 Space is big like really big like think of the biggest thing that you can think of and it's even bigger than that So how do a scientist take all of this? Bigness and put it into something that you can comprehend Well, that's where the light here comes in handy and what's interesting is that with astronomy You can actually do a little bit of time travel without having to hop into your DeLorean This is your space pod for May 1st 2015 The speed of light is based on extremely precise measurements of how fast a beam of light Moves one meter through a vacuum turns out. That's about two hundred and ninety nine thousand seven hundred and ninety two kilometers per second or about one hundred and eighty six thousand three hundred and twenty two miles for our imperial unit friends light takes approximately one two hundred and ninety nine millionth seven hundred and ninety two thousand four Hundred and fifty eighths of a second to travel one meter This is ridiculously fast for example if I were to run around the earth at this speed I Could run around the earth eight times in one second And if I wanted to get to the moon it would take me only about 1.3 seconds to traverse the 384 thousand kilometers between the earth and the moon Light years are a unit that allows us to measure both distance and the approximate time It's taken light to travel from an object to us We like to use this unit because the distances are vast between objects outside of our solar system And that can make it very difficult to comprehend for those of you curious to just how far light travels in a single year It's about nine point four six trillion kilometers. That's going to be quite a few tanks of gas For some context Voyager one is currently the fastest of our probes headed out of the solar system And at its current speed of 17 kilometers per second it would take nearly 17,500 years to travel one light year so the closest star to us Proxima Centauri is about 40 trillion kilometers away from earth But that's a lot of distance to wrap your head around so we use light years as our measurement Which comes out to about four point two four light years away This way when we talk about the furthest visible objects away that we can currently see with the Hubble space telescope We tell you that they're in excess of 13 billion light years away as opposed to the billions trillions Quadrillions and many more numbers of miles followed by a ridiculous amount of zeros away Now we also can use the speed of light as a measure for time For example going back to Proxima Centauri at four point two four light years away The light you see today has taken four years and just about three months to traverse the vast Distance between our stellar neighbor. This means that the light that you're seeing today on May 1st 2015 actually left Proxima Centauri sometime around January 2011 and the further you look out the further back in time you see the Orion Nebula is about 1,600 light years away from the earth so that means that the light you're seeing from it today left the Orion Nebula back around 400 AD the mighty Andromeda galaxy it's 2.5 million light years away Meaning it's light left 2.5 million years ago. So what about these distant objects we're seeing over 13 billion light years away Well, that light has taken 13 billion years to reach us it left those objects over 9 billion years before our own solar system began to form So can we apply this even to human scales? We can actually I've got my dad and my dogs Missy and Asuki out here on our lawn. They're about one meter away from me So does that mean that I'm seeing them right now? Well the answer to that is no I'm not I'm seeing them as they were one 299 millionth of a second ago turns out no matter where you look anywhere in the universe Even with your own two eyes. You're looking back in time Thanks for watching this space pod. I'm Jared head. Don't forget to subscribe Comment on social media and we do have a patreon campaign and if you donate to us we can continue to bring you Fascinating science at the speed of light. So thanks for watching and keep exploring