Roger Tom, Jim
----- Original Message -----
From: Tom Fowle <[log in to unmask]
To: [log in to unmask]
Date sent: Sat, 13 Feb 2016 18:23:05 -0800
Subject: Re: interesting email about Gravitational waves
Thanks Jim, that's the craziest noise reduction work ever heard
of.
tom fowle WA6IVG
On Fri, Feb 12, 2016 at 08:18:27PM -0800, Jim Gammon wrote:
Got this from a ham friend yesterday.
Gravitational Waves Exist: The Inside Story of How Scientists
Finally Found
Them
By Nicola Twilley
Just over a billion years ago, many millions of galaxies from
here, a pair
of black holes collided. They had been circling each other for
aeons, in a
sort of mating dance, gathering pace with each orbit, hurtling
closer and
closer. By the time they were a few hundred miles apart, they
were whipping
around at nearly the speed of light, releasing great shudders of
gravitational energy. Space and time became distorted, like
water at a
rolling boil. In the fraction of a second that it took for the
black holes
to finally merge, they radiated a hundred times more energy than
all the
stars in the universe combined. They formed a new black hole,
sixty-two
times as heavy as our sun and almost as wide across as the state
of Maine.
As it smoothed itself out, assuming the shape of a slightly
flattened
sphere, a few last quivers of energy escaped. Then space and
time became
silent again.
The waves rippled outward in every direction, weakening as they
went. On
Earth, dinosaurs arose, evolved, and went extinct. The waves
kept going.
About fifty thousand years ago, they entered our own Milky Way
galaxy, just
as Homo sapiens were beginning to replace our Neanderthal
cousins as the
planet’s dominant species of ape. A hundred years ago, Albert
Einstein, one
of the more advanced members of the species, predicted the
waves’ existence,
inspiring decades of speculation and fruitless searching.
Twenty-two years
ago, construction began on an enormous detector, the Laser
Interferometer
Gravitational-Wave Observatory (LIGO). Then, on September 14,
2015, at just
before eleven in the morning, Central European Time, the waves
reached
Earth. Marco Drago, a thirty-two-year-old Italian postdoctoral
student and a
member of the LIGO Scientific Collaboration, was the first
person to notice
them. He was sitting in front of his computer at the Albert
Einstein
Institute, in Hannover, Germany, viewing the LIGO data remotely.
The waves
appeared on his screen as a compressed squiggle, but the most
exquisite ears
in the universe, attuned to vibrations of less than a trillionth
of an inch,
would have heard what astronomers call a chirp—a faint
whooping from low to
high. This morning, in a press conference in Washington, D.C.,
the LIGO team
announced that the signal constitutes the first direct
observation of
gravitational waves.
When Drago saw the signal, he was stunned. “It was difficult
to understand
what to do,” he told me. He informed a colleague, who had the
presence of
mind to call the LIGO operations room, in Livingston, Louisiana.
Word began
to circulate among the thousand or so scientists involved in the
project. In
California, David Reitze, the executive director of the LIGO
Laboratory, saw
his daughter off to school and went to his office, at Caltech,
where he was
greeted by a barrage of messages. “I don’t remember exactly
what I said,” he
told me. “It was along these lines: ‘Holy shit, what is
this?’ ” Vicky
Kalogera, a professor of physics and astronomy at Northwestern
University,
was in meetings all day, and didn’t hear the news until
dinnertime. “My
husband asked me to set the table,” she said. “I was
completely ignoring
him, skimming through all these weird e-mails and thinking, What
is going
on?” Rainer Weiss, the eighty-three-year-old physicist who
first suggested
building LIGO, in 1972, was on vacation in Maine. He logged on,
saw the
signal, and yelled “My God!” loudly enough that his wife and
adult son came
running.
The collaborators began the arduous process of double-, triple-,
and
quadruple-checking their data. “We’re saying that we made a
measurement that
is about a thousandth the diameter of a proton, that tells us
about two
black holes that merged over a billion years ago,” Reitze
said. “That is a
pretty extraordinary claim and it needs extraordinary
evidence.” In the
meantime, the LIGO scientists were sworn to absolute secrecy.
As rumors of
the finding spread, from late September through this week, media
excitement
spiked; there were rumblings about a Nobel Prize. But the
collaborators gave
anyone who asked about it an abbreviated version of the
truth—that they were
still analyzing data and had nothing to announce. Kalogera
hadn’t even told
her husband.
LIGO consists of two facilities, separated by nearly nineteen
hundred
miles—about a three-and-a-half-hour flight on a passenger jet,
but a journey
of less than ten ten-thousandths of a second for a gravitational
wave. The
detector in Livingston, Louisiana, sits on swampland east of
Baton Rouge,
surrounded by a commercial pine forest; the one in Hanford,
Washington, is
on the southwestern edge of the most contaminated nuclear site
in the United
States, amid desert sagebrush, tumbleweed, and decommissioned
reactors. At
both locations, a pair of concrete pipes some twelve feet tall
stretch at
right angles into the distance, so that from high above the
facilities
resemble carpenter’s squares. The pipes are so long—nearly
two and a half
miles—that they have to be raised from the ground by a yard at
each end, to
keep them lying flat as Earth curves beneath them.
LIGO is part of a larger effort to explore one of the more
elusive
implications of Einstein’s general theory of relativity. The
theory, put
simply, states that space and time curve in the presence of
mass, and that
this curvature produces the effect known as gravity. When two
black holes
orbit each other, they stretch and squeeze space-time like
children running
in circles on a trampoline, creating vibrations that travel to
the very
edge; these vibrations are gravitational waves. They pass
through us all the
time, from sources across the universe, but because gravity is
so much
weaker than the other fundamental forces of
nature—electromagnetism, for
instance, or the interactions that bind an atom together—we
never sense
them. Einstein thought it highly unlikely that they would ever
be detected.
He twice declared them nonexistent, reversing and then
re-reversing his own
prediction. A skeptical contemporary noted that the waves
seemed to
“propagate at the speed of thought.”
Nearly five decades passed before someone set about building an
instrument
to detect gravitational waves. The first person to try was an
engineering
professor at the University of Maryland, College Park, named Joe
Weber. He
called his device the resonant bar antenna. Weber believed that
an aluminum
cylinder could be made to work like a bell, amplifying the
feeble strike of
a gravitational wave. When a wave hit the cylinder, it would
vibrate very
slightly, and sensors around its circumference would translate
the ringing
into an electrical signal. To make sure he wasn’t detecting
the vibrations
of passing trucks or minor earthquakes, Weber developed several
safeguards:
he suspended his bars in a vacuum, and he ran two of them at a
time, in
separate locations—one on the campus of the University of
Maryland, and one
at Argonne National Laboratory, near Chicago. If both bars rang
in the same
way within a fraction of a second of each other, he concluded,
the cause
might be a gravitational wave.
In June of 1969, Weber announced that his bars had registered
something.
Physicists and the media were thrilled; the Times reported that
“a new
chapter in man’s observation of the universe has been
opened.” Soon, Weber
started reporting signals on a daily basis. But doubt spread as
other
laboratories built bars that failed to match his results By
1974, many had
concluded that Weber was mistaken. (He continued to claim new
detections
until his death, in 2000.)
Weber’s legacy shaped the field that he established. It
created a poisonous
perception that gravitational-wave hunters, as Weiss put it, are
“all liars
and not careful, and God knows what.” That perception was
reinforced in
2014, when scientists at BICEP2, a telescope near the South
Pole, detected
what seemed to be gravitational radiation left over from the Big
Bang; the
signal was real, but it turned out to be a product of cosmic
dust. Weber
also left behind a group of researchers who were motivated by
their
inability to reproduce his results. Weiss, frustrated by the
difficulty of
teaching Weber’s work to his undergraduates at the
Massachusetts Institute
of Technology, began designing what would become LIGO. “I
couldn’t
understand what Weber was up to,” he said in an oral history
conducted by
Caltech in 2000. “I didn’t think it was right. So I
decided I would go at it
myself.”
In the search for gravitational waves, “most of the action
takes place on
the phone,” Fred Raab, the head of LIGO’s Hanford site, told
me. There are
weekly meetings to discuss data and fortnightly meetings to
discuss
coördination between the two detectors, with collaborators in
Australia,
India, Germany, the United Kingdom, and elsewhere. “When
these people wake
up in the middle of the night dreaming, they’re dreaming about
the
detector,” Raab said. “That’s how intimate they have to
be with it,” he
explained, to be able to make the fantastically complex
instrument that
Weiss conceived actually work.
Weiss’s detection method was altogether different from
Weber’s. His first
insight was to make the observatory “L”-shaped. Picture two
people lying on
the floor, their heads touching, their bodies forming a right
angle. When a
gravitational wave passes through them, one person will grow
taller while
the other shrinks; a moment later, the opposite will happen. As
the wave
expands space-time in one direction, it necessarily compresses
it in the
other. Weiss’s instrument would gauge the difference between
these two
fluctuating lengths, and it would do so on a gigantic scale,
using miles of
steel tubing. “I wasn’t going to be detecting anything on
my tabletop,” he
said.
To achieve the necessary precision of measurement, Weiss
suggested using
light as a ruler. He imagined putting a laser in the crook of
the “L.” It
would send a beam down the length of each tube, which a mirror
at the other
end would reflect back. The speed of light in a vacuum is
constant, so as
long as the tubes were cleared of air and other particles the
beams would
recombine at the crook in synchrony—unless a gravitational
wave happened to
pass through. In that case, the distance between the mirrors
and the laser
would change slightly. Since one beam would now be covering a
shorter
distance than its twin, they would no longer be in lockstep by
the time they
got back. The greater the mismatch, the stronger the wave.
Such an
instrument would need to be thousands of times more sensitive
than any
previous device, and it would require delicate tuning in order
to extract a
signal of vanishing weakness from the planet’s omnipresent
din.
Weiss wrote up his design in the spring of 1972, as part of his
laboratory’s
quarterly progress report. The article never appeared in a
scientific
journal—it was an idea, not an experiment—but according to
Kip Thorne, an
emeritus professor at Caltech who is perhaps best known for his
work on the
movie “Interstellar,” “it is one of the greatest papers
ever written.”
Thorne doesn’t recall reading Weiss’s report until later.
“If I had read it,
I had certainly not understood it,” he said. Indeed,
Thorne’s landmark
textbook on gravitational theory, co-authored with Charles
Misner and John
Wheeler and first published in 1973, contained a student
exercise designed
to demonstrate the impracticability of measuring gravitational
waves with
lasers. “I turned around on that pretty quickly,” he told
me.
Thorne’s conversion occurred in a hotel room in Washington,
D.C., in 1975.
Weiss had invited him to speak to a panel of NASA scientists.
The evening
before the meeting, the two men got to talking. “I don’t
remember how it
happened, but we shared the hotel room that night,” Weiss
said. They sat at
a tiny table, filling sheet after sheet of paper with sketches
and
equations. Thorne, who was raised Mormon, drank Dr Pepper;
Weiss smoked a
corncob pipe stuffed with Three Nuns tobacco. “There are not
that many
people in the world that you can talk to like that, where both
of you have
been thinking about the same thing for years,” Weiss said. By
the time
Thorne got back to his own room, the sky was turning pink.
At M.I.T., Weiss had begun assembling a small prototype detector
with
five-foot arms. But he had trouble getting support from
departmental
administrators, and many of his colleagues were also skeptical.
One of them,
an influential astrophysicist and relativity expert named
Phillip Morrison,
was firmly of the opinion that black holes did not exist—a
viewpoint that
many of his contemporaries shared, given the paucity of
observational data.
Since black holes were some of the only cosmic phenomena that
could
theoretically emit gravitational waves of significant size,
Morrison
believed that Weiss’s instrument had nothing to find. Thorne
had more
success: by 1981, there was a prototype under way at Caltech,
with arms a
hundred and thirty-one feet long. A Scottish physicist named
Ronald Drever
oversaw its construction, improving on Weiss’s design in the
process.
In 1990, after years of studies, reports, presentations, and
committee
meetings, Weiss, Thorne, and Drever persuaded the National
Science
Foundation to fund the construction of LIGO. The project would
cost two
hundred and seventy-two million dollars, more than any
N.S.F.-backed
experiment before or since. “That started a huge fight,”
Weiss said. “The
astronomers were dead-set against it, because they thought it
was going to
be the biggest waste of money that ever happened.” Many
scientists were
concerned that LIGO would sap money from other research. Rich
Isaacson, a
program officer at the N.S.F. at the time, was instrumental in
getting the
observatory off the ground. “He and the National Science
Foundation stuck
with us and took this enormous risk,” Weiss said
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