## How does gravity work? II

How does science work? And what's all this about quantum mechanics?

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uwot
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### Re: How does gravity work? II

Noax wrote:...your explanation of gravity seems dependent on diffraction due to that gradient.
Thank you for going to all that trouble, but I'm not sure how much tidal forces apply, as the model is based on the refraction experienced by sub-atomic particles in an hypothetical medium. I see what your saying when you consider the volume of an object, but that's not something one normally does when talking about quarks. You are right that it is more complicated than I have painted it, but I think the basic idea is sound, and one that people with little mathematical training might be able to grasp.

uwot
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### Re: How does gravity work? II

thedoc wrote:Don't brake for the stupid cat, that way it won't walk in front of you again, and that much stupidity will be removed from the gene pool.
Not a cat lover then, doc.

Noax
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### Re: How does gravity work? II

uwot wrote:
Noax wrote:...your explanation of gravity seems dependent on diffraction due to that gradient.
Thank you for going to all that trouble, but I'm not sure how much tidal forces apply, as the model is based on the refraction experienced by sub-atomic particles in an hypothetical medium. I see what your saying when you consider the volume of an object, but that's not something one normally does when talking about quarks. You are right that it is more complicated than I have painted it, but I think the basic idea is sound, and one that people with little mathematical training might be able to grasp.
It seemed that the diffraction was dependent on a gravitational gradient. If the field was completely uniform, then there would be nothing acting to bend the path of the object, just like light travelling travelling through glass: not top speed, but still straight, bending only at an angled edge where the gradient is present. My math showed the gradient to follow an inverse cubed law, not an inverse square one.
Stationary objects would not be affected by gravity in the model. No diffractions/forward-pitching from braking for the cat if you're already parked. The blog gets around that by noting that atoms are not stationary due to those electrons winging around, but those electrons account for well under one percent of the mass of the atom. Most of the mass of the atom is relatively still and immune from this diffraction effect.
Explaining physics, without needless complication, to people with limited mathematical background is a good endeavor, but if the explanation is inconsistent with observed results, more damage than good would seem to be done.

I think I overstated the mass-moment of a vertical human, which might be more like 20x (not 40x) that of our pair of 1kg weights connected with 2m of string. 20000 newtons will still be fatal, as it was for the moon(s) that got too close to Saturn, and was ripped apart into its rings.

uwot
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### Re: How does gravity work? II

Noax wrote:It seemed that the diffraction was dependent on a gravitational gradient.
I don't think it will make any difference to the argument you are making, but it's refraction, not diffraction.
Noax wrote:If the field was completely uniform, then there would be nothing acting to bend the path of the object, just like light travelling travelling through glass: not top speed, but still straight, bending only at an angled edge where the gradient is present. My math showed the gradient to follow an inverse cubed law, not an inverse square one.
The suggestion is that the field is essentially radiating from a point source. As such, the intensity diminishes according to the same inverse square law that applies to gravity, electric and magnetic fields, light and sound. It's just how stuff spreads out.
Noax wrote:Stationary objects would not be affected by gravity in the model. No diffractions/forward-pitching from braking for the cat if you're already parked. The blog gets around that by noting that atoms are not stationary due to those electrons winging around, but those electrons account for well under one percent of the mass of the atom.

Then I haven't made the point strongly enough, that gravity acts on the quarks for the same reason. I will try to make that clearer; an arrow round the nucleus might do it.
Noax wrote:Most of the mass of the atom is relatively still and immune from this diffraction effect.
It's not certain how the quarks actually move and in some models the mass of nucleons is attributed largely to the binding energy of gluons. Having said that, don't forget that mass is different to weight.
Noax wrote:Explaining physics, without needless complication, to people with limited mathematical background is a good endeavor, but if the explanation is inconsistent with observed results, more damage than good would seem to be done.
I don't think anyone will be seriously harmed. This is just a snapshot of one area of research. It's not meant to be exhaustive, but I agree that it should not be misleading, which is why I value your input.
Noax wrote:I think I overstated the mass-moment of a vertical human, which might be more like 20x (not 40x) that of our pair of 1kg weights connected with 2m of string. 20000 newtons will still be fatal, as it was for the moon(s) that got too close to Saturn, and was ripped apart into its rings.
No one's right all the time.

Noax
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### Re: How does gravity work? II

uwot wrote:
Noax wrote:It seemed that the diffraction was dependent on a gravitational gradient.
I don't think it will make any difference to the argument you are making, but it's refraction, not diffraction.
Yes, I got that wrong. Should have said refraction all along. Thanks for the correction.
The suggestion is that the field is essentially radiating from a point source. As such, the intensity diminishes according to the same inverse square law that applies to gravity, electric and magnetic fields, light and sound. It's just how stuff spreads out.
Right. Nothing in this universe can produce a uniform gravitational field. Interestingly, the flat-earth model does. If such a thing existed (infinite slab of Earth in 2D but finite thickness), I think it might produce a uniform field where you weighed the same at any altitude.
Noax wrote:Most of the mass of the atom is relatively still and immune from this diffraction effect.
It's not certain how the quarks actually move and in some models the mass of nucleons is attributed largely to the binding energy of gluons. Having said that, don't forget that mass is different to weight.
Don't think I mentioned weight much. All my examples were in freefall, where things have no weight.

Off-topic:
Not sure if you saw it since it will not show up on your notify list, but I did the math for the twin-problem in your relativity thread, and did it without any resort to general relativity. It is a far less complicated example than the one of multiple-dimension accelerated reference frames that you get by flying clock-laden aircraft around the world. I kept my example to only one spatial dimension (for math simplicity) and completely free of anything accelerating (to keep GR out of the picture).

thedoc
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### Re: How does gravity work? II

uwot wrote:
thedoc wrote:Don't brake for the stupid cat, that way it won't walk in front of you again, and that much stupidity will be removed from the gene pool.
Not a cat lover then, doc.
Not really, but then I don't brake for any animal unless it's big enough to damage my vehicle, except maybe a dog.

Dubious
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### Re: How does gravity work? II

thedoc wrote:
uwot wrote:
thedoc wrote:Don't brake for the stupid cat, that way it won't walk in front of you again, and that much stupidity will be removed from the gene pool.
Not a cat lover then, doc.
Not really, but then I don't brake for any animal unless it's big enough to damage my vehicle, except maybe a dog.
Another one of theism's grand sentiments, the inferiority of all other creatures except man. After all it's just one of many stupid biblical mandates! I'd stop for any animal or try to help when in distress and have done so in the past. I've had dogs and cats and they got along just fine; they didn't need any rules of tolerance to do so. Some were very intelligent and some less so just as with people but all had feelings just as with people.

I'd much rather dispense with any disgusting low-life theist who really do belong to another millennium than ANY cat, dog or animal alive.

***Sorry for the detour; back to gravity.

thedoc
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### Re: How does gravity work? II

How does gravity work? II

In an atmosphere, Heavy things fall and light things rise. In no atmosphere, everything falls.

thedoc
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### Re: How does gravity work? II

In a closed car, when you brake a helium filled balloon floats to the back, why? when you accelerate hard the balloon floats to the front, Why?

uwot
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### Re: How does gravity work? II

thedoc wrote:How does gravity work? II

In an atmosphere, Heavy things fall and light things rise. In no atmosphere, everything falls.
That's buoyancy, it's the same reason that some things float on water. It was Archimedes' 'Eureka!' moment, when he realised that the mass of water displaced by an object is equal to the mass of the object placed in the water for anything that doesn't just sink to the bottom*. The atmosphere is a mixture of gases, so if you can create a bubble, or balloon, filled with a particularly light gas, in practise hydrogen or helium, it will float, but it is still acted on by gravity. (Hot air is less dense than cold, basically, the atoms in hot air are moving around and bashing into each other more, so they take up more room.)

*The story is that Archimedes had been given a crown by the king of Syracuse. He suspected that the goldsmith had conned him by mixing the gold with silver, much cheaper, but also much lighter. Of course, both silver and gold sink, but the trick is to balance the crown in air with pure gold. If you then compare the crown and gold in water, if they no longer balance, you've been ripped off.

uwot
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### Re: How does gravity work? II

thedoc wrote:In a closed car, when you brake a helium filled balloon floats to the back, why? when you accelerate hard the balloon floats to the front, Why?
Had to think about this one. I don't really know, but I guess it's to do with air pressure. As you are moving forward, air is forced into the cabin from the front. When you brake, this effect is reduced and the air pressure drops, essentially, the air escapes by the same way, creating a forward current, but don't hold me to that.

thedoc
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### Re: How does gravity work? II

uwot wrote:
thedoc wrote:In a closed car, when you brake a helium filled balloon floats to the back, why? when you accelerate hard the balloon floats to the front, Why?
Had to think about this one. I don't really know, but I guess it's to do with air pressure. As you are moving forward, air is forced into the cabin from the front. When you brake, this effect is reduced and the air pressure drops, essentially, the air escapes by the same way, creating a forward current, but don't hold me to that.
I made the condition of a closed car with the assumption that no air would be escaping. In a car that is moving at a steady speed no air is moving inside the car, as it is all moving along with the car, just as the atmosphere is moving with the Earth as it orbits the Sun and spins on it's axis. When the car accelerates the inertia of the air moves it to the back of the cabin raising the pressure there and lowering it toward the front, thus the balloon moves toward the lower air pressure, and the opposite occurs during braking. So the movement is due to inertia, and air pressure, the assumption is that no air is escaping or entering the cabin.

uwot
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### Re: How does gravity work? II

thedoc wrote:I made the condition of a closed car with the assumption that no air would be escaping. In a car that is moving at a steady speed no air is moving inside the car, as it is all moving along with the car, just as the atmosphere is moving with the Earth as it orbits the Sun and spins on it's axis. When the car accelerates the inertia of the air moves it to the back of the cabin raising the pressure there and lowering it toward the front, thus the balloon moves toward the lower air pressure, and the opposite occurs during braking. So the movement is due to inertia, and air pressure, the assumption is that no air is escaping or entering the cabin.
Makes sense. Thank you, I've learnt something new.

thedoc
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Joined: Thu Aug 30, 2012 4:18 pm

### Re: How does gravity work? II

uwot wrote:
thedoc wrote:How does gravity work? II

In an atmosphere, Heavy things fall and light things rise. In no atmosphere, everything falls.
That's buoyancy, it's the same reason that some things float on water. It was Archimedes' 'Eureka!' moment, when he realised that the mass of water displaced by an object is equal to the mass of the object placed in the water for anything that doesn't just sink to the bottom*. The atmosphere is a mixture of gases, so if you can create a bubble, or balloon, filled with a particularly light gas, in practise hydrogen or helium, it will float, but it is still acted on by gravity. (Hot air is less dense than cold, basically, the atoms in hot air are moving around and bashing into each other more, so they take up more room.)

*The story is that Archimedes had been given a crown by the king of Syracuse. He suspected that the goldsmith had conned him by mixing the gold with silver, much cheaper, but also much lighter. Of course, both silver and gold sink, but the trick is to balance the crown in air with pure gold. If you then compare the crown and gold in water, if they no longer balance, you've been ripped off.
I believe the goldsmith was executed for his fraud.

Noax
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### Re: How does gravity work? II

thedoc wrote:
uwot wrote:
thedoc wrote:I believe the goldsmith was executed for his fraud.
I heard that the crown was found to be pure gold, and no execution. Same story, but different ending. Was I told the story wrong? Too PC of a school to describe an execution, but it was OK to give us an image of Archimedes running naked down the road?

The balloon in the car thing is also buoyancy. It is an illustration of one of the initial thought experiments for general relativity. Einstein stated that there was no local experiment that could differentiate gravity from acceleration. Hence, a sealed/soundproofed car with the windows painted black and the balloon coming to the windshield: Is the car accelerating or it just parked pointing uphill? Einstein said you can't tell the difference.

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