So, by now, you’ve probably heard that Mars is going to look as big as the full Moon tonight. It’s a very popular Internet meme these days, sent around by people who think it sounds cool but never stop to think about the physical situation that such a story represents.
Epic fail on their part. Don’t let it be one on yours.
Think about it. How far away is the Moon? I’ll tell you — it’s (on average, depending on where it is in its orbit) about 384,000 kilometers away from us.
Now, how far away is Mars? I’ll tell you that, too. When Mars and Earth are at their closest points in their orbits, Mars can be about 55 or 56 million kilometers away. That makes it look like a reddish point of light from our vantage point here on Earth.
Okay, now compare 384,000 with 55 million. BIG difference. It’s a big enough difference that Mars will always, always, always appear as a point of light in our sky. And the Moon will be brighter and bigger and look like… the Moon.
If Mars were to look as big as the full Moon in our skies, we would have BIG problems. Bigger than worrying about how it would look in our sky. Let me put it to you this way: if it were as big as the full Moon in our sky, we’d be looking for a way off-planet before the tidal forces broke both worlds apart. NASA explains it all pretty well here.
So, don’t believe the meme — don’t let some foolish person’s misunderstanding of science and planetary orbital mechanics live rent-free in your brain.
Instead, head out tonight and check out Mars and Venus after sunset. They look lovely, without all the need for breathless Internet/Web hype.