Penrose trial

The Penrose process , theorized by Roger Penrose in 1969 , states that energy can be extracted from a rotating black hole . This is possible because the rotational energy of a rotating black hole is outside the event horizon , in the region of the ergosphere .

The Penrose process can be illustrated by a simple example: A particle is thrown with a four-pulse in the direction of rotation of the black hole. The energy of this particle is ${\displaystyle p_{a}}$

${\displaystyle E_{0}=-p_{0}^{a}\xi _{a}}$

This energy of the particle remains constant during the fall into the black hole. When entering the ergosphere, the particle decays into a particle with additional positive angular momentum and energy and a particle with negative angular momentum and energy. Conservation of angular momentum and energy state that:

${\displaystyle p_{0}^{a}=p_{P}^{a}+p_{N}^{a}}$

If one also contracts this equation , then the following also applies: ${\displaystyle \xi _{a}}$

${\displaystyle E_{0}=E_{P}+E_{N}}$, in which ${\displaystyle E_{N}<0}$

The particle with positive angular momentum and energy escapes the ergosphere, whereas the particle with negative angular momentum and energy falls into the black hole. To an outside observer, this appears like extracting energy from the black hole there . The mass of the black hole reduces to , which means that an energy has been extracted from the black hole . ${\displaystyle E_{P}>E_{0}}$ ${\displaystyle M-|E_{N}|}$ ${\displaystyle E_{N}}$

In 1971 Jakow Seldowitsch transferred the postulated effect to the case of a rotating absorber such as a metal cylinder, which is hit by a “classic” (i.e. mechanical) wave. The incident wave should then gain energy upon reflection if the rotation frequency of the cylinder is higher than the frequency of the wave, which could be confirmed experimentally in 2020 in the case of sound waves .

See also

• Lense thirring effect
• Kerr metric

Individual evidence

1. ^ ^{A b} Robert Wald: General Relativity . University of Chicago Press ,, ISBN 0-226-87033-2 .
2. ↑ Amplification of waves from a rotating body www.nature.com, published June 22, 2020, accessed June 28, 2020
3. ↑ Physicists Verify Half-Century-Old Theory about Rotating Black Holes www.sci-news.com, June 24, 2020