Can blackholes suck in light?

[TheDrBraniac]

Do black holes suck in light due to their immense gravity? I thought light has no mass and subsequently it does not get affected by such curvatures of space-time? Also, from the Newtonian point of view, it has no weight. So how do we determine that light will get sucked in and why?

 

Basically, for light to bend, there has to be a refraction right? So, it has to travel through a new medium. So how is it possible? I've heard of this. Is it true?

[Leader Bee]

My understanding is that the light is not bent at all, but the gravity from the singularity bends spacetime - the medium which light travels through instead -Thus changing the velocity of the photons as they must follow the curvature of spacetime.

[swansont]

Light bends in a gravity field because the "flat" space is actually curved, as measured by someone far away fro the gravitational effects. So a black hole does not "suck in" light, per se — there's no extra influence on it or anything. It's just that the curvature is such that light goes in and cannot come out.

[Radical Edward]

light follows geodesics. Space is not Euclidean.

[TheDrBraniac]

Light bends in a gravity field because the "flat" space is actually curved, as measured by someone far away fro the gravitational effects. So a black hole does not "suck in" light, per se — there's no extra influence on it or anything. It's just that the curvature is such that light goes in and cannot come out.

 

Oh thanks a lot! Now I understand! The light does not bend and thus follows the curvature of space-time, entering the black hole. Thanks for your help.

[sankaet]

lol!

it doesn't SUCK light,

well light posses dual nature , it can act as a particle and as a wave, it does have mass(mass though very small, but I care to mention coz gravity is a property that mass reacts to and people tend to neglect this basic fact).

Now, when we talk about a black hole, its apparent "gravity" is so high, so so high that nothing escapes it, so it ends up absorbing all the light, reflecting back not even a single spectral band! That is the reason we call it a BLACK hole today, coz it looks black for the reason i gave above

Edited April 2, 2010 by sankaet

[StringJunky]

Light bends in a gravity field because the "flat" space is actually curved, as measured by someone far away fro the gravitational effects. So a black hole does not "suck in" light, per se — there's no extra influence on it or anything. It's just that the curvature is such that light goes in and cannot come out.

 

That's enlightened me as well..I envisioned blackhole gravity 'pulling' the photon in! As far as the photon's concerned it's still actually travelling on the same geometric line, albeit increasingly curved, and not veering off it due to extreme gravitational force as I thought before. Another lightbulb moment...cheers Swansont!

[sankaet]

and what swansont said , can be another possible explanation too as thr is so less we know about black holes so far, all these are just what people have come up with, maybe you can come up with a new theory that explains it all someday

[StringJunky]

Sankaet

 

We may not know what's beyond the Event Horizon of a Black Hole but it's effect on the local spacetime geometry around it due to its mass is well understood.

 

Einstein's explanation of gravity as curved spacetime predicts well what has been observed and measured. New data is reinforcing his concept with each passing year as far as I'm aware...an alternative explanation isn't needed.

[swansont]

lol!

it doesn't SUCK light,

well light posses dual nature , it can act as a particle and as a wave, it does have mass(mass though very small, but I care to mention coz gravity is a property that mass reacts to and people tend to neglect this basic fact).

Now, when we talk about a black hole, its apparent "gravity" is so high, so so high that nothing escapes it, so it ends up absorbing all the light, reflecting back not even a single spectral band! That is the reason we call it a BLACK hole today, coz it looks black for the reason i gave above

 

No, the photon has no mass. it's only in the Newtonian approximation that you need mass; in GR the effect is from energy density.

[Bob_for_short]

If a photon travels directly towards your black hole, it cannot miss it.