>>10486762You got it correctly for the case of the photon yes.
In relativity, an important concept is the Lorentz factor, which essentially is what keeps the speed of light constant in all frames of reference. It is given by
The figure shows the value of for different speeds.
If your speed is negligible compared to the speed of light, as in everyday life, and everything works just like Newton tells us. If however your speed is a significant fraction of the speed of light, the value of increases.
This brings us to the concept of time dilation and length contraction, they are basically the same thing but apply to different observers.
If you are traveling at close to the speed of light, you experience length contraction in the direction in which you move. Every distance is effectively divided by
If I were to look at you as you flew past me, and more specifically at a watch you held in your hand, I would see that each tick of a second takes a factor longer than it does for a clock I hold in my own hand.
At the speed of light, the Lorentz factor is infinite, explaining what the photon experiences. At any speed lower than c, the Lorentz factor is finite but can be arbitrarily large. For example, there is a certain speed which, if you achieved it, would make the Andromeda galaxy be located 1 meter away from you.
This also explains why you can never reach the speed of light. The Lorentz factor applies to energy as well. It would require an infinite amount of energy to accelerate any object with mass to the speed of light.