Duncan Alfreds

Cape Town - A University of Chicago professor studying black holes says they are an important phenomenon and may lead to new understanding of the nature of the "real universe".

"They (black holes) are interesting objects from a fundamental physics point of view and play an important role in astrophysics processes. They help us to understand what's going on in the real universe," Bob Wald told News24 after his lecture at UCT.

A black hole is a region of spacetime where gravity is so strong that nothing - not even light - can escape. They arise in nature as the end products of the complete gravitational collapse of sufficiently massive bodies like stars.

"There are black holes at the centre of most galaxies, and the one at the centre of our galaxy is about four million solar masses," said Wald, who is in SA for the first time, and just recently hiked up Table Mountain.

However, despite being a "perfect absorber of everything", black holes do not swallow up the galaxy because of the speed of bodies around it, much like the Earth doesn't not fall into the sun, despite the latter's gravity.

Observations

"Black holes have a finite temperature, despite their gravity. One would think that their temperature should be absolute zero (-273.15°C) but they are subject to quantum effects.

"Given that black holes have a finite temperature, they should evaporate in a finite amount of time," said Wald.

He said that much of the theory around the study of black holes was developed by physicist Stephen Hawking and hopes that observations of black holes will confirm the theory of general relativity.

"I'm still excited by black holes, there's still much to be learned and it might teach one about what's going on. We need to fill in the details of astro-physical processes."

Most remarkable of the theoretical developments is the relationship between certain laws applying to black holes and the ordinary laws of thermodynamics, particularly the fact that - due to quantum processes - black holes "emit" thermal radiation.

Wald said study of physics and cosmology was a popular field of study in the US and attracted good students, illustrating the difference between the industrialised economy and SA as a developing country where there was a chronic shortage of skills.

"The gravitational waves results in about five years excites me - it would be good to confirm the theory. What is needed is a theory that includes general relativity and quantum theory, but there are special difficulties when one tries to formulate a quantum theory of gravity."

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## Comments

I would have loved to have attended this lecture!

We know a lot more about black holes right here in SA. The gravity theory seems to be correct too.

Blackholes? Hmm, has it got anything to do with governance and funds?

The statement that the theory of general relativity must be confirmed is not correct; the theory has been confirmed thousands of times and holds every time. Perhaps what is still needed is final proof of the actual existence of black holes, because up to now they can only be inferred through their gravitational action on surrounding matter, e.g. in binary star systems. The main difficulty why it is still very difficult to combine general relativity and quantum mechanics, while each functions extremely accurately in its own domain, is the Heisenberg uncertainty principle which was never factored into the formulation of general relativity. But then again, that is because Heisenberg was a mere boy in 1915 when Einstein proposed general relativity. And Einstein never bought into the Heisenberg theory of the probabilistic nature of matter particles -- Einstein said "God does not play dice", and signalled his rejection of the theory.

*lol* --- we cannot even see the closest star to us properly. How in the world are they going to study an imaginery object?

Thats why he is in SA to study how Funds disappear with our own ANC black hole. Interesting

Seriously guys. Can there not be ONE News24 article that does not have anti-government or racist comments posted afterwards? Corrupt politicians are all over the world, not just here, so please get over it.

Black holes exist in profusion, and remarkably good images in various spectra have been made for years. But so what? They're a normal, natural phenomenon well within the bounds of known physics. What's REALLY interesting is what gravity is; we know zilch about it except some of its effects. Any news of the inter-planetary satellite experiment to try to detect gravity waves and their rate of propagation?

"Given that black holes have a finite temperature, they should evaporate in a finite amount of time," said Wald.

Milky Way’s Giant Black Hole Awoke from Slumber 300 Years Ago

@Robert Matzdorf and Juan Valdez: Quite right we know nearly zilch about gravity, which Newton described as "a force" but which Einstein some 300 years later described as NOT being a force, but rather a consequence of matter warping space (and time) around itself! Go figure. There is yet no news of really deep interest about the inter-planetary satellite experiment to detect gravitational waves and their rate of propagation;general relativity predicts that those waves travel at the speed of light (about 370 000kms a second)and are released by any non-quiescent gravitating body, hence they are so very difficult to detect! About black holes having a finite temperature and the "ability" to evaporate in a finite time -- well, the phenomenon is very close or similar to the second law of thermodynamics, which can be simplified as saying that disorder in any closed system tends to increase with time. Black hole evaporation is disorder -- I simply do not get the statement that the Milky Way's Giant (central??) black hole "awoke from slumber 300 years ago" -- the concept of black holes is comparatively new, dating back to only 1970 when phycist/mathematician Roger Penrose first came with a solid proposal about their existence, so 300 years ago -- in Newton's time -- nobody knew of black holes! Mitchell and La Place only spoke of "compact" stars from which "light corpuscles" could not escape.