Observations by the Hubble Space Telescope — like the Hubble Ultra Deep Field, which looks back to within a few hundred million years of the Big Bang — have helped to put cosmology on sound observational footing.
NASA, ESA, H. Teplitz and M. Rafelski/IPAC/Caltech, A. Koekemoer/STScI, R. Windhorst/Arizona State Univ., Z. Levay/STScI
Not that long ago, most serious scientists considered cosmology a branch of philosophy. But in recent decades, observations by the Hubble Space Telescope and probes of the microwave radiation left over from the Big Bang have put cosmology on a sound observational footing. Still, many important issues about the origin and evolution of the universe remained unresolved. So now some serious cosmologists are suggesting that it might help to develop a philosophy of cosmology.
Physicist Sean Carroll, for instance, recently blogged about a conference he attended on just that subject: the philosophy of cosmology. He commented that the field is not well formulated yet, and proposed that one way to build a sound foundation for the field would be to identify the key questions worthy of its attention. Carroll nominated 10 such questions.
As with most scientists’ Top 10 Questions lists, though, he didn’t bother to provide any of the answers. So as a service to cosmology, or philosophy, or blogology, I’ve decided to reveal those answers now, unconstrained by any implied warranty that my answers are actually correct. (When you think about it, similar non-warranties should apply to anybody’s answers.)
So remember, the questions are Carroll’s. The answers are mine.
1. In what sense, if any, is the universe fine-tuned?
Whatever the sense is, it is not very well fine-tuned, because the picture is still pretty fuzzy.
2. How is the arrow of time related to the special state of the early universe?
Ah, by assuming the state of the early universe was special, this question answers itself. It was special because it was “early” and therefore came “before” all the other states of the universe, which defines the arrow of time by making all those other states “after.” (OK, so I don’t really know the answer to this one.)
3. What is the proper role of the anthropic principle?
Now we’re getting somewhere. The role of the anthropic principle is to explain things that can’t be explained without it. Anthropic reasoning basically says that something is the way it is because otherwise people wouldn’t be around to wonder why it’s the way it is. Anthropic reasoning can explain the distance between the Earth and the sun, because if the distance were much more or less, people couldn’t survive here and ask such philosophical questions. Similarly, there are features of the universe that couldn’t be altered very much without making intelligent life impossible. Still, the tricky thing is that just because scientists don’t know how to explain something now, that doesn’t necessarily mean they won’t find some nonanthropic explanation in the future.
4. What part should unobservable realms play in cosmological models?
Whatever part they need to play to help explain observable realms. The whole notion that anything that can’t be observed is not scientific is a pernicious prejudice left over from failed positivistic philosophies. It’s baloney.
5. What is the quantum state of the universe, and how does it evolve?
A deep and difficult question, at the heart of understanding the nature of reality and existence. So the complete answer will require something like a three-installment set of blog posts. The short answer is that the quantum state is either ontic or epistemic, and it evolves however it wants to. But I won’t be able to explain that until I look up “ontic” and “epistemic.”
6. Are space and time emergent or fundamental?
Yes.
7. What is the role of infinity in cosmology?
For one thing, to make sure there’s no limit to the number of cosmologists. But this answer could go on and on and on and on and….
8. Can the universe have a beginning, or can it be eternal?
An eternal question. Aristotle said the universe had to be eternal, because it was impossible for something to emerge from nothing. But let’s face it — Aristotle’s grasp of quantum spacetime fluctuations was limited. Modern big bang cosmology initially suggested that there was an initial instant when time itself (and space, too) came into being. But nowadays there is a lot more speculation about a cosmos pre-existing the known universe, or about a universe that continually recycles itself. Whether or not there was a beginning, though, the best evidence now suggests that the universe will expand forever. So it would be a good idea to bet that the universe will be eternal to the future. (And even if the universe did come to an end, you wouldn’t have to pay up.)
9. How do physical laws and causality apply to the universe as a whole?
Kind of the same way constitutional law applies to the Supreme Court. Laws of nature aren’t prohibitions, after all — they’re descriptions of how nature works. It’s possible that the nature of physical law will have to be reinterpreted as cosmologists find out more about how the universe as a whole really behaves.
10. How do complex structures and order come into existence and evolve?
By the operation of forces, the flow of energy, and the processing of information. Not by blogging.
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