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Q: Measurement or Physics ( Answered,   0 Comments )
Subject: Measurement or Physics
Category: Miscellaneous
Asked by: alan123-ga
List Price: $10.00
Posted: 20 Aug 2002 05:14 PDT
Expires: 19 Sep 2002 05:14 PDT
Question ID: 56487
There is a theory in science that "one cannot measure anything without
effecting that which you measure".  Who wrote theory is this?
Subject: Re: Measurement or Physics
Answered By: voyager-ga on 20 Aug 2002 07:52 PDT
Hi alan123,

this sentence is one of the basic points in Quantum Theory. The most
popular example dealing with this sentence is "Schroedinger's Cat"
paradox as described in this article ( ) by Erwin Schroedinger, first
published in "Die gegenwärtige Situation der Quantenmechanik" in the
German publication Naturwissenschaften (1935).

You can find a nice discussion (which is probably easier to read than
Schroedinger's paper) about the paradox here ( )

The actual theory behind your sentence was mostly developed by Werner
Heisenberg and is called "The Uncertainty Principle" (sometimes also
called "The Principle of Indeterminacy"). Heisenberg worked together
with Bohr an together they created the Copenhagen Interpretation of
Quantum Theory ( ).
I think these quotes from Heisenberg are in line with the sentence you

"The more precisely the position is determined, the less precisely the
momentum is known in this instant, and vice versa."
--Heisenberg, uncertainty paper, 1927

"I believe that the existence of the classical "path" can be
pregnantly formulated as follows: The "path" comes into existence only
when we observe it."
--Heisenberg, in uncertainty principle paper, 1927

Understanding Heisenberg's theories is not a trivial task, so I am
going to supply a few links that might explain the points relevant to
your question:

Uncertainty Principle

The Uncertainty Principle

for a more in-depth understanding, you might want to read about the
Wave-Particle-Duality explained here ( ) and about Quantum Entanglement and
Causality ( ).

I hope this was helpful! I would have liked to write a more in-depth
answer, however, this is such an exhaustive subject that books have
been filled with it (if you need specific book recommodations, please
ask for them!).
Please feel free to ask for clarification should you require more
information on any specific point!


PS: One of the most famous quotes from the discussion about Quantum
Theory was Einstein’s “God does not play dice.” (he was trying to
disprove Quantum Theory with a number of thought experiments)

Additional Resources:

Heisenberg / Uncertainty Principle

The Page of Uncertainty

The Uncertainty Principle

Search Strategy:

quantum entanglement

schrödinger's cat

wave particle duality

uncertainty principle paper heisenberg
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