Center of the Universe

Have you ever told a narcissist that he or she is not the center of the universe? Well, it turns out that there may not even be one to begin with.

Before we look into the science behind it, let’s hear a few opinions on the center of the universe from MV students! The question “Does the universe have a center?” left many students stumped. Sophomore Aparna Manoj was on the right track for she explained, “The universe has no center because it expands.” However, she questioned how the universe could expand if there was nothing beyond it. Sophomore Shivika Sivakumar believes that there is no center of the universe because the center of the universe cannot be defined. She explains that because the universe is expanding, the center is constantly changing. Both students made the correct conclusion that there is no center of the universe, but let’s look into why there is no center.

According to Astronomy Notes created by Nick Strobel, a college physics professor, the cosmological principle states that the universe is uniform in two ways. First, it is homogenous, or in simple terms, it has the same properties at every point. Second, it is isotropic, meaning it has the same properties regardless of which direction you look. Space has been expanding since the Big Bang which occurred was more than 14 billion years ago! Space is 3-dimensional, so space is expanding in three different planes. Because the universe is uniform at all points, there is really no center to the universe!

The most intriguing piece of evidence that proves that the universe has no center is the expansion of the universe. An astronomer at Caltech, Edwin Hubble, discovered the expansion of the universe in 1929. The expansion of the universe is unique because it is not expanding at one point in which case, we could call that point the center of the universe. The perfect cosmological principle states that the universe is expanding equally at all points. In order to understand the idea that space is expanding at all points, it is best to use an analogy of a balloon which is used in Astronomy Notes. If you draw equidistant points on a balloon with a sharpie, when you blow up the balloon the distances between these points will be greater than the original distances by the same amounts. However, there is a difference between the balloon analogy and what is actually happening in space. In the balloon analogy, the balloon is expanding in the space around it. In actual space, the space itself is expanding, so the entire coordinate plane itself is also expanding.

But how do we know that the universe is expanding? One piece of evidence is the Doppler Effect and how it applies to stars.

You may have seen this physics question about Fred and the Doppler Effect in your AP Physics 1 class!

The problem says “Fred is going to die.” And indeed he is because he will perceive a the sound from the speaker with a frequency of 1172 Hz because of the Doppler Effect! You may have picked up from your physics class that the Doppler Effect states that the motion of the observer and the source affects the frequency of sound that the observer perceives. If the observer and the source are moving closer together, the frequency that the observer detects is higher than the actual frequency of the source. If the observer and the source are moving apart, the frequency that the observer detects is lower than the actual frequency of the source.

The Doppler Effect applies to many types of waves including light and sound waves. For stars, we are specifically interested in the light that they emit. Different colors of light have different frequencies and wavelengths. However, all light waves have the same velocity. This image from NASA shows that violet has a smallest frequency and the smallest wavelength while red has the lowest frequency and the longest wavelength.

What evidence is there that the universe is expanding?

Redshift is the term used to describe the Doppler Effect involving the light emitted by stars.

Exploratorium explains that stars appear to emit red light because they’re moving farther from Earth. As the star or the source moves away from the earth, the wavelength of that the observer on earth detects is longer than the wavelength of light that is actually being emitted by the source or the star. The faster the star is moving away from earth, the greater the redshift that an observer on earth will observe.

Redshift proves that the stars in other galaxies are moving away from earth, supporting the idea that the universe is expanding.

However what proof is there that the universe is expanding uniformly and not from its center? An article by Philip Gibbs of the University of California Riverside explains that the Big Bang was not an ordinary explosion in which one would observe that there was empty space beyond the end of the explosion that would be expanding. In fact, there is no defined edge of explosion for the Big Bang! Instead of a definite edge, there is a light glow of gases that date back to the origin of the universe. This is called “cosmic microwave background radiation” or CMB and is shown by the images below taken by the Wilkinson Microwave Anisotropy Probe. This radiation is uniformly distributed in every direction in space. Therefore, the idea of CMB supports the cosmological principle because it is uniformly distributed throughout the universe. The image below from NASA shows a map of the radiation and its distribution.

There are many questions that are still to be answered about the expansion of the universe. For example, although the expansion of a balloon is finite, is the expansion of the universe infinite? Will it expand for an indefinite period of time or will it collapse? Why is the rate at which the universe is expanding increasing? Is dark energy responsible for the expansion of the universe? NASA hopes to find answers to these questions, for they are launching the WFIRST project to find connections between the expansion of the universe and dark energy.

In conclusion, since the universe is uniform at all points and is expanding uniformly at all points, it has no center. So next time someone tells you that you aren’t the center of the universe, you don’t have to take any offense; after all, there is no center of the universe!

 


 

References

http://www.astronomynotes.com/cosmolgy/s3.htm

http://math.ucr.edu/home/baez/physics/Relativity/GR/centre.html