Monday, July 19, 2010

Why won't it DIE???!!!!!

Oh crap! It's back!

Maybe recently, an email came across your inbox declaring that this August, Mars would be as big as the full moon in the sky. A friend of mine who works in an astronomy store in Toronto reports that he even recently got a customer inquiry from someone who wanted to look at Mars then.

After seven years, you'd think the Mars Hoax would have run it's course.

Just in case you aren't sure what I'm talking about, let me clarify. The origin of this thing goes back to 2003 when Mars did, in fact, have a remarkably favourable "opposition." This is something that happens with every planet beyond Earth when sun, Earth and planet form something of a line in the sky. Think about watching a race from within the circle. As two runners run in their individual tracks, the inside runner appearing to go faster because he has a smaller circle to run, both are going to appear to 'line up' occasionally.

For us, this simply means that the planet will rise as the sun sets and vice versa. We see the planet for a considerable amount of time either side of this so it only means, for a brief period of time, the planet is at its biggest and brightest in our sky. This year, that happened for Mars on Jan. 29.

For Mars, it's closest approach is about 35 million miles! To give you an idea of distance, the sun is 93 million miles. The moon is about 250,000 miles. You'll see why this is important in a minute.

First, let's talk about Mars's orbit. It's weird! More specifically, it's highly "eccentric." Most orbits are somewhat "egg-shaped" but for Earth, Venus and several others, that eccentricity doesn't amount to more than a few per cent out-of-round. Mars is different. It's eccentricity actually amounts to something like 30 per cent. That means the Earth-Mars distance can vary wildly between 35 million miles - like what happened in August 2003 - and almost 100 million miles. That's a difference of nearly 80 millions miles!

And the variation between most favourable oppositions? Well, between 2003 and the last most favourable when Mars appeared it's largest in a telescope....about 60,000 miles.

Okay, keep that in mind. Here's why...even when Mars is at its closest, it still only appears as a star-like dot in the sky. Granted, in 2003, it was a very bright dot. But still, a dot.

In order to actually cover as much sky as the moon does, Mars would actually have to be considerably closer. Say, about 800,000 miles away! That's close! Scary close! As in, not sitting under the romantic ochre glow. More like "Oh God, Oh God, we're all going to die!" close! If Mars were that close, life on Earth would be a very unpleasant thing. The tidal forces between these two bodies would be considerably larger than they are between the moon and Mars (remember, we're talking not just angular size but volume and mass!)

So now you know why not to take too much stock in the Mars hoax. Of course, if you're still inclined to buy a telescope from my friend, go right ahead! He might even tell you about some interesting things you actually can see!

Oh, and just so you know, on Aug. 23, Mars will be close to the sun and low on the western horizon near Venus.

Clear skies!

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