Why is lightspeed the limit?
Why is lightspeed the limit? So why can't you travel faster than light? The faster an object travels, the more massive it becomes. As an accelerating object gains mass and thus becomes heavier, it takes more and more energy to increase its speed. It would take an infinite amount of energy to make an object reach the speed of light.
How far back in time is a light year?
Because light takes time to travel to our eyes, everything we view in the night sky has already happened. In other words, when you observe something 1 light-year away, you see it as it appeared exactly one year ago. We see the Andromeda galaxy as it appeared 2.5 million years ago.
How much time would pass on Earth if I traveled at the speed of light for a year?
At 99.99 percent of the speed of light, a craft traveling for one year would come back to a world that had aged more than 70 years in their absence. At 99.99999 percent of the speed of light, for a year, more than 2000 years would pass on Earth.