Orbit

Kepler's Laws

Aimed at pupils aged 14-18, this activity will focus on investigating Kepler's three laws of planetary motion, with a particular emphasis on Kepler's Third Law: The Law of Periods, which explains the relationship between the distance from an orbiting body to a system's centre of mass and its period of orbit.

Pupils 16-18 / more able students: The relationship will also be put to the test by calculating the mass of the host star of the stellar system TRAPPIST-1 using the known orbital periods of its exoplanets.

Sophia Brahe

Sophia Brahe (1556 – 1643)

Centre of Mass

Earth and Moon taken by
the Galileo Spacecraft
Credit: NASA

Mass is the amount of "stuff", or matter, and object has and this amount remains the same wherever the object is, even though it's weight will change depending upon gravity.

Orbital Demonstration

Start Animation

Have a look at the picture to the left and imagine that you are holding the satellite up above the Earth.

What do you think will happen if you "let go"? Press the Start button to see.

That's right, gravity makes the satellite fall straight down to the surface.

Elliptical Orbits

Elliptical Orbit
Credit: Horvath and Rubber Duck

Gravity Animation

Solar Eclipse Animation

The animation below demonstrates a Total and Partial Solar eclipse. Notice how the sky gets darker as the Moon slowly passes across the face of the Sun, and that it gets much darker during a total eclipse than during a partial one.

Lunar Eclipse

Solar Eclipse

An eclipse of the Sun, or Solar Eclipse, occurs when the Moon comes directly between the Sun and the Earth so that the Earth lies in the shadow of the Moon.

Phases of the Moon

It takes the Moon around 27 days to orbit around the Earth, during this time we see the Moon go through a series of different shapes, known as the "phases" of the Moon. It takes around 29.5 days for the Moon to get back to exactly the same phase, this is a little longer than it takes it orbit the Earth, due to the fact that the Earth is also moving around the Sun at the same time.