Concept of time

[purintjp]

I was thinking about the concept of time recently and came to

the realization that for time to exist there must be some

movement through space benchmark for it to exist.

If you consider all the possibilites of the universe as it has

supposedly existed from the 'primordial atom' as postulated on a

recent showing of the 'Universe' series on TV to the current time

and probably way beyond, it seems clear that there has always been

movement through space and probably always will be.

It would seem that the only way a 'beginning' of time could exist

would be that the early universe consisted of nothing.

Do we know how long the 'primordial atom' existed prior to the

BBT ?

[swansont]

I was thinking about the concept of time recently and came to the realization that for time to exist there must be some movement through space benchmark for it to exist.

 

If an atom could be at rest (as it is in its own frame) it can quite happily oscillate between two states, which is one way of measuring time.

[purintjp]

I agree with that. As long as there is matter and energy in the universe isn't there always some movement at the quantum level or the cosmic level ?

I was thinking more in terms of the 'primordial atom'. Did it have it's own space or was it created out of nothing ? I guess what I'm trying to understand is what time = 0 really means.

[granpa]

do you conceive of time as being analog or digital?

 

if time is digital then the universe is a series of 'events'. each event being caused (or is it influenced) by the events immediately prior to it.

 

if all of existence is nothing but discrete events then a chain of events would have the same units whether the chain was in space or in time.

[Martin]

... I guess what I'm trying to understand is what time = 0 really means.

 

There are several modern models of what was going on around that time--models that are being studied and which have to be tested by comparing observation with what they predict about presentday data.

 

None of the modern models have time begin at t = 0. Time zero is just a good marker or reference point---the start of expansion (from a very dense state.) They all have something going on before t = 0, but there is disagreement as to what.

 

There is a classical model that does not quite get back as far as t = 0, it breaks down. So for that classic model (based on vintage-1915 relativity) the idea of "before t = 0" is simply meaningless. It loses track of things as it approaches time zero and breaks down.

 

So about all we can do is watch the experts in quantum cosmology (the people studying the very early moments of expansion) wrestle with the problem, which models are gaining adherents and interest among the research community, which models are losing appeal and having less research effort devoted to them.

 

Einstein Online (link in my signature) has an essay called "Tale of Two Big Bangs" which says it very clearly. "Most cosmologists would be very surprised" if it turned out that there actually was a singularity (where time stopped) at t = 0.

 

E-O is the pubic outreach website of one of the world's top research instutions and it's pretty up-to-date and well written, you might enjoy checking it out. It is likely less dumb-down than what is on History Channel. It is likely more clear and forthright about areas of uncertainty than commercial broadcast media can be.

[purintjp]

Thanks for the excellent explanation. If I understand correctly, you are saying that t = 0 is just another tick from a previous state. It does, however, cause me to wonder if the reality of 'nothing' has ever existed or will exist. If it doesn't then would not time be eternal ?

 

I put the comment about the History channel knowing that someone would say exactly what you said. I could not have put it better. This is why so many misconceptions exist and I wish all the scientists could get on the same page and keep this from happening. Unfortunately, like you said, the dumbing-down of America is and has been in full swing for some time now.

[Martin]

... cause me to wonder if the reality of 'nothing' has ever existed or will exist. If it doesn't then would not time be eternal ?

...

 

It's a natural question to ask. Science, though, goes in small steps. I don't know any professional cosmologist who is addressing those ultimate beginning issues technically, about "nothing" or time being eternal or non-eternal.

 

What I see them doing is focusing just on that one narrow time period 13-some billion years ago. What came before that t=0 moment? What conditions led up to the start of expansion?

 

Broader issues necessarily get put on hold. Maybe there was a beginning of time, way way back. Maybe countless universes have branched out like the branches of a tree but the tree itself has a beginning As a rule, working cosmologists don't want to get mixed up in that kind of speculation. It is too hard to make that empirical, testable. It is hard enough to try to get a testable model of just our one big bang that we know about.

 

I can link you to the professional research in quantum cosmology so you can see for yourself and not have to take my viewpoint. I normally only look at the after 2006 publications, but you can change the date on the search. This is the Stanford data base called Spires. Hits are ranked by the number of times the paper has been cited in other research papers. (a rough measure of importance). Don't expect to find anything readable, but you can get something out of scanning the titles (for a brief summary of contents click on a paper's "abstract"). Don't get bogged down, just skate over for a quick impression:

 

Here are the date > 2006 papers:

http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+K+QUANTUM+COSMOLOGY+AND+DATE+%3E+2006&FORMAT=www&SEQUENCE=citecount%28d%29

 

Here for comparison, the date < 1985 papers (back when Stephen Hawking's ideas were being actively investigated)

http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+K+QUANTUM+COSMOLOGY+AND+DATE+%3C+1985&FORMAT=www&SEQUENCE=citecount%28d%29

 

You can see in the early bunch there is a Hawking paper in second place. Top of the list is a paper by Vilenkin, a close associate of Hawking.

There has been an enormous shift in what ideas and models are considered interesting, from the before-1985 period to the after-2006 period.

 

Remember that if you want a brief (if incomprehensible) summary of the paper you click where it says "abstract" under the title. From there you could even get the whole paper by clicking on "pdf". I'm not suggesting this, just noting the possibility.

 

The point is that essentially none of these people are investigating eternal questions*. In the top-cited research community they are all focused intently on modeling and explaining the big bang, and also black holes but mainly the big bang. This is the immediate thing we have the leftover radiation and chemical elements from. It's got to be the focus of attention until it is understood. If they ever get to eternal questions it will have to be later.

 

*They may speculate in words on TV interviews and in talking to journalists, but that's just popular media fluff. The mathematical model building is more focused.

Edited June 4, 2009 by Martin