How does Einstein's model explain the relationship between gravity and energy?

In summary: Gravity is propagated, in Einstein's model, at the speed of light. Meaning that if there's a change in the position of the source of gravity, the rest of the universe won't feel that change until the moving curvature of spacetime catches up to the rest of the universe.In summary, according to Einstein, gravity is caused by the curvature of spacetime.
  • #1
liam.buchanan
4
0
This probably is a really basic question but nobody has ever told me the answer. Does a mass emparting a gravitational force on another mass exert any energy doing this.

Thanks,
Liam
 
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  • #2
Energy is not something that is "exerted". Force is exerted. Energy is the result of force and movement. So the answer is, if there is no movement, there is no energy. Ie, a book sitting on a table is not undergoing any changes in energy. An object in a non-circular orbit, on the other hand, is constantly exchanging energy between potential and kinetic, though the total energy is constant. Gravitational energy is conserved.
 
  • #3
Thanks russ,

I don't really understand how something can exerting force on something else without losing any energy in the process. What is it about a mass that pulls another towards it? I can't think of a better way to put this but is there any 'communication' between the two masses.
 
  • #4
liam.buchanan said:
I don't really understand how something can exerting force on something else without losing any energy in the process.
That is simply the definition of energy. It is f.d and not just f. No movement means d=0 which implies f.0=0 regardless of the amount of force.

For example, a large rock sitting on the ground is not using any energy, but it is exerting a large force on the ground (and viceversa).
 
  • #5
Thanks for you help just one more thing. I still really don't understand how gravity works is it a wave or particle that acts on from other masses? Does it tke a finite amount of time before the gravtitional force from one body acts on another? I only ask because things like light and electromagnetism have been explained to me so many times but nobody has ever told me the basics of gravity and why it happens.

Liam
 
  • #6
As far as I can recollect, gravity waves have been detected. Graviton particles haven't, but seem to still be a valid theory. Gravity itself propagates at the speed of light. I would guess, then, that gravity shares the same wave/particle duality as EM radiation. I don't know how spacetime curvature fits into that.
 
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  • #7
Thanks everyone for your help.
 
  • #8
As far as I can tell, gravity waves haven't been detected--at least not as of Oct. 2007.
 
  • #9
That's quite possibly true, Phrak. My memory isn't too reliable. I was thinking that the experiment in (Australia?) with the massive cylinders had registered something, but I could very well be mistaken.
 
  • #10
Danger said:
That's quite possibly true, Phrak. My memory isn't too reliable. I was thinking that the experiment in (Australia?) with the massive cylinders had registered something, but I could very well be mistaken.

I didn't know either. Gravity waves are spoken about with great certainly, being solutions to Einstein's field equations, so statements can be misleading. So I found this,

"[url[/URL]

and this

[PLAIN]http://www.wired.com/science/space/news/2007/10/gravitational_waves"
 
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  • #11
I think the situation is that two (neutron?) stars in orbit around one another were observed to spiral towards each other in the exact manner predicted by their emission of gravitational waves, but nobody's actually detected them in a lab before.
 
  • #12
Okay, gravity is not a force.

A force is something that is exerted upon an object, and this is the classical Newtonian answer to what gravity is.What Einstein came up with was something just a little bit different. Einstein states that the universe in which we exist, rests upon something known as spacetime. It is a 4 dimensional entity (or sometimes referred to as 3+1 dimensions, for three spatial dimensions and one temporal) which is not rigid and straight.

Newton's model of the universe rested upon a straight, non-curved universe.

Einstein's model states that the universe rests upon a curved, non-linear "spacetime".
How gravity operates is that it curves the path of objects on spacetime. So, objects are moving on spacetime, and then gravity is the curvature that alters the path that that object will travel (called, formally, a "geodesic"). Now, locally, this will be felt as a force, called the "fictitious force". All accelerated reference frames feel this force.

What causes gravity? Energy, mass, and electromagnetic fields. They are all, when boiled down, nothing more than energy. And in Einstein's world, mass is energy (hence, E = mc^2).Think of a ball sitting on a trampoline. If you're not around, that ball will roll in a straight direction. But if you jump on that trampoline, that ball will curve towards you.So, gravity is propagated, in Einstein's model, at the speed of light. Meaning that if there's a change in the position of the source of gravity, the rest of the universe won't feel that change until the moving curvature of spacetime catches up to the rest of the universe.
 

FAQ: How does Einstein's model explain the relationship between gravity and energy?

What is the relationship between energy use and gravity?

The relationship between energy use and gravity is complex and multifaceted. On a basic level, energy use refers to the consumption of resources to produce work, while gravity is the force that attracts objects with mass towards each other. However, the more energy we use, the more mass we create, which in turn increases the force of gravity. This means that our energy use can indirectly affect the strength of gravity on Earth.

Can energy use change the Earth's gravitational pull?

Yes, energy use can have an impact on the Earth's gravitational pull. As mentioned before, the more energy we use, the more mass we create, which can lead to a slight increase in the Earth's gravitational pull. Additionally, the burning of fossil fuels and other forms of energy production can release large amounts of carbon dioxide into the atmosphere, which contributes to the greenhouse effect and can alter the Earth's gravitational pull.

Does energy use create or reduce gravitational force?

It depends on the context. As mentioned earlier, energy use can indirectly increase the strength of gravity by creating more mass. However, in certain situations, such as the use of rockets or other forms of propulsion, energy can be used to reduce the effects of gravity and allow objects to escape Earth's gravitational pull.

Are there any other factors that can affect the relationship between energy use and gravity?

Yes, there are other factors that can influence the relationship between energy use and gravity. For example, the distribution of mass on Earth can also play a role in the strength of gravity. Additionally, the rotation of the Earth and its position in the solar system can also impact the gravitational pull on objects on Earth.

How does energy use on other planets affect their gravity?

The relationship between energy use and gravity on other planets is similar to that on Earth. The more energy that is used, the more mass is created, potentially leading to a slight increase in the planet's gravitational pull. However, other factors such as the planet's composition and distance from the sun can also influence its gravity, so the impact of energy use may not be as significant as it is on Earth.

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