Scientists build world’s first black hole bomb inside lab

Physicists in the UK have created the first-ever laboratory version of a black hole bomb, replicating a decades-old theoretical phenomenon where energy around a spinning black hole builds up and triggers an explosive release.

The research team, led by Hendrik Ulbricht, PhD, a physics professor at the University of Southampton and one of the study’s authors, built the experimental setup using a rotating aluminum cylinder surrounded by magnetic coils.

By mimicking the conditions proposed in the original theory, initially proposed by English mathematician Roger Penrose in 1971, they successfully demonstrated how energy could be extracted and amplified through a process known as superradiance.

Even though the experiment did not involve real black holes, the scientists believe it could provide valuable insights into how black holes interact with the fabric of space.

A decades-long challenge

Penrose’s idea describes a way to extract energy from a rotating black hole. It relies on an effect called frame dragging, where a rotating object twists nearby space and pulls objects along its spin.

Although the effect has been observed near Earth, it is extremely small. In contrast, near a black hole, frame dragging becomes much stronger. In the ergosphere – a region outside a rotating black hole where space-time is dragged around by the black hole’s rotation – objects can be dragged at speeds exceeding that of light in a vacuum.

The theory was further extended by Soviet physicist Yakov Zeldovich, who suggested a couple of years later that similar energy amplification could happen if light passed around a rotating metal cylinder at incredible speeds. He also predicted that if a reflective mirror surrounded the cylinder, the energy could build up in a positive feedback loop.

When applied to black holes, the phenomenon suggests that a black hole bomb could release as much energy as a supernova. What’s more, it wouldn’t even require an external energy source, as the black hole would amplify tiny electromagnetic fluctuations in the vacuum of space, effectively generating energy from background noise.

However, constructing a physical object capable of spinning fast enough to match the frequency of light seemed impossible, leaving the challenge unsolved for decades, until Ulbricht and his team took it on during the COVID-19 lockdown in 2020.

The University of Southampton physicist revealed that he was searching for a meaningful project when he decided to use a rotating aluminum cylinder and magnetic fields to build the first prototype and demonstrate Zeldovich’s feedback loop.

Covid-19 lockdown sparks discovery

To Ulbricht’s amazement, the system showed clear energy amplification, prompting him to immediately assemble a team and develop a more sophisticated version of the experiment.

“I was so super excited that, actually, you could say it rescued me during Covid,” the physicist says. The final setup consists of a spinning aluminum cylinder, surrounded by three layers of metal coils generating a magnetic field that rotates at roughly the same speed as the cylinder.

In this system, the magnetic field plays the role of the light, while the coils act like the mirror, trapping and amplifying the energy. As Zeldovich predicted, the team observed a boosted magnetic signal, effectively creating a miniature black hole bomb.

The team also found that without an initial external magnetic field, the system could spontaneously generate a runaway signal from background noise, mirroring what would happen in a real black hole bomb scenario.

Vitor Cardoso, PhD, a physics researcher at the University of Lisbon in Portugal, explained that having precise laboratory measurements of the process provides strong evidence that the same phenomenon must also occur in black hole physics.

Although the laboratory bomb is a harmless model, it gives physicists a rare opportunity to study superradiance in detail. The researchers believe it could also help test theories involving exotic fields, including those thought to be linked to dark matter.

“If new fields exist, we should be seeing, for instance, gravitational waves being emitted from this cloud around black holes, or we should see black holes spinning down because they’re giving their energy away to these new particles,” Cardoso concludes.

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