Gravitation, Kepler and inverse square

The Ptolemaic model placed Earth at the centre of the universe. By what name is this model better known?

• Geocentric

• Heliocentric

• Copercentric

• Ptolemocentric

Copernicus moved our understanding of the solar system forward with his idea of the Sun being at the centre of our universe, but what was this model called?

• Geocentric

• Heliocentric

• Copercentric

• Ptolemocentric

Which of these describes when a planet is at its closest point to the Sun.

• Conjunction

• Aphelion

• Perihelion

• Astronomical Unit

When a planets appears to move backwards in the sky, it is said to be in which of these states?

• Direct Motion

• Stationary Point

• Retrograde Motion

• Reverse

Kepler's First Law states that all planets orbit the Sun .......?

• In equal areas at equal times

• On a circular path

• With an epicycle

• On an elliptical path

Kepler's Second Law states?

• Orbits change path

• Sweep out areas over equal amounts of time

• Planets continually accelerate

• T^2 = a^3

According to the inverse square law, if a planet's distance from the Sun is doubled, the gravitational force is....?

• Doubled

• Halved

• Quartered

• The same

According to Kepler's Third Law T^2 = R^3, with T being the orbital period and R being the mean distance from the Sun. But what units are they measured in?

• Arcsec and Hours

• Years and AU

• Seconds and metres

• Hours and Minutes

The point where a planet is furthest from the Sun is called: .....?

Two stars have the same luminosity, but one star is 6 times further away from us. How much more radiation will be received by an observer on Earth from the nearer star compared with the further star?

• 2x more

• 6x more

• 12x more

• 36x more