
We are not mostly empty space - yusufk
https://medium.com/starts-with-a-bang/you-are-not-mostly-empty-space-b836ca510313
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kylec
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.

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themodelplumber
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

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mirimir
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.

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state_less
Rather than thinking of space as empty vs non-empty, it might be better to
think of space as a relationship between things.

I think you make less commitments of space this way.

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limomium
That's also the difference between raster and vector modeling of virtual
geometry. There is an area on a graph where one literally takes less space on
a computer's memory than the other, for representing essentially the same
information.

But there are other trade-offs.

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state_less
Thought you might find this interesting.

[https://www.quantamagazine.org/coder-physicists-are-
simulati...](https://www.quantamagazine.org/coder-physicists-are-simulating-
the-universe-to-unlock-its-secrets-20180612/)

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starchild_3001
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 and out of
existence, space suddenly fills up. But the author doesn't even mention that.

If you want to understand this stuff, read up Feynman's descriptions &
lectures on QED.

Downvote for this article (sorry).

~~~
Koshkin
Some think that electron is a string!

~~~
starchild_3001
Let's argue about that when there's a modicum of evidence :)

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vaidhy
Language is ambiguous and we are debating between two meanings of empty -
nothing there or nothing there, but can be replaced with something else. And
we have the added distraction of what nothing means - no physical, permanent
“particles” or the abstract empty space.. We can go down the rabbit hole of
parsing semantic meanings.

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scarmig
How often do objects interact with our bodies when passing through us?
Neutrinos, very rarely. The atoms of an aluminum bat, very commonly. Light? It
depends.

Something being "empty" or "full" all depends on spatial and energetic scale.

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

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knzhou
But visible light can't get through us at all. Does that prove that we _aren
't_ empty space? The whole point is that this criterion is incredibly
ambiguous.

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jcelerier
> But visible light can't get through us at all.

visible light definitely gets through me when I put my hand in front of a
bright light source

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mcnamaratw
All the article says is that "empty" isn't enough information.

If "empty" means "I can put electrons in there", then it takes more binding
energy to pack more electrons into the same space. If you want to pack more
electrons in, you have to squeeze harder.

Example: you _can_ confine an electron to a tiny part of an atom (electrons in
inner shells of heavy atoms, for example) but those electrons are very tightly
bound (held in by very high ionization energies).

Or the "emptiness" of an atom could be measured using neutral particles, which
don't interact with the electrons at all and sail right through as if the
electrons were empty space.

For what it's worth this is normal sophomore physics. There's no way to just
dismiss it. But there's also no way to claim it's less than a hundred years
old.

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balnaphone
> For non-quantum objects, this isn’t a problem, as different methods of
> measuring an object all give you the same answer. Whether you use a
> measuring stick (like a ruler), high-definition imaging, or a physics-
> reliant technique like Brownian motion or gravitational settling, you’ll
> arrive at identical solutions.

Right off the top, it's made clear this author doesn't know what he or she is
talking about. From at least the time of de Moivre, around 1740, the problem
of estimating an accurate true value from multiple differing measurements was
recognized in its own right as a problem. By 1810, Gauss and Laplace had
discovered the basics of statistical estimation, the form of the normal
distribution, results including the central limit theorem, and regression
techniques such as non-linear weighted least squares. Now, almost 200 years
later, the problem still exists, and is being worked on in various forms and
circumstances.

To give a simple example, take 1000 frames of well-exposed video of a still
scene, with constant illumination, and constant exposure settings on the
camera. Now try to estimate how many photons, within a constant multiplicative
factor, are coming from each point in the scene. Most of the measurements will
show a normal distribution, but at the extremes of exposure, something more
complex is going on (perhaps to do with sensor non-linearity, censored
sampling, or something else). This is one of the basic theoretical problems in
HDR imaging, and is an active area research (i.e. unsolved, as of today).

It's very hard to get past that paragraph -- which is the first one in answer
to the question "why?".

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nobrains
So, in an atom, how much volume does the electron cloud occupy? It's more than
the volume an electron occupies, but, in the upper end, does it occupy all the
space from the electron to the nucleus? (And also because it is rotating, that
space then occupies all the area surrounding the nucleus as well?)

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at_a_remove
This has the sound of _grooviness_ to it.

One on hand, electrons as point particles sure sounds empty enough. On the
other hand, the fields fill everything.

But on the gripping hand, you could set the volume of the electron to
something ludicrously large, like the volume of a proton, then use the charge
distribution of whatever "orbital" to trade that charge for an equivalent
amount of proton-volume, as sort of a percentage filled of unit volume ...
integrate, and you could get a sense of the density.

That, I think, is about as fair as you could ask for when dealing with point
particles that are still smeared around.

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badrabbit
Excellent explanation. My question after this is, at a macro level,how much of
space is actual pure space. Pardon the childish question but how exactly would
one measure space (nothing exists at this point) without introducing something
that might be displaced by the measurement,or how can one be sure space isn't
made up of lower energy qanta that are displaced by higher energy
particles,much like how solids displace gases and liquids?

~~~
jonahbenton
Yeah, agree with this and disagree with other comments, thought this was a
very effective communication of a better thought-model for understanding-
still in largely colloquial terms- what is going on.

To the point about "pure space"\- I suspect the colloquial answer is that
there isn't any pure/just space. I know that Wolfram is also not respected on
here much but I like his- not intentionally metaphorical- arrival at a story
for space being a process.

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Digit-Al
My understanding of quantum physics is miniscule; so a question: would it be
potentially true to say that the concept of "emptiness" as we define it is
essentially meaningless at the quantum level?

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Viliam1234
Yes. Concepts can stop making sense in situations that take them apart. For
example, it makes sense to ask whether an apple is a fruit, but it doesn't
make sense to ask whether an atom inside the apple is a fruit.

Even if you'd take just one electron, its cloud is infinite. Like, really,
when people talk about things like shape of the cloud, what they mean is the
density of the cloud, or the shape that you get when you only take the region
where the density exceeds some arbitrary level.

So, from this perspective, as long as at least one electron exists in the
universe, there is no empty place in the universe. Because, with infinitesimal
probability, the electron could be anywhere.

Obviously, this is NOT what we mean by emptiness in everyday life.

(The article is okay, but its title is pure clickbait.)

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NewEntryHN
> But until such an interaction occurs, the electron has been acting like a
> wave all along.

What does that mean? Most interpretations of quantum mechanics consider the
wave function to be an abstraction to model the system, not something that is
actually tangible. Even in theories that consider it real (e.g. De Broglie-
Bohm) it acts as some sort of field, not something that actually occupies
space.

~~~
simonh
That's rally not correct. Interpretation of the double-slit experiment relies
on the electron (or photon) wave actually spanning both slits. It's not enough
to treat the electron as a point particle and the wave as being something we
pretend exists to explain it's wave-like behaviour. If the wave wasn't real,
we wouldn't see the behaviour.

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Koshkin
“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.

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

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

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muny
> Atoms exist on extremely tiny scales, just 1 ångström across...

I may be misinterpreting, but it sounds like he's saying all atoms are 1
ångström in diameter.

~~~
saagarjha
That sounds within one or two orders of magnitude?

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thayne
just one order of magnitude actually

~~~
saagarjha
One on each side, I guess.

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keymone
how much volume does a wave take up in the sea?

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okareaman
"The Medium is the Message" \-- Marshall Mcluhan

What is it about Medium that produces less than stellar articles? Because it
is a paid blogging service so people just blow out some smoke and hope to make
a little money?

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r4ltman
because it resembles an old 2003 sensibility of blogs which resonated with a
pseudo sensibility about certain types of New Yorkeresque/90s WIRED vibe.
Medium is not good, I use it right now to create synopsis for YouTube videos I
make, it's basically Myspace, which was useful for non professional and pro
musicians to just get the music out.

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efdwefwfwerf
This article is silly. 7/8th of it recapitulates what is already commonly
known. Then it doesn't go on to show a new result.

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sporkologist
> Inside your body, you aren’t mostly empty space. You’re mostly a series of
> electron clouds, all bound together by the quantum rules that govern the
> entire Universe.

So we are mostly electron clouds... and clouds by definition are mostly empty
space.

~~~
tristanstcyr
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.

~~~
Retric
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 you generally find
all the places it was not.

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mcnamaratw
Right ... except that if I want to put more _electrons_ in the same space I'm
going to have to confine them more tightly. That prediction works.

~~~
Retric
An oxygen tank where you can safely add more oxygen by increasing the pressure
is not considered full. The percentage of how empty a container is can be
considered 1 -(amount of stuff in it) / (maximum stuff possible).

~~~
mcnamaratw
I think possibly you've defined "full" two different ways. Is it maximum safe
pressure or maximum stuff possible?

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Retric
I don’t see the contradiction, Space unlike a gas tank is not going to fail.

