All About Gravity

We are learning all about space.

Today we were wondering “Why don’t we fall off the Earth when it is up-side down in space?”  We were also wondering “Why do astronauts on the moon bounce about so much every time they take a step?”…….Both these questions can be answered if we know about gravity.

On Earth if we drop anything, it falls to the ground.  Have you ever wondered why this is?

Well, there is a force called “gravity” which pulls everything it can.  That’s why things fall down if  they can.

Teacher had two identical pieces of paper.  She asked us which was heavier.  (We spotted this as a trick question, both weigh the same!)  When we let them fall, both pieces floated to the ground at the same time.  We know that it is air (air resistance) that makes the pieces of paper float in the air rather than fall straight down to ground.

Then she scrunched up one piece of paper and asked us again which piece of paper was heavier. (We didn’t realise that this is also a trick question-the two pieces of paper are still the same weight!)  This time when we dropped the paper, the scrunched up piece of paper landed first.

We were wondering if it is the weight or the shape of the object that matters when you are deciding which object falls first.  We decided to test this out:

A stone and a scrunched piece of paper are about the same shape but are very different weights. .  We tried dropping these at the same time.  Believe it or not they landed together.  We were amazed.

Next we tried two water bottles, one empty, one full.  We dropped these at the same time.  Again they landed at the same time.

Teacher told us that the astronauts were wondering if they dropped two completely different objects (different weights, different shapes, different sizes) at the same time, in a place with no air at all (on the Moon) would they land at the same time because there would be no air resistance.  What do you think happened? People think there is no gravity on the moon but we know there is reduced gravity which is what causes the astronauts on the moon to bounce quite high when they walk, but it is why they don’t float away altogether when they take a step. (We tried dropping a hammer and feather at the same time in the classroom.  Predictably the hammer landed first.)

Later on a famous scientist called Brian Cox tried the same experiment, but this time in a vacuum chamber on Earth.  Can you guess what he found?