Do you know how long it takes for light from 100 lightyears away from earth to reach us? The answer is: it depends; on where you place the clock. If it is your watch, it will take 100 years. But what if the timepiece was on the photon?
As per the ‘special theory of relativity‘, the faster an object moves, the slower the time ticks for it relative to the observer.
t = time as measured by a stationary observer
tphoton = time as measured by the travelling object
v = speed of the travelling object and
c = speed of light.
Now, substitute v = c; photon (light) travels with the speed of light! tphoton becomes zero.
In other words, light – from wherever it is – reaches you the moment it is born. But you may take one hundred years to catch it!
