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Black Holes' Growth Measured
Tei'ehm Teuw writes: "In an article from NASA@Today.gov, astronomers
are concluding that monstrous black holes weren't
simply born big but instead grew on a measured diet of gas and
stars controlled by their host galaxies in the early formative
years of the universe. These results, gleaned from a
NASA Hubble Space Telescope census of more
than 30 galaxies, are painting a broad picture of a galaxy's evolution and its long
and intimate relationship with its central giant black hole.
Though much more analysis remains, an initial look
at Hubble evidence
favors the idea that titanic black holes co-evolved with the galaxy by trapping a
surprisingly exact percentage of the mass of the central hub of stars and
gas in a galaxy." This seems an affront to my simplistic understanding of black hole behavior, but heck, we're not even sure black holes exist, anyhow.
Sorry, but that's just plain wrong. Any particle created within the event horizon must be created with sufficient kinetic energy to overcome the force of gravity and escape the potential well of the hole.
:-)
:-) that it is the particle with positive energy that escapes, and the one with negative energy that is swallowed. Thus, the net total energy of the hole is reduced, and due to energy-mass equivalnce, it's mass is reduced.
The reason that we cannot see black holes optically, is that light does not have sufficient kinetic energy to escape the gravitaitonal field at a distance outside the event horizon. What you propose here is that particles are created that have supra-light velocity; this is expressly forbidden by relativity.
You are on the right track, however
The theory is that, due to quantum effects, a matter/anti-matter particle pair can spontaneously be created near the event horizon. (This happens in ordinary space all the time, and is permitted by energy conservation, over short time scales).
If the pair is created at the right distance from the horizon, then it is possible that one particle will have sufficient energy to escape, while the other (travelling in the opposite direction) is swallowed by the hole.
It turns out (ie don't ask me to do the maths
Cheers,
Tim
It's official. Most of you are morons.
Great... I can just picture a black hole support group.
Black Hole 1: Hi, I'm Globulax, Swallower of Galaxies... I've been a black hole for billions of years.
Rest of Black Holes (seated on uncomfortable folding chairs): Hi, Globulax!
Black Hole 2: It's okay... we're all Black Holes here... nobody's judging you...
Globulax: <sniffle> Well, I wasn't born big... I was raised on a measured diet of gas and stars controlled by my host galaxy...
Black Hole 2: Don't worry... with time, you'll learn to control your cravings...go on... it's good to let these emotions out...
Globulax: I feel so unwanted... so unloved... even light tries to escape my event horizon... <sob>... and... and... scientists aren't sure if I even exist! Waaaaaaaaaaaaahhhhhhh!!!
Black Hole 2: There, there. It's okay, Globulax. Come on, everybody, let's all give Globulax a big group hug!
The Black Holes sympathetically converge near Globulax. Unfortunately, their gravity is too strong, and they swallow each other into one ultra-massive Super Hole, whose gravity gobbles up everything in the vicinity and rips a large tract of spacetime to shreds...
Black Holes (in unison): Oops!
Black Hole 2: Great... there go our folding chairs...
Stay up hacking each weekend. Sleep is for the week.
A black hole suspended in an absolute vacuum (no matter, no radiation, nothing) will slowly radiate at a temperature which is inversely proportional to its surface area, and thus shrink.
Now let's say we have a black hole and an external background radiation. Black hole now absorbs radiation and grows (but still continue to shrink at the same time). If the temperature of the radiation is greater than that of black hole, the latter would grow faster than it shrinks. Now throw in some matter, and the black hole will grow even faster.
BTW microwaves don't travel 300x the speed of light. Phase velocity can be anything you like, but phase does not "travel".
--
Industrial space for lease in Flatlandia.
As is, black holes have a definite, but not necessarily measurable mass... it's just the mass they started with plus the mass of whatever they have eaten and minus what has been lost to Hawking radiation.
Now, the singularity... yes it does supposedly approach infinite density (approach is an important mathematical distinction), and is even capable of shredding the very Einsteinian laws that define it. The only reason it's tolerated, physicists say (kind of a strange reason, but I don't have the tools to judge) is because the singularity is locked away, and no information can be transmitted about it. The universe doesn't know that there's this strange point at where space-time curvature (gravity) approaches infinity.
To make things really weird, Brian Greene added a nifty component to string theory (which is what gave him credibility for his book besides being a damned good physicist). In the 6 curled dimensions, there is a transformation was allows space to remain continuous, but plants the seed for a black hole... That folding may be part of what keeps the universe from tearing itself apart during black hole formation.
Either way, its pretty nifty how the 'weakest' force in the universe can kick the other three's asses when enough mass is involved....