# Photons, gravity, and the bending of light.

• martinscherer
In summary, the conversation revolves around the concept of general relativity and quantum physics and its application to a scenario involving a black hole and a star. The main question is whether the light from the star would appear as a circle or fog due to the bending of light around the black hole. Reference is made to similar pictures and the concept of Hawking radiation is briefly discussed. The conversation ends with apologies for any misunderstandings due to language barriers.

#### martinscherer

Hello everyone,

first of all, english isn't my native language, so please excuse any spelling-mistakes during this post.
secondly, i am very much new to the world of physics in general, but getting more and more interested by the whole concept of general relativity and quantum physics.

thirdly, my question is infinately hard to ask (for me anyway) in an understandable way, so i hope you are able to grasp what I'm actually pondering about.

and forth, I'm sorry about the horrible Paint illustrations, I have no other tools available at this time.

So, the question(s)..

Setting:
An object with an enormous amount of mass (black hole? antimatter? blackmatter?) is positioned smack in the middle of to other object, one being a star much like our sun, the other being a point where an observer stands. Let's just call it Earth at this time.

Now, while standing on Earth observing in a straight line towards the stars "absolute" position, these questions arise in my (strange) head:

1. would not the star be visible as a circle, since the light would bend around all "sides" the black hole before it reaches earth?

..and if you go one step further..

2. would not the star be visible as just a fog, a mist, of light, since the light would be bent in an infinite amount of angles around, and away from, the black hole?

I'll try to visualize it with some drawings:

Figure 1:
Light is bent around the black hole, hitting the Earth in an infinite number of places.

Figure 2:
Light is bent around the black hole, arriving at "two" (just to make it easier) different places, making it look like the same star was to places at the same time from the observers point of view.

If anyone can shed any light (yeah, i know) to make it somewhat easier for me to grasp the concept of what is really happening, it would make my shoulders hurt a lot less.

Thank you,

Martin, Norway

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Googling "Einstein ring" also turns up some nice pictures :)

atyy said:
Googling "Einstein ring" also turns up some nice pictures :)

http://blogs.nature.com/news/blog/einsteinring.jpg [Broken]

now for the matter of figuring out why light isn't scattered everywhere, making a light-emitting-object impossible to see..?

in my mind, when in presence of a black hole, everything should appear to be everywhere, since the release of the photon from the black holes gravitational pull (time/space warp) should be arbitrary/random, and would end up just so random.

i'm making my head spin at the moment.

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martinscherer said:

Yeah, that was neat.

martinscherer said:
now for the matter of figuring out why light isn't scattered everywhere, making a light-emitting-object impossible to see..?

in my mind, when in presence of a black hole, everything should appear to be everywhere, since the release of the photon from the black holes gravitational pull (time/space warp) should be arbitrary/random, and would end up just so random.

i'm making my head spin at the moment.

As long as one doesn't get too close to a black hole, in gravitational terms it acts just like a normal star. In lensing one only needs general relativity without quantum mechanics, and light doesn't get captured and re-emitted, it just gets bent.

This thing about a black hole emitting photons randomly is probably a reference to Hawking radiation in which general relativity and quantum mechanics are considered together, and is about stuff that is captured and re-emitted.

atyy said:
Yeah, that was neat.
it was not my intention to act arrogant in any way, I'm sorry.

atyy said:
As long as one doesn't get too close to a black hole, in gravitational terms it acts just like a normal star. In lensing one only needs general relativity without quantum mechanics, and light doesn't get captured and re-emitted, it just gets bent.

This thing about a black hole emitting photons randomly is probably a reference to Hawking radiation in which general relativity and quantum mechanics are considered together, and is about stuff that is captured and re-emitted.

i will try to find some books covering those topics, thank you for the information.

atyy said:
Yeah, that was neat.

martinscherer said:
it was not my intention to act arrogant in any way, I'm sorry.

Sorry? In English "neat" is a compliment!

atyy said:
Sorry? In English "neat" is a compliment!

it just seemed sarcastic in some way.. the hassle of internet-communication + language barriers.

i'm sorry once again then :rofl:

martinscherer said:
i'm sorry once again then :rofl:

:rofl: