109th Carnival of Space courtesy of Twisted Physics - where you can find out about spacey B-movies, staring into a really big black hole, Apollo's plan B, solsitice celebrations, more Tunguska, Canadian fusion, a shrinking planet, and more!
Monday, June 29, 2009
Sunday, June 28, 2009
I received my first Mars Hoax email of the season last week and thought I should clear the air.
In fact not only is Mars not going to be this big, in one sense it is shrinking ...
Origins of the Mars Hoax
On August 27, 2003 Mars and Earth lined up in what is known as an inferior conjunction or opposition. This is a normal astronomical event which happens every 26 months. That year the opposition was special because it was closer than normal. A lot was made of the fact that at 55.7 million km it was the closest Mars and Earth had come in almost 60,000 years.
A more realistic view is that Mars and Earth oppositions bring the two planets within the wide range of 55 to 101 million km. But they only get to close end of this range every 7 or 8 oppositions (e.g. 1956, 1971, 1988, 2003, 2018, 2035, 2050). When Mars is in close opposition it is nearly twice as close and will appear nearly twice as big. During these close oppositions Mars will appear much brighter than normal but you will still need a telescope to see it. These close oppositions are the very best times to see Mars through a telescope. The neighbouring oppositions (e.g. 2001, 2005, 2016, 2020) also allow excellent viewing opportunities.
What about 2009 through 2012?
Sorry, for 2009 the Earth is still catching up to Mars. The distance is closing but it's still over 280 million km away (see this neat real-time Earth Mars distance calculator).
Last December the two planets were on opposite sides of the Sun and almost 400 million km apart. The next oppositions in 2010, 2012, and 2014 are among the farthest and least interesting. So when the Mars Hoax email comes around in one of these poor years - enjoy a chuckle. Mars will continue to appear smaller and smaller until after 2012 when it begins to return to its regularly scheduled close oppositions. So in that sense, Mars is shrinking.
Click here for tables of Mars oppositions and closest approaches and a technical explanation at SEDS (Students for the Exploration and Discovery of Space).
Want to See for yourself?
Nothing helps like a visual. Try out the NASA/JPL orbit simulator, here. The reason I've used the asteroid Ceres to trick the simulator because you can't look up a planet or a moon in its database. Now you should:
- Click the Orbits drop down and select in order: No Orbits, Earth, and Mars
- Turn off the Distance label
- Zoom in a bit to get Ceres out of the picture
- Set the Way-back machine to Aug 27th 2003 (use Date or just run it backwards using "<<")
- Rotate the frame so Earth and Mars are front and center
- Set the Interval beside the date to 1 year
- Step forward and back
A quick search of Google for Mars+Hoax gets 810,000 hits. There are pages on the Mars Hoax at both Wikipedia and Snopes.com. Here are what just a few knowledgeable people are saying about this hoax:
- We Need The Mars Hoax... The Universe Just Ain't Exciting Enough | Space Disco - June 10, 2009
- Mars as Big as the Moon 09 #2 | Alice's Astroinfo - June 5, 2009
- Mars. Moon. No. | Bad Astronomy - June 4, 2009
- The Mars Hoax Rides Again | Astroblog - May 12, 2009 (with fixed/parody hoax Powerpoint)
- Really, Mars will NOT be the size of the Moon in the sky! | Astroprof - May 2, 2009
- Mars Hoax Lasts Five Years | Cosmic Log MSNBC - August 26, 2008
- Please (Again)– Mars Will NOT Look As Big As the Full Moon | Universe Today - August 23, 2008
- Today is the day Mars isn’t as big as the Moon! | Bad Astronomy - August 26th, 2007
- Will Mars Look as Big as the Moon on August 27? Nope | Universe Today - July 25th, 2007
- The Zombie Mars Hoax That will Not Die | Astroblog - July 24, 2007
- Return of the Great Mars Hoax | Cosmic Log MSNBC - August 21, 2006
- No, Mars Won't Look as Big as the Moon in August | Universe Today - July 27th, 2006
- Mars Hoax | Astroblog - August 2, 2005
- No, Mars Won't Look as Big as the Moon | Universe Today - July 8th, 2005
- Beware the Mars Hoax | Science @ NASA - July 7, 2005
- Mars Attacks | Bad Astronomy - August 13, 2003
The diameters of Mars and our Moon are about 6752 km to 3470 km or just about 2 to 1. For Mars to appear the same size as our Moon it would need to be much closer to us. About twice as far as our Moon in fact. At that distance Mars would be inside the Earth’s Hill Sphere and we would either have a second moon or be in really big trouble (see the picture above).
On a Lighter Note
Planetary oppositions of Mars were featured in two Warner Brothers cartoons:
- "Rocket-Bye Baby" used a close approach to Mars in 1954 to set up a cosmic mix up where a Martian and human baby were switched.
- In the 1958, "Hare-Way to the Stars", Bugs Bunny foils Marvin the Martian's plan to blow up Earth with the Illudium Q-36 Explosive Space Modulator because it obstructs his view of the planet Venus.