Does time exist? The answer to this question is obvious. Look at a clock or calendar.
The existence of time is an open possibility, and one that we should take seriously.
What would that mean? It will take a little while to explain, but don't worry: Even if time doesn't exist, our lives will go on as usual.
There is a crisis in physics. For the past century or so, we have explained the Universe with two wildly successful physical theories.
The world of particles and particle interactions is described in quantum mechanics. The big picture of gravity is described by General relativity.
Both theories work well, but they are thought to conflict with one another. Scientists generally agree that a new, more general theory is needed for the conflict.
Physicists want to create a theory of quantum gravity that replaces general relativity and quantum mechanics. The theory explains how gravity works at the smallest scale of particles.
Producing a theory of quantum gravity is difficult.
string theory is an attempt to overcome the conflict between the two theories. The strings vibrate in as many as 11 dimensions.
string theory is facing more difficulty. There are a number of models that describe a Universe like ours, but they don't make any clear predictions that can be tested in an experiment.
Physicists came up with a range of new mathematical approaches to quantum gravity after they became dissatisfied with string theory.
One of the most prominent of these is loop quantum gravity, which proposes that the fabric of space and time is made of a network of extremely small chunks.
loop quantum gravity appears to eliminate time completely.
A number of other approaches also seem to remove time as a fundamental aspect of reality.
We know we need a new physical theory to explain the Universe, but it might not have time.
Suppose the theory is correct. Is it possible that time does not exist?
It depends on what we mean by exist.
We still accept that tables, chairs, and people exist even though theories of physics do not include them.
Why? We assume that such things exist at a higher level than the physics describes.
Tables emerge from an underlying physics of particles in the Universe.
We have a good idea of how a table might be made out of fundamental particles, but we don't know how time might be made out of something more fundamental.
It is not clear if we can assume time exists if we don't have a good account of how it happens.
Time may not exist at any level.
It's like saying there are no tables at all.
Trying to get by in a world without tables might be difficult, but managing in a world without time seems disastrous.
Our lives are built over time. We plan for the future because of what we know about the past. We hold people accountable for their past actions, with an eye to disciplining them later on.
We believe ourselves to be agents because we can plan to act in a way that will bring about changes in the future.
What is the point of acting if there is no future to act for?
When there is no past action, what is the point of punishing someone?
The world would grind to a halt if time did not exist. We wouldn't have a reason to get out of bed.
There is a way out of this mess.
The sense in which one thing can bring about another is unaffected by physics.
The basic feature of our Universe is causation and not time.
Agency can still survive if that is correct. It is possible to reconstruct a sense of agency completely in terms of causality.
In our new book, we argue that.
The discovery that time does not exist may not have a direct impact on our lives.
Sam Baron is an associate professor at Australian Catholic University.
This article is free to use under a Creative Commons license. The original article is worth a read.
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