 Every object in the universe that has mass exerts a gravitational pull, or force, on every other mass. The size of the pull depends on the masses of the objects. You exert a gravitational force on the people around you, but that force isn't very strong, since people aren't very massive. When you look at really large masses, like the Earth and Moon, the gravitational pull becomes very impressive. The gravitational force between the Earth and the molecules of gas in the atmosphere is strong enough to hold the atmosphere close to our surface. Smaller planets, that have less mass, may not be able to hold an atmosphere. Show Planetary GravityObviously, gravity is very important on Earth. The Sun's gravitational pull keeps our planet orbiting the Sun. The motion of the Moon is affected by the gravity of the Sun AND the Earth. The Moon's gravity pulls on the Earth and makes the tides rise and fall every day. As the Moon passes over the ocean, there is a swell in the sea level. As the Earth rotates, the Moon passes over new parts of the Earth, causing the swell to move also. The tides are independent of the phase of the moon. The moon has the same amount of pull whether there is a full or new moon. It would still be in the same basic place.We have to bring up an important idea now. The Earth always produces the same acceleration on every object. If you drop an acorn or a piano, they will gain velocity at the same rate. Although the gravitational force the Earth exerts on the objects is different, their masses are just as different, so the effect we observe (acceleration) is the same for each. The Earth's gravitational force accelerates objects when they fall. It constantly pulls, and the objects constantly speed up. They Always ask About FeathersWhat About the Moon?But what keeps the Moon from falling down, if all of this gravity is so strong? Well, the answer is that the moon IS falling; all the time, but doesn't get any closer to us! Remember that if there wasn't a force acting, the Moon would be traveling in a straight line. Because there IS a force of attraction toward the Earth, the moon "falls" from a straight line into a curve (orbit) around the Earth and ends up revolving around us. The Earth's gravity holds it in orbit, so it can't just go off in a straight line. Think about holding a ball on a string and spinning it in a circle. If you were to cut that string (no more gravity), the ball would fly off in a straight line in the direction it was going when you cut the string. That direction, by the way, is not directly away from your hand, but tangent to the circle. Tangent is a geometry term used to describe a direction that are related to the slope of a curve. Math stuff. The pull of the string inward (toward your hand) is like the Earth's gravitational pull (inward toward the center of the Earth).
Or search the sites for a specific topic. How Gravity Affects Molecules (NASA-eClips Video)
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 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 answer 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. 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. 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. 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. Gravity in our universeGravity 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. 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. Gravity on EarthGravity 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. 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. 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. The gravitational force of earth is responsible for holding the atmosphere above the earth. It is also the gravitational force of earth which keeps us firmly on the ground. Various objects attract each other due to gravity only. This article deals what is gravitational force and how this force holds the Solar System together.
As we know that force is necessary to produce motion in a body. If any object falls from some height towards the earth, therefore a force must be acting on it. This force is due to the attraction between the earth and the object which is known as Gravitational Force of earth or gravity of earth. Similarly, a leaf falls down from a tree due to gravity of earth. In fact earth attracts or pulls all the objects towards its centre. The gravitational force of the earth is responsible for holding the atmosphere above the earth; for the rain falling to the earth; and for the flow of water in the rivers. It is also the gravitational force of earth, which keeps us firmly on the ground. Though the various objects on this earth attract one another constantly, they do not cause any motion because the gravitational force of attraction between them is very small. When two bodies or objects are very big, having large masses, then the gravitational force of attraction between them becomes extremely large. For example the sun, the moon and the earth have extremely large masses, therefore, the gravitational force of attraction between the sun and the earth or other planets or between the earth and the moon, is extremely large. Through this article we will discuss how gravitational force holds the solar system together. First it is necessary to understand that every object in the Universe attracts every other object
Source: www.image.slidesharecdn.com Do you know why Saturn have rings and how they are formed?We know that when we drop a ball from a certain height, it falls towards the earth. This means that the earth attracts the various objects towards its centre. According to Newton, it is not only the earth, which attracts the objects, in fact, every object attracts every other object with a certain force. The force with which two objects attract each other is called gravitational force or gravity. The gravitational force between two objects, acts even if the two objects are not connected by any means. But if the masses of the objects are small, then the gravitational force between them is very small which cannot be detected easily. For example, two stones lying on the ground attract each other, but since their masses are small, the gravitational force of attraction between them is small and hence we do not see one stone moving towards the other stone. If, however, one of the objects is very big having a large mass, then the gravitational force becomes very large and its effect can be seen easily. How gravitational force holds the solar system together? In the Solar System, planets move in circular orbits around the sun; and satellites move in circular orbits around the planets. A centripetal force is needed to make an object move in a circular orbit or circular path. Now,the question arises what is centripetal force?
Source: www.wikimedia.org.com A centripetal force is not a fundamental force, but a net force which causes an object to move in a circular path. It is directed towards the centre around which the body is moving. In the case of planets moving around the sun, the centripetal force is provided by the gravitational force of the sun. And in the case of satellites moving around the planets, the centripetal force is provided by the gravitational force of the planets. In the case of ‘the sun and the earth’ Since the masses of the sun and the earth are very, very large, they exert very large force on one another. It is the gravitational force between the sun and the earth, which keeps the earth in uniform circular motion around the sun. In the case of ‘the earth and the moon’ It is the gravitational force between the earth and the moon that makes the moon revolve at uniform speed around the earth. Thus, the gravitational force is responsible for the existence of our solar system. Due to this force motion of planets around the sun; motion of the moon around the earth; formation of tides in the sea etc. took place or can be explained.From the above article it is clear that what is gravitational force, centripetal force, how gravitational force holds the solar system together. Do you know that our moon is made up of 20 smaller moonlets? |
Explain whether that is the only gravitational force that affects objects in our solar system.
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