The Sound of a Black Hole

Snags writes "Astronomers have used the Chandra X-ray Observatory to observe the deepest, lowest-frequency sound waves ever observed. By my calculations, the 'B-Flat 57 octaves below middle-C' has a period of 9.8 million years. Despite arguments that explosions in space movies should be silent, it is legitimate to call these sound waves because at that frequency, particles of space dust can 'see' each other through gravity. These notes are 'over a million billion times deeper than the limits of human hearing', so to call it infra-sound would be a bit of an understatement."

Comments

Wow - and I thought Germany had a long concert

[MerlynEmrys67]

bbc.co.uk

So this is a 639 year concert that has started in Germany. The concert has been ongoing for 17 months (the initial "quiet period" of the organ filling) however the first three note chord has been hit.

Boy wish I had that kind of time to waste... Imagine the monks 630 years from now going - "Well, this is over now - what the hell are we going to do now ?"

On the team

[xiox]

I'm on the team that did this. Ask any questions you like!

Do black holes exist?

[nimblebrain]

Black holes rely on an assumption that gravity has no limits on its strength, and to some extent on it following a strict Newtonian curve.

Thinking of "curves" in space-time is an interesting analogy for gravity, but still doesn't address the mechanism - sure, the planet may be on a "45 degree" incline in spacetime, but what forces it down... and not up? You would nearly have to posit the existence of some constant stream of gravitons coming at 'right angles' to three-dimensional space in order to actually push things 'down the well'.

There are alternate corpuscular (i.e. caused by particles; "quantum") models of the mechanism of gravity. There's the LeSagian model, with modern reworks that range from the bizarre-yet-possible theories of Tom Van Flandern, to the more "moderate" theories of Paul Stowe explaining how the "drag" factor that detractors expect doesn't show up, in exactly the sort of way that Feynman expressed it for electromagnetism.

The LeSage-type theories are, in general, "push" theories, which operate in a medium filled with gravitons (just as space is filled with photons) that are deflected/absorbed near bodies and cast 'shadows' that create a low "pressure" area close to surfaces and, to a lesser extent, between bodies.

The formulae calculate out approximately to Newton's/GR's gravity equation, but with some interesting exceptions:

• There is a stronger fall-off at greater distances, which limits the effective range of gravity (surprisingly, this reduces the need for 'dark matter' to keep galaxies in the shape they're in)
• Inside denser and denser bodies, graviton absorption reaches a point where matter on the inside hardly contributes at all (a complete gravity "shadow")

This upper limit on the strength of gravity may prevent the ultimate collapse that black hole theory requires.

Black holes are still a theoretical construct. Even the jets, now often taken as a 'sign' of a black hole, are still a largely unexplained phenomenon, one that is also associated with accretion disks for newly-forming stars.

So if something's singing in that cloud, it may not be as dense as it's accused of being.

I apologize for all the jargon. I shall go read another thread on SCO as just punishment :)

Re:Do black holes exist?

[krysith]

Doesn't a stronger fall off at greater distances actually go against the data we have for anomalous gravitational effects? If anything, both cosmological ("dark matter") and experimental data point to gravity being stronger than Newton at long distances.

See also:
"Study of the anomalous acceleration of Pioneer 10 and 11", Anderson, J.D., Laing, P.A., Lau, E.L., Liu, A.S., Nieto, M.M., and Turyshev, S.G., Physics Review D, v65, 082004, (2002)

Re:This would be a "RTFA". It *is* sound.

[xiox]

That's right. We see the ripples as X-ray emission is very sensitive to gas density (goes like density squared), so we see the dense regions where the gas is being compressed by the sound wave. The picture is a "snapshot" as we never see the wave move.