## Jun 8 Forces of Nature Series : Gravity

Gravity, one of science and nature's biggest mysteries and of all the forces of Nature, the least understood. Out of all the forces Gravity is the weakest and the weakest by far. Gravity, like the other forces of nature, came into existence very soon after the instant of the Big Bang and held its influence on the expanding and cooling universe. The attraction of Gravity eventually caused early gases to form stars and planets etc.

Think of this, gravity as we loosely understand it can keep our planet orbiting the sun and the sun orbiting the centre of galaxy but if we jump up and down we can overcome it! A colossal force of nature that keeps order and alignment in the cosmos can be overcome by us weak and feeble humans here on Earth.

From the strong nuclear force and weak nuclear force the protons, neutrons and atomic nuclei as a whole can be observed to develop an understanding of the forces themselves. Gravity doesn't have a matter make up. The closest physicists have come is the Graviton, a hypothetical particle that forms a composite make up of matter with gravitational effect.

As always I love to debunk common misconceptions about science. Gravity isn't actually a downward force. If you are in a car and the accelerator is pressed hard it will push you back into the seat. So that places gravity as in and down making it radially inward. Radially inward gravity also explains why planets and stars are spherical as opposed to flat.

Gravity in its true definition is an attractive force. The phenomenon brings all things with mass together. In the 17th Century Issac Newton formed the best mathematical basis for understanding gravity. He concluded that the net force of gravity can be measure by multiplying the mass of two objects like the Earth and Moon as an example and dividing by the distance between them.

Earths gravity, often referred to as free fall is 9.8 metres per second squared near the surface. Earth's surface gravity. Depending on pressure, density and the force of a planet this measure can vary from planet to planet or moon to moon.

Irregular patterns in the orbit of Uranus actually contributed to the discovery of Neptune using Newton's laws of gravitation. For the following 200 years or so, gravity was an undisputed force and had very little opposition and universal agreement.

Einstein's General Relativity gives the most accurate understanding of our notion of gravity. I have written about this previously but will give Relativity a bigger series in the future. Relativity postulates that gravity is a manifestation of a curved spacetime. Please don't mix up spatial curvature and the curvature of space and time. The curviture as a rule of thumb increases as you go closer to a centre of mass. Time slows closer to the centre of mass to an outside observer. Black holes have the most extreme curvature in the universe so for an outside observer time actually stops. If you were standing on the Earth watching someone fall into a black hole, to your eye that person would be falling forever. For the person inside the hole, all of time would pass them by. All of it!

Gravity has caused the most debate and discussion over the centuries. Do we know what it is? Technically speaking no! We can see the effect it has on objects and bodies we can see and feel but the actual gravity itself we cannot. We can only go on what our minds and measurements believe it is!

Jude Morrow