# What does light look like?

1. Oct 26, 2010

### SMG75

1. The problem statement, all variables and given/known data
What would light look like if you could ride alongside of it?

2. Relevant equations
None

3. The attempt at a solution
I am aware of wave-particle duality. I am just having some trouble coming up with a visual of this...

2. Oct 26, 2010

### fss

...probably because it's not a meaningful question...?

3. Oct 26, 2010

### srmeier

To have a visual representation of light, light would have to reflect off light and hit your eye. This doesn't occur in reality as far as I'm aware.

4. Oct 26, 2010

### SMG75

I understand that it's not a meaningful question, but it is something I need to come up with for class. Any ideas?

5. Oct 26, 2010

### fss

Come up with whatever you want; it's not like anyone can prove you wrong. The entire premise is ridiculous.

6. Oct 26, 2010

### venkatg

To me there is no ridiculous question.

Light can behave as a wave one time and a particle other time depending upon how you probe it. If you observe its interaction with electrons, it would behave like a particle (photon). If you allow coherent light source to pass through multiple narrow slits placed close together, it would behave like a wave (interference patterns). So to probe light you have to interact with it. A photon does not have internal structure and hence no mass. When it moves from one point in space to another, it does in no time. So essentially a photon takes all possible paths. From a photon's perspective time does not flow. But the space and time are not independant entities. they are connected by a metric that limits the speed at which 2 events can be causally connected. Light travels at that cosmic speed.

So to answer your question, the metric of space and time does not change for inertial observers and so you will see the light speeding away at the cosmic speed no matter how fast you run along with it. This also means that light moves at an aboslute speed! But this creates paradoxes... which is resolved by the special theory of relativity

7. Oct 26, 2010

### sungod

This is the question Einstein asked himself at 16 years old. He concluded that the light would "look like" a stationary, oscillating e-m field - impossible according to Maxwell's equations. Yes, he apparently was familiar with Maxwell's equations at 16! He finally resolved the contradiction by assuming (postulating) that it was impossible to travel at the speed of light. This, and the other postulate, led to Special Relativity