swansont

! Moderator Note Yes, it was, and yet you’ve opened a new thread. Don’t do it again. The common theme is James Maxlow's theory of "Earth Expansion Tectonics that you brought up. One thread per topic.

If it has mass, then we can say it’s matter, since that’s one of the properties that define matter. “grooves left by stars”?

I think people are conflating time and time measurement, and I will reiterate: Is there a testable hypothesis here? A model, or evidence?

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What part of GR states this?

Is there a testable hypothesis here? A model, or evidence?

No, it isn’t. The technique is called electromagnetically induced transparency (EIT). The problem here is that the article you read was filtered through the reporter and watered down. Information was omitted. But you won’t notice this if you lack understanding of the physics involved. You just see the buzzwords, and compare them to other buzzwords. It’s like using Cliff Notes for literature. Reading a summary of the book rather than the book itself. There are difference between the experiments, but AFAIK using EIT is not one of the differences. (it would be nice to check, but you need to link to journal papers or the ArXiv preprint to see those details)

You’re just trolling me now.

Not making a dent, am I?

780 nm is the resonance for Rb. The resonance frequency for Rb is ~3.85 x 10^14Hz. (that’s 780 nm) Because the atoms are moving, there is a Doppler shift, that resonance can be higher or lower, depending on that motion. The Doppler shift is up to 500 MHz for a significant fraction of the atoms*, so to be resonant with some of them, you need to be within 500 MHz of 3.85 x 10^14Hz. *the atoms move with speeds that depend on temperature. It’s a distribution of speeds; some move fast, some slow.

Right. The motion of the atom means it will absorb light at a lower frequency than its resonance frequency. For the emitted photons, for every redshifted photon you would get a blueshifted one, on average. The resonance is not at 500 MHz. I explained this. That’s how wide the resonance is - if you are within 500 MHz of the resonance, the photon has the highest chance of absorption.

This reminds me of those folks who insist that their perpetual motion machine will work, and won’t listen to anyone who tells them different. Yes, the doppler shift will be changed slightly. That’s why you need millions of photon scatters to slow an atom to close to zero velocity - the imparted momentum from a single photon is small. p=E/c, and c is a big number. If the cloud is big, light won’t penetrate unless it’s being re-emitted, and that’s in a random direction. Light from random direction won’t cause slowing; there’s no net force being applied It’s usually described in terms of the force, which is in the direction of the laser (looking at a 1-D example). But yes, the emitted light would be slightly more energetic.

A MOT traps neutral atoms, not ions. That’s part of the problem. If you need a few mW/cm^2, and your optics are ~5 cm in diameter, that’s about 40 mW. Six beams, that’s 240 mW. Losses from acousto-optic modulators to tune the laser frequency is a factor of 2. Maybe another factor of 2 for other losses. Basically you need a watt for that. Now you want to scale this up by a factor of 20, which means the area goes up by a factor of 400. You need a 400 watt laser. Huge problem #1 You need 1 meter windows for your vacuum system. Optical-quality flat. If you can find them, they would be super expensive. Problem #2 But it’s probably all for naught, because a 1 meter cloud of atoms will be optically thick, meaning the laser light won’t penetrate, and the re-radiation would cause heating. You would likely not be able to get a 1m cloud of cold atoms to begin the process of forming a BEC.

https://en.wikipedia.org/wiki/Magnetic_trap_(atoms) magnetic trap and magneto-optic trap are two very different things (“optic” meaning photons are involved) But hey, you’ve got your youtube degree, so...whatever.

Sure I can. Physics backs me up. “kinda similar” is not much of an argument; a quadrupole magnetic field + a laser is not “kinda similar” to the capacitor plates Changing the sign does nothing. You still have an unstable equilibrium. If the atom is not at rest at the exact center, it feels a force. And it will never be at rest. In this case it will be attracted to a one of the plates. And this is not the case for either of the electrostatic cases. You don’t have a stable equilibrium.

This won’t work. “Earnshaw's theorem states that a collection of point charges cannot be maintained in a stable stationary equilibrium configuration solely by the electrostatic interaction of the charges.” https://en.wikipedia.org/wiki/Earnshaw's_theorem Guesswork is not a replacement for knowledge (studiot expressed a similar sentiment earlier) In this case, if the atom is not at rest at the exact center, it feels a force. And it will never be at rest. The atom will eventually leak out

How would this trap the atoms? I’m looking for a physics answer, not a WAG. Put another way: provide a link to anyone who has trapped atoms like this. I’ve told you this won’t work, and you haven’t detailed how it could work, so why are you asserting that it will? Physics is not magic. Wishing does not make it so. Invoking a few key words is not an incantation that will give you your desired result.

They aren't. The spin of the proton is aligned with the magnetic field in MRI - pointing in that dierection. That doesn't mean the atoms are lined up in a line. Spin is quantized. You can't reduce the spin. You reduce the CoM motion. Spin is quantized. All you can do is change the orientation of the spin. Yes, there is a field, but the force is optical, not magnetic. The function of the field is to Zeeman shift the resonance of the atom. Without the magnetic field you have what is called optical molasses. Cold atoms where the lasers overlap, but not confined. You don't get as many atoms in a molasses, but you can get them colder by letting the cloud expand (in a BEC, the next step is a magnetic trap, and then evaporative cooling)

What does that have to do with its temperature? (which is CoM motion) Depends on what you mean by "lined up" There will always be motion, and some spatial extent. But if you want more confinement, you should use a linear ion trap, which has a stronger restoring force, coupled with laser cooling. At this point I have to wonder if you are doing this deliberately. (after it's been brought to your attention twice in the last few days) A 2-D MOT uses both magnetic fields and lasers. Magnetic traps are not very deep, so they will only confine atoms that are already cold. It would not have a "wider coverage"

Precession won't cool the atom. Laser cooling by itself doesn't cause confinement. No, the 500 MHz is a feature of the atoms (owing to their innate width and thermal motion), not the laser. The laser is at 780 nm, which is ~ 4 x 10^14 Hz Again: MRI and laser cooling are not the same thing. You can't mix and match them. You're still doing this? The confinement is from the light, but the presence of a particular magnetic field gradient (a quadrupole field) makes the force position-dependent, so the atoms will be at rest at the zero point of the magnetic field. You can do that with the proper magnetic field gradient. It's a 2-D magneto-optic trap, sometimes called an atomic funnel.

The transition that you use in MRI is not the same as you use in laser cooling. In MRI you cause Larmor precession at a frequency that's resonant because you have put on a magnetic field to match the frequency of the RF. The emission pattern of the radiation is laser cooling is isotropic, which is why the force from emission averages out to zero. As far as I know this is not the case for MRI interactions. If the incoming and outgoing photon are in opposite direction, so net momentum change occurs — the atom doesn't slow down. Cooling and trapping requires that you scatter enough photons before the atom has passed through the interaction region. If you don't do this, the atom will not be trapped. If it passes through it then hots the vacuum chamber wall or, since the "dark vacuum" still has background gas, some other atom, and re-thermalizes. Even if you managed to trap an atom or two, these collisions will liberate them from the trap. You use the optical frequency of the D2 transition (which minimizes the optical pumping I mentioned earlier) which for Rb is at ~780 nm The 500 MHz they mention in the wikipedia article is ∆w, which is the Doppler-broadened width (FWHM = full width at half-maximum) of the transition, not the transition frequency. IOW, the laser has to be within about 500 MHz of the center to be resonant with one of the atoms in the thermal distribution (the Maxwell-Boltzmann distribution that is mentioned). They mention the natural line width of 6 MHz, which is true for any Rb atom at rest. That's how closely you have to tune the 780 nm light to be most likely to be absorbed by a particular atom. Here is a trace from this paper https://advancedlab.physics.gatech.edu/labs/SaturationSpectroscopy/SatSpecManual.pdf It shows the saturated absorption signal of the D2 transitions in Rb for both isotopes (around 500 MHz FWHM) and the individual structure because they are doing Doppler-free saturated absorption, which can show the transitions for the atoms with v=0 in the ensemble. Those are nominally 6 MHz wide, but broadened by other effects, like laser power.

I'm not sure why that matters in general, or to the applicability of Ockham's razor.Whether they typical human being understands some bit of science is not why we pursue the science. I think the concept applies to more than science, and is not anywhere near a full description of the motivation of new science. Yes, you might do science to find a simpler explanation, but people also do new science because current science is incomplete, or possibly wrong, and to realize experiments of theory where the technology has caught up, or to push the limit of what experiment can do. Those have nothing to do with having the simplest explanation. There are places where it has been applied. We had some data suggesting superluminal neutrinos some years back, but the simplest explanation was experimental bias/error, and that's precisely what it turned out to be. The more complex explanation - that there was new physics - was not going to be adopted without a whole lot of confirmation, because of another adage: extraordinary claims require extraordinary evidence. Which, if you think about it, is just another version of Ockham's razor (much like we have multiple ways of stating the second law of thermodynamics)

I was referring to the magnetic field for MRI, to point out that it’s not what you need for cooling. For Rb? I expect the photon transition rate would be lower, and the photon momentum is smaller, as compared to laser cooling. I doubt you get significant cooling.

In MRI the water is confined because it’s in an organ. Magnetic trapping isn’t involved. I’ve been doing laser cooling for almost 30 years. I like physicsgirl and veritasium videos (I met Derek once, several years ago) but I’m not going to learn any experimental details from watching this. In laser cooling you tune below the resonance, so the doppler shift moves you closer to resonance. Laser cooling works because the light slows the atom down - the absorption is from one direction, so there’s always a momentum “kick” from that direction. The momentum kick from the emissions cancel, because it’s isotropic. You don’t have this arrangement in MRI. Or the same magnetic field arrangement (and we haven’t discussed the problem of optical pumping yet) You can suspend an atom in a vacuum system with laser cooling because there’s more than enough force (you can easily get 100 g’s of acceleration). How much of a force can you get with microwaves?

No, not really. The confining force in a magneto-optic trap comes because photons have momentum. You put lasers along all six directions (+/- for x, y and z) The magnetic field means the light causing confinement is closer to resonance. so you get more light being absorbed that gives a force toward the trap center. The recoil of a visible photon changes the speed of an atom of order 1 cm/sec. MRI uses photons perhaps a million times less energetic.