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SYFY WIRE Bad Astronomy

No, There Won’t Be Two Moons in the Sky on Aug. 27. Or Ever. Ever Ever
Ever. Ever.

By Phil Plait

Oh for Ares’ sake. This again?

Yup, it’s August, and that means it’s time for the annual “two Moons in the sky” Facebook hoax. Maybe you’ve seen it; it starts to go viral around this time of the year. It’s also sometimes sent around with a note saying, “Mars will be as big as the Moon.”

Let’s get this out of the way immediately: No. It’s baloney. It isn’t true this year, it wasn’t true in 2013, or 2009, or 2008, or 2007, or 2006, or 2005, or even when it first began back in 2003.

It can never be true. Mars can simply never get close enough to Earth to be seen as more than a dot by the eye. Despite that, this hoax gets spread all the time—I’ve already been getting questions asking whether it’s true.

Here’s the actual claim going around this year:

The caption says,

12:30 Aug 27 th you will see two moons in the sky, but only one will be the moon. The other will be Mars. It won’t happen again until 2287. No one alive today has ever witnessed this happening.

Well, at least one part is true: No one has ever seen this, because you can’t. Note too this is the exact same Photoshopped picture used in 2013. Blarg.

Here are the facts. Mars is on an orbit outside of Earth’s from the Sun. It’s at its closest when the Earth passes it on the inside. Both orbits are elliptical, so sometimes they get closer than other times, but really the closest they can be is roughly 55 million kilometers (35 million miles) apart. That’s more than 100 times farther than the Moon. Given that Mars is roughly twice the physical size of the Moon, that should set off alarm bells in your head right away. At best, Mars is still only 1/50th as big as the Moon in the sky! On Aug. 27 the Moon will appear 530 times larger than Mars.

Look at the photo at the top of this article. I actually took an image of Mars and scaled it to one of the Moon as they will both look on Aug. 27. Not so amazing, is it?

It’s even worse: Mars doesn’t get very close to Earth this year at all. The last perigee (closest approach to Earth) was in 2014, and the next one won’t be until next year in May. Also, on Aug. 27 they will literally be in opposite parts of the sky, 175° apart. When one rises, the other sets, so in realistic terms they won’t even be in the sky at the same time for more than half an hour.

No one really knows why this hoax got started back in 2003. I know how; I described it: A real note got spread around saying that through a telescope at 75X, Mars would look as big as the Moon does by eye. That part is correct, but it got changed by someone to the current “Mars as big as the Moon” silliness, and now I think some goofball or goofballs spread it around every year, knowing people will continue to spread it without checking.

It’s frustrating to debunk this every year. It’s not so much the act of doing it as having to do it; I wish people understood the sky well enough to know such an event is impossible. I don’t fault anyone for that, really; people are busy and have different interests and so on.

But in this country in particular and worldwide in general, critical thinking isn’t exactly encouraged. Generally not by schools, not by governments, and not by religions, essentially nowhere are children taught these basic skills in a rigorous way. It does happen, of course, but it’s not exactly widespread. If we did teach kids how to think, not just what to think, then maybe a lot of these hoaxes would go away.

And not just inane, innocuous pranks like this, but also serious problems with thinking, like denying the benefits of vaccines, denying the reality of global warming, or believing the Earth is 6,000 years old. These do in fact have serious repercussions.

So I will continue to debunk nonsense like the Moon/Mars thing when they pop up, because every time we chip away at our ability to think critically we lose a piece of our ability to deal with the world as it is, and we actively make it worse.

If we, as a species, knew better how to think, a lot of the very large problems we face today would never have occurred in the first place. That’s a world I’d very much like to live in.

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