Top 5 Questions About Our Universe, Answered

Have you ever wondered how big the universe is? How it formed? How fast it's expanding? Whether it will ever die? 

Yeah, we've wondered about those things, too. And luckily for us, so has Paul Sutter, an astrophysicist at The Ohio State University and the chief scientist at COSI Science Center. Sutter, who is is also the host of the podcasts Ask a Spaceman and RealSpace, and the YouTube series Space In Your Face, is a frequent contributer to Space.com's Expert Voices: Op-Ed & Insights. 

Sutter has answered some astronomically huge questions for us here at Space.com, and we've had the pleasure of sharing his answers with you, our dear readers. So without further ado, here are 6 of the biggest questions we've had about our universe, answered by the astrophysicist himself. 

[FIRST UP: How do you measure the universe?]

Things in space are, appropriately enough, astronomically far away. The distance to the sun and other planets in the solar system is easy enough to calculate, especially because we can toss probes about here and there, and presumably, the probes will know how far they've traveled when they land.

But how can astronomers make the great leaps to measure the distances to the far-flung stars? How can we claim with any certainty the breadth and depth of the Milky Way? And what ruler spans the farthest reaches of the universe, separated from us by seemingly unfathomable oceans of darkness?

It starts with triangles

I want you to perform a science experiment. Come on, this will be fun. Start by shoving your nose right into the screen. That's it, right here. Close one eye. Now switch to the other. Continue alternating. If anybody gives you distraught glances, smile calmly, and with your sagest voice, tell them, "This is for science."

As you alternate eyes, the words on this screen should leap left and right, covering huge apparent distances. Now, back up to normal reading distance. Continue switching eyes. The words still shift, but not nearly as much as when we were a little more intimate.

Congratulations! You've discovered parallax. It's part of the reason it's useful to have two eyes: With binocular vision, your brain can judge distances without needing to evolve a ruler coming out of your forearm.

It's easy enough to calculate the distance: The span between your eyes forms the base of a long, skinny triangle. The amount of swing a distant object appears to travel as you switch eyes gives you one of the angles in the triangle. With a little bit of high-school geometry, you can know the distance to your desired target.

OK, great, but that's not exactly useful for stars, which are vastly farther away than this screen. But that's fine; we can still play the same game — we just need a different set of cameras. How about, say, Earth in the summer and Earth in the winter?

That's a pretty big triangle. Because we know the distance from the Earth to the sun, we know how wide our binoculars are. And by carefully measuring the teensy-tiny wiggle in a star's position between the seasons, we can compute the distance.

Well, to a point. I mean, most stars are so fantastically far away that we could never hope to measure their parallax, no matter how sophisticated — or big — our triangle gets. Read more about how to measure the universe here.