Invisible Forces – Exploring Gravity

What is Gravity?

Gravity is an invisible force that pulls objects towards each other.

• Earth’s gravity keeps us on the ground and makes things fall to the ground. 
• Gravity depends on Mass and Distance.
  • Every object that has a mass also has gravity. The greater the mass, the greater the gravity.
  • The force of gravity also depends on the distance between objects. The larger the distance, the lower the force of gravity.
• The Sun and other planets in our solar system have gravity, which helps keep the planets in orbit around the sun.

Why do astronauts float in space?

Astronauts appear to be floating in space inside their spacecraft as they are in a state of free fall.

• Free Fall – The spacecraft is continuously falling towards Earth due to gravity but also moving forward at an incredible speed. The only force acting on the spacecraft is gravity. 
• Microgravity – In this state of free fall, the spacecraft and astronauts within it fall at the same speed toward Earth. The weak gravitational force in space is called microgravity, where everything feels weightless. 
• Floating – There is no solid ground in space to push back against the force of gravity, making it look like the astronauts are floating in space.

Fun Facts

Here are some interesting facts about gravity:

• In a free fall, two objects with different masses, like a ball and a feather, will hit the ground simultaneously when dropped from the same height.
• You will weigh less on the Moon than on Earth as the Moon’s mass is lower than Earth’s, which means its gravity is less than Earth’s.
• The gravitational pull of the Moon on Earth causes high and low tides in the oceans.
• In our universe, Black Holes have the strongest gravitational pull and suck in everything around it.

Review

Let’s quickly recap what we learned about gravity:

• What are the two factors that gravity depends on? Mass and Distance
• The greater the distance between two objects, the greater the gravitational pull. True or False? False
• Is the Moon’s gravity lesser than or greater than Earth’s, and why? Lesser as its mass is less than Earth’s
• A spacecraft continuously falls toward Earth, where gravity is the only force acting on it.  What is this state called? Free Fall
• What is the weak gravitational force experienced in spaced called, where everything feels weightless? Microgravity