Debenedetti and Steinhardt don't work in the same building at Princeton, but they know of each other because their daughters share the same piano teacher. At my request, the two exchanged a few e-mails and concluded that each man's negative pressure was a stranger to the other. I also approached cosmologist Michael Turner at the University of Chicago, who conferred with his friend Humphrey Maris, a physicist and fluid-dynamics expert at Brown University.
After talking to Maris, Turner helped put the two realms together. The two kinds of negative pressure are related, though, "in the sense that they are examples of things that behave elastically. And both are a bit counterintuitive. If there is a unifying theme here, Turner said, it's direction—an inward, imploding, or contracting force, rather than the outward-pushing force typically defined as pressure.
The minus sign next to those atmospheres doesn't mean "less than nothing"; it's an arbitrary signifier denoting "in the direction opposite of positive. Liquids can have negative pressure in metastable states, when they resist turning to vapor. And, according to the astrophysicists, even empty space can have negative pressure. Gases are still the dark horse in the meta-stable. Steinhardt has heard that metastable gases can have negative pressure, but he isn't sure how.
Debenedetti is skeptical. Turner is noncommittal. Since the many facets of negative pressure are obscure enough to escape career physicists, I figure readers can be forgiven their confusion.
Negative pressure, it seems, is the perfect remedy for overstretched intellects. Register or Log In. The Magazine Shop. Login Register Stay Curious Subscribe. The Sciences. Newsletter Sign up for our email newsletter for the latest science news. Sign Up. Already a subscriber? Want more? Ask a Question. Formatting: Spelling, grammar or punctuation errors. Personal Attack: Disrespectful content about a person. Insincere Question: Question not seeking real answers.
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Active Oldest Votes. Improve this answer. Community Bot 1. You take in account signs of projections"? Thanks for link. Add a comment. So the temperature will have a negative value if 1 The derivative of entropy over volume change is negative, or 2 The absolute temperature is negative As for the 1 , i don't know if it's sign can become negative an increase in volume meaning a decrease in entropy or the opposite.
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