APOD: Retrograde Mars
apod.nasa.gov — Why would Mars appear to move backwards? Most of the time, the apparent motion of Mars in Earth's sky is in one direction, slow but steady in front of the far distant stars. About every two years, however, the Earth passes Mars as they orbit around the Sun.
optimusprime01- 554 diggs
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- maybeishould, on 05/11/2008, -2/+7Like a rollercoaster in space.
- k7jeb, on 05/11/2008, -0/+2Yeah, you'd think the Martians would be getting a rough ride out of it, wouldn't you...
- awuwish, on 05/11/2008, -5/+6Ironic; we just finished discussing this in my physics class. O.o
- sc0rpi0n, on 05/11/2008, -2/+12Funny and ironic are different. I don't see how the word "Ironic" fits in either NASA's context or yours.
- devaka, on 05/11/2008, -2/+2Do you work in NASA?
- fr3ddie, on 05/11/2008, -3/+1way to be a dick.
- Anomaly100, on 05/11/2008, -4/+1Semantics. I find it ironic too.
- Tyrghast, on 05/11/2008, -0/+1BUT IT THERE IS NO IRONY IN THIS SITUATION!!!!
- infinitejones, on 05/11/2008, -0/+0It's like 10,000 spoons when all you need is a knife.
- FarOutGrace, on 05/11/2008, -0/+0The irony that awuwish may have meant could very well be that it was "odd" that this very thing was just discussed in her/his physics class. It was ironic as in unusual that it came up twice in so short a time. The irony is that it's kind of funny and out of the ordinary that it was just discused and he/she ran into the topic again so soon. I think that was how it was meant that's all. Just an expression. God bless.
- Tyrghast, on 05/11/2008, -0/+1BUT IT THERE IS NO IRONY IN THIS SITUATION!!!!
- withoutamartyr, on 05/11/2008, -0/+3The quality or state of an event being both coincidental or contradictory in a humorous or poignant and extremely improbable way.
This would be 'coincidental'. - ElAssoWipo, on 05/11/2008, -0/+1Ironic would've been to cover the exact opposite in class.
- awuwish, on 05/11/2008, -2/+2Sorry, I'm not an English major like everyone here seems to be. It's "coincidental" which could explain irony.
- sc0rpi0n, on 05/11/2008, -2/+12Funny and ironic are different. I don't see how the word "Ironic" fits in either NASA's context or yours.
- imabug, on 05/11/2008, -1/+0gotta love those planetary loop-de-loops
- threemagic, on 05/11/2008, -2/+1Looks like some aliens got loaded up on Nybord and did some doughnuts in space...
- coltraning, on 05/11/2008, -2/+3dugg the neat rollover chart
- goscript, on 05/11/2008, -0/+3It would be fun to get an X and Y axis and get them onto an equation
- kilworth, on 05/11/2008, -1/+6I think after digg started featuring every APOD article I think APOD is now slowly adjusting to the digg audience.
Or how do you explain a video of cute kittens in the description of a astronomy pic?
http://www.youtube.com/watch?v=1WtNMufWmw0 or click on "motion" in the last sentence.- goscript, on 05/11/2008, -0/+3They were probably watching Mars going backwards? :))
- UrinalPooper, on 05/12/2008, -0/+1They've always kept it light and fun.
- elbergel, on 05/11/2008, -1/+2Retrograde Motion? Sounds like the work of Xenu to me...
- k7jeb, on 05/11/2008, -0/+1Yeah, isn't this the kind of thing that the astrologers are always warning us about?
- kilworth, on 05/11/2008, -1/+2http://www.youtube.com/watch?v=1WtNMufWmw0
- Totz83, on 05/11/2008, -6/+1As far as APODs go, this sucks
- gu0d, on 05/11/2008, -1/+3Wait, so why does it happen.
- infinitejones, on 05/11/2008, -0/+5Earth travels faster than Mars when they're orbiting the Sun (because it's closer to the Sun). Therefore every so often Earth "overtakes" Mars and from our viewpoint on Earth, this makes it look like Mars is travelling backwards. Imagine you're driving at 40mph and you overtake a vehicle ahead of you travelling at 35mph - you're both travelling in the same direction, but to you or one of your passengers, as you go past the other car, it appears to be travelling backwards. To keep your eyes fixed on the other car, you'd need to turn your head in the opposite direction to the direction you're travelling. Same thing with people on Earth looking at Mars.
- gu0d, on 05/11/2008, -0/+3thank you for your explanation
- Scynet, on 05/11/2008, -0/+1Here's an animation:
http://www.flex.com/~jai/astrology/retrograde
- infinitejones, on 05/11/2008, -0/+5Earth travels faster than Mars when they're orbiting the Sun (because it's closer to the Sun). Therefore every so often Earth "overtakes" Mars and from our viewpoint on Earth, this makes it look like Mars is travelling backwards. Imagine you're driving at 40mph and you overtake a vehicle ahead of you travelling at 35mph - you're both travelling in the same direction, but to you or one of your passengers, as you go past the other car, it appears to be travelling backwards. To keep your eyes fixed on the other car, you'd need to turn your head in the opposite direction to the direction you're travelling. Same thing with people on Earth looking at Mars.
- bouche, on 05/11/2008, -6/+6I've got news for you. There is an RSS feed of APOD images that you can subscribe to and spare us from seeing these images posted on Digg every goddamn day. yeesh! who's with me?
- colonels1020, on 05/11/2008, -1/+3I am. :P
- matt510, on 05/11/2008, -1/+3I know, it is SO very difficult to sort through the ONE article per day... I am MUCH better of sorting through the hundreds of lame political posts on Digg, that is much more entertaining and educational...
/sarcasm
- colonels1020, on 05/11/2008, -0/+2aPod
- matt510, on 05/11/2008, -0/+3Wait... so that means the Earth ISN'T at the center of the universe? My world is crashing down around me!
- FarOutGrace, on 05/11/2008, -0/+0Does this also mean that I am not the center of the universe either? Oh mannn....
sarcasm
- FarOutGrace, on 05/11/2008, -0/+0Does this also mean that I am not the center of the universe either? Oh mannn....
- OropheR, on 05/11/2008, -0/+2I am not quite sure I could explain the whole thing, but the only reason why Mars looks like it's going backward, is because Earth reaches a segment on its orbit that makes it move faster than Mars.
- UrinalPooper, on 05/12/2008, -0/+1Kepler's 3rd law: The squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axes (the "half-length" of the ellipse) of their orbits. This means not only that larger orbits have longer periods, but also that the speed of a planet in a larger orbit is lower than in a smaller orbit. [so saith wikipedia]
This was part of the great break in physics where data started determining the rules as opposed to the aristotelean models which held back great minds like Brahe. Tycho Brahe taught Kepler. Voluminous amounts of observation were compiled and on top of those theories laws were written,
- UrinalPooper, on 05/12/2008, -0/+1Kepler's 3rd law: The squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axes (the "half-length" of the ellipse) of their orbits. This means not only that larger orbits have longer periods, but also that the speed of a planet in a larger orbit is lower than in a smaller orbit. [so saith wikipedia]
- FranksValli, on 05/12/2008, -0/+3Awesome :). This is the kind of movement of the "wanderer" stars was observed by ancient astronomers but was baffling because it appeared that the heavens didn't move in perfect concentric circles after all. The Ptolemaic model explained this by way of "epicycles", which was a clever model that was actually accurate enough at the time, and still preserved the "perfect circles" theory. It took over a millenia, and the highly detailed observations of Tycho Brahe (this data was used by Kepler), before they were fit into the current model. Needless to say, it's more than a cool photo - there's a lot of history behind it :)
- h3lx, on 05/12/2008, -0/+3Aside from all of that, the outlandish western theories evolving from these observations are a fun read having knowledge after the fact.
More amazing is the older Hindu cultures had much of this mathematically resolved and and somehow, in the large span of time some ancient knowledge was lost, distorted, or taken from us. It's a fun read.
(it's a bit dated as far as design and layout, but the info is solid).
http://www.geocities.com/dipalsarvesh/datingMahabh ...- FranksValli, on 05/12/2008, -0/+2Cool, I'll check it out!
- h3lx, on 05/12/2008, -0/+3Aside from all of that, the outlandish western theories evolving from these observations are a fun read having knowledge after the fact.
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