Brainspace – July 2019

brainspace SUMMER 2019 37

PIANOS OR DOUGHNUTS?

by mario carr and marnie ferguson
You would think that if you dropped a piano out of
a window, it would fall faster to the ground than if
you dropped a doughnut from the same window.
Nope. They fall at the same speed. It’s a head-
scratcher and some very famous scientists decided
to see if they could figure out what was going on.

TRY IT: Do heavier objects fall faster?
If you drop a ball and a sheet of paper at the same
time, which one hits the ground first? The ball
seems to fall faster than the sheet of paper that
floats to the ground. However, the paper floats
because of another force working against gravity

• air resistance. If you could magically remove air
  resistance, then you could see how gravity affects
  mass. Since we can’t easily remove the air, we can
  do the next best thing by crunching the sheet of
  paper into a tight ball to remove air resistance.
  Now, drop the ball and the crunched sheet of
  paper at the same time from the same height. Both
  objects will hit the ground at the same time.

GALILEO GALILEI

About 2,500 years ago, the ancient Greek philosopher,

Aristotle believed that heavier objects fall faster than lighter

ones. Then, about 2000 years later in 1589, the Italian

scientist Galileo Galilei also became interested in how objects

fall. He started to throw things off the Leaning Tower of Pisa and

discovered that objects fall at exactly the same rate even though they

had different weights. This proved that gravity is a constant force that

acts equally on all objects.

Almost 400 years later, in 1971, Commander David Scott decided to

test Galileo’s theory of gravity with an experiment on the Moon when

he arrived there as commander of the Apollo 15 mission. He dropped

a hammer and a falcon feather at the same time, proving Galileo’s

discovery.

SIR ISAAC NEWTON

About 100 years after Galileo got the ball rolling on gravity,

the famous thinker and scientist Sir Isaac Newton was hit on

the head with an apple one day in 1686. This got him thinking

about gravity. Rubbing his head, he realized that gravity is

a force, and the force of gravity acts between objects. The

gravitational pull of the Earth on the apple was the force that made

it fall. This was a very important discovery and he went on to find a

mathematical equation to measure the force. That is why the force of

gravity is measured in newtons.

It was Sir Isaac newton who explained that the ocean tides happen

because of the pull of gravity by the sun and the moon on the oceans.

He also realized that gravity was the reason why the planets orbit

around the Sun.

ALBERT EINSTEIN

He questioned everything. Including the wonder of gravity. He

worked on the Newton laws and redefined them in his very

famous Theory of General Relativity. Einstein was thinking

about much larger objects and how the force of gravity

affected space and the universe.

He predicted that gravity had an effect on outer space. Just think

of space as a big stretchy rubber sheet. Place a bowling ball on the

rubber sheet and it bends. Place an apple on the sheet and it still

bends, but much less. The larger the object in space, the greater the

bend on space. His theory was proven correct on April 10th, 2019.

The recent photograph of a black hole in outer space, is the first one

of its kind.

could jump six times higher than

on Earth. That’s because the Moon

has less mass and only one sixth the

gravity of Earth.

Gravity and

Black Holes

After a star has burned through its

fuel, it could explode as a super

nova. Sometimes a neutron star

is created when this happens. Its

gravitational forces are so intense

that it acts like an intergalactic

vacuum cleaner called a black hole,

sucking up everything. Nothing

can escape from it, not even light.

Our Milky Way Galaxy has a black

hole right in its centre. Don’t worry;

we’re really far from it.

Gravity and the

Big Crunch

The Big Bang Theory isn’t just a TV

show – it’s also how scientists think

the universe was created about 13.7

billion years ago. The theory says the

universe was created and continues

to expand even today from a single

point. Scientists aren’t sure if the

universe will continue to expand

forever, or if gravity will take over,

shrinking it back to a point. Some

people call this the Big Crunch.

First ever photograph of a black hole

taken on April 10th, 2019

Use Zappar. Scan for a video demonstration.