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Sreeram Padmanabhan
Edge of Forever by Carl Sagan (Cosmos)

 

If you want to know what it's like inside a black hole look around. But we don't yet know whether the universe is open or closed. More than that, some astronomers doubt that the red shift of distant galaxies is due to the Doppler effect. They are skeptical about the expanding universe and the big bang. Perhaps our descendants will regard our present ignorance with as much sympathy as we feel to the ancients for not knowing whether the Earth went around the sun.

If the general picture, however, of a Big Bang followed by an expanding universe is correct - what happened before that? Was the universe devoid of all matter and then the matter suddenly somehow created? How did that happen? In many cultures, a customary answer is that a "God" or "Gods" created the universe out of nothing, but if we wish to pursue this question courageously, we must, of course, ask the next question - where did God come from? If we decide that this is an unanswerable question, why not save a step and conclude that the origin of the universe is an unanswerable question? Or if we say that God always existed, why not save a step and conclude that the universe always existed? There's no need for a creation, it was always here. These are not easy questions. Cosmology brings us face to face with the deepest mysteries, with questions that were once treated only in religion and myth.

"Who knows for certain? Who shall here declare it? Whence was it born? Whence came creation? The Gods are later than this world's formation, who then can know the origins of the world? None knows whence creation arose or whether he has or has not made it - he who surveys it from the lofty skies. Only he knows, or perhaps he knows not." These words are 3500 years old. They're taken from the Rigveda: a collection of early Sanskrit hymns. The most sophisticated ancient cosmological ideas came from Asia and particularly from India. Here there's a tradition of sceptical questioning and unselfconscious humility before the great cosmic mysteries. Amidst the routine of daily life, in say the harvest and winnowing of grain, people all over the world have wondered, where did the universe come from? Asking this question is a hallmark of our species. There's a natural tendency to understand the origin of the cosmos in familiar biological terms - the mating of cosmic deities or the hatching of a cosmic egg or maybe the intonation of some magic phrase. The big bang is our modern scientific creation myth, it comes from the same human need to solve the cosmological riddle.

Most cultures imagine the world to be only a few hundred human generations old. Hardly anyone guessed that the cosmos might be far older but the ancient Hindus did. They, like every other society, noted and calibrated the cycles in nature: the rising and setting of the sun and stars; the phases of the moon; the passing of the seasons. All over south India, an age old ceremony takes place every January, a rejoicing in the generosity of nature in the annual harvesting of the crops. Every January nature provides the rice to celebrate Pongal. Even the drought animals are given the day off and garlanded with flowers. Colourful designs are painted on the ground to attract harmony and good fortune for the coming year. Pongal, a simple porridge - a mixture of rice and sweet milk - symbolizes the harvest; the return of the seasons. However this is not merely a harvest festival, it has ties to an elegant and much deeper cosmological tradition.

The Pongal festival is a rejoicing in the fact that there are cycles in nature, but how could such cycles come about unless the Gods willed them and if there are cycles in the years of humans might there not be cycles in the eons of the Gods? The Hindu religion is the only one of the world's great faiths dedicated to the idea that the cosmos itself undergoes an immense, indeed an infinite, number of deaths and rebirths. It is the only religion in which the time scales correspond, no doubt by accident, to those of modern scientific cosmology. Its cycles run from our ordinary day and night to a day and night of Brahma; 8.64 billion years long. Longer than the age of the earth or the sun, and about half the time since the Big Bang - and there are much longer time scales still.

There is the deep and appealing notion that the universe is but the dream of the God who, after a hundred Brahma years, dissolves himself into a dreamless sleep and the universe dissolves with him until after another Brahma century he stirs, recomposes himself and begins again to dream the great cosmic lotus dream. Meanwhile, elsewhere there are an infinite number of other universes each with its own God dreaming the cosmic dream. These great ideas are tempered by another, perhaps still greater. It is said that men may not be the dreams of the Gods but rather that the Gods are the dreams of men.

In India, there are many gods and each god has many manifestations. These Chola bronzes cast in the eleventh century include several different incarnations of the god Shiva. Seen here at his wedding. The most elegant and sublime of these bronzes is a representation of the creation of the Universe at the beginning of each cosmic cycle – a motif known as the cosmic dance of Shiva. The god has four hands. In the upper right hand is the drum whose sound is the sound of creation. And in the upper left hand is a tongue of flame… a reminder that the universe now newly created, will billion of years from now will be utterly destroyed. Creation. Destruction.

These profound and lovely ideas are central to ancient Hindu beliefs as exemplified in this Chola temple at …. They are kind of reminiscent of modern astronomical ideas. Without doubt the universe has been expanding since the big bang but it is by no means clear that it will continue to expand for ever. If there is less than a certain amount of matter in the universe, then the mutual gravitation of the receiving galaxies will be insufficient to stop the expansion and the Universe will run away forever. But if there is more matter than we can see…hidden away in black holes… say or in hot but invisible gas between galaxies, then the universe holds together, and partakes in every Indian succession of cycles… expansion followed by contraction… cosmos upon cosmos…Universes without end. If we live in such an oscillating universe, then the Big Bang is not the creation of the cosmos but merely the end of the previous cycle the destruction of the last incarnation of the cosmos.

Neither of these modern cosmologies may be altogether to our liking. In one cosmology, the universe is created somehow from nothing 15 to 20 billion years ago and expands forever. The galaxy is mutually receding until the last one disappears over our cosmic horizon. Then the galactic astronomers are out of business… the stars cool and die…matter itself decays…and the Universe becomes a thin cold haze of elementary particles.

In the other, the oscillating universe, the cosmos has no beginning and no end… and we are in the midst of an infinite cycle of cosmic deaths and rebirths. With no information trickling through the cusps of the oscillation…nothing of the galaxies, stars, planets, life forms, civilizations evolved in the previous incarnation of the universe trickles through the cusp filters past the Big Bang to be known in our universe.

The death of the universe in either cosmology may seem little depressing. But we may take some solace in the time scales involved. These events will take tens of billions of years or more. Human beings or our descendants whoever they might be can do a great deal of good in the tens of billions of years before the cosmos dies.

If the universe truly oscillates, still stranger questions arise. Some scientists think that when expansion is followed by contraction, when the spectra of distant galaxies are all blue-shifted, causality will be inverted and effects will precede causes. First the ripples spread from a point on the water’s surface, then I throw a stone into the pond.

Some scientists wonder about what happens in an oscillating universe at the cusps, at the transition from contraction to expansion. Some think that the laws of nature are then randomly reshuffled, that the kind of physics and chemistry that orders this universe represent only one of an infinite range of possible natural laws. It is easy to see that only a very restricted range of laws of nature are consistent with galaxies and stars, planets, life and intelligence. If the laws of nature are randomly reshuffled at the cusps, then it is only by the most extraordinary coincidence that the cosmic slot machine has this time come up with a universe consistent with us.

Do we live in a universe that expands forever or in one in which there is a nested set of infinite cycles? There are ways to find out: not my mysticism, but through science - by making an accurate census of the total amount of matter in the universe, or by seeing to the edge of the Cosmos.

Radio telescopes are able to detect distant quasars billions of light-years away expanding with the fabric of space. By looking far out into space we are also looking far back into time back toward the horizon of the universe back toward the epoch of the big bang. Radio telescopes have even detected the cosmic background radiation. The fires of the big bang cooled and red-shifted faintly echoing down the corridors of time. This is the very large array a collection of 17 separate radio telescopes all working collectively in a remote region of New Mexico. Modern radio telescopes are exquisitely sensitive.

A distant quasar is so faint that its received radiation by some such telescope amounts to maybe a quadrillionth of a watt. In fact, and this is a reasonably stunning piece of information the total amount of energy ever received by all the radio telescopes on the planet Earth is less than the energy of a single snowflake striking the ground. In detecting the cosmic background radiation in counting quasars in searching for intelligent signals from space radio astronomers are dealing with amounts of energy which are barely there at all. These radio telescopes, rising like giant flowers from the New Mexico desert are monuments to human ingenuity. The faint radio waves are collected, focused assembled and amplified, and then converted into pictures of nebulae, galaxies and quasars. If you had eyes that worked in radio light they'd probably be bigger than wagon wheels and this is the universe you'd see. An elliptical galaxy, for example leaving behind it a long wake glowing in radio waves. Radio waves reveal a universe of quasars interacting galaxies, titanic explosions. Every time we use another kind of light to view the cosmos we open a new door of perception. As the murmurs from the edge of the cosmos slowly accumulate our understanding grows. This is an exploration of the ancient and the invisible a continuing human inquiry into the grand cosmological questions. Another important recent finding was made by x-ray observatories in Earth orbit. Artificial satellites launched to view the sky not in ordinary visible light, not in radio waves but in x-ray light. There seems to be an immense cloud of extremely hot hydrogen glowing in x-rays between some galaxies.

Now, if this amount of intergalactic matter were typical of all clusters of galaxies then there may be just enough matter to close the cosmos and to trap us forever in an oscillating universe. If the cosmos is closed there's a strange, haunting, evocative possibility one of the most exquisite conjectures in science or religion. It's entirely undemonstrated it may never be proved, but it's stirring. Our entire universe, to the farthest galaxy, we are told is no more than a closed electron in a far grander universe we can never see. That universe is only an elementary particle in another still greater universe and so on forever.

Also, every electron in our universe, it is claimed is an entire miniature cosmos containing galaxies and stars and life and electrons. Every one of those electrons contains a still smaller universe an infinite regression up and down. Every human generation has asked about the origin and fate of the cosmos. Ours is the first generation with a real chance of finding some of the answers. One way or another we are poised at the edge of forever.

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