Science -- Your Future, Scotland's Future
SCI-FUN Roadshow Exhibits -- Uphill Gravity
SCI-FUN Roadshow Exhibits -- Uphill Gravity
In this exhibit you learn about how everything always rolls downhill.

Gravity makes things fall towards the Earth. Unless there is a stronger upward force, everything will go downwards.

But in the Uphill Gravity exhibit, it looked like the double cone was rolling up the slope, getting higher. No outside forces were at work, it was gravity doing it.

The thing is, uphill and downhill aren't always what you think they are. The double cone was definitely moving towards the higher end of the slopes, but it was actually going down.

The slopes are wider at the top, and the double cone got narrower towards the ends. This meant that as the double cone moved up the slope, a narrower part of the cone was touching the slope. This meant that the cone was actually lower down.

In 17th Century Italy, Galileo Galilei discovered that all objects fall at the same accelaration on Earth, now known to be 9.81 m/s2. In 1687, Sir Isaac Newton found that all objects are attracted to other objects; the bigger the mass of the object the bigger the attraction. So we don't feel any force of attraction to most objects we come across, but we do to the Earth which has a mass of 6 x 1024 kg, that is 6 with 24 zeros kg. Also, the closer we are to the object, the bigger the attraction. So we're attracted to the Earth but not the Sun, which has a bigger mass but is further away. (The Earth, however, is attracted to the Sun, which keeps the Earth in orbit.)

Astronauts experience weightlessness in space because they're not close enough to the Earth to feel its gravity. On the Moon, astronauts leap and bounce around because the Moon has weaker gravity than the Earth, because it has a smaller mass.

When we experience free-fall, it can also feel like a lack of gravity. Of course gravity is making us fall, but since all other objects are falling at the same speed, it seems like everything is floating. NASA make use of this idea to train astronauts to get used to zero gravity conditions. They take the astronauts up very high in an aeroplane, then go into freefall. For about 25 seconds, the astronauts experience zero-gravity before the plane goes up and starts again. These planes are nicknamed "Vomit Comets" because of the effect they often have on new astronauts.

1 Gravity makes things ________ towards Earth.
2 What did the slopes do, in the Uphill Gravity exhibit, that made the double cone move up them?
3 At what acceleration do objects move towards Earth, due to gravity?
4 Why don't we feel gravity from the Sun?
5 How do Vomit Comets recreate zero gravity?
6 How do you think water behaves in zero gravity?

1 Lose and gain weight in an instant. Do you ever notice that weird feeling when a lift starts and stops moving? Stand on a set of scales in a lift and watch yourself lose weight as you accelerate downwards and decelerate upwards, and gain weight as you accelerate upwards and decelerate downwards.
2 Recreate Galileo's gravity experiment. Stand at the top of a flight of stairs and have a friend stand at the bottom. Drop two objects of similar size and shape, but different mass. Do they reach the ground at the same time? Make sure you choose objects that won't break and watch out for other people.