Vibe Physics: Chatter Overheard at the Physics Water Fountain

Side Question for Google AI:

Is a Penrose blow-up a jet coming from a black hole?

No, a Penrose "blow-up" is not a jet coming from a black hole. They are distinct theoretical concepts related to black holes and general relativity.

Here is a breakdown of what each concept refers to:

Penrose blow-up (or singularity theorem)

• What it is: The Penrose singularity theorem is a mathematical proof in general relativity showing that once matter collapses to a certain point, a spacetime singularity is inevitable. A "blow-up" in this context refers to the point in spacetime where the mathematics breaks down and quantities like density and spacetime curvature become infinite. This signifies the "end of spacetime" according to the theory.
• Location: This singularity is located at the center of the black hole, beyond the event horizon.
• Function: The theorem is a prediction about the internal structure of a black hole, not an external, observable event.

Jets coming from a black hole

• What they are: Jets are powerful, collimated beams of superheated plasma that are ejected at nearly the speed of light from the poles of an active black hole.
• Location: The jets do not originate from the singularity itself. Instead, they are launched from the magnetic and gravitational fields surrounding the black hole's event horizon, in the region of the accretion disk.
• Function: These jets are a mechanism for the black hole system to release excess energy and mass. They can be so large that they stretch across millions of light-years.

The connection: The Penrose process vs. the singularity theorem

It's possible that the confusion arises from another concept named after Roger Penrose: the Penrose process, which is related to the energy that powers black hole jets.

• Penrose process: A theoretical mechanism describing how a particle entering the ergosphere (a region just outside the event horizon of a rotating black hole) could split. One piece falls into the black hole with "negative energy," allowing the other piece to escape with more energy than it had initially, extracting rotational energy from the black hole.
• Powering jets: This process, along with the Blandford–Znajek process, is a proposed explanation for how rotating black holes can fuel their incredibly powerful jets.

In summary, the Penrose singularity theorem describes the theoretical point of infinite density and curvature at the heart of a black hole, while the Penrose process is a theoretical mechanism for extracting energy from a spinning black hole, contributing to the formation of the observed jets. The jets themselves are not the singularity, but rather a byproduct of the extreme physics in the region just outside the event horizon.