Black Hole Harmonics

SPEAKER_1 (0:00)

This episode is brought to you by Accenture. When you're advertising operations fall out of sync, everything else follows. Spotify and Accenture are working together to reinvent the rhythm of ad sales. Using automation, analytics, and smarter workflows to simplify campaign delivery and access better data across the business. The result? Less time spent on operations, more time connecting brands with the moments and fandoms that matter most. Learn more at accenture.com/spotify.

SPEAKER_2 (0:31)

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Matt O'Dowd (1:00)

Thank you to brilliant.org for supporting PBS Digital Studios. Black holes are crazy enough on their own, but crash two together and you end up with this roiling blob of inescapable space that vibrates like a beaten drum. And the rich harmonics of those vibrations seen through gravitational waves could hold the secrets to the fabric of space time itself. Today on Space Time Journal Club, we'll explore two papers that claim to have detected black hole harmonics. We'll also give you the latest updates on the most recent, and in some cases quite bizarre, LIGO detections.

When physicists talk about black holes, they're usually referring to highly theoretical objects. Static, unchanging black holes viewed from infinitely far away.

This makes everything clean and simple enough to attempt the already notoriously complex calculations of black hole physics.

But real black holes are created in the violent deaths of massive stars, and there's nothing clean about that. We now know that black holes also merge, and in the process produce gravitational radiation that we've only just managed to detect with the miraculous work of the LIGO and Virgo gravitational wave observatories. In the instant after its merger, the new joined black hole looks nothing like the idealized theoretical black hole. Imagine it. Two event horizons. Two roughly spherical black surfaces that are literal boundaries to our universe. They spiral together and touch, instantly becoming a single surface. Technically, in that instant we go from two black holes to one.

But in the beginning, this new black hole looks nothing like its progenitors. It's not even close to spherical, is dumbbell-shaped, and then it's an elongated blob, and then it's an oscillating spheroid, like a ball of water wriggling in space. But what exactly is oscillating here? The event horizon seems to define the surface of the black hole, but it's really the fabric of space time itself that's vibrating. The two in-spiraling black holes make powerful space-time ripples, gravitational waves, which intensify as the black holes approach merger, only becoming observable in the last fraction of a second. And then the merged black hole continues to radiate these space-time ripples as it oscillates. But these quickly die away as the black hole settles into its final static form. This final phase is called the ring-down, an expression that comes from the analogy with a bell. When struck, a bell vibrates with many different frequencies, many overlapping harmonics. As those vibrations give up their energy, in this case to sound waves, the vibrations fade and the bell rings down. A struck black hole also vibrates with many different frequencies.

SPEAKER_1 (4:00)

This episode is brought to you by Accenture. When your advertising operations fall out of sync, everything else follows. Spotify and Accenture are working together to reinvent the rhythm of ad sales, using automation, analytics and smarter workflows to simplify campaign delivery and access better data across the business. The result? Less time spent on operations, more time connecting brands with the moments and fandoms that matter most. Learn more at accenture.com/spotify.

SPEAKER_2 (4:31)

When you need to build up your team to handle the growing chaos at work, use Indeed Sponsored Jobs. It gives your job post the boost it needs to be seen and helps reach people with the right skills, certifications and more. Spend less time searching and more time actually interviewing candidates who check all your boxes. Listeners of this show will get a $75 sponsored job credit at indeed.com/podcast. That's indeed.com/podcast. Terms and conditions apply. Need a hiring hero? This is a job for Indeed Sponsored Jobs.

Matt O'Dowd (5:00)

Different harmonic frequencies. The harmonics of a vibrating sphere, be it a blob of water in zero G or a black hole, are analogous to the harmonics of a vibrating guitar string or piano wire.