A barometer measures the air.
The air has weight. It pushes on us. This tool helps us see the weather. It can help us find a storm.
Can you feel the air push on you?
A barometer is a tool. It measures the air.
The air has weight. It pushes on everything. This push is called air pressure.
A man named Torricelli made a tool to see this. He used a heavy liquid called mercury. The weight of the air pushes the liquid up a tube. If the air pressure changes, the liquid moves. This helps us see the weather.
It can even help us find a storm. It is a very cool tool to watch.
A barometer is a tool used to measure air pressure. Air pressure is the weight of the air pushing on us.
This weight can change. These changes help us predict the weather.
In 1644, Evangelista Torricelli made a new kind of barometer. Before him, many thought air had no weight. Torricelli showed that air does have weight. He used a heavy liquid called mercury. He put mercury in a glass tube. The weight of the air pushes on the mercury in a basin. This push forces the mercury up into the tube.
When air pressure is high, it pushes harder. This makes the mercury rise higher in the tube. When pressure is low, the mercury level drops. This can signal a coming storm.
Scientists also found that air pressure changes with height. Blaise Pascal and Florin Perier tested this idea. They found that pressure is lower high up on a mountain. This happens because there is less air above you to push down.
A barometer is a special tool used to measure air pressure. Air pressure is the weight of the air pushing on everything on Earth.
Scientists use these readings to see how weather might change soon. If the pressure starts to drop, it might mean a storm is coming.
Barometers are very helpful for understanding the atmosphere around us. They help us find different weather systems and boundaries in the sky.
One way a mercury barometer works is by using a heavy liquid.
Imagine a glass tube that is closed at the top. The bottom sits in a basin filled with mercury. The air around us pushes down on the mercury in that basin. This push forces the mercury up into the tube.
When the air pressure is high, it pushes harder and the mercury rises. When the pressure is low, the mercury level drops lower in the tube.
Long ago, people did not think air had any weight at all.
In the early 1600s, scientists like Giovanni Battista Baliani did experiments with water. They noticed that water would only go up a certain height in a tube. Around 1643 or 1644, Evangelista Torricelli had a new idea. He realized the air was actually pushing the liquid up.
He used mercury because it is much heavier than water. This allowed him to use a much shorter tube for his tool.
Other scientists helped prove how these tools worked.
Blaise Pascal wanted to see if air pressure changed with height. In September 1648, Florin Perier carried a barometer up the Puy de Dôme mountain.
He found that the mercury stood lower at the top of the mountain. This happened because there was less air above him to push down. This proved that air pressure is lower at higher altitudes.
Today, we see the ideas of the barometer in many places. You might see a simple weather glass at home.
Some people call these Goethe barometers after a famous writer. Even modern tools like smartphones can use barometric sensors.
They help your phone know how high up you are. Whether it is a big machine or a tiny sensor, it all works by measuring the air.
A barometer is a scientific instrument used to measure atmospheric pressure. This is the weight of the air pressing down on the Earth's surface.
By tracking these readings, scientists can observe pressure tendency. This refers to how pressure changes over a short period. These changes help meteorologists forecast upcoming weather patterns. Barometers are essential for finding surface troughs and pressure systems. They also help identify frontal boundaries in the atmosphere.
One common type is the mercury barometer. This device consists of a vertical glass tube closed at the top. The bottom of this tube sits inside an open basin filled with mercury. The atmosphere exerts force on the mercury in the basin. This force pushes the liquid up into the tube. The mercury level adjusts until it balances the atmospheric force.
When air pressure is high, the mercury rises higher in the column. When pressure is low, the mercury level drops. Scientists must also adjust the scale for temperature. Higher temperatures reduce the density of the mercury.
A barometer is different from a pressure altimeter. Both instruments use atmospheric pressure, but they serve different goals. A barometer stays at a constant altitude to measure weather changes. An altimeter measures the pressure of the surrounding atmosphere to estimate altitude. It compares the current pressure to expected levels at various heights. This allows pilots and hikers to determine how high they are.
Before the 1600s, many people believed air had no weight.
In 1630, Giovanni Battista Baliani observed a siphon experiment. He found that water could only rise to about 10 meters. Galileo Galilei suggested that a vacuum held the water up. He believed nature resisted the creation of a vacuum. Later, Gasparo Berti and Raffaello Magiotti conducted experiments with tubes. They observed that water stayed at a specific height in a tube. This suggested a vacuum might exist in the space above the water.
Evangelista Torricelli is credited with inventing the barometer around 1643 or 1644.
He proposed a revolutionary idea about the weight of the air. He argued that the atmosphere pushes on the water in a basin. This weight holds up the column of liquid in the tube. To make his tool more practical, he used mercury. Mercury is about 14 times denser than water. This meant he only needed an 80 cm tube instead of a 10.5 m tube. He demonstrated that air pressure could support 30 inches of mercury.
Other scientists worked to prove these mechanical theories. Blaise Pascal wanted to test if air pressure changed with altitude.
He asked Florin Perier to take a barometer up the Puy de Dôme mountain. In September 1648, Perier performed this experiment. He found that the mercury column stood lower at the top of the mountain. This proved that air pressure decreases as altitude increases. There is less air above the observer to provide weight.
There are many variations of barometers used today. One simple version is the "weather glass" or Goethe barometer.
It uses a sealed glass container that is half-filled with water. A narrow spout connects the body to the atmosphere. If air pressure drops, the water rises in the spout. If pressure increases, the water level drops. Modern technology also uses barometric sensors. You can find these in devices like smartphones. These sensors help gadgets calculate altitude and track weather.
Where will your curiosity go next?
🖼️ Images & Media (22)
+ 10 more
More to explore
✨ What else?
Related topics you might enjoy
🔬 Go deeper
More advanced topics to explore
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.