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Torricelli and most of his contemporaries (and possibly guest author Richard Williams as well) might have thought that the famous experiment demonstrated the existence of a vacuum. That is incorrect. Namely, the empty-looking closed space above the liquid mercury in the barometer is occupied by mercury vapor at the equilibrium vapor pressure of liquid mercury, which corresponds to the temperature at which the experiment is carried out. Although the equilibrium vapor pressure of mercury is small (1 Pa at 315 K), it is not zero. Nowadays we know that all condensed phases have equilibrium vapor pressure. Consequently, we cannot create and maintain a vacuum on a macroscopic scale. Unfortunately, numerous textbooks perpetuate the incorrect notion that the empty-looking space in closed-end barometers (using mercury or any other liquid) is a “vacuum.” Thus in retrospect, besides its great historic significance, Torricelli’s elegant experiment had actually demonstrated the existence of an equilibrium vapor pressure of mercury, rather than the existence of a vacuum.
Zoltan A. Schelly
In response to the Back Page “Why Communicate Science?” by Carl Safina, that appeared in the October APS News: as far as I know, most people could not name the leading lawyers, the line of succession to the Presidency, leaders in Congress, the leading physicians, etc. In general, people know “the celebrities”–those people paraded daily by the media–and some don’t even know those.
No other profession has people like Einstein, Darwin, and Newton that people generally know were “important.” So it is untrue that science is unknown or unrecognized. The problem is that people have the same regard for scientists that they once had for clergy, which is appropriate because academic degrees began as “holy orders” for members of the clergy back in the day when all scientists were clergy. That regard is dramatized by the reason the Pope silenced Galileo. It wasn’t a theological problem. It was a public perception problem. The public wasn’t interested in theology, but it saw clergy as magicians who had “the remote control to the universe” and when it heard clergy debating whether the sun circled the Earth or vice versa, it thought they were contemplating making the Earth circle the sun and they rioted in fear. Nowadays, people have discarded theologians, ordinary clergy, lawyers, and politicians. They have focused upon scientists, who are believed to have the remote control to the universe. They do not like us. They are scared witless by us. But they will tolerate us as long as we give them iPods, iPads, remote controls, and pills to fix stuff so they do not have to “eat right and exercise.” This is not so different from not having “to pray and behave,” which was what the clergy required.
I agree that we should make an effort to do something about this perception. However, many of us are, shall we say, not socially adept and thus not fitted for the task. Perhaps instead of focusing on how science provides more stuff, we should focus on the fact that, unlike theology, science changes when the next piece of this infinite puzzle is placed. Also, science does not pretend to tell anyone who they are or why they are, just how, physically they came to be. By emphasizing the discipline and limitations, we might not get more funding, but the “other guys” might let us into “their group” and stop treating us like wacky magicians who must be tolerated. Rushing around pontificating on this or that controversy (about which we only know the physics and do NOT know about the millions who could be fired, displaced, or otherwise abused) is not likely to help the cause of “science.” Science should be treated more like carpentry–something we can do to be useful and helpful in return for farmers feeding us, manufacturers clothing us, and construction workers housing us.
J. W. Lane
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