Needless to say, at 19,000 Kelvin, the solid gold sample blew past that boundary, heating up to more than 14 times its melting point, which is about 1,300 Kelvin. The team suggests the speed of the heating likely kept the gold from expanding. They blasted the gold to its record-setting temperature in just 45 femtoseconds, or 45 millionths of a billionth of a second.

“The thing that’s intriguing here is to ask the question of whether or not it’s possible to beat virtually all of thermodynamics, just by being quick enough so that thermodynamics doesn’t really apply in the sense that you might think about it

The team notes that the second law of thermodynamics, which states that disorder increases with time, still stands—their work did not disprove it. That’s because the gold atoms reached their extreme temperature before they had time to become disordered, White tells Nature’s Dan Garisto.

Even still, researchers are now faced with a question they had considered all but completely solved nearly four decades ago, per New Scientist: How hot can something really get before it melts? If a material is heated quickly enough, there might be no limit, per the SLAC statement.

Sort of reminds me of the energy-time version uncertainty principle: if an interval is short enough, energy fluctuations can be extremely high.

What I’d like to know here is what the duration threshold to would allow fusion to start is.

Energy-time relations have no link to the uncertainty principle. They apply to classical cameras for instance. There are no “energy fluctuations”, you cannot magically get energy from nothing as long as you give it back quickly, like some kind of loan.

This is because the energy-time relation works for particular kinds of time, like lifetime of excitations or shutter times on cameras. Not just any time coordinate value.

Fluctuation implies going up and then back down within the dt, to me at least, so we agree I guess.

Fine, I can say this in a way that does not violate energy conservation but still uses the energy-time uncertainty principle:

Say you have a system with two levels, hot and cold like the gold sheet in this experiment. Then I can take a linear combination of these two (stationary) states, between which which the period of oscillation would be deltat=h/deltaE, which would be the time for the system to “heat” and “cool” within 45 femtoseconds. (lifted from Griffiths, page 143)

That would give a deltaE>1.5E-20J compared with kT (T=19000K) = 27E-20J (T=1300K) = 1.8E-20J so the fusion T is close to the oscillation limit, the extra energy for 19000K is not going to do anything unless the cooling slows down.

Soo…I don’t understand the point of the experiment. It just looks like they’re exciting atoms metal and then letting them quickly deexcite radiatively…and then wonder why they won’t absorb huge amounts of energy and melt (if the energy remained within the system, it would). I probably would have to get the actual paper, but I don’t wanna

Gold can be heated to 14 times its melting point without melting

With fast heating, sheets of gold can shoot past the theoretical maximum temperature a solid can have before it melts – raising questions about what the true limits are

New Scientist (www.newscientist.com)

“White and his team fired a powerful laser at a 50-nanometre thick sheet of gold for 45 quadrillionths of a second…”

As a rank amateur I don’t understand the other discussions here, but my thinking is that if a material is heated up for such a short period of time, and also only in a very small location (“The laser was focused to a spot approximately 100 µm in radius”), not across the whole mass, then the energy will dissipate across the mass of the material without building up enough to break the bonds and melt.

For me, what’d be more significant to know is how long it’d take for melting to occur/what’s the tipping point.

So I’ve skimmed through the journal article and:

https://www.nature.com/articles/s41586-025-09253-y

“Notably, the temperatures exceed the proposed limit of 3Tm in both cases for over 2 ps. This time is approximately an order of magnitude longer than the characteristic phonon oscillation period and, thus, much longer than required for homogeneous melting”

So the gold did melt, just not instantaneously!

“Our experimental findings raise an important question about the ultimate stability limit for superheating.”

Right so both news articles avoid stating that melting occured so far as to suggest it didn’t and that was what was significant…oh well, reading the journal article was interesting at least!

One question of mine I didn’t see was answered is, what significance do the xrays have on the temperature and time taken to melting?

I’m also no expert in this particular topic, but the heat transfer to the surrounding material shouldn’t play to huge a role. First because the material is very thin (50 nm) and second because the the X-ray focus is much smaller (5 um) so I would only probe the material in the middle of the heated spot.

The effect of the X-rays depends strongly on the intensity of the beam (which I can’t figure out on mobile ATM). X-rays can definitely melt or vaporize material of this thickness when the intensity is high enough. In this case here it hopefully shouldn’t affect the measurements to much.