The essay is based on Zwicky's
monstrous idea to do space travel by moving the
entire solar system. In the fictional discovery story, it is reported
how scientists learn in 2048 to control some parameters in the nuclear
fission of the sun by triggering asymmetric burning in the sun.
This allows them to produce a tiny acceleration of the sun.
This is used to change the dynamics of the solar system and prevent
a disastrous collision with an asteroid.
This document was submitted in November 26, 1997
to the essay contest "Physics Tomorrow" which was
hold by the journal 'Physics Today'.
The task of the contest was to write an essay as it
could appear in 50 years in Physics Today. While writing
this essay, I was not aware that two movies on Asteroid
impacts were in the making ("Armagedon" and "Deep impact").
Later in 1998, there was even a false alarm on an asteroid
on collision course.
The footnotes after each paragraph and the real web links
to the previously fictive scientific references to the essay
were added when preparing this document for the web.
(January 2000, the 2
Nasa animations
were added in April 2000). A discovery of an object
(
on Nov 2. 2000, CNN ) or an object, one did not even see before it had
passed
on March 8, 2002). An other close encounter occurred on 14. June 2002 when
an asteroid of the size of a football pitch passed within 75'000 miles. It was
discovered only 3 days later.
In February 2013, after the close flyby of Asteroid 2012 DA14 and an impact of a smaller
one on the same day in Russia, the interest has grown even more.
A view of near
earth asteroids. Many articles in the press like
Slate,
NBCNews,
Space.com,
Guardian.
The Earth orbits the Sun in a sort of cosmic shooting gallery. It is
subject to impacts from comets and asteroids. While the primary source of
these objects is the main asteroid belt, there are minor planets
until wide outside the Kuiper belt, where detection and observation is
difficult. While the knowledge of the inner and outer neighborhood of
the solar system has grown [4] so does our
awareness of danger. Eight years ago, routine computations have shown that one
of the minor planets which shoots through the solar system in an abnormal
eccentric orbit has a chance of hitting the Earth in the year 2098.
Since then, Earth and space based radar and optical
telescopes have determined accurately the location, the speed and the shape
of this asteroid. Simulations on the worldwide network of supercomputers (WWNS)
found a positive Lyapunov exponent for the orbit, a sign for chaos.
The scientists became alarmed, when Monte Carlo simulations predicted a
substantial chance of an impact with Earth on the northern hemisphere. The
reason for the uncertainty is in that the impact angle is in the critical
range, where also reflection is possible.
Footnote: The information in this section was taken from
impact.arc.nasa.gov .
There is some uncertainty about the likelyhood of an impact.
But the danger is there and monitoring is done. The Newtonian n-body
problem allows the possibility of chaotic orbits. Such orbits would
indeed be hard to predict. The Lyapunov exponent of a celestial object
moving in the gravitational field of the planets is small because
of the slow angular motion of the planets.
Obtaining an object with a highly unpredictable orbit is
unlikely but not impossible.
Image source:
impact.arc.nasa.gov.
Crash predictions
Long time predictions of a catastrophic asteroid impact are difficult.
If the object is large enough, the
Earth's climate can be perturbed on a global scale because large
quantities of dust gets injected into the stratosphere.
In case of an impact from a meteor with 20 km diameter
already most of population is expected to perish.
The bad news are that the object targeting Earth has a diameter of
90 kilometers. A full impact would probably mean an immediate
extinction of any life because a temporary atmosphere of rock vapor develops
at temperatures of one thousand degrees Celsius on Earth.
In comparison, the meteor producing the Cretaceous impact 65 Million years
had a 10-20 km diameter. There are geological indications that impacts of
the size of 100km might have occurred in the early history of our planet.
Each could have destroyed previously existing life.
Footnote: This section was compiled from an article on crash
predictions of asteroids and summarizes what is currently
believed to happen. Image source:
impact.arc.nasa.gov
Search for a defense plan
A research program of the world science foundation (WSF) brought together
scientists from different disciplines with the aim to search for a solution.
Preventive measures for large asteroid impacts
were never followed because the risk for
accidents or misuse of such a shield was considered too high in comparison
with the impact probability.
The political situation hardly allows now to revive a nuclear weapon
program since the tragic 2020 missile accident which has led to a subsequent
complete ban of any nuclear weapons. It will therefore be impossible to
send and detonate huge hydrogen bombs near the asteroid and blow it into
pieces.
Footnote: the risk of a nuclear accident by an erroreous launch of a
missel is a fact.
Huge nuclear arsenals still exist. It is also reasonable to expect
that an accident would lead to more awareness and maybe even to a ban
of nuclear weapons.
A world science foundation does unfortunately not yet
exist. Image source:
impact.arc.nasa.gov .
A research conference
The most recent conference on the impact issue was organized this spring
by the former NASA Ames Space Science Division. It was supported by most
main universities and international laboratories. Scientists who are not
directly involved were invited to attend the conference via Internet.
Research scientists were encouraged to send ideas in any of the
involved areas. The proposals are constantly updated and
evaluated. As a result, a large tree of ideas has grown. While all material
is accessible online, the authors of the submissions were
kept anonymous. This allowed unbiased evaluation as in journal
publications, where it now became standard to keep authors of papers
anonymous during the refereeing process.
Footnote: Anonymous submissions of articles to journals would
eliminate biased referee work. The later is sometimes done rather purely,
sometimes by diletantism, more often by lack of time.
On the other hand, all the referee reports and names of the
involved referees (also of eventual earlier rejections) should be
added to the published articles. This would give some credit to this
important part of scientific work. Image source:
NASA .
Space travel
One of the ideas which emerged from that big "think tank" scored badly first
on the evaluation scale. Indeed, the idea looks crazy at a first glance.
It is a suggestion of the astronomer Fritz Zwicky (1898-1974)
in the late sixties of the last century to make space travel by moving the
solar system. Zwicky was an eccentric Caltech astronomy professor who was
proud of having achieved in 1957 the first shot of a pellet of aluminum
into interplanetary space. Zwicky thought
that one could use the whole solar system as a "space ship" in order to
travel to other stars. He speculated that this should be accomplished
by shooting high velocity particles onto the Sun and bring them there to
fusion. He stated in his book [5]
that it should be possible to travel like this to the star system
Alpha-Centauri during a 2500 year trip.
Footnote: A
website on Alpha Centauri .
Zwicky indeed proposed this idea and many more.
The space travel with the solar system as spaceship appears in
Fritz Zwicky: "Entdecken, Erfinden, Forschen im morphologischen
Weltbild", p. 237. Image source:
windows.ivv.nasa.gov/ .
Rockets on the sun
The submitted proposal suggested to modify this idea in a less
ambitious way. Instead of generate the energy ourselves, the idea
is to make use of already existing "rockets on the Sun" which are now nearly
canceling each other and to which we will come back later
on. The still horrendously ambitious aim is to accelerate slightly the Sun
and so of the Earth just enough so that the asteroid will miss. The later
will be less influenced by the displacement because it is farer way from
the Sun.
Fine tuning in the next few hundred years should then assure that
planetary orbits of the solar system become not disturbed too much
by this acceleration.
Footnote: Modifying Zwicky's idea to avoid an asteroid impact
is a bit far fetched indeed. However, there could be other applications.
Image source.
Illustration added 2006 from video by JAXA's Hinode spacecraft.
more info
Missing orders of magnitudes
Human technology does not allow the production of enough energies for
such an idea. Many orders of magnitudes
are missing even with a full control of fusion energy.
To see the difficulty, consider the magnitudes. The Sun weights
2 10 30 kilograms. Even if it would be possible
to redirect the entire solar wind which ejects 1017
kilogram per year into one direction, this would displace the Sun only
1 meter in one year. On the other hand, the radiation energy produced
by the Sun is
4 10 33 erg/sec and could in principle be used
to accelerate the Sun to a velocity of 100 m/sec in one
year, when considering the energy only. By heating and cooling different
parts of the Sun and redirect the radiation asymmetrically, a fraction of this
energy could in principle be available. But even if the entire radiation could
be redirected into one direction, the force would accelerate in one year the
Sun only to a speed of 10 -3 cm/sec. The reason for this low
value is that photons do not carry a lot of momentum. How is it possible to
turn more radiation energy into kinetic energy of massive particles?
Footnote: How many orders of magnitudes are missing is not clear but
the question is worth a serious discussion.
While the numbers in this essay should be correct, the conclusion is
rather optimistic. Some fantastic mechanisms and an incredible
better understanding of solar burning is needed to make a control
of the solar fission a theoretical reality.
Giant solar flares
Giant solar flares were a long standing enigma of astrophysics.
As a matter of fact, these coronal mass ejections are the most
energetic phenomena which occur in our solar system [3],
exceeding over short times the radiation energy of the Sun. Moreover,
their energy is mainly kinetic energy of particles. It has been realized that
giant solar flares can produce 1034 erg's, carried away by electrons
or more massive particles. When such large solar flares were observed in
1991 for the first time, they were named "giant solar flares" since they were
up to 1000 times larger than the ones seen previously.
It was then also surprising to see that several giant flares can occur
in a single active region within a short time.
Still, using natural flares as "rockets" is not sufficient because despite a
gigantic energy release, the mass of the ejected material is small. A single
flare accelerates the Sun only to 10-7 cm/sec. Enhancement by
several orders of magnitudes is achieved by manipulating the nonlinear
processes of the photospheric dynamo and the magnetic dynamics in the
corona. This is realistic because small instabilities can trigger the
energy release during a flare. Tiny small energies can control the
subtle bifurcation mechanisms responsible for the flares.
The point is that those energies are in the realm of human technology.
Footnote: Solar flares act as rockets and
are the most energetic events which happen in our solar system.
Whether solar flares can ever be controled with human technology
is not clear. Image source:
www.pnl.gov .
Asymmetric radiation
As a first step it was proposed to produce a resonance in the nuclear reaction
through stimulation with neutron beams which are shot to specific parts
in the core of the Sun, where the nuclear burning happens. Achieving this
goal would be impossible if not fortunately, the energy production of these
nuclear reactions were extremely sensitive to the temperature [1].
Monitoring and amplifying the naturally occurring temperature instabilities
allows to trigger small temperature changes in the treated region.
This produces an asymmetric thermonuclear burning which implies asymmetric
radiation and more importantly, an asymmetric convection.
Footnote: the idea in physics that resonances allow small energies to
built up large energies is correct. Whether it will ever be possible to
monitor and control nuclear reactions in the sun is not clear.
Image source: NASA .
Triggering more flares
The asymmetry is unstable and could not be kept alive for a long time if
not the Sun's atmosphere above the treated region could be kept to be an
"active region". In order to deal with this, strong lasers pointing
to specific parts of the photosphere stimulate or suppress
super giant flares by influencing the energy convection through the
photosphere which lies below the hot chromosphere of the Sun. The flares
will be produced in high altitudes of the atmosphere so that the
particles, mostly electrons and protons but also heavier ions are shot
away from the Sun. Most of the energy is carried away by kinetic energy.
The momentum change coming from those artificially triggered flares at
specifically controlled active regions together with the enhanced
radiation should propel the Sun, a few meters a year at first and
finally, after years of tuning, to several hundred meters per year.
Footnote: this modification was necessary because the photon pressure
would be far too weak for propelling the sun. That a mechanism
similar to ion rockets could work is more reasonable. It adds
however more difficulties. Image source:
nasa .
Targeting the North Pole
The Sun is not spinning as a rigid body but different
altitudes rotate with different speed. This differential rotation would
make it difficult to achieve an acceleration in the planetary plane.
This is the main reason why it is proposed to accelerate the Sun normal
to the planetary plane. Treating the north part of the Sun near the axes
of rotation has also other advantages. First of all, it enhances already
existing coronal holes, the natural main corridors through which particles
of the solar wind escape from the Sun. Also, the pole region can be
accessed at any time of the Earth year.
Finally, the existing solar wind is already much faster near the polar
regions than at the equatorial latitudes.
An "environmental bonus" is that the tremendously increased solar wind will
not be blown into the direction of the Earth.
Footnote: we have learned that any technology also comes with risks.
Changing the fission in the sun would be no exception. And one would
have to keep this in mind.
[July 12, 2012: Animation of
a Solar X-flare blast heading toward earth from spaceweather.com, hitting the earth
on July 14th.
Diving away
If a control and amplification of the "hybrid photon-particle rocket
on the Sun" really works with the desired intensity, the Earth could
"dive away" from the asteroid because the orbit of the minor planet is
sufficiently sensitive to changes of the positions of the planets.
The minor planet which will pass close to Mars before deflected
towards the earth will become redirected slightly away and get a slight
kick "upwards" to pass above the North Pole of the Earth.
The expectation is that treating the Sun for 30 years from now starting
in 10 years would be enough for a success.
Footnote: it is likely that if one would manage to achieve such a
thing, a simpler solution could be realized. But let's continue anyway.
Implementation steps
Should the proposal get approved, huge engineering efforts will be necessary.
Plans for building powerful particle accelerators and
lasers on Mercury and a network of observation satellites orbiting the Sun are
in discussion. Mercury is suited because it is the planet nearest to the Sun
and because it has enough iron for building the large magnets for the
accelerators. Despite being so close to the sun, it will be crucial to compute
fast from the observations the necessary control steps and
to overcome computationally the minute long telecommunication delay.
Fortunately there has been progress in controlling nonlinear partial
differential equations building on older ideas for ordinary differential
equations [2].
Footnote: working from Mercury sounds reasonable. Looking however at
the current obstacles only to land robots on mars, this part could even
pose a major problem. Image source:
www.solarviews.com .
Summary and Zwicky's dream
In summary, the conference findings are that human knowledge of plasma,
nuclear, particle and solar physics as well as the mathematics of
partial differential equations might allow a minor human control of
the dynamics of the solar system. This technology could
help to keep the Earth free from larger asteroid impacts.
And who knows whether maybe, one day, Zwicky's crazy dream will come
true to make space travel by displacing the whole solar system!
Footnote: It is quite reasonable that Zwicky's crazy dream will
appear less crazy in a few hundred years.
Bibliography
1 Internet online library.
Nuclear reactions in the sun
World science foundation, 2040.
http://www.library.org/astro/sun/nuclear/
2 Internet online library.
Partial differential equations.
World science foundation, 2043
http://www.library.org/math/pde/control/.
3 Internet online library.
Solar flares.
World science foundation, 2045.
http://www.library.org/astro/sun/flares/.
4 Internet online library.
Minor planets.
World science foundation, 2046.
http://www.library.org/astro/celestial/minorplanets/.
5 F. Zwicky.
Discovery, invention, research
through the morphological approach.
Available online in http://www.library.org/astro/people/zwicky/,
1969.
The URLS in the above bibliography are fictuous. It is reasonable to
assume however that in 50 years, much of human knowledge is
freely accessible from every computer.
The book 5) exists and contains the idea of Zwicky. Below are
some effective links (valid January 2000).
The essay is based on Zwicky's
monstrous idea to do space travel by moving the
entire solar system. In the fictional discovery story, it is reported
how scientists learn in 2048 to control some parameters in the nuclear
fission of the sun by triggering asymmetric burning in the sun.
This allows them to produce a tiny acceleration of the sun.
This is used to change the dynamics of the solar system and prevent
a disastrous collision with an asteroid. 
This document was submitted in November 26, 1997
to the essay contest "Physics Tomorrow" which was
hold by the journal 'Physics Today'.
The task of the contest was to write an essay as it
could appear in 50 years in Physics Today. While writing
this essay, I was not aware that two movies on Asteroid
impacts were in the making ("Armagedon" and "Deep impact").
Later in 1998, there was even a false alarm on an asteroid
on collision course. 
The Earth orbits the Sun in a sort of cosmic shooting gallery. It is
subject to impacts from comets and asteroids. While the primary source of
these objects is the main asteroid belt, there are minor planets
until wide outside the Kuiper belt, where detection and observation is
difficult. While the knowledge of the inner and outer neighborhood of
the solar system has grown [
Long time predictions of a catastrophic asteroid impact are difficult.
If the object is large enough, the
Earth's climate can be perturbed on a global scale because large
quantities of dust gets injected into the stratosphere.
In case of an impact from a meteor with 20 km diameter
already most of population is expected to perish.
The bad news are that the object targeting Earth has a diameter of
90 kilometers. A full impact would probably mean an immediate
extinction of any life because a temporary atmosphere of rock vapor develops
at temperatures of one thousand degrees Celsius on Earth.
In comparison, the meteor producing the Cretaceous impact 65 Million years
had a 10-20 km diameter. There are geological indications that impacts of
the size of 100km might have occurred in the early history of our planet.
Each could have destroyed previously existing life.
A research program of the world science foundation (WSF) brought together
scientists from different disciplines with the aim to search for a solution.
Preventive measures for large asteroid impacts
were never followed because the risk for
accidents or misuse of such a shield was considered too high in comparison
with the impact probability.
The political situation hardly allows now to revive a nuclear weapon
program since the tragic 2020 missile accident which has led to a subsequent
complete ban of any nuclear weapons. It will therefore be impossible to
send and detonate huge hydrogen bombs near the asteroid and blow it into
pieces.
The most recent conference on the impact issue was organized this spring
by the former NASA Ames Space Science Division. It was supported by most
main universities and international laboratories. Scientists who are not
directly involved were invited to attend the conference via Internet.
Research scientists were encouraged to send ideas in any of the
involved areas. The proposals are constantly updated and
evaluated. As a result, a large tree of ideas has grown. While all material
is accessible online, the authors of the submissions were
kept anonymous. This allowed unbiased evaluation as in journal
publications, where it now became standard to keep authors of papers
anonymous during the refereeing process.
One of the ideas which emerged from that big "think tank" scored badly first
on the evaluation scale. Indeed, the idea looks crazy at a first glance.
It is a suggestion of the astronomer Fritz Zwicky (1898-1974)
in the late sixties of the last century to make space travel by moving the
solar system. Zwicky was an eccentric Caltech astronomy professor who was
proud of having achieved in 1957 the first shot of a pellet of aluminum
into interplanetary space. Zwicky thought
that one could use the whole solar system as a "space ship" in order to
travel to other stars. He speculated that this should be accomplished
by shooting high velocity particles onto the Sun and bring them there to
fusion. He stated in his book [
The submitted proposal suggested to modify this idea in a less
ambitious way. Instead of generate the energy ourselves, the idea
is to make use of already existing "rockets on the Sun" which are now nearly
canceling each other and to which we will come back later
on. The still horrendously ambitious aim is to accelerate slightly the Sun
and so of the Earth just enough so that the asteroid will miss. The later
will be less influenced by the displacement because it is farer way from
the Sun.
Fine tuning in the next few hundred years should then assure that
planetary orbits of the solar system become not disturbed too much
by this acceleration.
Human technology does not allow the production of enough energies for
such an idea. Many orders of magnitudes
are missing even with a full control of fusion energy.
To see the difficulty, consider the magnitudes. The Sun weights
2 10 30 kilograms. Even if it would be possible
to redirect the entire solar wind which ejects 1017
kilogram per year into one direction, this would displace the Sun only
1 meter in one year. On the other hand, the radiation energy produced
by the Sun is
4 10 33 erg/sec and could in principle be used
to accelerate the Sun to a velocity of 100 m/sec in one
year, when considering the energy only. By heating and cooling different
parts of the Sun and redirect the radiation asymmetrically, a fraction of this
energy could in principle be available. But even if the entire radiation could
be redirected into one direction, the force would accelerate in one year the
Sun only to a speed of 10 -3 cm/sec. The reason for this low
value is that photons do not carry a lot of momentum. How is it possible to
turn more radiation energy into kinetic energy of massive particles?
Giant solar flares were a long standing enigma of astrophysics.
As a matter of fact, these coronal mass ejections are the most
energetic phenomena which occur in our solar system [
As a first step it was proposed to produce a resonance in the nuclear reaction
through stimulation with neutron beams which are shot to specific parts
in the core of the Sun, where the nuclear burning happens. Achieving this
goal would be impossible if not fortunately, the energy production of these
nuclear reactions were extremely sensitive to the temperature [
The asymmetry is unstable and could not be kept alive for a long time if
not the Sun's atmosphere above the treated region could be kept to be an
"active region". In order to deal with this, strong lasers pointing
to specific parts of the photosphere stimulate or suppress
super giant flares by influencing the energy convection through the
photosphere which lies below the hot chromosphere of the Sun. The flares
will be produced in high altitudes of the atmosphere so that the
particles, mostly electrons and protons but also heavier ions are shot
away from the Sun. Most of the energy is carried away by kinetic energy.
The momentum change coming from those artificially triggered flares at
specifically controlled active regions together with the enhanced
radiation should propel the Sun, a few meters a year at first and
finally, after years of tuning, to several hundred meters per year.
The Sun is not spinning as a rigid body but different
altitudes rotate with different speed. This differential rotation would
make it difficult to achieve an acceleration in the planetary plane.
This is the main reason why it is proposed to accelerate the Sun normal
to the planetary plane. Treating the north part of the Sun near the axes
of rotation has also other advantages. First of all, it enhances already
existing coronal holes, the natural main corridors through which particles
of the solar wind escape from the Sun. Also, the pole region can be
accessed at any time of the Earth year.
Finally, the existing solar wind is already much faster near the polar
regions than at the equatorial latitudes.
An "environmental bonus" is that the tremendously increased solar wind will
not be blown into the direction of the Earth.
Should the proposal get approved, huge engineering efforts will be necessary.
Plans for building powerful particle accelerators and
lasers on Mercury and a network of observation satellites orbiting the Sun are
in discussion. Mercury is suited because it is the planet nearest to the Sun
and because it has enough iron for building the large magnets for the
accelerators. Despite being so close to the sun, it will be crucial to compute
fast from the observations the necessary control steps and
to overcome computationally the minute long telecommunication delay.
Fortunately there has been progress in controlling nonlinear partial
differential equations building on older ideas for ordinary differential
equations [
In summary, the conference findings are that human knowledge of plasma,
nuclear, particle and solar physics as well as the mathematics of
partial differential equations might allow a minor human control of
the dynamics of the solar system. This technology could
help to keep the Earth free from larger asteroid impacts.
And who knows whether maybe, one day, Zwicky's crazy dream will come
true to make space travel by displacing the whole solar system!
