On Monday, August 21, 2017, the Moon is going to destroy the Sun.
Briefly.
But don’t worry, the Sun will return.
For the first time since 1991, the United States will experience a total solar eclipse.
In fact, everyone in North America will get a chance to see some version of this epic
event - 500 million people will see the Sun dim to some extent.
But for the fortunate people on an epic path from Lincoln City on the Oregon Coast, to
Charleston, South Carolina, they’ll see one of the most dramatic and awe inspiring
events of the sky.
If you’re one of the people along that path, and you’ve got the proper eye protection
- make sure you’re wearing proper eye protection - you’ll see a bite appear on the side of
the Sun.
Over the course of over an hour, you’ll see more and more of the Sun disappear, blocked
by the Moon.
At the halfway point, the last remnants of the Sun will be completely covered, casting
the area in darkness.
The Sun’s mysterious corona will appear as a ghostly halo around the Moon, and the
stars will come out.
For a few brief minutes, you’ll experience totality.
And that’s when the eldar Lovecraftian gods will come pouring forth from this eldritch
rift in spacetime, to consume our planet in madness.
Or, you know, maybe not, the ancient scrolls are unclear.
What is clear is that the Sun will return, slowly but surely.
Then there’ll be traffic jams as a huge population returns home, spiritually awakened
by this momentous event.
Will you be there?
I will.
But what’s going on?
What are the underlying geometries that create such a spectacular moment for us to witness?
Address the question: Eclipses are caused because of the orbital
alignments of the Earth, Sun and Moon.
The Earth travels around the Sun, and the Moon travels around the Earth.
When the Moon is in the Earth’s shadow, that’s a lunar eclipse, and when the Moon’s
shadow falls on the Earth, that’s a solar eclipse.
The Earth orbits the Sun at an average distance of about 150 million kilometers, and the Moon
orbits the Earth at a distance of about 385,000 kilometers.
But in one of the craziest coincidences, the size of the Moon and the size of the Sun are
almost exactly the same from our perspective.
The Sun is 400 times bigger than the Moon, but it also happens to be 400 times farther
away.
The Moon is slowly drifting away from the Earth, so in a few billion years, this will
no longer be the case.
The Moon will no longer be big enough in the sky to perfectly cover the Sun.
We don’t get eclipses every month because the orbits of the Earth and Moon are slightly
inclined from each other.
Sometimes the Moon passes above the Sun, other times it passes below.
From the Earth’s perspective, you’ll see the Moon chomp away and block the Sun.
But seen from space, you’ll see a better idea of what’s going on.
The Moon casts a shadow down onto the surface of the Earth.
For the 2017 eclipse, the shadow appears out in the Pacific ocean, and then races across
the surface of the planet.
For anyone actually caught in the shadow, they’re able to see the complete eclipse,
where the Moon fully blocks the Sun.
For everyone else on either side of the shadow, you see a partial eclipse, where only a chunk
of the Sun is blocked by the Moon.
Every year, there are usually a couple of total solar eclipses, visible from somewhere
on the planet, and there are larger chunks that can see a partial eclipse.
The Earth follows an elliptical path around the Sun, and the Moon makes its own elliptical
path around the Earth.
So the size of both the Sun and the Moon can be slightly different sizes in the sky.
When the Sun is at its largest, and the Moon is at its smallest, that’s an annular eclipse.
The Moon doesn’t completely cover the Sun and create the special event of a total eclipse.
In a moment, I’m going to give you some recommendations on how to best watch and photograph
this (and any solar eclipse), but first I’d like to thank:
Gordon Grant David Connor
Jen Scott
And the rest of our 759 patrons for their generous support.
If you love what we’re doing and want to get in on the action, head over to patreon.com/universetoday.
If you are planning to witness the Great American Eclipse with your own eyes, you’re going
to want to get the most out of the experience.
But you also want to be safe.
If you look at the Sun, even briefly, you can permanently damage your eyes.
You’re absolutely going to want some kind of protection.
There are ways that you can observe the eclipse indirectly, like using a pinhole to project
an image of the Sun onto a piece of paper.
That’s okay, but you’re really just going to want to look at it.
Right now, today, while there’s still time, go online and order yourself a set of proper
eclipse glasses.
Any listing should say that they’re CE and ISO certified, for safety.
But even so, you shouldn’t need to pay more than a few dollars for each pair.
You can’t use regular sunglasses, no matter how cool they make you look.
Then you’re safe to watch the Sun directly through the glasses.
If you want to take things to the next level, you can project an image of the Sun onto the
ground or a piece of paper with a Sun funnel.
I’ll put links into the description for how to build one.
You can also project the light from the Sun through a pair of binoculars or a small spotting
scope onto a piece of paper.
This is dangerous, however.
For starters, if you look through unfiltered binoculars at the Sun, even for a second,
you’ll be getting a magnified light in your eyes, and you’ll be permanently blinded
in moments.
It’s also hard on the optics of the binoculars or telescope.
You can can melt the glue and plastics inside, and pretty much destroy it.
So, be careful.
It’s best to get your hands on a solar filter.
There are some good manufacturers that produce high quality solar filter material that you
can put over the front of your telescope or binoculars to block most of the light and
allow you to see what’s going on.
But really, I just recommend you wear a set of eclipse glasses and call it a day.
Next up, taking pictures.
If you’ve got a good camera with a telephoto lens, you can take some cool photos of the
eclipse.
Once again, you’ll want to be really careful, since the light can damage the optics of your
lens and camera.
Use a long lens, like 300mm or greater, and do a bunch of tests with the Moon before eclipse
day.
Especially figure out your focus point and put a piece of tape on your lens so you’re
not fumbling around when it’s happening.
But I’ve also talked to a few people about what to do, and here’s the advice I heard
time and time again: if this is your first total solar eclipse, don’t bother trying
to take pictures of it.
Just appreciate the experience without the stress of trying to capture it with a camera.
Take pictures next time, once you’re hooked.
That’s what I’m planning to do.
As the partial eclipse begins, you’re going to see the landscape darken around you, so
slightly.
Less and less of the Sun is providing illumination.
As totality approaches, you might even be able to see the shadow of the Moon racing
across the landscape towards you.
Moments before totality, there’ll be tiny beads of sunlight at the edge of the Moon
as it blocks the Sun.
You’re seeing sunlight slipping through tiny valleys in between mountains on the Moon.
Now that totally blows my mind.
Finally, we’ll reach totality, and for a few brief moments it’s safe to look up at
the Sun without any eye protection.
But be careful, because after just two minutes of totality, the first spots of sunlight will
appear at the opposite edge, as the Sun begins to return.
The entire space community has been nagging you for the better part of a year to go and
see this amazing eclipse, so I really hope you’ve got something fun organized, and
you’ll get a chance to see it with your own eyeballs.
But even if you don’t, you’re in luck.
There’s going to be a second eclipse passing through the area in April 2024, giving most
of North America a second chance to witness this amazing event.
Are you planning to watch the August Eclipse?
Let me know your plans.
And if you’re watching this after the eclipse already happened, let me know your experience.
How did it go for you?
Are you hooked?
In our next episode, we consider all those asteroids hurtling around in space.
Who’s keeping an eye out for them, and what strategies can we use to prevent an asteroid
hitting Earth?
Time again for a playlist.
In this episode we look at a recent episode of Astronomy Cast.
You know, that other thing I do with Dr. Pamela Gay, where we help you prep for the eclipse.
Then some new videos from NASA all about the eclipse.
Finally, a video from PBS Spacetime.
That starts right here.