The Great Cosmic Roller-Coaster Ride
Could cosmic inflation be a sign that our universe is embedded in a far vaster realm?
But one of the emerging themes of 21st-century cosmology is that the known universe, the sum of all we can see, may just be a tiny region in the full extent of space.
Various types of parallel universes that make up a grand “multiverse” often arise as side effects of cosmological theories. We have little hope of ever directly observing those other universes, though, because they are either too far away or somehow detached from our own universe. Some parallel universes, however, could be separate from but still able to interact with ours, in which case we could detect their direct effects.
The possibility of these worlds came to cosmologists’ attention by way of string theory, the leading candidate for the foundational laws of nature.
Although the eponymous strings of string theory are extremely small, the principles governing their properties also predict new kinds of larger membranelike objects—“branes,” for short. In particular, our universe may be a three-dimensional brane in its own right, living inside a nine-dimensional space.
The reshaping of higher-dimensional space and collisions between different universes may have led to some of the features that astronomers observe today.
String theory has received some unfavorable press of late. The criticisms are varied and beyond the scope of this article, but the most pertinent is that it has yet to be tested experimentally. That is a legitimate worry. It is less a criticism of string theory, though, than a restatement of the general difficulty of testing theories about extremely small scales. All proposed foundational laws encounter the same problem, including other proposals such as loop quantum gravity.
String theorists continue to seek ways to test their theory. One approach with promise is to study how it might explain mysterious aspects of our universe, foremost among which is the way the pace of cosmic expansion has changed over time.
Kemo D. (a.k.a. no.7) www.beyondgenes.com