For those of you who are connected to the astronomy education world, it’s that time of year: the “Mars will be as big as the Moon” e-mail is going around again. The short answer is “Nope.”
Mars and Earth regularly pass “close” to each other, but not that close. Astronomers get excited because we’re at “closest approach” or “opposition,” so our ground-based telescopes have a better view of Mars. Will you see a difference without a telescope? Not really, Mars may be a little brighter or a little redder, but it will still look, to your eyes, just like a star.
This e-mail hoax started in August 2003, when Mars was actually very close, astronomically speaking. It was a mere 35 MILLION MILES AWAY. Since then, the e-mail has been going around every August, with the date slightly changed.
In 2007 Mars will be at opposition in December, not August, and it will still be 55 million miles away.
Here is what some scientists are saying:
Dec 18, 2007- Closest approach of Mars and Earth (0.589 AU = 88.42 million km). Apparent diameter of Mars is 15.88″ (seconds of arc). The apparent diameter of the Moon is about 1/2 degree which is 1,800″ (seconds of arc). So, will Mars look as big as the Moon? Not even close. [1 degree = 60 arcminutes – 3,600 arcsec]
-Alan Gould, UC Berkeley
The Moon and Mars could not look alike in the sky, BUT an astronomer might say that that through a telescope at 100X, Mars _through a telescope_ might look almost as big (1,588″) as the Moon to the unaided eye (1,800″). Perhaps the part of the comparison about looking through a telescope was lost, and media types looking for a hype to hang a story on ran with it. That’s the only explanation I can give about the recurring story about Mars being as big in the sky as the Moon. This story reappears at almost every opposition of Mars, especially the really close ones.
– Steve Berr
Let Them Down Easy:
So what do you say to someone who is excited? Cover each of these topics:
- Validate the excitement
- Point out something related that will be cool
- Correct the misconception
- Invite them to view/look up something real
“So did you hear about Mars being as big as the Moon?”
“Yes! I agree, that would be awesome. You know, December is really going to be the best month to view Mars though, maybe we could take out a telescope together? Unfortunately, it’s still really far away, so it won’t ever look as big as the Moon. Also, if you want to see something cool sooner, on August 27 there will be a lunar eclipse, and the Moon itself will look red!”