At the same time, on Plymouth Hoe, twice that number of the world's astrologers will also have gathered; they will engage in mystic circle-dancing as darkness covers the earth.
Both the Royal Astronomical Society and the Astrological Association have re-arranged their annual meetings to take place this week to coincide with the eclipse, but they are looking at the same phenomenon through rather different eyes.
The astronomers will hear lectures on a new infra-red telescope cooled by helium, on black holes, and with titles such as "helio-seismic images of the interior of the sun". The astrologers, in contrast, have booked speakers on The Prophecies of Nostradamus, Wise Woman's Ways to Astrological Healing, and Horary - which is foretelling the future.
"The eclipse significantly affects the birth charts and lives of many thousands of people," said Roy Gillett, chairman of the astrologers, who, barring the unforeseen - and presumably he knows about that - will be elected their president at the meeting. It has certainly affected the astrologers. "Six hundred people have signed up for this meeting; normally we get only half that."
Their meeting will discuss much more than whether you are born under Leo or Scorpio; astrologers believe the hour and minute of your birth link your life mystically to the planetary arrangements in the sky - and especially to eclipses.
"Many religions believe that devotions are especially effective when performed at new and full moons. They become 10 or even 100 times more important when there is an eclipse,'' explained Mr Gillett.
"The astrological energy of this eclipse coincides with significant alignment of the major planets," he continued. "It means turbulent times. We shall see more disruptive events like Kosovo, political cover-ups emerging into light, confrontations over things like GM foods. It will take six months to work its way out in human affairs."
The hard-headed astronomers, of course, believe no such thing. Unlike the astrologers, their meeting place, in Guernsey, is not under the path of the solar eclipse, so they will be taking a break on Wednesday for a day trip to the neighbouring island of Alderney, which is.
"We thought," said their spokeswoman Dr Jacqueline Mitton, "that it would be nice to arrange things so their university travel budgets to the conference would allow them to see the eclipse as well."