File:Galilean moon Laplace resonance animation.gif

From Wikiversity
Jump to navigation Jump to search

Galilean_moon_Laplace_resonance_animation.gif(365 × 245 pixels, file size: 351 KB, MIME type: image/gif, looped, 288 frames, 5.8 s)

Commons-logo.svg This is a file from the Wikimedia Commons. The description on its description page there is shown below.

Commons is a freely licensed media file repository. You can help.


English: Animation of the 1:2:4 Laplace resonance between Io, Europa, and Ganymede. The labels indicate the ratios of orbital periods: Europa's is twice Io's, and Ganymede's is four times Io's.
Warning: do not downsize the image below its original size of 365 × 245 when used in a Wikipedia article, as the animation won't move then (at least not for all users).
Date (UTC)
Source based on earlier version of this file, avail. below
Author User:Matma Rex
(Reusing this file)

Public Domain

Other versions


Public domain I, the copyright holder of this work, release this work into the public domain. This applies worldwide.
In some countries this may not be legally possible; if so:
I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.


This image has been generated by the following Ruby code and optimized in GIMP.

# author: Matma Rex
# code licensed under CC-BY-SA license

require 'rubygems'
require 'RMagick'
include Magick

step=5 # degrees by which Io will move in every frame

# Io, Europa, Ganymede
distances=[46, 72, 112]
speeds=[1, 0.5, 0.25]
shifts=[-90, 90, -90]

centery=122 365,245

# lines
gc.stroke 'lightgrey'
gc.stroke_width 1.5
distances.each{|d| gc.line centerx, centery-d, 360, centery-d}
gc.line centerx, centery, 360, centery

# orbits
gc.stroke 'grey'
gc.fill 'none'
gc.stroke_width 2
distances.each{|d| centerx, centery, centerx, centery+d}

# Jupiter
gc.stroke 'black'
gc.fill 'black'
gc.stroke_width 2  centerx, centery, centerx, centery+9

# labels
# gc.stroke_width 0
# gc.gravity EastGravity
# gc.font_family 'arial'
# gc.font_size 18
# gc.font_weight LighterWeight
# gc.text_align RightAlign
# gc.text_undercolor 'white'

# gc.text 360, centery-distances[0]+7, '"  Io 1:1"'.upcase
# gc.text 360, centery-distances[1]+7, '"  Europa 2:1"'.upcase
# gc.text 360, centery-distances[2]+7, '"  Ganymede 4:1"'.upcase

# gc.font_weight BoldWeight
# gc.text 360, centery+7, '"  Jupiter"'.upcase

gc.draw base

# ImageMagick sucks at text - load a predefined text img instead
base=base.composite'text.png')[0].transparent('cyan'), 0, 0, OverCompositeOp

(0..(4*360-1)).step(step) do |deg|

  0.upto(2) do |i|
    rad=(deg*speeds[i] + shifts[i]) * Math::PI / 180.0
    x=distances[i] * -Math.cos(rad)
    y=distances[i] * Math.sin(rad) centerx+x, centery+y,  centerx+x, centery+y+4.5

  gc.draw img
  list << img

list.write 'magick.gif'

File history

Click on a date/time to view the file as it appeared at that time.

current18:08, 16 February 2011Thumbnail for version as of 18:08, 16 February 2011365 × 245 (351 KB)Matma Rexa much nicer version, even if somewhat larger
18:33, 23 December 2010Thumbnail for version as of 18:33, 23 December 2010365 × 245 (21 KB)Bark~commonswikiChanged direction from clockwise to counter-clockwise to better represent the Jovian system with the view from above the north pole, the typical convention. The previous version accidentally implied retrograde motion in the system, which is not the case.
08:17, 3 November 2006Thumbnail for version as of 08:17, 3 November 2006365 × 245 (32 KB)Splarka{{Information |Description=Animation of the 4:2:1 Laplace resonance between Ganymede, Europa, and Io |Source=created for Wikimedia |Date=~~~~~ |Author=User:Splarka |Permission=Public Domain |other_versions=This is the first }}

Global file usage

The following other wikis use this file:

View more global usage of this file.