Thermonuclear Reactions: How Does Gravity Generate Heat?

  • Thread starter maximus
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In summary, the gravitational force as a result of the mass of hydrogen in a region is what causes nuclear reactions to occur. The heat is released as a result of these reactions.
  • #1
maximus
495
4
exactly how gravity in a star can generate temperatures high enough for thermonuclear reactions? i need a straight answer this time.
 
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  • #2
It was the pressure origionally, and then the reactions which also produce heat.
 
  • #3
I'm pretty sure

that most new stars contain some Lithium and Deuterium which would fuse at much lower temperatures, and help "kindle" the reaction. Does anyone more knowledgeable about this have any comments?
 
  • #4
All that is necessary is gravitation. When the mass of Hydrogen in a region is great enough, gravitation draws it together. If the mass is great enough the force of gravity is sufficient to over come the electronic forces which sperate atoms. When this happens the nucleons are crushed close enough together to allow nuclear reactions to occur. These nuclear reactions release heat. It is not temperature which starts the reactions it is gravitational forces. The temperature is a result of the nuclear reactions.

Haven't I already answered this question?
 
  • #5
Originally posted by Integral
If the mass is great enough the force of gravity is sufficient to over come the electronic forces which sperate atoms. When this happens the nucleons are crushed close enough together to allow nuclear reactions to occur.

Nuclear rections inside Sun have nothing to do with pressure. Indeed, protons in Sun's interior (there are no atoms there) are about 2-3 times closer to each other than in liquid or solid H, still way way far for any nuclesr interaction between them to take place. What makes protons fuse is thermal motion. As H protostar shrinks its cold H atom are losing gravitational energy (because they are descending closer) thus gaining kinetic energy. While cloud is still transparent, this energy is radiated away by infrared radiation and the protostar cloud keeps collapsing (=falling on itself). But sooner or later the cloud becomes dense enough to trap most of its IR radiation inside. Since this moment temperature inside cloud starts gradually rizing as a protostar condenses under its own weight futher. When temperature reaches about 0.5-1 KeV (~10 7 K) then proton's velocities are high enough to allow to some protons occasionally gain in collisions high enough speed to roll over tall Coulomb barrier of repulsion and to fuse. At that low temperature (10 7 K fusion is still very and very seldom - once in few billion years per proton. Thus, slow (very and very slow) lazy occasional fusion takes place in proton plasma. Released energy then is trapped inside and makes long long way outside via billions of meters (usually it takes hundreds of thousand years for a photon inside Sun like star to reach the surface despite that it always moves with the speed of light), and then shines from a surface out. We then call such object "a star", because it becomes visible. Futher collapse of star is halted by the balance of thermal pressure (due to flow of fusion energy) with gravitational (hydrostatic) pressure of star's weight.

Production of energy inside stars is quite slow. Ordinary candela releases about million times more energy (per same volume) than Sun's core.
 
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  • #6
The gravitational potential energy is transferred into translational kinetic energy of the falling particles. Another name for 'translational kinetic energy' of microscopic particles is 'heat.'

If you drop a bowling ball, it gains kinetic energy as it falls. As the hydrogen atoms fall in towards a protostar, they also gain kinetic energy.

- Warren
 
  • #7
Originally posted by maximus
exactly how gravity in a star can generate temperatures high enough for thermonuclear reactions? i need a straight answer this time.

Integral, your answer makes it seem that if it were not for fusion a contracting self-gravitating mass would not heat up.

But you know it would and that the story is a bit more complicated.

The core of Jupiter would be hot even without a single event of radioactive decay or fusion ever having occurred there, essentially by the release of gravitational potential and its conversion into kinetic energy (heat, temperature).


Maximus if you drop a brick onto the ground then the brick and the ground are both slightly warmer afterwards.

Self-gravitation of a star involves enormous quantities of mass coming down vast distances. Even if it is gradual the kinetic energy is going to reach very high temps---even without fusion occurring---because so much gravitational potential energy is being given up by the matter as it moves in towards the center.

this might be a case where one could calculate a rough estimate of the temperature achieved by a self gravitating mass of some size coming together---there is a related (not directly applicable but suggestive) formula called the Virial Theorem asking to be tried here.
 
  • #8
Might I suggest that some of you read the pages in the Astronomy and Cosmology forum, Proof of the cause of gravity, near the end pages 11, 12, 13, this particular topic is, in a sense of it, being 'Hotly' debated, just that it is presently about the Earth's core...such fun.

In a star the pressure is generated by gravity, generation of pressure is a heating event, pressure alone is not, pressurization is, hence it is the stars gravity that initiates the event, and the resultant increases in heat values, further drives it, as heat, and gravity, play a dance of expansion and contraction, in opposition to each other.

The nuclear reaction (fusion) simply adds to the heating side of the event, and slowly to the mass side, through the fusion of higher mass elements. Gravity builds!
 
  • #9
Originally posted by chroot
The gravitational potential energy is transferred into translational kinetic energy of the falling particles. Another name for 'translational kinetic energy' of microscopic particles is 'heat.'

If you drop a bowling ball, it gains kinetic energy as it falls. As the hydrogen atoms fall in towards a protostar, they also gain kinetic energy.

- Warren

Exactly. It is not pressure, but change of position (protons come closer) in mutual attraction force (gravity) which makes protons move faster. Make Earth and ball come closer, and both will move faster (=gain "temperature").
 
  • #10
Originally posted by Alexander
Exactly. It is not pressure, but change of position (protons come closer) in mutual attraction force (gravity) which makes protons move faster. Make Earth and ball come closer, and both will move faster (=gain "temperature").

So the idea that temperature is actually 'Ambient Energy Pressure" (AEP) holds to the idea that it is actually pressure that is active, just that we are calling it heat, as it is a pressure of energy/EMR, AEP.

Used that term in the "Proof of Gravity" pages, AEP.
 
  • #11
Well, what we call pressure is just a change of momentum of moving particles in collisions with each other, with walls of a container (if any) and with the device measuring pressure (pressure gauge, barometer, etc). What we call temperature is average kinetic energy per particle. So, still these are different (though closely related as momentum and energy are closely related) concepts.
 
  • #12
Originally posted by Alexander
Well, what we call pressure is just a change of momentum of moving particles in collisions with each other, with walls of a container (if any) and with the device measuring pressure (pressure gauge, barometer, etc). What we call temperature is average kinetic energy per particle. So, still these are different (though closely related as momentum and energy are closely related) concepts.

I agree, but note that both arise from the same source, matter, and the energy that surrounds all matter.

Hence an interactive viewpoint of the two, as the same, (from the same source) enables the understanding of the function of the two, as a function of one thing, matter.

Is that OK?
 
  • #13
Yes, this is OK. Everything in physics is related.
 
  • #14
Mr. Robin Parsons

That is how you can use 1/r-1/2 as the calculator for the Earths increasing internal gravitational ability, with respect to it's pressurization, and it thermal energy output(s).

can you explain the 1/r-1/2 ? at first glance, it just looks like another way to write [squ]r , I suspect there's more to it than that.
 
  • #15
The 1/r-1/2 is the version of "one over the square root of r"
 
  • #16
Actually, Mr. Parsons, there is an error in your maths.

1/r-0.5 == (r-0.5)-1

== r0.5, which is the square root of r.
 
  • #17
Insert disclaimer ¤HERE¤

Originally posted by FZ+
Actually, Mr. Parsons, there is an error in your maths.

1/r-0.5 == (r-0.5)-1

== r0.5, which is the square root of r.

Thank you, I appreciate the help!

From this site...

http://www.calphysics.org/zpe.html" [Broken]

this statement...

Originally stated at the Cal Tech site

The possibility that electromagnetic zero-point energy may be involved in the production of inertial and gravitational forces opens the possibility that both inertia and gravitation might someday be controlled and manipulated. This could have a profound impact on propulsion and space travel.

Comments anyone??
 
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  • #18
Appearently, the original topic of this thread is done.

Mr. Parsons if you wish to start a new topic concerning your last post, please do.

I am locking this one.
 

1. What are thermonuclear reactions and how do they work?

Thermonuclear reactions are nuclear reactions that occur at extremely high temperatures, typically millions of degrees. These reactions involve the fusion of atomic nuclei, releasing a tremendous amount of energy. In the case of gravity generating heat, the intense gravitational force compresses the atoms, causing them to collide and fuse, releasing heat energy.

2. How does gravity play a role in generating heat through thermonuclear reactions?

Gravity is a fundamental force that attracts objects towards each other. In the case of stars, the immense gravitational force causes the atoms in the core to be tightly compressed, creating high temperatures and pressures. This allows for thermonuclear reactions to occur, generating heat and sustaining the star's energy output.

3. What types of stars undergo thermonuclear reactions?

Main sequence stars, which are the majority of stars in the universe, undergo thermonuclear reactions. This includes stars like our sun, which fuse hydrogen atoms to form helium and produce heat and light. As stars evolve, they may also undergo other types of thermonuclear reactions, such as the fusion of heavier elements in their cores.

4. How does gravity maintain the balance between heat generation and heat loss in stars?

In stars, the intense gravitational force balances out the energy released from thermonuclear reactions. This creates a state of equilibrium where the inward pull of gravity is counteracted by the outward pressure from the energy released by the thermonuclear reactions. This balance allows stars to maintain their stable size and temperature for long periods.

5. Can thermonuclear reactions occur on Earth?

While scientists are able to create thermonuclear reactions in laboratory settings, it is not feasible to recreate the extreme conditions necessary for these reactions to occur naturally on Earth. The intense temperatures and pressures required are only found in the core of stars, making it impossible to replicate on our planet.

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