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QUESTION: Hi,

I read that in quantum physics, if we detect the motion of electron, the electron behaves like a wave else it behaves as a particle in 2 slit experiment. How does the electron know that it is being detected and change its behavior. Also some religious people are using the quantum phenomenon to prove that science cannot explain all observable phenomenon and hence super natural powers exists in the universe. Please explain.

regards.

ANSWER: We need precise terminology here.

Electrons don't "know" that they're being detected.  Their basic nature is affected by the same interactions that cause the measurement.  They're not conscious, they're particles.

The people who try to mix physics with the supernatural or social/psychological are fundamentally flawed from the get-go, so I can't explain.  I was, however, at the lecture on this at Duke when I was in grad school... http://en.wikipedia.org/wiki/Sokal_affair  http://www.physics.nyu.edu/faculty/sokal/transgress_v2/transgress_v2_singlefile.
Perhaps that will give you a better perspective.
Idiots...

---------- FOLLOW-UP ----------

QUESTION: Thanks for your reply. I am sorry I could not understand the below statement. Can you please explain further.


"Their basic nature is affected by the same interactions that cause the measurement"


How does electron change its behavior just because they are detected. Does the detectors interact with the electrons?

ANSWER: Yes, the detector must interact with the electron in order to detect it.  As much as quantum mechanics extends our understanding of the universe beyond Newtonian physics, the basic principles still apply.  Equal an opposite reactions are still a fundamental basis of our understanding of physics.  If you wish to affect the instruments of measurement in order to cause a measurement, you necessarily create reaction to the particle being measured.  While on the macroscopic level we can ignore the tiny measurement forces, on the quantum particle level you create serious interaction with the particles being measured.  Keep in mind, an electron has a mass of just under 10^-30 kg.  A single 1L bottle of water has a mass of 1 kg.  The entire planet has a mass of about 6*10^24 kg.  So an electron is ridiculously tiny!  Yes, any measurement of an electron requires it to exert an effect on some kind of probe, and of course such a hilariously small object will always be affected by that kind of measurement.

---------- FOLLOW-UP ----------

QUESTION: Thanks for your reply. How could quantum entanglement of electrons can be explained logically. How could electron instantaneously correlate with each other although they are separated by distance.

Thanks

Answer
The basic nature of quantum entanglement is still at the forefront of research physics.  You can do a lot of mathematics behind it (the ultimate logical explanation), but that is waaaay beyond the scope of this forum if you want to get that deep into it.  If you're that interested, you'll need to start taking formal quantum mechanics classes to really have a deeper understanding.  There's no shortcut for that right now, no quick explanation of quantum entanglement that I'm aware of.

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Dr. Stephen O. Nelson

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I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

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I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

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Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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