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Author Topic: What causes gravity?  (Read 7369 times)

Offline thedoc

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What causes gravity?
« on: 22/09/2014 15:30:01 »
Vincent Risi asked the Naked Scientists:
   
Given that everything travels at the speed cee (ee is equal to em cee squared) and everything bends space time from more close up to less further out relative to itself, is this what causes the gravitational effect? And we incorrectly consider gravity to be an attractive force like magnetism or static attraction.

What do you think?
« Last Edit: 22/09/2014 15:30:01 by _system »


 

Offline JohnDuffield

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Re: What causes gravity?
« Reply #1 on: 22/09/2014 16:34:14 »
Gravity is quite simple really. A concentration of energy, usually in the guise of matter in the guise of a massive planet, "conditions" the surrounding space, the effect of this diminishing with distance. See Einstein's Leyden Address for that. Then imagine you could place optical clocks al various locations throughout an equatorial slice through the Earth and surrounding space. Clocks go slower when they're lower, so when you plot all your clock rates, what you get is a plot like this: 


GNUFDL image by Johnstone, see Wikipedia 

That's a depiction of Riemann curvature. It's basically a picture of curved spacetime. But note that space isn't curved. See the Baez website and note "not the curvature of space, but of spacetime". Curved spacetime isn't curvature of space and curvature of time. It's a curvature in your plot of measurements of motion through space over time. It's a curvature of "the metric", metric being to do with measurement. Also note this on the Baez website:

"Einstein talked about the speed of light changing in his new theory.  In his 1920 book "Relativity: the special and general theory" he wrote: "... according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [...] cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity [Einstein means speed here] of propagation of light varies with position."  This difference in speeds is precisely that referred to above by ceiling and floor observers."

Those clocks I referred to are optical clocks. And they go slower when they're lower because light goes slower when it's lower. See the Shapiro quote:

"The proposed experiment was designed to verify the prediction that the speed of propagation of a light ray decreases as it passes through a region of decreasing gravitational potential."

People refer to this speed of light as the "coordinate" speed of light. The locally-measured speed of light is the speed that's constant, because of a tautology wherein we define the second and the metre using the motion of light.  Anyway, like Einstein said, light curves because the speed of light varies with position. There's a nice gif showing this on Ned Wright's deflection and delay article where you can read this: "In a very real sense, the delay experienced by light passing a massive object is responsible for the deflection of the light."



Light doesn't curve because spacetime is curved. It curves because the speed of light varies with position. It's a bit like the way a car veers when it encounters mud at the side of the road. Once you know that and you know about the wave nature of matter, it's quite easy to work out why matter falls down. Think of an electron as a wave going round and round, then simplify it to a wave going round a square path. Then imagine the horizontal sections curve down a little, like the picture below. The electron falls down. 
« Last Edit: 22/09/2014 16:40:05 by JohnDuffield »
 

Offline PmbPhy

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Re: What causes gravity?
« Reply #2 on: 22/09/2014 17:36:43 »
Quote from: thedoc
Vincent Risi asked the Naked Scientists:
   
Given that everything travels at the speed cee (ee is equal to em cee squared)
which it doesn't. This assumption is incorrect.

Quote from: thedoc
.. and everything bends space time from more close up to less further out relative to itself, is this what causes the gravitational effect?
What is "this" that you're talking about? Mass is the source of gravity. That's what you're looking for.
 

Offline yor_on

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Re: What causes gravity?
« Reply #3 on: 23/09/2014 00:21:03 »
I'm not sure what you're asking there Vincent? Maybe you can reformulate the question in other words?
 

Offline vincentrisi

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Re: What causes gravity?
« Reply #4 on: 24/09/2014 22:29:57 »
Well the Solar System is just a bunch of particles clumped together in bigger blocks. I assume that each of the individual particles must bend space time in any and all directions. The rubber mat analog for describing gravity is only on a single plane (and that kinda bugs me out).  Its mind boggling to consider that the clump of matter that makes up a human is 120 trillion times 120 trillion atoms not looking at the sub particles. I also dislike the concept of the Empire State Building would condense down to the size of one rice seed if all its known particles were scrunched up together as atoms are mostly non particle space. Is there another type of fabric we cannot detect using particles as an instrument of detection?
 

Offline yor_on

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Re: What causes gravity?
« Reply #5 on: 26/09/2014 02:09:12 »
Possible it is, depends on definitions. You have those considering a holographic universe for example. Most of everything existing can be defined as a vacuum, even a atom. And if you're into waves then we're all 'matter waves'. If you like 'fields' (which I sort of do:) then that's it, it's a 'field' :)
=

you do have something stopping this crunching down though, called the Pauli exclusion principle, then you have those 'atomic forces' too,, keeping particles (matter) in equilibrium. All of it under a normal regime, when one start to move out of this regime, as due to mass overcoming the radiative pressure inside a sun, you under some specific circumstances find the matter 'collapsing' on itself, forming a neutron star or black hole. A black hole leaves the physics we can know of, as it doesn't communicate with us, except possibly by Hawking radiation. So it becomes a singularity.

But normally we don't have any problems with it, as on Earth.
« Last Edit: 26/09/2014 02:19:14 by yor_on »
 

Offline vincentrisi

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Re: What causes gravity?
« Reply #6 on: 26/09/2014 18:08:34 »
Another thought I have is that the fusion process in stars remove the so called void portion of the atom producing dark energy and dark matter. The dark energy leaves the confines of the galaxy and causes expansion and the dark matter stay in the galaxy and forms the backbone of the galaxy. Please excuse my inability to put my ideas as like many a programmer I do not have the ability to write prose well. The original quasar monsters must have been great sources of fusion. Again this fits the concept that everything is on the move and we are all affected by cee.
 

Offline UltimateTheory

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Re: What causes gravity?
« Reply #7 on: 26/09/2014 20:30:04 »
Another thought I have is that the fusion process in stars remove the so called void portion of the atom producing dark energy and dark matter. The dark energy leaves the confines of the galaxy and causes expansion and the dark matter stay in the galaxy and forms the backbone of the galaxy. Please excuse my inability to put my ideas as like many a programmer I do not have the ability to write prose well. The original quasar monsters must have been great sources of fusion. Again this fits the concept that everything is on the move and we are all affected by cee.

You should first start from learning how to calculate energy released by fusion, to see how unreasonable is what you're saying..

Find mass of isotope in f.e.
http://en.wikipedia.org/wiki/Isotopes_of_hydrogen
(on bottom there is table of other elements)

Multiply it by 931.494 MeV (it's mass atomic unit, more precise value is here http://en.wikipedia.org/wiki/Atomic_mass_unit), subtract 0.511* quantity of electrons (Z). This will give your energy that has bare nucleus. (There should be also take care of ionization energy, but it's hard to calculate, except last electron)

Repeat the same with other sources particles.

Repeat the same with target particles.

Then energy released by fusion is E=(src1+src2)-(dst1+dst2)

If source particles have too few energy, than destination particles (while evaluating by f.e. computer algorithm), fusion won't happen, because negative energy cannot exist. It would violate energy conservation. For the same reason fusion stops at Iron, because two Irons can't fuse together (fusion energy would be negative, violating conservation).

f.e.
D+ + T+ -> He-4 + n0 + 17.6 MeV

Deuterium mass = 2.0141017778 u
Tritium mass = 3.0160492777 u
Helium-4 mass = 4.00260325415 u
(2.0141017778+3.0160492777)-4.00260325415 = 1.0275478014 u
1.0275478014 * 931.494 MeV = 957.1546116707 MeV
957.1546116707 MeV - 939.565 MeV (mass-energy of free neutron) = 17.5896116707 MeV

During fusion there are produced photons, and neutrinos (just some reactions, production of Helium-3 or 4 doesn't produce neutrinos), and these leave star, not some "dark matter and dark energy"..
 

Offline evan_au

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Re: What causes gravity?
« Reply #8 on: 26/09/2014 21:01:53 »
Quote
fusion process in stars remove the so called void portion of the atom producing dark energy and dark matter
At present we are unable to generate or detect dark energy or dark matter on Earth.
However, we have reproduced nuclear fusion on Earth, and we know what all the inputs & outputs are.
 

Offline vincentrisi

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Re: What causes gravity?
« Reply #9 on: 29/09/2014 13:22:37 »
We cannot detect Dark Matter other than by some possibly observed light bending. I am suggesting that the "void" in an atom is possibly a leviton-graviton pair which cancel out their space time bending. It take 4 hydrogen atoms to produce 1 helium atom in the star fusion process. Hydrogen and Helium are very similar in size and mass so perhaps 3 atoms worth of leviton-graviton pairs are released. The graviton-leviton are Planck sized items perhaps strings or snippets or particles. I grant that I am no good at doing physics math and this idea may be totally off the wall. But we know that we humans are apt at adopting weird idea and we should be able to reconsider when required. Another thing about Dark Matter bothers me. If the stars in the galaxy are affected by the gravity of dark matter, why are the planets not affected similarly? Is it due to the stellar winds blowing the Dark Matter out of the stars locality? The stellar system has a spinning plane but is in the centre of its sphere of influence which is quite a considerable size sphere.
 

Offline UltimateTheory

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Re: What causes gravity?
« Reply #10 on: 29/09/2014 16:11:13 »
We cannot detect Dark Matter other than by some possibly observed light bending. I am suggesting that the "void" in an atom is possibly a leviton-graviton pair which cancel out their space time bending. It take 4 hydrogen atoms to produce 1 helium atom in the star fusion process. Hydrogen and Helium are very similar in size and mass so perhaps 3 atoms worth of leviton-graviton pairs are released. The graviton-leviton are Planck sized items perhaps strings or snippets or particles.

You're making up things.
During fusion between 4 protons to He-4 there is released ~26.304 MeV energy and ~0.42 MeV neutrinos.
More detailed calcs you have in this thread
http://www.scienceforums.net/topic/85656-solar-fusion-neutrinos-and-age-of-solar-system/

It doesn't happen in the same time. First proton-proton fuses together. Then to He-3 or Tritium. Then further..

 

Offline vincentrisi

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Re: What causes gravity?
« Reply #11 on: 29/09/2014 19:40:00 »
Well I see in the hydrogen to helium lookup I did in Google that 4 hydrrogen atoms in 1 helium atom out plus energy and neutrinos. I am assuming that the so called "void space" in the atom is not being shown to be used in the process. I am suggesting that 3/4 of the so called "void space" has to go somewhere if it is not absolutely nothing. Whatever happens to it we cannot determine with our current detection means. I am absolutely happy with the calculation methods you have shown.
 

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Re: What causes gravity?
« Reply #11 on: 29/09/2014 19:40:00 »

 

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