We see it almost every night of our lives. For thousands of years, the greatest philosophers and astronomers alike have watched its face change and wondered why.
Step outside and observe the moon every day for a month and you will notice something fascinating. Over the course of the entire month, the moon will go through an entire cycle of phases—no more, no less.
The phases of the moon are something I’ve talked about before, but I wanted to spend some time on a few common misconceptions this time around and show you the truth behind the lunar phases.
I remember something my ninth grade advanced biology teacher told our class. It was essentially a story about an invisible dragon.
Now why, you ask, would a biology teacher teach us about an invisible dragon?
Her message had nothing to do with the dragon, and everything to do with the lengths one of the story’s characters went to in order to disprove the dragon’s existence. Her intention was to help her students distinguish between evidence and belief.
On a broader level, her intention was to show us the difference between science and religion. See, back when I was in eighth and ninth grade, there seemed to be a lot of controversy in schools surrounding science and religion.
Teachers of students that age felt the need to preempt their entire class with a disclaimer—that students were still free to believe whatever they believed, no matter what science the class taught.
Most teachers just made a general announcement on the first day. But my biology teacher told us this story about a dragon—and it continues to impact me to this day.
If this quote really is from Cecilia Payne, then she had the right idea—at least for a female astronomer in the 1920s. Women in science back then faced an uphill battle to get recognized for any discoveries they made, and Payne was no different.
What’s so special about Payne, you might ask? Well, she wasn’t just one of the many “unsung heroes” of modern science. She was the one who figured out what stars are made of.
Yeah, that’s right. She sent a probe to the sun, collected a jar of star stuff, and brought it back to her laboratory…
Um, no, not really. It wasn’t that easy.
In fact, it was very difficult. She had far too many roadblocks than were fair. But she wasn’t out for money or recognition. She was just in it for the science. And science was what she got…
Astronomers know that if white light passes through a prism and is bent, it’s separated out into its component colors—the colors of the rainbow.
Astronomers also know that when light interacts with atoms, the building blocks of the universe, the atoms absorb photons of light and reemit them—but in a different direction.
Put these two bits of knowledge together, and astronomers now have everything they need to understand spectra (the plural for spectrum).
A spectrum is something I’ve covered in previous posts. In astronomy, it means the wavelengths of electromagnetic radiation spread out so we can analyze them individually. And it’s an astronomer’s most valuable tool.
So, what exactly is a spectrum, and how can we use it to analyze radiation from space and learn more about the universe?
Everything we know about space comes from radiation.
Now wait just a moment here. That statement explains how astronomy is such a successful field of science—it’s based entirely on the information we can glean from radiation, after all. But how does that make sense?
I mean, it’s one thing to study radiation. It’s quite another thing to study matter, the “stuff” in the universe. How does one have anything to do with the other?
Well…that’s where atoms come in. Radiation does, in fact, have a lot to do with the “stuff” it comes from. And if it weren’t for that basic principle, astronomy as a science wouldn’t work.
Thankfully for astronomers, it does. So what’s the secret, then? What does radiation have to do with matter?
The Hubble Space Telescope is one of the most famous telescopes in the world.
Oops, excuse me—one of the most famous telescopes built.
Hubble, after all, is certainly not in this world. Unless you call the universe the “world,” it’s about as far from being in this world as you can get. It’s in space.
Hubble isn’t that different from an ordinary, ground telescope. It’s only as big as a bus. There are bigger optical telescopes. Its mirror is 2.4 m across—hardly an achievement by modern-day standards.
Palomar Observatory, which was the biggest telescope in the world when it was built, has better optics than Hubble, meaning its images are a bit crisper.
But that doesn’t keep astronomers from continuing to use Hubble. In fact, if you want to use Hubble, you have to get in line—it hardly has time to complete all the projects astronomers ask of it, even observing the night sky 24/7.
It’s a radio telescope, the largest in the world. It’s so huge that a normal support system can’t support its weight. So it’s basically suspended between three mountaintops. It’s 300 m across, which is 1000 feet. It’s huge.
This is the kind of construction endeavor that radio astronomers must try if they want to get much detail from radio waves. The radio wavelengths of the electromagnetic spectrum are really, really weak. You need huge telescopes to collect enough.
But, as ever, astronomers face the same basic problem: money.
Huge telescopes are expensive. It’s unfortunate for astronomers, but true—just think of the cost of labor of basically burying a whole valley under a radio dish.
Astronomy is a labor of love, and radio astronomy is no different.
As I covered in my last post, radio astronomy deals with the longest wavelengths of the electromagnetic spectrum (a spectrum that includes visible light). Radio waves are not sound waves. They’re radiation just like visible light, infrared, and ultraviolet.
I’ll prove to you that radio waves can’t be sound waves. We get them from space—that’s why there’s such a thing as radio astronomy. But there’s no sound in space. Why? Sound requires something to pass through, and space is a vacuum.
So, we’ve established that radio waves are just another form of electromagnetic radiation. And astronomers love to collect any form of electromagnetic radiation. We can’t touch the stars ourselves, so it’s our only chance at learning about the cosmos.
Why? Because just about everything in the sky emits electromagnetic radiation.
Everything except black holes and a couple other things…but those are topics for another day.
But electromagnetic radiation isn’t easy to collect. And radio waves are especially hard.
Yeah, it’s a bit bigger than your average radio antenna.
That’s because its job isn’t to direct radio signals to your house. It’s a radio telescope, and its job is to collect as many radio signals as it possibly can—from outer space, not from a radio station.
Radio astronomy is a tricky business. It has its advantages over visible astronomy—it certainly works better for interferometers—but radio signals are so weak, they’re hard to detect and study. Which is why you’ll never see a small radio telescope.
So, how do astronomers manage to collect and study radio emissions from the cosmos?
Okay, maybe you have…online. What with the spread of the internet these days, I’m guessing that at one point you have seen something like this on a page of image search results.
That’s the thing, though. You’ve seen this incredible phenomenon on a computer screen. But have you ever seen it through a telescope?
Don’t worry—if you haven’t had an opportunity to look through a telescope, you’re not missing out. You’re not going to see the Sombrero Galaxy above in all its photographed glory just from looking through the eyepiece of a telescope.