Circling earth's orbit, the Hubble Space Telescope is humanity's unblinking eye to the cosmos. It allows us to peer deep into the universe to the very dawn of time and helps us resolve long-standing problems in astronomy. It also helped confirm several theories put forth by the man after whom the telescope is named, Edwin P. Hubble.
Every once in a while a person puts forth a theory that requires us to rewrite our accepted model of the cosmos. Edwin Hubble was such a person. He made several important discoveries during his career but one in particular stands out to me as the most mind-blowing of all. It's this discovery which forced astronomers to rethink their view of the universe in a radical way.
Allow me to set the scene.
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The year is 1922. The place is Mount Wilson, California, site of the poorly-named Hooker Telescope, the world's most powerful device of its kind. At the helm of this sits Edwin Powell Hubble, a 33 year-old astronomer only five years removed from college.
Edwin wanted to be a professional astronomer since boyhood but, being a dutiful son, he fulfilled his father’s wishes and studied law instead. He was at Oxford University doing just that when he received word that his father had passed away. Upon returning home to take care of his mother, Edwin, then 25, decided to abandon law and pursue his dream. He received his PhD in 1917 after publishing his dissertation, “Photographic Investigation of Faint Nebulae,” and became an astronomer.
In order to fully appreciate Hubble’s discovery we must first talk about the model of the universe at the time. You see back then, astronomers believed that the Milky Way galaxy was a so-called "island universe,” an island of matter surrounded by the infinite void of space.
With their pre-Hooker telescopes, astronomers observed two different types of celestial bodies: stars and faint, nebulous shapes which they called nebulae. No one knew exactly what nebulae were. The prevailing theory was that they were oddly-shaped clouds of gas or diffuse stars. They named them according to shape. The Spiral Nebula, the Eagle Nebula, and so on. It was assumed that both stars and nebulae were part of the Milky Way.
Equipped with the state-of-the-art Hooker telescope, Edwin got an unprecedented view of the heavens. As you probably guessed from the title of his dissertation, nebulae were of particular interest to him. What he discovered about them was world-shattering. According to Hubble’s calculations, the nebulae were hundreds, thousands, and in some cases millions of light-years away.
In other words, nebulae could not be located within the Milky Way.
But where else? If the Milky Way formed the entire universe, how could nebulae exist beyond its borders? Imagine Hubble's reaction as it dawned on him. Nebulae were not clouds of gas or diffuse stars as had been previously thought: they were other galaxies, like the Milky Way, only millions of light years removed, scattered across the heavens, and too numerous to count.
Put yourself in his shoes for a moment. Edwin Hubble’s universe went from being the size of the Milky Way—200 billion stars deep and nothing to scoff at—to the size of billions of Milky Ways separated by countless light-years of empty space.
It’s no surprise that Hubble’s conclusion was met with scorn or dismissed out of hand; even today people have a tough time wrapping their heads around the size and scope of the universe. If our puny minds can barely handle the scope of the universe now, imagine what people in the 1930’s thought!
Our understanding of the universe has come a long way. We started out on a flat-earth located at the centre of all creation, then progressed to a round earth. A while later Copernicus had the gall to propose that the sun—not the earth—was at the center of the universe, which was only partially right. Finally we thought the Milky Way formed the entire universe; now we know it’s just a grain of sand, a speck of galactic dust among billions.
Whenever we think we have a handle on things someone like Edwin Hubble comes along and blows our understanding out of the water. For every difficult question we answer, we expose more questions. Hubble expanded the borders of our universe beyond the Milky Way; could future discoveries expand the universe even further? Could ours be one of many universes?
If we learn anything from Hubble and all the other radical thinkers who dared disrupt the prevailing theories of their time, it’s that we don’t know much and what we do know is subject to change drastically and with little warning.
We may never fully understand the nature of the universe, reality, human consciousness, etc. All we can ever hope for, to paraphrase Carl Sagan, is an ever-improving understanding, not a perfect one.
Edwin Hubble’s contributions helped advance human understanding one huge step forward.