Expert: Tom Whiting - 2/15/2012

Question
QUESTION: Hi Tom. Could you please give me a quick overview of expansion rates of the universe. Is the following BROADLY accurate? Big Bang is the start of inflation, inflation lasts less than 1 second, expansion then slows down to a rate drastically lower than inflation rates, expansion rates gradually increase to present date where it continues to increase. Concerning the answer you give me....Do phycicists who accept BB generally agree on these expansion rates. In other words, are there any decent (not wild) theorys that would disagree with the generally agreed expansion rates. Thanks for your time,  Richard.

ANSWER: Hi Richard,
Excellent question and I thank you for it. Yes, it is broadly accurate.  So, yes, the non-wild physicists are all pretty much in agreement with your statement above, with a small correction needed. After the inflation event, the expansion rate continued to decelerate (due to gravity) until about 1/2 the age of the Universe (the first 6 or 7 billion years).  Then gravity became so diluted (from the volume increase) that the dark energy component took over and began to accelerate the expansion rate after that.  So the Universe continues to expand and accelerate it's expansion, and this will go on until the Big Rip or heat death (absolute zero), whichever occurs first. (NOTE - the Big Crunch is completely off the table now).
Now we need to check and see if the current acceleration itself...  is accelerating.   [And, is THAT acceleration also, accelerating???? (?)]
If so, then we have to drastically reduce the total lifespan of the Universe down from hundreds of trillions (a trillion being 10 to the 12th power in USA) of years, down to about only 30 - 50 billion years total lifespan.
Any (non-wild) decent theories that disagree with all this?  Not that I'm aware of at present, because the  stated theory above agrees with (and was developed from) what really appears to be happening, according to all our observations.
(In the stock market don't fight the FED, and in science, don't fight with Mother Nature!)
Hope this helps,
Clear Skies,
Tom Whiting
Erie, PA USA    


---------- FOLLOW-UP ----------

QUESTION: Thanks for clearing that up. Two surprises there. I wasnt aware that acceleration slowed for a period, or that the big crunch had been ruled out. The reason for asking this question...We know gravity affects the passage of time. As we go back towards BB, matter is more concentrated. Gravity fields most have been much stronger. Surely this must have had some affect on time? What we measure as, say a year, would be vastly different from a year in post BB eras. Does the estimates of expansion rates, and ultimately, the age of the universe, include any kind of recognition of time passing at different rates? What I might imagine (as best I can) as 15 billion years might be better measured as say 50 billion years, based on what I measure as a year NOW. Hope this makes some sense; I think you understand my general point. Thankyou for your response, Richard.

ANSWER: Yes, well with the very low density of the Universe now (compared to say one second after the Big Bang), time passage is about as fast as it can go (pass) now, in today's Universe... kind of like the absolute temperature of the Universe is now 3 degrees above absolute zero, down from unimaginable trillions of degrees at the Big Bang, maybe even hotter.  You only have 3 more degrees to drop to the lowest possible temperature where all motion stops.

Change in time passage is kind of the same way.  Today, the only way to significantly slow time down is get up very close to a black hole (or get up over 85% light speed)!  And even then, all the BIG change occurs in those last few "percents"  as you approach the event horizon (or approach light speed),  because time dilation effect (for velocity) is given by the Lorentz transformation equation where its equal to "Rest Time" divided by the square root of 1 - v squared over c squared.  
Yes, time was zero at the instant of the Big Bang... that's how we know that time began at the Big Bang, because of the massive singularity.
So in the far distant future, "one year time passage" won't be that much different than today's one year time passage. (At least as far as General Relativity and mass are concerned).  Because the majority (over 99%) has.... already happened due to the very low density of our current Universe. So future 15 billion year increments would never dilate to 50 billion years... might equal (dilate to) 15.00001 billion years, but that would be about it.
So in today's Universe, the really big change in time passage only occurs going the other way... when you approach a massive body like a black hole... time passage becomes zero as you hit the event horizon... or in Special Relativity, when you hit 100% c.
Hope this helps,
Clear Skies,
Tom    



---------- FOLLOW-UP ----------

QUESTION: Thanks once again, thats the first time Ive had an answer to this thought that has annoyed me for years. If Ive understood correctly you are saying time dilation is insignificant because the universe has spent most of its time in the un-extreme state its in now. So, a slight dilation, at the start, is inconsequential. If Ive understood that correctly then it makes sense to me. I may have asked you this in the distant past so please forgive me. I have read a bit about inflation-vacuum energies etc, not fully understood but a general grasp. Couldnt time dilation (for want of a better expression) have some relevance in inflation? If time was slowed down enough, expansion would appear rapid. If 1 second took (our)10yrs to pass, lots of expansion would have passed!! Sorry if Ive been a real bore-thats it on the subject for me! Its been quite informative for me. Thanks, Richard.

Answer
Well, the problem with time dilation (extending one hour to say, one month) is that neither observer... the one experiencing the effect on, say a craft up near lightspeed, AND the outside observer standing relatively stationary on the Earth where one second "feels like" one second,
they both think that they are correct with respect to time passage.  The space traveler thinks everything is "normal" too, and to him also, one second would "feel" like one second.
(The original movie "Planet of the Apes"... got it right!  Up near lightspeed, astronauts aged only a few years in their timeframe, whereas some 4000 years passed on the Earth's timeframe!)

How can they both be right?  Because they are in two completely different reference frames.
Remember, Einstein said with his relativity, that you FIRST have to define your reference frame with respect to gravitational field and velocity relative to light, before you can even discuss anything accurately with another "outside" observer.  Because both observers can be correct in their respective reference frames.  In the example above, the only way the space traveler would even know that he was in a time dilation effect due to speed, would be if he had a powerful telescope and could instantaneously see a clock back on the Earth... he would observe that the Earth clock appears broke because he would observe that the hands are moving rapidly through an hour in only a couple of "his" seconds.
And the Earthly observer with a powerful telescope would see the clocks onboard the spacecraft
must be broke too, because they are barely moving... it takes almost an Earth hour to click off even one second on the spacecraft clocks... so the spacecraft clocks all must be broke and defective too.  BUT, they aren't!
In reality, both are keeping the correct time... for their own reference frame.

 Also understand that we cannot visualize a "big bang" from the outside... but only from the inside, because we (our entire Universe) is in the Big Bang residual influence.
(That's why no matter which direction you observe the night sky, we are always looking back in time... because we are "IN" the Big Bang remains and influence.)
So there was no, nor could there ever be, "outside" observer to the Big Bang. So our first view, if we could magically exist several seconds after the Big Bang, would be of all this sub-atomic hot matter and hot energy, rushing away from us in all directions. That would be the "REAL" view of an observer stationed in the Big Bang several seconds after the event. (Because we are (and have to be) IN it, not outside of it.)

Also, the inflation effect at the very beginning was really not a "velocity" many times faster than light.  Besides, only matter and energy are bound by c; not spacetime, shadows of spacecraft, all non-material events including spacial expansion, are NOT bound by lightspeed.
Picture this... a unimaginably large portion (10 to the googleplex lightyears) of the Void that existed just prior to the Big Bang... is about to become "our Universal Space-time continuum".
Then at the Big Bang instant, this unimaginably huge volume just suddenly becomes... our entire
space-time continuum.  That's the more proper way to picture it rather than a "rushing" out of space at a velocity much greater than c.  Because that's the way it actually had to happen.
And remember it's this spacetime that is accelerating and expanding, not the matter and energy in it.  The matter... just goes along for the ride, like an empty canoe going down a mountain stream faster and faster. (It's not the galaxies expanding... there are no "little rockets" attached to the galaxies moving and expanding them.... it's the spacetime itself. Like the canoe, the galaxies just go along for the ride.
Hope this helps,
Clear Skies,
Tom