Reincarnation with AI (Unemployment-Free)

On a hill in the village, there grows the largest tree in the vicinity.

Rudeus and Sylphie were practicing magic in the shade of a tree.

"Simply put, just as fish swim in water, we also swim in the air," Rudius said.

"Air?" Hilfi asked, looking troubled.

Explaining the existence of air to people is not easy; this invisible thing is truly perplexing.

If you don't explain it clearly, people will just think you're talking about the wind, not the air.

This doesn't seem like common sense from a previous life. People naturally know that the earth is round, there is air around it, and wind is the movement of air.

To be honest, even modern people who think this way are just following the crowd because everyone around them thinks this way.

Because this is common sense, an axiom, and the foundation of their worldview.

You ask him why the Earth is round and why there is air.

It's round, it's there!

Are you stupid? Asking something like that?

The other party will be angry and will feel that you are challenging or subverting them.

Modern people are not smarter than ancient people; they just have a different mindset. They've been instilled with more advanced ideas and think they're smarter than ancient people.

"Yes, it's like putting your hand into a stream and feeling the water flowing. Wind is the movement of air."

Rudeus used magic to create a gentle breeze that ruffled Silphie's hair.

"Do you remember how to activate the fog?"

"Should we activate the Waterfall, Geothermal, and Ice Zones in that order?"

"Um."

Rudius raised his hand and heated the water balloon in his hand into steam.

"Look, the water is turning into a gaseous state. Now I'm heating it all at once, and you can't see the steam anymore, can you? This is simulating the waterfall and geothermal activity in front of us."

A large amount of magic surged out, but inevitably some white mist would still appear.

Rudeus gradually discovered the flaws of the magic of steam.

The first issue is the hidden problem.

When using steam magic, contact between steam and air is unavoidable. This means that steam magic cannot be made transparent when used alone and will be visible to enemies.

At that point, the slow-moving steam is no longer a hidden killer, no longer a trap in the enemy's path, but just a waste of magic.

No warrior would willingly walk into the white mist.

Although it doesn't have much effect when added to mist or flames, it can't be used alone, which makes it somewhat useless.

This makes steam magic more of an add-on than a means to gain the upper hand.

That drastically reduces the usability of Rudius, who uses information asymmetry as his starting point.

If Rudeus were to explain this to Sylphie now, he could provide a large amount of magic power to make the steam as transparent as possible, making it look like a distorted mass of air, but this would obviously not be useful in battle.

Teaching and fighting are two different things.

Secondly, steam can easily injure oneself. Even though Rudeus has learned to control the amount of steam produced and knows how much water can produce approximately how much steam, as mentioned earlier, gas, like water, can easily backfire once it is spilled and disturbed by the airflow during combat.

The steam will penetrate the clothing directly, clinging to the body like a bone-deep infection, undergoing a phase change and liquefying, and releasing a large amount of heat.

This is not a good thing for the enemy, nor is it a good thing for Rudius.

This type of adhesive burn is an extremely terrifying yet insidious killer, and it is also what makes steam truly terrifying.

In order to avoid burning himself, he imposed strict restrictions on the casting distance. If he was too far away, the steam would be uncontrollable, and if he was too close, he would accidentally hurt himself.

This makes steam magic even less useful.

The steam magic that was originally conceived to complement mist and fire rings, aside from the steam bomb that caused a significant increase in volume when water turned into steam, has hit a bottleneck ever since, unable to expand into other applications.

Back to teaching.

Rudius picked up a small twig and dipped it into the steam. The surface of the twig gradually carbonized in the steam.

Sylphie looked at the small patch of distorted air and asked, "Rudy, isn't that fire?"

How so?

That's right. To make the steam appear transparent, Rudius actually wrapped the water vapor in a large mass of hot air. Once the water vapor became transparent, it looked exactly like the distorted air above the flame.

"No, this is what water looks like when it turns into air, called water vapor. It does this because it's hot enough, like a flame, to distort the air."

"And what is that fog?"

Upon hearing Sylphie's question, Rudeus reduced the output of his magic, causing the water vapor to condense back into mist.

"Mist...mist is water, but because of the heating and cooling process, the clump of water was broken up into a large number of very small water droplets."

Seeing that Hilfi still didn't quite understand.

As he spoke, Rudeus condensed the water vapor in his hand into mist and gently pushed it toward Sylphie.

A small cloud of water vapor cooled down in a short distance.

Hilfi felt a layer of mist hitting her face, bringing a cool sensation.

Rudius extended his index finger and gently stroked it across Silphi's face, then rubbed it together with his thumb.

You can feel the humidity.

"Isn't it wet? Hilfi, look, it's still watery," Rudeus laughed.

"Mmm," Hilufi replied, her face flushed.

"But if we're talking about fish in water, then people in the air should also have buoyancy," Rudeus muttered to himself.

Rudeus used the analogy of fish in water to explain the existence of air to Sylphie, and now that I think about it, it makes a lot of sense.

Air also has mass, and it has water pressure and atmospheric pressure.

Aren't humans essentially living in the ocean beneath the air?

Then the problem arises.

Does buoyancy only exist in liquids?

Are they not found in solids and gases?

If you were buried in the ground, would you feel lighter?

If you stand in a vacuum, do you feel heavier?

This is an excellent question; it touches upon the core of the concept of buoyancy...

The fundamental reason for buoyancy is Archimedes' principle: an object immersed in a fluid (including liquids and gases) experiences an upward force equal to the weight of the fluid displaced by the object.

[...also present in gases: the most typical examples are hot air balloons and hydrogen/helium balloons...]

[...solid...vacuum...]

Wait a minute, what?

What did the AI ​​just say?

Hot air balloon? What Archimedes' principle?

Doesn't a hot air balloon rise because the hot air rises, thus lifting the balloon up?

Rudius remembers this question very clearly.

When I was a child in my past life, this was one of the few questions my dad could answer directly.

So he remembers it very clearly. Rudius could say he remembered this answer his whole life. Now you say it's wrong?

Isn't a hot air balloon lifted by the lift generated by hot air?

Why is it said that a large amount of air was displaced?

Let me explain the principle behind hot air balloons.

You've raised an excellent question, which is precisely the key to understanding the principle of buoyancy!

Archimedes' principle:

The buoyant force on an object in a fluid is equal to the weight of the fluid it displaces.

[...By heating the air at the bottom of the balloon, the air molecules inside the balloon move faster and the distance between them increases.]

This results in fewer air molecules within a given volume, therefore, the density of hot air is less than the density of cold air outside...

density……

Therefore, the principle of buoyancy in air is exactly the same as that in water!

Huh!? Holy crap, how come I didn't think of that?

"Rudy? What are you thinking about?" Hilfi asked.

"Hilfi, I suddenly thought of a magic spell! Maybe we can fly!" Rudeus exclaimed excitedly.

"Hmm? What kind of magic is it?"

"I was just saying fish swim in the water, right?"

"Hmm, but what does this have to do with flying?"

"If fish can swim in water, does that mean we can swim in the air too?"

Hilfi tilted her head, feeling like she understood a little, but not quite.

"So what should we do?"

"Let me think... I'll use wind magic to thin out the surrounding air and then confine it around my body," Rudeus said as he cast a spell without chanting.

Rudius felt the air being sucked out of his lungs.

"Ugh! Ugh~! My head can't get thinner." Rudeus gasped.

It seems that attention to detail is needed; you can't just wrap yourself up completely in thin air.

"Hmm... I'll thin it out, then maintain the magic, connecting the surrounding gas and my body as a single entity through magic, and then I'll float up..."

Rudius tried jumping, and sure enough, he felt lighter.

It felt like it was floating downwards when it fell.

"Hahaha, Silphie, look, haven't I slowed down a bit?" Rudeus asked excitedly.

"Huh? Really? It seems so." Hilfi said with a hint of doubt.

There's nothing we can do; it's normal for Rudius to have poor results at first, as he's just starting out.

Hilfi didn't see any obvious changes from the magic, but she could clearly feel her body being lifted by buoyancy, like walking out of water, and she could clearly feel the weight of her body. Rudeus already knew the feasibility of this method.

Flying, maybe we can fly!

Although the flight magic has only just begun, the important thing is that we have a clear idea.

At first, Rudeus held the idea that magic was omnipotent, but when it came to flying magic...

The first thing that comes to mind is gravity magic, which uses anti-gravity methods to achieve flight.

To be honest, Rudius had absolutely no clue about gravity.

Could it be that we can use magic to distort spacetime and rewrite gravity?

Am I too awesome?

I'm already so awesome, does it even matter whether I fly or not?

I need flying magic, not to enjoy the scenery, but to make it easier to get around!

If I can warp spacetime, why don't I just kill the other side?

Therefore, gravity magic was ruled out as a possibility for flight, because it's not feasible in the short term!

For Rudyus to survive, what he needs most is to increase his combat strength in a short period of time.

This is similar to Luo Yonghao. In pursuit of perfection, he could make Smartisan phones, but after going bankrupt, he still had to go live-streaming to sell goods in order to pay off his debts.

From the perspective of ordinary people, the ultimate goal of both is to make money.

But can earning money through rational effort be the same as earning money to pay off debts?

Rudyus is currently paying off his debts; he needs to increase his combat power to cross the kill threshold.

At this point, the input-output ratio becomes extremely important.

Blindly pursuing gravity magic without any clear direction is not cost-effective at this point.

After ruling out gravity magic, there are actually modern methods of flight.

In terms of modern technology, airplanes and similar devices rely on the wind pressure difference generated at high speeds to provide lift.

Looking back now, this was also caused by the density difference created by dividing the air through the shape.

In terms of shape, this is obviously not suitable for the human body. If it were to be applied, equipment such as a single-person flight suit or a glider would need to be designed.

This requires appropriate materials and manufacturing processes. In addition to the appropriate materials, one also needs to understand fluid mechanics and the like.

Honestly, even if it succeeds, Rudeus feels the investment is far too much. He'd rather focus on practicing offensive magic, which would have a higher return on investment and a better survival rate.

As for the hot air balloon idea, as Rudius knew, he thought that all it would take was to make a large balloon at any time and then use fire magic to provide lift.

But in my imagination, it looks like a balloon tied to his head, or a bucket being carried by hand.

The way force was applied in that scene was completely unsuitable for combat; it could only be used as a temporary means of transportation, so Rudeus was also rejected.

Rudeus's ideal flight is one that can save his life in battle!

But this flying magic is different now; the entire body is enveloped in thin air.

Wonderful! Absolutely wonderful!

Maybe it will be able to take off soon!

Rudius meowed more and more as he thought about it.

This not only solved his problem about how to land after taking off using earth magic catapults, but also allowed him to evolve this catapult into a combination technique similar to the catapult takeoff of aircraft carrier fighter jets.

In the sky, one can also use jet-powered magic to mimic the flight of a jet engine.

At that point, it'll be like kicking a Kamehameha!

In close combat, the thin air also acts as a natural barrier, interfering with a warrior's breathing and weakening the power of fire magic.

In the sky, by adjusting the thinness of the air, one can complete aerial rotations and fine-tuning of the body.

Even under low pressure, the boiling point of water decreases as the pressure decreases, and water vapor can hide more silently without worrying about being detected by the enemy due to the high temperature distorting the air.

Although it's only the beginning, Rudius feels like he's opened the door to a new world.

With a sudden flash of inspiration, I began to actively piece together what I had learned in the past.

This magic seems to have endless possibilities!

This is so exciting!

"Rudy?" Hilfi called out.

"Huh? I'm here."

"Rudy, what are you thinking about?"

"Hmm, I've thought of something. Sylphie, could you practice your magic on your own first?"

"Oh well……"

Being a teacher makes all the difference; Rudius controls the pace of the lesson, so even if the students' thinking goes astray, it's not a big problem.

After his initial excitement, Rudius gradually calmed down.

Start asking AI.

[Suppose that the magician can reduce the air density in a certain area around his body, creating a low-density air zone.]

However, simply reducing the density of the air around the body will not directly reduce the average density of the mage himself.

Because the density of the magician himself (including his body, clothing, etc.) has not changed; only the density of the surrounding air has decreased.

In fact, if the density of the surrounding air decreases, the weight of the air he displaces (buoyancy) will decrease instead, because buoyancy = ρgV, where ρ is the density of the surrounding air and V is the volume he displaces.

Therefore, reducing the surrounding air density will actually decrease buoyancy, making it even harder for him to float.

Rudius frowned as he looked at the description.

AI is right. If the buoyancy is equal to the mass of the air I displace, then the density of the air decreases, and the buoyancy I experience should decrease.

My preconceived notion was that the air would lift me up. In reality, a hot air balloon also holds the air in place and then uses ropes to transfer the lift.

Does that mean that when I cast a spell, there is a connection between me and the spell I cast, acting as a rope that treats me and the low-density air as a whole?

The reality is not that it is being lifted up by the air, but rather that Rudius is "pressing" down these low-density air masses. For the low-density air masses to take off, they must carry Rudius along with them.

If that's the case, Rudius then thought of something he hadn't noticed before.

Difference in air density.

This is the same logic as with steam.

Both inevitably come into contact with the air in the environment.

The only differences are temperature and density.

Steam cools and condenses, revealing its location, and air naturally flows towards areas of lower density.

This means that flight magic is a type of magic that requires a constant supply of magical energy. It requires a certain amount of magical energy output, and the greater the density difference caused by the magic, the more intense the airflow will be, and the more magical energy needs to be supplied.

Based on my brief attempt, it would require a considerable amount of magical power to fly.

To increase the required air density, it is necessary to interfere with the air in a larger spatial area; a balance must be found between space and air density.

Wait a minute, if buoyancy equals the weight of the displaced air, then why do I have to reduce the air density?

What if it's the other way around?

Wouldn't increasing the air density around you be just as feasible?

This would drastically reduce the area of ​​space requiring intervention, allowing the atmospheric pressure to simply envelop the area.

Be careful not to squeeze your lungs too hard.

Safety precautions must be taken. Pressure may cause physical discomfort, but it is not fatal and can be resolved with healing magic. Once the body is strong enough, healing magic may not be necessary.

The truly deadly condition is decompression sickness, which affects divers, and it should also apply to air pressure.

Why!?

By the way, if it only covers the legs, is this a Windwalking spell?

Is that covering the body the Lightness Technique?

If you can flexibly apply atmospheric adhesion to your body and change it at will, wouldn't it be much easier to chop people up?

Raising the sword can be easier, swinging it can be more powerful...

High-pressure air is also a means of attacking enemies... There's no need to use the magic displacement of blasts anymore; at crucial moments, you can directly choose the corresponding location and release high-pressure gas to complete the displacement.

This is a standard displacement method... and it also frees up a spellcasting slot.

Pressurization involves entirely different technical details and sensations...

Rudius wrote down all these thoughts, intending to think about them more when he got home; for now, it was still time for his class with Silphi.