Hubble Can See Into the Past

The Hubble Space Telescope (HST) is a time machine. Everybody probably knows that, but it still amazes me that HST can look into the past. For example, the sun we see is the sun as it was eight minutes ago. That's because light is fast, but not instantaneous. It takes sunlight a little over eight minutes to travel the 90 million miles to Earth. An impressive example of light's speed is that if you could travel at the speed of light you could circle the Earth at the equator 7 ½ times in a single second.

The farther away an object is the farther back in time HST sees. An object a light year away is 6 billion miles distant, the miles light travels in a year. If the Hubble Space Telescope (HST) is peering at it, it sees the object as it was one year ago. It's frustrating, but you can't see things at a distance in real time. But, that can be a good thing.

Astronomers tell us the age of the universe is around thirteen billion years. That means if the HST could see a galaxy that lies 13 billion light years from us, it is seeing it as it was when the universe began.

Now that's cool.