Lumen Autumn 2025 - Flipbook - Page 14
Research
If it isn’t real, why have we created it?
Time. Does it exist?
If so, what is it? Discuss…
AE: I suspect the question is somewhat self-undermining.
Creation is a process that happens in time – at least any creation
that humans perform. We can only create if time exists.
University philosopher Antony
Eagle and physicist Andre Luiten
answer the same series of
questions exploring aspects of
time and its importance to their
discipline.
AL: It is real! Humans have created systems of timekeeping based
around seconds, hours, days, years – these are useful, but arbitrary,
ways to use time in a manageable way.
Is time linear?
AE: A tricky issue! Our best physical theories of spacetime seem to
make time linear, in that there is only one time dimension and, for
any three events, one is between the other two. But this line is quite
unlike others we are familiar with – for example, the elapsed time
measured between two events can vary depending on the motion of
the measurer.
AL: In practical terms, yes. However, very careful experiments
show that time can bend and warp depending on the speed or
environment of the observer or the observed. Einstein’s theories
of relativity predicted this and all experiments to date have
verified his theories perfectly.
Does time exist/is it real?
AE (philosopher): Events certainly seem to take time, and to be
temporally related (earlier/later than) to each other. And I think
we are entitled to take those appearances more or less at face value.
That time exists is more plausible than any philosophical (or
physical) argument that it does not exist, although there are
famous arguments in the history of philosophy that time isn’t real.
Why is time important to your field/people?
AE: The nature of time is one of those big foundational questions
that eventually leads every discipline to philosophy. Along with
notions like space, and location, and existence, time features in
almost every scientific theory. Time is also intimately linked to
change and identity, which have been topics of philosophical
interest for 2,500 years.
AL (physicist): Yes, time is real. Deep within science and
philosophy is the concept of “causality” – this expresses the fact
that there are causes and effects in the universe and the ordering
of those events is rigid with the cause always preceding the effect.
Despite all the new things we have learned through relativity and
quantum mechanics, causality is still a foundational belief.
AL: Time is foundational. Almost everything we do in modern
society requires precise measurements of time. Even minor
inaccuracies in timekeeping will throw these systems off, which is
why we strive for extreme accuracy. In my work, we spend a lot
of time ensuring we can measure time exceedingly well, although
(perhaps surprisingly) we spend very little time thinking on its
exact nature.
If time is real, what is it?
AE: Like space, things (both objects and events) take up a
volume of time (duration); things are located in time; and there
is a metrical structure to time. If pressed I would say time is a
dimension, and that the question of the reality of time is rather
like that of the reality of space.
Is time travel feasible? If so, only into the past?
AL: Time is the parameter that orders events and allows us to
measure the rate of change of things. It is as fundamental to the
structure of the universe as is the concept of space. One interesting
observation is that for small, simple microscopic systems one can
run time either forwards or backwards and everything works and
looks to be normal.
AE: Feasible? I would say ask an engineer! But is time travel
possible? – I think so. For a person to persist, philosophers say, is
for that person to be located at many different times. Normally the
times at which a person is located form a nice ‘block’, connected up
and with the stages of our lives progressing in an orderly way.
Perhaps as an analogy, if I were to film balls colliding on a billiard
table, then I could play the film forwards or backwards and you
wouldn’t be able to determine which is the “truth”. However, if
I film someone diving into a swimming pool then it is very clear
which ordering of the film is the “truth”. The arrow of time itself
appears to pop into existence in the move from isolated, simple
systems into large, complex systems. Exactly how this happens is
still an active area of study in physics and is closely connected to
the concept of entropy (disorder) and the way that disorder seems
to increase with time.
As long as their stages are connected to each other in the right
sort of way, a person could occupy a set of times that doesn’t look
like this. Their life may be disconnected, e.g. occupying the years
1900–1920 and also 1980–2040. It may be out of order, with a
‘baby stage’ in 1980, a middle-aged stage in 2030, and an elderly
stage in 1915. A life like that would be a time-traveller, a life where
the ‘internal clock’ of the stages of growth and development and
ageing is not aligned to the external calendar.
AL: One for lovers of science fiction! There is no doubt that you
can move into the future if you move at relativistic speeds (i.e. close
to the speed of light) – check out the “Twin Paradox” on Wikipedia
for an explanation of this and the nice point that astronaut Scott
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