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Time and Absolute Zero
Name: Stephen H.
Status: educator
Age: 20s
Location: N/A
Country: N/A
Date: 2001-2002
Question:
In theory, would time pass for an object that exists at absolute zero
temperature? If, according to the theory of relativity, time only
exists as it relates to motion, does that mean that if there is no
molecular motion, time essentially would be at a standstill?
Replies:
Stephen,
Even at absolute zero there is motion. It is just that all the matter is
in its lowest vibrational state and therefore cannot lose energy to its
environment. Hence it is as cold as it can get which makes it an excellent
reference point for temperature (and thus energy).
Since motion is not stopped at absolute zero, neither is time.
Greg Bradburn
P.S. What does it mean to say that motion has stopped? Motion of an object
is always measured relative to the position of another object. Thus, while
an object may appear to be motionless to a person in the same frame of
reference in reality it may be speeding along at thousands of miles per
second (when viewed from another frame of reference).
The concept of absolute zero temperature appears to surround itself in a
cloak of mystery. Some deserved others not. Certainly the quantum effects of
Bose-Einstein condensates are strange and only occur at temperatures less
than micro-kelvins. Being able to trap light and make it "stop" certainly is
not standard behavior, but it also is not magic and while extraordinary does
not mean that our view of the molecular world requires major overhaul.
Even at absolute zero, which is not actually attainable even though you can
get very close, not all motion ceases. Quantum mechanics still leaves us
with zero point energy, which is related to the Heisenberg uncertainty
principle.
There is no evidence that time would "stop" and it is not even clear what
that means. The theory of relativity says that space and time are not
separable, but it does not mean that it does not exist in various frames of
reference.
Vince Calder
Stephen,
If the entire universe, everything that in any way could interact with
anything else, never changed in any way, then you would not be able to
detect passage of time. Even a molecule at absolute zero may detect random
photons flying through the air, an occasional stray electron. A neutron at
absolute zero still may be able to undergo beta decay, turning into a
proton, electron, and neutrino. To measure time, something you can detect
must be moving. You need to measure a change, and know at what rate the
change occurs. This will allow you to make a time measurement. You do not
need to move. Your clock needs to have something moving.
Dr. Ken Mellendorf
Physics Instructor
Illinois Central College
Good question! However, I believe that time would continue. It would be
impossible (energy is conserved) to get the entire universe to absolute
zero, so time would go on in some places, at least. Time stopping in only
parts of the universe would be even more discombobulating than time
stopping everywhere.
Also, even at absolute zero, some motion is necessary (zero-point energy)
by Heisenberg's Uncertainty Principle. Since the uncertainty in a
particle's position times the uncertainty in its momentum must be greater
than Planck's constant, if a particle is constrained in its position at
all, it's momentum must have some uncertainty, which means it cannot be
zero. For example, electrons in atoms must still move in their orbits.
Best, Dick J. Plano ...
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