The bottom line is that time travel is allowed by the laws of physics.
Extraordinary emblems of math’s ability to illuminate the dark corners of the cosmos, black holes have become the cynosures of modern physics.
According to string theory, if we could examine these particles with even greater precision – a precision many orders of magnitude beyond our present technological capacity – we would find that each is not pointlike, but instead consists of a tiny one-dimensional loop. Like an infinitely thin rubber band, each particle contains a vibrating, oscillating, dancing filament that physicists, lacking Gell-Mann’s literary flair, have named a string.
We revere the absolute but are bound to the transitory.
Just as important, the energy released by the inflaton field isn’t lost-instead, like a cooling vat of steam condensing into water droplets, the inflaton’s energy condenses into a uniform bath of particles that fill space. This two-step process-brief but rapid expansion, followed by energy conversion to particles-results in a huge, uniform spatial expanse that’s filled with the raw material of familiar structures like stars and galaxies.
General relativity then establishes that objects move toward regions where time elapses more slowly; in a sense, all objects “want” to age as slowly as possible. From an Einsteinian perspective, that explains why an object falls when you let go of it.
Stephen Hawking showed mathematically that the entropy of a black hole equals the number of Planck-sized cells that it takes to cover its event horizon. It’s as if each cell carries one bit, one basic unit of information.
And since, according to the big bang theory, the bang is what is supposed to have happened at the beginning, the big bang leaves out the bang. It tells us nothing about what banged, why it banged, how it banged, or, frankly, whether it ever really banged at all.
If you were to head out into the cosmos, traveling ever farther, would you find that space goes on indefinitely, or that it abruptly ends?
A stack of five off-the-shelf terabyte hard drives fits comfortably within a sphere of radius 50 centimeters, whose surface is covered by about 1070 Planck cells. The surface’s storage capacity is thus about 1070 bits, which is about a billion, trillion, trillion, trillion, trillion terabytes, and so enormously exceeds anything you can buy. No one in Silicon Valley cares much about these theoretical constraints.
The skyscraper is but a physical realization of the information contained in the architect’s design.
Much as Hamlet famously declares, “I could be bounded in a nutshell, and count myself a king of infinite space,” each of the bubble universes appears to have finite spatial extent when examined from the outside, but infinite spatial extent when examined from the inside. And that’s a marvelous realization.
The point being that everything emerges from the same collection of ingredients governed by the same physical principles. And those principles, as attested to by a few hundred years of observation, experimentation, and theorizing, will likely be expressed by a handful of symbols arranged in a small collection of mathematical equations. That is an elegant universe.
The ability to manipulate the environment thoughtfully provides the capacity to shift our vantage point, to hover above the timeline and contemplate what was and imagine what will be.
In the end, during our brief moment in the sun, we are tasked with the noble charge of finding our own meaning.
Sweet is sweet, bitter is bitter, hot is hot, cold is cold, color is color; but in truth there are only atoms and the void.
The beauty of physics, its raison d’etre, is that it offers insight into why things in the universe behave the way they do. The ability to predict behavior is a big part of the power of physics, but the heart of physics would be lost if it didn’t give us a deep understanding of the hidden reality underlying what we observe.
We are guided by laws that operate without concern for destination, and yet we constantly ask ourselves where we are headed. We are shaped by laws that seem not to require an underlying rationale, and yet we persistently seek meaning and purpose.
Fused in stars and ejected in supernova explosions, or jettisoned by stellar collisions and amalgamated in particle plumes, an assortment of atomic species float through space, where they swirl together and coalesce into large clouds of gas, which over yet more time clump anew into stars and planets, and ultimately into us. Such is the origin of the ingredients constituting anything and everything you have ever encountered.
Messy arrangements far outweigh orderly ones.
As our trek across time will make clear, life is likely transient, and all understanding that arose with its emergence will almost certainly dissolve with its conclusion. Nothing is permanent. Nothing is absolute. And so, in the search for value and purpose, the only insights of relevance, the only answers of significance, are those of our own making. In the end, during our brief moment in the sun, we are tasked with the noble charge of finding our own meaning.