Is there any particular hypothesis of a Blane that can be falsified by experiment and observation? (Is “theory” a particularly appropriate term here?)
Spiritus
I think your response of “unanswerable” is perfectly accurate.
Yes. Brane theories (with the word “theory” being used in the non-scientific sense) make certain predictions about phenomenon observable only at extremely high energy densities.
There are a variety of popular books and websites available to laypeople about branes. I suggest you take a look at them.
What predictions do they make? Are there other hypotheses that make the same predictions? Why is the term “theory” used in a “non-scientific sense” about a scientific matter?
A wide variety, mainly about the nature of space-time. Predictions include certain forms of action-at-a-distance and various manifestations of fundamental mathematics, otherwise known as “physics”.
Because they’re more than hypotheses, essentially. They don’t have the weight of evidence that confirms true theories, such as the Atomic Theory or the Theory of Evolution, but they’re not true hypotheses either.
Theoretical physics is dedicated to generating mathematically consistent systems whose behavior can be used to describe (and ideally, predict) the physical universe. Sadly, history has seen to it that the name of the hypothetical sciences carries the word “theory” in it. It’s just one of those funny things about life.
Set theory, for one example.
The basic problem with what you’re saying is that everything does not have a beginning!! time has no beginning!! We only measure it against something.
Precisely. “Theory” in the mathematical sense refers to a consistent system. “Theory” in the sciences can be used in a technical sense: a set of principles that attempts to explain observations and can make meaningful predictions about the world while withstanding attempts at falsification and competition from other hypotheses. It can also be used in the vernacular sense, which is somewhat similar to the mathematical.
How so ? The other coordinates of spacetime all have a beginning, back at t[sub]0[/sub] when the big bang was nothing but a dimensionless point. There was no X, no Y, and no Z. What makes you so certain that the range over which time holds is larger than any of the other axes ?
How so ? The other coordinates of spacetime all have a beginning, back at t[sub]0[/sub] when the big bang was nothing but a dimensionless point. There was no X, no Y, and no Z. What makes you so certain that the range over which time holds is larger than any of the other axes ?
Has it been show that there is a t=0?
I haven’t studied it much, but I imagine that time can be defined in fractions of a second after zero. Is there a limit to how small of a fraction of a second can exist?
-k
I believ the point that the “time has no beginning” folks are making is that time is the word “beginning” itself implies a flow of time (i.e. a change of state which is possible only in time). Thus, it makes no real sense, semantically, to speak of time itself having a beginning. There was no “moment” before time began, since “moment” already implies time.
For myself, I prefer to simply reference anything before t[sub]0[/sub] as out-of-scope for any discussions grounded in our physical reality. t[sub]0[/sub] represents a terminus point beyond which we can gather no information. Whether that terminus separates us from “something” or “nothing” or “everything” is a matter that will always be necessarily speculative.
According to quantum theory, yes.
wow, that one took a while to post.
The big bang is not considered to be simply an explosive outpouring of matter into a pre-existing geometry, but rather involved the creation of spacetime itself.
I’ll get beat up by a mob of angry mathematicians and physicists if I say much more than that. However, Stephen Hawking has a nice little pdf (~25K) lecture titled The Beginning of Time, which covers things nicely:
Well, the link was pdf when I opened it, but now it comes up as html :smack:
It’s an interesting read, regardless.
But doesn’t that still occur as an event in time? My point was, at t=0, nothing could “come from” anything, because time is not defined, right? Forgive my piggybacking Squink’s Hawking quote:
“the state of the universe, after the Big Bang, will not depend on anything that may have happened before, because the deterministic laws that govern the universe will break down in the Big Bang.”
Wheelchair Guy says it better than I can. If the universe does have a cause, it can’t be measured in terms of our time.
Blowero
Now you and I are on the same page, I think — or at least close. Your answer is more along the lines of that from Spiritus and me, namely that there is no answer. Dodgy business about theories that aren’t really theories doesn’t contribute anything substantive that I can discern. But just to be clear — and to reiterate a point I already made — I’m not saying that the universe must have had a cause. I’m saying that it must have had a mechanism. Nothingness implies the lack of any mechanism. That’s the problem.
There’s a difference between the lack of an answer and the lack of a humanly comprehensible answer. There will always be unanswerable questions, but that does not imply that there is no truth.
It may have had a “cause” (or mechanism, or whatever you want to call it), or it may be eternal. We don’t have any way to know that right now, since any reality that may or may not exist outside of the universe is not measurable by any standards within the universe.
To be honest, I don’t understand what you’re talking about here. My understanding is that nothing “before” (for lack of a better word) t=0 can have any effect on how events play out after t=0. So the question of whether our universe was “spawned” from another universe, or simply exists eternally is irrelevant to the current state of entropy, is it not?
Well said. But you should add that it should never be taken as carte blanche to substitute overt speculation (or wishful thinking) for unknowns and try to pass it off as fact.
Here’s my admittedly layman’s understanding of it (and again I offer the standard disclaimer to correct me if I’m wrong): t=0 is a mathematical limit where density is infinite at t=0. So yes, time is defined at increasingly smaller and smaller fractions of a second after t=0. We can’t really talk about what occurs at t=0, because the rules by which we describe things don’t exist at t=0. It’s really a mathematical construct that we lack the ability to understand intuitively.