String Theory is “Fashion,” Penrose Said. We Finally Have a Response

String

theory has attracted a lot of criticism.

It's often used as an example for

everything that goes wrong in the

foundations of physics. So much so that

a lot of people think I'm criticizing

string theory even when I'm not.

Sometimes I'm breathing in a German

accent. Okay, but this video isn't about

me. It's about not the loudest but the

most respected string theory critic,

Roger Penrose. His criticism now got a

very detailed reply from string

theorists. I had a look at the paper.

Roger Penrose won a Nobel Prize in 2020

for his work on black holes, notably the

singularity theorems. I've met quite a

few Nobel Prize winners over the years,

but Penrose stands out among them. For

one thing, his background is in

mathematics rather than physics, and

usually mathematicians don't get

anywhere in physics. They just end up

proving theorem after theorem with

little relevance for reality. Think Ed

Whitten. The other thing that's special

about Penos is that he writes popular

science books that are quite technical

indeed and yet find a large audience.

I'd go so far to say that Penos has

established somewhat of a new style of

scholarly communication and physics. But

now about string theory. In 2016,

Penrose published a book called Fashion,

Faith, and Fantasy. The fashion part is

about string theory. In his book, he

argues string theory has some serious

problems that string theorists seem to

entirely ignore. One example he has is

the question of what all these extra

dimensions are doing in a universe

that's filled with energy. If you

remember, in string theory, one needs

additional dimensions of space other

than the three that we're used to. These

additional dimensions can't be infinite

in extension. They must be very small,

otherwise we'd already have noticed

them. The strings can wrap around the

dimensions and oscillate in them. The

wavelengths of these oscillations have

to fit to the size of the extra

dimensions. This is where the analogy to

violin strings comes from. These

oscillations are like the harmonics of a

violin string. Now, usually string

theorists say that we don't see any of

the higher harmonics because the energy

to make the strings oscillate is

extremely high somewhere at the plank

energy. So, you need a particle collider

the size of the galaxy to make the

oscillations in the extra dimensions

wiggle and observe them. Pen however

says that this doesn't make sense

because you see these extra dimensions

aren't in one place. They're everywhere.

This is like you know the direction up

isn't just here above me it's

everywhere. And then Panu says if you

take the entire energy that's in our

space then that's easily enough to make

the strings in the extra dimensions

vibrate. The problem is that this would

be observable and we don't observe it.

Henos writes, "Although the plank energy

is indeed very large when compared with

normal particle physics energies, it's

still not that big an energy being

comparable with the energy released in

the explosion of about one ton of TNT.

There is of course enormously more

energy than this available in the known

universe. For example, the energy

received from the sun by the earth in 1

second is some 10 to the 8 times larger

on energy terms alone that it be far

more than sufficient to excite the extra

dimensions for the entire universe. The

authors of the new paper now review this

and several others of Penrose's

arguments on the matter of the vibrating

extra dimensions. They say that to get

any observable effect, one really needs

all this energy to be localized in one

region and not be spread out through the

universe. It's because they show the

relevant quantities, not the total

energy, but the energy in a volume of

spaceime. If one wants to create an

oscillation in these extra dimensions

everywhere in the universe, one would

still have to first create it locally

and then get it to spread. easiest way

to recognize a true science paper

footnotes large enough to camp in. They

address several other points of

Penrose's critique, but there's one that

they agree on. It's that the equations

that one needs to describe our space

time in string theory are not just

Einstein's equations. They have

infinitely many corrections. Penrose

worries that this requires specifying

infinitely detailed initial data, which

ironically is very similar to the

problem with infinitely many correction

terms that string theory was meant to

solve. The new paper agrees that this is

a genuine open question and deserves

proper analysis. More work is needed.

The reason I'm telling you about this is

not so much to do with string theory is

that it's a lovely example of scientific

discourse done right. Someone raises a

criticism, someone else addresses it.

This is how science progresses with

fashion, faith, and footnotes. How does

that work? Why is that? So, if those are

questions you also like to ask, you

should really have a look at Brilliant.

It's a great way to practice your

problem solving skills and your critical

thinking. All courses on Brilliant have

interactive visualizations and come with

follow-up questions. What you see here

is from their newly updated maths

courses, no matter how abstract the

topic seems. Brilliant courses have

intuitive visualizations that really

click into my brain. I found it to be a

highly effective way to build up

knowledge. And Brilliant covers a large

variety of topics in science, computer

science, and maths from general

scientific thinking to dedicated

courses. Just what I'm interested in.

Sounds good. I hope it does. You can try

Brilliant yourself for free. And if you

use my link brilliant.org/zabina

or/zabina

or scan the QR code. You'll get 20% off

the annual premium subscription. So, go

and give it a try. I'm sure you won't

regret it. Thanks for watching. See you

tomorrow.