"Alice laughed: "There's no use trying," she said; "one can't believe impossible things.""I daresay you haven't had much practice," said the Queen. "When I was younger, I always did it for half an hour a day. Why, sometimes I've believed as many as six impossible things before breakfast." ——Alice in Wonderland.
Judging from The Universe Next Door: The Making of Tomorrow's Science by Marcus Chown, a great many physicists are accustomed to believing impossible things not just before breakfast, but all day and night. The strange thing is, some of these impossible things become not just possible, but the products of our technological society. Consider ultrasensitive magnetometers called SQUIDs, for Superconducting QUantum Interference Device. They depend on the ability of an electron to pass through two apertures simultaneously and interfere with itself. A tiny magnetic field biases how many electrons actually self-interfere and how many pass through just one aperture and thus fail to interfere, producing a signal boost.
Others remain stubbornly impossible. It is estimated that about one-third of the brain energy of cosmologists has been consumed with string theory for the past few decades, and to date, every "result" must be firmly labeled speculative. So far, not one testable hypothesis has emerged from the field.
Still others seem fantastic, but plausible upon reconsideration. The last chapter of the book, titled "Alien Garbage", discusses the proposal by Alexey Arkhipov that there could be a few thousand artifacts on earth that are "space junk" from alien civilizations. Consider: In 54 years of the "space age", we have produced tens of thousands of items in orbit, most of them pieces of satellites or debris from their launching, plus at least two large space probes deliberately sent beyond the confines of the solar system. Consider a century hence, at which time we might have begun to make use of the asteroid belt. Over time, we might convert some fraction of a percent of its mass into artifacts of all sizes. Some of these will inevitably be lost to interstellar space. Using a calculation similar to the Drake Equation used for SETI predictions, Dr. Arkhipov estimated that about 4,000 pieces of alien space junk could have found their way to the Earth's surface in the past few billion years, assuming aliens have been around that long. This is considered a reasonable estimate, and, remarkably, you'd have to reduce the estimate by a factor of a few thousand in an "unreasonably pessimistic" direction, to claim that there are one or fewer alien artifacts that could have impacted Earth.
In between, the author has gathered quite an entertaining variety of speculations about the nature of the universe (or universes), of reality itself, and of life. Can it be that every time a choice must be made, the universe splits into a sufficient number such that every possible choice actually occurs, somewhere? Think of how many decisions you make daily, and multiply by seven billion; or better, multiply by the half trillion or so vertebrate brains on the planet; or even better, multiply by every option a quantum is faced with each and every nanosecond, and split universes accordingly. Now there is an impossible thing to consume with your breakfast! And I contend that this speculation is, indeed, impossible in the very most literal sense of the word. This is a consequence of the Copenhagen Interpretation of quantum theory, which states that a quantum event does not actually eventuate until an observation is made that "forces" the previously "mixed state" of the quantum or quanta involved to "choose" where to be and how fast to be moving. Such a "many-worlds" model is proposed as a way that all possible "choices" can be made simultaneously. A vastly simpler explanation is certain to arise.
At the other end of the scale, there is the existence of life itself. One life-bearing planet is proof that it is possible. But how likely? It is either very easy or very hard. Experiments in the lab have eliminated the easiest end of "very easy", but if you could carry on such experiments for a trifling million years or so, producing life might be found to be inevitable. Don't hold your breath. The blackness of the comets so far visited indicates that they are also likely places for living cells to arise (again, given a million years or so when they are still warm from creation and from medium-duration isotopes such as Al26).
Then there is the fifth dimension. I understand the special and general theories of relativity well enough to be comfortable that spacetime is a four-dimensional continuum, with the proviso that motion along the t dimension is not manipulable in any way other than by changing either velocity or gravitational potential. Can t be reversed, or can there be portions of space in which t is traversed in the opposite direction? Further, can there be yet another dimension of space, or multiple time dimensions? There is lots of speculation, but no data. By the way, the author does not denote terms for the directions along a fourth space direction. I suppose he is unaware that theorists use the terms ana and kata to correspond to "toward" and "away" along this extra dimension/direction.
While I enjoy reading about such speculations, I am equally amused that they get more than passing notice. It really is easier to believe in God than in many of these speculative cosmologies. Amazingly, there is a whole chapter titled "Was the Universe Created by Angels?", which re-introduces creationism, but relegates it so "superior" beings, who are less than "supreme". This just puts off the question by a step; how did the specially-tuned Universe in which these "superior" beings arose get created? Reminds me of the old Hindu who was asked "What is the Earth?" He stated, "The rounded back of a huge turtle." Asked what holds up the turtle, he said, "Four elephants." Asked if the elephants are standing on anything, he replied, "A larger turtle." OK, but what was the turtle on? Exasperated, he replied, "From there, it is turtles all the way down," and he walked away to forestall any further questions.
Any question of origins inevitably results in, if we are honest, "I don't know," and if we are more honest, "Probably, we can never know." So far as I know, Fred Hoyle has never reneged from his belief in continuous creation. He has his own explanations for various phenomena offered as "proof" of the "big bang." At least, his cosmology cannot be challenged by the question, "What was there before the beginning?" since it is without beginning. And perhaps that is the best place from which to think: Do not try to imagine a beginning, or a "before" state. Science firstly seeks to answer "What is, and what has happened?", then, "How do things happen?". To ask "Why" is not scientific, but theological, and as S.J. Gould suggested, is a different Magisterium, into which science simply cannot probe.
That won't stop scientists from speculating, of course. Nor should it.
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