Ask-a-Physicist by Topic

Quantum Mechanics

Infrared and Blackbody Radiation

Is there a particular range of frequencies at which parts of the human body (or the human body overall) normally vibrates? Because in an episode of the sci-fi TV series Fringe, they claimed that they could figure out if one character was from this universe or a parallel universe by measuring the frequency at which he was vibrating.


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Photon Entanglement

Hello, I am trying to figure out the practice behind the experiment I've heard about in a National Geographic documentary, so please help me a bit.

How do they generate entangled particles in the lab (photons)? Also, how do they make photons to interact with each other and what kind of interaction do they make?


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Planck Scale

My 7 year old son Ben (who is sitting next to me now) has recently become interested in how small things can be. He is not convinced that nothing can be measurably smaller than a Planck length because whatever is Planck sized can always be divided into something smaller.

He thinks perhaps Planck lengths can be divided into energy beams that then become infinite.


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Simultaneity in modern physics

Does Einstein's relativity of simultaneity mean that two events cannot be simultaneous or that we cannot prove that two events occurred simultaneously?


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Wave and Particle Duality

I have a question about waves and particles. Since waves and particles seem to be somewhat interchangeable at the subatomic level, at what wavelength does the wave / particle duality stop?


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Atomic sizes As the nucleus gains mass by adding protons and neutrons does the size of the nucleus increase into the empty space of the atom or does the innermost orbital move away from the nucleus? Basically, is an atom of Ununoctium larger than an atom of Sodium?
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The Weak Interaction

In the proton-proton chain reactions which happen, for instance, in our Sun, two protons collide and form a proton and a neutron. However, this just blows my mind.

What is the mechanism by which a proton simply loses its charge, becomes slightly more massive, and turns into a neutron?


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Super-Kamiokande neutrino detector in Japan. Image Credit: Univ. of Tokyo I am lost about neutrinos. I thought a neutrino was just a neutrino since it is neutral. What are the differences between electron, muon, and tau neutrinos?
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universe How was the universe created if physics states matter can neither be created nor destroyed?
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electric-dipole-tn What is an electric dipole?
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standard-model

If the recent result of the tests of the speed of the neutrino are validated by other research groups what are its implications for the standard model of particle physics as it has been described to date?


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minos-detector

There seems to be a lot of debate about how accurately CERN measured the departure of their neutrinos. Could they not aim them at some other neutrino detector in the world and just use the difference in distance and time from the readings in Italy as this would eliminate the error in not knowing exactly when the neutrinos left CERN?


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double split

When carrying out the double slit experiment using electrons or buckyball molecules, do the particles have to be traveling at near light speed velocities to produce an interference pattern?


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beam An electron beam, such as the one found in a TV picture tube, is composed of negatively charged electrons. Why is it that this beam does not rapidly spread out owing to the electric repulsion? I realize that the tube has various focusing magnets and such, but I would think the electronic repulsion would be a serious problem. - JT, Buffalo Grove, IL
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