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PhET- Earth Science

Page history last edited by Shawn Murphy 8 years ago



Content standard: Earth Science Standard 3.2.a,b,c




PhET is a great resource for teaching scientific concepts, from elementary to secondary. The simulation below is a valuable resource for demonstrating Newton's laws of motion and universal gravation. In the simulation, the position of the bodies can be adjusted using the (X,Y) coordinate system where the center of the page is (0,0) or by dragging the body to the desired position. The velocity of the bodies can be changed by adjusting the vectors of the bodies using an (X,Y) coordinate system with the center of the body at the (0,0) position. The length of the arrows indicates the velocity of the body which can be adjusted for all of the bodies. Bodies will move in the direction that is inputed also using the coordinate system. For example, if you input the coordinates X=-12 and Y=+12, the body will move in a northwest direction. If you input the coordinates X=+12 and Y=+12 the body will move in a northeast direction. You can also adjust the masses of the bodies using the table at the lower left. There is also a help button to give you advice.


Test out the simulation below using these criteria:


Demo 1:

1. Start with just two bodies and click the start button.

2. Notice how the Earth moves around the sun.

3. We tend to think of the sun and being stationary but the Earth's gravity pulls on the sun as much as the sun's gravity pulls on the Earth. This is why there is a slight movement on the sun.


Demo 2:

1. Press the reset button.

2. Begin with two bodies.

3. Adjust the 2 body to a mass of 50 instead of 10. Press the start button.

4. Notice how much more pronounced the movement of the sun is when the mass of the Earth is increased.


Demo 3:

1. Press the reset button.

2. Begin with three buttons.

3. Press the start button.

4. One of the most interesting insights when viewing the simulation is that the moon travels in a corkscrew path around the sun. Most people understand that the moon makes a circular orbit around the Earth. What they may fail to consider is that while the moon is moving around the Earth, the Earth is moving around the sun and its overall path in more complex.


Demo 4:

1. Set the simulation for 2 bodies.

2. Set the position of the 2nd body on the X axis to 100 and the velocity of the 2nd body on the y axis to 175.

3. Press the start button.

4. Notice how the 2nd body slows down as it gets to its furthest point away from the sun, apogee, and how it increases in speed as it gets to its clostest point to the sun, perigee.


Demo 5:

1. Choose the slingshot option from the dropdown menu above the start menu.

2. Notice how the second body is ejected from the solar system.

3. This is the process by which our early solar system is thought to clear debris from between the inner planets. As the gravity of earth and other planets acts on smaller bodies, such as asteriods and comets, these bodies were ejected from the solar system. The formation of the asteroid belt between mars and Jupiter is thought to have been formed from the gravity of our planets pulling these rocks into defined orbits. A similar pattern develops in the the rings and moons of planets like Saturn. This process is also used by NASA to give extra momentum to spacecraft that are traveling to the outer solar system.

4. Around time 170, the satelite will return, much like comets return after a prolonged period away.


Demo 6:

1. Choose the 'sun, planet, comet' option from the dropdown menu above the start menu.

2. Change the Y axis on the 3rd body from 130 to 150.

3. Set the speed meter to the far left to make the calculation the most accurate.

4. At time 49.7, the comet comes in close proximity to the planet and its path is altered. This is known as a gravational keyhole that results in a collision with the planet at time 58.1.




Movement of celestial bodies

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