The Power of Doubt Science and Islam


The Power of Doubt

Jim Al-Khalili examines how the Islamic world has advanced science. He shows how Islamic scientific ideas permeated into the west in the 16th and 17th centuries.


Similar Content

Browse content similar to The Power of Doubt. Check below for episodes and series from the same categories and more!

Transcript


LineFromTo

The sun, the moon, the planets and stars

0:00:100:00:14

have always fired our imaginations and fuelled our mythologies.

0:00:140:00:19

And studying the heavens - astronomy - is surely the oldest scientific discipline there is.

0:00:190:00:25

What's really unexpected, I guess,

0:00:290:00:31

is that astronomy has repaid our interest in it over the centuries.

0:00:310:00:35

Time after time it's been the place where new ideas have emerged,

0:00:350:00:40

and it's often led the rest of sciences.

0:00:400:00:42

I'm a Professor of Physics at the University of Surrey,

0:00:470:00:51

and the ideas and theories of the great European scientists

0:00:510:00:54

like Galileo, Newton and Einstein lie at the heart of my work.

0:00:540:01:01

But there's another side to me.

0:01:010:01:02

I'm half-Iraqi, and I'm keen to investigate stories I'd heard as a schoolboy in Baghdad

0:01:020:01:09

of great astronomers from the medieval Islamic world

0:01:090:01:12

whose work shaped the discoveries of these later, Western scientists.

0:01:120:01:17

So, I'm going on a journey through Syria and Egypt, to the remote mountains in northern Iran,

0:01:190:01:25

to discover how the work of these Islamic astronomers had dramatic and far-reaching consequences.

0:01:250:01:32

There, I'll discover how they were the first to attack seemingly unshakeable Greek ideas

0:01:340:01:40

about how the heavenly bodies move around the earth.

0:01:400:01:44

It was Islam that paved the way

0:01:440:01:47

for one of the greatest upheavals in the history of science.

0:01:470:01:52

This is the University of Padua in northern Italy.

0:02:200:02:23

I'm here to see incontrovertible evidence

0:02:260:02:28

that one of the greatest breakthroughs in European science

0:02:280:02:32

links back to the earlier work by Islamic scholars.

0:02:320:02:36

Astronomer Dr Luisa Pigotti and I

0:02:410:02:43

are climbing up to the 18th century observatory.

0:02:430:02:47

At the top she promises to show me one of the most important books in scientific history.

0:02:490:02:54

So, what do we have here?

0:02:560:02:59

OK...

0:02:590:03:00

This is the second edition of De Revolutionibus.

0:03:000:03:04

Ah, Copernicus. Yes.

0:03:040:03:07

This is De Revolutionibus Orbium Celestium,

0:03:070:03:11

which was published in 1543 by the Polish astronomer Nicolaus Copernicus.

0:03:110:03:17

The significance of this book is enormous.

0:03:170:03:22

In it, Copernicus argues for the first time since Greek antiquity

0:03:220:03:26

that all the planets, including the Earth, go around the sun.

0:03:260:03:30

For thousands of years, everyone had believed a very different view -

0:03:340:03:39

that the earth is static and everything - including the stars,

0:03:390:03:44

sun and planets - move around it.

0:03:440:03:46

And here there are...all his system, OK...?

0:03:460:03:51

Oh, here we go.

0:03:510:03:53

Sol. The sun in the middle.

0:03:530:03:57

Yes.

0:03:570:04:00

Oh, yes, there's Terra...

0:04:000:04:01

With the moon. With the moon going around it. Yes.

0:04:010:04:05

This is an astonishing book.

0:04:050:04:07

And many historians credit it with starting the European scientific revolution.

0:04:070:04:14

The first, crucial step in a journey that led to modern physics.

0:04:140:04:19

Well, I agree.

0:04:210:04:23

But it does seem a bit odd that one doesn't hear much

0:04:230:04:25

about where Copernicus got his ideas and information.

0:04:250:04:29

The impression is that they came out of nowhere.

0:04:290:04:32

The beginning... The beginning is all in Arabic.

0:04:340:04:38

It certainly is a real revelation to me

0:04:380:04:41

that he explicitly mentions a 9th century Muslim

0:04:410:04:45

for providing him with a great deal of observational data -

0:04:450:04:49

an astronomer who lived in Damascus, called Al-Battani.

0:04:490:04:52

Like all the great scientists of the Islamic Empire,

0:04:540:04:57

Al-Battani lived in a culture without portraiture.

0:04:570:05:01

All we have are later impressions of what he might have looked like.

0:05:010:05:05

And here he mentions Hipparchus,

0:05:050:05:10

Ptolemy and so on.

0:05:100:05:13

And he started to mention what he called Machometi Aracenfis,

0:05:130:05:19

he means Al-Battani.

0:05:190:05:21

OK. And then this second book here... This second book is...

0:05:210:05:25

We can look at the beginning in Latin... I see...

0:05:250:05:29

Copernicus, in fact, made extensive use of Al-Battani's observations

0:05:290:05:33

of the positions of planets, the sun, the moon and stars.

0:05:330:05:37

He worked with Latin translations, similar to this one, of the Syrian astronomer's data.

0:05:370:05:43

Kitab Al-Zij Al-Battani.

0:05:430:05:45

So this is Al-Battani's zij, his book of star charts.

0:05:450:05:52

So it has the Arabic on one side and...

0:05:520:05:55

Yes. And then the Latin version.

0:05:550:05:58

That's convenient.

0:05:580:06:00

But certainly he had the data, the observational data, by Al-Battani.

0:06:020:06:07

And Copernicus' book is full of clues

0:06:100:06:12

that hints at other past sources.

0:06:120:06:14

And though Al-Battani is the only Islamic astronomer Copernicus actually names,

0:06:170:06:22

recent detective work has uncovered clues that Copernicus based many of his ideas

0:06:220:06:28

on the work of other Islamic scholars.

0:06:280:06:31

The clearest example is Copernicus's use of a mathematical idea

0:06:310:06:36

devised by the 13th century Islamic astronomer Al-Tusi, called the Tusi Couple.

0:06:360:06:42

Back in England, I compared a copy of Al-Tusi's Tadhkirah Al-Hay Fi'ilm Sl-hay'ah

0:06:460:06:52

with another edition of Copernicus' Revolutionibus.

0:06:520:06:57

In it there's a diagram of the Tusi Couple -

0:06:570:06:59

and there's an almost identical diagram in Copernicus's book.

0:06:590:07:05

Even down to the letters that mark the points on the circles.

0:07:050:07:09

So, in Al-Tusi there is the Arabic Alif, which is A.

0:07:090:07:13

There's the Baa, which is B. Gheem, over here, is the G.

0:07:130:07:17

And the Dal at the centre, D.

0:07:170:07:21

It's a remarkable similarity.

0:07:210:07:24

Now this might just be coincidence, but it's pretty compelling evidence.

0:07:240:07:29

In fact, I truly believe that Copernicus

0:07:290:07:33

must have been aware of Al-Tusi's work and other Islamic astronomers.

0:07:330:07:38

Further detective work also shows that Copernicus used mathematical ideas for planetary motion

0:07:420:07:48

that are remarkably similar to ones developed by another Islamic astronomer,

0:07:480:07:53

a 14th century Syrian called Ibn Al-Shatir.

0:07:530:07:57

For some historians this cannot be coincidence.

0:07:570:08:01

Copernicus, to me, I have no proof, I don't have a smoking gun.

0:08:010:08:06

But to me it looked like, and by analysing his own words,

0:08:060:08:11

it looks like he was working from diagrams.

0:08:110:08:14

Somebody gave him a geometric diagram of what was done by Ibn Shatir to solve the problem of the moon,

0:08:140:08:21

for example, to solve the problem of the upper planets,

0:08:210:08:25

to solve the problem of the movement of Mercury, he had diagrams, and he was genius enough

0:08:250:08:29

to be able to figure out from the diagrams what was the underlying theory behind those diagrams.

0:08:290:08:35

So, far from emerging from nowhere,

0:08:390:08:42

it seems Copernicus' work would be better described as

0:08:420:08:46

the culmination of the preceding 500 years of Islamic astronomy.

0:08:460:08:51

I wanted to investigate this story,

0:08:510:08:54

find out more about those astronomers and their ideas.

0:08:540:08:57

But before that, I wanted to investigate an even deeper question.

0:08:590:09:03

What actually motivated medieval Islamic scholars' interest in astronomy?

0:09:030:09:09

This is the Umayyad Mosque

0:09:230:09:25

in the heart of the Syrian capital, Damascus,

0:09:250:09:28

and is one of the oldest in the world.

0:09:280:09:30

And I'm here on a kind of treasure hunt.

0:09:350:09:38

Well, it says says in the books

0:09:380:09:40

that there is a sundial on the top of the Arus Minaret,

0:09:400:09:44

the bright minaret over there.

0:09:440:09:46

So we'll see whether it is there or not...

0:09:460:09:48

This is Dr Rim Turkmani,

0:09:500:09:52

an astrophysicist and medieval astronomy expert

0:09:520:09:55

from Imperial College London.

0:09:550:09:57

And we're looking for one of the most accurate sundials made in the medieval world.

0:09:570:10:02

And equally exciting for me

0:10:020:10:04

is the fact that it was made by one of the Islamic astronomers

0:10:040:10:08

who had so heavily influenced Copernicus, Ibn Shatir.

0:10:080:10:12

Let's see...

0:10:140:10:16

Officials in the mosque claim that the sundial was removed in the 19th century,

0:10:190:10:25

but Rim's research suggests that an exact replica might still exist,

0:10:250:10:30

high in one of the minarets, hidden from view.

0:10:300:10:33

It's not quite the lost of arc of the covenant,

0:10:330:10:36

but the idea of discovering a 150-year-old artefact is still quite something.

0:10:360:10:40

Would you recognise anything if you...? Yeah, I need to look out of the other window, I'm sorry.

0:10:420:10:46

Nope. No, it is further up...

0:10:490:10:51

Yeah.

0:10:510:10:53

Marking time accurately is essential to Islam.

0:10:530:10:57

The Qur'an requires the faithful to pray five times a day,

0:10:590:11:04

at five very precise times.

0:11:040:11:06

At the exact moment of dawn, when the sun is overhead,

0:11:100:11:14

in the afternoon, at sunset,

0:11:140:11:17

and then again at the moment of nightfall.

0:11:170:11:21

So for early Islam, an accurate sundial was an extremely important fixture in many mosques.

0:11:210:11:28

That's it. That's it, I've found it! I've found it!

0:11:340:11:38

Here it is, that's it, look!

0:11:380:11:41

Just as described in the book. Wow! It's hidden by the pillar.

0:11:410:11:46

Yeah. No wonder they didn't know that it exists here.

0:11:460:11:48

It's all covered with the pigeons' filth.

0:11:480:11:52

Pigeon crap. Yeah. Try that. Oh, great, thank you.

0:11:520:11:56

Now, this consists of three sundials.

0:12:010:12:05

The main, big one.

0:12:050:12:06

And there's the northern one and the southern one.

0:12:060:12:10

There is a line here for Dhuhr,

0:12:100:12:12

the midday prayer, and there is one for the afternoon prayer.

0:12:120:12:15

Ibn Al-Shatir had calculated the arrangement of these lines

0:12:170:12:21

so that the sun dial remains accurate all through the year,

0:12:210:12:26

even though length of the days change.

0:12:260:12:28

They will have a timekeeper.

0:12:280:12:31

You know, it's a very important job.

0:12:310:12:33

Yeah. So he would sit here watching the shadow... Exactly.

0:12:330:12:36

And the precise moment for prayer, he'd signal to the muezzin to start the call for prayer. Exactly.

0:12:360:12:42

Ibn Al-Shatir's sundial, accurate to within minutes,

0:12:550:12:59

really showed me how Islam required its scholars

0:12:590:13:02

to make meticulously accurate observations of heavenly bodies.

0:13:020:13:06

And I began to understand why Copernicus was so impressed by the work of his Islamic predecessors.

0:13:170:13:23

They really brought standards of accuracy and precision to astronomy that were unheard of before.

0:13:240:13:30

They had calculated the size of the Earth to within 1 per cent.

0:13:320:13:36

And created trigonometric tables accurate to three decimal places.

0:13:360:13:41

And when I met up with Rim Turkmani again on Mount Qassioun outside Damascus,

0:13:440:13:49

I was to hear about the Islamic astronomer who personified accurate observation,

0:13:490:13:55

the man whose astronomical tables and measurements

0:13:550:13:58

Copernicus explicitly makes reference to - Al-Battani.

0:13:580:14:02

Born in 858 in southern Turkey,

0:14:030:14:06

Al-Battani made accurate astronomical measurement a personal obsession.

0:14:060:14:12

And the story goes that Al-Battani used to observe on this mountain here in this observatory...

0:14:120:14:20

Over 40 years from 877 - both here and in the town of Raqqah -

0:14:200:14:26

Al-Battani's great project was to work to out,

0:14:260:14:29

as accurately as possible, the length of the year.

0:14:290:14:33

This is a copy of the original manuscript.

0:14:330:14:37

OK. I'll show you the chapter at which he explains the length of the year, OK?

0:14:370:14:42

Mm-hmm. The Chapter 27.

0:14:420:14:45

So he first started by citing the ancient values of the Egyptians and the Babylonians.

0:14:450:14:51

And he gives their length of the year.

0:14:510:14:52

Their estimate of the year

0:14:550:14:57

was 365 days, 6 hours and just over 10 minutes.

0:14:570:15:03

To improve on this, Al-Battani used his ingenuity and a device like this, an armillary sphere.

0:15:030:15:09

He used it to measure how the length of shadows varied over the course of the year.

0:15:090:15:14

With this information he worked out the precise day

0:15:140:15:17

on which it's both light and dark for exactly the same time -

0:15:170:15:21

the so-called equinox.

0:15:210:15:23

And he repeated his measurements over the course of 40 years.

0:15:230:15:27

Now here's the clever bit.

0:15:270:15:29

He then examined a Greek text that was written 700 years earlier,

0:15:290:15:33

and discovered the precise day on which its author had also measured the equinox.

0:15:330:15:38

He now had two vital pieces of data -

0:15:380:15:40

the number of days between the two observations, and the number of years.

0:15:400:15:45

He divided the first number by the second to arrive at an astonishing result -

0:15:450:15:53

a year is 365 days, five hours, 46 minutes and 24 seconds.

0:15:530:15:59

He gets the new number, which was only two minutes off the modern observations.

0:15:590:16:04

The length of the year to an accuracy of just two minutes.

0:16:040:16:08

Exactly, the one he calculated.

0:16:080:16:09

What's astonishing about the accuracy of Al-Battani's measurements

0:16:150:16:20

is that he had no telescope.

0:16:200:16:21

He used an armillary arm, his naked eye, and devices like this - an astrolabe.

0:16:240:16:29

So you move the pointer, and you move this disc with it, to point towards the North Star.

0:16:290:16:34

And then these small pointers here,

0:16:340:16:37

they will give you the location of the rest of the stars and the planets.

0:16:370:16:41

Despite this, among his many other observations

0:16:430:16:46

is an incredibly accurate figure for the Earth's tilt,

0:16:460:16:51

of just under 24 degrees - about a half a degree from the figure we now know it to be.

0:16:510:16:57

And he didn't stop there.

0:16:590:17:01

He measured variations in the sun's diameter with such accuracy

0:17:010:17:06

that it lead him to astonishing conclusion.

0:17:060:17:10

This distance, the furthest point the sun reaches from the Earth during the year,

0:17:100:17:15

known as its apogee, actually changes from one year to another.

0:17:150:17:19

Also, his tables showing the position of the sun and moon,

0:17:220:17:26

which is what Copernicus refers to some 600 years later,

0:17:260:17:31

set a new standard in precision and accuracy.

0:17:310:17:34

So, Al-Battani and his fellow Islamic astronomers were clearly good observers.

0:17:370:17:42

But so what, you might ask.

0:17:440:17:47

Well, the answer is that their observations began to suggest to them

0:17:470:17:51

that the prevailing Greek theory that described how everything

0:17:510:17:56

in the heavens revolved around the Earth had some serious flaws.

0:17:560:18:00

This Greek tradition, which had been unquestioned for over 700 years,

0:18:030:18:09

was based primarily on the work of one of the greatest astronomers of the ancient world.

0:18:090:18:15

Claudius Ptolemaeus, or Ptolemy,

0:18:190:18:22

was a Greek astronomer based in Alexandria in the 2nd century AD.

0:18:220:18:27

He wrote one of the greatest texts in astronomy, the Alamgest,

0:18:270:18:31

which was basically a distillation of all the Greek knowledge on the celestial world.

0:18:310:18:37

Ptolemy believed that the sun, the moon, the planets and the stars

0:18:370:18:42

all sat on crystal spheres that rotated around the Earth.

0:18:420:18:46

So, the moon sits on the innermost sphere,

0:18:460:18:49

followed by the sun and the planets,

0:18:490:18:52

and finally, a patchwork of stars on the outermost sphere.

0:18:520:18:56

So, we human beings sit at the very centre of the universe,

0:18:560:19:00

with the rest of the universe rotating around us.

0:19:000:19:03

But, as Ptolemy himself realised,

0:19:030:19:06

there's a problem with trying to describe the heavens

0:19:060:19:09

as a place of mathematically-idealised perfect spheres.

0:19:090:19:14

And that is that the planets don't really play ball.

0:19:150:19:19

As they move across the night sky, they change speed,

0:19:190:19:23

appear to get bigger and smaller and even go back on themselves.

0:19:230:19:28

Ptolemy tried to explain this away by arguing that the planets sat on small spheres called epicycles,

0:19:280:19:35

which rotated around a bigger sphere called a deferent.

0:19:350:19:39

This explained why they might look as though they were changing size

0:19:420:19:45

and why they sometimes even changed direction.

0:19:450:19:47

Unfortunately, that still didn't fit all the facts.

0:19:490:19:53

It didn't easily explain why the planets appear to speed up and slow down.

0:19:530:19:58

So rather desperately, Ptolemy fudged his model further

0:19:580:20:03

by moving the Earth away from the centre of the deferent,

0:20:030:20:08

and having the deferent rotate around an arbitrary point in space - the equant.

0:20:080:20:14

But now the works of astronomers like Al-Battani

0:20:140:20:18

started to strain Ptolemy's ideas to breaking point.

0:20:180:20:22

Their careful observations began to suggest that even with Ptolemy's unwieldy equants and deferents,

0:20:220:20:30

the actual behaviour of the heavens didn't fit the data.

0:20:300:20:34

So, what do you do if you were an astronomer living in Baghdad

0:20:340:20:38

and you have all these results on your table?

0:20:380:20:41

The very first requirement is to say,

0:20:410:20:44

this Greek tradition is not as trustworthy as it is advertised to be.

0:20:440:20:51

And now of course they begin to say,

0:20:510:20:53

"If the fundamental values of the astronomical measurements of the Greeks,

0:20:530:20:59

"which we could double-check and we found them to be in error, what else is in error?"

0:20:590:21:04

They began to question now the more basic foundational

0:21:040:21:10

astronomical, cosmological foundations of the Greek tradition.

0:21:100:21:16

And question they did.

0:21:160:21:18

What's absolutely striking about the writings of Islamic scholars by the 9th century

0:21:230:21:30

is the increasing use of the word "shukuk", which in English means "doubts".

0:21:300:21:36

They showed it's sometimes necessary to doubt an idea that everyone around you believes unquestioningly.

0:21:360:21:42

Islamic doubting of Greek astronomy

0:21:420:21:44

began the slow process of undermining the notion

0:21:440:21:47

that the Earth is at the centre of the universe.

0:21:470:21:50

To doubt takes great courage and imagination,

0:21:500:21:54

but if the great dialogue between Islamic and European astronomers shows anything,

0:21:540:22:00

it's that doubt, or shukuk, is the engine that drives science forward.

0:22:000:22:04

One of the first great shukuk scientists was called Ibn Al-Haytham.

0:22:110:22:17

He was born in the Iraqi city of Basra in 965AD.

0:22:170:22:23

And was among the first to argue passionately

0:22:230:22:27

that scientific ideas are only valid

0:22:270:22:29

if they're mathematically consistent and reflect reality.

0:22:290:22:34

And when he applied his fierce, rigorous intelligence to Greek astronomy,

0:22:340:22:39

he immediately spotted that there was a fundamental contradiction at its heart.

0:22:390:22:45

On the one hand, Greek cosmology argued that everything in the heavens revolves around the Earth.

0:22:450:22:52

On the other hand, Ptolemy, in his Almagest,

0:22:520:22:55

argued that if you want to mathematically predict how the sun and planets move,

0:22:550:23:01

you have to pretend that they go around an arbitrary point in space - the so-called equant.

0:23:010:23:06

This is clearly a contradiction -

0:23:080:23:10

the heavens can't both go around the Earth and not go around it at the same time.

0:23:100:23:16

Ibn Al-Haytham hated this nonsensical contradiction.

0:23:160:23:20

In the early 11th century, he wrote a paper, Al-Shukuk Ala-Batlamyus, or Doubts On Ptolemy.

0:23:220:23:29

In it, he writes with barely contained frustration,

0:23:290:23:33

"Ptolemy assumes an arrangement that cannot exist."

0:23:330:23:37

Ibn Al-Haytham says, "That is a total absurdity. We cannot accept that."

0:23:370:23:42

And furthermore he says, "It's not a slip of the tongue.

0:23:420:23:46

"Ptolemy knew that it was absurd."

0:23:460:23:48

And he shows us where Ptolemy himself was embarrassed by having to introduce it.

0:23:480:23:52

So, he says there is a fundamental reasoning problem,

0:23:520:23:56

meaning that the Greeks knew, that Ptolemy knew he was making a mistake,

0:23:560:24:02

but he couldn't do any better,

0:24:020:24:04

and hints, now the challenge is to do much better and hints to be able to fix this...

0:24:040:24:09

That, in my explanation,

0:24:090:24:12

begins to be the programme of research for all astronomers to come.

0:24:120:24:16

In order to achieve that project, you had to be convinced -

0:24:160:24:22

you had to be convinced -

0:24:220:24:24

that it was possible to make high-precision mathematical models

0:24:240:24:30

of the way in which planets and stars move,

0:24:300:24:34

that would really capture how they are in the heavens.

0:24:340:24:39

Ibn Al-Haytham, in effect,

0:24:470:24:48

laid down the challenge for all astronomers who followed,

0:24:480:24:52

which was to come up with an explanation for how the heavens move

0:24:520:24:57

that is both mathematically consistent, and agrees with what we observe.

0:24:570:25:01

The final answer to this would come from far-away Europe, with Copernicus and others.

0:25:050:25:10

But the next and crucial breakthrough came somewhat closer.

0:25:100:25:14

The top of this mountain in northern Iran

0:25:330:25:36

was the adopted home of the man who was the next of Copernicus' Islamic influences,

0:25:360:25:43

Nasir Al-Din Al-Tusi.

0:25:430:25:44

He would succeed in rewriting Ptolemy's theory,

0:25:440:25:48

which would ultimately lead to the overthrow of the geocentric view of the universe,

0:25:480:25:55

and so the birth of the modern scientific age.

0:25:550:25:58

This is the remote castle of Alamut,

0:26:020:26:07

Al-Tusi's adopted home.

0:26:070:26:10

For many years, it was the home of a Muslim sect called the Ismailis.

0:26:100:26:14

It's a lovely secluded spot,

0:26:170:26:19

and it was the centre of the Ismaili movement.

0:26:190:26:23

It's not surprising that Al-Tusi would find a home here.

0:26:230:26:27

And it wasn't just him.

0:26:270:26:29

Many other scholars were gathered here

0:26:290:26:31

and there seems to have been a library -

0:26:310:26:33

it was a centre for learning as well as a military stronghold.

0:26:330:26:37

Here, this is the main gate, northern gate of the upper castle...

0:26:450:26:52

A new archaeological dig is now revealing under the castle, hewn into the living rock,

0:26:540:26:59

a warren of rooms and studies, a mosque and living quarters

0:26:590:27:04

for this extraordinary community of soldiers and scientists.

0:27:040:27:09

This is the court of mosque,

0:27:090:27:12

or centre of headquarters of castle.

0:27:120:27:18

And it was within these cramped conditions

0:27:210:27:25

that Al-Tusi started his masterwork of the shukuk,

0:27:250:27:29

or the doubts - the Tadhkirah.

0:27:290:27:31

In it he finds an answer to Ibn Al-Haytham's first challenge -

0:27:310:27:36

how to eliminate Ptolemy's equant.

0:27:360:27:39

Instead of a sphere rotating around an arbitrary point in space,

0:27:420:27:47

Al-Tusi devised a series of two nested circles,

0:27:470:27:50

which rotate around each other in such a way that they eliminate the equant.

0:27:500:27:56

The nested circles became known as a Tusi Couple.

0:27:580:28:03

This is the mathematical system that finds it way into Copernicus' work some 300 years later.

0:28:050:28:12

Having found a solution to the equant problem,

0:28:170:28:20

Al-Tusi now wanted to complete the task Ibn Al-Haytham had started 200 years earlier -

0:28:200:28:26

to find a consistent mathematical description of the movement of the celestial bodies.

0:28:260:28:33

But to do that he needed better data,

0:28:330:28:36

which meant bigger and better equipment than he was ever going to find here at Alamut.

0:28:360:28:40

And then something happened which changed Al-Tusi's life forever - the Mongols.

0:28:400:28:48

Streaming in from the East, an army of Mongols led by Hulagu Khan

0:28:560:29:02

marched into Iran, crushing everything before them.

0:29:020:29:05

By 1255, they had reached the foothills of Alamut, intent on its destruction.

0:29:080:29:15

Then, in a brilliant piece of diplomacy,

0:29:180:29:20

Al-Tusi managed to both save his own skin

0:29:200:29:24

and satisfy his scientific ambition.

0:29:240:29:27

He visited the Mongol leader, and played on his deep astrological superstition.

0:29:280:29:34

Convincing him he could tell the future if only he had new equipment, Al-Tusi persuaded the Khan

0:29:370:29:43

to make him his head scientist and to build him, just a few hundred miles away,

0:29:430:29:48

perched on a hilltop where the air was clear,

0:29:480:29:51

the largest observatory the world had ever seen.

0:29:510:29:55

This is all that remains of the Maragheh Observatory.

0:30:040:30:10

The main instrument is hidden is under this protective dome.

0:30:100:30:13

Al-Tusi's new astronomical centre was based around a single large building.

0:30:160:30:22

Inside was an enormous metal arc,

0:30:230:30:27

an armillary arm, ten metres across.

0:30:270:30:30

On its circumference were marked angles in degrees and minutes.

0:30:320:30:37

The scientists would line up the celestial object under study

0:30:370:30:41

with a central point on the arc, and then make a reading from the markings on the arc,

0:30:410:30:47

giving them the definitive, accurate position of the object in the sky.

0:30:470:30:51

The building was also surrounded by smaller astronomical equipment,

0:30:550:30:59

libraries, offices and accommodation.

0:30:590:31:02

The observatory even had its own dedicated mosque.

0:31:040:31:08

I suppose it is a little disappointing that there's not much left of the place now,

0:31:150:31:20

so you really have to imagine what it must have been like back in its heyday.

0:31:200:31:24

After all, what Al-Tusi built here

0:31:240:31:27

was nothing less than the world's greatest observatory for 300 years.

0:31:270:31:32

And like any modern-day international research institute,

0:31:320:31:37

he brought together the world's greatest astronomers from as far away as Morocco and even China.

0:31:370:31:43

I mean, it really must have been a great buzzing atmosphere to work here.

0:31:430:31:48

With his new observatory and world-class team,

0:31:550:31:58

Al-Tusi was now ready to fulfil Ibn Al-Haytham's dream -

0:31:580:32:02

to try to make Ptolemy's model scientifically rigorous.

0:32:020:32:07

First they attacked the mathematics.

0:32:070:32:11

As well as the Tusi Couple, they invented other systems of planetary movement.

0:32:110:32:16

And with these new systems, they were able to calculate

0:32:160:32:19

mathematically-consistent models for many of the celestial bodies.

0:32:190:32:24

Mercury, Venus, Mars, Jupiter, Saturn and the sun and moon.

0:32:240:32:30

Al-Tusi and the astronomers he brought together created what became known as the Maragheh revolution,

0:32:380:32:45

which was a complete paradigm shift in astronomy, overthrowing the old Ptolemaic view.

0:32:450:32:51

What Islamic scholars and astronomers like Al-Tusi do

0:32:510:32:56

is to organise and make sense of mathematical astronomy

0:32:560:33:02

at a level of unprecedented accuracy,

0:33:020:33:05

using instruments more precise than had been built before,

0:33:050:33:09

over longer timescales, with predictions

0:33:090:33:13

of the positions of planets and stars that no-one had previously reached -

0:33:130:33:17

that at Maragheh or at Alamut

0:33:170:33:21

we see, I think, genuine revolutions in the level, scale and intensity of mathematical astronomy.

0:33:210:33:28

But there was still a problem.

0:33:350:33:37

The new models were mathematically coherent and they dispensed with Ptolemy's unwieldy equant.

0:33:370:33:44

But they still firmly placed the earth at the centre of the universe,

0:33:440:33:49

and that inevitably meant that their descriptions of the heavens were intricate and complicated,

0:33:490:33:55

with epicycles, deferents and couples - it was like some great cosmic gearbox.

0:33:550:34:01

It would require a huge leap of imagination to make the next step in our story.

0:34:080:34:13

And that next step would take place 2,000 miles from where I am now.

0:34:130:34:18

In my view, the last phase of the Maragheh revolution took place

0:34:330:34:37

not in Iran or anywhere in the Islamic Empire, but here in Northern Italy.

0:34:370:34:43

Based on the work of Muslim scholars, places like

0:34:430:34:46

the University of Padua were already starting a new scientific movement -

0:34:460:34:51

the Renaissance.

0:34:510:34:52

Back in Padua, where I began my journey,

0:34:560:34:59

I now understand why Islamic astronomers were so important to Copernicus.

0:34:590:35:05

They gave him his motivation.

0:35:050:35:07

He's the first European to share Ibn Al-Haytham's deep aversion to Ptolemy's cosmology.

0:35:080:35:15

And that's what makes Copernicus not the first great astronomer

0:35:150:35:19

of a new European tradition, but the last of the Islamic tradition.

0:35:190:35:23

As we've seen, many of the complex mathematical models Copernicus uses in his new heliocentric model,

0:35:270:35:34

like the Tusi Couple, are copied from Islamic astronomers.

0:35:340:35:38

But more importantly, it's Copernicus's deep desire

0:35:380:35:42

to bring mathematical consistency to cosmology that he really owes to his Islamic predecessors.

0:35:420:35:49

Copernicus' ideas set in motion a train of scientific revelations

0:35:510:35:57

that would eventually lead to Isaac Newton and the discovery of gravity.

0:35:570:36:02

In Newton's hands, Ibn Al-Haytham's dream of an astronomy with rigorous

0:36:020:36:07

and coherent mathematics which agrees with experimental observation finally took place.

0:36:070:36:13

But this begs two crucial questions -

0:36:230:36:26

why was the great astronomical project which Islamic astronomers began

0:36:260:36:30

completed in Europe and not in the Middle East?

0:36:300:36:35

And how did knowledge of Islamic science get to Europe in the first place?

0:36:350:36:39

The answers to these questions lie in one of the most beautiful cities on earth,

0:36:450:36:49

the Queen of the Adriatic - Venice.

0:36:490:36:53

Venice was founded on a swamp off the coast of Italy,

0:37:080:37:13

and felt itself separate from Europe, and not bound by its laws and traditions.

0:37:130:37:18

And as Shakespeare famously pointed out, the two most important aspects

0:37:180:37:22

of Venice were its merchants and its longstanding links with the Arabs, or Moors.

0:37:220:37:30

It was a rich and complicated relationship, sometimes based on piracy and theft.

0:37:300:37:37

The story goes that in 828,

0:37:370:37:40

two Venetian merchants stole the bones of a famous Christian saint

0:37:400:37:44

from Venice's rival city across the water, Alexandria.

0:37:440:37:47

The bones belonged to St Mark the Evangelist, and they brought them back to here to St Mark's Square.

0:37:470:37:53

But without doubt, trade with the East brought to Venice great wealth

0:37:590:38:04

and an exchange of ideas, customs and people, as Venice expert Vera Costantini showed me.

0:38:040:38:11

So this is called the Campo dei Mori because as you can see

0:38:110:38:14

at the corners, there are statues of what were called Moors.

0:38:140:38:21

There's another... Yeah, there's another one with a turban.

0:38:210:38:24

The beard was recommended to many Venetian merchants even when they went to the East.

0:38:240:38:29

There were manuals written for Venetian merchants.

0:38:290:38:33

How to blend in?

0:38:330:38:35

Yes. How to be respected in the East.

0:38:350:38:38

As Venetians traded more and more with their Muslim neighbours,

0:38:410:38:45

the influence of Islam was more strongly felt.

0:38:450:38:49

Arabic coffee culture became hugely popular.

0:38:510:38:54

As did Islamic styles of architecture,

0:38:570:38:59

with their characteristic arches and decorations.

0:38:590:39:02

So, the next thing I want to show you is the Palace of the Camel.

0:39:060:39:09

When Venetians traded in the East, the unit of measurement,

0:39:090:39:15

of a load that could be loaded on a dromedary was called a carrico.

0:39:150:39:21

And it was exactly the same unit of measurement

0:39:210:39:24

they had in the East. And it was called yook.

0:39:240:39:28

So it's not coincidence that

0:39:280:39:30

they actually imported that unit of weight.

0:39:300:39:33

Yes, of measurement, of weight.

0:39:330:39:36

And with the Arabic trade came the Arabic books.

0:39:390:39:44

The great 9th century Arabic text on algebra appeared in Latin in the 12th century.

0:39:440:39:50

The same century saw the arrival of Arabic astronomical tables,

0:39:500:39:55

and in the 15th century, the famous canon of medicine was first published in the West.

0:39:550:40:01

And this influx of learning seems to coincide with a great historical shift.

0:40:100:40:15

The engine of science begins to move west, from the Islamic world to Europe.

0:40:150:40:21

That's where the great breakthroughs from the 1500s would mainly take place.

0:40:210:40:26

I encountered an astonishing and very tangible symbol of this shift, and a really surprising clue

0:40:360:40:43

as to why it happened, thanks to Professor Angela Nuovo, from the University of Udine.

0:40:430:40:49

20 years ago, in this library on one of the islands of Venice,

0:40:530:40:57

Angela discovered the only surviving version of a 500-year-old book.

0:40:570:41:03

And what did it feel like? This is a big, big discovery!

0:41:030:41:07

Yes, yes. It was a great emotion.

0:41:070:41:10

I remember it was July, very hot, like today - even hotter.

0:41:100:41:13

And I felt cold.

0:41:130:41:15

Wow!

0:41:150:41:17

Yes, it was a great emotion.

0:41:170:41:19

What she found was the very first printed copy of Islam's holy book, the Qur'an.

0:41:220:41:29

This is the first time she has seen her Qur'an since she discovered it 20 years ago.

0:41:380:41:45

But it struck me as strange that world's first printed Qur'an

0:41:450:41:49

was produced in Venice, and not in the Islamic world.

0:41:490:41:53

And it's obvious at first glance that it was printed by people who didn't speak Arabic very well.

0:41:530:42:00

HE READS ALOUD

0:42:000:42:04

What strikes me is that

0:42:080:42:10

it's written in what I would regard as almost childlike handwriting.

0:42:100:42:17

It's clumsy.

0:42:170:42:19

Yeah. Well, it's the first attempt to reproduce the handwriting in moveable types,

0:42:190:42:26

and as you know, the language has an enormous amount of different sorts.

0:42:260:42:31

Every letter changes according to ligatures and the position.

0:42:310:42:36

Of course, so it's difficult.

0:42:360:42:38

Yeah, the word meaning "for that",

0:42:380:42:41

the dash should be underneath the L, but it's above it, so it says the wrong thing.

0:42:410:42:49

Probably there were not people of mother language in the press.

0:42:490:42:56

So there were some errors in the text, which are of course sins.

0:42:560:43:01

Yes, of course, as the Qur'an, every Muslim believes it's the word of God, you can't change it.

0:43:010:43:08

So when you change it, it's a sin.

0:43:080:43:11

How was it first received when it was published?

0:43:110:43:14

Well, yes, the hypothesis is, and I think it's true,

0:43:140:43:18

that it was an enormous failure from the business point of view.

0:43:180:43:23

The Muslims didn't accept the printing press for centuries,

0:43:230:43:28

and probably the whole copies of this book were destroyed.

0:43:290:43:33

So we don't have any other copy.

0:43:330:43:36

Probably the only one that remained in the Western world is this book.

0:43:360:43:41

'I felt that the failure of this printed Qur'an to catch on in the Islamic world spoke volumes.'

0:43:410:43:48

800 years earlier, one reason for Islamic science's success

0:43:530:43:58

had been the precision of the Arabic language - with over 70 different ways

0:43:580:44:03

of writing its letters and many extra symbols to define pronunciation and meaning,

0:44:030:44:08

it allowed scholars of many different lands to communicate in a single, common language.

0:44:080:44:14

Now, with the arrival of the printing press,

0:44:180:44:21

scientific ideas should have been able to travel even more freely.

0:44:210:44:26

In the West, books printed in Latin accelerated its scientific renaissance.

0:44:260:44:32

But because of its symbols and extra letters,

0:44:320:44:37

Arabic was much harder to set into type than Latin,

0:44:370:44:40

and so a similar acceleration in the Islamic world failed to materialize.

0:44:400:44:45

I believe this rejection of the new technology - the printing press -

0:44:460:44:52

marks the moment in history when Arabic science undergoes a seismic shift.

0:44:520:44:57

Europe has embraced Greek and Arabic knowledge and the new technology.

0:44:570:45:02

And Galileo and his ilk are poised at the cusp of the Renaissance.

0:45:020:45:07

It has been a turning point both in the history

0:45:070:45:11

of the Venetian printing press, who used to be extremely powerful.

0:45:110:45:15

It's the limit of expansion, let's say.

0:45:150:45:18

And in the history of the general and cultural relationship between the East and the West.

0:45:180:45:24

As acceptation of printing would have meant

0:45:240:45:28

the acceptation of the first important technology,

0:45:280:45:31

so the two histories started to differ very much.

0:45:310:45:37

This initial rejection of printing was one of the many reasons

0:45:410:45:45

that caused science in the Islamic world to fall behind the West.

0:45:450:45:50

It coincided with a host of global changes, all of which affected the way science developed.

0:45:500:45:58

The first and most obvious reason for the slowdown in Islamic science

0:46:060:46:09

is that the Islamic empire itself

0:46:090:46:13

falls into decline from the mid-1200s.

0:46:130:46:17

One reason for this is that it's under attack from all sides.

0:46:170:46:21

From the east are the Mongols.

0:46:210:46:23

In 1258, they invaded the capital, Baghdad, and it's said that

0:46:280:46:32

the waters of the Tigris and Euphrates rivers

0:46:320:46:35

ran black for days with the ink of the books they'd destroyed.

0:46:350:46:40

But trouble was also brewing in the far west of the empire.

0:46:400:46:44

Islamic Spain, already fragmented into separate city states, now faced a new threat -

0:46:480:46:55

a united and determined onslaught from the Christian north.

0:46:550:47:00

The re-conquest, as it was called, raged for hundreds of years,

0:47:030:47:07

but culminated in the 15th century, when Ferdinand II and Isabella

0:47:070:47:12

led an army which forced the last of the Muslims in Grenada to surrender in 1492.

0:47:120:47:19

The Christians were intent

0:47:190:47:21

on removing every last vestige of Islamic civilization and culture from Spain.

0:47:210:47:26

In 1499, they ordered the burning in this square in Granada

0:47:260:47:31

of all Arabic texts from Granada's libraries...

0:47:310:47:34

except for a small number of medical texts.

0:47:340:47:38

Within about 100 years, every Muslim in Spain

0:47:380:47:42

had either been put to the sword, burnt at the stake or banished.

0:47:420:47:46

And Christians from the east of Europe were intent on reclaiming the Holy Land -

0:47:490:47:56

the Crusades.

0:47:560:47:57

Bent on carving out a wholly Christian Levant

0:47:590:48:03

and claiming the holy city of Jerusalem,

0:48:030:48:05

the Crusaders launched a massive attack on Northern Syria.

0:48:050:48:09

They quickly captured this castle and turned it into one of their strongholds.

0:48:090:48:14

Then, with ruthless and missionary zeal, they marched on Jerusalem.

0:48:140:48:19

And as the empire fought with its neighbours, it collapsed into warring fiefdoms.

0:48:190:48:26

The Mamluks, slaves who originally belonged to the state of Egypt,

0:48:260:48:30

became its leaders.

0:48:300:48:32

The Bourbon Almohads ruled Morocco and Spain in the 13th century.

0:48:320:48:38

And the north of Syria and Iraq splintered into a series of city states.

0:48:380:48:43

But for many historians of science, the biggest single reason

0:48:460:48:50

for the decline in Islamic science was a rather famous event that took place in 1492.

0:48:500:48:56

That year, the entire political geography of the world

0:48:560:49:01

changed dramatically when a certain Christopher Columbus arrived in the Americas.

0:49:010:49:08

I explain it with the phenomena of

0:49:080:49:11

the discovery of the New World in 1492.

0:49:110:49:14

The immediate result is that you got immense amounts of gold and silver

0:49:140:49:18

coming to the royal houses of Europe at the time and all the adventurers,

0:49:180:49:23

empires and royal houses of the time were setting colonies all over the world.

0:49:230:49:27

And science always follows the money.

0:49:270:49:31

As the 16th and 17th centuries came and went, that money,

0:49:310:49:36

power and hence scientific will, moved through Italy, Spain and onto Britain.

0:49:360:49:42

By the 17th century, England, sitting at the centre

0:49:420:49:45

of the lucrative Atlantic trade route, could afford big science.

0:49:450:49:50

And that ultimately explains why the greatest book in world science,

0:49:500:49:54

Sir Isaac Newton's Principia Mathematica,

0:49:540:49:57

the book that ultimately explains the motion of the sun, moon and planets,

0:49:570:50:01

was not published in Baghdad, but in London.

0:50:010:50:06

It was necessary for him to have data of astonishing accuracy

0:50:060:50:11

gathered from across the world.

0:50:110:50:15

Global inventories of numbers, observations, positions.

0:50:150:50:22

The heights of tides, the positions of comets and planets, the rate at which pendulums beat...

0:50:220:50:28

It's a global project, it's big science.

0:50:280:50:32

And many of those observations, many of those mathematical models

0:50:320:50:37

were of course models initially developed

0:50:370:50:40

by Islamic astronomers in Egypt and the Near East and Central Asia.

0:50:400:50:47

But there's a final twist in the tale.

0:50:500:50:54

As the wealth of the Islamic nations subsided through war,

0:50:560:51:00

political and religious entrenchment and the loss of its lucrative trade,

0:51:000:51:04

so its science declined.

0:51:040:51:08

But what this doesn't explain is why their scientific achievements have been so forgotten.

0:51:080:51:13

And that's partly because as Europeans colonised great swathes of the Middle East and Asia,

0:51:150:51:21

they actively encouraged the idea

0:51:210:51:23

that the civilizations they encountered were moribund and in decline.

0:51:230:51:28

It seems the English and the French were uncomfortable with subjugating people

0:51:280:51:35

whose knowledge and science might be as sophisticated as their own.

0:51:350:51:39

So it became important to portray the Islamic world

0:51:390:51:42

in a very specific way,

0:51:420:51:45

namely that yes, they once were very sophisticated and had great scientists and philosophers,

0:51:450:51:50

but of course now, they've fallen into decay.

0:51:500:51:52

Somehow this point of view made the whole colonial enterprise seem much more palatable.

0:51:520:51:59

One of the most fascinating developments, I think,

0:51:590:52:03

in the history of the encounter between western Europeans and other cultures

0:52:030:52:09

is a kind of shift which has got fundamental and terrible consequences

0:52:090:52:17

amongst western Europeans,

0:52:170:52:19

when they start to reflect on why they are superior.

0:52:190:52:25

It doesn't often cross western Europeans' minds that they might not be superior to everybody else.

0:52:250:52:31

For a very long time after all, western Europeans in general,

0:52:310:52:36

the British, for example, supposed that their superiority lay in their religion.

0:52:360:52:40

But then I think around the 1700s, we begin to see a shift.

0:52:400:52:46

And the shift is from claiming that the reason for European superiority is its religion

0:52:460:52:52

to the reason for European superiority is its science and technology.

0:52:520:52:57

Eventually it ends up with the famous phrase, "We have the Gatling gun, and they do not."

0:52:590:53:04

Europeans in that period were quite prepared to acknowledge that in ancient times,

0:53:040:53:12

Islam for example had achieved great things in the sciences.

0:53:120:53:17

But they weren't doing so now.

0:53:170:53:21

So even recent Islamic and Sanskrit astronomy

0:53:210:53:26

was imagined to be very old,

0:53:260:53:28

because if it was very old, it meant that the culture the British were conquering was declining.

0:53:280:53:34

And for the British, that was clearly good news.

0:53:340:53:37

And some experts believe that the effect of this on Islamic scientific history

0:53:400:53:45

is still felt in the Islamic world today.

0:53:450:53:50

The Islamic part and the Arab part have not yet discovered their history

0:53:500:53:54

because their history was obliterated intentionally

0:53:540:53:58

by the colonisation period. And unfortunately when they rediscover it now,

0:53:580:54:03

they are rediscovering it in bits and pieces.

0:54:030:54:05

So today, for many different reasons, the great observatories

0:54:090:54:14

of the medieval Islamic world are ruined husks.

0:54:140:54:19

And it's true to say that most of the great scientific breakthroughs

0:54:190:54:23

of the last four centuries have taken place in the West.

0:54:230:54:28

But that's not to say that science has completely ground to a halt in the Islamic world.

0:54:280:54:34

Now, in the 21st century,

0:54:340:54:36

there are many examples of cutting-edge research being carried out.

0:54:360:54:40

I've arrived at the Royan Institute here in Tehran,

0:54:400:54:43

where they carry out stem cell research,

0:54:430:54:46

infertility treatment and cloning research.

0:54:460:54:49

I was surprised to learn that here in Iran, an Islamic state,

0:54:530:54:57

potentially controversial science like genetic modification

0:54:570:55:01

and cloning is condoned, even funded by a theocratic government.

0:55:010:55:07

One of the uses is when a small part of the heart stops working,

0:55:070:55:10

which is finally going to lead to heart failure...

0:55:100:55:13

Right. So the cells from that part of the heart are actually replaced with the cells that have been cloned.

0:55:130:55:19

Another use of cloning in therapeutics

0:55:190:55:23

is actually creating an animal which has the medicine in their milk, for example.

0:55:230:55:29

So when we drink the milk, we actually receive the medicine we need.

0:55:290:55:35

Considering genetic research has many vociferous opponents in Christian communities,

0:55:350:55:40

I was intrigued to see that here in Tehran,

0:55:400:55:43

they have their own in-house imam to offer support and advice

0:55:430:55:48

on this sometimes quite controversial research.

0:55:480:55:51

TRANSLATION: We have got this medical ethic committee here in Royan Institute,

0:55:550:56:01

and every project which is proposed is investigated

0:56:010:56:07

in this committee, and we see different aspects of it,

0:56:070:56:11

and they have got to justify the project for us.

0:56:110:56:15

I'm not enough of an expert in genetics to truly assess the quality of the work here.

0:56:150:56:20

But one thing I can say is how at home I felt.

0:56:200:56:24

Whatever cultural and political differences we have with the Iranian state,

0:56:240:56:28

inside the walls of the lab,

0:56:280:56:31

it was remarkably easy to find common ground with fellow scientists.

0:56:310:56:36

Nature's rules are refreshingly free of human prejudice.

0:56:380:56:42

That's something the scientists of the medieval Islamic world understood and articulated so well.

0:56:420:56:48

In the 9th century, Al-Khwarizmi synthesised Greek and Indian ideas

0:56:510:56:56

to create a new kind of mathematics, algebra.

0:56:560:57:01

The polymath Ibn Sina brought together the world's traditions

0:57:020:57:06

of healthcare into one book, contributing to the creation of the subject of medicine.

0:57:060:57:12

In remote Iranian mountains,

0:57:120:57:15

astronomers like Al-Tusi paved the way for scientists working hundreds of years later in Western Europe.

0:57:150:57:22

These scientists' quest for truth, wherever it came from,

0:57:220:57:27

were summed up by the 9th century philosopher Al-Kindi, who said,

0:57:270:57:31

"It is fitting for us not to be ashamed of acknowledging truth,

0:57:310:57:35

"and to assimilate it from whatever source it comes to us.

0:57:350:57:39

"There is nothing of higher value than truth itself.

0:57:390:57:42

"It never cheapens or abases he who seeks."

0:57:420:57:47

One moral emerges from this epic tale of the rise and fall

0:57:520:57:56

of science in the Islamic world between the 9th and 15th centuries.

0:57:560:58:01

And that is that science is the universal language of the human race.

0:58:010:58:06

Decimal numbers are just as useful in India as they are in Spain.

0:58:060:58:10

Star charts drawn up in Iran speak volumes to astronomers in northern Europe.

0:58:100:58:15

And Newton's Principia is as true in Arabic as it is in Latin or English.

0:58:150:58:21

What medieval Islamic scientists realised and articulated

0:58:210:58:25

so brilliantly is that science is the common language of the human race.

0:58:250:58:31

Man-made laws may vary from place to place,

0:58:310:58:34

but nature's laws are true for all of us.

0:58:340:58:38

Subtitles by Red Bee Media Ltd

0:58:510:58:54

Email subtitling@bbc.co.uk

0:58:540:58:56

When I think of the world we inhabit, everyone will think,

0:59:170:59:20

"Oh, this was done digitally."

0:59:200:59:21

Yeah. And it wasn't, it was done by hand

0:59:210:59:23

over days and weeks and months and years.

0:59:230:59:26

It was always a very, very deep love affair

0:59:270:59:31

Physicist Jim Al-Khalili tells the story of the great leap in scientific knowledge that took place in the Islamic world between the 8th and 14th centuries.

Al-Khalili turns detective, hunting for clues that show how the scientific revolution that took place in the 16th and 17th centuries in Europe had its roots in the earlier world of medieval Islam. He travels across Iran, Syria and Egypt to discover the huge astronomical advances made by Islamic scholars through their obsession with accurate measurement and coherent and rigorous mathematics.

He then visits Italy to see how those Islamic ideas permeated into the west and ultimately helped shape the works of the great European astronomer Copernicus, and investigates why science in the Islamic world appeared to go into decline after the 16th and 17th centuries, only for it to re-emerge in the present day.

Al-Khalili ends his journey in the Royan Institute in the Iranian capital Tehran, looking at how science is now regarded in the Islamic world.