Lumen Autumn 2025 - Flipbook - Page 15
The (non?)
existence and
(un?)importance
of time
earlier to later? Or is the direction of time derived from how
things are in time? For example, many would say that the direction
of time is grounded in a thermodynamic asymmetry – on this view,
the future is just by definition whatever direction entropy tends
overall to increase in.
Kelly aged eight milliseconds less than his Earth-bound twin due
to a year spent on the Space Station. Essentially Scott Kelly has
travelled eight milliseconds into the future. Very much longer trips
in time than this would be technically very tricky. It appears that
there is no scientific means to travel backwards in time.
How have human concepts/understandings of time
changed, over time?
AE: For most of known history, time was seen to be ‘flowing’ or
‘passing’, and only present things were taken to be real. It took until
the twentieth century to see thinkers toying with the denial of these
claims – to think that past and future might also be real, and that
the flow of time may be an artefact of our cognitive systems.
AL: Humans started measuring and dividing time using the
natural astronomical cycles that were around them – day and night,
seasons, lunar phases. As society desired more timing
precision than available from calendars and sundials, it drove
the development of mechanical clocks that were placed high in
cathedrals and town halls to provide agreed time to an entire
town. The next huge leap in timekeeping was driven by the desire
to navigate over the oceans with high precision. The final great
leap in timekeeping has come with the ongoing development of
atomic clocks since the 1950s - the best modern clocks are capable
of measuring time to one picosecond per day (one thousandbillionth of a second).
Is there a bigger question I should have asked about
time, pertinent to your field of expertise? If so, what
is it, and how would you answer it?
AE: I’m not sure they are bigger questions, but there are two
which are the focus of considerable discussion at present. First,
the question of the direction of time. Is time itself ordered from
Second, the question of the fundamentality of time. Time might
be real, but it might be grounded in something more fundamental
– in the same way the economy is real but may be grounded in the
behaviours and dispositions of individuals and institutions. Some
think a future theory of quantum gravity will explain time (and
space), and yet may not itself involve spatiotemporal notions.
AL: The Global Positioning System (GPS) underpins the effective
functioning of our communications, internet, logistics as well as
our ability to navigate a foreign city and get a pizza delivered to
our house. The benefit of GPS to our global economy has been
estimated at more than 2 billion dollars per day. What might not
be as well understood is that the heart of GPS is a constellation of
orbiting satellites on each of which are several very high-quality
atomic clocks. Further improvements in timekeeping ability could
allow a next-generation GPS with increased precision which could
answer a slew of economically valuable tasks.
Associate Professor Antony Eagle has a research focus of theoretical
philosophy including the philosophy of physics. He has previously
lectured at Oxford and has a PhD from Princeton. He is Editor
of the Australasian Journal of Philosophy.
Professor Andre Luiten is Chair of Experimental Physics at the
University and Chief Innovator of our Institute for Photonics
and Advanced Sensing. He and his team won a Eureka Prize
for the development of the world’s most precise clock – the
Cryogenic Sapphire Oscillator.
Story created by Mark Douglas, Editor of Lumen. Image by
Isaac Freeman, photographic editor.
LUMEN
