If you traveled the speed of light for 14 years how old would someone on earth be if they were 20 when you left?

Answer 1

It would require an infinite amount of energy to propel a mass to the speed of light.

But he answer depends on what you mean. From your perspective (the traveler), the person on earth would not age at all by the end of a one way trip directly out bound. They would still appear to be 20 years old, as the signals from that person would not have aged.

If the person traveled 7 years out and 7 years back (at very close to light speed), the earth bound person would be 34, while the traveler (you) would still be the same age as when you left.

The theory that accounts for this is known as "special relativity," and if you know algebra a function to calculate relative ages is: to = ts/(1 - v2/c2)(1/2)

Where t=time, o=objective (earthbound), s=subjective (traveler), v=velocity and c=speed of light. The 1/2 exponent indicates the square root of (1-v2/c2).

Answer 2

According to the theory of relativity, time dilation would occur for the person traveling at the speed of light. They would essentially experience less time passing compared to someone on Earth. If the traveler aged around 14 years at the speed of light, the person on Earth who was 20 when they left would still be 20 years old.