Once Before Time - Martin Bojowald [152]
In quantum gravity, impressive possibilities of new knowledge can be expected for the foreseeable future. Theoretical progress continues unceasingly, and some surprising gains have resulted from the research of recent years, bringing hope for a fundamental mathematical analysis that will reliably reveal new phenomena. Cosmology will be made ever more precise by a series of satellite and other observations arising from the continuous development of new technologies. Ever more precisely will we be able to look back to ever earlier times, and eventually we should be able to make physical measurements of quantum gravity effects.
How far back in time can we be guided in this way? Will we ever, with a precision that meets scientific standards, see the shape of the universe before the big bang? The answer to such questions remains open. We have a multitude of indications and mathematical models for what might have happened. A diverse set of results within quantum gravity has revealed different phenomena important for revealing what happened at the big bang. But for a reliable extrapolation, parameters would be required with a precision far out of the reach of current measurement accuracies. This does not, however, mean that it is impossible to answer questions about the complete prehistory of the universe. Cosmology as well as theoretical investigations are currently moving forward and will result in unforeseen insights. Among them might well be experimentally confirmed knowledge of the universe before the big bang.
NOTES
INTRODUCTION
1. Rudolf Carnap, An Introduction to the Philosophy of Science (New York: Dover Publications, 1995), 207.
1. GRAVITATION
1. Other striking examples are provided by the main theories covered in this book: general relativity and quantum mechanics. These theories started perhaps more controversially than Newton’s, for they came at a much later stage and were tasked with explaining more subtle phenomena. In these as in other cases, it is almost shocking to realize that purposeful mathematical manipulations—pure thought—can so closely correspond with nature. So often, observations have been preempted by bold predictions, for instance of elementary particles envisioned before they were seen, following purely mathematical symmetries. Then again, theoretical visions so often turned out to be incorrect; but by being right much more than once, theoretical physics has abundantly shown that it did not just have a lucky strike. Its attempted predictions are indispensable in guiding observations and leading physics to new frontiers. Being granted confirmation of one’s own ideas, even if they are rather minor, is every theorist’s dream, though only few can have success. It is as if one thinks one is playing a game of chess, only to find oneself leading an actual battle.
2. The transformability of space and time does have consequences for daily life, for without it the amount of natural radioactivity on Earth’s surface would be much less: muons, elementary particles produced in the upper atmosphere by cosmic rays bombarding Earth, would otherwise decay high up in the atmosphere without being able to contribute to cosmic radiation on the ground.
3. The origin especially of the highly energetic contribution is not completely understood, but it appears to come from active galactic nuclei outside the Milky Way.
4. Such arguments may also be a telltale sign of the hidden agenda to conveniently avoid learning complicated theories, which only rarely find their way into standard university courses.
5. For this discovery, Hulse and Taylor were awarded the Nobel Prize in Physics in 1993.
6. “Heads” here literally refers to the body parts. If the minds of people in Europe and America also sometimes seem to point in different directions, that observation has an unrelated origin.
7. Accordingly, clocks slow down when brought to lower altitudes. This holds true only as long as the clock remains outside Earth’s main