Our Journey Through Space and the Expanding Universe
We all have a favorite way of relaxing. For some, it’s lying the couch watching football on a Sunday afternoon. Others curl up in an easy chair with a good book. It might be a walk in the forest where everything is quiet and the world seems to be at peace. But let’s take a little trip in our minds for a few minutes. Without even the aid and protection of a spaceship, we are going outside the Earth’s atmosphere to see what is happening in space.
I did a search on Google that included the words, hanging, planets, space, suspended, stars, and galaxies. Everywhere I read, space was described as a place where heavenly bodies were hanging or suspended. When I imagine such a place, it is static, unmoving. But is that reality or fantasy?
The Earth's Rotation as Recorded by the Spaceship Galileo in 1990
The Earth's Rotation and Orbit
Let’s continue our tour of space to see what we find. We will begin with our home, Earth. Look back and describe what you see. Even from this vantage point, it seems to be a quiet, unmoving sphere. In reality, our planet is spinning around on its axis. How fast is it spinning? The speed at which our planet rotates is 1700 kilometers per hour or one half a kilometer per second. For my American readers, that is 1056 miles per hour or 0.3 miles per second.
So, as you lie on the couch or lounge in the recliner, you are not really as still and quiet as you think.
That is not the only movement in space. Earth orbits the Sun once every 365 days. How fast are we going as we make that annual trip? This will make the previous figure of our rotation seem slow. We are orbiting the Sun at 30 kilometers per second or almost 19 miles per second. Now that’s speed, right?
Our Solar System's Path Through the Galaxy
The Elliptical Path of the Sun Through the Galaxy
But the roller coaster ride isn’t over yet. The Earth spins on its axis. The Earth orbits the Sun. Is the Sun static? Is it quietly suspended in space? No, it is moving as well. Our Sun is in the midst of a very long journey, moving along an elliptical path within the Milky Way Galaxy. One trip around this celestial superhighway takes approximately 250 million years. It must be creeping along like a snail for it to take such a long time, wouldn’t you think? But here is what scientists have discovered. Our Sun is traveling in this elliptical pattern at over 200 kilometers per second or 124 miles per second.
Keep in mind that, so far, three movements are occurring simultaneously. Earth is spinning at half a kilometer per second. Earth is orbiting the Sun at 30 kilometers per second. And the Sun, with us in tow, is on an elliptical journey going in excess of 200 kilometers per second. Where, oh where, is the intergalactic highway patrol?
Is that enough movement, enough speed to knock you off the couch or out of the recliner? Well, it may come as no surprise that we aren’t finished yet.
The Andromeda Galaxy
The Milky Way Galaxy and the Andromeda Galaxy on a Collision Course
The movement I am about to describe is of a different sort. It isn’t a rotation or an orbit. It is in a straight line. Look out from our vantage point above the Earth. We find the constellation Cassiopeia and move downward and to the right until we see a hazy, blurry area. This is the Andromeda Galaxy, the nearest major galaxy to our own. In 4 billion years the two galaxies will collide. Make sure all your insurances are paid up, folks.
Two friends were talking one day. One was an astronomy enthusiast. He told the other fellow that the Andromeda Galaxy would collide with our own in 4 billion years. Apparently, the friend wasn’t listening too carefully. He sputtered and asked his astronomy loving friend to repeat what he had said, which the friend did. “Whew,” the other exclaimed, “I thought you said 4 million years.”
The two galaxies are traveling toward each other at 109 kilometers per second or 68 miles per second.
A Galaxy Cluster: Overdense Regions of Space
Movement Caused by Underdense and Overdense Regions of Space
And still, there is more. We all know that space is filled with planets, stars, solar systems, and galaxies. But these bodies are not evenly distributed. There are places known as overdense regions and others are known as underdense regions. We can all understand that the overdense regions would have a gravitational effect on our galaxy. Scientists are just now realizing though that the underdense areas also have a tremendous impact on us. The lack of gravity acts as a repulsive force. It pushes against our galaxy. We just happen to live near a massive underdense region. The forces on our galaxy of these two areas create motion that scientists have calculated to be about 300 kilometers per second (186 miles per second) from each source for a total of 600 kilometers per second (372 miles per second).
Does the couch or recliner still feel comfortable? Hang onto the armrests. We aren’t finished yet.
The outer edge of the universe is expanding at a rate greater than the speed of light
The Expanding Universe
In 1929, scientist Edwin Hubble discovered that the universe was expanding. Notice I did not say that the heavenly bodies and formations such as planets, stars, and galaxies were expanding. No, the universe is expanding. It’s as if you sewed buttons all over a piece of stretchy fabric and pulled the outer edges. The buttons would move because the fabric was expanding. This is how the universe is expanding. How fast is this occurring?
The universe is expanding at a rate of 74.3km per second per megaparsec. A megaparsec is a measure of distance. Here is how this calculation works.
- Megaparsec one, where Earth is located, is traveling at 74.3 kilometers per second. From this point on, each megaparsec will increase in speed by 74.3 kilometers per second.
- Megaparsec two is moving outward at 148.6 kilometers per second.
- Megaparsec three zips along at 222.9 kilometers per second.
- Megaparsec four is barreling through space at 297.2 kilometers per second, and so on.
Each parsec is about 30 trillion kilometers (19 trillion miles).
A megaparsec is made up of one million parsecs or 30 trillion kilometers (19 trillion miles) times one million.
A gigaparsec is one billion parsecs or 30 trillion kilometers times one billion.
So how big is the universe? The edge of the known universe is 14 gigaparsecs from Earth. (14 billion times 30 trillion kilometers or 19 trillion miles).
Each of these sections increases in speed over the previous one by 74.3 kilometers per second. At that rate, the outer edge of the universe is expanding at a rate greater than the speed of light which is 300,000 kilometers per second or 186,000 miles per second. And it’s getting faster, not slower.
Don’t miss the implication of the outer megaparsecs racing away at greater speeds than those behind them. The universe is growing. It is growing apart. Everything is getting farther away from everything else. Someday, if we were around to experience it, there would be nothing to see in the night sky. It would be too far away.
The Future Universe
The Earth rotates at 0.5 kilometers per second. The Earth’s orbit around the sun is at 30 kilometers per second. The Sun journeys (along with our solar system) on an elliptical path at 200 kilometers per second as we race toward the Andromeda Galaxy at 109 kilometers per second. Underdense and overdense regions cause movement up to 600 kilometers per second. And to top it all off, the universe is expanding at maximum speed over that of the speed of light.
And it all is happening at the same time. Dramamine anyone?
The next time you kick back on the couch to watch the game or curl up in the recliner with your book, take a second to think about what is going on around you, even though you can’t feel even the slightest movement.
Oh, by the way, you can come back down to Earth now. Thanks for joining me on this little journey.
An Expert Explains The Expanding Universe (4 minutes)
Questions & Answers
© 2019 Chris Mills