Physics Space March 2019

Question 1

What is the universe made out of?

Answer 1

• Over 100 billion galaxies, one of which is the Milky Way.
• In the Milky Way there are over 100 billion stars, one of which is the Sun
• Orbiting the Sun is our solar system made up of planets, dwarf planets, comets and asteroids.

Question 2

When was the solar system formed?

Answer 2

4.6 billion years ago

Question 3

What are the 8 planets and the dwarf planet?

Answer 3

Inner Planets: Mercury, Venus, Earth, Mars
Outer Planets: Jupiter, Served, Uranus, Neptune
Dwarf Planet: Pluto

Question 4

What separates the inner and outer planets and the outer planets with other solar systems?

Answer 4

An asteroid belt separates the inner and outer planets and the Kuiper belt separates the outer planets with other solar systems.

Question 5

What are the characteristics of the inner planets?

Answer 5

• Rocky
• Dense
• Few or no moons
• No rings

Question 6

What are the characteristics of the outer planets?

Answer 6

• Giant sized
• Mainly ice and gas
• All have rings
• Many moons

Question 7

What is gravity?

Answer 7

• An attractive force
• Acts on all stars, planets and moons
• Size of force depends on the mass of the object and distance apart from other objects.
• Gravity form the Sun keeps the Earth and other planets on a circular/elliptical orbit.

Question 8

What % of the solar systems total mass does the sun have?

Answer 8

99%

Question 9

What is the life cycle of a star?

Answer 9

An average star or massive star is formed in a nebula.

Average Star –> Red Giant –> Planetary Nebula –> White Draft

Massive Star –> Red Super Giant –> Supernova –> Black Hole or Neutron Star

Question 10

What is a nebula?

Answer 10

A vast region of dust and gas where stars are born.

Question 11

How is a star born?

Answer 11

Dust and hydrogen gas in a nebula collapse under their own gravitational attraction. The particles are moving very fast and when they collide the temperature increases due to the kinetic energy being transferred into thermal energy. This makes a Protostar.

The temperature of the Protostar increases by several million degrees causing nuclear fusion to occur. The hydrogen nuclei collide together to create a heavier helium nuclei releasing lots of energy due to the difference in mass. This is the official birth of a star.

Question 12

How do stars die?

Answer 12

Stars die when they run out of hydrogen. This is because the hydrogen acts as a fuel for the nuclear fusion that takes place in the star so when it runs out no more nuclear fusion can take place. The lack of fusion taking place cause instability in the star so the forces are no longer balanced and it rapidly collapses.

Question 13

What happens when a star dies?

Answer 13

When a star dies, depending on its size it will go out with a bang or a whimper. Average sized stars become white dwarfs and go out as a whimper. Massive stars become supernovas and go out with a bang.

Question 14

Why are there circular/elliptical orbits?

Answer 14

The Earth and other planets are all moving at a constant speed. The gravitational pull of the sun creates a circular/elliptical orbit.

Question 15

Why must the speed of satellites orbiting Earth be just right?

Answer 15

If it is too slow, it will crash into the Earth. If it is too fast it will fly into outer space.

Question 16

How can you calculate the orbit speeds of planets?

Answer 16

You need to know:

• Distance from the planet and the sun. (Orbit radius)
• length of 1 year on the planet. (Time)

Speed of planet = Distance (2 x π x r)/Time

Question 17

What is the Doppler effect?

Answer 17

The Doppler effect is the sound you hear when a police car passes you with its siren on.

This is caused because when it moves towards you the the wavelength is shorter and the frequency is higher. When it moves away from you, the wave length is longer and the frequency lower.

Question 18

What is red-shift/blue-shift?

Answer 18

The Doppler effect also happens with light. When we see an object moving away from us it seems redder. We say the light has been red-shifted as it moves towards the red side of the spectrum. It has a longer wavelength and lower frequency. Blue-shift is the opposite when it moves towards the blue side of the spectrum.

Question 19

How did Hubble discover that the universe is expanding?

Answer 19

Hubble measured light arriving from other galaxies and found that it was red-shifted. As an object is red-shifted when moving away he could tell that the other galaxies where moving away in all directions showing that the universe is expanding.

Question 20

When was the universe created?

Answer 20

13.8 billion years ago.

Question 21

What was the big bang?

Answer 21

The big bang was a giant explosion in which all matter and energy was in a very small space and exploded from a single point expanding rapidly. The hot matter condensed into atoms with dust and gases forming stars.

Question 22

What is the geocentric model?

Answer 22

A model of our solar system with the Earth at the centre. It was put forward by a Greek astronomer Ptolemy around 100 AD.

Question 23

What is the heliocentric model?

Answer 23

A model of our solar system with the Sun at the centre. It was put forward by Copernicus in 1543.

Question 24

What helped improve our knowledge of our solar system?

Answer 24

The invention of the telescope by Galileo.