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05/09/2000
Anniversary and Decimal Places
This week marks the first anniversary of Dr. Bortrum''s columns
for stocksandnews.com. I feel comfortable in referring to
Bortrum in the third person inasmuch as he is my alter ego, born
when I decided to use a nom de plume for this journalistic
endeavor. (After using the term alter ego, I found the dictionary
gives one definition as "another aspect of oneself", just what I
meant!) Over the course of the past year, I have learned a lot
from Bortrum about subjects ranging from Viagra and harmful
algae to quarks, gluons and black holes. Bortrum has had the
temerity to write about topics that I would never consider for my
own scientific papers. He also has occasionally injected bits of
humor in his columns; at least I found them humorous although
my wife occasionally has disagreed.
Back in my semiconductor days at Bell Labs, I once did an
experiment that lasted 98 or 99 days and got the best data I had
ever obtained in that particular area. In the paper I submitted to
the Journal of The Electrochemical Society, I threw in a
statement that it would have been aesthetically more pleasing to
have run the experiment for an even 100 days. However, I noted,
there was a predicted thunderstorm and I cut the experiment
short in case the thunderstorm caused a power failure and shut
down my furnace. By accident, I received the signed copy of the
referee''s report, usually anonymous. The referee was an
esteemed member of the electrochemical community and in fact
was a past president of The Electrochemical Society. He said
that my flippant remark about the 100 days, etc. had no place in a
scientific publication and downgraded my manuscript from a full
paper to a mere technical note! You can understand why I am
delighted that Bortrum can deal with science in a more casual
manner.
As I mentioned above, one topic Bortrum treated was black
holes. I didn''t realize just how well accepted and understood the
concept is by the general public until last week. In the daily
comic strip "Over the Hedge" the raccoon and the turtle were
discussing black holes and there was a depiction of one,
complete with a sign designating the Event Horizon! I had no
idea that nonhuman members of the animal kingdom, let alone
the cartoonists who draw them could relate to such a wondrous
cosmological entity. Last week was National Cartoonists Week
so my belated best wishes to our Lamb creator, Harry Trumbore.
The concept of the black hole, you may recall, arose out of the
work of Albert Einstein. Regular readers of Bortrum''s columns
cannot have escaped my veneration of Einstein as my scientific
hero. Hardly a day goes by that someone isn''t preparing to or
actually trying to either confirm or debunk one or another of
Einstein''s tenets or conclusions. A central idea in his relativity
theories is the simple hypothesis that the velocity of light is the
same no matter what the source. Well, Kenneth Brecher of
Boston University recently put this idea to the test and claims to
have found that this is indeed very very true. In fact, an article in
the April 28th issue of Science cites Brecher as proving it''s true
at least out to 20 decimal places! I can''t imagine being able to
measure anything that precisely. What Brecher did was to
measure the light arriving from very distant celestial events
known as "gamma ray bursts". Gamma rays are photons, but not
optically visible photons, with higher energies than X-rays. The
origin of these very intense bursts of gamma rays, lasting small
fractions of a second, is not known. However, they are quite
common and, with present day detectors, the chances are good
that you can see one a day coming from somewhere in the sky.
The bursts appear to be one-shot deals, however, each burst
coming from a different part of the sky.
Brecher''s thesis is that such intense energies must be associated
with chunks of matter flying through space in different directions
at immense speeds approaching the velocity of light. Without
Einstein, one might naively think that if a light source is moving
rapidly toward you the light might get to you faster than if
another source, at the same location, was moving in the opposite
direction when it emitted the light. What Brecher did was to
analyze the shape of the intensities of these bursts as a function
of time. That is, if you''re recording the "brightness" of the
gamma ray burst on paper or on a photographic film, how sharp
is the peak that you measure? What Brecher concludes from his
analysis is that any differences in the speed of light must be less
than 3 billionths of a millimeter per second. If you divide this by
the speed of light of 30 billion centimeters per second it comes
out that any variation has to be in the 20th decimal place or
more. I''m somewhat relieved to find that Brecher apparently did
not actually measure the speed of light out to 20 decimal places.
Instead, he''s saying that, whatever it is, it''s the same at least out
to the 20th place.
Bortrum felt up to the task of discussing dark matter by his third
column. Dark matter is still in the news. In a recent column
Bortrum discussed work claiming that the WIMP, a postulated
particle for dark matter, has been identified. On the same page
of the issue of Science cited above, there is an example of dark
matter and its importance in contributing to the weight of
galaxies. This study by Wyn Evans and Mark Wilkinson, two
British astronomers, concludes that, contrary to what has been
thought for years, our own Milky Way galaxy is heavier than our
neighboring Andromeda galaxy. The reason Andromeda has
been thought to be heavier than our own familiar galaxy is
because Andromeda is bigger and brighter and has more clusters
of stars than we do. What Evans and Wilkinson did was to focus
on distant objects outside Andromeda and calculate how fast they
were spinning around that galaxy. They now have measurements
on 40 or so objects ranging from clusters of stars to tiny dwarf
galaxies. By concentrating on objects that are well outside the
bulk of the galaxy, they calculate the mass of the galaxy that
must be present to hold the objects in their orbits. I presume the
calculation would be akin to calculating the mass of the earth
from the orbit of the moon. At any rate, they conclude that
Andromeda has a mass of slightly more than one trillion solar
masses, about half the mass of the Milky Way. This is
surprising, if true, since it means that the amount of dark matter
surrounding Andromeda is much less than expected.
Both of the above studies have those skeptical of the conclusions,
as it is with any major finding these days. So, we''ll keep tuned
for any new developments.
Back to Einstein, there is a major multi-year effort going on to
test another of his conclusions. This effort is being launched in
Livingston, Louisiana to the tune of hundreds of millions of
dollars. The impressive name of the facility is the Laser
Interferometer Gravitational-Wave Observatory, more simply
known as LIGO. The objective of the LIGO endeavor is to
detect gravitational waves. Einstein''s general relativity theory
predicts that huge events such as two black holes colliding,
supernovas and other major disruptions should produce a
distortion in space-time that would propagate throughout the
universe as a wave. These waves have not been detected as yet,
although Russell Hulse and Joseph Taylor have inferred them in
some Nobel Prize-winning work. Russ and Joe found two
neutron stars that are engaged in a death spiral around each other,
the consummation of which will occur a couple hundred million
years from now. The rate at which they are spiraling together
turns out to match the rate due to the predicted loss of
gravitational energy from Einstein''s general relativity theory -
hence the Nobel Prize. I can''t help repeating how astounded I
am that Einstein himself never got the Nobel Prize for relativity!
But back to LIGO and the actual detection of gravity wave.
LIGO is essentially two tubes at right angles to each other, each
tube somewhat over a yard in diameter and 4 kilometers (over
two miles) long. These tubes are under vacuum and contain sets
of mirrors at strategic locations. Laser light is used to measure
the distances between the mirrors and the light bounces back and
forth amongst the mirrors making the path length longer than the
actual lengths of the two "arms". By adjusting the distances the
light beams can be make to either "interfere" with or reinforce
each other. This is like the interference you see in an oil film on
a puddle of water, the pretty colors being interference colors.
What does this have to do with gravity waves? If a gravity wave
should come along, it would be expected to change the space
between the mirrors ever so slightly, enough to shift the
interference conditions of the light beams and result in an effect
similar to the oil film colors.
It all sounds not too complex to understand, at least until you
hear how big the effect may be. The gravity wave from those
colliding black holes billions of light years away might shift the
4 kilometer separation of the mirrors by less than a thousandth of
the diameter of a proton! My feeble calculation indicates that the
change in distance would be out in the 22nd or 23rd decimal
place!! Is this a trend or what? That speed of light had better not
deviate from being constant. I wonder if Mr. Brecher shouldn''t
be brought into the LIGO team. To even dream of
accomplishing such a feat the LIGO guys and gals have to deal
with such obvious things as vibrations, expansion and
contraction due to heating and cooling, winds and even the
"noise" arising from various esoteric quantum mechanical
considerations. In my humble opinion, if they manage to pull off
the detection of a gravity wave it will rank right up there with
putting a man on the moon and the Nobel Prize is a given.
Finally, for those purists out there, I should mention that the
gamma ray bursts discussed here are the "classical" gamma ray
bursts. There are also "soft gamma ray repeaters" which give
rise to gamma ray burst from the same location repeatedly and
are believed to be "magnetars". When Bortrum thinks he has a
clue as to what a magnetar is he''ll probably go out on a limb and
write a column.
Allen F. Bortrum
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