Final answer:
The Twin Paradox, a concept stemming from time dilation in special relativity, describes a scenario where an astronaut traveling at relativistic speeds ages less than their Earth-bound twin. It leads to the conclusion that time experienced by individuals in motion can pass at a different rate than for those at rest, though this paradox doesn't fully account for the effects of acceleration.
Step-by-step explanation:
One of the various paradoxes related to time travel is the twin paradox. This paradox stems from the effects of time dilation as predicted by special relativity. In the twin paradox, one twin travels at relativistic speeds to a distant star and back to Earth, while the other twin remains on Earth. The traveler, upon return, is younger than the Earth-bound twin due to the time dilation experienced during the journey. Since motion is relative, from the astronaut's perspective, the spaceship would seem to be stationary and the Earth in motion.
However, the premise of the paradox is considered faulty because the traveling twin experiences acceleration, which is not accounted for in special relativity, as it only applies to non-accelerating frames of reference. Despite this, the time dilation effect is real and has been experimentally verified, although it is usually negligible at the low relative velocities we experience in our daily lives.
For example, if an astronaut were to travel to another star system at a velocity such that the Lorentz factor (γ) is 30.0, a trip that takes 2 years for the astronaut would take 60 years for those on Earth. If the astronaut was 40 when she left, she would be 42 upon her return, while her Earth-bound twin would be 100, assuming they were the same age when the astronaut left.