CCNet 56/2002 - 2 May 2002

"This work by Paul Steinhardt and Neil Turok is extraordinarily
exciting and represents the first new big idea in cosmology in over two
decades. They have found a simple explanation for the observed fact the
universe on large scales looks the same to us left and right, up and
down -- a seemingly obvious and natural condition -- that in fact has defied
explanation for decades."
--Jeremiah Ostriker, University of Cambridge



    Andrew Yee <>

    Ron Baalke <>

    I.V. Simonov

    P. Putz

    C. Veillet

    L. Bykova & T. Galushina

    M.D. Norman & D.W. Mittlefehldt

    R.L. Millis et al.

     T. Kenkmann

     Andy Smith <
     Andrew Yee <>


I am pleased to announce that the workshop on HOLOCENE EXTRATERRESTRIAL
AND RECOVERY IN THE HOLOCENE, Brunel University, London) will take place on
Aug. 29, 2002.

Topics covered in this special session will include:

* Environmental effects of small and medium scale hypervelocity impacts
* Sub-critical impacts and Holocene impact carters
* Tsunami sediments and oceanic impacts; detecting oceanic and atmospheric
impacts in the geological record
* Cometary dust loading and abrupt climate change
* Impacts and the abrupt end of ice ages; impacts and societal evolution

Please note that Ted Bryant and Mike Rampino will give plenary keynote
presentations which also focus on the impact issue (past, present and
future). This is the first time that the international Holocene research
community has embraced NEO studies as part of their agenda which I
personally regard as big step in the right direction.

I am confident that our "impact" session will be of high quality and look
forward to welcoming the speakers and other CCNet members in London this
summer. Please do not hesitate to get back in touch with me should you have
any queries. Information about the conference and accomodation can be found
at the conference website at:

Benny Peiser

2002, pm

- Benny Peiser: Sub-Critical Impacts during the Holocene (welcome &
- Mark E. Bailey: Time-Variability of the Interplanetary Complex
- Duncan Steel: The Coherent Catastrophism Hypothesis
- Ted Bryant, Evidence for Cosmogenic Tsunami

Coffee break

- Sharad Master: Umm al Binni lake, a possible Holocene impact
structure in the marshes of southern Iraq: Geological evidence for its
age, and implications for Bronze-age Mesopotamia.
- Siim Veski: Kaali Meteorite impact induced Ecological catastrophe
800-400 BC, as revealed by pollen, XRD, LOI and 14C analyses of peat
containing impact ejecta
- W. Bruce Masse: The human dimensions of cosmic impact: an analysis
of South America's myths of the "Great Fire"
- W.M. Napier: Comet dust as a driver of climate
- Victor Clube: The calendar and the Holocene


>From, 30 April 2002

By Leonard David

The late Charles Conrad, a veteran astronaut who flew Gemini, Skylab, and
Apollo missions, is recognized in a bill before the U.S. Congress that is
tied to spotting celestial bodies that could harm Earth.

Republican Congressman Dana Rohrabacher of California introduced on April 25
the Charles Pete Conrad Astronomy Award Act. The Act calls for the Board of
Regents of the Smithsonian Institution to establish an awards program in
honor of the astronaut.

Conrad was killed on July 8, 1999 in a tragic motorcycle accident in Ojai,
California. He was 69 years of age.

The Act is intended to encourage amateur astronomers to discover new
heavenly bodies and keep an eye on previously identified objects,
particularly those that threaten a close approach to Earth.

"Charles Pete Conrad made history and today in his honor and in his memory,
I am introducing a bill that could help protect the United States of America
and, yes, the entire world," Rohrabacher said in detailing the legislation
before the House of Representatives.

Award categories

The bill, House Resolution 4613 (H.R. 4613), calls for three categories of

The first category is an award for the amateur astronomer who discovers the
largest asteroid crossing in near-Earth orbit;

The second category is an award to an amateur astronomer for discovering
asteroids using information derived from professional sources and locating
newly discovered asteroids; and

The third category is an award for those who provide the greatest service in
updating the Cambridge, Massachusetts-based Minor Planet Center's catalog of
known asteroids.

Rohrabacher noted that the Act underscores the fact that asteroids colliding
with Earth, and the threat they pose, is not science fiction.

"There are numerous examples of asteroids and comets in the last few years
that have come very near to the world and have not been detected until the
last minute or even after they pass by the world. One of them was coming in
from the Sun and was not seen until after it passed the Earth's orbit. If
any of these asteroids or comets would have hit the Earth, it would have
been a catastrophic occasion, perhaps killing hundreds of millions of
people," Rohrabacher said.

Home planet defense

The lawmaker said that by providing awards, amateur astronomers could look
into the sky to help find troublesome objects. "We are mobilizing the people
to help us discover that possible threat," he said.

Rohrabacher said that he once chaired a hearing on the issue, observing that
one witness said not to worry about the problem. That authority testified
that there is about as much chance of a comet hitting the Earth as it is of
going to Las Vegas and getting a royal straight flush, the lawmaker

"And I said, oh, my gosh. I did get a royal straight flush once. I remember
that happening. So this is a real threat, but it is not something we have to
fear. It is something we have to look at and try to find a way to identify
threats. It is called Home Planet Defense. We need to pay some attention to
it; and then if an asteroid does threaten us, we will be able to identify it
far in advance and deter it from its path so it would not hurt the people of
the world," Rohrabacher said.

Looking up and getting involved

A key purpose of the bill is to get young people more interested in space
and science and mathematics.

The awards would be administered by the Smithsonian Institution, with
Rohrabacher asking his U.S. Congress colleagues to join in by co-sponsoring
the Pete Conrad Award bill.

"This bill will do a great deal in bringing to our young people the
realities of science and America's space program. Let us get them off of
these electronic games and get them into the real world and the real world
may well be dealing with threats coming to us from outer space from great
distances away...asteroids and comets that we should know about,"
Rohrabacher said. "I look forward to working with my colleagues and seeing
that we get young Americans looking up just like Pete Conrad...always
looking up and getting involved."

Copyright 2002,


>From Andrew Yee <>

George Diller      
Kennedy Space Center, Fla. April 25, 2002
(321) 867-2468

KSC Release No. 38-02


The NASA Comet Nucleus Tour (CONTOUR) spacecraft arrived at the Kennedy
Space Center April 24 and was transported to the Spacecraft Assembly and
Encapsulation Facility-2 (SAEF-2) in the KSC Industrial Area today to begin
final preparations for launch.

CONTOUR will provide the first detailed look into the heart of a comet --
the nucleus. The spacecraft will fly as close as 60 miles (100 kilometers)
to at least two comets, taking the sharpest pictures yet of the nucleus
while analyzing the gas and dust that surround these rocky,
icy building blocks of the solar system. For the first time, COUTOUR will
help assess the diversity of comets and unravel the mysteries of how they
evolve. The Applied Physics Laboratory of Johns Hopkins University,
Baltimore, Md., built CONTOUR. They will also be in control of the
spacecraft after launch.

Beginning on April 29, the CONTOUR integration and test team will undertake
a system performance test to verify that all spacecraft systems are
functioning to their design capabilities. The week of May 6, using
facilities located at KSC's MILA tracking station, the Deep Space Network
(DSN) compatibility test will be performed to verify CONTOUR's ability to
communicate with the worldwide system of deep space tracking stations
operated by the Jet Propulsion Laboratory.

On May 13, a five-day mission simulation will begin, once again using ground
station facilities at MILA to connect the spacecraft at KSC with the CONTOUR
mission operations control center located at the Applied Physics Laboratory.
The mission operations team will follow a compressed timeline simulating the
flight of CONTOUR, remotely commanding all of the spacecraft's systems and

On May 20, mechanical prelaunch preparations will begin, followed by
installation of the spacecraft's solid rocket motor, attachment of the eight
solar panels, and performance of a solar array lighting test. The spacecraft
will then be placed on a spin-table for spin balance measurements. CONTOUR
can then be loaded with its hydrazine fuel. A weight and center of gravity
determination will be done and a final spin balance test will be performed.

Finally at SAEF-2, the CONTOUR spacecraft will be mated with a solid
propellant upper stage that serves as the third stage of the Delta booster.

The Boeing Delta II launch vehicle is at Cape Canaveral undergoing
pre-erection check out. Buildup of the launch vehicle on Pad A at Space
Launch Complex 17 is scheduled to begin on May 28.

CONTOUR will be transported to the pad and erected atop the Delta II on June
19. After a spacecraft functional test, there will be the integrated
vehicle/spacecraft flight program verification simulated flight. Upon
successful completion, the spacecraft will be closed out for launch and the
vehicle nose fairing installed around the spacecraft.

CONTOUR is scheduled for launch on July 1, 2002 during a 12-second launch
window that extends from 2:56:14 - 2:56:26 a.m. EDT.


>From Ron Baalke <>

                              IMPACT TECTONISM

                     Mora, Sweden, 31 May - 3 June 2002

  With a pre-workshop excursion and two post-workshop excursions to several
             proven and suggested impact structures in Sweden.



This workshop of the ESF IMPACT programme will focus on tectonics of impact
structures and will be located at the town of Mora within the Siljan Impact
Structure, the largest known impact crater in Western Europe. In this
workshop, lectures will be combined with field studies at nearby sites of
the Siljan crater.

The Siljan meeting will cover the following themes:




Simonov IV: The feasibility of using large impact to destroy a dangerous asteroid

Some physical aspects of high velocity (> 30 km/s) collisions involving an
asteroid or comet nucleus are discussed. Impacts by both meteoroids and
massive artificial objects are considered; these may result in effects such
as gas expansion reaction forces, shock wave propagation, and fragmentation.
The approach is based on conservation laws and observed phenomena associated
with high energy impacts, combining data on the attenuation of strong and
weak shock waves in rocks and data on the strength of meteorites as
determined by their observed breakups in the atmosphere. The calculations
accept the prevailing view that asteroids are structurally inhomogeneous and
contain some initial crack distribution, possibly of the type that has been
observed in meteorites. Analytical estimates for the mean fragment size
distribution and the volume of a fragmentation zone are derived from a
step-by-step analysis of the wave evolution. This leads to the surprising
conclusion that a powerful impact can cause the complete disruption into
small pieces of a much larger monolithic asteroid (1-2 km in diameter-by an
impact with a kinetic energy of less than 1 Mt) than previously thought, In
particular, an artificial very massive projectile might be assembled from
low-orbit space debris (dead satellites, abandoned space stations, etc.).
This suggests that kinetic energy impacts are a viable alternative to
nuclear explosions, which other authors have concluded as that required to
protect the Earth from an asteroid on a collision course. Recent
experimental and theoretical results are also used to compare the total
change of asteroid momentum due to a high energy impact to the momentum
produced by gas expansion, and also to that resulting from a nuclear
explosion. (C) 2002 Elsevier Science Ltd. All rights reserved.

Simonov IV, RAS, Inst Problems Mech, Wave Dynam Lab, Moscow 117526, Russia
RAS, Inst Problems Mech, Wave Dynam Lab, Moscow 117526, Russia

Copyright 2002 Institute for Scientific Information


Putz P: Space robotics. REPORTS ON PROGRESS IN PHYSICS 65 (3): 421-463 MAR

This paper reviews the topic of space robotics. As an introduction, some
definitions and the rationale for space robotics are given. The main
differences between space and terrestrial robots are highlighted, and it is
shown that they are driven by the peculiar environmental, system, and
programmatic constraints of space missions. Some common objections against
the use of space robotics are mentioned and rebutted. A major part describes
the typical architecture, sub-systems, and some key technologies of space
robot systems. This distinguishes between 'manipulator arm' and 'rover' type
robots. The interdisciplinary system character of space robotics is
emphasized. The currently perceived application scenarios for space robotics
are introduced next: low-Earth-orbit applications for system servicing and
payload tending, satellite servicing in geostationary Earth orbit, the
assembly of large orbiting structures, and applications in exploration
missions to the Moon, Mars, Mercury, comets, asteroids, and other celestial
bodies. Throughout, the main robotic functions are presented and the most
eminent robotic systems are described which have been operated or are under
development. The practical usage of space robots is illustrated in a final
section. The concept of the robot as a transparent tool for the ground user
is stressed, and a systematic methodology for developing investigations
involving space robots is proposed. The paper closes with some suggestions
for more 'non-conventional' scientific uses of space robots and general
conclusions. High-level literature is indicated to deepen the appreciation
and understanding of the technology and its applications.

Putz P, European Space Agcy, Estec, Res Ctr, ESA Automat & Robot Sect, POB
299, NL-2200 AG Noordwijk, Netherlands
European Space Agcy, Estec, Res Ctr, ESA Automat & Robot Sect, NL-2200 AG
Noordwijk, Netherlands

Copyright 2002 Institute for Scientific Information


Veillet C, Parker JW, Griffin I, Marsden B, Doressoundiram A, Buie M, Tholen
DJ, Connelley M, Holman MJ: The binary Kuiper-belt object 1998 WW31
NATURE 416 (6882): 711-713 APR 18 2002

The recent discovery(1,2) of a binary asteroid during a spacecraft fly-by
generated keen interest, because the orbital parameters of binaries can
provide measures of the masses, and mutual eclipses could allow us to
determine individual sizes and bulk densities. Several binary
near-Earth(3-5), main-belt(6-10) and Trojan(11) asteroids have subsequently
been discovered. The Kuiper belt-the region of space extending from Neptune
(at 30 astronomical units) to well over 100 AU and believed to be the source
of new short-period comets(12)-has become a fascinating new window onto the
formation of our Solar System since the first member object, not counting
Pluto, was discovered in 1992 (ref. 13). Here we report that the Kuiper-belt
object 1998 WW31 is binary with a highly eccentric orbit (eccentricity e
approximate to 0.8) and a long period (about 570 days), very different from
the Pluto/Charon system, which was hitherto the only previously known binary
in the Kuiper belt. Assuming a density in the range of 1 to 2 g cm(-3), the
albedo of the binary components is between 0.05 and 0.08, close to the value
of 0.04 generally assumed for Kuiper-belt objects.

Veillet C, Canada France Hawaii Telescope Corp, POB 1597, Kamuela, HI 96743
Canada France Hawaii Telescope Corp, Kamuela, HI 96743 USA
SW Res Inst, Boulder, CO 80302 USA
Space Telescope Sci Inst, Baltimore, MD 21218 USA
Ctr Astrophys, Cambridge, MA 02138 USA
Observ Paris, F-92195 Meudon, France
Lowell Observ, Flagstaff, AZ USA
Inst Astron, Honolulu, HI 96822 USA

Copyright 2002 Institute for Scientific Information


Bykova L, Galushina T: Numerical simulation of the orbital evolution of
near-earth asteroids close to mean motion resonances

The dynamics of near-Earth asteroids near mean motion resonances with the
Earth or other planets is considered. The probability domains of the motion
of some near-Earth asteroids close to low-order resonances are presented.
The investigations have been carried out by means of a numerical integration
of differential equations, taking into account the perturbations from the
major planets and the Moon. For each investigated object an ensemble of 100
test particles with orbital elements nearby those of the nominal orbit has
been constructed and its evolution has been retraced over the time interval
(-3000, +3000 years). The initial set of orbits has been generated on the
basis of probable variations of the initial orbital elements obtained from
the least square analysis of observations.

Bykova L, Tomsk VV Kuibyshev State Univ, Inst Appl Math & Mech, Tomsk
634050, Russia
Tomsk VV Kuibyshev State Univ, Inst Appl Math & Mech, Tomsk 634050, Russia

Copyright 2002 Institute for Scientific Information


Norman MD, Mittlefehldt DW: Impact processing of chondritic planetesimals:
Siderophile and volatile element fractionation in the Chico L chondrite

A large impact event 500 Ma ago shocked and melted portions of the
L-chondrite parent body. Chico is an impact melt breccia produced by this
event. Sawn surfaces of this 105 kg meteorite reveal a dike of fine-grained,
clast-poor impact melt cutting shocked host chondrite. Coarse (1-2 cm
diameter) globules of FeNi metal + sulfide are concentrated along the axis
of the dike from metal-poor regions toward the margins. Refractory
lithophile element abundance patterns in the melt rock are parallel to
average L chondrites, demonstrating near-total fusion of the L-chondrite
target by the impact and negligible crystal-liquid fractionation during
emplacement and cooling of the dike. Significant geochemical effects of the
impact melting event include fractionation of siderophile and chalcophile
elements with increasing metal-silicate heterogeneity, and mobilization of
moderately to highly volatile elements. Siderophile and chalcophile elements
ratios such as Ni/Co, Cu/Ga, and Ir/Au vary systematically with decreasing
metal content of the melt. Surprisingly small (similar to10(2)) effective
metal/silicate-melt distribution coefficients for highly sideropbile
elements probably reflect inefficient segregation of metal despite the large
degrees of melting. Moderately volatile lithophile elements such K and Rb
were mobilized and heterogeneously distributed in the L-chondrite impact
breccias whereas highly volatile elements such as Cs and Pb were profoundly
depleted in the region of the parent body sampled by Chico. Volatile element
variations in Chico and other L chondrites are more consistent with a
mechanism related to impact heating rather than condensation from a solar
nebula. Impact processing can significantly alter the primary distributions
of siderophile and volatile elements in chondritic planetesimals.

Norman MD, Lunar & Planetary Inst, 3600 Bay Area Blvd, Houston, TX 77058 USA
Lunar & Planetary Inst, Houston, TX 77058 USA
NASA, Johnson Space Ctr, Houston, TX 77058 USA
Australian Natl Univ, Res Sch Earth Sci, Canberra, ACT 0200, Australia

Copyright 2002 Institute for Scientific Information


Millis RL, Buie MW, Wasserman LH, Elliot JL, Kern SD, Wagner RM: The Deep
Ecliptic Survey: A search for Kuiper belt objects and Centaurs. I.
Description of methods and initial results
ASTRONOMICAL JOURNAL  123 (4): 2083-2109 APR 2002

We report here initial results of the Deep Ecliptic Survey, an ongoing new
search for Kuiper belt objects (KBOs) and Centaurs using the 8K x 8K Mosaic
CCD array on the 4 m Mayall Telescope at Kitt Peak National Observatory.
Within the interval covered in this paper, useful observations were obtained
during seven nights in 1998 October and November, 1999 April, and 2000
February. We used a novel technique to efficiently find and determine
positions of moving objects. Sixty-nine KBOs and Centaurs with apparent
magnitudes between 20.6 and approximately the 24th magnitude were
discovered. Nine or 10 of the newly discovered KBOs appear to be in the 3 :
2 mean motion resonance with Neptune, and four appear to be scattered-disk
objects. Three objects were found that may be in the 4 : 3 resonance.
Sixty-two of the objects reported here have been observed on at least one
additional night and have received designations. Our own follow-up
astrometry was done primarily with the WIYN 3.5 m telescope in
queue-scheduled mode and with the Steward Observatory 90 inch (2.3 m)
telescope. Others, using a variety of telescopes, recovered a significant
number of our objects. Although not a primary objective of the survey,
positions of all main-belt asteroids, Trojan asteroids, and nearby
fast-moving asteroids seen in our data also have been determined, and most
have been reported to the Minor Planet Center. Through simulations and
analysis of the existing KBO database, we have investigated the uncertainty
to be expected in various KBO orbital parameters as a function of the extent
of the astrometric coverage. The results indicate that the heliocentric
distance of an object and the inclination of its orbit can be narrowly
constrained with observations from a single apparition. Accurate
determination of semimajor axis and eccentricity, on the other hand,
requires astrometric data extending over additional apparitions. Based on
the observed distribution of orbital inclinations in our sample, we have
estimated the true distribution of orbital inclinations in the Kuiper belt
and find it to be similar to that of the short-period comets. This result is
consistent with the commonly held belief that the Kuiper belt is the source
region of the short-period comets.

Millis RL, Lowell Observ, 1400 W Mars Hill Rd, Flagstaff, AZ 86001 USA
Lowell Observ, Flagstaff, AZ 86001 USA
MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA
Univ Arizona, Large Binocular Telescope Observ, Tucson, AZ 85721 USA
MIT, Dept Phys, Cambridge, MA 02139 USA

Copyright 2002 Institute for Scientific Information


Kenkmann T: Folding within seconds. GEOLOGY 30 (3): 231-234 MAR 2002

Hypervelocity impacts of cosmic projectiles larger than similar to 200 m
diameter are capable of forming complex craters on Earth. At these craters,
shock loading, shock damage, and excavation flow are followed by a
gravity-driven collapse of the deep transient cavity. Such impact structures
are characterized by a central uplift, a flat crater floor, and a terraced
crater rim. Collapse-induced deformation features, like folds and brittle
fault zones, have many similarities to tectonic structures. Typical
deformation patterns of complex terrestrial impact craters of 5-15 km
diameter are compiled and analyzed with respect to their kinematic
development. Unlike their tectonic counterparts, deformation structures are
always the result of non-plane-strain deformation and are formed in a single
event that takes place in seconds to minutes. To understand the
high-strain-rate processes, the microstructure of an impact-induced fold of
the Crooked Creek impact crater (similar to7 km diameter), Missouri, United
States, is investigated in detail. A period of 20-30 s at the most is
determined for the collapse phase of this crater. The gross plastic
deformation behavior of the fold is achieved by localized brittle
deformation along millimeter- to centimeter-spaced fault zones, forming a
network of veins. Shock damage has fractured similar to40% of grain
boundaries. The onset of collapse and associated deformation started in
rocks with a reduced cohesion and is friction controlled.

Kenkmann T, Humboldt Univ, Museum Naturkunde, Inst Mineral, D-10115 Berlin,
Humboldt Univ, Museum Naturkunde, Inst Mineral, D-10115 Berlin, Germany

Copyright 2002 Institute for Scientific Information



>From Andy Smith <
Hello Benny and CCNet,

We have all been concerned about the funding problems in the NASA Orbital
Debris Program because much of our help in the NEO hunt is coming from
equipment that was developed by the AIr Force and NASA, as part of programs
like this. In particular, we have been following the development and use of
liquid mirror technology (LMT) as a way to get large and inexpensive mirrors
into the hunt, quickly. Some work has been done using the 3 meter LMT, here
in New Mexico and we were hoping to have that work continue. It was directly
affected by the NASA program cuts. There aare also larger LMT being
developed and we are very interested in seeing them act as spotters for the
smaller objects (abs.mag. 21 and smaller). One of the big advantages of the
LMT is that it is always looking at the zenith and there is not competition,
among the users, for control.

We ask all who can help, to try to preserve the NASA Orbital Debris
Observatory programs. We expecially welcome the folks in the U.S. Congress
for proposing the Conrad award. Pete Conrad was well known to us and did a
lot to advance many important programs. Also, the Space Sub-Committee of the
Science Committee of the U.S.House of Representatives has been the NEO
champion for more than a decade and we thank them and ask that they help us
to get the Natural Hazards Caucus of the U.S.Senate to recognize the NEO
danger. We especially appeal to the Caucus Co-Chairs, Sens. Stevens and

Progress In The Hunt

We are approaching the 200 point, after 4 months of searching, by the global
team, and this clearly looks like it will be another record year (nearly 600
NEO). Linear is in the lead, followed by NEAT. We are still hoping that our
other great programs will be able to make larger contributions. We are
especially concerned about CATALINA and SPACEGUARD-JAPAN, because they seem
to be having difficulties. We are also hoping to see the UK telescopes
adding to the NEO list (Newton, etc.).

Planetary Defense Day

Each year, since the SL-9 impact of Jupiter, we have observed the 16th of
July as a special day and we have celebrated our progress, as a global team,
toward asteroid/comet emergency  (ACE)awareness, prevention and
preparedness. We play Beethovens Symphony #1 (as they did on the night of
the SL-9 Discovery), remember all who have helped and are helping in this
vital cause and rededicate ourselves to the mission. We cordially invite all
Net members to join with us, this year, in this observation.

ACE Magnitude Scale Addition

There are only a few explosive dangers that compare to asteroid/comet impact
and we find that volcanics fit so well that we are adding them to our
simple, exponential ACE Scale and we are now comparing our scale with the
Richter. The Tambora event was in the tens of thousands of megatons range
and it equaled about a 400 meter impact (ACE #4). As you will recall, our
scale starts with a Tunguska class event (50 meter range) and the NEO
diameter double with each step. ACE#10 is about the size of Hale-Bopp.

Andy Smith


>From Andrew Yee <>

Office of Communications
Stanhope Hall
Princeton, New Jersey 08544-5264
Telephone 609-258-3601; Fax 609-258-1301

April 25, 2002

New Theory Provides Alternative to Big Bang

A new theory of the universe suggests that space and time may not have begun
in a big bang, but may have always existed in an endless cycle of expansion
and rebirth.

Princeton physicist Paul Steinhardt and Neil Turok of Cambridge University
described their proposed theory in an article published April 25 in an
online edition of Science.

The theory proposes that, in each cycle, the universe refills with hot,
dense matter and radiation, which begins a period of expansion and cooling
like the one of the standard big bang picture. After 14 billion years, the
expansion of the universe accelerates, as astronomers have recently
observed. After trillions of years, the matter and radiation are almost
completely dissipated and the expansion stalls. An energy field that
pervades the universe then creates new matter and radiation, which restarts
the cycle.

The new theory provides possible answers to several longstanding problems
with the big bang model, which has dominated the field of cosmology for
decades. It addresses, for example, the nagging question of what might have
triggered or come "before" the beginning of time.

The idea also reproduces all the successful explanations provided by
standard picture, but there is no direct evidence to say which is correct,
said Steinhardt, a professor of physics. "I do not eliminate either of them
at this stage," he said. "To me, what's interesting is that we now have a
second possibility that is poles apart from the standard picture in many
respects, and we may have the capability to distinguish them experimentally
during the coming years."

The big bang model of the universe, originally suggested over 60 years ago,
has been developed to explain a wide range of observations about the cosmos.
A major element of the current model, added in the 1980s, is the theory of
"inflation," a period of hyperfast expansion that occurred within the first
second after the big bang. This inflationary period is critical for
explaining the tremendous "smoothness" and homogeneity of the universe
observed by astronomers, as well as for explaining tiny ripples in space
that led to the formation galaxies.

Scientists also have been forced to augment the standard theory with a
component called "dark energy" to account for the recent discovery that the
expansion of the universe is accelerating.

The new model replaces inflation and dark energy with a single energy field
that oscillates in such a way as to sometimes cause expansion and sometimes
cause stagnation. At the same time, it
continues to explain all the currently observed phenomena of the cosmos in
the same detail as the big bang theory.

Because the new theory requires fewer components, and builds them in from
the start, it is more "economical," said Steinhardt, who was one of the
leaders in establishing the theory of inflation.

Another advantage of the new theory is that it automatically includes a
prediction of the future course of the universe, because it goes through
definite repeating cycles lasting perhaps trillions of years each. The big
bang/inflation model has no built-in prediction about the long-term future;
in the same way that inflation and dark energy arose unpredictably, another
effect could emerge that would alter the current course of expansion.

The cyclic model entails many new concepts that Turok and Steinhardt
developed over the last few years with Justin Khoury, a graduate student at
Princeton, Burt Ovrut of the University of Pennsylvania and Nathan Seiberg
of the Institute for Advanced Study.

"This work by Paul Steinhardt and Neil Turok is extraordinarily exciting and
represents the first new big idea in cosmology in over two decades," said
Jeremiah Ostriker, professor of astrophysics at Princeton and the Plumian
Professor of Astronomy and Experimental Philosophy at Cambridge.

"They have found a simple explanation for the observed fact the universe on
large scales looks the same to us left and right, up and down -- a seemingly
obvious and natural condition -- that in fact has defied explanation for

Sir Martin Rees, Royal Society Research Fellow at Cambridge, noted that the
physics concerning key properties of the expanding universe remain
"conjectural, and still not rooted in experiment or observation."

"There have been many ideas over the last 20 years," said Rees. "Steinhardt
and Turok have injected an imaginative new speculation. Their work
emphasizes the extent to which we may need to jettison common sense
concepts, and transcend normal ideas of space and time, in order to make
real progress.

"This work adds to the growing body of speculative research which intimates
that physical reality could encompass far more than just the aftermath of
'our' big bang."

The cyclic universe theory represents a combination of standard physical
concepts and ideas from the emerging fields of string theory and M-theory,
which are ambitious efforts to develop a unified theory of all physical
forces and particles. Although these theories are rooted in complex
mathematics, they offer a compelling graphic picture of the cyclic universe

Under these theories, the universe would exist as two infinitely large
parallel sheets, like two sheets of paper separated by a microscopic
distance. This distance is a extra, or fifth dimension, that is not apparent
us. At our current phase in the history of the universe, the sheets are
expanding in all directions, gradually spreading out and dispersing all the
matter and energy they contain. After trillions of years, when they become
essentially empty, they enter a "stagnant" period in which they stop
stretching and, instead, begin to move toward each other as the fifth
dimension undergoes a collapse.

The sheets meet and "bounce" off each other. The impact causes the sheets to
be charged with the extraordinarily hot and dense matter that is commonly
associated with the big bang. After the sheets move apart, they resume their
expansion, spreading out the matter, which cools and coalesces into stars
and galaxies as in our present universe.

The sheets, or branes, as physicists call them, are not parallel universes,
but rather are facets of the same universe, with one containing all the
ordinary matter we know and the other containing "we know not what," said
Steinhardt. It is conceivable, he said, that a material called dark matter,
which is widely believed to make up a significant part of the universe,
resides on this other brane. The two sheets interact only by gravity, with
massive objects in one sheet exerting a tug on matter in the other, which is what dark
matter does to ordinary matter.

The movements and properties of these sheets all arise naturally from the
underlying mathematics of the model, noted Steinhardt. That is in contrast
to the big bang model, in which dark energy has been added simply to explain
current observations.

Steinhardt and Turok continue to refine the theory and are looking for
theoretical or experimental ideas that might favor one idea over the other.

"These paradigms are as far apart as you can imagine in terms of the nature
of time," said Steinhardt. "On the other hand, in terms of what they predict
about the universe, they are as close as you can be up to what you can
measure so far.

"Yet, we also know that, with more precise observations that may be possible
in the next decade or so, you can distinguish them. That is the fascinating
situation we find ourselves in. It's fun to debate which ones you like
better, but I really think nature will be the final arbiter here."

For further information and a graphic animation of the cyclic scenario, see

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