This is a classic barometric test.

The most technical device is probably this glass. It was also specially fired with dragon scales by Xia Fan's entrustment Luo, although it showed a deep green color due to the impurities of sea sand, it did not hinder its excellent light transmittance.

Place four candles in a basin filled with water, then light the candles and close the glass upside down.

In full view, the candle quickly ran out of oxygen and went out.

Then the surface of the water inside the cup rises rapidly at a speed visible to the naked eye.

In less than a few breaths, the water pouring into the cup crossed the basin outside, rising almost to a third of the wall of the cup, and from a distance, it looked like a new "hill" had risen from the basin.

And until then, the inner and outer waters were on the same level!

"This water...... How did it move?"

"It feels like something has been sucked up!"

The children's interest was immediately aroused.

Think about why this is happening. Xia Fan looked at the crowd again—in fact, he had arranged for the Privy Council among the observers, just to prevent the cold scene caused by no answer.

This time, though, someone said the answer in advance.

"Could it be that what you're trying to say is that because the gas inside the bottle is depleted, the gas from the outside squeezes the surface of the water and pushes the water into the bottle?"

"Correct. Xia Fan was a little curious and looked at the voice, and it was actually a little girl who caught his eyes. Judging by her location, she should be a guest invited by Fang Xiandao.

To be honest, this experiment is classic, but it is not as shocking as a hemispheric experiment, and you need to go around in a circle to understand the principle. The other party doesn't seem to be very old, but he can quickly think of this layer, is it - she is also a living dead?

"Then can I ask a few more questions?" Qianyan stood up from her chair, which made her suddenly a little shorter again, "The person in front, please let me go." ”

Probably never seen such an imposing little girl, everyone involuntarily vacated a passage.

"Lord Qianyan......" Fang Yanni's face turned white.

"Don't worry. Instead, Fang Xiandao opened his mouth and said comfortingly, "The Xia Fan I know is not the kind of person who bullies others. ”

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

"If there is pressure in the air, why don't we feel tired, even if we relax, we won't be deflated?"

"It's the same as this bottle, because we also have air in our body, and the inside and outside cancel it out. If you pull the qi out, it's enough weight to weigh on a person. ”

"What the hell is air, is it corporeal, can it be directly touched?" asked Qianyan.

If it is the theory of reality in the past, we will definitely avoid answering this kind of question head-on, and instead talk about some mystical and mysterious truths.

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

"The air—can it be frozen?" Qianyan couldn't help but be stunned, she categorically didn't expect that she would get such an answer, "How low is the temperature?"

"It's a lot lower than freezing. This temperature may not be achievable at the moment, but if you work in this direction, I think you should see a day when frost freezing is just condensing the water vapor floating in the air into ice?"

Qianyan gave a pensive look before she looked up after a long time, "These are just your speculations, right?"

Xia Fan did not deny it.

She hesitated, "That is...... Whether this conclusion is correct is questionable. ”

"I know it's really unimaginable. This is one of the great pleasures of Gewu: to deduce the principles behind things from the details that are usually everywhere and apply them to a wider range of fields, even if it is counterintuitive. Xia Fan turned to the enthusiastic students, "Everyone is quiet!, I have prepared another experiment, which will show you that not only does the air fill the surroundings like water, but people can also do incredible things with it!"

This experiment is no longer limited to the square inch of the glass bottle, but takes the world as the stage.

Of course, a simple fun experiment of air pressure could not satisfy Xia Fan, and he tried to make this open class the first shot of the school's reputation, so he did not spare the slightest.

And what could be more impressive than the iconic machinery that combines all sorts of aerodynamic studies and represents the conquest of the skies by man?

At his signal, two guards carried a biplane into the hall.

Despite its model-level size, it instantly caught everyone's attention with its unique shape – at first glance it looked a bit like a kite, but it soon became clear that it was much thicker than a kite, nearly half a man tall, and its wings were more than an arm's length. When placed on the ground, the thing does not move, and its weight is visible.

The next step is to build a 100-meter-long runway out of smooth wooden planks.

Xia Fan originally thought that the key to the biplane model - the electric motor was difficult to polish by hand, but Mo Yun gave him a surprise, the slender iron rod as a rotor, it was the latter that was sharpened and formed little by little by precision hands. In contrast, the copper wires and magnets that surround the rotor are just the experience accumulated from the 4WD era, and it doesn't take much effort.

Supplying energy to the engine are two sets of earth-based capacitor sheets. They are made up of layers of gold leaf stacked on top of each other, and to prevent the insulation from breaking down, the surface of the paper is also coated with sealing wax to ensure that the charge does not fly up and down.

Charging the capacitor is a heavy streamer. Even after thousands of earthquakes, Xia Fan burned several prototypes before he mastered the strength of charging the earth method capacitor.

Of course, he can also hold the wire in his hand and directly provide energy for the model machine, but this kind of "wired remote control" is easily reminiscent of a kite, and it inevitably lacks the feeling of being free to chase the wind.

"What is this?" Qianyan couldn't help but ask.

"A vehicle that allows people to soar through the air, but it's just a model now. ”

"Soaring...... In the air? You mean, it can fly?"

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

"Because the air flows like water, it can lift a thousand times heavier than oneself if it is used properly, just as a ship weighing a thousand pounds can only float on the sea. Xia Fan replied with a smile. Seeing that everything was ready, he flipped the switch that connected the circuit.

The propellers located in the nose of the aircraft spun up at a rapid speed and made a loud buzzing sound!

The motor does not need a boost, it will run at maximum twist as long as there is a supply of electrical energy.

Driven by the propellers, the biplane began to move slowly and faster. Until the pressure difference between the upper and lower wings exceeded the weight of the plane, it seemed to be held up by a pair of invisible hands, and suddenly left the ground under the incredulous gaze of more than 200 people, roaring into the air!

The scene was silent for a while.

Xia Fan knew that the two sets of capacitors could only run for dozens of seconds, and then it would fall to the ground under the pull of gravity. But just these tens of seconds are enough to leave an indelible impression in people's hearts.