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Author Topic: How does a helium atom orient itself in a gravitational field?  (Read 2047 times)

Offline jeffreyH

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Is there a particular orientation of helium atoms when in a gravitational field? What I mean by this exactly is what is the general orbital configuration of electrons around the nucleus? Do they align in any way?


 

Offline alancalverd

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Since the s orbital is spherically symmetric, there is no definable orientation for the electron cloud under any circumstances.
 

Offline jeffreyH

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Since the s orbital is spherically symmetric, there is no definable orientation for the electron cloud under any circumstances.

Thanks for the answer. I thought this might be the case but had to make sure.
 

Offline syhprum

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The gravitational force on a single atom is infinitesimal and could have no effect on its orientation
 

Offline evan_au

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Over 99.9% of the mass of an atom (protons & neutrons) is concentrated in the nucleus, effectively a point mass.

The electrons are more distributed. Even if the electrons are not in the ground state (s orbital), the higher orbitals are still symmetrical, and centered on the nucleus. The electron's position is "smeared out" over the orbital, which represents the probability that an electron will be found at a particular position. So even the electrons wouldn't provide a gravitational orientation force. Tidal effects are negligible on these scales.

MRI machines realign the orientation of nuclei in a magnetic field, by application of a series of radio-frequency pulses. This does not apply to helium 4, since there are an even number of nuclei; it does occur for the much rarer Helium 3 (making up 0.0001% of Helium).
 

Offline jeffreyH

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The reason I asked was I was reading up on Coulomb potential wells and quantum effects. The fact that every particle in the universe can be thought of as linked together in one whole system got me thinking. As an atom can be thought of as seeking out a partner to bond with to lower the overall energy this can be thought of as the sub-atomic equivalent of gravitation and can act at remote distance according to theory. Gravitation is treated as having infinite range and so there is an analogy, gravity being everywhere at once with most of the wave functions cancelling out at the more remote points. However being an inverse square this does not fit with theories of elementary particles.
 

Offline evan_au

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There are a few things that puzzle me here, Jeffrey. As I understand it:
Quote
an atom can be thought of as seeking out a partner to bond with to lower the overall energy
  • Many types of atoms bond do with others to lower the energy, effectively completing their outer shell of electrons.
  • But Helium (and all the noble gases) already have a complete outer shell of electrons, and so don't form many stable compounds at all.
Quote
gravity being everywhere at once with most of the wave functions cancelling out at the more remote points
  • Coulomb forces from protons (+) and electrons (-) in neutral atoms do cancel out at long distances.
  • However, as far as we know, there is no anti-gravity. Since gravity is only attractive, it does not cancel at long distances, and so it follows an inverse square law.
  • This is similar to Coulomb forces from an unbalanced charge (eg an isolated electron or proton), which also follows an inverse square law and continues to infinity (in theory).
  • The Coulomb force is separate from the wavefunction of an electron; the amplitude of an electron's wavefunction decays rapidly beyond the size of an atom (or the wavefunction of a proton, which decays rapidly beyond the size of a Helium nucleus).

Quote
[Gravity] being an inverse square [law] does not fit with theories of elementary particles
There have been a number of attempts to unify quantum theory & gravitation.
  • On larger scales you can just consider gravitation as an inverse square law, as described in General Relativity, and ignore Quantum effects.
  • On smaller scales you can just consider Quantum Theory and ignore Gravity.
  • On both scales, effects like time dilation apply.
  • There are some pesky conditions like atomic-sized Black Holes and the edges of macroscopic black holes where we don't yet have a self-consistent theory, let alone a provably correct theory....
 

Offline jeffreyH

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There are a few things that puzzle me here, Jeffrey. As I understand it:
Quote
an atom can be thought of as seeking out a partner to bond with to lower the overall energy
  • Many types of atoms bond do with others to lower the energy, effectively completing their outer shell of electrons.
  • But Helium (and all the noble gases) already have a complete outer shell of electrons, and so don't form many stable compounds at all.
Quote
gravity being everywhere at once with most of the wave functions cancelling out at the more remote points
  • Coulomb forces from protons (+) and electrons (-) in neutral atoms do cancel out at long distances.
  • However, as far as we know, there is no anti-gravity. Since gravity is only attractive, it does not cancel at long distances, and so it follows an inverse square law.
  • This is similar to Coulomb forces from an unbalanced charge (eg an isolated electron or proton), which also follows an inverse square law and continues to infinity (in theory).
  • The Coulomb force is separate from the wavefunction of an electron; the amplitude of an electron's wavefunction decays rapidly beyond the size of an atom (or the wavefunction of a proton, which decays rapidly beyond the size of a Helium nucleus).

Quote
[Gravity] being an inverse square [law] does not fit with theories of elementary particles
There have been a number of attempts to unify quantum theory & gravitation.
  • On larger scales you can just consider gravitation as an inverse square law, as described in General Relativity, and ignore Quantum effects.
  • On smaller scales you can just consider Quantum Theory and ignore Gravity.
  • On both scales, effects like time dilation apply.
  • There are some pesky conditions like atomic-sized Black Holes and the edges of macroscopic black holes where we don't yet have a self-consistent theory, let alone a provably correct theory....

Well I hate helium, in fact all the noble gases. Anything you can think about how gravitation might work is destroyed by them. The point about ignoring gravity on quantum scales is well made and probably not properly appreciated. I am reviewing the Schwarzschild equation for the event horizon at the moment but although what I am thinking makes sense it is backwards. However it does describe a collapsing spacetime and is an elegant solution, but it still does not say what gravity actually is.
 

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