Time
One thing after another
Time is queer. It seems so fundamental that it's hard to imagine anything without it. And as we might expect of something fundamental it seems hard to define time in terms of anything else. The question “What is time made of?” seems absurd. Time has to do with sequences of events. Reality is just a long sequence of one thing after another. We experience that directly.
And yet, in the equations of physics, time is a variable that can have a positive or negative value. In physics the past and the future are the same - displaced from the present by a certain amount of time. So is time just an artifact of our own experience rather than something important in reality?
Think about a star - it's what happens when a cloud of gas in space collapses to a centre under the influence of gravity. The presence of the star now shows that that process happened in the past.
Doesn't that show that time is more than an artifact of our experience? But if we change our perspective from the star to the atoms that make it we see time differently. Events still happen in sequences, but you can't distinguish past from future.
At the scale that we live at entropy makes it possible to tell the future from the past - the future is more disordered. But what could be more disordered than the quantum jitteriness of atoms and sub-atomic particles? There's a certain symmetry to time at that scale - there is nothing to indicate the passage of time. Every time you look everything looks the same.
Geology gives another perspective on time. The flow of energy from the sun and from the stored energy of the earth continually churns the material of the earth. And as happens when material is churned by energy the matter becomes ordered. We are familiar with what that order out chaos looks like - it's the landform of our planet. Mountains are pushed up out of the oceans and eroded back into them in a continuous cycle. And the result is the sort of fractal terrain we live in where the landscape of the past was very much the same sort of landscape we have now.
If we think of change through time of things like stars or mountains the change happens at the same rate for long periods of time punctuated with sudden shifts. Think of a cloud of gas collapsing into a star. For millions of years conditions are much the same - just a cloud slowly becoming more dense. Then a critical density is passed and fusion reactions start. Then for millions of years conditions are much the same again.
Perhaps it is this situation of a state of affairs existing for a long time that motivates the predictable equations of physics. It's the form of those equations that raises the possibility that the time variable can be positive or negative. But every predictable system also has bifurcation points; points where all the rules suddenly change and the system starts evolving in a new direction. Like when fusion ignites in a star.
We are creatures that act. If one traces our trajectory through time the line is jittery and constantly changing.
So time for things that can act is very different than it is for things that only exist. Instead of producing a feeling of predictability where the future is like the past the experience of things that can act produces the feeling that the past is irretrievable but memorable and the future is rushing upon us and is unknown. So we feel the passage of time in a way that a star or a mountain doesn't. We care.
What do you think?
I present regular philosophy discussions in a virtual reality called Second Life.
I set a topic and people come as avatars and sit around a virtual table to discuss it.
Each week I write a short essay to set the topic.
I show a selection of them here.