UCSB Science Line Why the sun does not fall on the earth? Question Date: 2014-08-30 Answer 1: The earth and the sun are about 93,000,000 miles apart. If the earth did not orbit the sun and became stationary (this can't happen, but if it did) the sun and earth would attract each other and the earth, being smaller, would fall into the sun. Otherwise, it is because earth has a lot of momentum. If the sun were to disappear, the earth would fly away straight rather than continuing to circle the sun. So, the earth has two main forces: inertia, to keep moving straight, and the gravity, to pull it to the sun. It moves in an average of the two directions, as in this image, and moves in a circle around the sun. click here to watch Answer 2: Everything we see on earth involving gravity is misleading when it comes to the solar system. You see, everything on Earth---the air, the rocks and you and I are attracted towards the CENTER of the Earth. A basic law of nature says that any two objects of mass M and mass m are attracted to each other with a force that is equal to the product of the masses divided by the distance between them squared, that is F= M*m/R2. So if we consider YOU and the Earth we can pretend that the mass of Earth is concentrated at the center... so the R is the radius of Earth (since you are on the surface). Now we can think about earth and Sun. The Earth is indeed attracted to the SUN. IF WE COULD STOP THE EARTH’S motion and then let go, indeed the earth WOULD accelerate and fall into the sun! The reason why it does not is because of Newton’s first law of motion. This first Newton’s law of motion says that if a body is in motion, it remains in motion unless acted upon by a force. So billions of years ago, the cloud of gas and dust from which the earth is made was in circular motion around the sun, in other words, the protoearth had a velocity INITIALLY that was tangential to its current orbit. This inertia remains today because there is no way the sun can remove the energy directed TANGENTIAL to the sun-Earth line. I realize this explanation may be confusing, but do not feel bad about it, it took humanity thousands of years to figure this out. You might want to find a simple book on NEWTON’S Laws, this book will help explain what I have written above. These are very deep and profound concepts, it takes some years to fully understand this, but it is never too soon to start trying!!! Answer 3: The sun is so much bigger than the Earth that a better question is "why does the Earth not fall into the sun?" The answer is something called 'momentum' - the property of moving objects that causes them to continue moving. The Earth is in orbit around the sun; without the sun's gravity, the Earth would coast off into space, but because the Earth is moving and is moving as fast as it is, it can't just fall into the sun. So, instead, it falls around the sun, i.e. an orbit. Answer 4: The sun and the earth are both in space, where gravity doesn't look quite the same as it does here on earth. The gravity of a planet or sun is to the middle of the planet -- we're on the surface of the earth so everything falls down. But in space there isn't an up or down! When we say that the earth orbits around the sun, that doesn't mean that it's above or below it, but that it's going in a circle around it. The earth is attracted to the sun and the sun to the earth, but we're so far away that the gravity force that attracts us isn't strong enough for the sun to come close enough to actually fall on us (thank goodness!!) Answer 5:Good question! All massive objects in our universe are attracted to each other through a force known as gravity. If gravity were the only force acting between the sun and earth, the two bodies would indeed collapse on one another. Therefore, there must be other forces acting on this system. Remember that the earth, and all the other planets in our solar system, revolve around the sun. Because the earth is in a rotational orbit, there is another force acting on the planet. This force is known as centrifugal force. The direction of the centrifugal force on the earth is opposite the direction of the gravitational force (see the diagram below), so it prevents the sun and earth form collapsing into each other. earth-sun diagram Centrifugal force acts on a rotating object in a direction opposite the axis of rotation. Imagine that you have a tennis ball tied to a string. If you swing the tennis ball on the string around in a circle, you would feel the ball tugging on the string. That is the centrifugal force on the ball. It is counteracted by tension in the string that you are holding. In this example, the tension force in the string is like the gravitational force between the earth and the sun. The ball doesn't get closer or farther from your hand. If you suddenly cut the string, the ball would go flying away, but that wont happen to the earth because of the sun's gravity. Click Here to return to the search form.    Copyright © 2017 The Regents of the University of California, All Rights Reserved. UCSB Terms of Use