15 September 2016

This is just mind boggling, if your mind is boggled by such things.

From Wikipedia, on a subject dear to me, namely the question What is the size of the observable universe in proportion to the size of the entire universe that emerged in the Big Bang? 

[Per]"Alan Guth, if it is assumed that [cosmic] inflation began about 10−37 seconds after the Big Bang, then with the plausible assumption that the size of the Universe before the inflation occurred was approximately equal to the speed of light times its age, that would suggest that at present the entire universe's size is at least 3x1023 times larger than the size of the observable universe.[18] There are also lower estimates claiming that the entire universe is in excess of 250 times larger than the observable universe[19] and also higher estimates implying that the universe is at least 101010122 times larger than the observable universe[20]


14 September 2016

Some musings on the philosophy of science

I got into a lively discussion ​not long ago with one of my interlocutors about whether future scientists will laugh at the current state of scientific understanding about the basic nature of how the world works. You know, stuff like "on a basic level, matter is composed primarily of atoms, which are in turn composed primarily of neutrons, protons and electrons, with more subtle internal structure responsible for quantum effects on a micro level." And "the electromagnetic force is what prevents your hand from flowing into the mostly empty space of the table when you pound on it." These kinds of well-established assertions are not hubris, and they are not going to be in any meaningful sense proven "wrong" in the future. Science does progress, and there are new discoveries being made all the time, but they do not affect the "truth" of correctly adduced past propositions. Here is where there is a difference. Some past propositions, such as Ptolemy's Earth-centered cosmology, or the phlogiston theory, or the luminiferous aether, were not "correctly adduced." They were just wrong. But mechanics, fluid dynamics, thermodynamics, the general outlines of General Relativity and Quantum Mechanics, etc. are shown correct by so many Bayesian "credence corrections" that there is no reasonable doubt that any of them will ever be shown to be basically incorrect. And this is not hubris. Here are some interesting observations from Sean Carroll in his lovely new book, The Big Picture:


"[There] is a fundamental difference between the kind of knowledge given to us by mathematics/logic/pure reason and the kind we get from science. The truths of math and logic would be true in any possible world; the things science teaches us are true about our world, but could have been false in another one. Most of the interesting things it is possible to know are not things we could ever hope to 'prove,' in the strong sense. ¶ Even when we do believe a theory beyond a reasonable doubt, we will understand that it's an approximation, likely (or certain) to break down somewhere. There could very well be some new hidden field that we haven't yet detected that acts to slightly alter the true behavior of gravity from what Einstein predicted [for example]. And there is certainly something going on when we get down to the quantum scales; nobody believes that general relativity is really the final word on gravity. But none of these changes the essential truth that GR is 'right' in a certain well-defined regime. When we do hit upon an even better understanding, the current one will be understood as a limiting case of the more comprehensive picture."


I had tried to make this point, and even that the same is true of Newton's gravity theory vis-a-vis Einstein's. Newton is a limiting case of Einstein. Any future quantum theory of gravity will have Einstein's as a limiting case. (Indeed, it's already established that any quantum corrections to Einstein will be unobservably small on a macro level).

But there's another point that ties into this that is perhaps even more important. Many people seem to think that because science is adductive, empirical, and subject to falsification at any time (based as it is on Bayesian reasoning, which Carroll explains beautifully and that alone is worth the price of the book)... that it is somehow just another form of faith, based on unprovable belief. Religious people will often say that belief in evolution is just a form of faith in a secular religion. But it isn't, and that kind of reasoning is completely fallacious. Again, Carroll:


"You will sometimes hear the claim that even science is based on a kind of 'faith,' for example, in the reliability of our experimental data or in the existence of unbreakable physical laws. That is wrong. As a part of the practice of science, we certainly make assumptions-- our sense data is giving us roughly reliable information of the world, simple explanations are preferable to complex ones, we are not brains in vats, and so forth. But we don't have 'faith' in those assumptions; they are the components of our 'planets of belief,' [a term he coined and explains elsewhere], but they are always subject to revision and improvement, and even, if necessary, outright rejection. By its nature, science needs to be completely open to the actual operation of the world, and that means that we stand ready to discard any idea that is no longer useful, no matter how cherished and central it may once have seemed." (Some emphasis added).


Few religionists will acknowledge the same rules of reason and evidence for their beliefs. But the main point is that science is not committed to any particular view of the world; other than the view that any proposition must withstand challenges from actual evidence, at any time. Of course many scientists, being human beings, are subject to various biases and "pet theories." But science itself is, by its nature, self-correcting.