There is an interesting discussion on twitter why “nothing can move faster than light”. I could not resist myself from a simple explanation
I also think a similar one might have been given by Einstein himself, long time ago, so forgotten by most when they try to explain it.
How does something go faster !! by burning mass.
In case of a car to move faster and faster one has to burn the fuel, more mass in less time.
In case of light (photons) all of its energy goes into producing its kinetic energy which is therefore it’s speed. SO all it’s mass has been converted into energy that is its speed-energy.
(those who would misinterpret this line it equivalently reads as: all the energy available to the photon is in terms of it’s kinetic energy since it’s mass has to be zero)
To move at that fastest speed of Universe “c” photon has to be massless. Any more mass a photon has to carry, the mass will slow down the photon’s speed from “c” to a smaller and smaller value. That is why anything that is massive is by an “equation-proportionality” slower compared to “c” at the same energy available to a massless particle.
SO nothing can move faster than light because light particles are massless and any other kind of particle has some mass. If somehow these other things can attain the speed of light it just means they have lost all their mass into energy. They have to anyway be massless at the speed of light, “c”.
To move faster than that speed “c” where does this hypothetical particle get more mass which will be produced into energy to be used up towards speed? This particle while moving at speed “c” is already massless. The particle has to go negative in it’s mass to move faster than “c” because the energy available will then go towards speed and mass is negative so this would cause a speed larger than “c”. A negative mass means somebody else has to pay for this particle’s mass.
We don’t have such mass-banks in the world neither do we have negative mass and to add to that if this particle acquires the mass at the speed of light which will provide it more speed than the speed of light it still has to carry that mass, which will slow it down.
Therefore nothing can move faster than light.