Astronomy Made Simple

What We Know

I love astronomy. Partly from reading a lot of science fiction as a youth, and partly because you get to make most of it up. All you really need to know is a little about heat, light, and gravity—and you already know about those—some of the simplest concepts of geometry (a sphere and a triangle), and the structure of the simplest atom imaginable.

Here’s what we know. Hydrogen is the simplest atom, consisting of a single proton with a positive electrical charge at its core and a single electron with a negative charge (bouncing around it in a crazy quilt orbit because opposites attract, but like your last boyfriend/girlfriend, it’s going too fast to get sucked in. You don’t need to know that though). Turns out some strange thing associated with the Big Bang (whatever That was) or God (whoever He is) made hydrogen. After that—the Universe! Yep, that’s it. That’s how it all happened.

Oh yeah, one more thing—gravity. Mass attracts mass, and the more mass you have together, the bigger the attraction. That’s gravity. It’s a constructive feedback loop. Whoever has the biggest collection keeps getting a bigger and bigger share. You know, the rich get richer, and the poor get poorer, or in this case gobbled up by the rich. The more mass you get, the tighter that whole little ball of hydrogen gets packed. The closer the packing the hotter things get.

That’s the actual definition of heat. The closer things are, the more they rub against each other, like rubbing your hands together to keep warm. At 100 million degrees celsius (or Kelvin, but what’s 325 degrees when you’re talking 100 million?), the hydrogen atoms bounce into each other hard enough to squish together. Two hydrogen protons get fused together like Superman pushing the positive ends of two super magnets together with an unstoppable force, no matter how hard they want to get away from each other. Their two electrons both start dancing happily around that nucleus of two protons while frantically avoiding each other like they’re hopscotching around some whacked-out 3-dimensional checkers board, and you have Helium with two protons and two electrons somehow happy together now that the positive and negative charges balance out again. All that crazy force you used to push things together now has to go somewhere. (That’s what Newton says. Just trust me on that one.) That process generates enough heat to satisfy Einstein’s crazy e=mc2 where e is energy generated, m is the amount of mass involved and c is the speed of light, and you know what a huge number that must be when multiplied by itself. That’s a lot of heat. Beyond imagination—at least beyond mine anyway.

So why didn’t all the matter in the universe gather itself back together and go in for another Big Bang? Here’s the thing about all that heat. Heat wants to expand. It just wants to explode like a two year-old throwing a temper tantrum. But the star’s mass is big enough to keep the mass together, and just let the heat and light escape. So the star gets stable at that point. It’s full, and doesn’t need to go looking for more mass to gobble up. It’s already eaten everything that was small and close enough to eat. A neighboring star has eaten up all the loose hydrogen that’s closer to it, and neither star is big enough to pull in another star that’s too far away for gravity to be that strong.

A stable star, like our sun currently is, generates enough heat to keep from collapsing further in on itself, and has enough gravity pressure to keep heating things up enough to keep generating the hydrogen fusion furnace. It’s all a fun balancing act like a juggler on a unicycle, until it runs out of hydrogen. When that happens, the fire isn’t strong enough to overcome the gravity anymore, and the star starts to collapse. When it collapses however, it generates even more heat and pressure by pulling everything closer. That starts to get things even hotter. Turns out you get hot enough, the helium atoms start to fuse, creating atoms with even more protons, and generating even more energy! You’ve heard of novas, supernovas, and such, right? Well, that happens, or, if the star isn’t big enough for that to happen, it just blows up into a gas giant and what’s left shrinks into a white dwarf.

Isn’t astronomy great? You get white dwarves, gas giants, black holes…. It’s like a Tolkien novel. Sorry, where was I?

There’s one more thing that we know. How far the planets and stars are away from us, and, by deduction, each other. That’s where we get into geometry. Surveyors figure out how far things are from them by a process called triangulation. To make it simple, they stand in one spot and measure the angle they have to look through their little telescopes to see some far-away landmark. Then they pace off enough distance and repeat the process, looking at the same thing. That gives them 2 angles and the length of one side of the triangle. That’s called the parallax. From that, they can calculate the length of the other two sides of the triangle, which happens to be the distance they are from that landmark they were looking at.

As it happens, we know how far the earth is away from itself at half year intervals in our orbit. Don’t ask me how, just trust me on that one. So that straight line distance from one part of our orbit to the opposite side is like the baseline the surveyor paced off. So we measure the angle at which we see each star in each observation 6 months apart and can calculate the star’s distance from us. Simple, easy, geometry.

Only there’s a problem. If something is really, really far away, it looks like it has the same angle from each observation. It becomes a straight line instead of a triangle. So, in this way, we know the distance of ourselves from about 100 stars, but no more.

That’s what we know. You can stop here if that’s all you care about.

What We Make Up

Now comes the fun part—making things up. You didn’t think all those astronomers are going to leave it at that, throw their hands up, and say that’s all we know, did you? You’re human. You know that what humans don’t know, we try to make up. So astronomers will tell you how far away each star is even if they’re just guessing. Sort of. Astronomers are scientists after all, so just making things up seems like cheating. Instead they start trying to Sherlock Holmes their way to justify their guesses.

So how do we “know” how far away the other stars are? The beginning goes back to Newton once again. He famously passed sunlight through a prism, and it turned into many different colors of light—what we now call the spectrum. You can hold up a white strip, and where each color falls on that strip will be a little different, enabling you to see what kind of matter caused that light energy to be emitted.

Modern scientists and engineers have even created machines called mass spectrometers that bombard unknown substances with energy and capture the emerging light that results, enabling us to tell what molecules are in that substance based on the resulting spectrum. So that trick enables us to see that among the hundred stars whose distance from us we know, they are slightly different in composition based on how big they are and where they’re at in their lifecycle of burning up their fuel, indicating their age. So now astronomers have classified stars into a few distinct types, each type having a certain level of brightness and a certain identifying spectrum.

That led astronomers first to the standard candle method of gauging a star’s distance from us. You see, if you know a candle emits a constant level of brightness, it will appear dimmer the farther away from your point of view it is, so, with careful measurements, you can tell how far away from you it is, based on your perception of its brightness. That leads to guess one. You assume all stars of the same type are the same brightness, so, based on that assumption, if you see a star of that type, you can calculate how far it is away from earth based on how bright it looks to us. There’s a lot of math involved depending on the magnification of your telescope and so on, so it makes astronomers feel like they’re being precise. If you have to do a lot of math to get your result, it must be true, right?

There’s one more trick that astronomers have found essential. It’s called the Doppler effect. If you’re musically inclined, and you’re approached by a fire engine with its siren sounding, you’ll notice a discernible rise in pitch as it approaches you, and a complementing change in the opposite tone as it swiftly moves away from you. Any wave phenomenon like sound or light demonstrates this property. With light, you can see this in the spectrum. The red line and the blue line are the same distance apart, but where they are is different depending on whether they’re coming closer to you or moving away from you. The distance of this shift is proportional to the speed of the source of the light as it is moving towards or away from you. The astronomers noticed that shift in the spectrums of the stars they observed and figured it was proportional to their speed coming at us or moving away from us.

Funny thing about that. All the stars were shifted in the same direction, indicating they were all heading away from us, no matter which direction we look! That fact helped convince astronomers of the Big Bang Theory. If everywhere we look, everything’s speeding away from us, it’s like we’re all on the surface of a balloon that keeps being blown up and getting bigger. If the universe is like the surface of a balloon, then the paint dots on the surface of that balloon that are farther away are moving faster away from us than the ones much closer. Feel free to try it yourself. Blow up a balloon halfway, sprinkle little dots of paint on it, and resume blowing it up. You don’t even have to do any math, you can see it with your own two eyes.

In any case, that leads to assumption number two. The further the light spectrum of a star is shifted, the faster it’s moving away from us,and therefore the faster a star is moving away from us, the more distant it is from us. So now all we have to do is collect the spectrum of each star, measure the amount the spectrum is shifted from a normal stationary light source, and, voila, we think we know how far it is from us.

So that’s two assumptions and a lot of math. You see where I’m going with this making stuff up assertion? No? Keep reading. There was a famous astronomer named Hubble. Based on these assumptions, he calculated how fast everything in the visible universe was moving away from everything else. That value was named the Hubble Constant, after him. Of course astronomers sometimes jokingly referred to it as the Hubble Variable because the value kept changing, the better our telescopes got. In any case that number allowed him to calculate when the Big Bang happened (sometimes called the age of the universe if you prefer).

Astronomers have tried to figure out if the universe will have enough gravity to start falling back in on itself once the energy from the Big Bang diminishes. To do that they calculated the mass of everything we can see. When that wasn’t enough to account properly for the speed of the expansion (based on the good old red shift of course), they decided there’s something called dark matter basically stuff you can’t see. Now that sounds plausible. There could still be hydrogen atoms floating around in the vacuum of space. Like tiny so-called no-see-ems (tiny flying insects that bug people in the Southeast US), they aren’t exactly invisible, just too small for us to see. Despite having no actual evidence for that, we have good reason to think we wouldn’t have any evidence if it is true. That’s the kind of evidence that gets you thrown out of court pretty quickly.

Even so, the calculations weren’t coming out to show what made sense to the astronomers, so they decided there was something countering the pull of dark matter. They called this mysterious thing dark energy. Quick, put your hands against your cheeks to keep your head from spinning. How do we know about dark energy? The same way we know about dark matter. As someone said, “Absence of evidence is not evidence of absence.” So that means we can just make up anything we want, right? Just as long as we cloud it in a mountain of indecipherable equations to be all professional and sciency about it.

Currently, astronomers have a problem they’re not talking about. Their oh so precise equations tell them that the new Webb telescope can see so far it can see almost to the beginning of the universe. The first problem I have with that is that, if that’s true, then you should see the same image in every direction, right? That may sound odd, but, think about it. If the Big Bang Theory is true, the universe must have been much smaller 13 billion years ago. That’s hard to wrap your head around, but it’s an obvious conclusion from what astronomers believe, even if it doesn’t seem to occur to them. I’m sure Steven Hawking can come back from the grave with some more lovely equations to explain that.

The other problem that astronomers are only talking to each other about is, if all they’ve laid out is true, the spectrums from stars 13 billion years ago should be insanely shifted. But they kind of look the same. Whoops, that whole pyramid of logic is now starting to look more like a game of Jenga.

Don’t worry though, I’m sure by the time the public hears about this problem, we’ll also hear about some distorting gravity lens effect that shines everything right back at us if we look too closely—with a lot of fancy equations to prove it of course.

See why I love astronomy?

One response to “Astronomy Made Simple”

  1. Great synopsis Frank! Good to see you are still writing my friend! I’d say more but I’m still working and have to go to work!


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