Therefore, the interior of the air is subjected to pressure in all directions. and this pressure is called Atmospheric pressure. In the year 1643, Italian scientists A thin and 80 cm long glass bulb was filled with mercury. and placed upside down in a water tank containing mercury. He found that the mercury in the glass bulb had dropped about 4 centimeters and then stopped. Because no air enters this 4 space, because it is a vacuum.
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