By Chris Hwang
It’s impossible to look at the present. As uncanny as this may seem, it’s quite literally true; when you look at something, you are looking at it the way it was in the past, not as it is in the present. How is this possible?
When light bounces of an object and reaches your eyes, that object becomes visible to you; and as fast as light is, it still takes time to travel. Light travels approximately at the speed of 300 million meters per second. Assuming that your eyes are about 60cm away from the screen you are reading this on, you’re reading this the way it was 2 nanoseconds earlier, which is equivalent to two-billionths of a second. In most cases, the time it takes for light to reach your eyes is inconsequential. However, look far enough into our cosmos, and you’ll be looking into the far past.
In fact, when you’re looking at the Moon, you’re looking at it the way it was one second ago. Even further away, the Sun is 8 minutes and 20 seconds away from us at the speed of light; any time you look at the Sun, you’re looking at it the way it was more than 8 minutes ago.
Telescopes are Time Machines
The term “light year” refers to the distance light can travel in a year; a unit of measurement in which we measure our vast universe. When you look at something that is one light-year away, you are looking at it the way it was a year ago. Powerful telescopes, such as the Hubble Space Telescope, allow astronomers to look at galaxies that are billions of light years away from us. For example, Galaxy 4845 is located 65 million light years away from us. We are seeing it the way it was during the time in which dinosaurs roamed around the Earth. Theoretically, if aliens in this galaxy had an outrageously powerful telescope, they would be able to see dinosaurs on Earth. The James Webb Telescope, will allow us to look back at the first stars of the universe, just 380,000 years after the Big Bang.
The Furthest Object Ever Spotted by Humans
Called the eXtreme Deep Field, or XDF, this photo is the combined result of 10 years worth of photos taken by the Hubble Space Telescope. It contains over 5,500 galaxies, dating all the way back to 13.2 billion years ago.
The idea of looking far to look at the past is truly captivating. At the same time, it’s quite startling that many of the stars we see on Earth today are actually no longer in existence. So, when you look up at the night skies, keep in mind that things may not be the way they seem.