Saturday, January 18, 2014

Ejs Open Source Moon Phases Java Applet « on: August 17, 2010, 11:49:40 PM »

Ejs Open Source Moon Phases Java Applet 
« on: August 17, 2010, 11:49:40 PM »

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun (modeled) and the rotation of the Earth (not in the model yet).

Some shorelines experience two almost equal high tides and two low tides each day, called a semi-diurnal tide. Some locations experience only one high and one low tide each day, called a diurnal tide. Some locations experience two uneven tides a day, or sometimes one high and one low each day; this is called a mixed tide. The times and amplitude of the tides at a locale are influenced by the alignment of the Sun and Moon (modeled) . by the pattern of tides in the deep ocean, by the amphidromic systems of the oceans and by the shape of the coastline and near-shore bathymetry.
This model assumes the theoretical amplitude of oceanic tides. 
The Sun causes tides, of which the theoretical amplitude is about 25 centimetres (46% of that of the moon) with a cycle time of 12 hours. 

$\ x = 2 R_{earth} + 0.25 (2) $

$\ y = 2 R_{earth} - 0.25 (2)$

Moon causes tides is about 54 centimetres at the highest point, which corresponds to the amplitude that would be reached if the ocean possessed a uniform depth, there were no landmasses, and the Earth were rotating in step with the moon's orbit. 

$\ x = 2 R_{earth} + |0.54 (2) cos \theta | $

$\ y = 2 R_{earth} + |0.54 (2) sin \theta |  $

At spring tide the two effects add to each other to a theoretical level of 79 centimetres (31 in), while at neap tide the theoretical level is reduced to 29 centimetres (11 in). Since the orbits of the Earth about the sun, and the moon about the Earth, are elliptical, tidal amplitudes change somewhat as a result of the varying Earth–sun and Earth–moon distances. 

The combined tidal visualization effect will be:

$\ x = 2 R_{earth} + 0.25 (2) + |0.54 (2) cos \theta | $

$\ y = 2 R_{earth} +  0.25 (2 )+ |0.54 (2) sin \theta |  $

Real amplitudes differ considerably, not only because of depth variations and continental obstacles, but also because wave propagation across the ocean has a natural period of the same order of magnitude as the rotation period: if there were no land masses, it would take about 30 hours for a long wavelength surface wave to propagate along the equator halfway around the Earth (by comparison, the Earth's lithosphere has a natural period of about 57 minutes). Earth tides, which raise and lower the bottom of the ocean, and the tide's own gravitational self attraction are both significant and further complicate the ocean's response to tidal forces.

To model the scientific graphs versus time, the model used

$\ y_{1sun}= 0.25*Math.cos( \frac{2 \pi t}{12} ) // sun where t is in hours $

$\ y_{2moon} = 0.54*Math.cos(\frac {61}{59} \frac{2 \pi t}{12} )// moon where t is in hours $

resultant is

$\ y_{1sun} +y_{2moon} = 0.25*Math.cos( \frac{2 \pi t}{12} )  +0.54*Math.cos(\frac {61}{59} \frac{2 \pi t}{12} ) $ version 20 Jan 2014
added sea-level modeling by lookang
author: todd timberlake and lookang
Ejs Open Source Moon Phases Java Applet

added on January 18 2014
 added high tide and low tide as a response to the Moon's gravitational field. version 03 Jan 2011
author: todd timberlake and lookang
Ejs Open Source Moon Phases Java Applet version 03 Jan 2011
author: todd timberlake and lookang
Ejs Open Source Moon Phases Java Applet

earlier version 17 August 2010
 i did not make this, this applet is made by Dr Todd Timberlake

i only remix it so that i can learn phases of moon from the open source computational model:)
read some article on moon phases, decided to figure out the physics first hand to understand what is so difficult because i didn't know this until now.
learn alot from Youtube, the Ejs applet

Full screen applet
kindly hosted in NTNUJAVA Virtual Physics Laboratory by Professor Fu-Kwun Hwang
alternatively, go direct to
Collaborative Community of EJS (Moderator: lookang) and register , login and download all of them for free :) This work is licensed under a Creative Commons Attribution 3.0 Singapore License
Author: Todd Timberlake and lookang
Taken from

Phases of Moon Model: Lesson Plan
A pdf file with a teacher lesson plan for use with the Phases of Moon Model.

Phases of Moon Model: Homework Exploration
A pdf file with a college-level homework exploration for use with the Phases… more...
download 206kb .pdf