by S. Prasad Ganti

Two questions interested me since my early years. One is what happened before ?  Another is what lies beyond ? Scientific advances over the years have lighted these two paths to an extent. But the path stretches beyond the known horizons. Both the space and time seems to stretch beyond the known limits.

Let us get to what lies beyond. From the street we live in, we go beyond the city and the country to the whole world. Then the planets of the solar system. And the billions of stars like our sun, making up our Milky Way galaxy. Galaxies clustering together with intervening voids make up our universe. Galaxies also have corpses of dead stars like the white dwarfs, neutron stars, black holes etc. which are intensely gravitational structures.  In fact an amalgamation of black holes exists at the core of each galaxy. Research in the last few decades is revealing the possibility of other universes.

What happened before ? The universe existed before we were born, before the earth was born, before the solar system was born, before the stars were born, before our Milky was born etc. Once we rewind this history we come to a point in time and space called the big bang which heralded the birth or our universe. A supergiant explosion from such a humble beginning and rapid expansion called “inflation” led to the universe as we know today. The expansion still continues, thanks to the dark energy (aka vacuum energy) about which we know very little. This expansion pales in comparison with the initial inflation which expanded the space twenty orders of magnitude (10 followed by 20 zeroes) in a very tiny fraction of a second. The initial inflation caused the space to expand faster than the speed of light. One of the rare instances when Einstein’s speed limit was broken.  Given below is the picture from Wikipedia  depicting the growth of our universe since the big bang. The vertical rise to the left is the period of rapid inflation. 

Sounds similar to the conception, birth and growth of a baby. If the conception is like a big bang, when a sperm and an egg come together to form one fused cell. Rapid division and multiplication of the number of cells leads to an embryo and to a baby and so on. Growth continues well into adulthood. Eventually the old adult dies and the body decays. Is our universe an adult now or an old person ? Will the analogy to the growth of a baby stop here ? We dont know. Astronomers predict expansion for a long time to come. But let us see what future discoveries come up with.   

What happened before the big bang ? Big bang is considered as a singularity where the clock is supposed to have started. Did something exist before the clock started ? This question is being increasingly linked to the one before. The possibilities of a multiverse (multiple universes). First posited by Hugh Everett under the guidance of John Wheeler and opposed by Neils Bohr, the idea tapered down with Everett leaving academia under intense criticism. The theory has been resurrected since then and is being viewed in the context of the recent string theory in an attempt to marry the macro gravitational force with the micro quantum mechanics.     

String theory decomposes all the known elementary particles like quarks, electrons etc. into more fundamental structures called vibrating strings. These are so minute that no technology exists to view them. Vibration at different frequencies is supposed to lead to different kinds of elementary particles. There seems to be an elementary within an elementary! As a side effect, string theory also predicts the existence of ten spatial dimensions and one time dimension. But we only see and perceive three spatial and one time dimensions. Remaining dimensions are supposed to be curled up at the micro level or not perceivable by us.  

All these concepts are being married together to form a theory of everything. There is supposed to be a higher dimension called a bulk in which multiple universes float as bubbles. The movie “Interstellar” tries to depict this concept well. Quantum mechanics specifies that particles at the micro level are also waves and are defined by the Schrodinger equation. Events are statistical and presence or absence of particles at different points in time are probabilistic and subject to Heiesenberg’s uncertainty principle. 

The bulk is considered as a string landscape where each miniature bubble on a canvas is a potential universe. When a bubble has intense energy and a lot of quantum variations within, it is a good candidate for a big bang and a universe to emerge. Probability of the existence of multiple universes is not trivial. In the book “Before the big bang” by Laura Mersini-Hughton, it succinctly states that the Wheeler-DeWitt equation in quantum cosmology is the equivalent of Schrodinger equation in regular quantum mechanics. The book also talks about looking for the effects of multiple universes on our universe. Obviously, we cannot travel beyond our universe. Nothing can travel between universes – no light, no radiation etc. Only gravity can traverse between multiple universes. 

Gravity is the only means by which we possibly can detect the effects of our universes. Such gravitational interactions are very feeble, and often masked by stronger interactions like death of stars and galaxies, merger of black holes etc. The cosmic background radiation which proved the theory of the big bang, has been studied by successively sensitive satellites launched into space. The latest being the Planck satellite. A picture captured by Planck shown below courtesy Physics World, shows a circled “cold spot” to the bottom right, which is supposed to indicate the impact of surrounding multiple universes. The spot cannot be explained by anything related to the big bang or an to any of the the local events.      

The conclusions are not a done deal. And the journey continues…