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We are not mostly empty space

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Re: We are not mostly empty space

#41

Post by goatlover »

starchild_3001 wrote: post #28

Is it just me who found the technical description and analogy here lacking? There's nothing that suggests electrons are a cloud. Yes, a "cloud" defines the probability where they can be found, but electron doesn't occupy the cloud. Electron is always a point, no matter what wave function it has. Therefore, from this perspective space is all empty. If you invoke path integrals and infinitely many things bubbling in an…

If an electron is always a point, how does it have a wave function? Field is the proper term for "cloud", and Quantum Field Theory is an alternative description of the universe, where fields are fundamental, and particles are excitations in the fields.

Re: We are not mostly empty space

#42

Post by lopmotr »

mannykannot wrote: post #27
not2b wrote: post #22

Earlier quoted context omitted.

For anything that responds to the electromagnetic force, you're filled with fields. For something that responds only to the weak force, you're almost entirely empty space.

In the English-language usage I grew up with, 'occupied' means that there is something there, while 'filled' means occupied to the point where nothing more can be added. The former does not imply the latter. In this usage, space itself (the 'empty' space of the article's title) is implicitly not something. This usage may seem to be an accidental issue of language, resulting from an incomplete understanding of physics…

This whole idea of empty space within atoms is just nonsense using English grammar as a substitute for physics. It's a meaningless statement either way until you define the terms specifically enough. And by doing that, you can choose whatever answer you want. "occupied to the point where nothing more can be added" isn't specific enough because you can still add a lot of photons to a "filled" glass of water, so that means it's not filled by that definition even though it is by common sense. It just shows the irrelevance of everyday words and concepts at the subatomic scale.

Even a neutron star is practically invisible to neutrinos which can easily pass through it despite it's being "filled" with neutrons.

Re: We are not mostly empty space

#43

Post by goatlover »

saagarjha wrote: post #38
andrewprock wrote: post #30

Earlier quoted context omitted.

Yeah, the fact that neutrinos pass through us largely validates the notion that we are in fact mostly empty space.

Depending on the conditions, it is through that neutrinos can pass through even very degenerate matter like that which forms neutron stars. "Empty space" really doesn't mean all that much if the thing that is interacting with it does so weakly.

Does this mean a black hole is "full"?

Re: We are not mostly empty space

#44

Post by chias »

saagarjha wrote: post #35
Koshkin wrote: post #34

“Empty space” is a completely relative notion. If I have a heavy steel safe which I do not have the key for, whether there is an empty space inside it is irrelevant, and the space occupied by the safe cannot be seen as being (partially) empty in any practical sense.

You can easily tell if it is hollow without opening it, however.

Just wait until you come across my safe, protecting my extremely rare and valuable collection of packing peanuts...

Re: We are not mostly empty space

#45

Post by goatlover »

Retric wrote: post #18
tristanstcyr wrote: post #7

Earlier quoted context omitted.

From what I understand, the idea of "empty" no longer makes sense at that level. All you have are fields. There, everything is made out of fields and fields are everywhere. There is therefore no "empty" really anywhere, including inside yourself.

Physics is all based on predictions not arbitrary definitions. To suggest something is filling space you must be able to hit it with something else. This talk of empty space, comes from actual experiments. Shoot a neutral particle through that cloud and you generally find it really was empty. Wave particle duality doesn’t mean a particle is in every location, just that it could be in every location. After detection y…

Physics does say fields like gravity and EM fill all of space. That's not arbitrary, it's part of QM and Relativity.

And wave particle duality could mean that a particle is a wave when it's not being detected.

Re: We are not mostly empty space

#46

Post by mirimir »

themodelplumber wrote: post #17
kylec wrote: post #11

Empty space, by definition, is space that can be filled by something. So how closely can atoms pack together? A neutron star has a density of 10^17 kg/m^3, whereas the typical human being is about 10^3 kg/m^3. I could fit the matter of trillions more human beings in the same space I'm taking up now. So yeah, I think there's some empty space in me.

So the author is saying fields are already filling things up, right? To compare this to the "we can pack them atoms tighter" model seems to be confusing the author's model with another, separate mental model, one in which we can fill up more. But the author's model says we're full. Full of this field stuff. Not so? IANAS

Yeah, they're probability distributions, not fields. So electrons, protons and neutrons are still tiny, even though their positions are uncertain. And so atoms are still mostly empty space.

Re: We are not mostly empty space

#47

Post by mirimir »

mannykannot wrote: post #27
not2b wrote: post #22

Earlier quoted context omitted.

For anything that responds to the electromagnetic force, you're filled with fields. For something that responds only to the weak force, you're almost entirely empty space.

In the English-language usage I grew up with, 'occupied' means that there is something there, while 'filled' means occupied to the point where nothing more can be added. The former does not imply the latter. In this usage, space itself (the 'empty' space of the article's title) is implicitly not something. This usage may seem to be an accidental issue of language, resulting from an incomplete understanding of physics…

Well, that space is filled, but only because of quantum interactions, and not because it's empty.

Re: We are not mostly empty space

#48

Post by dwaltrip »

mirimir wrote: post #46
themodelplumber wrote: post #17

Earlier quoted context omitted.

So the author is saying fields are already filling things up, right? To compare this to the "we can pack them atoms tighter" model seems to be confusing the author's model with another, separate mental model, one in which we can fill up more. But the author's model says we're full. Full of this field stuff. Not so? IANAS

Yeah, they're probability distributions, not fields. So electrons, protons and neutrons are still tiny, even though their positions are uncertain. And so atoms are still mostly empty space.

I believe there is non-zero vacuum energy. So "something" is going on, whether it be virtual particles popping in and out of existence, even in "empty space".

Granted, I don't really understand the details of what this means, but that's what I remember of the current science.

Re: We are not mostly empty space

#49

Post by mirimir »

dwaltrip wrote: post #48
mirimir wrote: post #46

Earlier quoted context omitted.

Yeah, they're probability distributions, not fields. So electrons, protons and neutrons are still tiny, even though their positions are uncertain. And so atoms are still mostly empty space.

I believe there is non-zero vacuum energy. So "something" is going on, whether it be virtual particles popping in and out of existence, even in "empty space". Granted, I don't really understand the details of what this means, but that's what I remember of the current science.

Yes, vacuum energy. But that's still probability distributions, and so almost all of the vacuum is empty at any given time.

Most physicists would likely say that there's no point trying to visualize this stuff in mundane terms. Or at least, that's what they were saying the last time I took a physics course.

Re: We are not mostly empty space

#50

Post by bouncycastle »

kylec wrote: post #11

Empty space, by definition, is space that can be filled by something. So how closely can atoms pack together? A neutron star has a density of 10^17 kg/m^3, whereas the typical human being is about 10^3 kg/m^3. I could fit the matter of trillions more human beings in the same space I'm taking up now. So yeah, I think there's some empty space in me.

You'll also develop a gravitational field and maybe things will start orbiting you!
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