The propagation of sound requires a medium, not air, not water, or even solids such as earth and steel, which is a physics curriculum in secondary schools. To be precise, it is introduced in the nature class of elementary school.

I remember that when he used to learn this, he liked to be downstairs and upstairs with his friends, and then knock on the fence of the stairs, and the people downstairs were attached to the fence, and they could hear a loud sound, which was used to prove that the sound was transmitted faster in the solid than in the air. So sound cannot be transmitted in a vacuum, and in space, radio is needed for communication.

It's not that Jiayi hasn't considered radio, but radio is more demanding and more refined, not to mention the reception and calculation of reflected radio waves, which cannot be achieved by a single transmission. However, if you can emit radio waves, not to mention mobile phones, at least the telegraph can be made, so that the transmission of messages will not be so troublesome.

The use of sound waves, although not as good as electromagnetic waves, is indeed the best way that Jiayi can think of under limited conditions, and the rest is almost impossible for Jiayi to achieve

"Teacher. Jia Yi looked at Orlando, although he was a little surprised, but he was not at a loss, "I understand the shortcomings of sound wave detection, but this is also the best way I can think of now, and in addition to humans, when I am adventuring outside, it is also very good to use it to detect Warcraft beasts in the wild or detect terrain." ”

Orlando's face softened a lot: "It's good that you have this psychological preparation, so as not to feel that the gap is too big in the back, but this is indeed a good spell in the wild, after all, the beast or the monster will not know the principle of the detection technique, and it will not be able to avoid these detection spells, and the safety is also greatly guaranteed."

"But even if there is a circle to keep watch, you must always be vigilant. You must know that in this world, there are monsters, evil mages, and scum who worship demons, all kinds of spells or magic items are strange and have different abilities, and there is never a kind of defense or warning spell that dares to say that it is foolproof. All defenses will eventually be cracked, even if there are monsters in the wild, you can't guarantee that none of them can absorb sound, since there are those that detect through sound, there must be those who absorb sound to avoid detection. ”

Jia nodded and said that he was taught, as safety first, Jia Yi never joked with his own life, this world is likely to be the only one such a traverser, no matter how you calculate it, it is also a protected species such as Tetete, no matter how it is protected, it should not be too much.

"Hey, Orlando, did you read the part below?" said Fergus suddenly.

Orlando stretched out his head curiously, and said: "Look here, he proved that bats are able to identify obstacles through hearing, and it is not over, and he also experimented with the vision of bats, proving that there is no problem with bats' eyesight, and the eyes are also useful." It's nice to have a subconscious idea that a bat is blind because it can detect its surroundings with sound waves, and it can eliminate blind spots in thinking. ”

"It's ok. Orlando said lightly, but the smile on his face was almost uncontrollable, and he only had to maintain a reserved attitude as a teacher, so he could suppress his smile.

"Then looking at it this way, is it really possible that the spider's auditory organ is on the leg?" Fergus said suddenly, startling Jia Yiyi, he didn't expect him to think of this so quickly, and he originally thought that he would conduct this research himself and be in the limelight.

Now this B can't be pretended, and Jiayi feels a little lost.

Orlando also looked moved, but did not agree with Fergus's thoughts: "How can there be such a coincidence." If that were the case, wouldn't the joke we've been telling for so many years really become a joke. ”

Kaichi disagrees with Orlando's idea, and even if the wrong method accidentally hits the right conclusion, it doesn't make any sense, because it lacks theoretical support, and you can't even be sure if you're actually getting the right result. Only the results obtained in the right way have universal significance.

Jiayi said what he thought, Orlando didn't say anything, but Fergus praised Jiayi. In fact, Orlando also appreciates Jiayi's statement, but as a teacher, you have to maintain your majesty.

After discussing Jiayi's experiments and papers, Orlando said, "Jiayi, your mage badge hasn't been activated yet, let's take you to activate it." ”

"Activate?" Kaichi pinched the mage badge on his chest and glanced at it, it was shining with silver light, and there were additional spell effects that kept the badge clean for a long time.

Is there anything else that can't be done?

Fergus said: "Of course, the mage badge is not just used as proof of identity, but of course it is the most important thing. After exchanging keys between mages, when you use the badge to set a key on a letter or other package, only the mage you exchanged the key can use the corresponding key to open it. Although the mage himself can set the secret key by himself, it is inconvenient to exchange the secret key and save the secret key, and it is not good to record it on paper in case it is read by others.

"Another important role is to record your identity information, to this mage association, many places are not allowed to enter casually, if you want to enter, you need to apply, after the application, the permission will be attached to your badge. There is also information about your paper, which will have Arcane Points, which will give you more privileges and benefits, which are also stored in the badge. You can even deposit money in the Mage Guild and trade it with badges. There are many other functions, if you are in the field, it doesn't make a big difference whether you have a badge or not, but in a mage association or academy, it is almost impossible to move without a mage badge. ”

Jia Yi heard and understood, the so-called mage badge is almost a set of ID cards, social security cards, cards, bank cards, meal cards, access control cards, etc.

"So what if it's lost? What if someone else picks it up? Isn't that the identity inherited by someone else?"

"What do you want? This badge is soulbound and can only be used by you. ”

"But when I got the badge..."

"That's why I asked you to come to the Mage Association to bind it. Before Jia Yi finished speaking, he was interrupted by Orlando, "The badge sent to you is simply used as proof of identity to prove that you are already an official mage, but if you want to use the various functions of the badge, as well as the binding of your paper information, you need to go to the mage association in person to activate it." There are various mage guilds scattered all over the world, and any of them can be activated. ”

"All the activation information is in duplicate, one is stored in the badge, one is stored in each high council, and the mage associations in various places are backups, and every cycle, the local associations will go to the high council to obtain the latest mage information, and at the same time submit the information handled in the association. If your information is not synced, it will not be recognized and will only work properly until it is synced. ”

Jia Yi couldn't imagine that the information storage of the mage had reached this point, isn't this cloud synchronization, if it is only stored locally, then there will always be a mage who can break through the protection and rewrite the information stored inside.

They take the elevator and go up, and they don't know which floor they have reached, so how can they determine which floor this elevator is?

Then Fergus and Orlando led Garnichi to a large hall that occupied an entire floor of the tower, with an intricate magic circle in the middle. This circle looks a little old, and many places are peeling off, revealing the lines of the circle protected by the covering, some of which look like broken wires, and there are many traces of repair that can be seen.

Jia Yi stared at this magic circle carefully, trying to see some mysteries, but after a while, he was dizzy and retreated.

"Stand in the middle, take the mage badge in your hand, I'll activate the badge for you, remember to take off all the spell items on your body, so as not to interfere. Fergus commanded.

Jia Yi obediently put the backpack outside the circle, took off all the talismans on his body, and put them on the backpack, then took the badge off his chest, held it in his hand, walked to the center of the circle, looked at Orlando and Fergus, and wanted to see what instructions he had next.

However, Fergus didn't say anything, and directly chanted the incantation, and began to activate the magic circle, and then, Jia Yi saw that the magic circle slowly became brighter, especially some parts that were damaged to expose the materials used to build the magic circle, and became very bright, like a lit fluorescent lamp, but the brightness was brighter, so bright that Jia Yi was dazzled, and he couldn't see anything clearly, so he could only close his eyes.