What is a light year?
The name light “year” is a bit of a misnomer because it makes it sound like it’s a measurement of time. A light year is simply the distance that light travels over one of our years on earth. Since light travels at about 671 million miles per hour (1,080,000,000 km per hour), a light year works out to about six trillion miles (9.5 trillion km). At the speed of light, you could travel to the moon and back again more than 1400 times in just one hour!
How big is our galaxy?
The Milky Way galaxy, of which our planet is a tiny part, is about 100,000 to 120,000 light years across. Our Sun is about 25,000 light years from the center of the galaxy, and orbits the center of the Milky Way clockwise. The Sun is moving at about 550 kilometers per second, so it will complete one orbit of the galaxy every 225-250 million years, dragging our little planet along with it.
How far have we seen into space?
The Hubble Telescope is our eyes in space, collecting snapshots of the distant universe since it was launched in 1990. In 2012, Hubble captured images of some galaxies that are 13.2 billion light years away from Earth. That means it took that long for the light of these galaxies to reach Hubble, so it’s more like looking into the distant past. Some of those galaxies came into existence just after the beginning of the universe!
What are the odds that aliens exist?
A 2013 study suggested that as many as 60 billion planets in our galaxy alone could support life.
Even if 0.0001% of those actually contain life, that’s still six million planets with living things.
And there are around 1,000,000,000,000,000,000,000,000 planets in the universe! The odds that life doesn’t exist somewhere other than earth are pretty slim, just because of the amount of tries the universe has had.
If we DO find aliens, will they conquer the earth?
Because of the vastness of space and the difficulty in traveling from one place to another, we may never meet intelligent life even if it does exist. But Steven Hawking, at least, thinks that it’s possible that aliens could come to earth to conquer us.
We humans could unwittingly broadcast our location into space, only to have hostile aliens find their way back to earth to kill us all. It’s possible that aliens could be nomads who travel around in search of natural resources. Hawking compared aliens coming to earth with Christopher Columbus landing in America, adding that that “didn’t turn out very well for the Native Americans.”
Of course, there’s always the possibility that we humans are one of the most advanced species in the universe…