Time is an illusion, lunchtime doubly so.
So what time do you make it right now? Probably every single person watching will have a different
answer, not just because you watched this video at different times during the day, but
also because we have to deal with time zones, different clocks and varying degrees of accuracy,
but mostly because you bought that suspicious “Rilex” watch for $5 in Singapore.
The idea of time existed long before clocks so how do we define it, what is time and what
are some of the amazing and strange ways it can affect our lives?
Early attitudes towards time were relatively simple; we used the motions of the sun to
give us an understanding of our place in the day. Sun high; find food, kill food, eat food.
Sun low, find woman, go to cave, shout at woman till she make fire. There were also
the shifting seasons which we weren’t able to measure but you would learn to follow them
and predict them from the way that nature changed around them.
The first instruments to make time measurements were sundials. But these were highly localised
and, from our perspective as clock users, the times would be different each day since
the amount of daylight increases and decreases steadily throughout the year, by just over
2 minutes per day in fact. This means that a specific point on the sundial would actually
be reached slightly early or later the following day.
There were various other measures, like sand timers and water clocks, or just counting
how many teeth you had left. It wasn’t until the early 19th century that we had reliable
mechanical clocks. Still, they weren’t all running at the same speed, but at this point,
it didn’t really matter. People in each town worked to one main clock, and the bells
would ring out every hour on the hour and that’s how the day would be organised. Then,
when you went to a different town, you would then work off that clock, which might run
at a different speed. But the difference was so small that you wouldn’t notice the change.
Then, came along one significant technology that made us realise that we had to synch
up all of these different clocks. And that thing was railways. Imagine trying to organise
a train schedule where every stop on the line thinks it’s a different time, partly because
of their own town clock but also due to their different positions on the globe. A city like
Bristol, only a couple of hour’s car journey West of London, would have a solar noon, that’s
the point when the sun is at its highest in the sky, about 10 minutes later than London
thanks to the 2.5 degree difference in position. So we needed a standard or it would be chaos.
On December 1st 1847, time really began, with the adoption of Greenwich Mean Time, which
was often referred to as railway time. Until 1880, when it became all of Britain’s legal
time, many clocks would show both local and GMT on separate faces. The time zones in the
US became vital since the differences over such a large country were even greater. That’s
also where the word “hello” comes from. A telephone greeting needed to be adopted,
rather than good morning or good afternoon, since you could be talking to someone thousands
of miles away and their morning might be your afternoon. Alexander Graham Bell, inventor
of the telephone, preferred the phrase “ahoy-hoy”. Imagine how much more fun the world would
have been if that had stuck. Soon each county in Britain had standardised
time and then the world began to coordinate as communication and travel became ever faster.
Most countries related their time to GMT by 1929 but it wasn’t until Nepal signed up
in 1986 that we had a complete global system. Okay, so that’s the basic history, now let’s
talk about the theory. What exactly is time? Or at least, how can we define it? Well time
is really three things or concepts that share a common name.
First, it is a way to label and order events in the universe. I buy a tub of ice cream,
I eat all the ice cream, I feel sick and slightly ashamed of myself. I need something that can
show that buying comes before eating, and then sickness and shame follow it. This is
ordering, like a calendar. Second, it’s a way to measure the distance
between two events. The ordering tells me which comes first but it doesn’t say how
far apart they are. If I get a new job and then a new car will they happen 2 weeks or
2 months apart? And thirdly, and this one is a little more
abstract, time is a medium we move through that allows us to see that change has actually
happened. The leaves turn from green to orange, wrinkles grow under your eyes and that beer
belly swells ever larger. This gives us the concept of past and future. It’s interesting
that the Ancient Greeks saw the future as something that snuck up, unseen, behind their
backs, while the past was laid in front of them, for them to stare out into. Sneaky future,
you never know what it’s up to. This third concept is really important because
it’s the only one that requires us to have an arrow of time, a direction it moves in
and never changes. The future cannot come before the present; the smoke never returns
from the air into the cigarette, the milk never un-swirls out of our coffee and I don’t
eject that ice cream into the tub, walk backwards to the shop and exchange it for money, that
would be weird and gross. The reason many things seem strange when you
play them backwards is because of Entropy. Entropy is the second law of thermodynamics
and of all the rules of physics, it’s probably the one we are surest about. To put it simply,
entropy is the measure of the order or disorder of a system. The law states that the entropy
of a closed system will either remain constant or increase with time. This means that you
always go from ordered to disordered. Think about your bedroom. You tidy it and then it
always slips slowly into a chaotic mess. And say in that mess you find a chocolate bar;
that is a nice, ordered, delicious collection of energy. But then you stuff it in your face
and that stored calorie energy turns into kinetic energy for walking, heat, even sound
for when you tread on something in the dark and scream. I told you your room was messy.
At least now you know it’s not your fault. It’s just entropy.
Think about a coffee with milk in it. The milk will always stay mixed throughout the
coffee, it will never separate so you have an area in the cup of just milk and an area
of just coffee. If it does, then your milk was really out of date and has evolved into
a sentient being. But why is this? Well, it’s really just
probability. The amount of ways you can organise something into a useful or ordered way, is
much much smaller than the ways you can organise it into a chaotic, meaningless way.
Let’s take writing as an example. If you close your eyes and randomly bash letters
on your keyboard for a minute, it’s unlikely that you will make many words because there
are so many combinations of letters but only a few combinations make real words. Take the
word “Piggy”, “P I G G Y” there are no other words in English made from just those
5 letters; yiggp, giypg, pygig, no. One more example. Put an ice cube in a bowl
of water and it will melt and you’ll end up with a bowl full of slightly more water.
Now if you reversed time, you would expect the ice cube to form out of the water; but
how would this be possible? How would all those water molecules decide which of them
had to become the ice and which would stay as water? It doesn’t make sense. Entropy
is how we know that time is destined to move in one direction.
Alright so we know that time has a direction but what about a speed? Is time moving at
the same rate for everyone and everything? No, it isn’t, it’s relative to the speed
you are moving and by gravity. The faster you are moving, the slower you experience
time compared to someone who is not moving. This is part of Einstein’s Theory of Relativity.
You can see relativity in action every day. For example, if you’re on a moving train
and you throw a ball up in the air then catch it, you only witness the ball moving at the
speed you threw it. Whereas someone stood on the platform as the train shoots past them
at high speed, watching you throw the ball in the air through the window, will see the
ball move much faster. Because they will see it move at the speed you threw the ball plus
the speed of the moving train. Now, the problem comes when we swap the ball
for a beam of light. Most of the time the speed of light is fixed, although it can be
slowed down nothing can travel faster than it. So take the same example but swap the
ball for a beam of light, the train is moving and you throw the beam of light up in the
air. So in this instance the onlooker would see the light beam travel at the speed of
light plus the speed of the train. But that’s not possible because you can’t exceed the
speed of light. So something must have happened to the time to make up for the lost speed,
therefore in this example, you and the onlooker would be experiencing time passing at a different
rate. This is called time dilation and it’s a
great excuse for being late, since you can claim your watch was just going slower because
you walk so fast. But in reality, this difference is negligible. The astronauts racing around
the earth at almost 8km/s in the ISS have aged about 0.005 seconds less than us back
on Earth in the past 6 months. Gravity also affects the flow of time in the same fashion.
The stronger the gravity the slower time passes. So if you were stood on a planet with several
hundred times the mass of Earth for just one hour, a whole year will have passed back here
on Earth. Relativity will never truly have an impact
on our lives, until we can build ships that can move at close to light speed. Then, you
could go off on a trip to some star and come back to find all of your relatives long dead
and buried and a bill of £14 billion because you forgot to cancel your phone contract. That’s the physics side of things but what
about personal relativity. Why is it that your current situation affects how fast that
you feel time is passing you by. One hour in a chemistry class definitely doesn’t
feel the same as one hour out in a bar, unless you really love chemistry or you’re rubbish
at drinking. When you’re a kid, summer seems to stretch
on forever but as you grow into adulthood, summer is gone in a blink and you can’t
remember what year it is and you realise that you missed your mum’s birthday again. And
what about those rare moments of extreme danger or intensity? If you’ve ever been in a serious
accident, you’ll remember that feeling of time slowing almost to a halt and it seems
like you’re processing everything at a far quicker rate than ever before.
A neuroscientist called David Eagleman became fascinated with this idea and with how the
brain measures time. Your brain is incredibly accurate when it comes to time. Take sound
for example. When you hear a loud bang, you turn your head towards the source of the sound,
but how do you know where it’s coming from? Well, that sound travels from the source and
hits each of your ears at a slightly different time, thanks to the width of your head, which
is how far apart your ears are. This time difference is as little as 9 microseconds,
that’s 9 millionths of a second, but your subconscious brain is still able to recognise
and use this information to calculate where the sound is coming from. You also track the
rhythms of the day and night, without needing to see the sun. Your brain can measure seconds,
minutes and hours passing by with incredible accuracy. Ever woken up exactly 1 minute before
your alarm goes off? That’s no coincidence, your brain is like a little Swiss watchmaker’s
house, stuffed full of various time keeping devices, and possibly some cheese.
Eagleman tried to test the effect of high intensity situations. The problem was, you
can’t just go around pushing people in front of cars or dropping their pets out of windows
to see how they react. So he found something called a suspended catch air device, that
basically involves dropping people through a hole, while they face upwards so they can’t
see the safety net behind them. He gave each volunteer a screen on their wrist, which would
flash a random number slightly faster than the eye can normally see. If they did experience
time slower, then hopefully they’d be able to see the number. Sadly, it didn’t work
but they did note that when asked how long they thought the fall had taken, volunteers
overestimated by an average of 36% so something was happening to their perception of time,
but this phenomenon still largely remains a mystery.
And finally, we can’t talk about time without mentioning time travel. Travelling to the
future is clearly possible, thanks to special relativity, all you need to do is keep travelling
close to the speed of light and life on earth will race by much quicker than your personal
experience of time. Traveling close to light speed is no easy task though, it would require
absolutely enormous amounts of energy. And imagine how disappointed you’d be if you
got out your ship and still no one had invented x-ray glasses or a reverse microwave to make
your beer cold in an instant. Without those, the future is totally pointless.
Travelling to the past is a little trickier and we’d almost certainly need some sort
of wormhole to achieve it. But it’s at least theoretically possible, having a wormhole
to the past would not defy the laws of physics, even if it does lead to the potential for
paradoxes, such as the bootstrap paradox. This could be where a young man travels back
in time, meets a girl and gets her pregnant. He leaves, because he didn’t get into the
time travel game to get tied down. But the woman gives birth to a boy, who ends up being
the time traveller. He is, without knowing it, his own dad. It would make parents evening
at school very confusing. So time is many things, it can be a measurement,
a concept and even a way of travel. We still don’t fully understand the complexities
of time and maybe we never will. But in the end it doesn’t matter what it is, or how
long it is, it’s what you do with it that counts.
