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-   -   If the Moon were replaced by other planets... (http://www.trekbbs.com/showthread.php?t=209545)

Gary7 April 16 2013 01:57 AM

If the Moon were replaced by other planets...
 
Very cool video. Looks amazingly realistic.


SonOfMogh April 16 2013 08:43 PM

Re: If the Moon were replaced by other planets...
 
That's awesome

Metryq April 16 2013 09:08 PM

Re: If the Moon were replaced by other planets...
 
Morlocks would hate it.

https://lh3.googleusercontent.com/-Q...me-Machine.jpg

RoJoHen April 16 2013 09:35 PM

Re: If the Moon were replaced by other planets...
 
I honestly would have figured Jupiter and Saturn to look a lot bigger than that.

Finngle Bells April 17 2013 03:16 AM

Re: If the Moon were replaced by other planets...
 
^indeed. The proportions don't look right, especially Jupiter and Saturn.

EnsignRedshirt April 17 2013 04:11 AM

Re: If the Moon were replaced by other planets...
 
I was half expecting the Sun to suddenly pop up at the end and engulf everything.

gturner April 17 2013 06:21 AM

Re: If the Moon were replaced by other planets...
 
Quote:

RoJoHen wrote: (Post 7954267)
I honestly would have figured Jupiter and Saturn to look a lot bigger than that.

At the beginning of the clip the Earth's moon is a pretty small spot. They should have left it somewhere in the frame so your eyes would have a comparative reference point.

Reverend April 17 2013 10:23 AM

Re: If the Moon were replaced by other planets...
 
^Even so, I also expected those two to totally dominate the sky. Like so big you can't see the whole thing without turning your head. Either that's an inaccurate representation, or I have really underestimated how far away the moon is. Most likely the latter.

MacLeod April 17 2013 12:13 PM

Re: If the Moon were replaced by other planets...
 
Some of it might be down to perspective. Sometimes bodies such as the Sun and the Moon can appear larger or smaller than they actually are depedning on what else you are looking at.

Remember the Sun is something like 400x the diameter of the moon, they only look the same size because the sun is 400x further away from the Earth thn the moon.

Metryq April 17 2013 12:34 PM

Re: If the Moon were replaced by other planets...
 
1. Download Celestia, install and launch.

2. RETURN. "Moon" RETURN. G.

3. Note the distance in the info display at upper left. Now use HOME and END to set your distance at 400,000 km, roughly the apogee of the Moon from Earth. (The default FOV is noted at lower right. You can change that if you wish, but the default view will do for this exercise.)

4. Now go to Jupiter: 5. G.

5. Again, set your distance to (approximately) 400,000 km. A super of the two images looks like this:

https://lh5.googleusercontent.com/-w...00/angular.jpg

(I have orbits turned on, which is what those lines are.)

R. Star April 17 2013 09:32 PM

Re: If the Moon were replaced by other planets...
 
I'd hate to think what all that would do to our oceans. Though we'd be the moon rather than have a moon there. :p

RoJoHen April 17 2013 09:34 PM

Re: If the Moon were replaced by other planets...
 
Quote:

MacLeod wrote: (Post 7957405)
Some of it might be down to perspective. Sometimes bodies such as the Sun and the Moon can appear larger or smaller than they actually are depedning on what else you are looking at.

Well, yeah, but in this case the whole point is that Jupiter and Saturn are supposedly the exact same distance as the moon. According to the scale presented here, I'm way less impressed with how big those planets are.

Though part of me does wonder if the time of year and the sky might have played a role. The moon was presented as being quite tiny, yet there are definitely days throughout the year when the moon looks HUGE because of the way the light is bouncing around in the atmosphere.

Asbo Zaprudder April 17 2013 10:03 PM

Re: If the Moon were replaced by other planets...
 
Jupiter's radius Rj is about 10.9 times the Earth's radius Re, which is about 3.7 time's the Moon's radius Rm, so the angle subtended at the same distance would be about 40 times greater for Jupiter than the Moon and the solid angle (apparent area subtended) would be about 1600 times greater.

gturner April 17 2013 10:46 PM

Re: If the Moon were replaced by other planets...
 
^ figure up the difference in albedo and you could come up with how bright "Jupiter lit" nights on Earth would be. I'd imagine you could read a book by it.

gturner April 17 2013 11:02 PM

Re: If the Moon were replaced by other planets...
 
Jupiter is 88,736 miles in diameter and the moon is 2,160 miles in diameter, so the area difference is 1,688. The albedo of the moon is 0.12 and Jupiter is 0.52, so the nighttime full moon brightness would go up by 7,313. Bright moonlight is about 0.25 Lux (0.2 to 0.3), so with Jupiter we could have 1,800 Lux. Office lighting is usually 300 to 500 Lux and a TV studio is about 1,000 Lux, as is an overcast day. So it would be very bright indeed.


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