Study the effect of the sunspots. EJS Galileo Sunspots Model illustrates the motion and changes in appearance of sunspots as they move across the disk of the Sun. Galileo's observation of the changing appearance of sunspots around 1611 provided strong evidence that the spots were actually blemishes on the surface of the Sun, an idea that conflicted with the Aristotelean notion of the perfections of the heavens. Through these observations Galileo was able to determine the obliquity of the Sun (the angle between the Sun's equator and the Ecliptic plane) as well as the rotational period of the Sun.

Display Options Menu
1. Show Equator Line: show a line representing the Sun's equator. The obliquity of this line can be adjusted by the user to match the motion of the sunspots.
2. Show Ecliptic Line: show a line representing the Ecliptic (the plane of Earth's orbit around the sun).
3. Show Directions: show arrows indicating East and West directions along the Ecliptic.
4. Show Randomly Generated Sunspots: show the four randomly generated sunspots.
5. Show User-Defined Sunspot: show the sunspot with user-defined latitude.

Visual Elements
1. Orange disk: the disk of the Sun.
2. Red line: the Ecliptic.
3. White arrows: East and West direction arrows along the Ecliptic.
4. Blue line: line representing the Sun's equator.
5. Black ovals: randomly generated sunspots.
6. Blue oval: sunspot with user-defined latitude.

Controls
1. Play/pause button: start or stop the simulation.
2. Step button: advance the simulation by one time step.
3. Reset button: reset the simulation and generate new sunspots.
4. Time: elapsed time in days.
5. Obliquity: the angle between the equator line and the Ecliptic, in degrees.
6. Latitude: the latitude (measured from the true equator of the Sun) of the user-defined sunspot, in degrees.

Requirements:
* Java

The license of this software is Free, you can free download and free use this calculator software.