String theory and the origins of the universe
String theory says that in the beginning, the universe was not a zero sized point particle but a small Planck sized nugget about the size of a typical string. The important thing to realise here is that it did have a size, small though it was. It did not start from nothing. The Standard Model describes the beginning of the universe from about a hundredth of a second ATB to the present, 13.7 billion years later, and says that from the Planck time to about a hundredth of a second ATB, the universe expanded exponentially.
String theory goes on to say that at first, the three non-gravitational forces (the electromagnetic and the strong and weak nuclear forces) comprised one “grand unified” or “super” force, but a split second thereafter, they crystallised into separate forces. What actually happened to the gravitational force and when it separated from the other fused forces is not clear to me from Greene’s account (2000), but it has been suggested elsewhere that the gravitational force separated from the other forces at the Plank time 1 x 10-43 seconds after the big bang[1],[2].
It has been postulated by some quantum theorists that in a pre-big bang scenario, the universe began in a vastly different state than it does in the conventional big bang framework; and that, rather than being enormously hot and tightly curled into a tiny special speck, the universe started out as cold and essentially infinite in spatial extent. The equations of string theory indicate that an instability then kicked in, driving every point in the universe to rush rapidly away from every other. This caused space to become increasingly curved, resulting in a dramatic increase in temperature and energy density. After some time, a millimetre sized three dimensional region within this vast expanse could look just like the super-hot and dense patch emerging from the traditional inflationary expansion. Then, through the standard expansion of ordinary big bang cosmology, this patch accounts for the whole of the universe with which we are familiar[3].
[1] Ben Best, The Standard Model of Particle Physics http://www.benbest.com/science/standard.html p 8; “The fundamental forces of nature”, http://csep10.phys.utk.edu/astr162/lect/cosmology/forces.html.
[2] A reminder: figures like those reproduced here are known as exponential notation, a form of mathematical shorthand. Thus 1028 is a 1 with 28 zeros after it. 1 x 10-43 is a very small fraction: a 1 divided by a 10 with 43 zeros after it. This is the standard powers-of-ten notation. A power-of-ten is also known as an order of magnitude. To get a feel for this, see the You Tube video https://www.youtube.com/watch?v=0fKBhvDjuy0 Also, the illustrated Scientific American text by Caleb Scharf, The Zoomable Universe (2017); and David Christian in Maps of Time, University of California Press, Berkeley (2011), 36.
[3] Greene (2000), 362.
String theory goes on to say that at first, the three non-gravitational forces (the electromagnetic and the strong and weak nuclear forces) comprised one “grand unified” or “super” force, but a split second thereafter, they crystallised into separate forces. What actually happened to the gravitational force and when it separated from the other fused forces is not clear to me from Greene’s account (2000), but it has been suggested elsewhere that the gravitational force separated from the other forces at the Plank time 1 x 10-43 seconds after the big bang[1],[2].
It has been postulated by some quantum theorists that in a pre-big bang scenario, the universe began in a vastly different state than it does in the conventional big bang framework; and that, rather than being enormously hot and tightly curled into a tiny special speck, the universe started out as cold and essentially infinite in spatial extent. The equations of string theory indicate that an instability then kicked in, driving every point in the universe to rush rapidly away from every other. This caused space to become increasingly curved, resulting in a dramatic increase in temperature and energy density. After some time, a millimetre sized three dimensional region within this vast expanse could look just like the super-hot and dense patch emerging from the traditional inflationary expansion. Then, through the standard expansion of ordinary big bang cosmology, this patch accounts for the whole of the universe with which we are familiar[3].
[1] Ben Best, The Standard Model of Particle Physics http://www.benbest.com/science/standard.html p 8; “The fundamental forces of nature”, http://csep10.phys.utk.edu/astr162/lect/cosmology/forces.html.
[2] A reminder: figures like those reproduced here are known as exponential notation, a form of mathematical shorthand. Thus 1028 is a 1 with 28 zeros after it. 1 x 10-43 is a very small fraction: a 1 divided by a 10 with 43 zeros after it. This is the standard powers-of-ten notation. A power-of-ten is also known as an order of magnitude. To get a feel for this, see the You Tube video https://www.youtube.com/watch?v=0fKBhvDjuy0 Also, the illustrated Scientific American text by Caleb Scharf, The Zoomable Universe (2017); and David Christian in Maps of Time, University of California Press, Berkeley (2011), 36.
[3] Greene (2000), 362.