gravity facts

Objects with mass are attracted to each other, this is known as gravity. Gravity keeps Earth and the other planets in our solar system in orbit around the Sun. It also keeps the Moon in orbit around Earth. Tides are caused by the rotation of the Earth and the gravitational effects of the Moon and Sun. Because Mars has a lower gravity than Earth, a person weighing 200 pounds on Earth would only weigh 76 pounds on Mars. It is thought that Isaac Newton’s theories on gravity were inspired by seeing an apple fall from a tree. While Newton’s older law of universal gravitation is accurate in most scenarios, modern physics uses Albert Einstein’s general theory of relativity to describe gravity. Acceleration of objects to due to the gravity on Earth is around 9.8 m/s2. If you ignore air resistance (drag) then the speed of an object falling to Earth increases by around 9.8 metres per second every second. The force of gravity 100 kilometres (62 miles) above Earth is just 3% less than at the Earth’s surface. The human body can handle increased g-forces as seen in activities such as dragster races, airplane acrobatics and space training. The highest known acceleration voluntarily experienced by a human is 46.2 g by g-force pioneer John Stapp. While formula one racing drivers may feel around 5 g’s under heavy braking, they can experience over 100 g’s if a crash causes them to decelerate extremely quickly over a very short distance. Some roller coasters have been known to include g-forces of around 4 to 6 g. The higher something is, the greater its gravitational potential energy. Back in the Middle Ages, weapons called trebuchets were used to take advantage of this principle, using mechanical advantage and the gravitational potential energy of a counterweight to hurl rocks and other projectiles at or over walls. In modern times we use the gravitational potential of water to create hydroelectricity.