
Scientists Create Rare Fifth Form of Matter in Space - motiw
https://www.livescience.com/63999-fifth-form-of-matter-created.html
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TimTheTinker
Here's the Wikipedia article on laser cooling:
[https://en.wikipedia.org/wiki/Laser_cooling](https://en.wikipedia.org/wiki/Laser_cooling)

Its explanation is a bit too surface level for me. Anyone have more details on
the mechanism used for this experiment? Would they have used Doppler cooling
like is sometimes done on Rb-85?

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horstbort
Author here. Yes, Doppler Cooling is the first step used in the experiment, in
a Magneto Optical Trap [0]. It is followed by Polarization Gradient Cooling
[1] to overcome the Doppler limit. Atoms are still way too "hot" after this
step, so they are then transferred to a purely magnetical trap and cooled down
further via forced evaporation [2].

[0] [https://en.wikipedia.org/wiki/Magneto-
optical_trap](https://en.wikipedia.org/wiki/Magneto-optical_trap)

[1]
[https://en.wikipedia.org/wiki/Sisyphus_cooling](https://en.wikipedia.org/wiki/Sisyphus_cooling)

[2]
[https://en.wikipedia.org/wiki/Evaporative_cooling_(atomic_ph...](https://en.wikipedia.org/wiki/Evaporative_cooling_\(atomic_physics\))

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TimTheTinker
Thanks!!

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smhost
why does bombarding tightly-packed rubidium-87 atoms with lasers cool them to
minus 273.15 degrees Celsius?

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ars
The simplest way to explain it is this:

Atoms can only absorb very specific and exact frequencies of light. But
because the atoms are moving, the frequency of light, as seen by the atom,
varies a lot.

If you only shine light that is slightly below the lowest frequency of light
the atom can absorb, only those atoms that are moving toward the light (and
thus "see" a slightly higher frequency) are able to absorb that light.

Then the atom emits that light - which is always at the exact frequency. In
the process you basically "steal" energy from the atoms motion, and emit it
back out as ever so slightly higher frequency light.

Since the atoms are now moving slower they are colder. You keep doing this
until you've gotten as much out of the process as you can.

~~~
BurningFrog
So do the moving atoms "see" different frequencies because of doppler effects,
or something else?

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ars
Yes, doppler effect.

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miles7
There are way more than five phases of matter...

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Starwatcher2001
Please do educate us.

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lake99
The Bose-Einstein condensate that the article talks about is one of many low-
temperature states. There are a few kinds of high-energy states too... the
most famous ones being electron degenerate matter (found in white dwarfs) and
neutron degenerate matter (found in neutron stars).

I think a good starting point is here:
[https://en.wikipedia.org/wiki/State_of_matter](https://en.wikipedia.org/wiki/State_of_matter)

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jsjohnst
Better link (which was found in your link):

[https://en.wikipedia.org/wiki/List_of_states_of_matter](https://en.wikipedia.org/wiki/List_of_states_of_matter)

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miduil

            When groups of atoms are cooled to such unfathomably low temperatures, they stop moving as individuals and meld into one big "super atom." Tens of thousands of atoms suddenly become indistinguishable from one another, slowly vibrating on a uniform wavelength that can, theoretically, pick up the tiniest gravitational disturbances around them.
    
    

Why should this be called "super atom", just because all atoms behave the
same? If I have a bag of indistinguishable rice corns, they don't suddenly
become a single "super rice corn".

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ars
> If I have a bag of indistinguishable rice corns

Ah, but they actually are distinguishable. If you checked them, their size
will vary slightly, the exact position of the atoms making them up with be
different, etc, etc.

If you tried, you would be able to find _something_ different about every
single grain of rice - even if you had to check at the atomic level.

The thing about this condensate is the atoms _ARE_ truly indistinguishable.
Their motion, energy, absolutely everything about this is exactly identical.

But what _really_ makes them special is that they stay that way - they all
move together. (At least until they get enough energy to break apart their
bond.)

It's that last part that makes them into this "super atom" \- they are all
bonded together.

