This is a guest post by Leaf.
Once upon a time, our illustrious scientific guru deemed to explain the size of the universe. The numbers used to describe the sizes and distances seen in the universe are mind-blowingly ridiculous and are frankly hard to fully comprehend their sheer enormity. That’s a lot of words just to say it’s fucking huge. What if I blow your mind and tell you it’s not only huge, but it’s getting bigger? Now let me blow your mind a second time and tell you that not only is it expanding, it’s speeding up. Let that sink in for a moment. This mind-numbingly huge universe is get bigger, and not only is it getting bigger but the rate at which it is getting bigger is getting faster.
Now there are many ways I can take this topic, all of which are extremely fascinating. For this I’m going to focus on how we know what we know. You might remember awhile back our esteemed scientific virtuoso talked about spectroscopy. You’ll remember he mentioned that different elements absorb/emit different wavelengths of light and that they leave marks in the light spectrum, like a barcode. Scientists can use these spectral lines to determine the makeup of distant stars. An interesting nugget is the lines from a distant star don’t quite line up with the way they look here on Earth. The patterns are the same, but their location on the light spectrum has shifted.
Another tidbit our renowned scientific expert recently mentioned (I’m not very original here am I) was that light is a wave. When the source of a wave is moving the waves in front of it are compressed while the waves behind the source get stretched. This is called the Doppler effect. A good real world example of this is a vehicle will sound higher pitched as it is approaching you, but once it passes you the sound gets lower as it moves farther away.
When it comes to the light spectrum, blue light has a shorter wave length and red light has a longer wavelength. Therefore compressed light waves will appear more blue, while stretched light will appear more red. This is called blueshift and redshift. If something is blueshifted, it is moving toward you. If it is redshifted, it is moving away from you.
So how does this prove the universe is expanding? As far back s as the late 1840s scientists were attributing the shift in the observed special lines of distant stars to the Doppler effect. But it wasn’t until 1929 that Edwin Hubble measured the redshift in 46 galaxies discovering that galaxies where moving farther away at a rate proportional to their distance (meaning the farther away they were the faster they were moving). This is strong evidence to support the idea of the Big Bang. In an explosion, material around the outer edge of the source will travel the farthest and the fastest. But eventually the energy from the explosion dissipates that material will slow down its rate of travel due to counteracting forces. So one would think that the expansion of the universe would follow that same logic as gravity pulls everything back. At the very least, there is no counteracting force and everything just continues on at the rate they currently are going on into infinity, right? Well in 1998, two separate teams researching supernova used the redshift to compare the the rate of expansion since the supernova occurred. They discovered that it’s extremely likely that the universe is speeding up in its expansion. “How is that possible”, you might ask. That my friends is a topic for another Science Saturday.