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For the first time, scientists have watched a chemical reaction happen from beginning to end without any missing pieces. Kang-Kuen Nis lab at Harvard University chilled molecules to within a millionth of a degree of absolute zero and used a Kerplunk!-style array of lasers to document the reaction as it happened.

Taking molecules to extremely low temperatures can be called ultracold chemistry, and it not only slows the particles down, but allows them to be manipulated in ways they cant be at higher temperatures. The molecules are essentially in a hypothermic coma that reduces their movement to the lowest possible speed.

One of the ways solid materials mislead us is by suggesting the particles in them arent active, but solidity and liquidity are usually the result of chemical reactions themselves. Within an ice cube, molecules move less than they do in liquid water and steam, but they still move very fast compared with what the Harvard lab calls the quantum crawl of near-zero Kelvin.

Ni has used ultracold chemistry to do a de facto Crispr drawer on molecules, combining impossible pairs that are so cold that they lack the normal resistance to bonding. This led to interesting work by itself, but the scientists in Nis lab realized they were seeing something else amazing: Instead of a before and after, where molecules were separate and then together, they were seeing what happened in the middle for the first time ever.

That new understanding will inform future research into how molecules combine and split. Both the observation of splitting and the molecule manipulation are made possible by ultracold chemistry, which slows a chemical reaction from a trillionth of a second to a huge, leisurely millionth or more.

Its amazing that scientists were observing anything within that trillionth of a second to begin with, which they did using powerful and extremely fast lasers. With microsecondsmicro is metric for a millionththe same level of laser power can document a hugely increased amount of data about the reaction. One microsecond is a million times longer than the chemical-bonds phase of a naturally occurring chemical reaction. Imagine if you sneezed in a very cold room and your half-second sneeze extended to 139 hours.

Nis research team is excited to see what else its near-absolute-zero facility will help reveal. The ability to slow reaction observation time by a factor of a million offers tantalizing possibilities in every field of science, but perhaps most of all in quantum physics, where the measured impression has always been that a few things are somehow happening simultaneously.

Is that truly the case, or is there billionth-of-a-second microthread processing that just appears smooth and simultaneous? If we slow particles enough, can we identify why observing them changes their outcomes or even stop that from happening? And what will having this power mean for changing isotopes, making new molecules, and more? The possibilities are limitless. Nis team published its paper in Science, and lead author Ming-Guang Hu summed it up nicely: Without this technique, without this paper, we cannot even think about this.

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The Coldest Chemical Reaction in the Known Universe Just Happened - Popular Mechanics