The golden anniversary of black-hole singularity

October 1, 2015
Milkyway Black Hole . Credit: Ute Kraus, Universität Hildesheim

When a star collapses forming a black hole, a space-time singularity is created wherein the laws of Physics no longer work. In 1965 Sir Roger Penrose presented a theorem where he associated that singularity with so-called ''trapped surfaces'' that shrink over time. That hypothesis -one of the results of the general theory of relativity- is now celebrating its anniversary.

Exactly 50 years ago, the physicist and mathematician Sir Roger Penrose, currently Professor Emeritus at the University of Oxford (United Kingdom), formulated a in which he associated two concepts related to relativity. One of these concepts is gravitational singularity, an 'error' in space-time where physical quantities cannot be defined.

The other concept is that of so-called ''trapped surfaces'', areas that inevitably shrink over time. These surfaces are formed by the explosion of a star at the end of its life, thus causing its collapse and the subsequent formation of a black hole. At that moment, a gravitational singularity is created where time ceases to exist and the laws of known Physics can no longer be applied.

Penrose's theorem relates both concepts and is considered the first major mathematically rigorous result of Einstein's general theory. Shortly after presenting his theorem, Penrose and the acclaimed Stephen Hawking tested another theorem which indicates that an expanding universe -such as ours- must have its origin in an instantaneous singularity: the Big Bang, the mysterious initial state which has infinite density.

''What these two theorems are saying is that the general theory of relativity predicts the existence of singular and catastrophic occurrences, such as that which happens inside a black hole or the great initial expansion of the universe, under certain physically reasonable conditions," explains José M. M. Senovilla, theoretical physicist at the University of the Basque Country and co-author of a study concerning these theorems.

"But they also indicate that Einstein's theory includes and describes its own limitations -he adds-, since said theory no longer seems valid in certain situations under extreme conditions due to the occurrence of totally unacceptable 'infinite' singularities".

The theorems in and of themselves do not imply that catastrophic events such as have to occur. Singularity could be averted if the hypotheses of the theorem were nullified. "An example in which this would occur would be if the energy density of the entire Universe were, on average, null; but the problem is that this case seems to be highly unrealistic, so singularities prevail," the researcher notes.

Senovilla's study on Penrose's theorem has been published in the journal 'Classical and Quantum Gravity' along with 12 other articles highlighting the milestones that mark 100 years of Einstein's General Theory of Relativity, the one-hundredth anniversary of which is also celebrated in 2015.

Explore further: Seeking proof for the no-hair theorem

More information: José M. M. Senovilla and David Garfinkle. "The 1965 Penrose singularity theorem". Classical and Quantum Gravity 32: 124008, 2015. iopscience.iop.org/article/10. … 64-9381/32/12/124008

Related Stories

Seeking proof for the no-hair theorem

September 9, 2014

According to general relativity, a black hole has three measurable properties: mass, rotation (angular momentum), and charge. That's it. If you know those three things, you know all there is to know about the black hole. ...

Penrose's and Hawking's early math award revisited

November 18, 2014

In 1966, it was Roger Penrose who won the prestigious Adams Prize for his essay "An analysis of the structure of space-time." The Adams Prize – named after the British mathematician John Couch Adams – is awarded each ...

Theorists apply loop quantum gravity theory to black hole

May 31, 2013

(Phys.org) —Physicists Rodolfo Gambini and Jorge Pullin of University of the Republic in Montevideo, Uruguay, and Louisiana State University respectively, have applied the theory of Loop Quantum Gravity (LQG) to a simplified ...

Researcher shows that black holes do not exist

September 24, 2014

Black holes have long captured the public imagination and been the subject of popular culture, from Star Trek to Hollywood. They are the ultimate unknown – the blackest and most dense objects in the universe that do not ...

Recommended for you

Solar minimum surprisingly constant

November 17, 2017

Using more than a half-century of observations, Japanese astronomers have discovered that the microwaves coming from the sun at the minimums of the past five solar cycles have been the same each time, despite large differences ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.