Chandra 'Hears' A Black Hole

The Reuters article had some additional information that is helpful to this
discussion:



When scientists trained the Chandra observatory on the center of Perseus
last year, they saw concentric ripples in the cosmic gas that fills the
space between the galaxies in the cluster.
"We're dealing with enormous scales here," Fabian said in a telephone
interview. "The size of these ripples is 30,000 light-years."

Fabian said the ripples were caused by the rhythmic squeezing and heating of
the cosmic gas by the intense gravitational pressure of the jumble of
galaxies packed together in the cluster.

As the black hole pulls material in, he said, it also creates jets of
material shooting out above and below it, and it is these powerful jets that
create the pressure that creates the sound waves.

To scientists, he said, pressure ripples equate to sound waves. By
calculating how far apart the ripples were, and how fast sound might travel
there, the team of researchers determined the musical note of the sound.

http://www.cnn.com/2003/TECH/space/0...eut/index.html



1. I think that the scientists observed the 30,000 light year ripples,
estimated the velocity of sound in the gas, and deduced the frequency.

2. Although a stretch, I do think they can technically classify this as
sound. The definition of according to Merriam Webster: "mechanical radiant
energy that is transmitted by longitudinal pressure waves in a material
medium (as air) and is the objective cause of hearing". These are pressure
waves in a gas, so if you were in the cosmic gas, could hear that low, and
could live for 20 million years to listen to the entire period, then sure,
you would hear sound. =)

Matthew F Funke replied to Jeff Root:

Middle C has a frequency of 261.63 Hz. The B-flat just below
it has a frequency of 233.08 Hz. An octave is a doubling or
halving of frequency, so 57 octaves below the B-flat just below
middle C is 1.6 e-15 Hz, if I calculated correctly. That is a
period of 618,307,825,964,715 seconds, or 19,592,992 years,
again if I calculated correctly.

A bit generous with our precision, aren't we?

At the time I wrote the message I determined the probability
of anyone commenting on the level of precision to be 41.26% if
Matthew Funke didn't read it, or 76.14% if Matthew Funke did
read it. I gamboled and lost.

Actually, I was parsimonious with my editing rather than
generous with precision. I could have edited the values to
some number of significant digits. That would have required
deciding how many significant digits to retain, and how to
round the least significant digit. I hate making decisions.
So I just truncated the result of the second calculation to
integer seconds, and that of the third to integer years.
I knew that everyone but the registered kooks would
understand, and that the kooks wouldn't be interested.
That left only Matthew Funke to make a comment, just as I
predicted a week from last Wednesday. Zetas left again!

Makes no sense to me.

Well, sound waves are just longitudinal pressure waves
through a medium, yes?

I'll buy that. Is it on audio CD?

In a sense, what this black hole is throwing out could be seen as
such (as the original article stated, "ripples in the gas filling
the cluster")... though a period of 19.6 million years seems to
stretch the idea of "sound" to the breaking point. -=shrug=-

A barrier to my comprehension was that I hadn't bothered to
read the info in the links. One of the articles you just
gave a link to says the sound waves "sweep across hundreds of
thousands of light years." I hadn't imagined that sound could
propagate that far. I was imagining something on the scale of
a solar system. I don't think it would be possible to observe
sound waves with a period of 19.6 million years in a space as
small as a solar system.

The new barrier is incomprehension that sound waves could go
so far and last so long.

-- Jeff, in Minneapolis

..

Well, sound waves are just longitudinal pressure waves through a
medium, yes? In a sense, what this black hole is throwing out could be
seen as such (as the original article stated, "ripples in the gas
filling the cluster")... though a period of 19.6 million years seems to
stretch the idea of "sound" to the breaking point. -=shrug=-

If a black hole made a sound in the universe, and no one could ever
hear it, did it really make a sound....WOW....Deep dude!

I agree though. I think this is NASA's attempt once again to stretch
the truth to get headlines. The latest Astronomy has an interview with
the Professor of Physics at Columibia (if I recall correctly). He
complains of the same thing. I've got five bucks that at my clubs
public star party on Sat I am going to have to explain this to at
least one member of the public who know believes that a black hole is
playing Jimi Hendrix tunes from the other end of the universe. Oh
well, at least it gets science some attention.

Matt

On 10 Sep 2003 07:27:32 -0700, in sci.astro, (Jeff Root)
wrote:

Bob Officer replied to Jeff Root:

Middle C has a frequency of 261.63 Hz. The B-flat just below
it has a frequency of 233.08 Hz. An octave is a doubling or
halving of frequency, so 57 octaves below the B-flat just below
middle C is 1.6 e-15 Hz, if I calculated correctly. That is a
period of 618,307,825,964,715 seconds, or 19,592,992 years,
again if I calculated correctly.

Makes no sense to me.

Sound = pressure waves = mechanical/kenetic energy...

They are observing a periodic pressure wave... as the gases are
flowing outward from the black hole. Calling such pressure waves

Did you accidentally omit the word "sound" at this point?

I did... Thanks, Jeff. I was looking for a way to describe the observations
other than use the word sound...


is not really accurate...

Sound is a mechanical wave, so them calling this periodic wave
sound is really reaching.

I assume that they know what sound is and what it isn't. Since
they call it "sound", I assume it is a correct use of the term.

Are they sure the wave is mechanical in nature? and not the variation of
EMF waves being the cause. The base cause could the prior
expansion/contraction of the parent star prior to collapse.

What makes no sense to me is: How can it have a period of
19 million years?

That why I dislike the term sound...


--
Aktohdi

Jeff Root wrote:
Matthew F Funke replied to Jeff Root:

Middle C has a frequency of 261.63 Hz. The B-flat just below
it has a frequency of 233.08 Hz. An octave is a doubling or
halving of frequency, so 57 octaves below the B-flat just below
middle C is 1.6 e-15 Hz, if I calculated correctly. That is a
period of 618,307,825,964,715 seconds, or 19,592,992 years,
again if I calculated correctly.

A bit generous with our precision, aren't we?

At the time I wrote the message I determined the probability
of anyone commenting on the level of precision to be 41.26% if
Matthew Funke didn't read it, or 76.14% if Matthew Funke did
read it. I gamboled and lost.

As long as we're both feeling playful.
("Gambol" versus "gamble".)

Makes no sense to me.

Well, sound waves are just longitudinal pressure waves
through a medium, yes?

I'll buy that. Is it on audio CD?

If you were happy with the resolution afforded per sample on CD, and
your CD was large enough(*), there's no reason it couldn't be encoded on
audio CD. But the fact that it could be encoded on audio CD does not, in
and of itself, dictate whether or not the phenomenon recorded is sound.

Various bits of information we have about recording periodic
phenomena, however -- most notably the Nyquist theorem -- suggests that we
wouldn't need to hsave samples anywhere near the usual audio CD rate in
order to preserve the waveform accurately, if we wanted to store it
digitally. (The reason audio CDs sample so much faster is due, in large
part, to the fact that our ears require substantially less than 19.6
million years to detect a change in the frequency of sound.)

(*) 618 trillion seconds times 44100 samples per second -- typical
for an audio CD -- makes a lot of samples. And that's just for one
period. You'd need a big CD, and a big CD player.
--
-- With Best Regards,
Matthew Funke )

In message , Dean
writes
1. I think that the scientists observed the 30,000 light year ripples,
estimated the velocity of sound in the gas, and deduced the frequency.

I thought this too, but my calculations give a speed around a few
hundred km per second - which is several orders of magnitude above Mach
1, but still hundreds of times slower than c. What assumptions were
they making here?

--
Mike

In message , Dean
writes
1. I think that the scientists observed the 30,000 light year ripples,
estimated the velocity of sound in the gas, and deduced the frequency.

I thought this too, but my calculations give a speed around a few
hundred km per second - which is several orders of magnitude above Mach
1, but still hundreds of times slower than c. What assumptions were
they making here?

--
Mike

"Jeff Root" wrote in message om...

. . .
The new barrier is incomprehension that sound waves could go
so far and last so long.

-- Jeff, in Minneapolis

The article does use the "sort of" marks (read the title,
Chandra *sort of* Hears A Black Hole) and mentions
that the frequency is far below what the human ear can
hear.

As for going so far for so long... perhaps we can conclude
that black holes are...

*R*E*A*L*L*Y* *R*E*A*L*L*Y* *L*O*U*D* ...(?)

g

happy days and...
starry starry nights!

--
"Oh give me please the Universe keys
That unlock all those mysteries!"
You pay your fees, you find some keys
That keeps you always groping.

"Oh give me please the Happiness keys
That ease the pain of biting fleas!"
Today you seize you need no keys,
That door is always open.

Paine Ellsworth

"Jeff Root" wrote in message om...

. . .
The new barrier is incomprehension that sound waves could go
so far and last so long.

-- Jeff, in Minneapolis

The article does use the "sort of" marks (read the title,
Chandra *sort of* Hears A Black Hole) and mentions
that the frequency is far below what the human ear can
hear.

As for going so far for so long... perhaps we can conclude
that black holes are...

*R*E*A*L*L*Y* *R*E*A*L*L*Y* *L*O*U*D* ...(?)

g

happy days and...
starry starry nights!

--
"Oh give me please the Universe keys
That unlock all those mysteries!"
You pay your fees, you find some keys
That keeps you always groping.

"Oh give me please the Happiness keys
That ease the pain of biting fleas!"
Today you seize you need no keys,
That door is always open.

Paine Ellsworth

Painius wrote,

The article does use the "sort of" marks
(read the title, Chandra *sort of* Hears A Black Hole) and mentions
that the
frequency is far below what the human
ear can hear.

As for going so far for so long... perhaps
we can conclude
that black holes are...
=A0=A0=A0=A0=A0=A0=A0=A0*R*E*A*L*L*Y* *R*E*A*L*L*Y*
*L*O*U*D* ...(?)
g

Paine, remember a few months back we were discussing gravity waves, and
how they should more aptly be defined as *spatial acoustic pressure
waves* in the spatial medium..? Serendipitously, the Chandra images are
clearly showing this.
But the compression-rarefaction signature is being
passed off as "sound" energy propagating thru interstellar gas.. and
that gas is more rarified than the best man-made vacuum.
O well. Anything to maintain the void-space
paradigm, huh? oc

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