# C not constant ?

1. Apr 28, 2003

### Moogle

Since the gravity of a black hole affects light, does a baem of light accelerate when it nears a black hole ? Just wondering.

2. Apr 28, 2003

### chroot

Staff Emeritus
It doesn't change speed -- but it changes direction.

Physicists refer to any change in the velocity vector an acceleration, though -- so yes, the light does accelerate. Its velocity vector does not change in magnitude however, which means the light does not change speed.

- Warren

3. Apr 28, 2003

### dr-dock

Re: Re: C not constant ?

nonsense.
when direction changes there are all three: normal, tangentional and torsional changes of the vector.
and how exactly do you find light to be cabable of traveling?
is it in a sense light changes position?
in my room now the lights are on.where do i find the light now?
how do i ensure the light after awhile has gone from there?

finally can you put light on bread and eat it?

4. Apr 28, 2003

dock, what the heck?? Are you capable of making sensible posts at all anymore, and even of understanding extremely basic vector mechanics?

5. Apr 28, 2003

Staff Emeritus
A light beam always follow the shortest path through the vacuum. If space is flat that path is a straight line. But near a gravitational source it is a curved line, called a geodesic. Light follows it.

The gravitational potential will not acclerate the ligh, but it will change its frequency. For light, momentum is exhibited as frequency according to the equation momentum equals planck's constant times frequency. p=h[nu].

6. Apr 28, 2003

### marcus

Or E = h &nu;

and p = E/c = h&nu; /c

7. Apr 28, 2003

### marcus

that thing that looks like a vee is supposed to be a nu.

I used & nu ; (without the spaces)

is there another way to get nu?

Let's try [ nu ] (w/o the spacing)

E = h[nu]

E/c = h[nu]/c

8. Apr 30, 2003

### Ben-CS

Yes, but that is a topic for another thread.