Why Did Time Start Going Forward?

[Music]

a roman bishop sits in the window of his

episcopal home

on the north african coast it is late

afternoon

he looks out at the sun setting over the

mediterranean

and watches the waves break along the

shore sand

piling into disordered heaps when the

sun sets

it will be time to light the lamps if he

wants to continue his work

he is augustine of hippo theologian

philosopher and saint famed for his five

million words of writing

that have survived to the modern age he

longs for the golden light to remain

for time to pause or even run backwards

what might that look like

he considers the sun would rise from the

horizon not so different to the glory of

a dawn

but all else would seem very strange the

waves crashing on the beach must collect

and assemble themselves in the most

unnatural fashion

with water droplets rising towards one

another into a teetering pile

before retreating back out to sea it

seems to violate the lord's natural

order

and augustine shies away from the

discomforting thought

what then if he could witness time laid

out before him

moving forward inexorably from one

moment

to the next the waves would crash

unceasingly on the shore advancing on

the bustling town until it reduced his

home to little more than a heap of

rubble and sand

as his quill drips ink onto the

parchment augustine's mind

wanders to see time itself advancing

ruining all in its path spreading its

relentless chaos

the present world of man crumbles to

meaningless piles

the thriving natural world eventually

decays to nothing more than dust in the

wind

and in the sky stars wink out one by one

until there is nothing left by which to

measure the passing moments

with nothing more for time to devour

would this finally be the end of the

voracious beast itself

what then is time if not the inevitable

march of disorder the inevitable

destruction of god's structured universe

into nothing more

than an eternal pile of sand

shaking himself from the darkness of his

waking dream augustine finds it truly is

darkening outside

with the last glimmers of the setting

sun he breathes deeply

and scratches out his final words for

the day

what then is time

but had augustine really been able to

see into the future

and probe the minds of modern scholars

he would have seen that his dark

imaginings

were not only accurate but substantiated

by the highest theoretical physics and

cosmology

the hungry beast of time powered by

ever-growing entropy

is unstoppable and relentless it is

driven not by some demon bent on

destruction but by the unassailable

forces of mathematics

that have gripped the cosmos from its

first moments to its inevitable end

this entropy bound up in the mathematics

of particles and energy powers the arrow

of time

forcing our eyes forward into a future

that is unavoidable as it

is disturbing and the past that is

forever

just out of reach

[Music]

some one and a half millennia after

saint augustine found his words lacking

on the subject of time the industrial

english city of manchester

was preparing to manipulate it in the

early 19th century

timekeeping clocks were calibrated

against local sundials

giving rise to times that could differ

by as much as 30 minutes

between the west and east coasts of

england

but with the advent of the industrial

revolution and the spread of the railway

network

the country suddenly needed a unified

system

now the difference of a few minutes

between london and other stations on the

network could mean passengers missing

their trains or even

collisions on intersecting tracks and so

it was decided that for the first time

in history

time itself would be changed

in january 1846 the residents of

manchester

collectively traveled through time

jumping 13 minutes

in an instant as the town's clocks were

adjusted to match the standard time set

by the royal observatory

in greenwich london

although time had been measured for

millennia following the passage of the

sun across the sky

this was the first time it had been

standardized

thanks to the incessant march of

industry but in truth

this so-called standard time is

arbitrary

little more than an imaginary structure

for our busy lives

the sun still sets in manchester 13

minutes later than in london

regardless of the time on the clocks

and yet the steam-powered locomotives of

the industrial revolution

did open our minds to the nature

of time in an altogether

unexpected way

some 20 years before england's clock

spent to the unstoppable force of the

railway

efforts to understand the heat engines

that powered these mechanical

juggernauts led french engineer and

physicist

sadie carneau to make a prophetic

observation

steam engines had been quickly adopted

across the rapidly industrializing world

bringing success and riches to all who

embraced them

but little work had been done to

understand how they really worked

this was the concern of carnot when in

1824

he penned his influential reflections on

the motive power

of fire his observation which may seem

simple and obvious now

was that heat always flows from a warmer

body

to a colder one this explains how a

fireplace can warm a cold room

why ice cubes melt when they're left in

the sun and why molten newly formed

planets solidify and cool in the cold

vacuum of space

it is an irreversible natural process

and it is this

that provides the motive power in all

heat engines

in this carno laid the foundation for

the theory

that was to become the second law of

thermodynamics

this law was developed over the

following century until it was brought

in line with our evolving physical

frameworks

now we recognize that not just heat

but all systems move in a single

direction

one that will decrease the free energy

of that system

today we describe this change in terms

of entropy

a mathematical way of measuring the

amount of disorder within a system

specifically it measures the number of