All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Science
Bright light (Posted on 2015-04-09) Difficulty: 4 of 5
When the moon is full, it always looks brightest to us on Earth vs. any other phase since we see its full illuminated area. It’s the same for Mars and the other outer planets, as we see their “full” phase when they are also closest to the Earth, i.e. when they are aligned on the same side of the sun as the earth. Not so for Venus and Mercury. Because their orbital radii are smaller than Earth’s, they present less and less lit surface to an earth-based observer as they approach their closest distance to our planet. Therefore the position at which these two planets look the brightest from Earth is at some point where their orbital radius has some non-zero angle to that of Earth’s.

Develop the relationship on how bright Venus looks from the earth as a function of the angular difference in orbital positions, and solve for the angle where Venus looks the brightest from earth. Simplifying assumptions: the orbits are perfect circles in the same plane, and the orbital radius of Venus is 0.723 that of earth (a good avg. value).

Bonus for purely analytical answer.

  Submitted by Kenny M    
Rating: 4.0000 (1 votes)
Solution: (Hide)
Many online references give the answer as "about 40 degrees separation of orbits, when Venus presents about 27% of it's disk illuminated to the earth." One treatment of the math can be found here: http://articles.adsabs.harvard.edu//full/1999JALPO..42...18G/0000020.000.html

Comments: ( You must be logged in to post comments.)
  Subject Author Date
I fixed my model.Jer2015-04-16 10:23:09
re: Interesting question.Charlie2015-04-10 07:35:28
Some ThoughtsInteresting question.broll2015-04-09 23:47:03
comparison with an actual caseCharlie2015-04-09 20:05:18
re(2): GSP Model disagrees with the previous postsCharlie2015-04-09 17:14:21
re: GSP Model disagrees with the previous postsCharlie2015-04-09 16:15:01
GSP Model disagrees with the previous postsJer2015-04-09 14:19:29
what I getCharlie2015-04-09 13:03:18
my solutionDaniel2015-04-09 11:36:31
Please log in:
Login:
Password:
Remember me:
Sign up! | Forgot password


Search:
Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (3)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:
Copyright © 2002 - 2017 by Animus Pactum Consulting. All rights reserved. Privacy Information