St. Augustine famously said that God exists outside of time: time is a creation of God, along with the universe; thus there was no “before” the moment of creation. Modern physics tells us something similar. The Big Bang theory, developed by the Belgian physicist Fr. Georges Lemaître who built upon the ideas of Albert Einstein, says the universe emerged from a state in which space and time were distorted beyond what the laws of physics allow us to investigate. Time began with the Big Bang. Lemaître described the universe as beginning on a “day without yesterday”.
How can space and time be distorted? I have discussed this some in my series of posts on Black Holes. Now we dig into the topic more in this new series of posts (click here for all three posts in the series).
PART 3
In the previous post in this series we learned about time dilation and length contraction, distortions of time and space, that are a consequence of Einstein’s ideas about the speed of light, c. We learned about the γ factor. Well, length contraction leads to the strange conclusion that two events that are simultaneous as seen by one person are not simultaneous as seen by another, if there is relative motion between those two observers.
Consider this.
Suppose some people play a little game. They are both in space ships, one red, one blue. They charge toward one another, with the goal being to score a point by being the first to zap the back of the other ship’s tail fins with a little zapper mounted on the nose of their own ship. Whoever first zaps the other wins. The zaps leave marks on the ships to record that they happened, and both teams record the time of zaps.
So, Team Red sees Team Blue heading their way, as shown below. Team Red sees their ship as being at rest, with Team Blue heading at them at speed V = 86.6% c, for γ = 2 (recall the factor γ from Part 2). They measure Team Blue’s ship to be the same length as theirs.
As Team Blue hurtles past, Team Red zaps the Blue ship. But, at the same moment, Team Blue zaps back. Team Red says, “tie point!”
But Team Blue disagrees. Remember, γ = 2. That means Team Red saw the Blue ship as length contracted to half its proper length. Moreover, Team Blue sees Team Red as coming at them at speed V, so Blue sees the Red ship length contracted to half of Red’s proper length. So Team Blue sees this:
You can see immediately that simultaneous zaps are not possible here! No, what Team Blue sees is that, as the much shorter Team Red ship passes by, Blue gets the first zap, as the tail of Red passes by Blue’s nose.
Then, when Red makes it to the tail of Blue, Red makes its futile zap.
Thus Team Blue says, “we won that point, easily!”
Again, both ships are marked by the zaps. Both ships have records of the zaps. The zaps occurred. But the two teams disagree about when they occurred, because motion distorts space and time such that two events that are simultaneous to one observer are not simultaneous to the other. Weird.
There is a lot of other “weird” here. For example, suppose that both teams have clocks mounted at the nose and tail of their ships to record times, and that those clocks can be seen by the other ship. Team Blue’s clocks will read one time for the first zap (from their perspective), another time for the second zap. However, Team Red sees the zaps as simultaneous. So they will see Blue’s nose clock showing an earlier reading than Blue’s tail clock. Team Red will claim that Blue’s clocks are not synchronized. Red will see an earlier time at Blue’s nose clock, a later time at Blue’s tail clock, and (if there are clocks all along the length of Blue’s ship) all the times in between, along the length of the Blue ship — past, present, and future all together! In a sense, Team Red is outside of Team Blue’s time. Likewise Team Blue will claim Red’s clocks are not synchronized, and will see various times in seemingly odd ways.
But now let us add a further twist to all this. Let us suppose that the game works such that when a ship is zapped, its own zapper is deactivated. This would have no impact on things as seen by Team Red; both zaps are simultaneous and both zappers are simultaneously deactivated—everything still proceeds as before and there is still a tie.
But from Team Blue’s perspective, they score the first hit, deactivating Team Red’s zapper. Red cannot zap back. Thus Red says there can be zaps in both directions, while Blue says there cannot be. This seems to be a paradox.
One can easily imagine making the Blue ship a hair shorter, such that Red sees that they got in the first zap, marking Blue’s ship and deactivating Blue’s zapper so that Red should be unmarked and be the winner.
And yet, from Blue’s perspective the Red ship is still much shorter than Blue’s and so Blue still gets in the first zap, marks Red’s ship and deactivates Red’s zapper so that Blue should be unmarked and be the winner. (I have done some searching and have not found this apparent paradox discussed anywhere.)
According to Einstein, motion is not the only thing that can cause time dilation. Gravity can also do it. This has been discussed in other posts (click here or here for them). So, the same sorts of distortions of space and time seen here can also be caused by gravity. These distortions would be very great where gravity is very strong, such as around a Black Hole. Lemaître envisioned the universe emerging from a very small, dense state — and in such a state gravity would also be very strong, such that space and time would be distorted beyond what the laws of physics allow us to investigate. Thus time could begin with that emergence, on Lemaître’s “day without yesterday”.
