I’d like to begin this post by telling a little story about myself (I’ll keep it short I promise). When I was kid, I was obsessed with astronomy. I had all the books and watched all the Discovery Channel documentaries on black holes and dark matter. But my favorite thing was going into my backyard at night and using my telescope. I’m not telling you this to brag about how I was some kid prodigy, trust me I wasn’t – I hardly understood anything about it. Either way, I was hooked.
As I got older, I upgraded to a more advanced telescope and started getting into to the abstract concepts of astronomy. One concept I specifically remember learning about was light. Light itself is so unique and has such odd properties. But the thing about light that really struck me was this – technically, when we look at something like a distant star, we are looking into the past. That concept to this day blows my mind. However, before I get ahead of myself, I want to take a step back.
The Basics of Light:
On the surface, light seems like a pretty simple thing. You point a flashlight at a wall, turn it on, and you see the light on the wall right away. Wow Owen, so cool. But, when you start introducing different factors, like distance, into the equation – things start to get a little more interesting.
Like almost everything in the universe, light takes time to travel over a distance. And when these distances get greater and greater, light takes longer to travel that distance. That’s why astronomers measure distance in space in light-years. For anyone unfamiliar with light-years, this article by Christopher Crockett does a great job of explaining the topic. Crockett discusses how light travels roughly 670 million miles per hour, which is just absurdly fast. But even at that speed, light still takes time to travel. Crockett demonstrates this concept by using the sun as an example. He states that when we look at the sun, (Please for the love of God don’t look directly at the sun) we are seeing light that is eight minutes old. This is because the distance from the Earth to the sun is roughly 93 million miles – and given the speed of light (670 million miles per hour), the light takes roughly 8 minutes to reach Earth (I’ll exclude the tedious calculations). It may not seem that impressive but let me put it into perspective for you.
Zooming Out:
Let’s pick a random star that’s multiple light years away – let’s say Wolf 359 – yeah that sounds cool. According to multiple sources, Wolf 359 is roughly 7.8 to 7.9 light-years away from Earth. That means if child Owen were to go into his backyard tonight and look at Wolf 359 through his telescope, he would see the star Wolf 359 as it was roughly 7.9 years ago. Pretty crazy, right? It’s even possible that Wolf 359 could’ve been obliterated in a catastrophic supernova five years ago, but child Owen wouldn’t know that because the light from the explosion wouldn’t have reached him yet. Phil Plait has a really cool piece on this concept over at slate.com. Alright, let’s take this a step further, beyond the reaches of our galaxy.
Suppose child Owen decides to look at the distant galaxy, Messier 104 – more commonly known as the Sombrero Galaxy. According to NASA, the Sombrero Galaxy is approximately 28 million light-years away (16,500,000,000,000,000,000,000 miles). That’s an absolutely massive distance. So when child Owen looks at this galaxy, he is seeing the galaxy as it was 28 million years ago! I’d try to put this into perspective, but I’m still trying to wrap my own head around it. It is straight up insane just how long ago that is and how great of a distance that is. Okay, let’s really blow the lid off this thing.
Imagine child Owen had the most powerful, high-tech, state-of-the-art telescope that money could buy and it could see nearly everything in the observable universe. Then, let’s say he observed MACS0647-JD, a galaxy that is roughly 13.3 billion light-years away (according to NASA). At that point, child Owen would be observing a galaxy “420 million years after the Big Bang” (NASA, 2012). 420 million years may seem fairly large, but the universe itself is 13.7 billion years old – and light from MACS0647-JD is 13.3 billion years old! A 420 million year difference on a scale that massive is a snap of the fingers.
Conclusion:
I hope I’m not the only one having an existential crisis, but either way, this concept is truly mind-boggling to think about. I believe that’s why this concept has stuck with me so long. Seeing light as a means of looking into the past just sounds absurd – but seeing it demonstrated, especially on such a large scale, really brings the idea to life. It not only gives you a perspective on the sheer size of the universe, but also a good grasp on how everything in the universe interacts together. This is the first of many discussions on space and space-related topics and I hope you all enjoyed the first installment of Deep Thoughts Blog! See you soon.
– Owen Hammer