Fact From Latin factum (“a deed, act, exploit; in Medieval Latin also state, condition, circumstance”), neuter of factus (“done or made”), perfect passive participle of faciō (“do, make”). The word fact can refer to verified information about past or present circumstances or events which are presented as objective reality. In science, it means a provable concept. As for explaining it further, this is deep in physics territory, so I can hardly do it with a couple of posts. I did post the video "A universe from nothing" by Lawrence Kraus in this very thread which is a good primer on this. It's a relatively easy to understand lecture on the basics of this, namely that the total sum of all energy in the universe is zero and how we got to know about it. This lecture by Sean Carroll does go a little more into detail as to how the physics behind a universe from nothing look like: http://video.google.com/videoplay?docid=-5667803493810086553# Both videos are about an hour long, but as I said, this stuff is complicated and fills books, so I guess that this time is the bare minimum you have to invest if you want to begin to grasp these ideas.
so does this guy... [ame="http://www.youtube.com/watch?v=S19d_bKbTtM"]YouTube - Saturday Night Live: Stuart Smalley[/ame]
I'm not trying to argue over semantics, but since words do convey ideas I just want to state that I believe there is a slight misuse of the term "fact" here. As I'm sure you know, science is not some static pool of collected "facts," it is a dynamic linkage of concepts and conceptual schemes based on observation and experiments--and these change as new evidences are discovered through new observations and experiments. As James B. Conant would suggest, in science it's better to use the term "conceptual scheme" rather than "fact." Additionally, if we were to talk about "provable concepts," I think we are no longer talking within the domain of science. As John Lennox puts it, "Now of course we do not speak of proof--you only get proof in the strict sense in my own field of mathematics. But in every other field including science we can't speak of proof, we can speak of evidence of pointers of being convinced beyond reasonable doubt." There are no scientific theories about why there is a universe rather than no universe that are empirically falsifiable, thus they cannot be scientifically tested and we are now bordering on metaphysics at this point. Instead, what remains are various theories, and these various theories are neither established "facts" nor even consensus. So what we are left with, then, are competing theories.
Well, first of all I agree of course. There's no absolute proof in science, only a practical one. However, here's what I said originally: I distinctly didn't say that "it's a fact that the universe started by purely natural means." Yes, so far we "only" have a couple of competing theories about the beginning universe, all being consistent with the laws of nature as we understand them today (which is mightily impressive if you ask me). But the mere fact that there are these theories out there (and it is a fact) means that we now know that god is not necessary to explain the world.
I listened to a portion of Sean Carroll's video, and one thing I was struck by was his statements about "before the Big Bang". Wait a minute. Now wait another minute...
that may be true, but (assuming there was a Big Bang) what anything was like before is a crapshoot. i don't care how much an expert in cosmology someone is, you can only speculate about the "before", and there are no hypotheses that can be tested, let alone falsified. the theoretical construct that you can reverse time to make determinations about how phenomena operated is interesting but we don't actually know whether the quantum mechanical models are more accurate than the general relativity models. Carroll says that his observations sound a bit crazy, and he's correct. until he can say more than "we don't know" what might have been before the Big Bang, i don't see any reason to abandon the idea that there is a time boundary involved. as he says, "there's no good reason" to assert that there isn't a time boundary. there may not be one, but who's to say one way or another.
Actually, if you watched it in full, you knew that this isn't true. Right now the theory can't be tested, but that's not a matter of principle, because if there is a "before", it has left traces in the "now". I don't even know what you're talking about. What I do know is that quantum mechanics produces the best, most accurate predictions in all of science. It is a matter of defining time. Time as we know it is a relationship between states. The state before the big bang would be different as there wouldn't be any distinguishable macro-states (EDIT: At least not in the model presented by Steve Carroll), therefore no time in the classical sense. There would however be distinguishable micro states.
Be grateful that we have the capacity to turn grape juice into wine. It does make our world a better place, doesn't it?
So I actually got Stephen Hawking's book. Since I drive a lot for long distances, I decided to get the audiobook, which might not have been the best idea, since at times, it would probably better to actually read a paragraph yourself or to look at some related diagram (which I'm sure there are in the book), especially since English is no my native tongue. But for the most part, I didn't have any problems understanding it. The book is in fact written for the average layman who has an interest in modern physics but doesn't know much about it. It's generally very compressed and Hawking only focuses on the important stuff. It's therefore no surprise that Hawking only gives us a very brief primer on the history of physics and the various discoveries made. Which personally I found very good, because I know all this stuff already from all the other books I've read and I didn't need to hear it again, while someone who doesn't already know these things probably isn't interested in details anyway, so the history presented in the book should be enough. Hawking generally doesn't go into detail very much, so it's actually rather easy to follow...until you start to wonder about the details that get never mentioned. The book is mostly about quantum mechanics and what it implies. So given the fact that this is a very tough subject to present, Hawking really does a tremendous job there (and yes he does talk about the double slit experiment, but no he doesn't talk about Schrödinger's cat). At the basis of it all is however a concept Hawking calls "Model-Dependent Realism" (MDR). This is basically a methodology to describe reality, a world view if you will (although that description might go a little too far). The basic tenet it that there is no one true way to describe reality, but that it depends upon your point of view. Very different models of reality can be true simultaneously, as long as they produce correct results. It's hard to sum up in a couple of sentences and you probably need to read the book in order to fully grasp it, but you probably get the idea. MDR seems intuitive on some level, but counter intuitive on others. I certainly have never thought about the world like that before but it's very intriguing and I have to say that I'm pretty much sold on the concept. From there, Hawking describes the latest advances in theoretical physics as well as cosmology. Apparently, Hawking endorses the Many Worlds Interpretation (MWI) of Quantum Mechanics (although he calls it Many Histories Interpretation if I recall it correctly...it amounts to the same thing though) which he justifies by his concept of Model-Dependent Realism: The MWI just works perfectly, therefore it's true. And while not explicitly endorsing M-Theory, he's definitely very hopeful about it. At the beginning, he says something along the lines of "M-Theory provides the foundation of many conclusions in this book" although I haven't really understood how he ties this all together. Towards the end, he seems to just throw out a couple of (very interesting) concepts about the nature of the universe, but I didn't see any connection to M-Theory...but maybe that would have gone too much into detail. For me personally there wasn't all that much new stuff in there. As I said, Model-Dependent Realism was new to me (in a sense) and Hawking did a good job explaining it. At times, would have liked him to go into more detail though. While I generally think that for this type of book, it's better to keep the various topics as brief as possible, some things seemed to deserve a little more attention: 1) The Holographic Principle. I find the concept absolutely fascinating, but unfortunately I still haven't heard any physicist detailing out the actual implications of it and how it's connected to M-Theory. 2) The Game of Life. Again a fascinating concept and again, I'd like to know about it's implications. What would it mean for our universe to be algorithmic in nature? And how does it tie into M-Theory? Maybe I have to read Stephen Wolfram's book "A New Kind of Science" which apparently deals with that subject. 3) The No-Boundary Proposal of time. This is probably the part of the book that was most interesting to me personally, so I was a bit disappointed that Hawking (like with the rest of the book) didn't go into much detail. I still have no idea what exactly this means nor how it's tied into the MWI or M-Theory or Relativity or anything really. Yet, the No-Boundary Proposal seems to be at the very core of Hawking's argument that our universe is self contained. But maybe it's impossible to put this into layman's terms. I've looked around a bit and it appears that there's some very complicated mathematics at the basis of this and no way to explain these mathematical functions in every day language. In conclusion, this book is great for everyone who wants to get a quick overview over the contemporary physics. It's relatively easy to understand and covers a lot of ground, although since it's based on the ideas of M-Theory, it omits competing theories like Loop Quantum Gravity (but that would have been beyond the scope of a book like that anyway). Hawking is in general pretty good at conveying difficult ideas in ways so that everybody can understand them. But that of course also means that you won't find much detail, let alone mathematical formulas. For someone like myself who has kept up with popular science in the media over the last years, there isn't all that much new information in the book though. It's still a nice read but don't expect any world view shattering information. Although as I pointed out above, the thing Hawking does explain in detail is MDR and that alone is very interesting, especially when he explains the consequences of MDR with an extreme example, namely with falling into a black hole. Personally, I think that Brian Greene's "The Fabric of the Cosmos: Space, Time, and the Texture of Reality". Is a better alternative. It has a similar scope, but goes through a lot more details. He describes the history of physics in depth, but in a way that makes it easy to follow and he also has an eye on what the things he explains mean, not just how they work. So he does put everything into a philosophical context. For people who would like to have even more details, I highly recommend Lisa Randall's "Warped Passages: Unraveling the Mysteries of the Universe's Hidden Dimensions" which is another book on M-Theory, and it also goes through the history of physics in depth, explaining the details of every major theory in a way that is still accessible to a lay person while at the same time offering a lot of in depth knowledge (There's for example a Math appendix with all the major formulas being explained, so if in any chapter you'd like to have some additional information, you can). The scope is not quite as large as in Hawking's or Greene's books, but if you really want to (begin to) understand Relativity or Quantum Mechanics, before diving into the speculative M-Theory, this is the better choice, since Hawking is more about what these things mean in the big picture than about how they work deep down, while Greene is somewhere in between. It is a tougher read though. While Randall also does a great job at writing analogies that make the physics easy to understand, the book kinda lacks a leitmotif that ties it together, so it can be dry at times.