NORFOLK, Va. — A light year is exactly what it sounds like: the distance light travels in one year. If you need to get somewhere quick, you'd want to jump on this train because light travels through space at 186,000 miles per second, which equates to about 5.88 trillion miles per year.
Determining the speed of light and how far it can travel in a certain period of time allows astronomers to use this as a measure of distance within the entire realm of space.
The circumference of the Earth is just under 25,000 miles, so light can travel around the earth over seven times in just one second and in one minute, light can travel over 11 million miles.
The distance from the sun to Earth is about 93 million miles, which takes light about 8 minutes and 20 seconds to reach the Earth.
Let's keep things simple: if we were traveling at 60 mph for 24 hours a day, 365 days a year, and decided to travel one light year, it would take about 11.2 million years to get to where we were going... hopefully aging wouldn't be a factor! Say we hitched a ride on something fast like Voyager 1, NASA's farthest-traveled space probe which is moving at around 38,000 mph. We would reach a light-year much faster; it would only take us about 17,000 years!
If we wanted to zoom out in space a bit and look at the Milky Way, the galaxy that includes our solar system, (there are estimated to be about 100 billion to 200 billion galaxies in the observable universe) the Milky Way is about 621,371,000,000,000,000 miles (six hundred twenty-one quadrillion, three hundred seventy-one trillion) or about 100,000 light-years across.
So, even if we were traveling at the fastest speed in the universe, which is light, it would still take 100,000 years to cross the Milky Way and that doesn't even begin to scratch the surface of how much farther things are in the universe. Again, if we were in a car going 60 mph, it would take us two TRILLION years; the universe itself isn't even that old!
If we look at other galaxies nearby like the Andromeda galaxy, 100,000 light years seems small. The Andromeda galaxy is 220,000 light-years wide, while another galaxy, IC 1101, spans as much as 4 million light-years.