Category Archives: Astronomy

Life, The Cosmos And Everything

“How much would you pay for the Universe?”, was the question asked by Dr. Neil deGrasse Tyson. What is the universe worth? There is a curious school of thought which makes some regard themselves as above and beyond the world. They seem to look at the Cosmos with a strange detachment – as if they can divine it without discovering anything about themselves.

But we are part of the Cosmos. Inextricably so. To know the Cosmos is to know ourselves.

There are some who would rather not think of such things. Some who question those whose business it is to question. “Why do you want to know?”, they ask. Some want to give up even before they begin. Should we let sleeping dogs lie?

Yet, our curiosity has long been the hallmark of our species. We want to know. Is there any evolutionary advantage to this? Perhaps. I will leave that to the biologists. But what is certain is that this curiosity has served us well over the millenia.

There are some traits which we have not been able to shake off. We tend to group ourselves within clusters without realizing that we are connected to everyone else. Before we are black or white or brown; before we are Indians, Americans or Chinese; before we are Hindus, Muslims and Christians, we are human. We are the descendants of a tribe of bushmen who migrated from Africa more than 50000 years ago. Will we ever appreciate that?

Going back even further, we are connected to every living thing on this planet. From the humblest bacterium to the most gigantic mammal, we share the essential building blocks of life. We are nothing but combinations of chemicals which, for an unknown reason, gained consciousness and populated the planet in an explosion of life. Will we look at a chimpanzee and realize that our DNA differs by around 2%; that we share a common ancestor?

And finally, the most poetic fact about the Cosmos. We are connected to literally everything we see. Every bit of matter is made of atoms, atoms that were spewed from the explosions of entire stars billions of years in the past. When you die, your body disintegrates and the atoms that make you, go back to the Cosmos. Parts of you will end up as other people, parts of you as a rock, you will end up in the ocean, in trees, in grass, in the air and a part of you will reach the stars. When you consider this, you realize how small minded you are when you worry about the little things. And you realize how absurd it is to fear death or to imagine a heaven where you spend an eternity in boredom.

The Cosmos made you, you are part of it. It is all that is within and without. Enjoy your moment under the sun and live your life free because really, there is nothing to fear. The Cosmos will take care of you.



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Of Slot Machines and Singularities

If one has ever played at a slot machine in a casino, one knows that the money put inside usually disappears once that lever is pulled. There are no returns and you are left looking foolishly at the machine and inevitably trot off to get some more spare change in the hopes of recovering your coins. The perfect term to describe a slot machine in a casino is a black hole.

What then is a black hole? We have all heard about them, some of us have a vague notion about a black hole but what does it imply? To put it in a single sentence, a black hole is a region in space-time which has a gravitational pull so strong, that not even light can escape it. That sentence probably raises more questions. And there are answers. And, as always, the profound genius of Albert Einstein is deeply involved.

In 1915, Einstein developed his theory of general relativity which incorporate 10 equations that describe how gravity is the result of space and time being curved by matter and energy.  The simplest way to perceive gravity as a result of an interaction between matter and space-time is to imagine a sheet of rubber held taut at all ends. If a ball is placed in the center, there will be a bulge in the sheet. If a smaller marble was placed on the sheet, it would inevitably fall towards the large ball. This, according to Einstein, is how gravity works. If you imagine the Sun to be the ball in the center and the marble to be Earth, you can understand how gravity works and is actually a result of this humongous mass of the sun literally bending space and time.

Now coming back to Enistein’s field equations, Karl Schwarzschild found a solution to these equations that described the gravitational field of a point mass. This, indeed, is what a black hole essentially is. What the solutions said were that there could theoretically be some regions in space where a point could have infinite density and zero volume and this point is called a singularity.

The existence of black holes was predicted in 1916 but at the time scientists were not even certain of the existence of other galaxies. It took Edwin Hubble to prove conclusively that other galaxies existed and that the universe is far larger than we even imagined. And that wasn’t all; his work also led to the theory of metric expansion of space. What that means is that space itself is expanding (incidentally the 2011 Nobel prize in physics was awarded to scientists who proved that this expansion is occurring at an accelerating rate).  This has profound implications. If the universe is expanding, that means that there must have been a time when it was infinitesimally small. And this conclusion is what makes black holes even more interesting.

How does a black hole come to be? Let’s suppose you have a table and you start to load it with heavy books. The internal force of the table will keep it propped up to a point when the books are too heavy and the table collapses to the ground under the force of gravity, which is pulling down the books towards the center of the earth. Now in space there is no “ground”. If a spherical body is so overloaded, there will be a point when it’s internal force is utterly powerful against the forces of gravity and it collapses – into itself.

A black hole is formed when certain types of stars die. A star is nothing but a giant nuclear reactor in space. The fusion process in the core of a star converts matter into energy and also resists the force of gravity – which tends to make the star collapse in on itself. But something’s got to give and when the star eventually runs out of fuel, gravity wins. The core collapses in on itself so that a mass of several times the mass of the sun is squeezed into a point of infinite density – a singularity. The outer layers of the star are shed in a spectacular supernova explosion, which sometimes outshine the entire parent galaxy. What remains is the black hole.

N0w the black hole is not just the singularity itself. There is another important term that concerns black holes and that is the event horizon. The escape velocity of earth is 11 km/sec. That means that a spaceship has to exceed this speed to break out of earth’s gravitational field. The escape velocity of the sun is around 600 km/sec. Generally, the heavier the object, the higher the escape velocity. What if you had an object that was so heavy and dense that it’s escape velocity exceeded the speed of light? Since nothing can go faster than the speed of light, nothing can escape the gravitational pull of this dense object and this is another way to understand the black hole. The event horizon of a black hole is a region around the black hole beyond which light cannot escape. Nothing inside the event horizon can be perceived by an outside observer. If we send a probe to a black hole, once it has passed the event horizon, it is lost to us forever. And strangely, inside the event horizon, space and time do not make sense. Time literally stops.

When we see an object, why we see it is because light rays are reflected from that object. But in a black hole, any light that falls onto it, can never escape it. Hence a black hole can never be seen. How then can a black hole be detected? For one, if there is a black hole between the observer and a region of space, the light from the space beyond the black hole is bent by the gravity of the black hole. This gravitational “lensing” points to the existence of a black hole.

So there’s the lowdown. Black holes are quirky objects in space which mess up space-time. But what makes them really interesting and ties them so deeply to our own questions about the origin of the universe? Theories now suggest the existence not of just our own universe, but many universes – a multiverse in which our universe is just one.

What happens inside the singularity? Physics as we know it loses it’s meaning. Could it be that a black hole contains a wormhole to another point in our universe or another universe altogether? What if, at the end of a black hole is a white hole? A singularity into which nothing can go in. Now the true implications of the theory of metric expansion of space come to the fore. If space is currently expanding, at some point it must have been a singularity. Everything was expelled outwards from this singularity. Could the creation of our universe merely be the outcome of the formation of a black hole in another? Could the millions of black holes that exist in space point to the creation of millions of different universes? One can only dream about finding out.

Till then, I shall go get my quarters for the slot machines.

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