FirstLight Astronomy Club

33°29.6'N / 117°06.8'W / 1190 ft.

The Indescribable Vastness of the Universe - Part 1

Gigantic. Humongous. Herculean. Monstrous. Pharaonic. Cosmic. Astronomical. All these are synonymous with huge. All of these are used to describe the size of the universe. But, really, none of them can be used to accurately describe its size. It is so big it needs its own word. 

This week we will try to get some idea of how vast our home is. The next time we get together we will look at the profound philosophical implications of the size of our universe and how some derive from it meaning - or a lack of it.

Let's start at home. The distance to our sun is about 93 million miles. If we could fly a commercial plane to the sun nonstop, it would take nearly 20 years to reach it. 

The diameter of our solar system out to Neptune is over five-and-a-half billion miles. Flying a plane that distance - from one side to the other - would take over a thousand years. And we are only just talking about the planetary bounds of the solar system.

Let's go to the nearest star other than the sun. That would be Proxima Centauri. That tiny star is almost 26 trillion miles away, so far that it is easier to measure its distance in the time it takes light to get there. Light, racing at 186,000 miles per second, takes 4.3 years to get there. Proxima Centauri is 4.3 light-years away. That is just the nearest star!

The other stars we see in the sky are tens or hundreds or even thousands of light-years away. 

The huge spiral collection of stars we live in, the Milky Way, is over 100,000 light-years across, over 60,000 trillion miles. I don't know about you, but it is already way bigger than anything I can even begin to comprehend - and we have not yet even left our galaxy. 

Now we zip through near empty space to another great "landmark" of space.

The nearest significant galaxy to us is the Andromeda Galaxy. That beauty is about 2.5 million light-years away from us. 

From now on we jump millions of light years at a time and galaxy-hop through the universe, farther and farther away, to the farthest reaches of the visible universe. How far will this hopping around get us? About 13 billion light-years out in all directions. And that is as far out as we can see. The universe may be another 10 times bigger than that!

I'll give an example that will try - vainly, I'm afraid - to put it in perspective. If the entire planet Earth represented the size of the visible universe, our planet would be no bigger than... a single infinitesimal atom. 

Our universe is vast. Vastly vast. But does this mean our relative inconceivable smallness is a measure of our worth? Some people think so. We'll look at the philosophical implications of our enormous universe next time. 

Observations on Observatories

This week let's take a little true-false quiz on the great observatories. Regular readers here should be able to get a perfect score. One way or another, don't fret, it's all in fun!

T/F Observatories are built as high up as they are because that brings them ever so much closer to the stars.  

Well, not really. You can technically build an optical observatory any where your little heart desires. In fact, it would be very pleasurable if astronomers could build them in  beach communities instead of thousands of feet up an ice-cold mountain with little air and desert-dry conditions. So, why don't they?

That atmosphere of ours, so absolutely beneficial and perfectly balanced for life on our planet, is anathema to astronomy. The air bounces the all-important light all over the place, causing images - and all other kinds of information - to become distorted. 

Get those telescopes high and dry and cold and you have great, if not comfy, conditions. Put them in orbit around the Earth, above the atmosphere altogether, and the images are pristine. 

T/F The best telescopes at those observatories are the longest ones from end-to-end. 

You'd think so, huh? It seems reasonable. There are some benefits to having longer telescopes, but by far the most important aspect of those big scopes is their width! The big, round mirror that is set up at one end of that great scope needs to collect as much light as possible and reflect it back to the imaging instruments. What can gather and reflect more photons of light - a tiny little mirror or a big one?

Of course, a big one. One of the biggest in the world for decades was our own Hale Telescope on Mount Palomar. It measures a whopping 5 meters across. In the last couple decades, however, it has been surpassed by telescopes with mirrors measuring up to 10 meters from side to side. And there are plans to make one with a set of mirrors totaling 30 meters across!

T/F A mere member of the public can actually visit some of these great observatories. 

Absolutely true! Some, like the Keck Observatory on the island of Hawaii are not exactly user-friendly. They have a small visitor's cage inside the dome from which you can kinda sorta see the great scope. Others, like our Palomar Observatory have one of the best tours of a working telescope going. And of course there are places like the famous Griffith Observatory in Los Angeles which is practically an astronomy amusement park. 

How did you do? Doesn't matter. If you learned something new, we all win. 

Until next time, clear skies!
Temecula Valley High School / Temecula, CA · Some images © Gemini Observatory/AURA Contact Me