Blaise Pascal

Who Carried A Barometer Up A Mountain · Mathematician & Writer · 1623–1662

Who settled whether nature abhors a vacuum by sending a barometer up a mountain — and showed that a fluid transmits a pressure equally in every direction, so that a few cupfuls of water in a thin pipe can burst a barrel.

Who was Pascal?

Blaise Pascal was born at Clermont in 1623 and educated entirely by his father, a tax official; at nineteen he built a mechanical calculator to do his father's arithmetic. Torricelli had inverted a tube of mercury in a dish and left an apparently empty space at the top, and the schools insisted the space could not be empty because nature abhors a vacuum. Pascal held that the mercury is held up by the weight of the air pressing on the dish, and devised the experiment that must decide between the two accounts: carry the barometer up a mountain, where there is less air overhead, and the column must fall. In September 1648 his brother-in-law Florin Périer carried one up the Puy-de-Dôme, some fourteen hundred yards above Clermont, and the mercury fell by more than three inches and rose again on the descent, while a second barometer left at the foot under the eye of a monk did not move all day. Pascal went on to establish that a fluid at rest presses equally in all directions and transmits an applied pressure undiminished throughout, so that a small force on a small piston balances a great weight on a large one — the principle of every hydraulic press since. He showed too that the pressure depends only on the depth and not on the shape or quantity of the vessel, demonstrating it by bursting a strong barrel with a few cupfuls of water poured into a long thin pipe fixed in its lid. With Fermat he founded the calculus of probabilities. After a religious experience in 1654 he turned to Jansenism and to the Provincial Letters and the Pensées, and thought his mathematics largely vanity. He died at thirty-nine.

Major achievements

• Devised and had performed the Puy-de-Dôme experiment, proving the air has weight
• Established that a fluid transmits pressure equally and undiminished in all directions
• Showed that pressure in a liquid depends on depth, not on the shape or amount of the vessel
• Burst a barrel with a few cupfuls of water in a tall thin pipe to demonstrate it
• Built a working mechanical calculator at nineteen

Life in brief

• 1623 — Born at Clermont: Educated entirely by his father.
• 1642 — The calculating machine: Built at nineteen for his father's tax office.
• 1647 — New Experiments on the Vacuum: The argument with the Jesuits begins.
• 1648 — The Puy-de-Dôme: Périer climbs; the mercury falls three inches.
• 1654 — Probability, and the night of fire: The letters with Fermat, then the turn to religion.
• 1656 — The Provincial Letters: French prose changed by a controversy.
• 1662 — Dies at Paris: At thirty-nine; the Pensées published after.

Explore the life of Pascal — five chapters

1. Educated Entirely by His Father — A calculating machine at nineteen
2. A Mountain Settles an Argument — The Puy-de-Dôme, 19 September 1648
3. Bursting a Barrel With a Few Cupfuls — Pressure transmitted equally in all directions
4. The Problem of the Points — A gambler's question, answered in letters with Fermat
5. The Night of Fire — Port-Royal, the Provincial Letters, and thirty-nine years

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