The Alan Sondheim Mail Archive

June 19, 2006

When was I born?
When did I die?
When did I write these words?
I wrote them after I was born and before I died.
I wrote them before I was born and before I died.
I wrote them after I was born and after I died.
I wrote them before I was born and after I died.
Where was I born?
Where did I die?

---------- Forwarded message ----------
Date: Mon, 19 Jun 2006 14:30:36 -0700
From: NASA Jet Propulsion Laboratory <>
To: "" <>
Subject: NASA JPL news

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

Erica Hupp 202-358-1237
NASA Headquarters, Washington, D.C.

News Release: 2006-085                                                                  June 19, 2006

Pace Quickens for NASA Spacecraft Orbiting Mars

NASA's newest spacecraft at Mars has already cut the size and duration of each orbit by more than half, just 11 weeks into a 23-week process of shrinking its orbit. By other indicators, the lion's share of the job lies ahead.

"The orbits are getting shorter and shorter. We've finished about 80 of them so far, but we have about 400 more to go, and the pace really quickens toward the end," said Dan Johnston, Mars Reconnaissance Orbiter deputy mission manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Supplementing the daily attentions of navigators, engineers and scientists, the orbiter has begun using unprecedented onboard smarts to schedule some of its own attitude maneuvers during each orbit.

The current phase of the Mars Reconnaissance Orbiter mission, called "aerobraking," began in late March with the spacecraft in a pattern of very elongated, 35-hour orbits.  It will end in early September, according to current plans, once hundreds of careful dips into Mars' atmosphere have adjusted the orbit to nearly circular, two-hour loops. Then, after some touch-up engine burns, deployment of a radar antenna and other transitional tasks, the spacecraft will be in the right orbit and configuration to start its main science phase in November.

During the two-year science phase, Mars Reconnaissance Orbiter will examine Mars from subsurface layers to the top of the atmosphere. It will use its 3-meter (10-foot) diameter dish antenna to pump data Earthward at up to 10 times the pace of any previous Mars mission. Besides providing information about the history and extent of Mars' water, the orbiter will assess prospective landing sites for NASA robots launching in 2007 and 2009.

When the spacecraft first entered orbit around Mars, its farthest point from the planet was about 45,000 kilometers (28,000 miles). After 11 weeks of aerobraking operations, this distance has been reduced to about 20,000 kilometers (12,000 miles). On each orbit since early April, the nearest-to-Mars portion of the orbit has passed through the upper atmosphere, usually at about 105 kilometers (65 miles) above the surface of the planet. The drag created by interaction of the atmosphere with spacecraft surfaces slows the craft.

"Our biggest challenge is the variability of the atmosphere," Johnston said. "It's not uncommon to get a 35 percent change in how much drag the spacecraft experiences from one pass to the next. We need to monitor each pass carefully and be prepared to change the altitude to a safe one for the next pass, if necessary."

While the orbiter is above the atmosphere, it can orient its antenna toward Earth and its solar panels toward the sun.  Before it enters the atmosphere for each pass, it pivots so that the back surfaces of the solar panels and antenna face the direction of travel.  An innovative capability of Mars Reconnaissance Orbiter's onboard software enables it to calculate the time when it needs to reorient itself for the next pass. This feature, called "periapsis timing estimator," was activated in May.

JPL's Jim Graf, project manager for Mars Reconnaissance Orbiter, said, "In the past, the times for turning to aerobraking attitude had to be calculated on the ground and sent to the spacecraft for each pass.  Now, the spacecraft can do that itself. This will be especially helpful when the spacecraft gets to the point when it is doing several drag passes per day."

Mars Reconnaissance Orbiter is the third NASA Mars mission -- after Mars Global Surveyor in 1997 and Mars Odyssey in 2001 -- to use aerobraking to get into a desired, near-circular orbit.  The strategy allows launching the spacecraft with much less fuel than would be required if using just rocket engines to decelerate into the desired orbit. Each drag pass this month is slowing Mars Reconnaissance Orbiter by an average of about 2 meters per second (4.5 miles per hour), which would otherwise require consuming about a kilogram (2.2 pounds) of fuel.

Transition activities during the two months between the end of aerobraking and the beginning of the main science phase will include unfolding two 5-meter (16-foot) lengths of antenna for a ground-penetrating radar instrument, removing the lens cap from a mineral-identifying spectrometer instrument and characterizing all instruments' performance in different modes of use. From early October to early November, Mars will be nearly behind the sun as viewed from Earth.  Communication with all spacecraft at Mars will be unreliable during portions of that period, so commanding will be minimized.

Additional information about Mars Reconnaissance Orbiter is available online at ( . The mission is managed by JPL, a division of the California Institute of Technology, Pasadena, for the NASA Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft.


To remove yourself from all mailings from NASA Jet Propulsion Labratory, please go to

---------- Forwarded message ----------
Date: Mon, 19 Jun 2006 11:06:21 -0400
To: sondheim@PANIX.COM
Subject: Physics News Update 781

The American Institute of Physics Bulletin of Physics News
Number 781  June 19, 2006  by Phillip F. Schewe, Ben Stein,
and Davide Castelvecchi

SYNCHRONIZATION OF EXTINCTION.  A new study of animal populations
shows that even widely separated populations of a single species
will go extinct together if a common external force is applied.
Take the analogy of two grandfather clocks falling into synchrony
through subtle vibrations in the floorboards linking the two
clocks.  In the same way a common stimulant, in the form, say, of
predators or adverse climate conditions, can synchronize the fate of
separate enclaves of an endangered species.  R.E. Amritkar of the
Physical Research Laboratory (Ahmedabad) and Govindan Rangarajan of
the Indian Institute of Science (Bangalore) began with actual field
data that had demonstrated the synchronizing influence of predators
on vole
populations and then applied principles from nonlinear dynamics to
simulate future behavior.  They conclude that provided there is a
common threat, separated communities of the species will synchronize
together before becoming extinct. This is bad news for
conservationists hoping that some decimated species could survive in
isolation.  They show that the net resistance to extinction can be
expressed as a parameter which puts the degree of endangeredness
into numerical form. This theory can help explain why species got
decimated  on a global scale in previous mass extinction events.
(Physical Review Letters, upcoming article;,
91-80-23600373; website at )

physicist Stephen Hawking and Thomas Hertog of CERN
( suggests that it can.  The leading explanation
for the observed acceleration of the expansion of the universe is
that a substance, dark energy, fills the vacuum and produces a
uniform repulsive force between any two points in space---a sort of
anti-gravity. Quantum field theory allows for the existence of such
a universal tendency. Unfortunately, its prediction for the value of
the density of dark energy (a parameter referred to as the
cosmological constant) is some 120 orders of magnitude larger than
the observed value.  In 2003, cosmologist Andrei Linde of Stanford
University and his collaborators showed that string theory allows
for the existence of dark energy, but without specifying the value
of the  cosmological constant.  String theory, they found, produces
a mathematical graph shaped like a mountainous landscape, where
altitude represents the value of the cosmological constant. After
the big bang, the value would settle on a low point somewhere
between the peaks and valleys of the landscape. But there could be
on the order of 10^500 possible low points---with different
corresponding values for the cosmological constant---and no obvious
reason for the universe to pick the one we observe in nature.
Some experts hailed this multiplicity of values as a virtue of the
theory.  For example, Stanford University's Leonard Susskind in his
book  "The Cosmic Landscape: String Theory and the Illusion of
Intelligent Design,"argues that different values of the cosmological
constant would be realized in different parallel worlds---the pocket
universes of Linde's "eternal inflation" theory.  We would just
happen to live in one where the value is very small.  But critics
see the landscape as exemplifying the theory's inability to make
useful predictions.
The Hawking/Hertog paper is meant to address this concern.  It looks
at the universe as a quantum system in the framework of string
theory. Quantum theory calculates the odds a system will evolve a
certain way from given initial conditions, say, photons going
through a double slit and hitting a certain spot on the other side.
You repeat your experiment often enough and then you check that the
odds you predicted were the correct ones.   In Richard Feynman's
formulation of quantum theory, the probability that a photon ends up
at a particular spot is calculated by summing up over all possible
trajectories for the photon. A photon goes through multiple paths at
once and can even interfere with its other personas in the process.
Hawking and Hertog argue that the universe itself must also follow
different trajectories at once, evolving through many simultaneous,
parallel histories, or "branches." (These parallel universes are not
to be confused with those of eternal inflation, where multiple
universes coexist in a classical rather than in a quantum sense.)
What we see in the present would be a particular, more or less
probable, outcome  of the "sum" over these histories. In particular,
the sum should include all possible initial conditions, with all
possible values of the cosmological constant.
But applying quantum theory to  the entire universe---where the
experimenters are part of the experiment---is tricky. Here you have
no control over the initial conditions, nor can your repeat the
experiment again and again for statistical significance.   Instead,
the Hawking-Hertog approach starts with the present and uses what we
know about our branch of the universe to trace its history
backwards. Again, there will be multiple possible branches in our
past, but most can be ignored in the Feynman summation because they
are just too different from the universe we know, so the probability
of going from one to the other is negligible.  For example, Hertog
says, knowledge that our universe is very close to being flat could
allow one to concentrate on a very small portion of the string
theory landscape whose values for the cosmological constant are
compatible with that flatness. That could in turn lead to
predictions that are experimentally testable. For example, one could
calculate whether our universe is likely to produce the microwave
background spectrum we actually observe.  (Physical Review D,
upcoming article; contact Thomas Hertog,

PHYSICS NEWS UPDATE is a digest of physics news items arising
from physics meetings, physics journals, newspapers and
magazines, and other news sources.  It is provided free of charge
as a way of broadly disseminating information about physics and
physicists. For that reason, you are free to post it, if you like,
where others can read it, providing only that you credit AIP.
Physics News Update appears approximately once a week.

AUTO-SUBSCRIPTION OR DELETION: By using the expression
"subscribe physnews" in your e-mail message, you
will have automatically added the address from which your
message was sent to the distribution list for Physics News Update.
If you use the "signoff physnews" expression in your e-mail message,
the address in your message header will be deleted from the
distribution list.  Please send your message to:
(Leave the "Subject:" line blank.)

High-Speed Sutra

I don't know what it means to practice Zen.
I don't know what it means to do anything at all.
Whatever it means, I'm not doing it. I'm definitely not doing it.

I think I might practice something.
I'm already at the edge of the cliff. Something, anything, one for all.
All for one is nothing. I won't practice that.
I won't practice writing either.

The practice of writing is writing.
The practice of Zen is nothing at all. I won't do it.
This isn't writing, this is practice.
I'll write something later on.

I should add I don't know anything about Zen.
I should add I'm writing borrowed-Zen.
I don't know anything about Zen, I'm writing borrowed-Zen.
My Zen is faster than yours.
I should add my Zen is fast.

I won't do it, not even to do it. I won't do Zen.
There are hungry ghosts after me, they know!
Where they are, I'm not. Where I am, they won't go!
My Zen is faster than theirs. My ducks are enlightened Kwak! Kwak!

Not dying is not not wanting to die.
Dying is not wanting to die and not not wanting to die.
After a while negation buzzes. Automata make negation machines.
Negation machines buzz for me. They make things faster.

Just because my Zen is fast doesn't mean it's not Zen.
Just because I feel nothing doesn't mean I'm not enlightened.
My enlightened Zen takes a nanosecond.
Whatever takes anything, I'm not doing it!
I haven't done it either!

This is the High-Speed Sutra.

Generated by Mnemosyne 0.12.