Let's talk about Lookback Time

Ok. Time to shake things up. As we all know, the quality of this blog has rapidly gone downhill, so the content around here is going to be changed. Instead of rambling on self-centeredly about my own life, I will enlighten you all with the wonderful knowledge I am daily acquiring at school. And no, there is no sarcasm here. I really like most of my classes, as is evidenced by the fact that I attend lectures. My two favorites are Astronomy and Indian History, and Immunology is rather engaging as well. And now that I have decided to share my knowledge of these three subjects with you, you will know which way is north just by looking at the stars (useful if you're ever stranded at sea), you will know what a Swastika originally meant, and if you happen to get sick with the flu virus, you will understand how exactly H1N1 is wreaking havoc inside your body.

And if you really want an update on my own life, here's what happened the past few weeks: I went to class. I came home. I did homework. I went to meetings. I watched TV. I went to parties. Oh and I passed the MCAT.

Soooo lets get to some interesting stuff, like some of the things I learned in Astronomy. By the way, the class itself is painfully boring because its an intro level non-science major class. However, some of the topics are nevertheless intriguing, such as the concept of lookback time. Lookback time is the idea that whatever you see with your eyes is actually old information. Allow me to explain. Say that you are standing about twenty yards in front of me and I wave to you. The moment I wave to you, you see it because the light reflects off me and reaches your eyes. However, because light has a finite speed (3 x 10^8 meters per second), it takes a certain amount of time for the light to get from me to you. In this case, it is far less than even a thousandth of a second. In normal earthly situations, nobody cares about lookback time because the distances we deal with are so small and so whatever we see is almost exactly what is happening.

Lookback time actually matters when we consider astronomical distances, such as that between galaxies, between stars, or even between the earth and the sun. The sun is so far away from the earth that it takes a full 8 minutes for the sun's light to reach us. So if you ever watch a sunrise, know that the first rays of sun you are seeing are a little bit late. The sun has already "risen" 8 minutes ago but you're just finding out about it now. Lookback time is even more dramatic when we talk about objects that are much farther away, such as stars and galaxies. Take for example the star Vega, which is 25 light years away from the earth. That is, it takes 25 years for the light from Vega to reach us. When we look up at Vega, we are seeing how it was 25 years ago. We don't really know the present state of matters. Vega could have exploded and died 10 years ago and we wouldn't know for another 15 years. Crazy, huh? And for galaxies that are ridiculously far away, such as those that are billions of light years away, it gets even cooler. When we see light that is more than 5 billion years old, we are looking well into the past, into a time before the earth and the solar system even existed. Imagine that.

The age of our universe is thought to be about 13.73 billion years. Get a load of this: the top circled galaxy in this picture is 13 billion years away.

Tell me this is not cool. What, now? Yeah. That's what I thought.

Take this Astronomy quiz from the New York Times if you're interested.