Half a century old black hole theory - which creator said could only be proved by alien or advanced civilisation - 'verified' by Scottish scientists

An artist's impression of the hyper-fast star's ejection from our galaxy's central supermassive black hole
Sergey Koposov/PA Wire
Ellena Cruse23 June 2020

A team of Scottish researchers claim to have verified a decades-old theory about one of space's greatest mysteries.

Scientists at the University of Glasgow’s School of Physics and Astronomy say they have proven Roger Penrose’s 1969 theory that energy can be created in black holes.

They used sound waves in an attempt to substantiate the “extremely odd physics" 51 years after the theory was first proposed.

At the time, Mr Penrose said the theory could only be tested by an advanced or possibly alien civilisation due to technical limitations.

The theory was first coined more than half a century ago 
Getty Images

He theorised that energy could be created by dropping objects such as a rocket into a black hole and splitting the object in two. By retrieving one half, the recoil action would then gain energy due to the black hole’s rotation, he said.

He said the energy could be stored and used to power entire worlds — but the engineering challenges posed by the experiment could not be undertaken at the time.

In 1971, physicist Yakov Zeldovich suggested the theory could be tested with twisted light waves projected onto a spinning surface.

An artist's impression showing a supermassive black hole close up.
PA

To test that, the spinning surface would need to rotate at least a billion times a second – a feat still not possible due to the limitations of engineering.

Now, the Glasgow researchers say they have found a way to experimentally demonstrate the effect using sound waves, which require a much slower rotating surface.

Using a ring of speakers, the researchers sent a rotating wave of sound towards a spinning foam disk.

Attached to the back of the disk were two microphones, which found that as the sound waves passed through the disk, the pitch was amplified by up to 30 per cent, known as a rotational Doppler effect.

Marion Cromb, the paper’s lead author, said: “The linear version of the Doppler effect is familiar to most people.

“The phenomenon occurs as the pitch of an ambulance siren appears to rise as it approaches the listener but drops as it heads away.

“It appears to rise because the sound waves are reaching the listener more frequently as the ambulance nears, then less frequently as it passes.”

They added: “The rotational Doppler effect is similar but the effect is confined to a circular space.

“The twisted sound waves change their pitch when measured from the point of view of the rotating surface.

“If the surface rotates fast enough then the sound frequency can do something very strange – it can go from a positive frequency to a negative one, and in doing so steal some energy from the rotation of the surface.”

During the experiment, researchers found that as the pitch of the sound wave hits the spinning disk, it dropped until it became too low to hear.

Then, when passing through, it was amplified by up to 30 per cent greater than the original pitch.

Professor Daniele Faccio, co-author on the paper, said: “We’re thrilled to have been able to experimentally verify some extremely odd physics a half-century after the theory was first proposed.

“It’s strange to think that we’ve been able to confirm a half-century-old theory with cosmic origins here in our lab in the west of Scotland but we think it will open up a lot of new avenues of scientific exploration.

“We’re keen to see how we can investigate the effect on different sources such as electromagnetic waves in the near future.”

Create a FREE account to continue reading

eros

Registration is a free and easy way to support our journalism.

Join our community where you can: comment on stories; sign up to newsletters; enter competitions and access content on our app.

Your email address

Must be at least 6 characters, include an upper and lower case character and a number

You must be at least 18 years old to create an account

* Required fields

Already have an account? SIGN IN

By clicking Create Account you confirm that your data has been entered correctly and you have read and agree to our Terms of use , Cookie policy and Privacy policy .

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Thank you for registering

Please refresh the page or navigate to another page on the site to be automatically logged in