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Wizard
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Wizard
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April 3rd, 2019 at 4:36:10 AM permalink
Quote: gordonm888

(Simplified) The strong force is a very short-range force. Before you could get the two protons close enough to feel the strong force, they would be repelled by the electromagnetic force. However, the strong force can hold together a proton and a neutron.



In a heavy element like Iodine, you would have a whole bunch of protons and neutrons packed into the nucleus. If you have a bunch of black and white balls in a bag, there would be some whites touching whites and blacks touching blacks. So, while I buy that neutrons help space apart the protons, aren't they still touching each other in places?
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unJon
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April 3rd, 2019 at 8:56:33 AM permalink
Quote: Wizard

In a heavy element like Iodine, you would have a whole bunch of protons and neutrons packed into the nucleus. If you have a bunch of black and white balls in a bag, there would be some whites touching whites and blacks touching blacks. So, while I buy that neutrons help space apart the protons, aren't they still touching each other in places?



That’s not a good analogy. Here’s a better (but still imperfect one): the white balls and black balls are all strongly attracted to each other, but the black balls (protons) all repel other black balls (like two north poles on a magnet). In that circumstance you can visualize a structure where the white balls are the “glue” and black balls don’t touch.

It’s still not “correct” but gives you a better idea.
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Wizard
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April 3rd, 2019 at 9:38:22 AM permalink
Quote: unJon

That’s not a good analogy. Here’s a better (but still imperfect one): the white balls and black balls are all strongly attracted to each other, but the black balls (protons) all repel other black balls (like two north poles on a magnet). In that circumstance you can visualize a structure where the white balls are the “glue” and black balls don’t touch.

It’s still not “correct” but gives you a better idea.



The only way I can visualize the black balls never touching each other is if they alternated in line with the white balls or there were are a significantly greater number of white balls, which isn't the case in a nucleus.
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unJon
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April 3rd, 2019 at 11:19:16 AM permalink
Quote: Wizard

The only way I can visualize the black balls never touching each other is if they alternated in line with the white balls or there were are a significantly greater number of white balls, which isn't the case in a nucleus.

Why are you thinking in 2D. See the pic on the Wikipedia page. Again this isn’t correct, but it’s less incorrect than your visualization

https://en.m.wikipedia.org/wiki/Atomic_nucleus
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Wizard
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April 3rd, 2019 at 11:50:30 AM permalink
Quote: unJon

Why are you thinking in 2D. See the pic on the Wikipedia page. Again this isn’t correct, but it’s less incorrect than your visualization



I wasn't.

What may help others struggling with this is that the heavy elements have more neutrons than protons, which I had forgotten.

Uranium, for example, has 92 protons and an average of 146.03 neutrons. I suppose there are certain arrangements where no protons touch.

source
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Ayecarumba
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April 3rd, 2019 at 12:07:05 PM permalink
I'm no nuclear physicist, but I'm pretty sure the Wizard is right regarding the Strong force having more of an influence than the electrostatic positive charge. Isn't the disruption of those bonds why nuclear bombs go boom?

Edit: Add source:
Quote: Wikipedia "Atomic nucleus"

...The nuclear force is highly attractive at the distance of typical nucleon separation, and this overwhelms the repulsion between protons due to the electromagnetic force, thus allowing nuclei to exist. However, the residual strong force has a limited range because it decays quickly with distance (see Yukawa potential); thus only nuclei smaller than a certain size can be completely stable...

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unJon
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April 3rd, 2019 at 12:13:07 PM permalink
Quote: Wizard

I wasn't.

What may help others struggling with this is that the heavy elements have more neutrons than protons, which I had forgotten.

Uranium, for example, has 92 protons and an average of 146.03 neutrons. I suppose there are certain arrangements where no protons touch.

source



Yes good point about more neutrons. But the visualization works even without that. Let me try it as a math problem. You have one white sphere and several black spheres all of equal radius. What is the most number of black spheres you can have touching the white sphere without any black sphere touching another black sphere?

In 2D with circles instead of spheres, the answer is 5 black circles around a center white circle.

@ayecarumba - yes the strong force is by far the strongest force, but only at very small distances.
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Ayecarumba
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April 3rd, 2019 at 12:24:26 PM permalink
Quote: unJon

Quote: Wizard

I wasn't.

What may help others struggling with this is that the heavy elements have more neutrons than protons, which I had forgotten.

Uranium, for example, has 92 protons and an average of 146.03 neutrons. I suppose there are certain arrangements where no protons touch.

source



Yes good point about more neutrons. But the visualization works even without that. Let me try it as a math problem. You have one white sphere and several black spheres all of equal radius. What is the most number of black spheres you can have touching the white sphere without any black sphere touching another black sphere?

In 2D with circles instead of spheres, the answer is 5 black circles around a center white circle.

@ayecarumba - yes the strong force is by far the strongest force, but only at very small distances.



It is important to remember that protons and neutrons aren't solid like billiard balls that can only touch on one point. They are more like soap bubbles that change "shape" when near each other.

check out the video here
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unJon
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April 3rd, 2019 at 4:18:45 PM permalink
Quote: Ayecarumba

Quote: unJon

Quote: Wizard

I wasn't.

What may help others struggling with this is that the heavy elements have more neutrons than protons, which I had forgotten.

Uranium, for example, has 92 protons and an average of 146.03 neutrons. I suppose there are certain arrangements where no protons touch.

source



Yes good point about more neutrons. But the visualization works even without that. Let me try it as a math problem. You have one white sphere and several black spheres all of equal radius. What is the most number of black spheres you can have touching the white sphere without any black sphere touching another black sphere?

In 2D with circles instead of spheres, the answer is 5 black circles around a center white circle.

@ayecarumba - yes the strong force is by far the strongest force, but only at very small distances.



It is important to remember that protons and neutrons aren't solid like billiard balls that can only touch on one point. They are more like soap bubbles that change "shape" when near each other.

check out the video here

IIRC, under the Standard Model they are point particles so couldn’t ever really touch anything.

In any event this was a visualization exercise that we all agreed wasn’t correct.

Cool video.
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Wizard
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April 3rd, 2019 at 4:35:24 PM permalink
Quote: unJon

Let me try it as a math problem. You have one white sphere and several black spheres all of equal radius. What is the most number of black spheres you can have touching the white sphere without any black sphere touching another black sphere?



Good question -- Let me think about it. I have hundreds of golf balls which may help.
It's not whether you win or lose; it's whether or not you had a good bet.

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