- Hey smart people, Joe, here.
How do we figure out how far away things are?
If you're measuring the distance to an object nearby, it's pretty easy.
We take another object whose length that we know, and we use it as a reference to find that distance.
What about an object that's beyond our physical reach?
Well, we can literally walk to that object and count our steps to calculate the distance.
Even something as far away as the moon, we can shine a beam of light, bounce it off.
Special mirrors left on the lunar surface by Apollo astronauts, count how long that light takes to make the round trip and calculate distance.
These are all ways of measuring using things -- physical objects in the world around us.
But how do we measure how big a universe is?
