|The Big Bang 13.8 billion years ago and the expansion of the Universe|
Mankind has always been fascinated with the study of the cosmos that is so mysterious, vast and unfathomable. In 1609, Galileo made his rudimentary 37mm dia telescope. Since then, scientists have been using rapidly evolving tools and technology to study the Space outside. The James Webb Space Telescope (JWST) is now being made by NASA, which is thousands of times more powerful than earlier telescopes. It will give scientists the opportunity to clearly 'see' cosmic events, as they happen. The Hubble Telescope has been travelling on the Earth’s orbit, while JWST will go all the way out to locations that are 1.5 million kms away and follow the orbit of the Sun. The Universe is revealing more and more.
All this while, a genius called Einstein was thinking, “Events, even the minutest, take place at specific locations and at certain time. For example, a simple event like brushing one’s teeth or having a bath happens by occupying a certain space and within a particular time line. Thus every event has four dimensions – the three dimensions of space (length, height and depth) and the fourth dimension of time.Our Universe is a space-time continuum that is constantly expanding, thus creating a three dimensional space over a period of 13.8 billion years”. This space and time are interwoven into a single continuum known as space-time, which can be visualised a flat grid.
In 1915 Einstein realized that this flat space-time grid does not consider the gravitational force of large objects. Massive objects in space like the earth, planets, sun, stars caused a distortion in space-time as the gravity of that object curves the grid. Imagine setting a large cricket ball in the center of a trampoline. The ball would press down into the fabric, causing it to dimple. A marble rolled around the edge would spiral inward toward the body, pulled in much the same way that the gravity of a planet pulls at rocks in space.This is the essence of Einstein's General Theory of Relativity.
The gravitational force in some objects in the Universe becomes so powerful and pulls down the space-time grid to such an extent that creates “Black Holes” that are so deep and dark that, even light cannot get out. Celestial bodies including stars collapse in these black holes. Because no light can get out, people can't see black holes. They are invisible. Black holes can be big or small, ranging from less than an atom to “supermassive” that are more than 1 million suns together.
Suppose that there is a star about 20 times more massive than the Sun. When this star runs out of fuel, the gravity will overwhelm the natural pressure that the star maintains to keep its shape stable. As the pressure from nuclear reactions collapse, gravity will violently overwhelm and collapse the core. Other layers will be flung into space called supernova. The remaining core collapses into a gravitational singularity- a one-dimensional point which contains infinite mass in an infinitely small space, leading to tremendous energy. The gravity becomes infinite and space-time curves infinitely, and where the laws of physics, as we know them, cease to operate.
A mention of the black holes was also made in the ancient Indian scripture, Mandukya Upanishad (400 BC) which talks about Vishwaruchi that absorbs everything in the Universe - black hole.