1. How spaced out are planets? How big are they compared with the Earth?
The Solar System
How spaced out are planets?
How big are they compared with the Earth?

2. Q Which is the 3rd planet from the Sun?
Which is the 5th planet from the Sun?
Which is the planet which you would expect to be coldest?
Which is the planet which you would expect to be hottest?

3. A Earth – “Third rock from the Sun.” Jupiter
Neptune – it is furthest away. (I will accept Pluto but it is not a true planet and is sometimes closer to the Sun than Neptune!)
Mercury – because it is so close. In fact Venus is the hottest because of its thick atmosphere.

4. The Planets are not at all even spaced.
There is a large gap between Mars and Jupiter.
This gap is filled by the asteroid belt.
Sometimes these can cause us problems here on Earth!

7. Model Solar System Sun Mercury 1.2 cm Venus 2.4 cm Earth 3.3 cm Mars
Jupiter
17.3 cm
Saturn
31.7 cm
Uranus
63.9 cm
Neptune
100.0 cm

8. Sun
Mercury
1.2 cm
58 million km
Venus
2.4
108
Earth
3.3
150
Mars
5.0
228
Jupiter
17.3
778
Saturn
31.7
1430
Uranus
63.9
2870
Neptune
100.0
4500

9. Planets are all much smaller than the Sun.

10. Jupiter is the biggest Planet
Jupiter, Saturn, Uranus, Neptune in front of the Sun to scale.

11. Earth and Saturn to scale.

12. Mercury 0.40 400 Venus 0.70 450 Earth 1.00 20 Mars 1.50 -20 Jupiter
Planet
Distance (AU)
Distance (millions of km)
Temperature (degrees Celsius)
Mercury
0.40
400
Venus
0.70
450
Earth
1.00 20
Mars
1.50
-20
Jupiter
5.0
-150
Saturn
9.5
-170
Uranus
19.0
-200
Neptune
30.0
-210
Plot a graph of distance (millions of km) against temperature (degrees C)

14. What is an “AU” in astronomy?
Why is Venus hotter than Mercury, even though it is further from the Sun?
What would happen to liquid water on the surface of Venus?
What would happen to liquid water on the surface of Mars?
Using your answers to 3 and 4 above, why is the Earth the only planet in the Solar System suitable for complex life?

15. Chart of temperature (up the side) against distance (along the bottom
Go from – 210 to +400 on the temperature axis.
Go from zero to 30 on the distance axis.