Ask A Scientist Physics Archive

name         John P.
status       educator
age          50s

Question -   How do we know that an event - pair formed quantum effect is 
simultaneously changed over a distance? That can only occur fastest over a 
light signaled sequence and hence by light speed. According to relativity there 
is no simultaneity. So what does happen with quantum effects at a distance? Is there 
a particle which transfers information?
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This effect is not "explained" to the satisfaction of many theoretical physicists. It 
involves a concept called "entanglement" (there is a book by that title the discusses 
the topic). When a pair of particles or photons are created and move away from one 
another, each 'remembers' the quantum mechanical state from which it was formed. Since 
the information is already imbeded in the wave function of the state no "new" 
information that cannot be exchanged at speeds exceeding needs to occur.

I am not qualified to say much more, but I know that this interpretation in not 
"bought" by a lot of people who understand the problem way better than I.

Vince Calder
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John P.,
One difficulty in quantum mechanics is understanding wave-particle duality. When we get 
down to quantum levels, i.e. single particles, the word "particle" starts to mean 
something different.  A particle has wave qualities.  A wave has particle qualities.  
Another difficulty is the effect of time.  In the world as we see it, time passes to 
allow things to happen. What happens now is not affected by the future.  At the quantum 
level, time is very different.  The "wave function" of an object is defined over time as 
well as position.  If you know the wave function of an object now, you know it throughout 
the future.  Unfortunately, wave functions cannot be measured directly.  We can only 
measure mathematical averages that involve wave functions.

When two objects are created together, the properties and parameters of their wave 
functions are linked for all time.  As the wave functions progress through time, they 
change together.  There are no particles sending information back and forth.

Scientists have been able to join quantum physics with relativity is through string 
theory.  Doing so requires a much more complex universe than we can see.  Time and 
motion take on whole new meanings.  I know of no scientist who claims complete 
understanding of string theory.  I do not understand it much at all.

Dr. Ken Mellendorf
Physics Professor
Illinois Central College
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