Gravity
Read, then answer:
Gravity is the force by which a planet or other body draws objects toward its center. The force of gravity keeps all of the planets in orbit around the sun.
What keeps all of the planets in orbit around the sun? The force of gravity
What else does gravity do?
Why do you land on the ground when you jump up instead of floating off into space? Why do things fall down when you throw them or drop them? The an\wer is gravity: an invisible force that pulls objects toward each other. Earth's gravity is what keeps you on the ground and what makes things fall.
Define gravity in one sentence? An invisible force that pulls objects together
An animation of gravity at work. Albert Einstein described gravity as a curve in space that wraps around an object—such as a star or a planet. If another object is nearby, it is pulled into the curve. Image credit: NASA
Anything that has mass also has gravity. Objects with more mass have more gravity. Gravity also gets weaker with distance. So, the closer objects are to each other, the stronger their gravitational pull is.
What makes gravity weaker? distance
Earth's gravity comes from all its mass. All its mass makes a combined gravitational pull on all the mass in your body. That's what gives you weight. And if you were on a planet with less mass than Earth, you would weigh less than you do here.
What does Earth’s gravity come from? mass
Look at the image below and write how much you’d weigh on the following planets if you weighed 100lbs on Earth.
Jupiter 253 lbs Mars 38 lbs Venus 91 lbs
Saturn 107 lbs Neptune 114 lbs
How much would you weigh on the moon? 17 lbs
Image credit: NASA
You exert the same gravitational force on Earth that it does on you. But because Earth is so much more massive than you, your force doesn’t really have an effect on our planet.
7. Why doesn’t your force really have much effect on Earth? Earth is much more massive than humans
Gravity in our universe
Gravity is what holds the planets in orbit around the sun and what keeps the moon in orbit around Earth. The gravitational pull of the moon pulls the seas towards it, causing the ocean tides. Gravity creates stars and planets by pulling together the material from which they are made.
8. What causes ocean tides? Gravitational pull of the moon pulling the seas towards it.
9. How does gravity create stars and planets? Pushing material together
Gravity not only pulls on mass but also on light. Albert Einstein discovered this principle. If you shine a flashlight upwards, the light will grow imperceptibly redder as gravity pulls it. You can't see the change with your eyes, but scientists can measure it.
Black holes pack so much mass into such a small volume that their gravity is strong enough to keep anything, even light, from escaping.
10. Why is gravity in black holes so strong that it keeps anything (even light) from escaping? Because nothing can escape black holes
What is a black hole?
a dead star
Watch this video to find out more about these areas of immense gravity!
Gravity on Earth
Gravity is very important to us. We could not live on Earth without it. The sun's gravity keeps Earth in orbit around it, keeping us at a comfortable distance to enjoy the sun's light and warmth. It holds down our atmosphere and the air we need to breathe. Gravity is what holds our world together.
11. What is the role of the sun’s gravity? Keep it away from us
12. Can humans live without gravity? no
However, gravity isn’t the same everywhere on Earth. Gravity is slightly stronger over places with more mass underground than over places with less mass. NASA uses two spacecraft to measure these variations in Earth’s gravity. These spacecraft are part of the Gravity Recovery and Climate Experiment (GRACE) mission.
13. Describe where Gravity in Earth is slightly stronger. The core
The GRACE mission helps scientists to create maps of gravity variations on Earth. Areas in blue have slightly weaker gravity and areas in red have slightly stronger gravity. Image credit: NASA/University of Texas Center for Space Research
GRACE detects tiny changes in gravity over time. These changes have revealed important details about our planet. For example, GRACE monitors changes in sea level and can detect changes in Earth’s crust brought on by earthquakes.
14. List 2 things that the GRACE mission can do for Earth.
i) detects tiny changes in gravity
ii) reveal important details about planets
15. Gravity on Mars
List 5 or more facts about GRAVITY ON MARS in the space below. You can copy and paste and add images. Save in your Hurumanu 3 File.
Its not heavy
You can almost fly
You feel lighter
Your faster
You move your body faster
