Look-UP

by Mitchell Tester, College Student

The Ever-Expanding Universe

Part Two

I live in the woods, with a dirt driveway that feels like you’re off-roading the whole time you’re on it, so I’m way off the beaten path, you could say. With that, comes serene feelings of peace as I’m sitting on my front porch. I hear the crickets chirping all around me, I hear owls off far in the distance, and I see deer frolicking through the trees at the edges of the yard. My fiancé and I will often sit on this front porch at night, sipping wine, and just talking about our day, catching up on life. With the peaceful setting, we will often have deep discussions about  life and the universe. With astronomy being an interest of both of us, that topic comes up a lot.

I remember one night in particular, where the crescent moon was perched up in the sky, partially obscured by the lingering haze of an approaching thunderstorm. We sat quietly for a moment—or maybe a little longer—and she asked me a simple (well, not quite so simple) question: “If you had to pick one… what is your favorite space fact.” Surprisingly enough, I believe this is the first time someone has ever asked me that question. I have had many people discuss astronomy with me, friends and family and so forth. Although, no one has ever asked me that specific question. I try to answer her. “My favorite… well I think… there’s so many, I’m not sure…” It honestly stumped me for a moment. But, then, it suddenly became so clear to me, and I said without another moment of hesitation: “The ever-expanding universe… yeah, that’s the one.”

Instead of being understandably confused by even the notion that the universe is expanding, she simply asked, “Why?”

“I think it poses a major scientific mystery, and I love a person’s wonder and imagination when discussing why the universe is expanding,” I explained.

So, when thinking of what to write about, I thought, what would be better than the space fact I love the most: the expanding universe?

I want you to think for a moment about why the universe would be expanding. It’s mind-boggling, isn’t it? To think that space itself is stretching, causing galaxies to move further apart over time, ignites our curiosity, our imagination, and our wonder.

That is exactly what I love about astronomy; it is so unknown and foreign, that the mind comes up with some very bizarre explanations to things we do not know or understand. This is why the genre of Sci-fi is home to some of the most strange stories if you think about it, and why it appeals to so many people.

Edwin Hubble showed that the universe was expanding by observing in 1929 that the more distant a galaxy is, the faster it is moving away from Earth, a principle now known as Hubble’s Law.

I posed the same question to my fiancé that she initially asked me, “What is your favorite space fact?” 

“Hmmm… maybe gravity? she answered. 

Gravity is one of the contributors to the expanding universe. At the beginning of the universe, gravity is what caused all these galaxies to form. Gravity is what causes matter to attract to matter. Galaxies are still formed today, although at a much slower rate. Why is that? Well, part of the reason is that space between matter is much farther than it once was, because the universe is expanding.

The simplest explanation—and I am using that ironically in a way—is that the Big Bang is the reason of the expanding universe, or at least the start of the expansion. The Big Bang was an astronomical explosion, and like any explosion, it propelled matter outward, and it has been expanding since. We can tell this due to something called redshift, which is where the wave lengths of the light that is emitted from an object are stretched, making them appear red. While an object that is moving toward the observer has blue wavelengths that are less stretched. Redshift is useful for astronomers because they are able to use it to measure the distance of a certain object. What we have found is that the farther an object is from us, the more stretched the wavelengths are.

Redshift can be used to describe the stretching of light as the universe expands. As light travels from these far distances, the light wave lengths stretch as they travel away from us. Redshift also indicates speed, if we look at a galaxy and the light emitted from it, the more redshifted it is, the faster it is moving away from Earth. So, the farther away something is, the faster it is moving. This accelerated expansion of the universe effects the observed redshift. Currently, what we know about the reason of the accelerated expansion is not very much; it is a mystery. “Dark energy” is the unknown reason behind the acceleration.

The ever-expanding universe isn’t my favorite space fact just because of the staggering distances, the speed of light, or the unknown theories such as dark energy. It’s more due to the questions it provides and the imagination it conjures up. Even if we never set foot on a planet of a distant star, even if the light we see today is not what is truly there but rather a light from a dead star, it doesn’t stop us from discussing it and wondering about more than what is right in front of us every day. There are corners of the universe that are unreachable, and the more time that passes, the more they go beyond our reach. I hope what you take from this, though, is that we should never stop looking up and asking why.