0:00

ABC Listen, podcasts,

0:02

radio, news, music

0:04

and more. Hello,

0:10

this is The Science Show on RN. I'm

0:12

Carl Smith. And yes, Robin, we'll

0:14

be back after a short break. In

0:17

his absence, we'll continue our tour

0:19

underground with another episode of Strange

0:21

Frontiers, this time under busy

0:23

streets to look at fragments of

0:25

Athens' ancient walls. And

0:28

we'll dive into an astronomical conundrum.

0:33

In the early 20th century, Albert Einstein laid

0:35

the foundation for a new physics, changing

0:37

our understanding of the world. He's been

0:40

proved right over and over again. But

0:43

for the field's next breakthroughs, his

0:45

theories need an update. Or maybe

0:47

they need to be proved wrong. Reporter

0:49

Shelby Trainor has been following this hunt for

0:51

the physics of the future. General

0:56

relativity is probably one of the

0:58

most extraordinary creations of the human

1:00

mind. Even though

1:02

Einstein didn't make all the predictions that have come out of it,

1:05

how many predictions have come out of it?

1:07

I mean, how powerful is that? And

1:10

the equations are, you know, a handful of

1:12

symbols long. But that

1:14

very beauty and simplicity, perhaps, that's

1:17

why he was always searching for

1:19

the underlying principles that would incorporate

1:21

everything together. Turns out

1:23

Albert Einstein was right again. This

1:26

should sound familiar. Albert Einstein's

1:28

theory of relativity predicted black holes

1:30

would bend light in a particular

1:32

way. He was right. Einstein

1:34

right again. Still, we're still getting

1:37

those. Einstein made this prediction, as you say,

1:39

a hundred years ago. What

1:41

they're really talking about is Albert

1:43

Einstein's general relativity, considered

1:46

his greatest theory and certainly

1:48

one of the most significant

1:50

contributions to science. General

1:52

relativity is the foundation on

1:54

which modern physics stands. Without

1:57

it, we might not know about black

1:59

holes. or gravitational waves,

2:02

or understand the very orbit we're in

2:04

right now. Without Einstein,

2:06

the world would probably be a

2:08

less intellectually beautiful place for me

2:11

anyway. Dr. Robin

2:13

Ariane Rod is a writer and a

2:15

mathematician. She did her PhD

2:17

in the maths of Einstein's equations.

2:20

He's become such an icon of

2:23

genius, and his theories are

2:25

so revered for their beauty and elegance and

2:27

power that they sort of

2:29

have in a way determined what we think

2:31

of as great science. If

2:34

there's any criticism, that's probably that.

2:38

Since General Relativity was published

2:40

over a century ago, physics

2:43

has been stuck. Because,

2:45

despite its genius, General

2:47

Relativity is incomplete. It

2:50

does not explain everything in the

2:52

universe. And the only way

2:54

to find a theory that does is

2:56

not to keep proving Einstein right, but

2:59

to prove him wrong. That

3:01

is what the physicists want.

3:05

It's a bit like with Newton. You know,

3:07

for 200 years, Newton was seen really

3:09

as godlike in his achievements. That

3:11

was the model for genius and for doing

3:14

science. And it

3:16

was only when somebody said, well, Newton's

3:18

fantastic, but he's wrong on this,

3:21

that you could make progress. At

3:23

the most extreme limits of the

3:25

universe, the theory of General Relativity

3:27

breaks down. Einstein knew this.

3:30

Every physicist who's come since has

3:32

known this. For more than

3:34

100 years, they've been trying to find

3:37

the next big theory to make

3:39

sense of the universe. And

3:41

the physicists that find that knows that they'll

3:43

be on their way to Sweden to pick

3:45

up a Nobel Prize. If you crack this

3:47

nut, that's the path that you're going down,

3:50

because you will change physics. changed

4:00

space and time. For

4:02

two centuries, Newton's laws governed how

4:05

he saw the world, including

4:07

his law of universal gravitation.

4:10

But then came Einstein, at just

4:12

the age of 26, with some thoughts of

4:14

his own. We have to remember, of course,

4:17

what he was asking us to take on

4:19

board. This is astrophysicist Geraint

4:21

Lewis, who happens to share a

4:23

birthday with Albert Einstein. So

4:25

up until 1905, the universe was a simple

4:28

place, right? Newton had to find the way

4:30

the universe works. To Newton, there's

4:32

this stage in which everything

4:34

takes place, and that's space. And there's this

4:36

clock that takes away in the background.

4:38

It's time, right? Time takes away. And it

4:41

just seems so obvious, right? It's like, this

4:43

is common sense. But

4:45

you get to 1905, and then Einstein says,

4:48

now let's do away with that. We'll

4:50

stop with this notion that firstly,

4:52

that time is absolute. Time is

4:55

not this rigid, ticking, universal clock.

4:58

But it changes from place to place in the

5:00

universe. And you sort of go,

5:02

that's not very sensible, surely,

5:04

because it doesn't count my

5:06

experience. You know, if we set our watches together, and we

5:08

go off and do different things, and we come back, our

5:10

watches tend to be in sync, right? But

5:12

when things start to get up to these huge speeds,

5:15

close to speed of light, then these

5:17

become big. And you realize that that's the way the

5:19

universe works. There's a similar story

5:21

with gravity. While Newton's theory

5:23

of gravity made sense at the scale

5:25

of an apple falling from a tree,

5:28

it couldn't account for everything,

5:30

especially at the larger scale,

5:32

like Mercury's strange orbit around

5:34

the sun. Still,

5:37

when Einstein came along,

5:39

Newton's theories dominated physics.

5:42

It was going to take a certain kind of

5:44

person to surpass that. But

5:46

according to Dr. Ariane Rod, Einstein

5:49

was the perfect candidate. He

5:51

was not afraid to ask the simple questions. He

5:54

was not afraid to question

5:56

the simplistic understandings

5:58

either. Right from the top. that he

6:01

was a troublesome student in school

6:04

where he wasn't popular with the teachers

6:06

because he would not hesitate to call

6:08

them out if he thought what they

6:10

said didn't make sense or to ask

6:12

for further clarification. There are a lot

6:14

of stories surrounding Einstein, most

6:16

of them at least partially true, including

6:18

the claim that he was a crappy

6:21

student. Even though he'd loved maths, once

6:24

he got to unilevel he realised there were so

6:26

many possible choices for maths he didn't know where

6:28

to start. But what he did love was physics

6:30

and the maths that applied to that. So

6:32

he just started to skip maths classes to

6:34

go and study by himself what they weren't

6:37

teaching him in physics. But

6:39

it didn't endear him to the professors,

6:41

so there was a very small class

6:44

and normally the graduates would get some kind

6:46

of placing perhaps at the school. And

6:49

Einstein was the only one who didn't and

6:51

that led him on a very disheartening fight

6:54

against the old Philistines as he called

6:57

them, trying to find a job.

6:59

Einstein did find a job at an

7:02

office issuing patents for eight hours a

7:04

day. He spent another eight

7:06

hours on his scientific work and the rest

7:08

of his time asleep. He

7:10

did his breakthrough early work

7:12

that wonderful 1905 year when

7:15

he published special relativity and

7:17

several other groundbreaking papers

7:20

in his spare time in his six day week at

7:22

the patent office. It helped that

7:24

he had a wife, fellow physicist

7:26

Maleva Marich, who not only

7:28

took care of the kids but acted

7:31

as a sounding board for Einstein's many

7:33

ideas. He talked to Maleva

7:35

and he talked to his friend, Michael Besso,

7:38

who also got a job at the patent office.

7:40

So they'd walk to work together and Einstein

7:42

would be bouncing around his latest

7:45

ideas and eventually all came

7:47

together in this extraordinary outpouring. Dr.

7:49

Ariane Rod has perused the many

7:52

letters Einstein sent to his wife

7:54

and friends. There are

7:56

decades worth of correspondence, full

7:58

of ideas, questions... The

8:00

enthusiasm that you see coming off the page

8:03

in those letters that are over

8:05

100 years old are just

8:07

stunning. He's constantly questioning, he's constantly

8:09

asking why, he's constantly coming up

8:11

with a different idea that maybe

8:13

he'll go off and check. He's

8:16

just got this wonderful restless curiosity,

8:19

but he doesn't shy away from trying

8:21

to actually find answers. It's

8:23

not just roaming around and picking a few

8:25

nice flowers, he goes as deeply as he

8:27

can. But let us tell another

8:29

story. Einstein was

8:32

a collaborator. He was not

8:34

a self-contained genius. At

8:36

that time in 1905, he

8:39

was not considered a genius at

8:41

all. He was trying to submit

8:43

papers to earn a PhD so

8:45

he could get some academic credibility,

8:47

and he submitted a special relativity

8:49

paper and it was rejected as

8:51

being incomprehensible. And

8:54

why that's so interesting in hindsight is

8:56

that today it's praised for its elegant

8:58

simplicity. So

9:00

it's interesting, isn't it, how new

9:03

ideas can just take such a long time to

9:05

be digested. You

9:07

can sort of see where they're coming

9:09

from, because even now special relativity can

9:11

be hard to wrap your head around.

9:14

It's probably Einstein's most well known, because

9:16

it gave us the famous equation E

9:19

equals mc squared. The

9:22

theory found that the speed of light does

9:24

not change, even when the source of the

9:26

light is moving. It remains

9:28

constant. That's easy

9:31

enough to digest. We know

9:33

nothing can travel faster than the speed of

9:35

light, but then the theory

9:37

also tells us that time is

9:39

relative. A second for

9:41

me is different for you, depending on

9:43

where you are and how fast you're

9:45

moving. A person on top

9:47

of a mountain will age slightly slower

9:49

than a person in the valley below.

9:52

Still, it's important to note that Einstein wasn't

9:54

the only person working on this at the

9:57

time. On Repronkare published

9:59

paper. not long before Einstein

10:01

did, and with more

10:03

sophisticated maths. But Einstein just

10:06

cut through the physics

10:08

of it to actually get

10:10

proper mutual relativity. And

10:12

then, ten years later, Einstein

10:14

added gravity to the equation.

10:17

His theory of general relativity declares

10:20

that gravity is the curvature of

10:22

space-time. Imagine space-time

10:24

as a trampoline. Space

10:27

and time are woven together and

10:29

can bend and stretch. Now

10:32

imagine the sun as a bowling ball

10:34

weighing the material down. It's

10:37

the mass of the sun that warps

10:39

the fabric of space and time, and

10:42

in turn produces a gravitational pull

10:44

strong enough to keep the Earth

10:46

orbiting around it. One

10:48

person that he did stand on there

10:50

was Herman Minkowski, his

10:53

old maths teacher at Zurich Polytechnic

10:55

whose classes he skipped. And

10:58

Minkowski thought he was a lazy dog for doing so.

11:02

But the idea of space-time as a

11:04

single entity is due to Minkowski. There's

11:07

a quote in physics. I can never remember these

11:09

quotes. But it's something like my theory. It's like

11:11

I was wandering along the beach and I found

11:13

this really shiny pebble. So that's my theory. But

11:16

I realised that if I hadn't have picked it

11:18

up, somebody else would have after me. This

11:20

idea that gravity is the curvature

11:22

of space-time is a departure from

11:24

Newton's theory of gravity. Newton

11:27

saw gravity as a force separate

11:29

from space and time, while

11:31

Einstein saw gravity as a product of

11:33

space-time. Instead of being a

11:35

force, like something that you could pull or

11:37

push with, it became this curvature of space-time.

11:40

This shift in our understanding of

11:42

gravity is what has enabled

11:45

us to make predictions at both the

11:47

universal scale and the everyday

11:49

scale. You can thank general relativity for

11:51

the GPS that gets you where you

11:53

need to be. Professor

11:56

Lewis knows that without Einstein's theory

11:58

of gravity, his job... wouldn't

12:00

be possible. It's inescapable. Whenever you

12:02

want to study the universe, because

12:04

the universe is dominated by gravity

12:06

on large scales, you can't

12:09

get away from talking about Einstein and

12:11

his theories of how gravity works. But

12:13

as grateful as all the astrophysicists are,

12:16

more and more, they're coming up against

12:18

the theory's limits. We know

12:20

that relativity can't be complete because we

12:23

know that there are places where relativity

12:25

definitely breaks down. And

12:27

one of the places is in the heart of

12:29

black holes, if I take Einstein's equations at face

12:31

value and say what happens to mass inside a

12:34

black hole, so it falls in and it basically

12:36

all collapses down to a point and

12:38

that point has zero volume. So once

12:40

we get things with zero volume, so

12:42

you have mass and zero volume, you

12:45

get infinite densities. And physicists

12:47

don't like infinities in their theories. When

12:49

infinities show up in the mathematics of

12:51

something physical, like a black hole, it's

12:54

probably a sign that something has gone wrong.

12:57

The theory has reached its limit. Some

13:00

people go, oh, maybe it is something physical,

13:02

maybe the universe does allow infinities. And other

13:04

people just go, no, that's nuts. There has

13:06

to be something else which is missing from

13:08

our physics that we haven't discovered yet. There's

13:12

a similar kind of problem with the start of the

13:14

universe. So when we look at the universe and we

13:16

ask, I can take my mathematical equations and I can

13:18

calculate the evolution of the universe all the way back

13:20

to the start, but when I get

13:23

to the start, there's an infinity in the equations. And

13:25

it's like, this can't be right. We can't start from

13:27

an infinity and then work out the evolution of the

13:29

universe. So what it's telling us is

13:31

that back then, probably there's a point

13:33

where relativity, as we understand it, breaks

13:35

down and whatever is gonna replace it,

13:38

that comes into play. So

13:40

it's not that general relativity is wrong,

13:42

it just has its limits. Just

13:45

like Newton's theory of gravity had its

13:47

limits, ones that Einstein sought

13:49

to expand. Now

13:51

physicists are trying to expand on

13:53

Einstein's theory of gravity. This

13:56

is where things get quantum. life

14:00

and into the 1960s etc when we

14:02

understood that we had to worry about

14:04

the strong and the weak forces well

14:07

is that there's been this realization that

14:09

electromagnetism, the strong force and the weak

14:11

force all share common properties, they're all

14:13

quantum forces. These are fundamental forces of

14:16

nature meaning as far

14:18

as we know they can explain

14:20

every known interaction in the universe.

14:23

Three out of these four forces

14:25

can be written in the language

14:27

of quantum mechanics meaning they're all

14:29

carried by discrete particles otherwise

14:31

known as quanta. That's one of the

14:34

great successes that people have had going

14:36

back a hundred years now is that

14:38

what we thought were three separate forces

14:40

are really just manifestations of the same

14:42

thing. But there is one more fundamental

14:45

force that so far hasn't been accounted

14:47

for in this quantum world. And there's

14:49

this goal to bring

14:51

gravity into the picture. What

14:54

people want to do is have a

14:56

theory of everything right they want to

14:58

encompass gravity electromagnetism strong force weak force

15:00

one set of mathematics and you use

15:03

that mathematics get electromagnetism over here strong

15:05

force etc over there. But gravity absolutely

15:07

refuses to play ball. It refuses to

15:10

say there is a particle

15:12

which carries gravity from one place to

15:14

the other and people

15:16

don't quite understand why. I mean people

15:18

have been hitting this scientific problem with

15:21

sledgehammers for a long long time and

15:23

it just refuses to yield. This is

15:25

the discrepancy that has been described as

15:28

the holy grail of physics. The

15:31

mission is to bridge this

15:33

gravitational gap between quantum mechanics

15:35

and general relativity. And

15:38

people have been trying even heinstein

15:40

was trying to do this on

15:42

his deathbed basically was trying to

15:44

make these worlds fit together and

15:46

they just refuse to. So what

15:48

we're dealing with here is the

15:50

biggest of problems versus the smallest

15:52

of problems if you like. This

15:54

is physicist susan scott a distinguished

15:56

professor at ANU. Currently businesses have

15:58

two separate kind of system of

16:00

rules for explaining how nature works,

16:02

and one is general relativity, and

16:04

that beautifully counts for gravity and

16:06

all of the things that it

16:08

governs, like orbiting planets and gliding

16:10

galaxies and so on. But then

16:12

you've got quantum mechanics. Quantum theory

16:14

is really adept at describing what

16:16

happens at the very small scale

16:18

and the atomic scale. But

16:20

the thing is they're fundamentally

16:22

different theories and they have

16:24

very different formulations. So we've

16:26

got genuinely kind of incompatible

16:28

descriptions of reality itself. As

16:31

you heard earlier, when we try

16:33

to apply general relativity to the

16:35

worlds of the very small, we

16:37

get infinities. Likewise, quantum mechanics

16:40

runs into serious trouble when you

16:42

try to blow it up to

16:44

cosmic dimensions. And that's because quantum

16:46

mechanics is very weird. One

16:49

particle can be in two places at

16:51

once. Two particles can

16:53

remain connected over astronomical

16:55

distances and can

16:58

still instantaneously affect one another.

17:00

These are proven phenomena. And

17:03

yet, when applied to the scale of you

17:05

or me, they don't seem

17:07

possible. Physicists agree there's

17:09

got to be something missing, even

17:11

when they don't agree on much else. Once

17:14

one learns and start using quantum

17:16

mechanics and one learns and start

17:18

using ice and theory of gravity,

17:21

it's clear there's a problem. This is Carlo

17:23

Rivelli, a physicist and a popular

17:25

science writer of books spanning from

17:28

physics to philosophy. He's

17:30

been working on this problem for his entire

17:32

career. The attempt to solve

17:34

this problem have been many through actually

17:36

models actually, because as I said, Einstein

17:39

is the first who realized that. Einstein

17:41

immediately after writing his equation in 1915,

17:45

one year later, he says, by the way,

17:47

mites only cannot be complete about gravity because

17:50

it has to deal with quantum phenomena where

17:52

he knew existed. Einstein wasn't

17:54

a big fan of the random nature

17:56

of quantum mechanics. Funnily

17:58

enough, he's considered a... loop

20:00

quantum gravity, time isn't

20:02

continuous either. We jump

20:04

from one moment to another with nothing

20:07

in between. The flow

20:09

of time isn't a flow, it's

20:11

more like hopscotch. The geometry

20:13

of space around us is not fixed.

20:15

It's a quantum thing, so it can

20:18

be a superposition of different geometry. And

20:20

so is time, which is even harder

20:22

for us to conceptualize. But if quantum

20:24

mechanics teaches us anything, it's

20:26

that just because it's hard to conceptualize

20:28

doesn't mean it's wrong. The

20:30

world is very strange. There is no

20:33

space, there's no time, there's quantum space,

20:35

quantum time. That's loop quantum gravity. This

20:37

loopy network that is space and time

20:39

is inconceivably small, which is

20:42

why from our reference point, it

20:44

seems continuous. Like a t-shirt,

20:46

this is a continuous two-dimensional thing which

20:48

can bend like ice time, space time,

20:51

or stretch. But if you look carefully,

20:53

closely, you see the threads. So one

20:55

possibility for testing the theory would be

20:57

to find these things. This

21:00

is the catch of theoretical physics. It's

21:02

a lot of thinking, talking, and maths.

21:05

A theorist might propose an experiment,

21:08

but they're always easier said than

21:10

done. And while

21:12

our current technology is extraordinary, we'll

21:14

need a few more advancements to

21:17

be able to detect the very

21:19

fabric of existence itself. For

21:22

now, all Carlo Rovelli has is the

21:24

maths and his wholehearted belief

21:27

that loop quantum gravity is the

21:29

right approach. It just takes

21:31

generativity as it is. It doesn't

21:33

add fields, it doesn't add particle, it

21:35

doesn't think, oh, there are more dimensions.

21:38

Just take Einstein theory, takes quantum mechanics

21:40

as it is. Simple as

21:42

that, right? Well, simplicity is

21:45

the goal. Einstein set an example

21:47

here with his theories. When

21:50

they're simple and elegant, it's assumed you're

21:52

on the right track. I think what

21:54

we've learned about modern physics is that

21:56

elegance is very much in the eye

21:58

of beholders. The current... dominant theories

22:00

of quantum gravity are string theory and lube

22:02

quantum gravity to a lesser extent. And you

22:05

know, spring theorists think their theory is beautiful.

22:07

Other people from the outside might think less

22:09

so. I think my theory is

22:11

beautiful, but maybe people from the outside don't think that.

22:13

So that's very much in the eye

22:15

of the beholder. I'm glad you say that because

22:18

reading up on this string theory being

22:21

described as elegant was very confusing to

22:23

me because I was like, you need

22:25

to add nine more dimensions. How is

22:28

that simple? It's actually seven

22:30

dimensions, but the point still stands. I'm

22:33

talking to Jonathan Oppenheim. Yes, Oppenheim, not

22:35

Oppenheimer. He used to be a string

22:37

theorist, but now he's questioning the path

22:39

most of his colleagues have been taking.

22:41

It's possible that the challenges that we're

22:43

facing in constructing a quantum theory of

22:45

gravity, it's possible that that's just because

22:47

quantum gravity is really hard and it's

22:49

going to be really challenging. And we're

22:51

very far from having the techniques we

22:54

need to solve that. But it's also

22:56

possible that the reason it's become so

22:58

difficult and challenging and not simple is

23:00

because we've gone off in the wrong

23:02

direction. I think it's worth a

23:04

shot at trying to see if perhaps the

23:07

idea of quantising gravity has been the wrong approach.

23:09

The suggestion that gravity can't

23:11

be quantised is controversial. This

23:14

has been the path most travelled

23:17

for decades. I think like most

23:19

people, I'd always been taught that

23:21

in order to make general relativity

23:23

consistent with quantum theory, that we

23:25

needed to quantise gravity. And it

23:27

was only kind of relatively recently

23:29

that I realised, and people actually

23:31

realised before me, that you could

23:33

actually construct a consistent theory of

23:35

quantum mechanics and classical mechanics. And

23:37

you didn't need to necessarily quantise

23:39

gravity in order to make things

23:41

consistent. So his main idea is

23:43

essentially that quantum mechanics does not

23:45

apply to gravity. That's

23:48

his suggestion. A reminder, there are

23:50

four fundamental forces at work in

23:52

the universe. We've proven that quantum

23:55

mechanics applies to three of those

23:57

forces. Jonathan Oppenheim is

23:59

suggesting that... the fourth force is

24:01

different. The idea that we

24:03

should not quantize space-time is, for

24:06

a while, I think probably 99% of

24:08

my colleagues thought I was being a

24:10

crackpot. I think that is now down

24:12

to maybe only two thirds of my

24:14

colleagues think I'm a crackpot now. So

24:16

at least that's going down, but it

24:18

should be mentioned that I think most

24:20

people think we should quantize gravity. Carlo

24:22

Revelli is most people. He's denying the

24:25

main discovery of Einstein, which is space-time

24:27

is the gravitational field. He's denying the

24:29

main discovery of quantum mechanics, which is

24:31

everything is quantum mechanics. He's saying

24:33

everything we have learned in the 20th century is

24:35

just basically wrong. We haven't understood it. Good, go ahead

24:38

and try. I

24:41

don't advise my students to go that

24:43

way. Carlo Revelli doesn't just disagree with

24:45

Professor Oppenheim in theory. He's

24:47

put his money where his mouth is. How much

24:49

did I bet? One to five thousand. Oh, five

24:51

thousand. One to five thousand. I'm not sure. I'm

24:53

not sure. I'm not sure.

24:55

I'm not sure. The

24:59

two men you've heard sparring back and forth

25:01

on the nature of space-time haven't known each

25:03

other that long. Carlo Revelli

25:05

heard Jonathan Oppenheim speak at a conference before

25:09

the world shut down in 2020. They got

25:11

to know each other through a bet on

25:14

whether gravity is quantized or not. So

25:16

as I have no problem of betting $5,000 against $1 on

25:18

that, I

25:21

would not bet $1 against a million

25:24

because, yeah, you know, I don't want to

25:26

risk my life on that or my entire wealth

25:29

on that. But certainly $5,000, even more,

25:31

I could easily bet. And

25:34

so he said, OK, let's make this bet. OK, I said,

25:36

you know, shake hands. If

25:39

I lose, I'll probably owe him like a

25:41

few crisps. If I win, then

25:43

I get 10,000 crisps, something like

25:45

that. I think at one point we were

25:47

thinking these bazinga balls, which you can swim

25:49

in. But I'm not sure that

25:52

that's what I want. I guess it's unclear when

25:54

the bet will be decided. So I might have

25:56

quite a bit of time to decide what I

25:58

want. For Carlo Revelli,

26:00

This was probably, maybe possibly,

26:02

a risk-free bet. He'd

26:05

be more apprehensive going toe to toe

26:07

with other theories of quantum gravity. I

26:09

would not bet one against 5,000 against

26:11

string theory or against, I mean, I

26:14

think my scientific judgment is that loop

26:16

quantum gravity is much more solid, but,

26:18

you know, we have to wait and

26:20

see the development. Things in science get

26:22

clarified slowly, right? It's not that you

26:24

make an experiment and bingo, this is

26:27

right, this is wrong. But the thought

26:29

that the gravitational field is not quantized

26:31

at all? That's very strange to me.

26:34

You know, if somebody comes to you, they

26:36

have a theory that humans are all the

26:38

same speeches, but actually people from New Zealand

26:40

are different. It's a different speeches. Can

26:43

I just a priori say that's wrong?

26:45

No, I mean, study this possibility, but

26:48

what's the likelihood of it? Come on.

26:50

Until we know for sure, it's open

26:53

for debate. Quantum gravity, not

26:55

the whole New Zealanders are all aliens

26:57

thing. I

26:59

don't think we should presuppose what theory

27:02

nature chose and we need to experimentally

27:04

test for which one it chose. Professor

27:06

Oppenheim makes an important point. Yes,

27:09

his idea does challenge long running

27:11

assumptions. Yes, it might be

27:13

unlikely, but also it can

27:16

be tested. It had always been

27:18

assumed that we had to go incredibly high energies

27:20

in order to test quantum gravity. Like we have

27:22

to find black holes if we're going to test

27:24

quantum gravity. And I think what we've

27:26

learned recently is that's not the case. There are

27:28

low energy experiments we can perform that

27:31

would test the quantum nature of space time. One

27:33

is that we can look for something called gravitationally

27:36

mediated entanglement. Entanglement is

27:38

a quantum phenomenon. I

27:41

described it earlier. Two particles

27:43

can interact and then remain connected,

27:46

sharing information even when they're

27:48

thrown apart. And we've

27:50

seen this happen. What we're yet to

27:52

see though, is whether gravity can do this

27:54

all on its own. If

27:57

it can, well, there you go. Gravity

27:59

has quantum. since

34:00

we've had the cosmic rug pulled out from

34:02

under us, since a

34:04

new theory has come along and properly

34:06

changed the foundations. As

34:08

much as everyone knows and loves

34:11

general relativity, it might

34:13

be time for Einstein to share the

34:15

headlines with someone new. Science

34:25

journalist Shelby Treanor with that story. And

34:27

next time we'll have another deep dive

34:29

into physics, the hunt for dark matter,

34:31

another crucial puzzle piece to understand how

34:34

the universe ticks. You're

34:36

listening to the science show here on RN. I'm

34:38

Carl Smith. And now let's

34:40

look beneath the streets of Athens at

34:43

the city's ancient ruins for another episode

34:45

of Strange Frontiers, exploring the science that

34:47

happens beneath your feet. A

34:51

city like Athens sits atop layer

34:53

upon layer of history. Some

34:56

ancient sites are well preserved and

34:58

protected, like the Agora, temples

35:00

like the Parthenon, or the

35:02

Acropolis, the majestic ancient citadel perched high

35:05

in the center of the city. But

35:08

many more sites lie below the surface,

35:11

holding clues about how ancient Athenians

35:13

lived in each era of the

35:15

city's long history. Often

35:17

they're poorly documented or hidden

35:19

altogether. It's not uncommon

35:21

to find signs of them in underground

35:24

car parks, workshops, or storage cellars here.

35:26

There's an arcade, several small

35:28

shops. And

35:30

in the basement, we will see parts of

35:32

the city wall. And

35:34

these sites can be unwittingly

35:37

damaged, overlooked, or lost as

35:39

the city continues to rapidly

35:41

grow and change. But

35:44

a new project is helping today's

35:46

Athenians discover and protect the ancient

35:48

structures below the buzzing modern metropolis

35:51

by digitizing archaeological records.

35:54

The dream was to create a digital

35:56

map with all excavations

35:59

in Athens. All this

36:01

information was fragmented,

36:04

so we had to bring them together. Hey,

36:08

this is Strange Frontiers, a series

36:10

about those doing science in hard-to-reach,

36:12

off-limits, and remarkable corners of the

36:14

Earth. And today, come

36:17

for a tour below Athens to

36:19

look at the city's ancient structures,

36:21

with an archaeologist working to help

36:23

citizens, urban planners, scholars, and

36:26

even the odd tourists understand and

36:28

celebrate the history hidden beneath the

36:30

surface. It's

36:33

a bright, warm, clear day in

36:35

autumn, and in the busy central

36:37

Kotsia Square, Athenians hurry past an

36:39

open excavation site. At

36:41

the edge of the pit is

36:43

a tall, smiley, enthusiastic archaeologist, my

36:45

guide for the day. My

36:48

name is Anita Teoharaiki. We

36:51

are at a very nice

36:53

place where we can see ancient remains.

36:57

So there are many people today around us because

36:59

the metro station is over there, and this

37:02

street, wherever you

37:04

walk, you can see the acropolis.

37:08

Many are rushing past the Olympic pool-sized hole

37:10

in the square, and through tall

37:12

metal fences, Dr. Anita Teoharaiki

37:15

points out ancient thoroughfares in the

37:17

layers of excavated ruins below us,

37:20

showing that this square has been busy for

37:22

centuries. It's a place where

37:24

ancient remains were recovered during excavation, during

37:26

a rescue excavation, as we call them.

37:29

This was excavated in the 1980s. Here

37:33

in the third century after Christ,

37:36

we have a very important industrial

37:38

complex with 27

37:41

ceramic kilns. This site

37:43

was discovered by accident during some urban work,

37:46

and rescue excavations like these aren't uncommon

37:48

in Athens. Below

37:51

these pottery kilns, the rescue archaeologists

37:53

found key arterial roads from different

37:55

eras of the city's history. or

38:00

two ancient roads. And

38:03

that is the place of their intersection.

38:05

And even deeper down through the layers,

38:07

a cemetery. After

38:09

archaeologists finish cataloging sites like this,

38:12

information is published in an archaic

38:14

periodical and sometimes a tiny plaque

38:16

is installed. And that means

38:19

the majority of the detailed snapshot of

38:21

life collected here is essentially

38:23

inaccessible to the average person. And

38:26

yet those finer details are important. They

38:29

can help piece together the layout of

38:31

the city throughout different eras, connecting the

38:33

sections of old roads between different sites,

38:35

filling in gaps in ancient maps. This

38:38

can help developers or city planners get a

38:41

sense of which areas nearby are likely to

38:43

hold more secrets like this. All

38:45

remains are in relationship with other

38:48

structures. And what interests us is

38:50

to examine time and space together.

38:53

Which is why she and her colleagues

38:55

created an organisation called the Dippylon Society

38:58

to build an immense archive that brings

39:00

all of this information together. Dippylon

39:03

Society is a non-governmental

39:05

society. It was founded in

39:07

2014 by four friends. Three of

39:11

us are archaeologists and one is specialising

39:14

in geography and cartography and

39:16

GIS. The dream was to

39:19

create a digital map with all remains

39:22

of excavations in Athens.

39:25

Where did people used to

39:27

live or where were the places of

39:29

their everyday work, which were the main

39:31

roads. Our ideal was

39:34

to create a database that

39:36

would have all this. And

39:38

the digital tools they've dreamt up and created are

39:41

now used by thousands of people

39:43

across Athens to better understand and

39:45

protect the layers of history below

39:48

the streets. Dr Teokoraki studied in

39:50

Greece and in the UK before

39:52

diving into a PhD and a

39:54

book mapping the ancient city walls

39:57

of Athens. It

39:59

was hard even for a train. archaeologist

40:01

to sift through old excavation reports to

40:03

make this map. And during

40:05

this process, she realised there was a

40:07

gap, turning all of this scattered data

40:10

into something professionals could actually use. She

40:13

met others in her field who'd noticed the

40:15

same problem and were piecing together the layout

40:17

of other ancient structures. The

40:19

dissertation of Lida Kostaki, who was a co-founder

40:22

of the diplon, had as a

40:24

topic the roads inside the city

40:26

wall. And my PhD

40:29

had the topic the city walls. These

40:32

two important grids were an excellent foundation

40:34

to start compiling a new digital map

40:37

of the ancient city. And

40:39

the name of their organisation comes from

40:41

a central point where the roads and

40:43

walls of ancient Athens met. We

40:46

met at the diplon gate, which is the central

40:48

gate of ancient Athens. That's

40:50

where our minds met. The

40:53

diplon society applied for and received

40:55

funding for a massive geographic information

40:57

system, or GIS, project called

41:00

Mapping Ancient Athens. This

41:02

was its first digital tool. This

41:04

project sits in the emerging field of

41:07

digital humanities, but aims to

41:09

make extensive and often archaic catalogues

41:11

of knowledge more accessible to modern

41:13

users. So they began

41:15

by sifting through all of the excavation reports they

41:17

could find of places like the pit

41:20

next to us. These results

41:22

have all been published in

41:24

the archaeological bulletin. This

41:26

meant we went through more than

41:28

70 volumes of this journal

41:31

and several other journals. It's

41:33

almost like an archaeology project on

41:35

archaeology itself. They digitised

41:37

and organised everything and built a map-based

41:40

tool showing details of each excavation across

41:42

the city. All this

41:44

information was fragmented,

41:47

so we had to bring them together. This

41:49

tool is now used by researchers to look

41:52

at the big picture, or to help sift

41:54

through mountains of data. City

41:56

and urban planners use it to try to

41:58

predict where other sites of historical significance might

42:00

be lurking. But Dr.

42:02

Teo Karaki says visitors and citizens

42:04

also use it to understand local

42:07

neighbourhoods. When you leave for

42:09

example in a particular place in Athens

42:11

and you're curious to see what's beneath, you

42:15

can enter this database and you will find

42:17

what's underneath your feet. And

42:20

that unexpected success inspired them to find

42:22

new ways to present this information to

42:24

the public. So in 2018 they launched

42:27

their first web-based app called Walk

42:29

the Walls Athens inspired by Anita's

42:31

work. We're in the northernmost part

42:33

of the ancient city. The

42:36

fortification here... Drawing on the information in

42:38

their mapping database, this app

42:40

also has collated pictures and diagrams paired

42:42

with an audio tour. We thought that

42:45

it would be important

42:47

to transfer this knowledge to

42:49

a wider audience. And

42:52

today Anita's offered to take me for a

42:54

tour following that route along the ancient walls

42:56

of Athens to show me what it's

42:58

been like bringing the old city back to life and

43:01

to see how it's helping modern Athenians celebrate

43:03

the history of their local area. As

43:07

we set up from Kotsia Square, Dr. Teo

43:09

Karaki shows me the free mapping ancient Athens

43:11

map, the core database for all the work

43:13

that's followed. This mapping ancient Athens, you can

43:15

see it in your mobile, the polygons

43:18

in circularly excavated sites.

43:22

The app shows archaeological sites like the one

43:24

we've just visited. It also shows

43:26

the ancient circuit wall combined with modern

43:28

Athens landmarks. We're

43:30

heading to a gate of the Themystoglian

43:33

city wall which encircled the

43:35

city which was around the Acropolis. That city

43:37

wall had the length of 6400 meters

43:41

approximately. The city wall was

43:43

built in 479

43:46

before Christ and this wall had a

43:48

stone circle of about one

43:50

and one half meters

43:53

high and the rest till

43:56

about seven or eight meters was made of

43:58

mud brick. a section

44:00

of this ancient city wall. It's in the middle

44:02

of a busy street but fenced off and protected.

44:05

And next to it is a small plaque. This

44:07

is, I think it's about 10 lines.

44:10

It's a nice way to express what

44:12

we see though. But in the

44:14

mapping tool on her phone we can

44:16

see layers of defensive structures throughout different

44:18

eras. Also ancient infrastructure plus

44:21

links and photos. Whatever has

44:23

been found as a physical remain

44:25

during the excavation is here. Nothing

44:28

was left out. There are

44:30

layers sorting sites into different eras of

44:32

ancient civilization. The Neolithic, the

44:35

Roman, or the Ottoman period of the city.

44:38

And there are different structures sorted

44:40

by their function. For example religious,

44:42

domestic, water supply, fortifications. But

44:45

then she opens up the newer public facing web

44:47

app, Walk the Wall Athens. This

44:49

is a very different offering. There are 35

44:51

stops on the audio tour circuit. At

44:54

each there's a detailed story, maps,

44:56

pictures of remains and excavations. And

44:59

even some artist renditions. Plus pictures of

45:01

artifacts from this site now sitting in

45:04

nearby museums. The combination of resources

45:11

helps immerse you and draws you back

45:13

in time to imagine what the area

45:15

looked like millennia ago. It

45:18

also helps you marvel at how many ancient

45:20

sites are scattered through the

45:22

basements of

45:24

the buildings

45:38

around you. And that's exactly

45:40

where Anita plans to take me next.

45:42

Down below the busy streets around us.

45:45

This is the line of the city wall. We

45:47

are going to walk along this way. We can find

45:50

a place where there are important

45:53

remains of the city wall but

45:55

hidden underneath. Weaving through people on the

45:57

street, Anita's taking me to a modern bank building.

46:00

With a thumbs up from a security guard, we

46:02

skirt down the ramp into its parking garage. The

46:05

car park of people working in the bank, yes. The

46:07

car park looks like it could be anywhere in the world.

46:10

Except that just beside the ramp down is

46:12

a wide excavation pit, showing

46:15

that the modern building is sitting right

46:17

on top of ancient stone wall remains.

46:20

Yes, this was excavated in 1966 and

46:24

at that time there was a very

46:26

strong interest from the part of the

46:28

state to preserve and show these remains.

46:32

Without the app or a savvy tour guide, you'd

46:34

have no idea such a giant section of

46:36

the ancient wall was hidden under there. We

46:39

head back out onto the street towards the next

46:41

stop on the ancient city walls tour. This

46:44

is an arcade, several small

46:46

shops and in the

46:48

basement we will see parts of the city

46:50

wall. So we

46:52

see textile printing and manufacturing

46:54

shops. And here is a niche. What

46:57

is inside is a part of

47:00

the exterior face of the

47:02

city wall. Anita, quick

47:04

to strike up a conversation, starts talking with one

47:06

of the shop owners. He works

47:08

in a small printing shop. He gives me a

47:10

big friendly grin and introduces himself as Nikos. With

47:14

Anita translating for us on the fly. His

47:17

name is Nikos Bardis and

47:20

he has this printing shop

47:23

since 1986. He

47:32

says that you can find the ancient

47:34

wall and its stretches all along the

47:36

city. Of course he has added that

47:38

there is an eight floor building on

47:40

top of it and he wonders whether

47:42

this way of preservation would

47:44

be the best one or not. We

47:50

say thank you to Nikos and as we

47:52

follow the app towards our next stop, Anita

47:54

tells me this is exactly what Dippylan's latest

47:56

public facing projects aim to do. To

47:59

help locals connect to the everyday history of where

48:01

they live or work or play. If

48:04

they know what's there, she and her colleagues hope

48:06

they'll also help fight to protect it. Or

48:08

maybe just find new ways to appreciate or celebrate

48:10

it. Everyday life can change through

48:12

that knowledge. It makes you

48:15

broaden your whole scope. Is

48:17

that something you hear from people who use the

48:20

web app as well? Yes, some people

48:22

discovered things and then we received, oh, that's

48:25

the place where I live, I never knew

48:27

that, thanks for that. Another

48:29

lady, she wrote a poem. This

48:32

means that something touched her. We

48:35

move on to the next stop on our tour,

48:38

a larger, more upmarket tower. Anita

48:40

chats with the building manager who

48:43

introduces himself as Leonidas. What's Leonidas?

48:47

He's the man who is responsible for

48:49

the building here. And

48:51

he takes us over to a blown up photograph

48:53

in the main lobby. It shows a section of

48:55

the ancient wall underneath the building with some text

48:57

around it. He just

48:59

decided to put that picture

49:02

up. He says that tourists

49:04

already know our application,

49:07

so they use it. That's what

49:09

makes us happy. But what

49:11

we've done is really useful for the public and

49:14

whoever wants to visit, thanks. I'm

49:16

not sure about that. He says

49:19

he's really proud, he's doing his best

49:21

to keep it as it should be

49:23

kept. Leonidas

49:25

directs us towards the basement to take a look.

49:28

We walk down some steps and in

49:30

amongst storage lockups, there's a long stretch

49:32

of ancient wall and it's so

49:35

clean that it looks like it's only just been chipped

49:37

and chiselled and shaped. As

49:39

if it was just finished in

49:41

antiquity, so well preserved.

49:45

There is a text explaining what you

49:47

have there. And they have

49:49

this from our book, I think,

49:52

which is very initiative, which

49:55

means they're really proud of it. We

49:58

walk back outside thanking Leonidas. on the

50:00

way back into the sunshine and the busy street

50:02

beyond. Anita

50:05

is still smiling after seeing how the

50:08

building's occupants are enthusiastically preserving their little

50:10

segment of the wall. Yes,

50:13

yes, I saw in his

50:15

eyes that he's really happy that he's part

50:17

of it in a way. This

50:20

must be really very important for him. For

50:23

our final stop, Anita Teokoraki takes me to

50:25

a city park to see a

50:28

section of the old wall which had been

50:30

removed years earlier during some urban reconstruction work

50:32

nearby. We're sitting on

50:34

a chunk of the old city wall here. Cicadas

50:37

in the trees, a cat up

50:39

in the tree next to us here sleeping in the branches. And

50:42

perched here we take a closer look at the

50:44

newest additions to the Dippylon Society's apps. Their

50:47

latest audio tour shows the route

50:49

to Plato's Academy with watercolour paintings

50:51

and illustrations. It was

50:53

hot and there was a bright sun above, warming

50:56

the backs of the workers in the olive

50:58

grove. And Anita says after

51:00

they launched their first programs, people

51:02

across the city from different professions

51:05

offered to contribute, adding depth to

51:07

the experience with music or artwork.

51:09

For example, Pavlos

51:11

Chabidis, who is

51:13

the painter, he listened to her stories

51:15

and then he was inspired and then

51:18

draw people as he

51:20

imagined them in antiquity, philosophers going

51:23

along the street. There

51:26

are also 3D reconstructed ancient landscapes,

51:29

even some augmented reality sections to pull

51:31

users deeper into these city walks and

51:33

deeper back in time. We

51:35

are open to new ideas to create

51:38

new digital tools either for research or

51:40

for the public. And we

51:42

would be very much happy if another

51:44

citizen in the world would like

51:46

to use this platform to

51:48

enhance their own heritage. Alongside

51:51

all this work for the public, Anita

51:53

tells me they're also starting to see

51:55

researchers engaging with their core mapping ancient

51:57

Athens database in new ways, connecting with

51:59

the world. neighbouring excavation plots and

52:01

finding new sites of interest. Because

52:04

you can see all transformations through time.

52:06

You can connect and see, okay, this,

52:08

yes, this is a part of a

52:11

house. And next one is another excavation.

52:13

It's another part of the house. Maybe

52:15

it's the same house. They maybe reconstruct

52:17

an idea which before we couldn't do

52:19

because we didn't know where was each

52:21

part. Did you ever imagine when

52:24

you were maybe doing a PhD in

52:26

archaeology that you would be creating new

52:28

web apps, new software? No

52:31

idea. I had no idea. No,

52:33

it was beyond my imagination. I

52:36

can't believe it. Dr Anita

52:38

Teokaraki has been thrilled watching these

52:40

new tools help modern Athenians connect

52:43

to their past. And

52:45

she's also been personally fascinated as this

52:47

project has slowly transformed her way of

52:49

interacting with her hometown too. Helping

52:52

her drift back through time as she

52:54

imagines walking over ruins. Marrowing

52:57

the distance between her life now and

52:59

those who came before her. People

53:02

would like to be part of this history. It's

53:06

something really unique to

53:08

have this information. If

53:11

people today know what's underneath

53:13

and have the knowledge, then they can

53:15

act on the help

53:17

to present them in a better way. Dr

53:23

Anita Teokaraki and there's a link to Dippylon's

53:25

free web apps on the Science Show website.

53:29

Join us next time for another episode

53:31

of Strange Frontiers under a mountain in

53:33

the hills behind Rome. And

53:36

we'll hear from a woman working to

53:38

keep space safe and collaborative for everyone.

53:41

This episode was produced on the lands of

53:43

the Gadigal, Terbil and Yagara peoples. A

53:45

sound engineer is Bela Troppiano. I'm Carl

53:48

Smith. Bye for now. You've

53:57

been listening to an ABC podcast.

54:00

Discover more great ABC podcasts,

54:03

live radio and exclusives on

54:05

the ABC Listen app.