# If light travels at approximately 5.9 trillion miles per year, is it safe to assume that objects and events assumed to be many light years away may have been transformed, converted  or evolved into something else and is no longer there? If some unimaginably huge event that would have given off such energy that it would have delivered sufficient energy such that it be detectable on earth but the event transpired 11,000 light years away would it not take 11,000 years to arrive here?

Q:

If light travels at approximately 5.9 trillion miles per year, is it safe to assume that objects and events that are many many light years away may have been transformed into something else and are no longer there? If some event transpired 11,000 light-years away, would the light from it take 11,000 years to arrive here?

A:

In short, yes, it is possible that light that is visible in the night sky on Earth originated in stars that no longer exist. The speed of light limits the rate at which light information from astral objects can reach Earth. Perhaps the most illustrative example of this time limit is the sun. It takes about eight minutes and twenty seconds, on average, for light from the sun to reach Earth. If the sun were to suddenly disappear, this means that it would still be visible from Earth for another eight minutes and twenty seconds before it became apparent that it was gone.

When we see objects in the night sky, we are actually looking at photons emitted from them (stars) or reflected off them (planets and asteroids). Because these photons can travel no faster than the speed of light, what you see in the night sky is a "snapshot" of those rays of light at the time that they were emitted or reflected. In other words, yes, light from an event that hypothetically took place 11,000 light-years away from Earth--that is, assuming that it was able to reach Earth in the first place--would indeed take 11,000 years to reach here, since light takes one year to travel one light-year.