Atmospheric pressure. Torricelli’s experiment and Pascal’s Principle.
The online atmospheric pressure measurement simulations on this page will allow us to better understand what atmospheric pressure is, how we observe it and how we measure it. We will see what Torricelli’s experiment was about, which laid the foundation for modern atmospheric pressure measuring instruments. We will also learn what Pascal’s Principle is.
This Thematic Unit is part of our Earth Sciences collection
STEM OnLine mini dictionary
Altitude
Vertical distance of a point relative to sea level (m); it is the main factor determining pressure variation.
Atmospheric Pressure
Force exerted by air on the Earth’s surface; its common units of measurement are the millibar (mbar), millimeter of mercury (mmHg), pascal (Pa), or atmosphere (atm).
Barometer
Instrument used to measure atmospheric pressure, essential for predicting changes in the weather.
Pascal’s Principle
Law stating that pressure exerted at any point in a fluid is transmitted with equal intensity in all directions.
Standard Atmosphere
Reference model establishing the mean pressure at sea level as 1013.25 hPa (1 atm) at a temperature of 15 °C.
Torricelli’s Experiment
Scientific test that proved air has weight and can support a 760 mm mercury column at sea level.
Torricellian Vacuum
Airless space created at the top of a mercury tube when performing Torricelli’s experiment; it was the first evidence of a man-made vacuum.
What is atmospheric pressure
Atmospheric pressure is the force per unit area exerted by the air that forms the atmosphere on the earth’s surface. It is a fundamental phenomenon in the atmosphere and plays a crucial role in various aspects of our daily lives and natural processes.
Atmospheric pressure measurement unit
The IS unit of pressure is the pascal (Pa), named after Blaise Pascal. One pascal is equal to a force of one newton per square meter (N/m²). Other units of measurement are the bar (bar, equivalent to 100,000 Pa), the millimeter of mercury (mmHg), which is based on the experiment performed by Evangelista Torricelli in the 17th century, or the atmosphere (equivalent to 760 mmHg or 1.013 bar).
Variation of atmospheric pressure with altitude
Atmospheric pressure varies with altitude, since the amount of air over a given area decreases as we move away from the earth’s surface. The higher the altitude, the lower the atmospheric pressure. Atmospheric pressure also influences climate and the formation of weather systems. Changes in atmospheric pressure can indicate the arrival of cold or warm fronts, and areas of high and low pressure are responsible for wind patterns and atmospheric currents.
Atmospheric pressure measuring instruments
Barometers are instruments used to measure atmospheric pressure. There are different types, such as the mercury barometer and the aneroid barometer. In addition, weather stations and satellites also collect atmospheric pressure data for weather analysis and prediction.
STEM OnLine mini dictionary
Altitude
Vertical distance of a point relative to sea level (m); it is the main factor determining pressure variation.
Atmospheric Pressure
Force exerted by air on the Earth’s surface; its common units of measurement are the millibar (mbar), millimeter of mercury (mmHg), pascal (Pa), or atmosphere (atm).
Barometer
Instrument used to measure atmospheric pressure, essential for predicting changes in the weather.
Pascal’s Principle
Law stating that pressure exerted at any point in a fluid is transmitted with equal intensity in all directions.
Standard Atmosphere
Reference model establishing the mean pressure at sea level as 1013.25 hPa (1 atm) at a temperature of 15 °C.
Torricelli’s Experiment
Scientific test that proved air has weight and can support a 760 mm mercury column at sea level.
Torricellian Vacuum
Airless space created at the top of a mercury tube when performing Torricelli’s experiment; it was the first evidence of a man-made vacuum.
Explore the exciting STEM world with our free, online, simulations and accompanying companion courses! With them you’ll be able to experience and learn hands-on. Take this opportunity to immerse yourself in virtual experiences while advancing your education – awaken your scientific curiosity and discover all that the STEM world has to offer!
Atmospheric pressure measurement simulations
Torricelli’s experiment
Torricelli’s experiment, performed in 1643, proved the existence of atmospheric pressure. Torricelli filled a glass tube about one meter high with mercury, sealed it and inverted it in a vessel also containing mercury. He observed that the mercury in the tube descended, leaving an empty space at the top, and stabilized at a height of about 76 cm. This phenomenon occurred because the atmospheric pressure pushed the mercury in the vessel upward, balancing the column of mercury in the tube. This experiment led to the invention of the first instrument for measuring atmospheric pressure, the mercury barometer.
Drag the mercury tube into the vessel and see what happens to its level depending on the atmospheric pressure of the planet.
Pascal’s principle
Pascal’s Principle states that a change in pressure applied to an incompressible fluid at equilibrium within a closed vessel is transmitted uniformly in all directions and to all points in the fluid. Pascal’s Principle has a multitude of practical applications in all kinds of hydraulic devices such as presses, brakes, elevators, etc.
In the last of our online atmospheric pressure measurement simulations, you can see how the equilibrium point varies in two connected columns of fluid when the radii of the tubes change.
Giants of science
“If I have seen further, it is by standing on the shoulders of giants”
Isaac Newton
Evangelista Torricelli
–
Luke Howard
–
Become a giant
Modeling Climate Change
Introduction to Water and Climate
Global Warming Science
Climate Change: The Science and Global Impact
Our Global Ocean – An Introduction Course
Sensing Planet Earth – Water and Ice
The History of Ancient Environments, Climate, and Life
Introduction to Deep Earth Science
Professional development for Educators
What Works in Education: Evidence-Based Education Policies
Teach teens computing: Data representation
Teaching with Physical Computing: Assessment of Project-Based Learning
Teach teens computing: Databases and SQL
Giants of science
“If I have seen further, it is by standing on the shoulders of giants”
Isaac Newton
Alexander von Humboldt
–
Vilhelm Friman Koren Bjerknes
–
Become a giant
Modeling Climate Change
Introduction to Water and Climate
Global Warming Science
Climate Change: The Science and Global Impact
Introduction to Deep Earth Science
Sensing Planet Earth – Water and Ice
Sensing Planet Earth – From Core to Outer Space
Our Global Ocean – An Introduction Course
Professional development for Educators
Teach computing: Moving from Scratch to Python
Introduction to Online Education & Course Planning
Teach teens computing: Developing your programming pedagogy
HP Digital Skills for Educators – Google Workspace
Test your knowledge
What is atmospheric pressure, and how is it explained from a physical perspective?
How do Torricelli’s experiment and Pascal’s principle explain pressure behavior in fluids?
Why does atmospheric pressure decrease as you go up a mountain?
What did Torricelli’s experiment show?
Why is it useful to measure atmospheric pressure?
You may also be interested
2026 Best Online STEM Education Platform
Last simulations
To learn and experience
Take your knowledge to the next level with science kits and hands-on tools that connect theory with experimentation
Communicating vessels
Teachers essentials
Notion
Organize your notes, tasks, and projects in one place. Notion combines notes, lists, and calendars in one flexible space.
Canva
Design presentations, diagrams, and infographics with easy-to-use templates and professional results
Genially
Create interactive content, presentations, and educational games in a simple and visual way
Desmos
The most intuitive graphing calculator to explore mathematics and create dynamic classroom activities
Tinkercad
Design in 3D and simulate electronic circuits for free; it’s the perfect tool for simple robotics projects
Your Infinite Library
Enjoy the freedom to explore millions of titles and a curated selection of magazines on any device
Join Prime for students and young adults
The best series. Millions of songs. All included with your subscription.
Science made fun
Learn with the best courses
edX
Online courses from leading universities and companies. Learn practical skills and earn professional certifications
Coursera
Courses from leading universities and companies. Learn practical skills and earn professional certifications
Udemy
Thousands of online courses tailored to your level. Learn at your own pace with expert instructors