[Aside: Wow, look at this. A front page full of new posts. Who would have thunk it?]
We are a group of scientists and we have invented a time machine. Well at this stage it's more of a time probe, but if this model works we're hoping to scale it up for human subjects. The time probe works thus: We set a period of time (say one year) and send the probe back. It travels backwards through time (don't ask me how it does this, the process is far too complicated) and when it reaches one year in the past, it stops its travelling through time and instead comes back to the present, returning to us instantaneously (or so it appears from our perspective). We have already tested the ability of the probe to travel one year into the past and back, one million years into the past and back, and one billion years into the past and back. Given our understanding of how the probe works, we are sure that it is completing its allotted task admirably. However, we have one burning question. Not, who shot Kennedy (yawn)? Not, what size sandals Jesus wore (boring)? No, we are after far more interesting quarry. The question we are interested in is, how far back can we send the probe? Is the past infinite or not?
Now unfortunately every number that we can think of (a billion, a trillion, a quadrillion, and so on) has always resulted in the probe returning successfully. So we know that the universe is at least a quadrillion years old. Eek. However one bright spark in the physics department has suggested that we make a little adaptation to our probe: When we send the probe back N years, it will check to see if there is an N+1 (otherwise known as yesterday). If there is a yesterday then it is clear that it must travel further back and the probe travels to yesterday, rather than returning to the present, and thus removing the need for the probe to keep travelling to-and-fro from the present. Now, this all sounded like a good idea, but we sent the probe off last week, and it hasn't returned yet. The lab sweepstake is currently split 50/50 between those who believe we will never see the probe again, and those who think it'll turn up any time. I suggest we do not hold our breath!
Okay back to reality (hehe). This post was inspired by Whitrow's paper On the Impossibility of an Infinite Past. Now I don't claim to be an expert on any of this. At best it is intended to be thought-provoking (and remember Cantor went mad thinking about infinity). But it does appear that if there is a yesterday, and a day before yesterday all the way into infinity, then how in the heck do you get back to the present? Apparently I'm not the first to think like this. From St Bonaventure (1221-74):
...if the universe had no beginning an infinite number of celestial revolutions must have taken place, and therefore the present day could not be reached.
But then take the number line on a ruler. Between 1 and 2 are a range of numbers: 1.1, 1.2 et cetera. And between those 1.11 and 1.12 and so on. And we can do that ad infinitum (or at least until the cows come home). But nobody complains that they cannot draw a line using a ruler because infinity stops them. Ah it's all just a little confusing. I think in reality there must be an infinite past and infinite universes, otherwise the Copernican principle would be violated—this is the idea that we are not occupying a special frame of reference in the universe ("Oi. Speak for yourself!" a voice from the back shouts). But our universe has only existed for a finite amount of time (approximately 14 billion years) and whilst this fact appears to violate the Copernican principle (one special universe is no better than one special Earth), my gut feeling is that this is a visibility bias, and were we able to see the rest of the universe in all its random and chaotic majesty, we would see we are a small (insignificant) part of a much larger whole. Not that this whole is actually doing anything mind you. I mean WTF. God is some mad scientist creating a giant infinity madness machine. Step away from the drugs Mary Jane. That kind of thinking really isn't going to get you anywhere.
Lastly, this Whitrow paper describes the story of Tristram Shandy:
Tristram Shandy, in Sterne's famous novel, on finding that it took him two years to write an account of the first two days of his life lamented that material for his biography would thus accumulate faster than he could deal with it, so that he could never come to an end. 'Now I maintain', argued [Bertrand] Russell, 'that, if he had lived forever, and not wearied of his task, then even if his life had continued as eventfully as it began, no part of his biography would have remained unwritten.'
But that just seems crazy. Okay I get that he has an infinite time to complete the task, but on the other hand, every day brings a new account to write. How can he ever finish? Maybe he needs to take a nine year break, like I did with this blog! Okay time literally does my head in. Ha. Nice thoughts to think sometimes though right?Go Top