No, There Won’t Be Two Moons in the Sky on Aug. 27 [View all]

[pokerfan]

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.

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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.

More: http://www.slate.com/blogs/bad_astronomy/2015/08/11/mars_big_as_the_moon_not_in_2015_or_ever.html