Atoms

The question is a bit confusing but I'll have a go. I'm sure others will as well.When you say at the molecular level I presume you mean what cause atoms to bind together into molecules. This is, as far as I know, very, very well understood.It is the electromagnetic force mediated by photons being exchanged that holds molecules together.The theory that describes this behavior is, I think, QED (quantum electrodynamics). This was developed orginally by R. Feynmann. It is a very precise theory. That is calculations done using it produce results that have been as accurate as the very best tests done. They are accurate to around 10 or so decimals.Can you tell us more about where you "heard"? One thing for sure is that lots of people say lots of things out of abject ignornance (me too, now and then ). The lesson might be not to believe everything you hear.

Ok, perhaps the question is in regard to atoms themselves separate from their incorporation into molecules.There are several parts to this, (warning now I'm really becoming uncertain of how firm all this is):1) Holding electrons around the nucleus.
This is also electromagnetic. The nucleus is positivly charged and electrons carry a negative charge.2) Holding protons and neutrons together in the nucleus.
Since neutrons carry no charge and protons are positive the nucleus has an electromagnetic force pushing it apart. This is where the strong nuclear force comes in. The neutrons and protons are bound together by the strong force. (IIRC, bosons are the exchanged particle). There have to be enough neutrons in the nucleus to "balance" the protons. Smaller nuclei have equal numbers of protons and neutrons (generally). As the atomic number goes up it starts to take more than an equal number of neutrons to hold it together. Eventually a nucleus can't be held together even with a significant excess of neutrons ( e.g., Uranium 238 has 92 protons and 146 neutrons). These elements are always radioactive.3) What holds the protons and neutrons together.Gluons hold them together. Gluons, I think, might have been detected in the very latest "atom smasher" experiments. Protons and Neutrons are made of "quarks" ( a term from James Joyce IIRC).That is probably as much detail as anyone could want. It is probably more than you wanted.What you 'heard' is correct in that we don't know everything. But it is very, very wrong given the amount that is known about this stuff.

I have Feynman's autograph on his "Character of Physical Law". He spoke here about 20 years ago.

huh? I'd say "no".Taste or oder are a chemcial reaction. The substances that make up the compounds that are involved in that reaction are made of atoms. There is nothing else there so, in that sense, the atoms do taste or smell.

Sell it?!!! I'm not squeezed into the new place enough to force me to do that.However I do have a number of moderately good condition Mad magazines from the '55 to '57 time frame.Also, as hard as it is to contemplate, I'm going to pack up my complete (I hope) from issue 1 of Isaac Asimov's Science Fiction magazine and put it on Ebay.

Yukawa (an abysmally bad lecturer - he visited the physics dept I was working in -- it wasn't much more than a hello)
Samulson (economics -- just a short discussion after a talk)
Freeman Dyson (another discussion about SETI etc. His son lives near here)So does, btw, Spider Robinson whom I've spoken to a few times in our local Science Fiction book store.Gloat!
This message has been edited by NosyNed, 11-20-2004 04:12 PM

This may very well be incorrect, but I think there is a very, very slight difference in the spectrum of the different isotopes. If it is there it is very small. We need a physicist to clear this up.

Yes, but not by looking at just one frequency. Different elements emit light in very specific patterns. That is what spectroscopy is all about. Have a look at this reference:http://hyperphysics.phy-astr.gsu.edu/.../quantum/sodium.htmlIf you see the same pattern but in the "wrong" place you can tell it has been shifted. (you could Google "hydrogen alpha line" too )IIRC, it was the pattern of lines from hydrogne (alpha and so on) that was first recognized as being in the "wrong" place.One frequency at a time I don't think one could tell.