h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Something i have wondered about.

Is it thought that our sub-atomic particles are all unique?

What I mean by that is, is it believed that the universe began with a certain amount of electrons, quarks, photons, etc and that each one of them can neither be created or destroyed.

For instance, take photons. They can be absorbed. They can be emitted. They can be in transit. However, when they are absorbed, does the individual photon lose it unique identity, or is it somehow just bouncing about encasulated inside it new home.

Or as another analogy .....

Image an electron as a cannister of 3 tennis balls and also as a pitcher full of three cups of water. If it jumps to a different orbital around the nucleus is it as if it emitted a tennis ball, or as if it emitted a cup of water? The former would suggest that the photon was always present within the confines of the electron and simply set free. The latter implies that although the emission is still quantized, the emitted photon is now a mixture of the previous batch of photons.

Or the same with all other particles that are not known to decompose into smaller assemblies. Are we still playing with the original box of legos, or are the legos continually being melted down and re-manufactured on demand?

<< is it believed that the universe began with a certain amount of electrons, quarks, photons, etc and that each one of them can neither be created or destroyed.>>

didn't the universe start as energy and the energy 'cool' to coalese into particles, these particles then 'cooled' further to form more complex particles and then hydrogen atoms??

only after the energy 'cooled' into particles did we gat any gravity effects

Particles combine to form different particles all the time. When three quarks join to form a proton, there is one proton, not three quarks. When a photon is absorbed, it is gone. There is no photon any more.

"When three quarks join to form a proton, there is one proton, not three quarks"

Or is it just that a Proton is a collection of Quarks and Bosons?

Whose to say that when Quarks come together to form Hadrons that the Quarks themselves lose their identity?

Can a Quark be created or destroyed?

"When a photon is absorbed, it is gone. There is no photon any more"

How do you know? How can you be certain that it is not simply oscillating or entangled within the particle?

OK, let's look at it this way:

A down quark has a charge of -1/3. An up quark has a charge of +2/3. Two down quarks and an up quark join together to form a neutron, which has a charge of zero.

A neutron decays into a proton and an electron - with charges of +1 and -1 respectively. The electron is a fundamental particle with a charge of -1, but it wasn't present in any of the original quarks.

That's why I say the particles don't retain their identity when they combine to form new particles.

"A down quark has a charge of -1/3. An up quark has a charge of +2/3. Two down quarks and an up quark join together to form a neutron, which has a charge of zero"

A hydrogen atom consists of an electron (charge -1) orbiting a proton (charge +1). As an assembly they form a charge neutral atom. Still nobody argues that the electron and proton cease to exist individually. I don't accept charge cancellation as proof that they loose their individual identity.


"A neutron decays into a proton and an electron - with charges of +1 and -1 respectively. The electron is a fundamental particle with a charge of -1, but it wasn't present in any of the original quarks."

I think this is a better example, but I'm not sold on your argument yet. The electon could be attached in some way to the quark assembly without vanishing in analagous fasion to how it orbits a nucleus. With this decay, you end up with a proton. So all in all you started with an assembly of three quarks, an electron, and an Anti-Neutrino and the end result was a combination of the same parts only separated. The interesting part is that at least one of the quarks went from DOWN to UP. So unless the quarks themselvs are composed of smaller pieces the fact that one could spontaneously change it's spin I think implies that identity was lost somewhere.


That brings me to another question though. Since Quarks have Charges in thirds, it seems intutive to believe that they are in fact not fundamental and are more likely composed of even smaller entities of unit charge. In this fashion, the electron would thus really have a charge of -3. If so, possibly even electrons (or any leptons for that matter) aren't truly fundamental either. Is there any firm evidence against this being the case?

nihmble, I only gave one example - three quarks combine and then split to form three slightly different quarks, an electron and a neutrino (although I didn't mention the neutrino).

I suppose there could be really fundamental units that have a charge of one third and a mass of one third of an electron, but such a particle has never been observed.

" "When a photon is absorbed, it is gone. There is no photon any more"

How do you know? How can you be certain that it is not simply oscillating or entangled within the particle?"

How about the situation where an atom absorbes a photon of a specific wavelength, and emits photons of one (or more) diferent specific waveleengths?

"When a photon is absorbed, it is gone. There is no photon any more"

How do you know? How can you be certain that it is not simply oscillating or entangled within the particle?"
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The energy of the photon goes somewhere else, e.g. heat.

Photosynthesis and solar power wouldn't work otherwise.

Gnomon, DeadAngel, ............. you have me convinced.

So with all this having been said .... It there anything that we know of that is still the same exact pieces now that they were 13 billion years ago? Do all fundamental particles undergo transformations?

There's the CMB - Cosmic Microwave Background radiation. That's protons that have been travelling since the universe was pretty young. Of course they've changed a bit because the expansion of the universe has stretched their wavelengths. I would imagine plenty of other particles have remained undisturbed in space as well.

However, none of these will actually be from the big bang because the early universe was a very energetic place full of interactions.

Don´t you mean photons?

I want to point out something else about the uniqueness of fundamental particles.

You cannot label bosons and fermions. That is if you have two electrons, you cannot say "This is electron one over there is electron two". If you did some time later you would not know which one was which. Not only are particles therefore created and broken down but one cannot call an electron unique in a way that implies you can distinguish it from any other electron.

... cannot call an electron unique in a way that implies you can distinguish it from any other electron.
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If an electron was destroyed (?) wouldn't that make it "unique" from the others - and an electron on earth cannot be distinguished from one in say Andromeda?

If you look closely, you can see electrons have little serial numbers from when God created them.