What Causes the Lunar Phases?

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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.

But why?

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. Continue reading

Einstein: General Relativity

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Albert Einstein may have been the genius among physicists, but like all others before his time, he stood on the shoulders of giants.

Einstein did not propose that the sun was the center of the solar system; that idea was already widely accepted when he came around. He didn’t discover elliptical orbits; that distinction belongs with Johannes Kepler.

But Kepler never could figure out why planets orbit the sun in ellipses instead of circles. Even Isaac Newton, who at last identified gravity as the reason we stick to Earth’s surface, couldn’t explain what gravity was—only how it worked.

Einstein provided that explanation with his general theory of relativity. Continue reading

Moving with the Tides

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Have you ever been to the beach?

If you’re from California like me, then I’m betting you have. If you’re from a place that’s not near an ocean and you’ve never been near the water all your life, then I’ll tell you a little bit about the tides.

They happen every day, twice a day. If you find yourself a nice comfortable spot overlooking the beach, you can see the waves come into the shore and then gently roll out again. If you stay for hours on end, you’ll see the water level eventually rise a bit.

And if you stay even longer, you’ll see the water level lower back down. When it’s high, it’s called high tide, and when it’s low, it’s called low tide.

The tides are partially responsible for the myth that the moon’s gravity affects you in some kind of metaphysical way. But this isn’t true at all.

So why do the tides happen? Continue reading

How Orbits Work

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Since Aristotle’s time over 2000 years ago, we have accepted that the moon orbits the Earth. We didn’t always know why, and we didn’t always accept this for the right reasons.

We used to assume that it happened just because we saw the moon move across the sky, and we believed the Earth to be the center of all motion in the solar system. But even when we realized—in the 1540s CE—that the sun was in fact the center of the solar system, the moon kept its place around the Earth.

And rightfully so. Astronomers now know that the moon orbits the Earth based on scientific observation, rather than the “logical” guesses of Aristotle’s time. And we even know why it orbits—gravity, the one force in all the universe we can’t escape.

But I can tell you, the moon’s orbit isn’t a perfect circle, and if gravity were the only reason it orbited, it would crash straight into the Earth. After all, people stay grounded on Earth’s surface because of gravity, and we don’t orbit our planet, do we?

So how does the moon orbit the Earth? For that matter, how does any satellite? Continue reading

Newton and Gravity

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So, the moon stays in orbit around the Earth, right?

Yeah, I thought so. But why? The moon’s orbit is not a straight line, which means it’s accelerated motion (using the physics definition, which is absolutely any change in speed or direction).

And in order for acceleration to happen, according to Newton’s first law of motion, a force has to happen—meaning, something has to reach out, touch the moon, and drag it into orbit around Earth.

Well, that doesn’t happen, last I checked. I mean, it’s not like we have some kind of giant cord connecting us to the moon. How crazy would that be?

So why does the moon orbit the Earth? Continue reading

Galileo and the Telescope

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When you hear the name “Galileo Galilei,” what immediately comes to mind?

If you thought, “inventor of the telescope,” you’re not alone. I also wouldn’t be surprised if you thought “condemned by the Inquisition for believing the Earth orbited the sun.”

But neither of these are true. If you’ve been following my more recent astronomy posts, you probably realize why—in Galileo’s time, people already knew that the Earth moved around the sun.

The idea that he invented the telescope is more understandable…but, again, it’s not true.

So what is true about Galileo, and how did he contribute to our understanding of astronomy? Continue reading

Archaeoastronomy

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Imagine that you’re living sometime around 2000 BCE, give or take a thousand years or so. That’s about 4000 years before our time.

You look up at the sky at night, and see it filled with numerous points of light. Some of them stay mostly fixed, but move mysteriously in circles around the north pole. Others move with the rest, but wander a bit from time to time.

And then there’s the sun, whose brilliant rays light the day. The moon, like the sun, doesn’t seem to follow the path of the lights in the sky. It even changes its shape, and sometimes disappears entirely.

Wouldn’t you wonder if there was some pattern to these otherworldly motions? Wouldn’t you devote time to studying them and seeing if you could predict them? Continue reading

The Eclipse Seasons

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There can be no doubt that solar and lunar eclipses are some of the most fascinating sights for the “naked” eye. (And I say “naked” under the assumption that you know never to look directly at the sun without approved protection!)

Unless it’s during totality. Then you can take those glasses off.

But what I mean is, solar and lunar eclipses don’t require telescopes or binoculars to be seen. You don’t need to use any special equipment. You just need your eyes, and in the case of a solar eclipse, some form of protection—like solar glasses.

You may have noticed that when a solar eclipse comes up—or even a lunar eclipse—it’s all the rage. Suddenly, the media is swamped with safety warnings and calendar countdowns to the big event.

The United States just about lost its mind over the solar eclipse of August 21, 2017. And I have a feeling the next total solar eclipse to pass over the US, in seven years, will be just as dramatic.

But you might also be wondering…how do we know when these incredible sights are going to happen? Continue reading

Solar Eclipse Sights

This is adapted from a post I wrote for the wonderful Momma over at A Momma’s View. For the original version, click here.

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The total solar eclipse is an incredible phenomenon, one that I hope to see myself someday.

It isn’t often that an astronomical event occurs of such magnitude that people of all walks of life from all around the globe are drawn to one measly 65-mile wide strip of land, to crowd in like sardines as they watch the world change around them.

What’s important to realize about a total solar eclipse, versus just an annular one, is that it’s a people event.

Scientists do take this opportunity to study the sun’s corona, an outer layer of gases that’s usually too faint to be seen. But in general, this is an event for crowds to enjoy.

And enjoy it they do. I have never known another event of astronomical significance to populate the web and turn heads like a total solar eclipse.

But what happens during a solar eclipse? What can you expect to see, and how can you protect your eyes from the sun’s damaging rays? Continue reading

The Annular Eclipse

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An annular solar eclipse is…an interesting sight, to say the least.

(I sincerely hope the photographer didn’t fry his camera taking this picture. Enough light from the sun is still reaching us to fry your retina, or damage your optics…)

The annular eclipse is not to be confused with an annual eclipse. When my dad first got excited about it back in 2012, preparing us for the spectacular sight of a solar eclipse in May, I wondered why the heck we hadn’t done this every year before.

The fact is, I’d never heard the word “annular,” so I thought Dad was just wrong.

But in reality, “annular” means something very different from “annual.” Continue reading