I've already explained how to resolve this in other threads.Present awareness wrote:The difficulty with the concept of time, is that it could NOT have a beginning or ending, because just like with the concept of numbers, we could always add one more digit or one more second. If time were infinite though, an eternity of time would have to pass, before we could even be born. I believe that is why it makes sense to say that time started about 13.7 billion years ago, but if time had a start point, does that mean it also has an end point?
Time could have a beginning and ending, because there is no reason to assume that just because we can imagine "more digits", that that actually reflects the real world. Just because we can imagine the Universe existing for another quadrillion years, does not make it so. And just because we can "subtract digits", i.e. imagine a Universe that always existed, that does mean that that is the way it is.
However, time could also have always existed, and could always exist. That is also a definite possibility. And that is what your analogy shows --- because we can imagine "adding or subtracting digits" the possibility exists. But only the possibility.
The resolution is to understand that both are true! And here is how to resolve that:
Time indeed began around 13.7 billion yrs ago. But when this is stated, ordinarily the unit of measurement is assumed to be constant. As if the 1 billion years after the BB (0-1mil) were the exact same as the last 1 billion years (12.7mil-13.7mil). But this is not so.
The conditions of the Universe were far different during the first billion years. The Universe was smaller, for example. Space-time was smaller. Total mass was less (science would dispute this). And the point is that "one second" then wasn't the same as "one second" now, although the actual number and unit of measurement is the same.
To give an analogy, it would be the same as if you measured an object here on the Earth, and say it was 12" long. Then, the entire Earth grows bigger. Let's suppose it doubles in size and mass. Not just the Earth itself, but also each individual object on it. So now your ruler, which still says 12 inches, is actually twice as long, but there will be no way for you to know that. Since everything is bigger, there will be no reference points to notice that it is all bigger. So when you measure the same object, although it has grown to twice its former size, it will still measure 12 inches long.
The same applies to the Universe as a whole. It's getting bigger and bigger, but since it is Everything, i.e. Everything is getting bigger, there is no way to know it by reference, i.e. there's no way to know it. And that is also applicable in the space-time paradigm. Time is getting "bigger" too.
The practical effect of this would be that if you took off in a time-machine, with the intention of going back to the big bang, you would notice something unusual. Although the speed of the ship is supposed to be constant, say you go back 1000 years every second, you would find that it isn't. At first, each second you would notice that you went back in time another 1000 years. But after some time, you'd start to notice that it was taking longer and longer to go back in time the same amount. You'd notice that it took 1.2 secs, then 1.5, then a whole minute, until finally, as you got closer and closer to the primordial big bang, you'd find it would take an inordinately long time to travel another 1000 yrs back in time. Eventually it would take years, until it appeared that your time-machine was at a virtual standstill. And this decrease in the apparent 'rate of speed of time travel' would correspond exactly with the change in the relative size (in terms of mass) that the Universe was in at any particular moment in time.
The underlying math behind all this is quite complex, but after a lifetime I'm convinced that that would be our experience if we ever invented a time-machine that could really go back in time.
So yes, the Universe indeed did begin 13.7 billion years ago, but since the measurement of time is relative, we can also say that the Universe always existed. It actually began, but from our perspective and for all practical purposes it always was....