Time. What even is time? We talk about time all the… time in our daily lives and it’s
difficult to imagine a world in which time does not exist. For all we know,
it might just be impossible. Since the beginning of the universe around 14 billion years ago,
the arrow of time has moved forward into the future at a constant speed, and this has had
philosophers scratching their heads over what the exact nature of time actually is. Does time
always move at this speed, or can it slow down or even be reversed? Is time travel possible? Some
philosophers have even questioned whether time even exists at all. The nature of time has massive
implications for our understanding of physics, consciousness, and all those other philosophy
topics we know and love. So in this video, let’s have a look at some of them. Just to warn you,
this video gets weird at times, so perhaps it’s best we start with something a bit more simple.
A MILLION YEARS MIGHT HAVE PASSED SINCE THE START OF THIS VIDEO.
Alright, that’s about as simple as discussions about time can be,
but we can do a thought experiment to make things a little easier to understand.
What if, at some time, the universe paused? All the galaxies would stop in their movement across
the universe, all the planets inside them would remain frozen in their orbits around their stars,
and all the atoms inside them would do the same. Perhaps God had pressed the pause button on the
universe’s remote control as He went to make a Pot Noodle. If this is possible,
that there really could be a stretch of time in which no events or things occurred,
then it’s also possible that you clicked on the video, a million years ticked over,
and then the universe resumed exactly where it was a million years later, and we would
never know. Now that’s some acid-level thinking. If the answer to the thought experiment is yes,
and we can imagine a stretch of time in which no events occur or even occur at a different rate,
this suggests that time exists independent of the stuff that happens within it.
This view is called absolutism, and has been defended by Plato and Newton. With absolutism,
time is like a Tupperware that holds some leftovers, where the Tupperware is time and
the leftovers are all the stuff that happens in the universe. This view does have some intuitive
appeal, as we normally think about time as this unchangeable entity that has always been there
and has continued moving forward at a constant rate. However, if the answer is no, this suggests
that time is dependent on the stuff that happens within it. This view is called relativism, and
has been defended by Aristotle and Einstein. With relativism, time does not exist over and above the
temporal relations between the events that occur. In other words, time exists because stuff happens,
and if nothing happens, then there is no time. This view also has appeal, since Einsteinian
relativity has been so consistently accurate in its explanation of the nature of the universe.
Alright, so we can never be sure that the universe doesn’t freeze now and then while time still moves
on. That’s fantastic, and it certainly does not keep me awake at night in cold sweats of
existential terror. However, things become even weirder when we think about the structure of time.
The common understanding is that time is a line, but all lines have shape, so what shape does it
have? The standard model that most people assume to be correct is that time is a straight line that
extends forever in both directions, and which doesn’t branch into any different timelines.
If this sounds right, then we agree with Plato. If time exists independent of the
events that occur within it, and there can be stretches of time in which no events occur,
then time must be absolute and its features must exist necessarily. But even if we assume
that Plato is correct, this still doesn’t tell us about what these features are,
and so it’s unhelpful in that sense. If this sounds wrong, then we side with Aristotle.
If time is dependent on the events that occur within it, then whatever features time
has must depend on whatever happens. It just happens that time appears as a straight line.
However, this still works on the assumption that, in our universe, time really does
have a straight line. But does it really? I mean, who among us is totally straight?
Perhaps we should take more seriously claims that argue that time is not a straight line,
but rather that time is bendy, or discontinuous. Perhaps it does branch
off here and there into separate streams in which different timelines have come to pass.
It could be that there are even multiple different time streams that run alongside each other,
in which time is defined on the relations between events in their own streams,
but never those in a different stream. And then there’s the question about the direction of time.
We know time can move forward, but could it move backward or side to side? Can it throw
some moves on the dancefloor and wave its hands in the air like it just don’t care? There are
many different theories on the nature of time, but unfortunately, our troubles don’t end there.
Even with all that considered, there’s a final question we can ask about time. Does it make a
difference where inside time something exists? In other words, does the existence of a thing
depend on whether we are talking about the past, the present, or the future?
Well, there are two different views that could provide an answer. On the one hand is presentism,
which holds that the present is all that exists, and that there is no such thing as
the past or the future. If a presentist were to make a list of all the things that exist,
it would only have things which exist now. We would be on the list, but Socrates and Theseus
Incorporated wouldn’t, because their homes are the past and future, which do not exist.
While it seems unbelievable, this view does have some appeal, because there is a sense in
which Socrates clearly does not exist now. We are comfortable to say that Socrates existed,
and that he exists no longer. But this view also falls into some problems. If we can still talk
about Socrates, and agree on what we mean, then what the hell are we talking about? If Socrates
does not exist, as presentism claims, then what does the word ‘Socrates’ actually refer to?
On the other hand, we have eternalism, which holds that objects from the past and the future
exist as well as the present. In other words, Socrates and Theseus Incorporated do exist,
but just not right now. We might not be able to see them or interact with them,
and they might not have any spacetime coordinates in the present, but we should nonetheless include
them on our list of existing things. On this pure eternalist view, a thing’s location within time
does not affect their ontological status (whether that thing exists or not),
but to make things even more confusing, there’s a more specific strand of the theory where it does.
This view is called growing universe theory, and it views time as fresh slices
of the present being added to the past. If we made a list based on this theory,
it would constantly increase in size as things move from the present into the past.
We live, as it were, on the edge of the proverbial time knife. Each new moment is a new entry on the
list, and we are forever on the forefront of all things that exist, until the time comes where we
move into the past for good. And you know what, if nothing else, I think that’s pretty damn cool.
Right, so there is clearly some debate about time. Whether it’s absolute or relative, whether time
has ever been curious about its sexuality, and whether the past or the future actually exist.
It’s no stretch of the imagination to argue that time is the most important factor in our lives.
It decides when meetings happen, dictates when trains and buses leave the station,
and severely limits how long I can last in the bedroom. Time is perhaps the most
mind-bending of all the mysteries that we have not yet decoded, and it represents a
neat crossover between physics and philosophy. I find that’s always where the good stuff happens.
Thank you very much for watching, peace and love, and I’ll see you in the next video.