
Physicists grab individual atoms in groundbreaking experiment - magoghm
https://phys.org/news/2020-02-physicists-individual-atoms-groundbreaking.html
======
pochamago
I don't understand why it takes at least three atoms to form a molecule. In a
cloud of hydrogen atoms, what is the third one doing in the production of h2?

~~~
amelius
Layman's guess. It probably has to do with conservation of energy and
momentum. To form a molecule, you have to change the energy state of the
electrons in both atoms, and in order to do so you have to respect the
conservation laws, so I guess it takes a third atom to absorb/provide the
required amounts of energy or momentum.

~~~
mokus
I think this is correct, and that a good illustration is planetary orbits - 2
bodies alone can never collide if they didn’t start out in intersecting
trajectories. They need a third to perturb their movements or they will just
keep orbiting the same way forever.

~~~
minitoar
Won’t the orbits decay due to tidal forces in some cases?

~~~
mokus
In reality, yes - for purpose of illustration, I was thinking of idealized
planets acting as point masses.

------
oceanghost
One step closer to us getting our matter compiler!

~~~
eternalny1
3-D printing materials like gold would destroy the world economy, that should
get interesting.

~~~
caymanjim
You can 3D print _with_ gold molecules, but you still need the molecules.
You're not going to be fusing junk atoms into gold atoms any time soon.

~~~
saagarjha
Well, you _can_ , it's just not economically feasible at all.

~~~
tyfon
You will need to stretch the definition of "can" here too, you need energy
equivalent to an exploding star or two neutron stars colliding [1] to make it
:)

[1]
[https://en.wikipedia.org/wiki/Gold#Gold_production_in_the_Un...](https://en.wikipedia.org/wiki/Gold#Gold_production_in_the_Universe)

