# Can something exceed the speed of light?

## Main Question or Discussion Point

How was the speed of light proved to be 3*10^8...also How it was proved that nothing can exceed the speed of light?...and what will happen if something moves under the effect of certain force with constant acceleration in space i.e the net force on it is constant and not equal zero...is that possible and will that body at certain instant exceed the speed of light ?and if so what will happen....another question, does my absolute velocity in the universe exceed the speed of light i.e I move with 100 km/h the earth moved with x km/h and the galaxy and so on ...........
Thanks for consideration

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Hootenanny
Staff Emeritus
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How was the speed of light proved to be 3*10^8
Using Maxwell's equations & the wave equation.
...also How it was proved that nothing can exceed the speed of light?
It is a consequence of one of the postulates of relativity.
...and what will happen if something moves under the effect of certain force with constant acceleration in space i.e the net force on it is constant and not equal zero...is that possible and will that body at certain instant exceed the speed of light ?
No since the body's inertial mass increases with velocity (http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html).

Last edited:
Doc Al
Mentor
How was the speed of light proved to be 3*10^8...
It was first deduced, then measured. (Given our modern understanding, it is now defined to be a certain speed.)
also How it was proved that nothing can exceed the speed of light?...
It's a consequence of relativity.
and what will happen if something moves under the effect of certain force with constant acceleration in space i.e the net force on it is constant and not equal zero...is that possible and will that body at certain instant exceed the speed of light ?and if so what will happen
While the force and acceleration will appear constant as measured by observers moving with the body, it will not appear constant to others. The speed of the body with respect to any other object will never reach light speed.
....another question, does my absolute velocity in the universe exceed the speed of light i.e I move with 100 km/h the earth moved with x km/h and the galaxy and so on ...........
There's no "absolute" velocity; all velocities are relative. No, your speed with respect to anything will be less that the speed of light.

We have to careful about whether we are talking about the group or the phase velocity. This is where the confusion comes in when people say they made light travel faster than the speed of light, they mean the group (or is it phase?) velocity of light through a specific medium. Nothing can travel faster than light in a vacuum, light can exceed its group (phase?) velocity in a medium like water, and give off pretty blue radiation.

I hope someone else can explain this better than me.

another question, does my absolute velocity in the universe exceed the speed of light i.e I move with 100 km/h the earth moved with x km/h and the galaxy and so on ...........
Thanks for consideration
What are the speeds of these objects being measured with respect to?