Even in the US, science is mostly metric. But most US people are not exactly the scientific kind…
Modern science is, but there’s plenty of old journals from the 80s and earlier that use degrees Rankine and gallons.
Fucking BTUs and shit.
PSI is another one that seems to be used over the metric/SI alternative in some science-adjacent applications.
Psi is used a lot in engineering. But honestly, pressure units are a bit of a mess. The metric unit is a Pascal, which is fundamentally defined as a Newton per square meter – unsurprisingly, that is an incredibly small quantity of pressure. It’s roughly 101,500 Pascals for standard atmospheric pressure. You’ll typically see pressure written in either kPa, MPa, or bars (1E5 Pascals) within a metric framework. For perspective, it’s 14.7 psi (lbs per square inch) for an atmosphere.
And personally, I think all of these are pretty silly when we could be using 1 atm instead, which is literally defined as standard atmospheric pressure. It’s a much easier way to visualize and intuitively grasp pressures.
BTU is another fun one. It’s the energy needed to raise 1 lb of water by 1 degF. Calorie is the energy to raise 1 g of water by 1 degC. Both are very pragmatic definitions and have a degree of intuition. Then they’re the metric unit, the Joule, which suffers from the same issue as Pascal. It’s the work done by a 1 Newton force pushing an object 1 meter. Once again, pretty small.
Until you start looking at old stuff and have you figure out if they were working with the “millions scheme” or “thousands scheme,” and if “1 billion” is equal to 1012 or 109
