The Vermont sky is stunning on crisp, clear, autumn evenings. Do you ever look up and wonder what’s out there in space? Or about the size of the Universe? Many of my students have been trying to wrap their minds around this question this semester as we explore the universe together. It seems as if the more we understand about the universe and how enormous it is, the smaller we feel!
To us, the earth seems gigantic. I flew to India last year for a research project, and the flight from New York City to Mumbai took 18 hours! Of course, being crammed into the economy section and wedged between other passengers doesn’t make the time go by quickly.
I felt like I had spent a few days in that tin can by the time I got off. The distance between the east coast of the United States and the west coast of India is huge -almost 8,000 miles – but nothing we cannot surmount.
Once we step off our earth into the rest of our solar system, distances get so big that we start measuring them with different units. Astronomers often talk in terms of “light minutes,” “light hours,” or “light years.” Light travels at the fastest speed physically possible – almost 700 million miles per hour.
Even traveling that quickly, it takes sunlight nine minutes to travel from the sun to the earth. So that sunlight streaming in the window as you read this left the sun nine minutes ago! That is, the sun is nine light minutes away. With our current technology, it would take one of our spacecraft months to travel that far. Pluto, by comparison, is about six light hours away. Now we’re talking years for spacecraft to get that far!
Our technology does let us travel to realms as far away as Pluto – it just takes a little while. In 1977, NASA launched the unmanned spacecraft Voyager I. It has been traveling outward in our solar system ever since. Just this year it entered the region that separates our solar system from interstellar space! It has taken Voyager I 30 years to traverse our solar system!
Wow. So how much larger is the universe? It turns out our solar system is just a speck of the entirety of the universe. To travel from the earth to our nearest star (besides the sun) takes four light years, which is over a trillion miles! Remember, Pluto is only six light hours away! Our solar system is in the Milky Way galaxy, which contains billions of other stars, and, probably, millions of other planets besides our own. Our entire galaxy is 100,000 light years across. When you see that faint whitish arc across the night sky that people call the Milky Way, you are seeing one of the spiral arms of our own galaxy.
Now think even bigger – the universe contains billions of other galaxies. We are not the only galaxy out there. The closest galaxy to the Milky Way is the Andromeda Galaxy, which is over two million light years away!
It’s so far away that, unless you have very good eyes, you need a telescope to be able to see it in the night sky. We definitely can’t get there from here with our current technology.
It is overwhelming to think about how small we are in comparison to the entire universe. But I think it’s overwhelming in a comforting way. It always makes my own problems seem a tiny bit smaller. I love how the poet Ralph Hodgson expressed this feeling in The Song of Honor:I stood and stared; the sky was lit,
The sky was stars all over it,
I stood, I knew not why,
Without a wish, without a will,
I stood upon that silent hill
And stared into the sky until
My eyes were blind with stars and still
I stared into the sky.
Go stare at the night sky tonight. I promise you won’t be disappointed.