Looking back in time

The farther out we look, the farther back we look.

I mentioned in my about me paragraph that I like astronomy. I think that the reason that I like astronomy so much is because it makes you consider size on a cosmic scale. Let me give you an example.

When you see something, your brain is interpretting light waves captured by your eyes that have traveled to you from the object that you are looking at. Light waves travel at the speed of light, which is fast, but not instantaneous. When you look at an object, you are seeing an image of the object at the time the light waves left the object and began travelling to you. Since the speed of light is so fast, this time is negligible and we just take for granted that the image we have processed is current.

The lag becomes noticeable when you are looking into space, though. It takes 8 minutes for light to travel from the sun to Earth. So, when you look at the sun, you are looking at it as it was 8 minutes ago. What if people lived on the sun, and you could see them through a telescope? When you observed them, you would be observing their actions 8 minutes ago. You would be looking at them in the past.

This is an interesting concept, but doesn’t really hit home until we expand it to a cosmic level. Consider the galaxy Andromeda, the closest neighbor to the Milky Way. Andromeda is 2.5 million light-years away. A light-year is the distance that a ray of light can travel in a year. So, light travelling from Andromeda travels 2.5 million years before it reaches us. Andromeda can be seen clearly though a telescope. Whenever you look at Andromeda, you are essentially looking at a "video feed" of it at this second, 2.5 million years ago. If you had a telescope that was strong enough to zoom in on a planet in that galaxy, and were able to observe Andromeda people living their lives, you would be looking at a live feed of people who have been dead for 2.5 million years. Their planet might not even exist anymore. You are literally looking into the past.

The concept that by looking farther and farther away you are looking farther and farther into the past, blows my mind. Technology is improving at an exponential rate. Think about what would happen if you showed somebody from the year 1400 technology from 1700 (300 years in the future). There was improvement, sure, better ships, better buildings, etc, but they wouldn't be blow away. But now think about showing somebody from 1700 technology from 300 years in the future like an iPhone. With technology growing as quickly as it is now, its feasible to think about a future with telescope-like technology that is strong enough to meaningfully look into the past.

So be careful not to be silly next time you look up into the sky. Because 2.5 million years from now, people on Andromeda, staring at Earth through a microscope, could be seeing every move you make!