Scenario takes the present acceleration of the expansion of the universe to extremes. In the wake of observations of distant supernovae (see the article by Saul Perlmutter in Physics Today, April 2003, page 53), cosmologists generally apportion 70% of the universe’s energy inventory to an enigmatic dark energy. The new relevant parameter, which must be less than —1/3, is w, the ratio of the dark energy’s average pressure to its energy density. The widely known cosmological-constant and quintessence models explore values of w between —1/3 and —1. But what if w is less than —1? In that “phantom energy” case, Dartmouth College physicist Robert Caldwell with Marc Kamionkowski and Nevin Weinberg of Caltech have now determined that eventually all bound objects—galaxies, stars, planets, atoms, nuclei, and nucleons—will be torn apart. Caldwell suggests that deciding between their model and the others might be possible in coming years with much better measurements of the microwave background, supernovae, and galaxies. (R. R. Caldwell et al., Phys. Rev. Lett. 91, 071301, 2003http://dx.doi.org/10.1103/PhysRevLett.91.071301.)
As scientists scramble to land on their feet, the observatory’s mission remains to conduct science and public outreach.
November 18, 2025 12:49 PM
This Content Appeared In
Volume 56, Number 10
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Physics Today - The Week in Physics
The Week in Physics" is likely a reference to the regular updates or summaries of new physics research, such as those found in publications like Physics Today from AIP Publishing or on news aggregators like Phys.org.