## Motion

What we'll learn in this sectionTopic 8 – Planetary motion and gravity

8.3 - Understand the role of gravity in creating stable elliptical orbits8.4 - Understand Kepler's laws of planetary motion

8.5 - Understand the terms ‘aphelion’ and ‘perihelion’ (solar orbits), ‘apogee’ and ‘perigee’ (Earth orbits) for an elliptical orbit

8.6 - Be able to use Kepler’s third law in the form: a constant

__T__= a constant

^{2}r

^{3}

where

*T*is the orbital period of an orbiting body and

*r*is the mean radius of its orbit

8.7 - Understand that the constant in Kepler’s third law depends inversely on the mass of the central body

8.8 - Know that Newton was able to explain Kepler’s laws using his law of universal gravitation

8.9 - Understand that the gravitational force between two bodies is proportional to the product of their masses and inversely proportional to the square of their separation (algebraic expression of Newton’s law of universal gravitation not required)

Topic 5 – Solar System observation

5.2 - Understand the observed motion of the Sun follows an annual path called the ecliptic5.3 - Understand the changing position of the planets in the night sky

5.4 - Understand the observed motion of the planets takes place within a narrow Zodiacal Band

5.5 - Understand the observed retrograde motion of planets

5.7 - Understand the appearance and cause of meteors and meteor showers, including determination of the radiant

5.8 - Understand the terms:

a) conjunction (superior and inferior)

b) opposition

c) elongation

d) transit

e) occultation

Topic 7 – Early models of the Solar System

7.1 - Understand the use of detailed observations of solar and lunar cycles by ancient civilisations around the world for:- agricultural systems

- religious systems

- time and calendar systems

- alignments of ancient monuments

7.2 - Understand that the current celestial alignment of ancient monuments differs from their original celestial alignment due to the precession of the Earth’s axis

7.3 - Understand early geocentric models of the Solar System

7.4 - Understand the advantage of the addition of epicycles, as described by Ptolemy

Topic 8 – Planetary motion and gravity

8.1 - Understand the contribution of the observational work of Brahe in the transition from a geocentric to a heliocentric model of the Solar System8.2 - Understand the contribution of the mathematical modelling of Copernicus and Kepler in the transition from a geocentric to a heliocentric model of the Solar System

Topic 11 – Exploring the Solar System

11.9 - Be able to use the astronomical unit (1 AU = 1.5 × 108 km), light year (l.y.) and parsec (pc)11.11 - Know that most bodies in the Solar System orbit the Sun in, or close to, a plane called the ecliptic

11.24 - Understand the importance of Galileo's early telescopic observations in establishing a heliocentric (Sun-centred) model of the Solar System

Topic 3 – The Earth-Moon-Sun system

3.6 - Understand how the gradual precession of the Earth’s axis affects the appearance of the Sun, Moon and stars, when observed from Earth, and its use in archaeoastronomy3.7 - Be able to use data relating to the rate of precession of the Earth’s axis

In this section you will earn about orbits of celestial objects, terms about orbits and fundamental laws of physics and astronomy.