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Since atoms are mostly "empty space," (Original Post) ZombieHorde Sep 2012 OP
imo yes proud patriot Sep 2012 #1
Try sticking your hand through a solid object flyingfysh Sep 2012 #2
Ouch! That was bad advice. ZombieHorde Sep 2012 #3
We only perceive a very small part of reality johnd83 Sep 2012 #4
I take comfort in that thought. nt ZombieHorde Sep 2012 #34
solid objects are objectively solid in the sense that we can't pass thru them phantom power Sep 2012 #5
I blame quantum myself intaglio Sep 2012 #6
A science assembly project Generic Other Sep 2012 #7
Perception is strictly a subjective experience. Jim__ Sep 2012 #8
I see you are predicting some of my future OPs. ZombieHorde Sep 2012 #9
One of my favorite illusions ... eppur_se_muova Sep 2012 #11
Color is definitely a mental construct... DreamGypsy Sep 2012 #18
No. That "empty" space is pervaded by fields, such as the EM field ... eppur_se_muova Sep 2012 #10
Thanks for the info. I like the magnet analogy, because it relatable. ZombieHorde Sep 2012 #12
Exactly. Igel Sep 2012 #13
That is really interesting to me. Thanks for posting. nt ZombieHorde Sep 2012 #14
It's actually electron degeneracy pressure that keeps atoms from collapsing... DreamGypsy Sep 2012 #17
Well, that's what keeps the electrons in atoms from collapsing inward ... eppur_se_muova Sep 2012 #19
DAMMIT, you beat me to the magnet analogy! Odin2005 Sep 2012 #24
When I was little, my sister always blamed me for anything that happened to her Tyrs WolfDaemon Sep 2012 #15
So naughty! ZombieHorde Sep 2012 #16
Yeah, but when she invents the oscillation overthruster, won't you look silly ! eppur_se_muova Sep 2012 #20
It will never happen Monkey-Boy! Bigbooté is watching her! Tyrs WolfDaemon Sep 2012 #21
Beat me to it. Stryder Sep 2012 #30
This message was self-deleted by its author kickysnana Sep 2012 #22
That's so mean, but hilarious! Odin2005 Sep 2012 #25
"Solidity" is an emergent phenomenon of... Odin2005 Sep 2012 #23
Sigh! No! It is an expression of Quantum Electrodynamics. longship Sep 2012 #26
Solidity is... Speck Tater Sep 2012 #27
Funny, but the analogy of repulsive parents seems to fit. nt ZombieHorde Sep 2012 #33
Sorry, but atoms are not "mostly empty". DetlefK Sep 2012 #28
By "subjective," I did not mean imaginary, I meant subjective to our size. ZombieHorde Sep 2012 #31
Then yes. DetlefK Sep 2012 #39
How do you know atoms are mostly empty space except through perception? GodlessBiker Sep 2012 #29
Well, I have not personally perceived nothing about individual atoms, only clumps of atoms. ZombieHorde Sep 2012 #32
Rutherford's gold foil experiment is how we found out that atoms are mostly empty space johnd83 Sep 2012 #36
I learned something! nt ZombieHorde Sep 2012 #35
Being that we all experience the phenomenon of solidity the same, then gtar100 Sep 2012 #37
I was thinking subjective due to our size. ZombieHorde Sep 2012 #38

flyingfysh

(1,990 posts)
2. Try sticking your hand through a solid object
Sat Sep 1, 2012, 02:37 PM
Sep 2012

What you run into is force fields operating at very small distances.

ZombieHorde

(29,047 posts)
3. Ouch! That was bad advice.
Sat Sep 1, 2012, 02:40 PM
Sep 2012

If we were somehow the size of an atom, would we be able to walk through the force fields?

intaglio

(8,170 posts)
6. I blame quantum myself
Sat Sep 1, 2012, 03:25 PM
Sep 2012

That and those damn vibrations playing fast and loose in the fields.

...And if I see that Higgs, I'll tell that interactor to go to mass.

Jim__

(14,045 posts)
8. Perception is strictly a subjective experience.
Sat Sep 1, 2012, 04:28 PM
Sep 2012

Does color exist outside of the mind? Various wavelengths of electromagnetic radiation exist, but do they exist as color outside of perception?

ZombieHorde

(29,047 posts)
9. I see you are predicting some of my future OPs.
Sat Sep 1, 2012, 05:21 PM
Sep 2012


If you print this out, and cut out squares A and B, and then put them next to each other, you will see that they are the same color.

DreamGypsy

(2,252 posts)
18. Color is definitely a mental construct...
Sat Sep 1, 2012, 10:06 PM
Sep 2012

and a developmental and cultural construct.

Our eyes detect a tiny range of the electromagnetic spectrum...about the width of one blade of grass on a football field. Why that range? Well, we just happened to be associated with a star of a type that emits most of its energy in that range. We audaciously call the range of electromagnetic radiation we perceive 'light'...so, everything else is 'dark'? We live on a planet with an atmosphere consisting mostly of nitrogen and oxygen, which scatter photons of particular frequencies in 'light' that we call 'blue' or 'blau' or 'azzurro' or 'अश्लील'. As very young children we learn that the sky is 'blue'. When we are shown 'blue' things our brains are active in particular areas in particular ways.

Our brains create colored percepts of our visual field about 10 to 12 times per second, but there is really no known experiment that can prove or disprove that two individuals per experience the same or different 'colors' in the percepts their two brains create. Whatever our brains show us can only (at least in current science) be characterized by brain activity and by the culturally defined words a person uses to describe the percepts of their brain.

eppur_se_muova

(36,227 posts)
10. No. That "empty" space is pervaded by fields, such as the EM field ...
Sat Sep 1, 2012, 06:03 PM
Sep 2012

which is the means by which atoms exert force upon one another.

Try pushing the like poles of two magnets together, to get a weak approximation of what it feels like to push two atoms together. There's no solid object between those magnets, but it feels like something is resisting closing the gap between the two.

Those fields are also interacting with electrons, which are moving about so rapidly they effectively "fill" the space about the atomic nucleus even though they are "present" at any one point only a small fraction of the time. (Not actually a good description according to quantum mechanics, but it gets the idea across.)

ZombieHorde

(29,047 posts)
12. Thanks for the info. I like the magnet analogy, because it relatable.
Sat Sep 1, 2012, 06:25 PM
Sep 2012

So, we wouldn't be able to walk through solid objects if we were atom sized, because the fields would stop us?

Igel

(35,191 posts)
13. Exactly.
Sat Sep 1, 2012, 07:22 PM
Sep 2012

Think helium and neon. They're atoms.

They stay in baloons and in lights.

Well, there are little pores in baloons that they helium can escape through, but so can oxygen and nitrogen molecules. Helium's smaller, it has an easier time. But don't confuse going through pores with passing through solid objects. The pores mean that the baloon isn't quite as solid as we think.

Electrons have an easier time. They can tunnel. But that's not a for-sure thing, it's not like they just "pass through" in any normal sense of the phrase.

It always freaks out my students when I point out how few forces there really are. All those chemical bonds? Friction? Crashing your car into a tree? Lightning? All the same.

Want a truly stupendous Nobel Prize? Find a novel force.

DreamGypsy

(2,252 posts)
17. It's actually electron degeneracy pressure that keeps atoms from collapsing...
Sat Sep 1, 2012, 08:30 PM
Sep 2012

From Wikipedia: Electron Degeneracy Pressure

Freeman Dyson showed that the imperviousness of solid matter is due to quantum degeneracy pressure rather than electrostatic repulsion as had been previously assumed.[1] Furthermore, electron degeneracy pressure prevents stars from collapsing under their own weight once nuclear fusion has ceased.


The Pauli Exclusion Principle prevents 2 electrons (spin 1/2 fermions) from occupying the same quantum state simultaneously. A consequence of this quantum mechanical principle is that electrons occupy, and are confined to, an orbital structure about the nucleus in normal matter - so the electrons do not 'fill' the space, it's just empty.

For stars of sufficient mass, gravitational collapse can overcome electron degeneracy pressure to form neutron stars, which may be prevented from further collapse by neutron degeneracy pressure (another consequence of the Fermi exclusion principle). Black holes result from the collapse of stars sufficiently massive to overcome neutron degeneracy pressure.

... but enough of that, and back to the original question of the thread...

I think the answer to whether "perception of solid objects is a subjective experience?" depends upon one's definition of solid. Quantum mechanics says that certain things that are mostly empty (~99.99% empty) behave as impervious. solid matter. Human experience of "empty" things, like an empty elevator shaft, are not as being solid. But, as Johnd83 remarked in his comment on this thread, "we (humans) perceive only a small part of reality", in fact a very tiny part of reality.

Our brains and senses have evolved to make us survive, not to make us wise. However, we do seem to have some capacity for trying to understand things that work in ways we cannot perceive and to build tools to help extend and map our perceptions. However, sometimes the universe challenges our abilities. As Richard Feynman remarked "if you think you understand quantum mechanics, then you don't understand quantum mechanics". The continual challenge to experience, to understand, and to know is what makes life fun.


eppur_se_muova

(36,227 posts)
19. Well, that's what keeps the electrons in atoms from collapsing inward ...
Sat Sep 1, 2012, 10:42 PM
Sep 2012

otherwise all atoms would be smaller than hydrogen, and there would be no Periodic Table.

But I was trying to anwer the question with the simplest picture possible -- and that meant sweeping QM under the rug.




In any case ...

Whether you're talking about an atom or a star, there are several types of forces involved, so I don't like to see any one factor given as the "cause" for their stability; it is a balance of these forces with/against each other that leads to a stable system. My impression of Dyson's work (he talked about this in one of his books, IIRC, my memory is not clear after all these years) was that he discovered that no one had ever proved fermionic matter -- and hence the Universe -- is overall stable, and he provided the proof. I would think fermionic degeneracy pressure would be part of that proof.

Ironically, we're no longer certain that the majority of the Universe consists of matter, much less fermionic matter. So in some sense, the proof went to waste.

I can't agree with the conclusion in your first para -- any single electron in any atom has, strictly speaking, non-zero density even as the distance goes to infinity -- that's reflected in the exponential part of the hydrogen-like atom wavefuntion, e-Zr/na?. As long as there is a single electron in a single atom in the Universe, no point in the Universe is completely devoid of electron density(except for nodal surfaces of the wavefunction, but that's only in a non-relativistic approximation).

I think the reason people have a hard time grasping the idea of solid matter being made up of tiny, swiftly moving particles is that they don't realize how much stronger the electrostatic force between such particles is than the forces we experience directly -- what we sense is the combined effect of many repulsive forces (between particles of like charge) and many attractive forces (between particles of opposite charge), which largely cancel each other out, except for some tiny, tiny residual imbalance due to the inhomogeneous distribution of charges in normal matter.

In a four kilogram (~1 gallon) jug of water there are

2.1 x 108Coulombs

of total electron charge. Thus, if we place two such jugs a meter apart, the electrons in one of the jugs repel those in the other jug with a force of

4.1 x 1026Newtons

This is larger than what the planet Earth would weigh if weighed on another Earth. The nuclei in one jug also repel those in the other with the same force. However, these repulsive forces are cancelled by the attraction of the electrons in jug A with the nuclei in jug B and the attraction of the nuclei in jug A with the electrons in jug B, resulting in no net force. Electromagnetic forces are tremendously stronger than gravity but cancel out so that for large bodies gravity dominates.

http://en.wikipedia.org/wiki/Fundamental_interaction#Overview


Note that the electrostatic interaction between these two jugs of water, even at close range, is immeasurably small, but that the gravitational attraction of two bodies of approximately that size is within the range of measurement -- even though gravity is ~1038 times stronger than the electrostatic force.

Tyrs WolfDaemon

(2,289 posts)
15. When I was little, my sister always blamed me for anything that happened to her
Sat Sep 1, 2012, 07:30 PM
Sep 2012

One day I got tired of it and told her a secret.
I explained that everything was made of atoms and that atoms have a lot of empty space in them. I even drew out diagrams (At least as well as a fourth grader could) to explain it to her. I then told her that if she believed hard enough and ran fast enough, she could pass through anything.

For a few days she was constantly running into the doors and walls of the house. It took that long for my parents to convince her that it wasn't possible. She told them that I explained it to her and it was all my fault.
I acted all innocent and said that she simply misunderstood what I told her.

Considering all the 'jokes' my parents would play on us, they let the tricking of my sister slide.

Response to Tyrs WolfDaemon (Reply #15)

Odin2005

(53,521 posts)
23. "Solidity" is an emergent phenomenon of...
Sun Sep 2, 2012, 01:16 AM
Sep 2012

...the electromagnetic force and the Pauli Exclusion Principle.

The same force that repels the negative ends of 2 magnets also keeps you from falling though the floor.

longship

(40,416 posts)
26. Sigh! No! It is an expression of Quantum Electrodynamics.
Sun Sep 2, 2012, 02:38 AM
Sep 2012

You cannot pass your hand through a wall (without hurting your hand somewhat severely) because the electrons in the outer shells of the atoms in your hand repel the same in the wall.

You stand on the floor of your house because the force of gravity which holds to the Earth (and to the floor) is many orders of magnitude weaker than the electrodynamic forces repelling you from falling through the floor.

Things are solid because of their compact atomic arrangement which is mostly static, held by atomic bonds that hold the material together. This also is quantum electrodynamics. As is light, as is radio, as are X-rays, as are gamma rays, as is computers, as is chemistry, as is biology. QED is almost everything we experience in the universe, except gravity.

Gravity is exceptionally weak, but over distances all the other forces of nature average out to zero.

The other two known forces of nature, the Weak and Strong nuclear forces are strangers to our daily experience, but without the first stars wouldn't shine, and without the second matter couldn't exist in a stable form. They also take part in certain exotic physics experiments to measure their attributes. The LHC at CERN comes to mind, among others. We don't experience them since they only act at very short distances, e.g., within an atom's nucleus.

This is all putting it simply. But that's my answer. I am sure some DUers could improve on it. (on edit: as I see some already have. :hi

 

Speck Tater

(10,618 posts)
27. Solidity is...
Sun Sep 2, 2012, 02:43 AM
Sep 2012

what keeps everything from happening at the same place.

Although when my kids were small it seemed like everything in the neighborhood always happened at my place. But that's probably because the other kids' parents were more repulsive. In the force field sense, not in the personal hygiene sense. I mean the other parents weren't actually repulsive, it's just that they tended to apply more force against children who congregated at their houses. Not that they actually applied physical force, mind you. but that... Oh, never mind. I'll stop now while I'm still ahead. Or at least before I get any further behind.

DetlefK

(16,423 posts)
28. Sorry, but atoms are not "mostly empty".
Sun Sep 2, 2012, 08:24 AM
Sep 2012

When encountering such tiny scales, you have to give up notions of absolutism. "Empty", "full", "here", "there" only work in classic newtonian-galileic physics.

There is the wave-particle-dualism, but in an atom electrons are best described by a wave-function. And according to Born's interpretation of the wave-function, the square of the absolute value of the wave-function is equal to the probability-density of the particle. (This equality no longer holds when the particle becomes relativistic. Works with Schroedinger-equation, but not with Dirac- and Klein-Gordon-equation.)

A spatial probability-density means, that the particle is never in one particular place, but is smeared out over several places. He is maybe "here" and maybe "there", as long as nobody is looking. Once someone "looks", the wave-function "collapses" from a multitude of possible states into one state: That one state reaches 100% probability, the rest drops to 0%.

So, in recap: Atoms are neither empty nor full. They are filled with maybes.



And concerning your question: Solidity is not subjective, you can't talk it away or ignore it at will. It's an emanation of a balance between attracting and repulsing forces that keep atoms in their place.
And the Pauli-exclusion-principle says: "The atoms of your finger-tip shalt not be in the same place as the atoms of your desk." (Well, the electrons and nucleons of the atoms, but the effect is the same.)

ZombieHorde

(29,047 posts)
31. By "subjective," I did not mean imaginary, I meant subjective to our size.
Sun Sep 2, 2012, 12:36 PM
Sep 2012

Would atom sized people be able to walk through solid walls? This was answered with a "no, the fields would stop those little people." <-- not a direct quote.

So, in recap: Atoms are neither empty nor full. They are filled with maybes.


I have heard this before, but does the "maybes" have more mass than when we "look?" If not, then it seems the spread out particles would simply be a different shape, and the atom would still be mostly empty.

DetlefK

(16,423 posts)
39. Then yes.
Mon Sep 3, 2012, 06:23 AM
Sep 2012

Let's look at it like this: An atom can tunnel through a finite repulsive potential (like a chunk of other atoms) up to a certain depth with a probability greater than zero. So, for example, the atom hitting the surface of a foil has 80% probability for reflection and 20% for tunneling through it.

Same goes for everything else: A molecule could tunnel through a foil, but as its mass is greater (let's assume same kinetic energy/temperature as the atom) the odds for reflection are higher and the odds for tunneling are lower.
And if you take a HUUUUGE bunch of molecules, like a human, then the odds for successfully tunneling through a door (without breaking it! ) are astronomically bad.

GodlessBiker

(6,314 posts)
29. How do you know atoms are mostly empty space except through perception?
Sun Sep 2, 2012, 08:25 AM
Sep 2012

Are you claiming to use perception to come to an objective truth and then using that truth to say that perception is subjective?

ZombieHorde

(29,047 posts)
32. Well, I have not personally perceived nothing about individual atoms, only clumps of atoms.
Sun Sep 2, 2012, 12:59 PM
Sep 2012

Scientists who study atoms and particles have to use perception because that is all we have to know about the world.

I was wondering if solid objects only seem solid because of our size. If solid objects were only solid because of our size, then solid objects would be strictly subjective. However, since there are fields in play, solid objects seem to be more objective than subjective.

I am starting to wonder if the words/concepts "objective" and "subjective" are misleading my thoughts on the subject.

johnd83

(593 posts)
36. Rutherford's gold foil experiment is how we found out that atoms are mostly empty space
Sun Sep 2, 2012, 02:27 PM
Sep 2012
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf

Our "perception" is based on light which is affected by the "atomic radius" rather than the nucleus itself.

gtar100

(4,192 posts)
37. Being that we all experience the phenomenon of solidity the same, then
Mon Sep 3, 2012, 02:25 AM
Sep 2012

the answer to your question would be no, that's it not a subjective experience.

ZombieHorde

(29,047 posts)
38. I was thinking subjective due to our size.
Mon Sep 3, 2012, 02:29 AM
Sep 2012

I should have communicated better in the OP.

The answer still seems to be "no" though.

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