How We Know the Universe Is Expanding, and Accelerating


In the article, “How We Know the Universe is Expanding, and Accelerating,” the author talks about how our universe is expanding. “Everything in the universe is slowly moving farther away from everything else. Even the molecules in your body are drifting away from one another”.  The author states, that this expansion of the universe was first discovered by Edwin Hubble in 1931. Hubble made this discovery by studying the Doppler effect. The author explains how this helped make the discovery because “The same thing happens with light waves. When a galaxy is moving away, the color of the light shifts toward the red end of the spectrum.” . Next, after Hubble observed the redshifting in every galaxy he came to the conclusion that the entire universe is expanding. However , it is observed by Hubble that the galaxies that are farther apart are expanding faster then the galaxies that are closer together. Next, the author states, “in 1998, another Hubble—the Hubble Space Telescope—made another startling discovery about the universe’s expansion.” This telescope helped astronomers discover that the universe is not only expanding , it is also accelerating. Lastly, astronomers have not yet came to a complete conclusion on why the universe is accelerating , but they do know there is some kind of energy pushing it apart.

Objective 17 was to be able to explain how astronomers know that the universe is expanding and how they determine the age of the universe. The article explains how Hubble discovered that every galaxy seems to be moving away from the earth. This directly corresponds to what we did in class on the screen with the different dots. During this activity , someone would choose a dot and say it was our Milky Way galaxy and then when we would put a blown up image of the dots over the top of it and it would show all of the other dots “running” away from the central dot. Also, just like the article the farther the dot , the more it seemed to be moving away. Just like the article explains about the galaxies; every galaxy astronomers have observed seem to be moving away, and the father the galaxy the faster it is moving away. Astronomers believe dark energy is what is causing the universe to expand and accelerate. In the textbook, most of a galaxy’s mass is in the form of dark matter and the gravity of that dark matter is probably what formed protogalactic clouds and galaxies from slight density enhancements. Therefore, the evidence points to eternal expansion given that the overall matter density of the universe appears to be only about 25% of the critical density. Lastly, as a further classmate pointed out to me, The Big Bang can also show the universe is expanding. It shows this by looking back there was nothing but radiation and elementary particles. The further into the future you go, the bigger the universe has become.  The universe is now 1,000 times larger now.

I found this article personally pretty interesting. The reason I say this is because I learned something knew about our universe. However,  learning that the universe is expanding and accelerating is not what interested me. The actually interesting part to me is how this article got me thinking in the future how this expanding and accelerating will affect me personally along with earth and the people in it as a whole.


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