The Search for Theoretical Physics Episode 26: How Physicists Have Relied on Beauty

The Search for Theoretical Physics

Episode 26: How Physicists Have Relied on Beauty

In previous episodes,

we have touched upon the fact that

physicists

often

talk about

the "beauty" of a theory.

Being simple.

Possessing symmetry.

Having no waste.

Physicists have treated

these qualities

as important values

of a theory.

However,

the word beauty

is originally

a term used in

the worlds of art and

design.

Why is it that

such

seemingly subjective values

have entered

physics,

which aims to

accurately

describe

the natural world?

And

how have physicists

actually

used beauty

as a clue

for their research?

The beauty that physicists speak of has

several

common characteristics.

One of them

is simplicity.

When there are two theories

that can explain the same phenomenon,

physicists

tend to prefer the theory

that can explain more things

from fewer assumptions.

This is

close to a way of thinking common to all science

called Occam's razor.

Another characteristic

is symmetry.

Symmetry is

the property where

the appearance or properties

do not change

even when a certain operation is performed.

For example,

a circle

looks the same

no matter what angle it is rotated at.

This can be said to have

rotational symmetry.

Various types of symmetry

have also been found

within the theories of physics.

The electroweak theory and

the Grand Unified Theory,

which we touched upon in previous episodes,

can also be said to be

attempts to find

hidden symmetries

between different forces.

Physicists have used

symmetry

not merely as

an aesthetic preference,

but as a

practical,

powerful clue

for building theories.

The process by which the physicist Einstein

developed the general theory of relativity

is a representative example

of how a commitment to beauty

guided actual research.

Einstein

started from a single, simple principle:

that gravity and acceleration

are indistinguishable.

And

he persistently pursued

what kind of mathematical formulas

would be needed

to make this principle

mathematically consistent.

In that process,

Einstein

did not simply adjust the theory to fit observational data,

but used whether the theory itself

was mathematically

beautiful and logical

as an important

guiding thread.

Another

famous example

is the attitude of

the physicist Dirac.

As mentioned in a previous episode,

Dirac

derived the equation for the electron

relying on mathematical consistency.

Dirac

later

said something to the effect of the following.

It is a statement to the effect that

the beauty of an equation

is more important than

the equation perfectly matching experimental data.

At first glance,

this might sound like

a bold statement

unbecoming of a scientist.

However,

it is said that

behind this

was Dirac's own

bitter experience.

The equation Dirac derived

initially, when it was first proposed,

had parts that

did not seem to

perfectly match

the observational results.

However,

Dirac

continued to trust

the mathematical beauty and consistency

that the equation itself possessed.

Later,

as understanding on the side of experiments and theory

progressed,

it was confirmed that

Dirac's equation

was correct.

From this experience,

it is said that Dirac

came to value

mathematical beauty

as one

powerful clue

for judging the correctness of a theory.

However,

the attitude of relying on beauty

also carries

great

dangers.

This is because a theory that is felt to be beautiful

does not necessarily

match the actual state of the natural world.

If the commitment to beauty

goes too far,

there is a danger of

disregarding observational data,

which is the most important

criterion for science.

In fact,

in the history of physics,

there are many theories that

were mathematically

very beautiful,

yet were

denied by experiments.

In some fields of theoretical physics,

in recent years,

voices of criticism have been raised

that perhaps experimental verification

is not progressing sufficiently

because of an overemphasis on mathematical beauty.

The fact that theories considered highly mathematical and beautiful,

such as superstring theory,

have not received

definitive verification

through experiments

for many years

has become a representative target

of such criticism.

Beauty is,

for physicists,

a valuable

guidepost for creating new theories, while at the same time,

it can sometimes

become a dangerous temptation

that leads them astray.

Even so,

when looking back on the history of physics,

it is also a fact that

a sense of beauty

has led to many

important discoveries.

Physicists have cherished beauty

not as something that guarantees the correctness of a theory,

but as one

powerful clue

for approaching theories yet to be seen.

Ultimately,

what determines the correctness of a theory

is not beauty,

but the natural world itself.

However,

on the long and difficult path

to reaching the true form of that natural world,

a sense of beauty

has continued to be

an irreplaceable

guidepost for physicists.

Next time

Episode 27: Is There an End Point to "Why" in Physics?