As Douglas Adams once wrote, “Space is big. Really big. You just won’t believe how vastly hugely mind-bogglingly big it is.” We all know that the unit of measurement used for distances in space is the light year, but think about what that means.
A light year is a distance so enormous that it takes light—that thing that moves faster than anything else in the universe—an entire year to traverse it.That means that when we look at objects in space that are really far away, like the Pillars of Creation (a formation in the Eagle Nebula), we’re really looking back in time. How is that possible?
Well, it takes light 7,000 years to reach Earth from the Eagle Nebula, and we see things by perceiving the light that bounces off of them. The light that we perceive as the Eagle Nebula is 7,000 years old by the time it reaches Earth.The implications of this glimpse into the past can be pretty weird.
For example, astronomers think that the Pillars of Creation formation was actually destroyed by a supernova about 6,000 years ago. Since it takes light so long to reach us, you can still see the pillars if you look up into the night sky, even though they no longer exist.