By Mark Thompson
"Ever looked up at the night sky and wondered: What is up there? Like your ancestors before you, you would be mistaken if you thought that it's just the Earth down here and the stars up there. Instead, the night sky encompasses everything that is, or ever was, in the Universe. You see, the really wacky thing about looking up at the sky is that you are not just looking into the depths of space, but also into the depths of time.
Let me explain. Light travels at about 300,000 kilometers per second (186,000 miles per second) - that's pretty fast. In our day-to-day lives, this doesn't pose a problem; the light entering my eyes from the display in the coffee shop window takes an immeasurably small period of time to get to me. Basically, I see the display as it is right now.
However, the distances in space are so vast that it takes more time for light to reach us. We see the moon as it was 1.3 seconds ago; the sun as it was 8.3 minutes ago; the nearest star 4.2 years ago; the most distant galaxy as it was about 13.3 billion years ago. The most distant object you can see with your naked eye is the Andromeda Galaxy and even that is about 2.3 million light-years away, which means you see it as it was 2.3 million years ago. Just by looking up, you can see back in time. Crazy.
The nearest star to our own is Proxima Centuari and it lies just over 4 light-years away. Depending on the method of transport, if we were to use today's technique of gravitational slingshots around other planets, the quickest transit time would be 19,000 years!
I've only scratched the surface of the stuff that's out there, but it reminds me of a quote from Isaac Asimov who once said: "The Universe isn't stranger than we can imagine, it's stranger than we can't imagine." I've not touched on any of the more exotic objects we have discovered but it's exciting and even tantalizing to wonder what else is lurking out there, just waiting to be discovered."