More than a few Hollywood adventures have featured asteroids smashing
into the earth and wiping out cities or generating monstrous tsunamis.
The notion of taking defensive action against an earth-bound asteroid
is starting to gain traction in the real world.
Two NASA astronauts have proposed
a gravitational tractor spacecraft that could tow an asteroid to a safe
trajectory. Existing asteroid rescue plans call for spacecraft to nudge
asteroids aside, but have practical challenges: it would be difficult
for a spacecraft to maintain both position and contact with an asteroid
because most asteroids rotate and have unstable surfaces.
The NASA plan sidesteps contact by using gravity as an invisible
tow line. This requires positioning a spacecraft of sufficient mass close
to the asteroid's surface and angling its thrusters to just miss the asteroid.
The plan also calls for patience and foresight. Given a lead time of 20
years, a 20-ton spacecraft would require a year to tow a a 200 meter asteroid
to a safe trajectory.
The European Space Agency (ESA) is preparing to test another alternative
asteroid deflection plan. The plan, dubbed the Don
Quijote project, involves smashing a spacecraft into an asteroid in
order to deflect it. The plan calls for two spacecraft -- one to smash
into the asteroid and the other to record what happens. The agency recently
narrowed the choice of asteroids for the initial test to two.
NASA tracks near earth
objects and assesses the risks they pose. The site uses the Torino
scale to indicate the chance of impact and the degree of damage.
(Gravitational Tractor for Towing Asteroids, Nature, November
In recent years researchers have been teasing out the properties
of all manner of networks as wide-ranging as the Web, social connections
among people, and relationships among chemicals in the biochemical processes
that support life.
Scientists from Northwestern University using this network analysis
technique to probe relationships among organic chemicals showed
that the collective endeavor of creating new molecules over the last century
and a half can be modeled as a network with a scale-free structure similar
to the Web.
Rather than being a random process of discovery and creation,
chemistry turns out to have a structure that makes it possible to make
predictions about it.
On the Web, nodes are Web pages and the links between them are
hyperlinks. In an organic chemicals network, nodes are molecules and the
links between them are chemical reactions. A link to a molecule at the
start of a reaction is an outbound link, and a link to a molecule that
results from a reaction is an inbound link.
Scale-free networks have a few heavily-linked nodes and many nodes
with few links. Using a database of nearly 6 million molecules, the researchers
found two types of hub molecules: commonly used ingredients, which have
many outbound links, and highly desirable substances, which have many
The information could be used to predict the ease of synthesizing
a given molecule, the types of molecules that are likely to be created
and the economic value of a molecule.
(Architecture and Evolution of Organic Chemistry, Angewandte
Chemie International Edition, November 11, 2005)
Time simplifies quantum crypto
The field of quantum cryptography, which promises potentially
perfectly secure communications, has matured rapidly. Current research
is aimed at increasing data rates and improving reliability.
Researchers from the University of Geneva in Switzerland have
developed a quantum
cryptography scheme that encodes data in the time of arrival of laser
pulses rather than the polarization or phase of photons. This promises
to simplify and improve the reliability of quantum cryptography equipment.
The recipient occasionally tests the phase of some of the pulses
using traditional quantum cryptography protocols to determine wether an
eavesdropper has observed any of the transmission. Using time of arrival
for data transmission makes for a faster and more reliable quantum cryptography
system, according to the researchers.
The work shows that the bottleneck for quantum cryptography is
the performance of photons detectors. Once those are improved, quantum
cryptography could be used at the full data rates of today's communications
(Fast and Simple One-way Quantum Key Distribution, Applied
Physics Letters, November 7, 2005)
Spreadsheet drives sensor net
Networks of tiny, inexpensive sensors scattered throughout an
environment could make it easier to monitor environmental conditions,
collect scientific data and track people and vehicles for military and
law enforcement purposes. Managing these sensor networks and analyzing
the data they collect, however, promises to be challenging.
Researchers at Microsoft Research are using
spreadsheets to organize and manage data collected by sensor networks.
The researchers' system is a modified version of the company's Excel spreadsheet
that allows users to analyze data from a network of sensors and program
the sensors without special software.
The system allows individual sensors to be mapped to cells within
the spreadsheet. Cell values are data from the sensors or variables that
can be changed to reprogram the sensors.
The researchers set up prototype sensor networks to monitor vehicles
in a parking lot and to monitor environmental conditions within a building.
The software should make it easier for scientists and others to
deploy sensor networks for practical applications.
(A Spreadsheet Approach to Programming and Managing Sensor Networks,
Microsoft Research Technical Reports, October 2005)
Bits and pieces
A solid acid made from sugars or starches is an efficient,
recyclable catalyst for turning vegetable oil into biodiesel fuel;
a carbon nanotube-polystyrene foam makes effective, lightweight
electromagnetic radiation shielding; carbon nanostructures with wheels
roll across surfaces, making steerable