“Evangelista Torricelli: Unveiling the Genius Behind Atmospheric Pressure”
Physicist and mathematician Torticelli was born on October 15, 1608, in a city called Faiza in northern Italy. He was so successful at the Jesuit College of Faiza that his priest uncle sent him to Rome to master various branches of science under the tutelage of Benedetti Castelli. Castelli himself was a disciple of Galileo and professor of mathematics at the College of Sapienza. Castelli sent Torticelli’s first essay ‘On Projectiles’ to Galileo. Galileo was greatly impressed by the young man’s mathematical talent and critical thinking, but Torricelli could come in personal contact with Galileo only much later – in 1641 AD, three months before Galileo’s death, when that great master of science He had become blind. In these three months, he was the teacher’s assistant as well as the blind’s stick. It was Galileo who first inspired Taricelli that there should be some solution to the problem of ‘zero’. The pump builders at the Grand Duke of Tuscany tried and failed, but could not lift the water 40 feet: the water could not be raised more than 32 feet by suction pumps. Galileo put a question before Torticelli that he should find some reason and solution for this.
Two years later, Torticelli, now professor of mathematics at the Florentine Academy and personal mathematician to the Grand Duke, performed the test, which is now famous. Even more important than this test was why this happens. He also explained the reason for this.
Fortunately the art and craft of making glass objects was at a great advance in those days in Rome. Torricelli did not face any problem in getting four feet long tubes made. One end of these tubes was closed. Torticelli filled the tube up to its mouth with mercury, closed the mouth with his finger, and inverted the tube into a cup—the cup itself was full of mercury. Now he removed his finger, and lo, the mercury came out and came into the cup – not all, but some. The mercury in the upper end of the tube remained only about 30 inches above the surface of the cup. The space above that was ’empty’. Torticelli skewed the tube. Mercury filled the tube further, but its height was still 30
It was only inches! The tube was further skewed. And now also of mercury. The height remained less than 30 inches from the mercury lying in the cup and the tube was completely filled. Straighten the tube a little then the same ‘zero’ comes back again! In this empty space, we know, only some vapors of mercury remained, but – in fact now it was ‘void’.
But there was still one question left that had not yet been resolved: how did Mercury stand on its own at such a height? Why didn’t the whole of it flow into the cup? Torricelli had an answer for that too. “The atmosphere in which we live,” Torricelli’s words, “is the bottom of a sea—an infinite sea of air. And air also has weight, it has been proved by experiments. There’s a huge mass of air 50 miles high above, which is always exerting pressure on us. So it’s no surprise that this liquid starts to climb up in the tube, because there’s nothing to hinder its progress. , And goes on climbing, until it comes against the pressure of the outside air. It is the outside air that holds it up to such a height that it does not allow it to fall – this was the conclusion or implication of the test.
Now it was not difficult for Torricelli to explain why the water could not be raised above 32 feet by the suction pump. Our environment cannot tolerate this heavy load of water. Mercury can rise up to 30 inches and water up to 32 feet. The relative density of mercury is 13.6. Torricelli also realized that now we have a device in our hands to measure the density of air. But the name of this instrument – weight-measure or barometer – was given by Blaise Pascal, not Torricelli. And it is also a matter that if the density of the atmosphere is less – as it happens on the top of the mountain – the height of mercury will naturally be less at such a place. The weight of the wind at the top of Everest can handle only 11 inches of mercury in a barometer.
Barometer is used to predict the weather. Moist air weighs less than dry air. That is to say, the mercury in the barometer will come down when there is some moisture in the air, and moisture in the air means that it is likely to rain. This mercury will go up again when the air becomes dry again. To know the news of the weather, it is not enough to read the barometer only, but yes, the decrease in air pressure means
If tomorrow the weather will be bad, and if the mercury starts rising, then understand that the next day the sky will be clear.
Torricelli did some more tests on the basis of his new discovery regarding ‘zero’. He showed that light travels through vacuum with the same ease as through air. And it was this formula that gave Huygens a novel idea that “light is nothing but a set of waves.” Torricelli also conducted experiments regarding the power of sound and magnet. His research in mathematics and in the field of water power is no less important.
Tarricelli died in 1647, at the age of 39. But even at this young age, he did a lot. Whenever we read the barometer or listen to the news about the weather, we are, in a way, acknowledging Torricelli’s debt. And this infinite sea of air, it is the atmosphere which does not allow the water to fall out of the glass, it also pushes the inverted handkerchief to hold it!
Now just try this test yourself – but on a chirmichi or hodi. Fill three-quarters of a glass with water. Wrap a handkerchief, loosely, over the mouth of the glass. Tie the handkerchief from all sides with a thread, but the handkerchief should keep touching the water. And now just turn the glass upside down.
Aristotle once said, “Nature probably hates a void or an empty space.” And how many wonderful inventions we have made today, and how much our machinery has developed in every field, but there was definitely some truth in Aristotle’s statement: there is probably no such thing as ‘absolutely zero’. No matter how much you try to empty any space with gas etc., some or the other matter particles will remain in that empty space. But it was not these residual particles that caused Galileo’s headache when he raised a problem regarding pumps with one of his disciples (Evangelista Torticelli). Not exactly zero, but almost empty – the problem of emptiness could not be solved till then.