# Mars approaches (question for astronomers) **URL:** \ **Category:** Factual Questions\ **Created:** [July 26, 2006, 6:24am UTC](https://boards.straightdope.com/t/mars-approaches-question-for-astronomers/366058 "2006-07-26T06:24:32Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![First\_Amongst\_Daves](https://avatars.discourse-cdn.com/v4/letter/f/4491bb/32.png) [@First\_Amongst\_Daves](https://boards.straightdope.com/u/First_Amongst_Daves)\ **Post date:** [July 26, 2006, 6:24am UTC](https://boards.straightdope.com/t/mars-approaches-question-for-astronomers/366058/1 "2006-07-26T06:24:32Z")
I received this chain e-mail today, together with some vivid photographs of Mars: > [@](#): > > 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 > > [images here] > > 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 12:30a.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 Is this correct? I find it hard to imagine that Mars would ever appear as large as the Moon in the night sky. If it is true, will I be able to see it from Perth Western Australia? (Antipodean constellations, for example, are quite different from the northern hemispheric view, for those who don’t know.) ---
**Author:** ![wolf\_meister](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolf_meister/32/15202_2.png) [@wolf\_meister](https://boards.straightdope.com/u/wolf_meister)\ **Post date:** [July 26, 2006, 6:39am UTC](https://boards.straightdope.com/t/mars-approaches-question-for-astronomers/366058/2 "2006-07-26T06:39:54Z")
The close approach of Mars occurred on August 2003. Here’s a cite: > **[Mars: What We Know About the Red Planet](https://www.space.com/47-mars-the-red-planet-fourth-planet-from-the-sun.html)** > > Mars is one of the most explored bodies in our solar system, here's why. This E-Mail story gets circulated each year and in late July, 2007, I’m sure someone will ask about it then too. Mars _never_ appeared to the naked eye to be the size of the full Moon by the way. ---
**Author:** ![Seven](https://avatars.discourse-cdn.com/v4/letter/s/3d9bf3/32.png) [@Seven](https://boards.straightdope.com/u/Seven)\ **Post date:** [July 26, 2006, 6:46am UTC](https://boards.straightdope.com/t/mars-approaches-question-for-astronomers/366058/3 "2006-07-26T06:46:21Z")
> [@wolf\_meister](#): > > Mars _never_ appeared to the naked eye to be the size of the full Moon by the way. …and it would REALLY suck if it ever did. ---
**Author:** ![First\_Amongst\_Daves](https://avatars.discourse-cdn.com/v4/letter/f/4491bb/32.png) [@First\_Amongst\_Daves](https://boards.straightdope.com/u/First_Amongst_Daves)\ **Post date:** [July 26, 2006, 6:52am UTC](https://boards.straightdope.com/t/mars-approaches-question-for-astronomers/366058/4 "2006-07-26T06:52:49Z")
Oh well there goes my perfectly good excuse to buy a telescope. Thanks all. ---
**Author:** ![exastris](https://avatars.discourse-cdn.com/v4/letter/e/b38774/32.png) [@exastris](https://boards.straightdope.com/u/exastris)\ **Post date:** [July 26, 2006, 7:31am UTC](https://boards.straightdope.com/t/mars-approaches-question-for-astronomers/366058/5 "2006-07-26T07:31:49Z")
I’ve gotten this one too. I believe there was a nugget of truth in it at one time: Mars, _as viewed through a decently sized telescope_, would have been as large as the full moon is to the naked eye. Or something to that effect. There are several big images in the middle of the email which break up the sentences in an awkward way. After many forwards, cutting and pasting, it gets further and further from the truth. (Not to say this was completely true to begin with- like most things, I think it started with a bit of truth, some good intentions, and a lot of stupid.) Mars is quite interesting though a telescope, regardless of its size. . . You can note the growing and shrinking of the polar ice caps, see global dust storms (in the dulling of the planet), and see albedo differences over the mid-lattitude areas. It takes some getting used to; the more you look at the planet through a telescope the more details you can discern. ---
**Author:** ![Santos\_L\_Halper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/santos_l_halper/32/1_2.png) [@Santos\_L\_Halper](https://boards.straightdope.com/u/Santos_L_Halper)\ **Post date:** [July 26, 2006, 12:36pm UTC](https://boards.straightdope.com/t/mars-approaches-question-for-astronomers/366058/6 "2006-07-26T12:36:28Z")
Here’s the [Snopes write up](http://www.snopes.com/science/mars.asp) about the email. The line break makes it less clear that the writer is saying: > [@](#): > > _At a modest 75-power magnification_ Mars will look as large as the full moon to the naked eye. emphasis mine Which is a pretty useless and confusing comparison anyway. The point of using a comparison is to put it into terms of what the reader can visualize. Would the average reader know how much magnification that is? Would they have a sense of how big Mars _normally_ looks at 75 power magnification? Of course not. The closest in 60,000 years is misleading too. He makes it sound like it’s going to be a hundred times closer than on a normal pass when it was really only a few percent closer than normal. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [July 26, 2006, 1:22pm UTC](https://boards.straightdope.com/t/mars-approaches-question-for-astronomers/366058/7 "2006-07-26T13:22:23Z")
If Mars and the Moon have an equal apparent diameter you can work it out with equal angles. Rad[sub]moon[/sub]/D[sub]moon[/sub] = Rad[sub]mars[/sub]/D[sub]mars[/sub] So Rad[sub]mars[/sub] = D[sub]mars[/sub]/D[sub]moon[/sub]\*Rad[sub]moon[/sub] which at closest approach works out to Mars having a radius about 6 times that of Jupiter. ---
**Author:** ![wolf\_meister](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolf_meister/32/15202_2.png) [@wolf\_meister](https://boards.straightdope.com/u/wolf_meister)\ **Post date:** [July 26, 2006, 2:45pm UTC](https://boards.straightdope.com/t/mars-approaches-question-for-astronomers/366058/8 "2006-07-26T14:45:40Z")
Mars’ diameter is about 4,200 miles. The Moon’s angular size is about 30 minutes of arc. For Mars to have this same angular size, its _distance_ would have to be about 480,000 miles. :eek: Wow that was a close call. I’m glad that won’t happen again for another 60,000 years. ---
**Author:** ![Cervaise](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cervaise/32/16693_2.png) [@Cervaise](https://boards.straightdope.com/u/Cervaise)\ **Post date:** [July 26, 2006, 3:37pm UTC](https://boards.straightdope.com/t/mars-approaches-question-for-astronomers/366058/9 "2006-07-26T15:37:19Z")
> [@First Amongst Daves](#): > > Oh well there goes my perfectly good excuse to buy a telescope. The sorority house up the hill isn’t excuse enough? 😉