chaired the “Exotic Science” session at the DARPA/NASA sponsored 100 Year
Starship Symposium, held in
First, let us assume, following the lead of Thorne, Morris, and Yurtserver, that we can snatch microscopic wormholes from the quantum foam and stabilize them. If we keep a wormhole mouth microscopic in mass and size, it behaves much like a fundamental particle with a very large mass, perhaps somewhat in excess of the Planck mass of 21.8 micrograms. For the purposes of calculation, let us assume that we can produce a stabilized microscopic wormhole with a mass of 10 Planck masses or 218 micrograms. Could such an object exist? Visser has described wormhole solutions to Einstein's equations of general relativity that are flat-space wormholes stitched together across a cut and co-stabilized by a tiny loop of negative-tension cosmic string. A wormhole like this might occur naturally in the aftermath of the Big Bang and might have the size and mass described above.
we take the two wormhole mouths of this object and thread lines of electrical
force through them, until we have passed about 20 coulombs of charge through the
wormhole. This can be done, for
example, with a 20 microampere electron beam passing through the wormhole for
about 12 days. The result is that
the wormhole mouth will now have the same charge-to-mass ratio as a proton and
will behave like a proton in the electric and magnetic fields of a particle
we transport what we will call the "traveling wormhole mouth" to
proton with a total energy of 7.0 TeV will have a Lorentz gamma factor (g
of 7,455. The accelerated
wormhole mouth will have the same Lorentz factor.
This is the factor by which the total mass-energy E
of the proton moving at this high velocity v exceeds its rest mass M.
It is also the factor by which time dilates, i.e., by which the clock of
a hypothetical observer riding on the proton would slow down.
The wormhole is traveling at a velocity that is only a tiny fraction less
than the speed of light, so it travels a distance of one light-year in one year.
However, to an observer riding on the wormhole mouth, because of
relativistic time dilation the distance of one light year would be covered in
only 1/7,455 of a year or 70.5 minutes.
back on Earth if we peek through the other wormhole mouth that is at rest in our
laboratory, we see the universe from the perspective of an observer riding on
the traveling wormhole mouth. In
other words, in 70.5 minutes after its launch from CERN, through the wormhole we
will be able to view the universe one light year away.
Later, in 11.7 hours we will view the surroundings 10 light-years away.
In 4.9 days, we will view the surroundings 100 light years away.
And so on.
is a remarkable result. How is it
possible that, if the traveling wormhole mouth requires 100 years, as viewed
from Earth, to travel 100 light years, we can view its destination as observers
looking through the wormhole in a bit less than 5 days?
It is because, as Morris, Thorne and Yurtserver pointed out, the special
relativity of time dilation makes a wormhole with one high-velocity mouth into a
time machine. The wormhole mouth,
100 light years away, connects back
in time to its departure point only 5 days after it left.
From our point of view, it has moved 100 light years at a speed of 7,455
could the traveling wormhole mouth be aimed so accurately from its start at CERN
that it might it actually pass through another star system many light years
away, to survey its planets, etc.? And
could it stop when it got there? To
answer these questions, we must understand the idea of "back reaction"
as it applies to wormhole ends. The
way wormholes work, it is not possible to change the amount of conserved
quantities like mass-energy, electric charge, and momentum in the local space
region around the wormhole mouths. If
an electric charge disappears into a wormhole mouth, the entry mouth acquires
the quantity of electric charge that passed through it (think of the lines of
electric flux threading the wormhole). Similarly,
if a mass goes through, the entry mouth becomes more massive.
And if a high momentum particle goes through, the entry mouth is pushed
forward with that momentum. In this
way, the local mass-energy, charge, and momentum in the vicinity of the wormhole
mass do not change. No mass-energy,
charge, or momentum can magically appear or disappear.
if a positive electric charge emerges from the exit wormhole mouth, the mouth
acquires an equal and opposite charge, so that the net charge in the region does
not change. An emerging massive
particle causes the exit mouth to lose mass-energy, and an emerging high
momentum particle gives the exit mouth a recoil momentum in the opposite
direction. This is called back
reaction. (We note that in the
May-1990 column we suggested refueling a starship though a wormhole.
That would not work, because of back-reaction effects.)
effect of back-reaction in changing the mass of a wormhole mouth raises a flag
of caution. Since we have not
specified how the wormhole is stabilized against its intrinsic tendency to
collapse and close off, we do not really understand the rules concerning the
mass of the traveling wormhole. In
particular, we do not understand how massive it can be, and how small the mass
can be allowed to become before stability is lost.
Can the mass go to zero? Can
it go negative? Managing the masses
of the two wormhole mouths during steering and deceleration maneuvers is likely
to be a major problem in implementing the steering scheme described below.
the mass problem can be managed, the momentum back reaction can be used to steer
the traveling wormhole mouth. The
direction of travel, as viewed through the wormhole, can be monitored.
Course corrections can be made by directing a high-intensity light beam
through the laboratory based wormhole mouth at right angles to the direction of
travel. The exit mouth will lose a
bit of mass-energy in this process, but it will also be gaining some mass energy
as interstellar gas passes through it, which may compensate.
We note that, in terms of momentum change vs. mass gain of the wormhole
mouth, the use of light for steering is preferable to high energy particles,
even though the momentum carried by light is only its energy divided by the
speed of light.
that precision steering can be accomplished, stopping is not too difficult.
The exit mouth can be steered to make passes through the upper
atmospheres of planets or to have grazing collisions with atmosphere of the star
itself, until the great initial velocity has been dissipated.
In this process, considerable mass will pass through the traveling mouth,
and it will gain this mass-energy by back reaction.
It can tour the star system, propelled by high momentum particle jets
incident on the stay-at-home mouth in the laboratory.
Such steering will tend to reduce the mass of the wormhole mass,
partially compensating for the mass-gain it received in decelerating, and
perhaps it could be used for sampling planetary atmospheres.
that the wormhole mouth has arrived at the star system of interest, a survey of
the planets can begin. We assume
that we have laboratory control of the diameter of the wormhole mouth, and that
it can be enlarged to a diameter that is convenient for sampling.
If a habitable planet is found, the wormhole mouth can be brought to its
surface, and samples can be extracted through the wormhole and analyzed,
(perhaps sending compensating mass back in the other direction to keep the
wormhole mouth masses in balance).
Ultimately, when the survey is complete, the wormhole can be expanded, permitting robot precursors, explorers, colonists, and freight to move through. Again, the mass of the wormhole mouths would have to be managed, moving equal masses in the two directions during wormhole transits, perhaps by sending compensating masses of water through pipes. This scheme could allow very rapid travel to and colonization of various star systems containing earth-like planets. Thus, if stable wormholes are possible at all, they may represent a path to the stars that would sweep away many of our previous concepts and prejudices about how the stars can and should be reached.
there any problem with causality created by using what is in essence a time
machine to reach the stars? Perhaps.
The issue is whether a timelike loop might be established.
Although the space-time interval from some event at the distant star to
the observation of that event on Earth, as viewed through the wormhole,
represents two-way communication across a spacelike separation, there is no
causality problem because there is no loop.
However, a causality problem could arise if similar but independent wormhole connections were established with accelerated wormhole mouths sent from the distant star system back to Earth, or even to another star system that had been similarly contacted by the Earth. In that case, transit through one wormhole followed by return through the other would constitute a timelike loop. Stephen Hawking has suggested that Nature will prevent the establishment of any time-like loop through an exponential rise in vacuum fluctuations that would destroy some elements of the incipient loop. Thus, an attempt to set up the second link might result in an explosion. The moral is that such wormhole connections must originate from only one central cite. Any attempt at replication from another site might lead to disaster.
brings us to a variation of the famous Fermi Paradox: if interstellar wormhole
transport is possible, shouldn't the technologically advanced civilizations of
our galaxy already be sending tiny accelerated wormhole portals in our
direction? Then, where are they?
they are already here. Cosmic ray physicists have occasionally observed strange
super-energetic cosmic ray detection events, the Centauro events.
These are cosmic ray particles with incredibly high energies that, when
striking Earth's upper atmosphere, produce a large shower of particles that
contains too many gamma rays and too few mu leptons, as compared to more normal
cosmic ray shower events. The Centauro events presently lack an explanation
based on any known physics. However,
an accelerated wormhole mouth with a large electric charge should have a large
gamma-ray to mu lepton production ratio in such collisions, since it would have
large electromagnetic interactions but no strong or weak interactions with the
matter with which it collided.
is interesting to contemplate the possibility that some advanced civilization
may be mapping the galaxy with accelerated wormhole portals, sending little
time-dilated observation points out into the cosmos as peep-holes for viewing
the wonders of the universe. And
perhaps, when a particularly promising or interesting scene comes into view, the
peep hole is halted and expanded into a portal through which a Visitor can pass.
we need to gain much more understanding of wormholes. They could provide our
pathway to the stars.
Michael S. Morris, Kip
S. Thorne, and Ulvi Yurtsever, Physical Review Letters 61, 1446 (1988).
Matt Visser, Phys. Rev. D 39, 3182 (1989).
Aris Angelis, "The mysteries of cosmic rays", The CERN Courier, Jan 29, 1999, http://cerncourier.com/cws/article/cern/27944
SF Novels by John Cramer: my two hard SF novels, Twistor and Einstein's Bridge, are newly released as eBooks and are available at : http://bookviewcafe.com/bookstore/?s=Cramer .
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