69 Gravity in the Solar System-Mid

Gravity in the Solar System FOCUS Question How does gravity affect objects in the solar system?

Gravity and Weight Imagine walking on the Moon. You have to wear a heavy spacesuit to protect you because there is no oxygen. Imagine how hard it would be to move around with all that heavy gear. Actually, it would be much easier than you think! On Earth, your weight is caused by gravity pulling your mass toward the center of the planet. The Moon has much less mass, or total amount of matter, than Earth, so its gravitational pull is much weaker. On the Moon, your mass does not change, but you would weigh one-sixth of what you weigh on Earth. The gear you are wearing would also be much lighter. Your muscles however, are just as strong on the Moon as on Earth. It is much easier to lift your body and your spacesuit off the surface. Astronauts on the Moon had to move very carefully to avoid stepping or jumping too far. It's all about mass and gravity, but what is gravity?

Gravity and Distance Gravity is a force that attracts all objects to each other. How strongly they are attracted depends on two key factors: the masses of the objects and the distance between them. Two large, rocky asteroids in space attract one another because of gravity. If they are far apart, the force is very weak. If they begin to move toward one another, the force increases They may pull together and form one larger asteroid. Do You Know? A meteor is a piece of rock that gets close to Earth. Earth's gravity pulls it down. You might see a streak of light in the sky as the meteor burns up in our atmosphere.

Gravity and Mass Are you and the classmate sitting next to you pulled together by each other's gravitational force? Yes, you are! Gravity attracts you to your pencil and to the bird outside your window and to any other objects that have mass, but it is hard to notice small pulls of gravity. Even large buildings are not massive enough to cause noticeable attraction. Earth's pull on these objects is much greater than the pull of these objects on each other, because Earth is so much more massive than they are. The more massive, the stronger the attraction. Objects like moons, planets, and stars have a noticeable gravitational pull. Math Moment From weakest to strongest, order the strength of the gravitational attraction between Earth and each object in this picture: the student, the building, and the ice cream cone.

Gravity and the Moon Earth's gravity keeps the Moon orbiting Earth once every 27.3 days. The Moon pulls on Earth, too. causing ocean tides. Water on the side of Earth facing the Moon. is pulled toward the Moon This causes a high tide As the Moon pulls on Earth, the water on the opposite side gets left behind. This causes a high tide on that side, too. Low tides occur between the high tides. As Earth rotates, each coastal location passes through high and low tides twice a day.

The Sun and the Planets You probably know that Earth orbits the Sun. It is the Sun's gravity that keeps Earth and the other planets in the solar system orbiting around it. Can you guess what determines the strength of the gravitational pull between each planet and the Sun? It is the mass of each planet and its distance from the Sun.