## Perihelion and Aphelion

Perihelion and Aphelion The closest point to the Sun in a planet’s orbit is called perihelion. The furthest point is called aphelion. Notice how the planet moves fastest at perihelion and slowest at aphelion. Randy Russell). Perihelion and Aphelion The planets in our Solar System orbit the Sun. The orbits of some planets ...

## Eccentricity of an Orbit

Eccentricity of an Orbit Eccentricity of an Orbit You may think that most objects in space that orbit something else move in circles, but that isn’t the case. Although some objects follow circular orbits, most orbits are shaped more like “stretched out” circles or ovals. Mathematicians and astronomers call this ...

## Elliptical Orbits

Elliptical Orbits Elliptical Orbits You may think that most objects in space that orbit something else move in circles, but that isn’t the case. Although some objects follow circular orbits, most orbits are shaped more like “stretched out” circles or ovals. Mathematicians and astronomers call this oval shape an ellipse. ...

## Kepler’s 3rd Law: P2 = a3

Kepler’s 3rd Law: P2 = a3 Kepler’s 3rd Law: P2 = a3 Kepler’s 3rd law is a mathematical formula. It means that if you know the period of a planet’s orbit (P = how long it takes the planet to go around the Sun), then you can determine that planet’s distance from the ...

## Kepler’s 2nd Law : The Speeds of Planets

Kepler’s 2nd Law: The Speeds of Planets Kepler’s second law he again discovered by trial and error. Kepler realized that the line connecting the planet and the Sun sweeps out equal area in equal time. Look at the diagram to the left. What Kepler found is that it takes the same ...

## Kepler’s 1st Law: Orbits are Elliptical

Kepler’s 1st Law: Orbits are Elliptical Kepler’s 1st Law With Tycho Brahe’s observations, Kepler set out to determine if the paths of the planets could be described with a curve. By trial and error, he discovered that an ellipse with the Sun at one focus could accurately describe the orbit of ...

## Fundamental Forces

Fundamental Forces Fundamental Forces The interactions in the Universe are governed by four forces (strong, weak, electromagnetic and gravitational). Physicists are trying to find one theory that would describe all the forces in nature as a single law. So far they have succeeded in producing a single theory that describes ...

## Gravity Definition

Gravity Definition Gravity Definition is one of the universal forces of nature. It is an attractive force between all matter, and is very weak as compared to the other forces of nature. The gravitational force between two objects is dependent on their masses, which is why we can only see gravity in ...