I guess, start at -1 Kelvin or Rankine? No reason why nothing can Get below 0 K , or -273 C. That would be -274 C. Its just that no more molecular movement seen at absolute zero. It won't get any "less" or "go backwards" any more than freezing water to 0 F makes it "harder" than at 31.
People used to think Sun orbited Earth, and Earth flat. Fahrenheit put Zero on his scale because it was lowest he could record. People also
thought atoms indivisible. And, X-rays harmless because you can't feel them. Also very recently thought only 3 particles to the atom.
I understand those who argue that temperature is a measurement of average kinetic molecular motion., and no motion means, in this sense, no temp. But, if instruments record a number below absolute zero, it is still a valid reading. The molecules will not get "stiffer" or have less motion. Freezing H20 to 0 F makes it no "harder" than at 31, as said; but it does require more heat or time to go back to liquid. Think of it That way.
And ,the practical problem of any sensor reading anything when its molecules are now at absolute rest. Again, we once thought Earth Flat, too..
With vacuum, if you have an absolute of zero microns (in practicality, impossible), you cannot go "negative", no. But , this is different concept.