# Observation and its role on objects/matter/particles

1. Feb 3, 2016

### Fred Boyd

As I understand it, in the double slit experiment electrons were found to exist in both wave and particle form depending on observation. The electron is a tiny speck of matter, and so does observation have the same effect on all matter? Max Planck said there is no matter as such. Is this because the wave function is the true nature of matter and physical substance only exists in observation?

Again, as I understand it, the measurement problem, says that an atom has no specific size or location until it's being measured in the act of observation and until observation collapse of the wave function the atom is a wave of probability, known as the superposition. All matter is made up of atoms and so I'm wondering if all atoms exist in a superposition/wave function without an active observer or observations? In other words, are the atoms that make up all matter in a superposition when an act of observation or measurement is not placed on them? Do all the objects I see around me change from particle to wave when I'm not here to observe them?

Does collapse bring into existence the particle, and thus all matter, or does it only apply to subatomic parts or a single atom? I could sum it all up with this. If a tree falls in the forest and no one is around to observe (witness) are there even any physical particles of a tree? Or are these particles in waveform and not specific to location in a superposition? It seems they would be immaterial waves, In a superposition,
and so would not have a specific location to fall from.

I asked these questions because in my research and study, I have read articles and watched demonstrations that have suggested the act of observation brings the whole physical universe into existence. With that said, I have also heard that science has managed to replicate the double slit experiment with things as large as molecules. This would suggest that matter outside the subatomic or atomic scale is not dual in nature and is fixed as a particle. Yet larger objects are made up of subatomic parts such as electrons.

2. Feb 3, 2016

### Staff: Mentor

Quantum objects - photons, electrons, quarks, neutrinos, all the rest of the subatomic zoo - are neither waves (as we usually understand the word) nor particles (as we usually understand the word). They obey the rules of quantum mechanics, which are rigorous and mathematically precise but lead to behavior unlike anything in the macroscopic world that we are familiar with. This fact was not widely appreciated almost a century ago when QM was first being worked out; and by the time we knew better these ideas of wave-particle duality and observation affecting whether an object would be a wave or a particle had taken root in the popular imagination. Furthermore, we had already started calling these quantum objects "particles", and the name has stuck - so when a physicist says "an electron is a particle" it doesn't mean anything close to "an electron is a tiny speck of matter".

It is true that all matter is composed of these quantum particles, and in that sense the behavior of all macroscopic objects is governed by quantum mechanics. This is somewhat analogous to the way that the behavior of macroscopic volumes of gas (for example, temperature and pressure and $PV=nRT$) can be derived from the laws governing the behavior of the individual molecules of the gas. Conscious observation plays no part in the underlying quantum mechanics and therefore also plays no part in the behavior of macroscopic objects composed of large numbers of quantum particles.

A good non-technical reference to the current state of quantum mechanics and macroscopic objects is Bruce Lindley's book "Where does the weirdness go?".

3. Feb 3, 2016

### Fred Boyd

Thank you. For a little more clarity on the superposition and the measurement problem I have a follow-up. Is my understanding as off, regarding this as it was with the double slit experiment and what particle wave duality means? Is an atom only specific to size and location in the act of measurement? Do the atoms that make up a tree not have a definite location to fall from in the superposition where their location/position is said to be a mathematical probability?

If the superposition is as I understand it, then does it apply to all atoms and thus all objects are in the superposition if not being measured?

4. Feb 3, 2016

### DrChinese

There is no simple answer to your question of whether atoms in trees have definite locations. An atom or a molecule can be made display the same quantum principles as an electron. There is no strict upper limit, it's more a matter of practicality.

Large molecules have been diffracted through a grating apparatus yielding (wave-like) interference.

http://qudev.ethz.ch/content/courses/phys4/studentspresentations/waveparticle/arndt_c60molecules.pdf