Ordinarily, you won’t encounter a radiation thermometer until somebody puts one in your ear at the doctor’s office, or you point one at your forehead when you’re feeling feverish. But more sophisticated and highly calibrated, research-grade “noncontact” thermometers—which measure the infrared (heat) radiation given off by objects without touching them—are critically important to many endeavors besides healthcare.

However, even high-end conventional radiation thermometers have produced readings with worryingly large uncertainties. But now researchers at the National Institute of Standards and Technology (NIST) have invented a portable, remarkably stable, standards-quality radiation thermometer about 60 cm (24 in.) long that is capable of measuring temperatures to a precision of within a few thousandths of a degree Celsius.

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