Bringing the Universe to Your Classroom!

Saturday, November 2, 2019

The Telescope, and the Center Of The Universe

In the beginning, there was "us" - and, just us. (So we liked to think)

(fast-forward a few hundred thousand years...)

Around the Middle Ages, it was discovered that we inhabited a "world" - a round, spherical one. And so now, we and our world were all that there was.

But, a little later, in 1610, a physicist named Galileo Galilei, using a new and revolutionary optical instrument called a "telescope", discovered that the moon, Saturn, and Jupiter - were not just dots of light in the sky, but rather, they were, actual, "other" worlds. Not only were Jupiter and Saturn planets, in their own right, but they possessed satellites, as well. Galileo, and then others, noticed that these satellites were orbiting around their host planets - resembling miniature Solar Systems.

None of this new and revolutionary information would have been revealed, had it not been for a new and revolutionary instrument - Galileo's hand-made, tiny, 2-inch diameter instrument - the refracting telescope. (This new revelation caused a lot of problems - both, for Galileo, and for society, in general - because, just maybe - there were "others" on these "other worlds")

While Galilei did not invent the telescope, he very successfully built one and used it for astronomical observations. This image shows two telescopes in his possession. Image Credit - DPA-Picture Alliance.
While Galilei did not invent the telescope, he very successfully built one and used it for astronomical observations. This image shows two telescopes in his possession. Image Credit - DPA-Picture Alliance.

In 1783, amateur astronomer, William Herschel, made the discovery that all of these "other worlds", were, actually, a conglomeration of worlds - an "island universe", which we, today, call the "Milky Way" galaxy. Using one of his - very large, for the day (40") - reflector telescopes, Herschel was able to, roughly, determine the general shape of the "Milky Way" (something like a double-convex lens, or, the way I like to imagine it: two, inverted Frisbees!). It was apparent then that, we reside in some, isolated structure of stars, and we named our isolated home galaxy after the dim band of cloud-like light that splits the sky into two "hemispheres". (This band of diffuse light, or the "Milky Way", can still be seen from some places in the world, so I understand).

William Herschel's sketch of the Milky Way Galaxy.
William Herschel's sketch of the Milky Way Galaxy.

Sometime later, comet-hunter, Charles Messier, using his own, small, hand-made reflecting telescopes had found that the sky contained, seemingly, hundreds of small, cloud-like patches of light, similar to the milky band that circled the sky - ranging in size, up to, just larger, than the full moon. It was thought that these tiny "fogs", were just that - some type of cloudy matter, nearly, randomly distributed about the sky. All that Messier knew, was, that they were not the "comets" he was searching for. And so, they stayed, just fogs.

Then, in the 1920s, a debate took place, now known historically as the "Great Debate", on the nature of these luminous patches of fog. The debate focused on whether these structures were portions of our own galaxy, or, whether they were external structures. Around that time, a slightly pompous - but, generally brilliant astronomer, Edwin Hubble, had made another revolutionary discovery that ended the debate, altogether - these luminosities in the sky were not cloudy in nature. Hubble was able to resolve these hazy patches into individual stars, using the Hooker telescope. It turned out that they were actually, distant "island universes" (galaxies) in their own right!

In a spectroscopic analysis of the motions, of the millions of other galaxies that lie beyond our own island galaxy, the Milky Way - nearly the entire mass of the universe is receding into the distance - i.e. apparently, away from us. What's more, the velocity of any given galaxy's recession, is proportional to its distance - i.e., the farther away the galaxy is, the faster it is receding into the "background"! This situation is what produces, what's called, the "red-shift effect" - light's, own version, of sound's, "Doppler" effect. The result is that the spectra of those receding galaxies are shifted towards the red (longer wavelength) end of the visible light spectrum; in the same way that the tone from, say, a passing vehicle's horn, in a fluid, continuous way, drops in pitch as it passes by us and on to a direction that carries it farther away from us.

All of this is due to the general expansion of the universe, as a whole (hence, the "Big Bang", or, "Great Expansion" event, when began universal expansion). This condition was discovered by Edwin Hubble, back in 1929. It was his observations, now, using the 200" reflector at Mt. Palomar that revealed that the universe was in a general state of expansion. Only, a very few galaxies, appear not to be receding from us. This includes, the 25 or so, member galaxies of what is called, the "Local Group", of relatively nearby galaxies, and the two satellite galaxies of the Milky Way galaxy, called, the Large, and the Small "Magellanic Clouds" (the LMC, and SMC, respectively), as well as the next, nearest, large spiral galaxy similar to our Milky Way galaxy, the Andromeda galaxy, or, M32. That galaxy is so nearby, cosmologically speaking, that it can just be detected in a clear, dark sky with the unaided eye. The galaxy lies in the constellation of Andromeda and it is a prime target for astrographic imaging, or, astrophotography.

But, from our own galactic island, it appears as if the Great Expansion event, itself, took place at the position of the Milky Way galaxy! And to make matters worse - this expansion is undergoing an apparent acceleration - one that increases, proportionally, as its distance from the Milky Way! Could it be that we are in some, privileged location, in relation to the rest of the universe? Can this really be so?

(I was going to have some fun with this, but I won't!)

The answer is, of course: No, it can't.

From the beginning of human civilization, man has revered himself to be the pinnacle of creation - whether he placed himself at some, centralized position, either on the Earth, or whether he placed the Earth, itself, at the center of - at first, the Solar System, and then the Milky Way galaxy - both of which were dead wrong. By small gradations, he has slowly discovered that there is no true center to the universe, nor is there any, true, up or down. Today, we know that our "island universe", is only one of the billions of other island universes - revealed to us, by the power of an inherently, very simple, optical marvel - the telescope.

Because of the telescope - we've not only revealed the nature of particular objects in the universe but also, general ideas as to the nature of the universe, on the whole.

Dale Alan Bryant

No comments:

Post a Comment