Small Physics Questions

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Kanastrous
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Small Physics Questions

Post by Kanastrous » 2016-01-07 09:01pm

Because this touches upon what are probably pretty basic physics I posted here:

Think of a magical process (physics part to come) that reduces human beings by about 1:18 (about the scale of old-school Star Wars action figures) - for present purposes the means of smallification aren't immediately relevant.

Is this a sufficient reduction in scale that the little reduced-sized people would notice unusual effects, specifically:

would air become noticeably thicker from their perspective

would surface tension noticeably affect the behavior of water

would falls from a proportionately great height become less terminally energetic (that is, would a 1:18 scale person falling from the roof of a 1:18 scale three-story building be in much less danger than a 1:1 person falling from a 1:1 building) and by roughly how much

would the reduction of a little person's iris diameter affect the quality of their vision?

Are there any other unusual effects that people reduced to the scale would notice, or would further scale reduction be necessary before seeing any unusual effects?
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Re: Small Physics Questions

Post by Jub » 2016-01-07 10:01pm

I can comment on the stuff that I know about.

I know that falls from pretty much any height would no longer be deadly though they might cause injury. Consider that a 5'10 (1.75 m) tall 175 lb (79.5 kg) person would end up as a ~4" (10 cm) tall 1.2 lb (545 g) mini-person. Cats which are larger and weigh more have a non-lethal terminal velocity, so it would be safe to assume that a shrunk person would also have this benefit. I'd still probably want a wingsuit before diving off a human scale skyscraper, but parachutes probably wouldn't be required.

I don't feel like air would become any thicker feeling. Consider that a 1.2 lb mini-person would have gone from being nearly a nonillion times larger than an oxygen atom to well over an octillion times larger than an oxygen atom. When you're talking about things with a mass of ~5.36 x 10-26 kg it takes a lot of difference in scale before you'd really notice the difference. I'm not 100% sure on this one, but that's my best guess.

I think the surface tension of water runs into the same issue as the air. After all, a mouse can still swim and they weight as little as 30 g. So you'd probably need to take people down to insect size ranges before they would notice any unusual effects with surface tension.

I also suspect that shrinking would affect the range of sounds we can hear far more than what we see. Again it's the difference in sizes between the wave lengths of light and sound. This is the one I'm least sure on though and my google-fu is failing me on this one.

Things you might notice would be new found strength relative to your size, moving much slower in real terms while feeling like you're moving very rapidly, the strange shift in how things sound, the fact that you're much better able to radiate heat (to the point that you might not even work up a sweat under strain). These are the things I can think of off the top of my head.

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Re: Small Physics Questions

Post by Zeropoint » 2016-01-07 10:37pm

I just started my fluid mechanics course, so I'll be able to answer some of those questions in ten weeks. Ohh, wait. Jub's right about the falling--housecats have a terminal velocity which is borderline safe, and squirrels have a terminal velocity which is entirely safe, and 545 grams is squarely within their weight range. A tiny human might have to wear baggy clothing (like literal parachute pants), but they'd be able to fall safely from any height, relying on the air to keep them at a safe speed.

In other words, the air would feel thicker to them.
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Re: Small Physics Questions

Post by jwl » 2016-01-08 03:59am

Kanastrous wrote:Because this touches upon what are probably pretty basic physics I posted here:

Think of a magical process (physics part to come) that reduces human beings by about 1:18 (about the scale of old-school Star Wars action figures) - for present purposes the means of smallification aren't immediately relevant.

Is this a sufficient reduction in scale that the little reduced-sized people would notice unusual effects, specifically:

would air become noticeably thicker from their perspective
It kind of depends what you mean by that. They would still be able to undergo turbulent flow if that's what you mean.
would surface tension noticeably affect the behavior of water
Yes. For that reason, water was a bit of a nightmare for special effects people in old movies, because if you try to use it on a smaller model it looks different.
Would falls from a proportionately great height become less terminally energetic (that is, would a 1:18 scale person falling from the roof of a 1:18 scale three-story building be in much less danger than a 1:1 person falling from a 1:1 building) and by roughly how much.


Would the reduction of a little person's iris diameter affect the quality of their vision?
Yes. Firstly by the fact that a smaller pupil means that less light is getting in your eye, and secondly by diffraction.
Are there any other unusual effects that people reduced to the scale would notice, or would further scale reduction be necessary before seeing any unusual effects?
One other thing I can think of is the higher relative surface area would mean they would lose heat more quickly. When the surrounding temperature is below body temperature, it will feel colder.

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Re: Small Physics Questions

Post by LaCroix » 2016-01-08 07:13am

Their hearing would also be impaired - a smaller ear channel can't let sound waves pass as well, I'd assume they loss a good bit of hearing. Everything should sound be a bit off/hollow as the max amplitude is dampened. They may even lose access to some low frequencies due to the size of their hearing apparatus. Most small animals have a range limit starting at 1khz. That shouldn't affect human speech too much, but most likely, everything under 1khz would be gone or barely audible. try having a sound guy filter out everything under 1khz and listen to it, and you might get a good idea what things would sound like.
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Re: Small Physics Questions

Post by Kanastrous » 2016-01-08 12:07pm

Thanks for the responses so far - in terms of vision what I wondered was whether the reduction of one's iris aperture to some fraction-of-a-millimeter diameter would mean no more near or farsightedness: would the pinhole effect render the tiny person's vision 20:20 or better?
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Re: Small Physics Questions

Post by SCRawl » 2016-01-08 12:13pm

jwl wrote:
Would the reduction of a little person's iris diameter affect the quality of their vision?
Yes. Firstly by the fact that a smaller pupil means that less light is getting in your eye, and secondly by diffraction.
I'm less certain about the first part. Although, yes, clearly less light would be getting through the pupil, the area it's illuminating is similarly reduced. The two should exactly offset.

What I would be more concerned (as Jub pointed out) about is the frequencies of light and the ability to resolve them. The various photo-sensitive cells in our eyes are adapted to wavelengths in the range of a few hundred nanometers. If these cells are reduced in size by a factor of 16 (by "magic" or whatever) would the frequencies to which they would respond not also be similarly reduced? I'm imagining that visible light would be invisible to a thus-diminished human, and that he would instead be seeing in the UV or X-ray part of the spectrum. This might have the effect of some of the shorter wavelengths not being visible at all.

Similarly -- again, as Jub (and LaCroix) mentioned -- hearing should be affected, both by amplitude and by frequency.
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Re: Small Physics Questions

Post by Lord Revan » 2016-01-08 12:18pm

Btw would you heart be strong enough to pump blood, I seem to remember that small creatures like squirrels or mice have larger hearts relative to their bodies then humans (human heart is actually quite small relative to body size).
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Re: Small Physics Questions

Post by jwl » 2016-01-08 01:21pm

SCRawl wrote:
jwl wrote:
Would the reduction of a little person's iris diameter affect the quality of their vision?
Yes. Firstly by the fact that a smaller pupil means that less light is getting in your eye, and secondly by diffraction.
I'm less certain about the first part. Although, yes, clearly less light would be getting through the pupil, the area it's illuminating is similarly reduced. The two should exactly offset.

What I would be more concerned (as Jub pointed out) about is the frequencies of light and the ability to resolve them. The various photo-sensitive cells in our eyes are adapted to wavelengths in the range of a few hundred nanometers. If these cells are reduced in size by a factor of 16 (by "magic" or whatever) would the frequencies to which they would respond not also be similarly reduced? I'm imagining that visible light would be invisible to a thus-diminished human, and that he would instead be seeing in the UV or X-ray part of the spectrum. This might have the effect of some of the shorter wavelengths not being visible at all.

Similarly -- again, as Jub (and LaCroix) mentioned -- hearing should be affected, both by amplitude and by frequency.
Hmm. I suppose it depends if the reduced-size rods and cones have a the same sensitivity to a given power of light or to a given intensity of light. However, if the power goes down so low you have less than one photon per cell, you have a problem.

I've googled this to find out, and it turns out that the human rods do respond to single photons at low light levels, but your brain only gets the signal if 5-9 of them are activated simultaneously. On the face of it, this means that getting smaller losing vision at low light levels. However, 90% of the light is lost on the way there in a normal eye. Presumably, in a smaller eye, it will have less distance to get lost and thus you get a brighter picture. However, since the light going into the iris scales with area, the reduction in light levels due to a smaller eye outweighs the lack of light lost. Therefore you do get weaker vision at low light levels when you are smaller. source: http://math.ucr.edu/home/baez/physics/Q ... hoton.html

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Re: Small Physics Questions

Post by SCRawl » 2016-01-08 01:53pm

I see your point, and I agree with the reasoning. According to the frequency issue, I think that this will also lead to weaker vision, since there's less EM radiation going around in those frequencies which would be picked up by the smaller cones.

As to Kanastrous' clarified question about whether or not suboptimal vision would be corrected by having such a small pupil -- presumably the main reason this thread exists -- I must confess that I'd have to think about it some more.
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Re: Small Physics Questions

Post by Elheru Aran » 2016-01-08 02:04pm

You're totally working on Ant-man 2, aren't you :p
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Re: Small Physics Questions

Post by Kanastrous » 2016-01-08 08:59pm

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Re: Small Physics Questions

Post by Jaepheth » 2016-01-09 04:47am

Would these people still be able to eat or breathe? As in would your blood still be able to chemically react with the oxygen whose molecules are now relatively 18x larger than they're supposed to be? Wouldn't you need to take canisters of shrunken gas with you? (ala that one Star Trek DS9 Episode)
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Re: Small Physics Questions

Post by Elheru Aran » 2016-01-09 11:00am

Jaepheth wrote:Would these people still be able to eat or breathe? As in would your blood still be able to chemically react with the oxygen whose molecules are now relatively 18x larger than they're supposed to be? Wouldn't you need to take canisters of shrunken gas with you? (ala that one Star Trek DS9 Episode)
No, because you're still millions or billions of times bigger than those molecules. You'd have to get REALLY small for that to matter, from what I understand.

Kanastrous, I believe you... I know you probably wouldn't be able to talk about it anyway so I'm just guessing :D
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Re: Small Physics Questions

Post by jwl » 2016-01-09 01:43pm

Elheru Aran wrote:
Jaepheth wrote:Would these people still be able to eat or breathe? As in would your blood still be able to chemically react with the oxygen whose molecules are now relatively 18x larger than they're supposed to be? Wouldn't you need to take canisters of shrunken gas with you? (ala that one Star Trek DS9 Episode)
No, because you're still millions or billions of times bigger than those molecules. You'd have to get REALLY small for that to matter, from what I understand.

Kanastrous, I believe you... I know you probably wouldn't be able to talk about it anyway so I'm just guessing :D
I think jaephath's question is an interesting one and it rather depends on how the miniaturisation works.

If the miniaturisation works by shrinking the atoms themselves, yes you will need shrunken oxygen and shrunken food to actually have compatible reactions. You might be millions or billions of times bigger than the molecules, but the molecules in your own body that are reacting with them are not, and furthermore most enzymes work based on matching to the reactant's shape. But considering that the properties of the atoms and molecules themselves are somewhat dependant on their size, it's likely miniaturised oxygen won't behave much like normal-scale oxygen and the whole system won't work.

If the atoms do not shrink but the cells do, you will need some fundamental messing around with the cell to get them to work normally. For example, white blood cells have a lobed nucleus to allow them to squeeze it between other cells. Why don't they just have a smaller nucleus? Because doing so will mean the nucleus will have less chromatin in it, which means less genetic information. So if you are shrinking the nuclear volume by a factor of 6000, you either need to use 6000 times less genetic information or make the chromatin 6000 times more efficient at holding that genetic information.

If the atoms and the cells do not shrink but the body does, this means less cells, which means less rods, neurons, etc.

Although it may be just better if this is being used for a story to just handwave this stuff, because what you are really saying is that miniaturisation is impossible; and that might damage the suspension of disbelief in a miniaturisation story.

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Re: Small Physics Questions

Post by Purple » 2016-01-09 04:05pm

The way I'd do it is I'd establish that the miniaturization effect is essentially a field encompassing the character. And within that field things are just physically smaller on the outside. And anything that enters his body like say food, water, air etc. is shrunk to match. So the molecules in his body work the way they do in a big body because from their perspective they are just as big as they were before. It's just you, the observer who witnesses a shrinkage in size. It's sort of like turning the entire body into a TARDIS.
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Re: Small Physics Questions

Post by jwl » 2016-01-10 05:25am

A bit like Capone Bege from One Piece then?

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Re: Small Physics Questions

Post by Purple » 2016-01-10 05:27am

jwl wrote:A bit like Capone Bege from One Piece then?
No idea what that is.
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