# Light and Blackholes

## Main Question or Discussion Point

My questions are:

If light has no mass then how can it be suck in a black hole?

What exactly is redshifting?

What do polarizing glasses do?

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DaveC426913
Gold Member
If light has no mass then how can it be suck in a black hole?
In Einstein's theory of general relativity, gravity is not a force but a curving of spacetime.

Light follows straight lines (properly called geodesics) through curved spacetime which toward the black hole.

As for 'what is' questions, well, Wiki is a good primer.

What exactly is redshifting?
http://en.wikipedia.org/wiki/Redshift

What do polarizing glasses do?
http://en.wikipedia.org/wiki/Polarization_(waves)

• Mr.maniac
Thanx but don't quite get it "what is" questions perhaps you could simplify it.

(Also that what are the children forum and is it okay for a 7th grader like me).

Assume a Badminton net tightly spread parallel to floor and above the floor.Assume it as flat space-time without force of gravitation.Now put a 1kg iron ball on it,it bends down a little to create slope around it like toilet .This is curvature of space time.
Now another smaller ball will go towards bigger ball due to curvature.

• Mr.maniac