Your Eyes as Time Machines
Have you ever wished you could go back in time to see what the universe looked like in the past? Well, you are doing that when you look into the sky, where light takes time to come to you. The moon, for example is about 240,000 miles away; it takes light about 1.3 seconds to travel from there to here. If a giant asteroid hit the moon, we wouldn’t see the explosion until 1.3 seconds later. Light from the sun, which is about 93 million miles away, takes 8 minutes to reach us, so it is 8 minutes old. Light, the fastest thing in the universe, travels 186,000 miles in one second. A light year is a measure of distance, not time; it’s the distance light travels in one year, which is about 6 trillion miles. We can say that the sun is 8 light minutes away from us, and the moon is 1.3 light seconds from us. Light from the planets in our solar system are light minutes or light hours away, depending on the planet’s distance from us. When you look at these objects, you are seeing them as they were minutes or hours ago. Your eyes have become a time machine.
All of the stars in the night sky are part of our Milky Way Galaxy. The nearest star is 4 light years away, 24 trillion miles from us. It takes light 4 years to cover that distance, so we see that star as it looked 4 years ago. Other stars are hundreds or thousands of light years from us. Some may have burned out since the light you now see left there so long ago. We may see a star as it appeared in 1776, when our country became independent and another as it was in 2560 BC during the building of the Great Pyramid of Cheops at Giza. Each star in the sky represents a completely different point in time. Large telescopes can see galaxies billions of light years away and so we see them as they looked back then, giving us a snapshot of the early universe.
Here is a link to find your birthday star, a star whose light left that star on the day you were born and is now reaching your eyes.
To find your birthday star click here. Then come back a month or two later and your birth star will be another one.
Now, when you look at stars in the night sky, remember you are seeing them as they were in the past. Your eyes and telescopes are time machines transporting you into the past.