The Sky's the Limit: Our Corner of the Universe

By Kelsey Johnson

Well, OK, so our universe doesn't actually have any corners. At least not that we know of. It turns out that astronomers don't actually know what the shape of the universe is because we can only see a tiny part of it. For all we know, we could be living in an enormous multidimensional bagel. Or if you really want to take your brain for a spin, our entire universe could be inside a black hole of another universe.

Whatever the shape of the universe, it is fascinating, and the amount of stuff we don't actually know is alarming. As one simple example, we don't know what 99% of the universe is made of - except that it is nothing like "normal" matter and energy. This is where our children come in. Who will figure out what our universe is made of? Or if it is shaped like a doughnut? Or if there is other life out there?

As it happens, we are really lucky; our tiny little patch here in central Virginia is a great place to be a budding young astronomer. In fact, southern Albemarle County features some of the darkest night skies of anywhere on the east coast. To an astronomer, getting away from city lights is critical. Did you ever think about dark night skies as a natural resource? It breaks my heart that kids can grow up in a city and never actually see the stars with their own eyes. I have to think that this can have a profound impact on the world view a child forms.

When I'm giving public talks, there is always that one person who asks something along the lines of, "What's the point of astronomy?" I have a love-hate relationship with this question. Sure, there are actually lots of practical benefits that spin off from astronomical research. But for me the real answer is much more visceral and intuitive. I can't even remotely understand how anyone wouldn't be curious about the universe in which they live. As an example, let's say that as a child your parents never let you go outside. I mean never - not for school, church, shopping, anything. You did, however, have a few windows. You could see a street, perhaps a few other houses, some grass, maybe some trees. How do you think your worldview would be different? Would you be content to stay inside, or would you want to go explore the world where you live? Now change your house to the Earth, and the windows to telescopes, and there's the analogy. We are pretty much grounded here on Earth.

Activity: How small is the Earth?

It can be hard to wrap our minds around the size scales in the universe, so this is a fun activity to help put things in perspective. All you need is a grapefruit and some nonpereil sprinkles. Step 1: Have the child hold the grapefruit and ask them to imagine that it is the Sun.

Step 2: How big would the Earth be by comparison? Hand out a couple nonpereil sprinkles -- these are about the right relative size for the Earth and the grapefruit Sun. This usually amazes adults and kids alike!

Step 3: Given the relative sizes of the nonpereil Earth and grapefruit Sun, how far away would the earth be? It's great to have a couple kids to walk around with their sprinkles and respond to cheers of "closer!", "further!", etc. At this scale, the nonpereil Earth would be about 13 yards away (grapefruit size will vary, and you don't need to be precise to get the point across).

Step 4: Sit back and think about how amazing it is that we all live on this tiny little sprinkle and everything we've managed learn about other planets and the universe. We've even sent the most miniscule little spacecraft off to every planet in the solar system to other tiny sprinkles far far away.

Step 5: Any guess how far away the nearest grapefruit star would be on this scale? Answer: somewhere on the west coast.

Kelsey is an astronomy professor at the University of Virginia, where she also directs the "Dark Skies, Bright Kids" program. She has two children who keep her grounded on earth.

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