Physicists Induce Motionless Quantum State In Largest Object Yet (newatlas.com) 31
Scientists have managed to slow down the atoms almost to a complete stop in the largest macro-scale object yet. The research has been published in the journal Science. New Atlas reports: The temperature of a given object is directly tied to the motion of its atoms -- basically, the hotter something is, the more its atoms jiggle around. By extension, there's a point where the object is so cold that its atoms come to a complete standstill, a temperature known as absolute zero (-273.15 C, -459.67 F). Scientists have been able to chill atoms and groups of atoms to a fraction above absolute zero for decades now, inducing what's called the motional ground state. This is a great starting point to then create exotic states of matter, such as supersolids, or fluids that seem to have negative mass. Understandably, it's much harder to do with larger objects, because they're made up of more atoms which are all interacting with their surroundings. But now, a large international team of scientists has broken the record for largest object to be induced into a motional ground state (or extremely closely to one, anyway).
Most of the time, these experiments are done with clouds of millions of atoms, but the new test was performed on a 10-kg (22-lb) object that contains almost an octillion atoms. Strangely enough, that "object" isn't just one thing itself but the combined motion of four different objects, with a mass of 40 kg (88 lb) each. The researchers conducted the experiment at LIGO, a huge facility famous for detecting gravitational waves as they wash over Earth. It does this by beaming lasers down two 4-km (2.5-mile) tunnels, and bouncing them back with mirrors -- and those mirrors were the objects that the new study cooled to a motional ground state. The photons of light in LIGO's lasers exert tiny bumps on the mirrors as they bounce off, and these disturbances can be measured in later photons. Since the beams are constant, the scientists have plenty of data about the motions of the atoms in the mirrors -- meaning they can then design the perfect counteracting forces. To do so, the researchers attached electromagnets to the back of each mirror, which reduced their collective motion almost to the motional ground state. The mirrors moved less than one-thousandth the width of a proton, essentially cooling down to a crisp 77 nanokelvins -- a hair above absolute zero. The team says that this breakthrough could enable new quantum experiments on the macro scale.
Most of the time, these experiments are done with clouds of millions of atoms, but the new test was performed on a 10-kg (22-lb) object that contains almost an octillion atoms. Strangely enough, that "object" isn't just one thing itself but the combined motion of four different objects, with a mass of 40 kg (88 lb) each. The researchers conducted the experiment at LIGO, a huge facility famous for detecting gravitational waves as they wash over Earth. It does this by beaming lasers down two 4-km (2.5-mile) tunnels, and bouncing them back with mirrors -- and those mirrors were the objects that the new study cooled to a motional ground state. The photons of light in LIGO's lasers exert tiny bumps on the mirrors as they bounce off, and these disturbances can be measured in later photons. Since the beams are constant, the scientists have plenty of data about the motions of the atoms in the mirrors -- meaning they can then design the perfect counteracting forces. To do so, the researchers attached electromagnets to the back of each mirror, which reduced their collective motion almost to the motional ground state. The mirrors moved less than one-thousandth the width of a proton, essentially cooling down to a crisp 77 nanokelvins -- a hair above absolute zero. The team says that this breakthrough could enable new quantum experiments on the macro scale.
How does this work with relativity? (Score:2)
Sorry for my country bumpkin question, but if everything is in motion in some other inertial frame, and still in another inertial frame, what does it mean for it to be motionless?
Feel free to not give me the whole answer -- just a reference or something would be fine.
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I believe that the frame relevant to the object itself is the crucial one, and specifically the delta of the particles of the object relative to each other. Admittedly this is a layman's conclusion, not a scientist's.
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Yeah, they mean the "jiggling" of the atoms. So if the whole object is moving at a constant speed but the atoms within it are not jigling around, that's absolute zero (which isn't actually achievable, just approachable)
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What's most surprising to me, is that they've apparently managed to turn four 40 kg objects into one 10 kg object. That operation must have created a gigantic amount of energy. Unless some journalist managed to screw up the report, which of course is always a possibility...
Reduced/effective mass (Score:5, Informative)
When you have a coupled system of multiple masses oscillating, you can sometimes describe the collective motion using something called the "reduced mass" https://chem.libretexts.org/Co... [libretexts.org] . Basically, in some cases, you end up being able to describe the motion of multiple masses using the same equations you would for a single mass, if you redefine the "mass" that you use in the equations. This "reduced mass" is a property of the overall system, and is dependent on the "actual" masses of all the constituent parts and how they interact.
In this experiment, they had a system of 4*40kg masses that were coupled together in such a way that the system had a reduced mass of 10kg. It is thus perhaps a journalistic simplifcation to say "this is one 10kg object"
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Thank you for that clarification.
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Physics is all about building useful models, where the meaning of "useful" depends very much on the context.
Is it fair to treat the air around us as lots of little hard spheres that bounce off each other? Yes, if the ideal gas model is a suitable description of what I'm trying to understand or explain.
But.. air "really" consists of molecules of oxygen and nitrogen and so on. So maybe it would be "fair" to say I've got O2 and N2 and we should think about the way they interact using some slightly more realist
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It's okay, that is simply the typical type of journalist mistake that it is the Editor's job to fix.
Ah.
Re:How does this work with relativity? (Score:5, Informative)
Re:How does this work with relativity? (Score:4, Funny)
Re: How does this work with relativity? (Score:2)
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Quantum State with Almost No Relative Motion (Score:2)
what does it mean for it to be motionless?
It means that each atom in the object is motionless with respect to all the other atoms in the solid i.e. every atom in the solid is in the exact same inertial frame. In any "normal" solid at a finite temperature, each atom has a random thermal motion so that in general any two atoms in the solid will have a relative motion between them.
Viewed at from a different inertial frame the object will still be moving but every atom in the object will be moving with exactly the same velocity. Hence, a more accur
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"the desire for a click-bait headline seems to be a vain hope in today's world."
And in yesterday's world, for that matter. Carlin's bit comes to mind, that having "Ten" Commandments was a marketing decision.
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Well said :D
Re: How does this work with relativity? (Score:1)
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I love the sleepy slowmo Biden jabs quickly followed by frothing hostility towards the Biden Agenda. It's like watching Gollum!
Cool (Score:1)
Lasers - so hot right now.
IANAP but not rOnlyeally physical mass it seems? (Score:3)
Thanks to previous poster who explained the concept of Reduced Mass.
Caveat IANAP and only saw the abstract on the Science site and skimmed the below Wikipedia article on reduced mass.
While it is apparently relevant to calculations of noise in beams, and is generally a cool way to turn a two-body problem into a one-body problem, it sounds like they didn't actually cool anything physical but "cooled" the mathematical abstraction called reduced mass by physically moving mirrors (which are not at absolute zero) back and forth with electromagnetic actuators. Is this interpretation correct?
Actually I had thought we were at the level of cooling molecules but this page says in 2014 a cubic meter of copper was cooled to 6 mK. Granted TFA is about nanoKelvins.
https://www.coolingpost.com/wo... [coolingpost.com]
Wikipedia for reduced mass says: ...
In physics, the reduced mass is the "effective" inertial mass appearing in the two-body problem of Newtonian mechanics. It is a quantity which allows the two-body problem to be solved as if it were a one-body problem.
The reduced mass is typically used as a relationship between two system elements in parallel, such as resistors; whether these be in the electrical, thermal, hydraulic, or mechanical domains. A similar expression appears in the transversal vibrations of beams for the elastic moduli.[4] This relationship is determined by the physical properties of the elements as well as the continuity equation linking them.
Re: IANAP but not rOnlyeally physical mass it seem (Score:2)
Nothing to worry about... (Score:2)
Frozen mirrors? (Score:2)
Wouldn't freezing the mirror like that render the mirror useless?
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you may aim for "funny" but it simply depends on the level of relativ humidity in the medium surrounding the mirrors