The effects of gravitySome people fear that when they are outside, if they do not keep a good grip on the ground, they will fly into space. They don't really need to worry about this, as gravity usually prevents this sort of thing from happening. The fact is that no one really knows what causes gravity, but its effects have been studied by many physicists and astronomers. Three of the most obvious effects of gravity are objects falling, weight, and the fact that the Moon and planets stay in their orbits. People have generally learned to accept that if one drops one's precious and valuable textbook while stepping in a mud puddle, the book will invariably end up in the puddle and will therefore be deprived of all value and even readability. gravitational attraction between objects of large mass, such as the Earth, and objects of small mass, such as a book. The only problem with this relatively simple explanation is that no one really knows why this is so. What people have understood so far is that gravity is a force, and a force is anything that changes the resting state or motion of an object. In the absence of external forces, the dynamics of a system remains constant. This means that if there were no gravity, when we let go of the manual, it would remain at rest in the air. If a force acts on a body, it accelerates in the direction of the force. In the example of the force of gravity, small things like textbooks are pulled down, toward the center of the great mass of the Earth, not out into space, although some think that might happen. Torgerson 2 Isaac Newton was the first to conceive of weight. like the gravitational attraction between a body and the Earth. The force that results from the Earth's gravitational pull on bodies on its surface is what we call weight. Science has chosen to measure the mass of objects in units that are roughly equivalent to the weight of those objects on Earth. For example, if a textbook weighs four pounds on Earth, its mass would be four pounds in an orbiting spacecraft. The manual would be "weightless" because it would not feel the gravitational pull of the Earth, but, even in space, to push the