The Physics of Star Trek by Lawrence M. Krauss Page B
Authors: Lawrence M. Krauss
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can develop such a fine
information storage and retrieval device, I believe that there is still a long way we can
go.
THAT QUANTUM STUFF: For some additional cold water of reality, two words: quantum
mechanics. At the microscopic level necessary to scan and re-create matter in the
transporter, the laws of physics are governed by the strange and exotic laws of quantum
mechanics, whereby particles can behave like waves and waves can behave like particles. I
am not going to give a course in quantum mechanics here. However, the bottom line is as
follows: on microscopic scales, that which is being observed and that which is doing the
observation cannot be separated. To make a measurement is to alter a system, usually
forever. This simple law can be parameterized in many different ways, but is probably most
famous in the form of the Heisenberg uncertainty principle. This fundamental lawwhich
appears to do away with the classical notion of determinism in physics, although in fact
at a fundamental level it doesn'tdivides the physical world into two sets of observable
quantities: the yin and the yang, if you like. It tells us that
no matter what technology is invented in the future,
it is impossible to measure certain combinations of observables with arbitrarily high
accuracy. On microscopic scales, one might measure the position of a particle arbitrarily
well. However, Heisenberg tells us that we then cannot know its velocity (and hence
precisely where it will be in the next instant) very well at all. Or, we might ascertain
the energy state of an atom with arbitrary precision. Yet in this case we cannot determine
exactly how long it will remain in this state. The list goes on.
These relations are at the heart of quantum mechanics, and they will never go away. As
long as we work on scales where the laws of quantum mechanics applywhich, as far as all
evidence indicates, is at least larger than the scale at which quantum gravitational
effects become significant, or at about 10
-33
cmwe are stuck with them.
There is a slightly flawed yet very satisfying physical argument that gives some heuristic
understanding of the uncertainty principle. Quantum mechanics endows all particles with a
wavelike behavior, and waves have one striking property: they are disturbed only when they
encounter objects larger than their wavelength (the distance between successive crests).
You have only to observe water waves in the ocean to see this behavior explicitly. A
pebble protruding from the surface of the water will have no effect on the pattern of the
surf pounding the shore. However, a large boulder will leave a region of calm water in its
wake.
So, if we want to “illuminate” an atomthat is, bounce light off it so that we can see
where it iswe have to shine light of a wavelength small enough so that it will be
disturbed by the atom. However, the laws of quantum mechanics tell us that waves of light
come in small packets, or quanta, which we call photons (as in starship “photon
torpedoes,” which in fact are not made of photons). The individual photons of each
wavelength have an energy inversely related to their wavelength. The greater the
resolution we want, the smaller the wavelength of light we must use. But the smaller the
wavelength, the larger the energy of the packets. If we bombard an atom with a high-energy
photon in order to observe it, we may ascertain exactly where the atom was when the photon
hit it, but the observation process itself that is, hitting the atom with the photonwill
clearly transfer significant energy to the atom, thus changing its speed and direction of
motion by some amount.
It is therefore impossible to resolve atoms and their energy configurations with the
accuracy necessary to re- create exactly a human pattern. Residual uncertainty in some of
the observables
information storage and retrieval device, I believe that there is still a long way we can
go.
THAT QUANTUM STUFF: For some additional cold water of reality, two words: quantum
mechanics. At the microscopic level necessary to scan and re-create matter in the
transporter, the laws of physics are governed by the strange and exotic laws of quantum
mechanics, whereby particles can behave like waves and waves can behave like particles. I
am not going to give a course in quantum mechanics here. However, the bottom line is as
follows: on microscopic scales, that which is being observed and that which is doing the
observation cannot be separated. To make a measurement is to alter a system, usually
forever. This simple law can be parameterized in many different ways, but is probably most
famous in the form of the Heisenberg uncertainty principle. This fundamental lawwhich
appears to do away with the classical notion of determinism in physics, although in fact
at a fundamental level it doesn'tdivides the physical world into two sets of observable
quantities: the yin and the yang, if you like. It tells us that
no matter what technology is invented in the future,
it is impossible to measure certain combinations of observables with arbitrarily high
accuracy. On microscopic scales, one might measure the position of a particle arbitrarily
well. However, Heisenberg tells us that we then cannot know its velocity (and hence
precisely where it will be in the next instant) very well at all. Or, we might ascertain
the energy state of an atom with arbitrary precision. Yet in this case we cannot determine
exactly how long it will remain in this state. The list goes on.
These relations are at the heart of quantum mechanics, and they will never go away. As
long as we work on scales where the laws of quantum mechanics applywhich, as far as all
evidence indicates, is at least larger than the scale at which quantum gravitational
effects become significant, or at about 10
-33
cmwe are stuck with them.
There is a slightly flawed yet very satisfying physical argument that gives some heuristic
understanding of the uncertainty principle. Quantum mechanics endows all particles with a
wavelike behavior, and waves have one striking property: they are disturbed only when they
encounter objects larger than their wavelength (the distance between successive crests).
You have only to observe water waves in the ocean to see this behavior explicitly. A
pebble protruding from the surface of the water will have no effect on the pattern of the
surf pounding the shore. However, a large boulder will leave a region of calm water in its
wake.
So, if we want to “illuminate” an atomthat is, bounce light off it so that we can see
where it iswe have to shine light of a wavelength small enough so that it will be
disturbed by the atom. However, the laws of quantum mechanics tell us that waves of light
come in small packets, or quanta, which we call photons (as in starship “photon
torpedoes,” which in fact are not made of photons). The individual photons of each
wavelength have an energy inversely related to their wavelength. The greater the
resolution we want, the smaller the wavelength of light we must use. But the smaller the
wavelength, the larger the energy of the packets. If we bombard an atom with a high-energy
photon in order to observe it, we may ascertain exactly where the atom was when the photon
hit it, but the observation process itself that is, hitting the atom with the photonwill
clearly transfer significant energy to the atom, thus changing its speed and direction of
motion by some amount.
It is therefore impossible to resolve atoms and their energy configurations with the
accuracy necessary to re- create exactly a human pattern. Residual uncertainty in some of
the observables
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