less friction to slow it down; it may go fast enough to make every sound worthy of a sonic boom, every living thing on earth will likely go deaf.

Basically what we have is the removal of the main method of decreasing momentum, all that can stop an object is gravity and interference. This means all planes will be left to die as will all people in elevators. Luckily opposite force (a la newtons law) is not effected, so walking is unaffected. With this we have our answer; anyone, anywhere in a moving object will likely die, I would estimate that this at least half the population (though I suspect much more)

Will this cripple humanity? yes. Will they be unable to restore the world as they once knew it? Absolutely. Will everyone die? no, there will be hundreds of millions of survivors, all scared, in pain and confused.

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  • $\begingroup$ I got confused when you said "... Sound is slowed down, sound will move much faster,..." ... Is that an error? $\endgroup$ – Skye Sep 4 '16 at 8:40
  • $\begingroup$ No, but I was unclear, I will clarify $\endgroup$ – TrEs-2b Sep 4 '16 at 8:44
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    $\begingroup$ I disagree. No friction means no walking or running; you'll slip and fall and then roll along the slightest incline. $\endgroup$ – nzaman Sep 4 '16 at 10:19
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    $\begingroup$ Walking is affected; have you ever tried to walk in ice skates? We rely on the friction between foot and earth to move forward. Without friction, our attempt to push the foot backwards will just result in the foot moving backwards. $\endgroup$ – Patrick Stevens Sep 4 '16 at 10:20
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    $\begingroup$ Sound waves don't work like this. They aren't "slowed" by friction. Their speed mainly depends on the mass density of the medium. $\endgroup$ – Nobody Sep 4 '16 at 13:36

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