(The Pillars of Creation, located in the eagle nebula.)
As the awesome Douglas Adams wrote, “Space is big. Really big. You just won’t believe how mind-bogglingly big it is.”
Everyone knows that the unit to measure distance in space is the light year.
Have you ever considered what that actually means though? Just one light year is a distance so incredibly large that it takes a beam of light – light, that nothing can in theory travel faster than, in the entire universe—a whole year to traverse.
Which means that when you gaze upon the many objects in space that are far away, you’re really peeking back in time. Is that possible? Well, it is and here is how. Lets take the Pillars of Creation (a formation in the eagle nebula) for example. It takes light 7,000 years to finally reach earth from this particular formation.
Astronomers believe that the Pillars of Creation could have been destroyed by a supernova around 6,000 years ago.
So since the light from the Pillars takes such a long time to get back to earth. We see the formation today as it was 7000 years ago, even though they may no longer exist.
It is because light takes so long to get back to us, you are still capable of seeing these completely humbling objects in the night sky; even though they no longer exist.
To read more about how it’s possible to look back in time in order to observe the universe check out: http://www.space.com/4497-universe-history.html