What is stress-energy and how does it differ from other forms of energy?

[taylordnz]

im basing my assumption that it is no, because light is energy acting as aparticle and because it creates no mass it has no gaviational attraction on other particles, i need to find proof if my assumption is correct?

 

[franznietzsche]

im basing my assumption that it is no, because light is energy acting as aparticle and because it creates no mass it has no gaviational attraction on other particles, i need to find proof if my assumption is correct?

Not in this forum it doesnt. In the relativity forum it does though.

 

[selfAdjoint]

In general relativity energy, including light energy, gravitates. General Relativity is usually classed as a "classical" theory, in the sense that it is not quantum.

 

[turin]

Allusion to light is unnecessary. If you are already willing to accept that something that "creates no mass has no gravitational attraction on other particles," then that seems to answer the original question (albeit incorrectly), as far as assumptions go. However, there are a lot of people around here who would like to say that light (a.k.a. a photon) does have (relativistic) mass, and they are not strictly incorrect. Bottom line:

Energy gravitates.

 

[franznietzsche]

Allusion to light is unnecessary. If you are already willing to accept that something that "creates no mass has no gravitational attraction on other particles," then that seems to answer the original question (albeit incorrectly), as far as assumptions go. However, there are a lot of people around here who would like to say that light (a.k.a. a photon) does have (relativistic) mass, and they are not strictly incorrect. Bottom line:

Energy gravitates.

Well in Newtonian theory energy does not gravitate. In Einstein's filed equation though, it is the stress-energy tensor that determines the einstein tensor (thus the ricci tensor and thus the curvature tensor), and so all forms of stress-energy gravitate (including gravity itself apparently) So energy in relativity does gravitate, not in Newtonian gravity though.

 

[taylordnz]

so light floculates and gathers inside itself due to the gravity it creates?

 

[Janitor]

so light *********s and gathers inside itself

HUSH YOUR MOUTH!

 

[turin]

so light floculates and gathers inside itself due to the gravity it creates?

I have only considered the ideal infinitesimally thin ray of light, but that doesn't help answer the above question. If you consider two such rays of light, then I'm pretty sure that they would tend towards each other, but I'm not positive, and that may not be a satisfactory consideration to you. As far as a finite volume of light traveling through space or something, I don't know. The theory says that the electromagnetic field causes spacetime curvature, but the one time I tried to calculate the curvature caused by electromagnetism, I had to abandon the effort because it took too much of my time. Maybe someone has done some kind of numerical calculation and published it.

 

[franznietzsche]

so light floculates and gathers inside itself due to the gravity it creates?

does a tennis ball? no, it keeps moving. You'd have to create a black hole from a photon gas in order to do what you describe, so no. But it does curve spacetime.

 

[franznietzsche]

I have only considered the ideal infinitesimally thin ray of light, but that doesn't help answer the above question. If you consider two such rays of light, then I'm pretty sure that they would tend towards each other, but I'm not positive, and that may not be a satisfactory consideration to you. As far as a finite volume of light traveling through space or something, I don't know. The theory says that the electromagnetic field causes spacetime curvature, but the one time I tried to calculate the curvature caused by electromagnetism, I had to abandon the effort because it took too much of my time. Maybe someone has done some kind of numerical calculation and published it.

i wouldn't try thinking in terms of the elctromagnetic field, rather think about the energy of a photon as a mass, it should fit into the equations more easily.

of course there was also the Kaluza solution of Einstein's equations in 5 dimensions which produced maxwell's equations, indicating that the two must be related, though little attention seems to have been payed to this result until some recent attention in string theory i believe.

 

[Dors_Venabili]

Light will not create gravity, but particles of finite mass in (accelerative and angular velocity) gravitational fields will gradually convert their mass into light energy (photons) via relativistic radiation. This is the unforseen connection between gravitational and nuclear forces.

Zarko

 

[Stingray]

i wouldn't try thinking in terms of the elctromagnetic field, rather think about the energy of a photon as a mass, it should fit into the equations more easily.

GR is a classical theory, and light is classically a wave. The problem is actually solved approximately in Tolman's old book (1934, but reprinted by Dover), and I'm sure there are many other treatments, but I don't know them off hand.

It turns out that at lowest order, light generates twice as much gravity as an equivalent amount of mass, although this statement is really quite vague.

 

[franznietzsche]

light is classically a wave.

Tell that to Newton.

 

[taylordnz]

ill revise my question again, if you had enough light condensed into each other would it create a small but minute gravity field?

 

[Stingray]

ill revise my question again, if you had enough light condensed into each other would it create a small but minute gravity field?

Yes it does. Most people here have said that. The effect is extremely small though.

 

[Dors_Venabili]

It's actually the other way around. Photons DO NOT create gravitational fields. Rather, massive objects in angular velocity fields will gradually lose their mass to photonic energy radiation so long as they remain in the field. However, to be able to experimentally detect these effects requires either incredibly massive objects or extremely high rotational frequencies - or preferably - both.

 

[pallidin]

It's actually the other way around. Photons DO NOT create gravitational fields. Rather, massive objects in angular velocity fields will gradually lose their mass to photonic energy radiation so long as they remain in the field. However, to be able to experimentally detect these effects requires either incredibly massive objects or extremely high rotational frequencies - or preferably - both.

So, as you stated, should it be clear that "Photons DO NOT create gravitational fields" ?
Curious. Surely there is a relationship. After all, if mass is reduced by photonic emission(in your example) could it not be conjectured that mass is increased by photonic absorption under the SAME circumstance?
Don't know myself, just asking.

 

[Stingray]

Dors is talking about his own ideas.

The generally accepted view is the one I gave. I'm fairly sure that the the gravitational effect of radiation is observed in the CMB. It certainly comes up all throughout the equations describing it, although I'm not up on the latest experimental results.

 

[Michael777]

Don’t they say that the light is curved in heavy gravitational fields? Is that Mr. Einstein- Mileva Maric theory ? If Einstein - Maric theory is correct , then E=mc^2. Light is a form of energy, therefore being linked to a mass, therefore it should gravitate.
I guess recently they validated again Einstein – Maric theory; that story about light being bent by a strong gravitational field .

Have fun,
Michael

 

[franznietzsche]

Light creates its own gravitational field, otherwise it could not be affected by gravity, which observations have shown that it is. The effect is minute, but all forms of stress-energy gravtitate, and light is included.

 

[Chi Meson]

Franz:

For help in understanding "stress-energy," could you give an example of energy that is NOT "stress-energy"? TIA