This is a classic air pressure test.

The device with the highest technical content is probably this glass cup. It was entrusted by Xia Fan to lightly and deliberately burn it with dragon scales. Although it appears deep green due to the impurities of sea sand, it does not hinder its excellent light transmittance.

Put four candles into a basin filled with water, then light the candles and press them upside down on the glass.

In full view of everyone, the candle quickly runs out of oxygen and goes out.

The water inside the cup then rises rapidly at a speed visible to the naked eye.

In less than a few breaths, the water pouring into the cup passed the basin outside and rose to almost one-third of the wall of the cup. From a distance, it looked like a new "small hill" rose from the basin.

Before that, the water surface inside and outside was still on the same level!

"How did this water move?"

"It feels like I've been sucked by something!"

The children's interest was immediately mobilized.

"Everyone might as well think about why this phenomenon occurs." Xia Fan looked at everyone again. In fact, he arranged a entrusted by the Privy Council among the audience to prevent the cold situation caused by no response.

But this time someone gave the answer in advance.

"Are you trying to say that because the gas in the bottle is exhausted, the gas outside squeezes the water surface and pushes the water into the bottle?"

"Correct." Xia Fan looked in the sound with a little curiousness. What caught his eye was a little girl. Judging from her location, it should be the guest invited by Fang Xiandao.

To be honest, this experiment is of course classic, but it is not as shocking as the hemisphere experiment in terms of perception. It takes a circle to understand the principle. The other party seems to be young, but he can quickly think of this level. Is she also a living dead person?

"Then can I ask a few more questions?" Qianyan stood up from the chair, which made her suddenly fade away again, "People in front, please let me go."

Maybe I have never seen such a powerful little girl, and everyone couldn't help but empty a passage.

"Master Qianyan..." Fang Yanni's face turned pale.

"Don't worry." Fang Xiandao spoke and comforted, "The Xia Fan I know is not the kind of person who bullies others by virtue."

On the other side, Xia Fan nodded with interest, "Of course, you said."

"Since the air is under pressure, why can't we feel tired? Even if we relax, we won't be crushed?"

"The same principle as this bottle, because there is air in our body, which is counteracted inside and outside. If the air is drained, the weight will be enough to cover a person."

"What exactly is air? Does it have a physical body? Can it be touched directly?" Qian Yan asked.

If it is the theory of reality and reality in the past, it will definitely avoid answering such questions positively and instead talk about mysterious principles.

"Of course it has." However, Xia Fan did not forcefully change the topic. "You can understand gas as a thinner water, so when the temperature is low enough, it will freeze like water and become a 'ice lump' visible to the naked eye. I think at that time, maybe you can see more intuitively that you are touching an entity."

"Can the air be frozen?" Qianyan couldn't help but be stunned. She absolutely did not expect that she would get such an answer, "How low is the temperature?"

"It's much lower than the freezing point. This temperature may be difficult to achieve at present, but as long as you work in this direction, I think you should have a day-to-day frost stimulation that condenses the water vapor floating in the air into ice?"

Qianyan showed a meditative look, and after a long time she raised her head, "These are just your speculations, right?"

Xia Fan did not deny it.

She hesitated, "That is to say... it is still doubtful whether the conclusion is correct."

"I know it is really unimaginable. It is also a great pleasure in investigating things: deduce the principles behind things from the details that are visible everywhere and apply them to a wider range of fields, even if it is counterintuitive." Xia Fan turned to the students who were enthusiastic, "Everyone is quiet! I have also prepared another experiment, which will allow you to see that not only the air fills the surroundings like water, but people can also do incredible things with it!"

This experiment is no longer limited to the square inch of glass bottles, but uses heaven and earth as the stage.

A simple air pressure fun experiment could certainly not satisfy Xia Fan. He tried to make this open class the first shot to make the school famous, so he did not hold back at all.

To show the charm of air, what else can be more influential than a representative machinery that combines various aerodynamic studies and represents the conquest of the sky by human beings?

At his gesture, the two guards walked into the school with a biplane.

Although its size can only be said to be model-level, it instantly attracted everyone's attention with its unique shape. At first glance, it looks a bit like a kite, but everyone quickly discovered that it is far thicker than a kite, with a size of nearly half a person, and its wings are even more than an arm. When placed on the ground, the thing does not move at all, and its weight can be seen.

Next, we use smooth wooden boards to build a runway about 100 meters long.

Xia Fan originally thought that the key electric motor of the biplane model was difficult to polish by hand, but Mo Yun gave him a surprise. The slender iron rod as a rotor was shaped by the latter with precision hands. In contrast, the copper wire and magnet surrounding the rotor were all accumulated in the four-wheel drive era and did not take much time.

The two groups of earth-based capacitor sheets provide energy for the engine. They are made of layers of gold foil and painted paper. In order to prevent the insulation from being penetrated, the surface of these painted papers is also applied with sealing wax to ensure that the charge does not fly up and down.

The one who charges the capacitor is a streamer. Even with thousands of earthquakes, Xia Fan burned several trial products before he mastered the intensity of charging the local capacitor.

Of course, he can also hold the wires in his hand and directly provide energy for the model machine, but this "wired remote control" is easily reminiscent of kites, which inevitably leads to a little bit of free feeling of wind chasing.

"What is this?" Qianyan couldn't help asking.

"The vehicle that can make people soar in the air, but it is now just a model."

"Soar... in the air? You mean, can it fly?"

This sentence is also a question for everyone, after all, the model machine looks too heavy and clumsy.

"Precisely because the air flows like water, as long as it is used properly, it can hold up things that are thousands of times heavier than itself, just like a ship that is heavy to a thousand pounds can only float on the sea." Xia Fan replied with a smile. Seeing that everything was ready, he turned off the switch connecting the circuit.

The blades located at the nose of the machine rotate rapidly and make a huge buzzing sound!

The motor does not need power, and as long as there is electricity supply, it will operate with maximum distortion.

Driven by the propeller, the biplane began to move forward slowly and faster and faster. Until the pressure difference obtained by the upper and lower wings exceeded the weight of the aircraft, it seemed to be lifted up by an invisible hand, and suddenly left the ground with the incredible eyes of more than two hundred people, roaring into the air!

The scene was silent for a while.

Xia Fan knew that the two sets of capacitors could only operate for a few dozen seconds, and then it would fall to the ground under gravity. But just these few dozen seconds was enough to leave an indelible impression in people's hearts.
Chapter completed!