Astonomy

Question 1

Explain why the gravitational field strength is different in each location (eg. Earth, Mars, Pluto etc)

Answer 1

The gravitational field strength is caused by its mass, so the more massive an object is, the more gravity it has

Question 2

All the planets, and the asteroids and other smaller objects, orbit the Sun. State the only force acting on these objects to keep them in their orbits

Answer 2

The only force acting on them is their WEIGHT due to the SUN’S GRAVITATIONAL FIELD

Question 3

How do orbits work?

Answer 3

• everything is moving in (roughly) a circle around the Sun with only their weight due to the Sun’s gravitational field acting on it
• this is because things want to move in a straight line unless acted upon by a resultant force and the weight of each due to the Sun is the resultant force
• this force acts at a right angle to the motion, (ie. towards the centre, pulling them around - it is a centripetal force)

Question 4

Do all planets move through space at the same speed as each other? Explain your answer

Answer 4

• no
• the ones further out move slower
• this is because each one out is much further from the Sun than the one before, and so the force from the Sun is weaker
• (if the force from the Sun was constant then ones further out would have to move faster, like satellites around the Earth do)

Question 5

A satellite is put into orbit around the Earth. Its speed is then increased. What happens to its orbit?

Answer 5

It moves out to a more distant radius of orbit

Question 6

A satellite is put into orbit around the Earth. Its mass is then increased. What happens to its orbit?

Answer 6

Nothing. Mass does NOT affect the orbit of an object

Question 7

List, in order starting with the centre and moving outwards, the contents of the Solar System

Answer 7

Sun, Mercury, Venus, Earth (with Moon), Mars (and moons), asteroid belt, Jupiter (with moons), Saturn (with moons), Uranus (with moons), Neptune (with moons), the Kuiper belt including Pluto and moon

Question 8

Why did the geocentric model have the Earth in the centre and everything orbiting around it?

Answer 8

It explained the fact that, looking at the sky, everything appears to move across the sky around us

Question 9

How was the heliocentric model created?

Answer 9

• Copernicus developed his model because the geocentric model didn’t fit observations very well
• Copernicus found that by assuming the Sun was in the middle and the Earth moving around it, while SPINNING (which caused the motion of things on the sky to look like they go around us), then his simple model of the planets circling the Sun worked very well

Question 10

Who backed up Copernicus’s work and how?

Answer 10

• Galileo used the recently invented telescope to observe various things that backed up Copernicus’s ideas, such as:
  
  • the moons of Jupiter (that orbit Jupiter, not Earth)
  • the phases of Venus (that can only be explained if Venus is moving around the Sun, not Earth

Question 11

What happened in the 1950s?

Answer 11

The USA and Russia started sending things into space, and then in the 60s the first space telescope was launched

Question 12

What are the advantages and disadvantages of space telescopes?

Answer 12

Disadvantages:
- very expensive

Advantages:

• above the Earth’s atmosphere so they can get a much clearer view of the Universe (not interfered by Earth’s atmosphere or light pollution)
• they can pick up parts of the EM spectrum (eg. Gamma rays, x-rays) that never make it to the surface of the Earth from space