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QUESTION: Hello Dr. Nelson,
Just two quick questions. 1- Are quarks theoretic or have their existence actually been confirmed? 2- Has there even been a photograph taken of an electron or does the uncertainty principal make that feat impossible?
Thank you.

ANSWER: Their existence is consistent with all our measurements, but we're still in the early stages of experimental study of things such as quark-gluon plasma.  The difference between a crackpot and a good scientist is that a good scientist is willing to consider alternatives when approached with new evidence.  Confirmed?  I'd say most scientists would agree that's true.  Their deeper structure and nature?  Still up for some debate and further experimentation.

Photograph?  Not in film, per se, but atomic force microscopes have imaged single atoms.  Since the structure and shape of an atom depends on its electrons, you could say that they have been imaged.

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QUESTION: Hello Dr. Nelson,

  Thank you for your relpy. I found it helpful. I do however have to clarify as tho the proven existence of quarks. I basically need a, "Yes they have been proven to exist 100%", or a "No, proof is not yet established 100%." regardless of what the popular theories are. Popular belief in something does not make it proven. Let's face it, scientists are the first to exclaim that, as an example, paranormal phenomena, regardless of the amount of popular "theories" a group may have, does not make any of if fact until there exists undeniable, testable and retestable "Proof" of it's existence. Does such "Undeniable Proof" exist for the existence of quarks or at this time, are they still theory, regardless of popularity of the opinions of the masses?

I have a new question that has been on my mind too and I hoped that you could help me with the answer. Should the universe eventually become heat dead, will gravity be at all affected? Will it still exert it's force over a cold dead universe?

Okay, one more... in your opinion, can a force exist without a particle?
For example, does there have to be a "graviton" for gravity to exist or can it just exist as a force unto itself?

Thank you very much again for your time.

There's no proof 100% that the universe isn't a hologram and that anything truly exists, science doesn't work that way.  So no, but there's evidence enough that a wide jury of very very good physicists believes in them.  That's not "popular belief," that's science.  You're picking at straws here, and bringing in paranormal phenomena is a really bad comparison.

As far as we know, gravitation will not be affected over the life of the universe, that's speculation.  

The jury is out on the graviton, none has ever been detected and so we don't know about it yet.


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Dr. Stephen O. Nelson


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.


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.

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

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