light and gravity as distance grows

[lemur]

As I understand it, both light and gravity dissipate at the same rate with distance from the source. So I think it would be correct to say that gravity and light fade at the same rate and disappear at the same point relative to distant objects. Does this mean that there is no possibility for either gravity or light to ever be present without the other? Or can light ever extend beyond gravitation in some other way? If not, does this mean that spacetime ends at the hubble horizon for any given point in the universe? Or is there some way that gravity, light, or some other force/phenomenon could extend beyond points where expansion and relative motion have reduced light to total isolation?

[insane_alien]

the intensity of light and gravity are not related though.

 

you can have a very bright low gravity source and you can have a very dim high gravity source.

 

I think the extremes would be a (non-feeding, ie without an accretion disk) black hole which will be characterised as having an intense gravity field but zero light field.

 

The other extreme would be a gamma ray burst, average gravity field but incredibly huge light field.

 

failing that it is always possible to block the light field by an obstruction. you can't do this with gravity without some exotic possibly fictitious means.

[John Cuthber]

Lemur,

do you think turning a light bulb on or off significantly affects it's gravitational effect?

[lemur]

Lemur,

do you think turning a light bulb on or off significantly affects it's gravitational effect?

I knew someone would raise this issue. I thought of it in terms of a flashlight, but no matter. It's not relevant, though, because the issue isn't the level of significance of gravity or light, because that is subjective. Who can say that the light from a given star is sufficient to have a significant effect? It is a good point that luminosity can vary independently of gravity, or vice versa as well I suppose. But the main issue I'm raising here is whether it is possible for either light/energy or gravitation to extend beyond the other? If they diminish in intensity at the same rate, how can one extend beyond the other?

[John Cuthber]

Both properties have infinite extent (eventually).

It is, in principle, true that if you suddenly produced some mass somewhere then the light emitted or reflected by that mass would reach an observer at the same time that the effect of gravity would reach the observer.

 

Anyway I only said "significantly" to avoid pointless discussions about relativistic mass.

The light suddenly becomes billions of times brighter, and it's mass changes by an amount a billion times too small to observe.

That's what I meant by significant.

[swansont]

(Nonthermal/nonequilibrium) EM radiation can be shielded. Gravity cannot.

[DrRocket]

I knew someone would raise this issue. I thought of it in terms of a flashlight, but no matter. It's not relevant, though, because the issue isn't the level of significance of gravity or light, because that is subjective. Who can say that the light from a given star is sufficient to have a significant effect? It is a good point that luminosity can vary independently of gravity, or vice versa as well I suppose. But the main issue I'm raising here is whether it is possible for either light/energy or gravitation to extend beyond the other? If they diminish in intensity at the same rate, how can one extend beyond the other?

 

 

I'm pretty sure that the food in my refrigerator floats when I close the door.

[mississippichem]

I'm pretty sure that the food in my refrigerator floats when I close the door.

 

That phenomenon must be gnomic in nature:

 

http://blogs.scienceforums.net/capn/

[BJC]

Depends on how you define universe. If "observable universe" then EM radiation and gravity waves coexist. If a universe defined by the "gravity wave horizon" then there is a volume between the two horizons where gravity exists and EM radiation does not.

 

If you accept the Big Bang and Inflation then you will have "inflation bubbles" which are about 1000 times the "observable universe". The gravity waves would be a flat Minkowski type universe (either de Sitter or vacuum solution of FLWR) - but no EM radiation. This universe would only have EM radiation in about 0.001% of the volume.

 

Of course you could say that wherever vacuum energy exists both virtual gravitons and virtual photons exist ... but i don't think that is the question.