Gravity

This time I am going to talk about Gravity and how it affects us and the Universe.

Have you ever wondered how and why the Earth orbits the Sun or the Moon orbits the Earth? You might say that the Sun's gravity keeps the Earth on track and the Earth's gravity keeps the Moon orbiting the Earth. But shouldn't the gravity of the Sun just pull the Earth towards it instead of having it revolve around it? Well, this does not happen because Space behaves like a fabric.

Anything that has a mass has its own gravity. Yes I have my own gravity and you too. Even tiny dust particles have their own gravity even though you don't notice it. And when anything has gravity, it bends the fabric of Space. Lets say you have a piece of cloth/paper (fabric of Space) and you stretch it so that it's flat but slightly relaxed at the same time. You then put a ball (the Sun) on top of it and notice how the fabric bends inwards.

This is the similar to what happens in space. No, space does not bend like a fabric, but it acts like it does. All objects bend space forming a gravitational cone, with the object being in the middle. The Sun's gravitational cone is huge, it extends out much further than the Solar System.  An object's gravitational cone depends on the mass (and not the size) of the object.

If the gravitational cone is big enough, the object can have a satellite orbiting around it. The Earth is a satellite of the Sun and so are the other planets in the Solar System. The Sun's gravitational cone keeps the planets in orbit.

Let's say that the Sun's gravitational cone is an actual cone and a ball is going around the centre of the cone. If the ball is going too slow, it will spiral inwards and fall into the centre. If it's going too fast, it will spiral outwards and fall off the edge of the cone. If it's going on a steady pace and not too fast or slow, it will maintain a steady orbit around the centre. The moon maintains a steady orbit around the Earth and the Earth maintains a steady orbit around the Sun. If Earth was going too slow, we would have crashed into the Sun by now!

Gravity is also capable of bending light! Albert Einstein first suggested that gravity bends light.To confirm this, a detailed experiment was carried out by Sir Arthur Eddington in 1919 (during a solar eclipse). The results were analysed, and in 1920, it was confirmed that gravity bends light. What happened in this experiment to prove thus? During the solar eclipse Eddington could clearly see the stars, hitherto not seen due to the overwhelming brightness of the Sun. The eclipse blocks this dazzle to some extent making the stars visible. What Eddington saw, however, was interesting: the stars appeared to be a little more closer to the Sun than their normal position. Why? This was because the light of those stars had bend towards the Sun due to the gravitational pull of the Sun. This phenomenon is called the Gravitational lens of the Sun. All star that are big enough to have a gravity that strong have a gravitational lens.

I will soon create a link explaining through a video how this gravitational lens works.

In all, the Universe depends on gravity and it would be impossible for life to survive without it.

Although the Universe depends on it, gravity can also turn into the most dangerous things in the Universe. These dangerous things are called black holes.

I will talk about black holes in my next blog.