Saturday, February 19, 2000
2/19/00 1:47:59 PM
WIMP in a teacup.
WIMPs are hypothetical weakly interacting massive particles,
thought to exist in flattened spherical haloes surrounding every galaxy. An Italian
to have bolstered earlier evidence for the detection of one such
candidate particle, called a
of the preprint put out by the Laboratori Nazionali del Gran
Sasso, and here is the full
in PDF form.
The particle reported by the Italian team has a mass about that of a
nickel atom, though it could be two or three heavier depending on
the actual value of earth's velocity with respect to the presumed
stationary (but possibly slowly rotating) cloud of WIMPs in which
the Milky Way spins. WIMPs were detected by clocking seasonal
variations in neutralino flux as earth's orbital motion first
bolsters, then detracts from, our velocity due to the galaxy's
rotation plus proper solar motion. The researchers base their claim
on a close match in 4 years' data between predicted and observed
variation, an effect on the order of 5 percent. This finding has not
yet been verified by other researchers. But a number of WIMP
experiments around the world are nearly ready to announce results,
so confirmation or repudiation could come soon.
The NY Times
referenced above notes that, at the presumed mass of the presumed
neutralino, the galaxy would be imbedded in a cloud with a density
of around one WIMP per teacup of space. Multiply the cross-section
of a human body by 140 miles -- the distance you travel through the
WIMP cloud in a second -- and divide by the volume of a teacup to
conclude that about a billion of these puppies are streaming through
you every second. Good thing they interact only weakly.
[Note added 2000-02-20, 12:56 pm:]
Not all of the matter in the universe is luminous. Dark matter
is anything that doesn't shine brightly enough for us to detect
it across whatever gap separates us. The matter we can see
represents only about 30% of the amount needed to assure a
"flat" universe, one which has exactly enough matter to keep it
expanding forever. (The currently favored interpretation of the
Big Bang and its aftermath leads theorists to prefer a flat
Luminous matter is also insufficient to explain the rotation of
galaxies. Unlike the solar system, in which the outer planets
rotate more slowly than the inner, galaxies (including our own)
act more like rigid disks. One explanation for this is that the
galaxies are embedded in haloes of invisible matter far larger
and more massive than the luminous parts we can see.
The missing mass in the universe has always been assumed, I've
assumed, to exist in the form of either WIMPs or MACHOs (massive
compact halo objects) or, more recently, the
This latter is a hypothetical
repulsive force that Einstein invented and later called "the worst mistake of
my career." The CC would cause the expansion of the universe to
accelerate over time. Weirdly enough, this is exactly what researchers
inferred from data on distant supernovas beginning about 2 years ago.
Interesting times when evidence for all three explanations for the
"missing mass" is strengthening at once.
- MACHOs: The recent Atlanta meeting of the AAS featured a number of papers
on "microlensing" -- watching for gravitational distortions in the
light from, say, the Lesser Magellanic Cloud as massive but
nonluminous objects pass between it and us. Such objects might be
MACHOs in the halo of either our own galaxy or of the LMC. An effort
called the MACHO Project
on 5.7 years' worth of data that includes 17 microlensing events
against the LMC. Another Atlanta
a number of microlensing studies as concluding that MACHOs don't
comprise the bulk of our galaxy's halo:
Over 350 microlensing events have been reported (most by the
MACHO Project) of which about 30 are towards the Magellanic
Clouds. The most straightforward interpretation of these events
is that they represent a significant component of the dark halo
of the Milky Way. Alternative explanations have been advanced,
and it has proved difficult to distinguish between the various
suggestions. A robust conclusion, however, is that objects of
substellar mass do not comprise much of the dark matter in the
halo of the Milky Way.
- Cosmological Constant:
A recent issue of Science News features a
of the unanimity the remarkable idea of an accelerating
universal expansion has garnered in just two years -- so much so
that the current best-guess value for the Cosmological Constant,
the push factor, is engraved on a plaque at the top of the
spiral "walk through time" in the new Rose Center (formerly the
Hayden Planetarium) in NYC.
Friday, February 18, 2000
2/18/00 11:50:49 AM
I'm taking the unusual step of reviving a week-old TBTF Log item because
a better explanation has come in. Here's what I wrote last Friday:
This photo won first place in the World Press Photo 2000 contest's
Science and Technology Singles category. The image was captured last
summer by US Navy Ensign John Gay. It shows an F/A-18C Hornet
breaking the sound barrier. More details at this
Alert reader Robert Hettinga alerted a numerical physicist of his acquaintence,
Michael Frese, who laid down the law. His explanation is posted here by permission.
This photograph shows the condensation of a probably
supersaturated mixture of water vapor in air often caused by
changes in pressure.
The particular change in pressure seen here is probably caused
by the shock which develops in the flow of air over a blunt body
at subsonic but near supersonic flow condition. The fact that
the shock does not trail from the front of the plane proves that
the plane's velocity is subsonic.
However, shocks only develop in supersonic flows. This flow has
supersonic regions in it because the passage of the front of the
plane causes the pressure to drop above it, smoothly and
gradually on the time scale of the plane's passage. This
pressure drop causes a decrease in the sound speed in the air,
because cooler air has a lower sound speed.
When the aft parts of the plane arrive, they are then moving
faster than the local sound speed, and cause sharp changes in
pressure, known as shock waves.
This flow condition is known as trans-sonic flight, because some
of the flow is subsonic and some is supersonic. Trans-sonic flow
is a steady-state flow, not a transient one, and is not
dependent for its existence on the acceleration of the plane.
This picture is thus unusual mostly because of the atmospheric
conditions required rather than the exact speed of the plane.
In other words, the guy who took the picture probably had a long
time to get his camera up, on, pointed, and adjusted.
Wednesday, February 16, 2000
2/16/00 1:09:54 PM
Telemarketing to domain-name holders.
A while back
Network Solutions stirred up a hornet's nest when it began spamming
domain-name holders by email looking to drum up new business. Those
wild 'n' crazy guys have now taken to annoying their customers by
telephone. Some of said customers are not best pleased.
This rant was posted by Alan Wexelblat on a private list. I think it
nicely exemplifies the outrage NSI is going to engender by this
latest step over the line.
I just got a phone spam from Network Solutions.
Those <>'s used their own database of contact phone numbers to spam
for more domain registrations.
This really pisses me off. I use a real phone number there in case
there's a real problem and someone actually needs to get ahold of me,
not so these bubble-headed excuses for over-evolved nematodes can
fill up my voicemail with their crapola.
Anyone know who I should complain to? Preferably a phone number. I
wanna call this dickless, brainless, spineless, useless waste of
NSI apparently has company in the shady business of telemarketing to
domain-name holders' phone numbers of record. This
piece recounts an Oklahoma man's 39 successful lawsuits against
unsolicited phone telemarketers. Robert Braver's latest suit names
bulkregister.com, which Braver says had robots call his home
and office phones and his wife's cell phone. This practice is illegal
under both federal and Oklahoma law.
[Note added 2000-02-18, 1:16 pm:]
Brian McWilliams wrote to note that he had written a
for InternetNews earlier this week on the bulkregister.com phone spam.
Tuesday, February 15, 2000
2/15/00 12:59:37 PM
TBTF named to Forbes Magazine's Best of the Web.
The review is
on the Web and on a newsstand near you. Quoth:
Created by consultant Keith Dawson in 1994, this site culls ten
weekly stories from reader e-mails, Internet news and a stable of
contributors. Coverage spans topics from quantum computing to
Microsoft's lesser-known court cases. The Web links are purposeful
and there are no ads to distract. This site will make you sound smart
to your boss.
In the obligatory "best and worst" section Forbes notes that the site's
worst feature is its design. "It has none," they say. (Go on, tell me what
you really think.)
Forbes has set up a reader reviews section at deja.com
[Note added 2000-02-18, 11:25 pm:]
You folks are awesome. Thirty-six of you have ranked and commented on TBTF,
and the repudiation of the "no design" comment is strong -- an overall reader
rating of 4.2 out of 5 on that criterion, and 4.1 overall. Of the 20 other listed
sites in the Technology News category, only four have garnered one or two reader
rankings; the rest have none.
Sunday, February 13, 2000
2/13/00 10:43:47 AM
NASA gets a Valentine from Mars, another from Eros 433.
As if saying Happy St. Valentine's Day from the Red Planet, the Mars
Global Surveyor's Mars Orbiter Camera captured this unique view of a
mesa in the south polar region. Here's the
story, which neglects to mention that the image was actually
captured on November 16, 1999. The heart is about 279 yards across.
Earlier in 1999 the Mars Global Surveyor captured an
more perfect valentine heart, this one expressed as a pit
instead of as a mesa.
Thanks to studly TBTF Irregular Eric Scheid, who did all the research
on this one.
[Note added 2000-02-15, 1:15 pm:
NASA must have hearts on its mind here lately. This
describes yet another heart-shaped crater that the NEAR spacecraft captured
Friday, at a distance of 1609 miles from the surface of Eros 433. Here's
on its own. NEAR entered orbit around the space rock yesterday. Here's
light image from a distance of 210 miles.