If there is a mixup here, it is a mixup of terminology. When people say Big Bang, they can mean t = 0 in the Big Bang chronology (the theoretical singularity in the classical relativistic model on which Big Bang theory is based), or they can mean the earliest period where the Big Bang theory is applicable, which comes a little bit after t = 0 (and which would be preceded by Inflation), or they can even mean the entire period from there till now and beyond (the Big Bang universe). The worry about time ending or becoming physically meaningless as it approaches t = 0 is not unfounded, for although we know little about that earliest period, there is reason to think that physical clocks that give time its meaning beyond a mathematical formalism may no longer work there.
The problem with putting initial conditions off limits is that virtually everything we observe in the universe is dependant on initial conditions. — Count Timothy von Icarus
Thus, if we come to see "Christ is King," "Zeus wuz here," "Led Zeppelin rules!," scrawled out in quasars and galaxies at the far end of the cosmos, this shouldn't raise an eyebrow? Because, provided the universe is deterministic, such an ordering would be fully determined by those inscrutable initial conditions. — Count Timothy von Icarus
When you think of the Big Bang, you just mean inflation, right? You're not adding a singularity to it, are you? — frank
The problem with putting initial conditions off limits is that virtually everything we observe in the universe is dependant on initial conditions. — Count Timothy von Icarus
That is, of the set of all physically possible things we could see, we shouldn't expect to see one universe more than the other. Thus, if we come to see "Christ is King," "Zeus wuz here," "Led Zeppelin rules!," scrawled out in quasars and galaxies at the far end of the cosmos, this shouldn't raise an eyebrow? Because, provided the universe is deterministic, such an ordering would be fully determined by those inscrutable initial conditions. — Count Timothy von Icarus
Seeing text written in English using galaxies wouldn't undercut the Copernican Principal? I mean, the universe would be writing in human language on the largest scales we can observe... at that point, if you keep the principal it has become dogma, something religious that can't be overturned by new observations. — Count Timothy von Icarus
Likewise, if we uncovered some sort of ancient Egyptian code in our DNA that said something like "we came from other stars to give you intelligence, send some light beams at these points when you read this," I would certainly start to take the History Channel loons more seriously, rather than shrug.
The likelihood of such a code is such that it would be solid evidence for ET conspiracies IMO. But if both potential causes of the message, random fluke and alien intervention, are both entirely dependant on initial conditions and their deterministic evolution, then why would we assign more likelihood to one versus the other? — Count Timothy von Icarus
Also, I don't see why observing seemingly unlikely phenomena requires positing any sort of creator or designer. Why can't we just assume some sort of hitherto unforseen mechanism that makes the seemingly unlikely, likely? E.g., people used to think the complexity of life required a creator, but then the mechanisms underpinning evolution were discovered. — Count Timothy von Icarus
From the 1920s up through the 1970s, scientists thought they had a satisfactory story for our cosmic origins [the Big Bang], and only a few questions remained unresolved. All of them, however, had something in common: they all asked some variety of the question, "why did the Universe begin with a specific set of properties, and not others?" — Ethan R. Siegel
In physics, we have two ways of dealing with questions like these. Because all of these questions are about initial conditions — i.e., why did our system (the Universe) begin with these specific conditions and not any others — we can take our pick of the following: — Ethan R. Siegel
Although it's not clear to everyone, the first option is the only one that's scientific (emphasis mine); the second option, often touted by those who philosophize about the landscape or the multiverse, is tantamount to giving up on science entirely.
The big idea that actually succeeded is known, today, as cosmic inflation. In 1979/80, Alan Guth proposed that an early phase of the Universe, where all the energy wasn't in particles or radiation but in the fabric of space itself instead, would lead to a special type of exponential expansion known as a de Sitter phase....
In fact, our entire observable Universe contains no signatures at all from almost all of its pre-hot-Big-Bang history; only the final 10-32 seconds (or so) of inflation even leave observably imprinted signatures on our Universe. We do not know where the inflationary state came from, however. It might arise from a pre-existing state that does have a singularity, it might have existed in its inflationary form forever, or the Universe itself might even be cyclical in nature.
There are a lot of people who mean "the initial singularity" when they say "the Big Bang," and to those people, I say it's long past due for you to get with the times. The hot Big Bang cannot be extrapolated back to a singularity, but only to the end of an inflationary state that preceded it. We cannot state with any confidence, because there are no signatures of it even in principle, what preceded the very end-stages of inflation. Was there a singularity? Maybe, but even if so, it doesn't have anything to do with the Big Bang.
— Ethan R. Siegel
In physics, we have two ways of dealing with questions like these. Because all of these questions are about initial conditions — i.e., why did our system (the Universe) begin with these specific conditions and not any others — we can take our pick of the following:
We can attempt to concoct a theoretical mechanism that transforms arbitrary initial conditions into the ones we observe, including that reproduces all the successes of the hot Big Bang, and then tease out new predictions that will allow us to test the new theory against the old theory of the plain old Big Bang without any alterations.
Or, we can simply assert that the initial conditions are what they are and not only is there no explanation for those values/parameters, but we don't need one.
Although it's not clear to everyone, the first option is the only one that's scientific (emphasis mine); the second option, often touted by those who philosophize about the landscape or the multiverse, is tantamount to giving up on science entirely. — Ethan R. Siegel
The point about the aliens is just this: if everything observable evolves deterministically from initial conditions, and initial conditions are unanalyzable, then the likelihood of any observation has no objective value. You could still ground probability in subjective terms, which is perhaps justified anyhow for other reasons, but it seems like a bad way to arrive at such a conclusion. The thing that has always kept me from embracing a fully subjective approach to probability is: (1) the existence of abstract propensities that seem isomorphic to physical systems and; (2) that fully subjective probability makes information theory arguably incoherent, which is not great since it is a single theory that is able to unify physics, biology, economics, etc. and provides a reasonable quantitative explanation for how we comes to know about the external world via sensory organs (leaving aside the Hard Problem there). — Count Timothy von Icarus
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