ramblings from the noisedoctor

August 12, 2006

Mars as big as the Moon?

Filed under: space — noisedoctor @ 7:06 am

Have you seen this email? My lovely, supportive, and intelligent wife came home from work all excited, telling me that tonight that Mars was going to appear as big as the Moon. Wow. Sounds incredible, huh?

The Red Planet is about to be spectacular! This month and next, Earth is catching up with Mars in an encounter that will culminate in the closest approach between the two planets in recorded history. The next time Mars may come this close is in 2287. Due to the way Jupiter's gravity tugs on Mars and perturbs its orbit, astronomers can only be certain that Mars has not come this close to Earth in the Last 5,000 years, but it may be as long as 60,000 years before it happens again.
The encounter will culminate on August 27th when Mars comes to within 34,649,589 miles of Earth and will be (next to the moon) the brightest object in the night sky. It will attain a magnitude of -2.9 and will appear 25.11 arc seconds wide. At a modest 75-power magnification Mars will look as large as the full moon to the naked eye. Mars will be easy to spot. At the beginning of August it will rise in the east at 10p.m. and reach its azimuth at about 3 a.m.
By the end of August when the two planets are closest, Mars will rise at nightfall and reach its highest point in the sky at 12:30 a.m. That's pretty convenient to see something that no human being has seen in recorded history. So, mark your calendar at the beginning of August to see Mars grow progressively brighter and brighter throughout the month. Share this with your children and grandchildren. NO ONE ALIVE TODAY WILL EVER SEE THIS AGAIN

Problem #1: this is from 2003. Problem #2: People can’t read the sentence correctly. Look again:

At a modest 75-power magnification Mars will look as large as the full moon to the naked eye. [emphasis mine]

Do we get it now? If you were looking at the Moon without a telescope, then look through a telescope at 75x at Mars, they would appear the same size. It does not come close to implying that Mars will appear the same size as the Moon. I just don’t see how people keep ignoring the first part of that sentence.


1 Comment »

  1. I should have been more clear. My wife never actually read the email and was just telling me what her co-worker (note: a doctor) told her. She had the co-worker forward the email to her but hadn’t read it yet.

    Comment by noisedoctor — August 13, 2006 @ 7:51 am

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