Chapter 88

This dye has very strong adhesion and water resistance. Once it is applied, it won't smudge unless it gets too wet, and once it dries, it is very difficult to wash off. The innermost layer of whale skin is a thin, smooth layer with few patterns, making it very suitable for use as paper. Hong Tao drew many horizontal and vertical lines on the whale skin he gave to Karl and Bo Jiao, resembling a Go board. However, unlike a Go board, these lines were not perfectly horizontal and vertical. Only the middle horizontal and vertical lines were straight, while the other lines had a certain curvature.

"Sir, what is this?" If it were a modern person, they would immediately recognize these lines as the Earth's latitude and longitude lines, but Karl and Bo Jiao were truly puzzled.

"This is a navigation coordinate system I invented. The horizontal lines are called latitudes, and the vertical lines are called longitudes. As long as these lines are measured accurately, the entire world's oceans will be our backyard, and we will never get lost. Don't ask why; just listen carefully to every word I say and follow every instruction I give. Remember, this is my highest secret. It's best not to tell anyone, not even your parents. If you can't do that, let me know in advance, and I will have you removed from this work. Do you understand?"

Hong Tao shamelessly claimed latitude and longitude as his inventions. In fact, this made things easier, as he didn't have to explain the complex formulas for calculating latitude and longitude, which would take a whole day to explain and involve a wide range of knowledge that people of this era couldn't understand.

"Is this a map of the sea?" Karl, though not a formal naval officer, had commanded the Holy Roman Empire's fleet. When Hong Tao explained, he immediately understood and was very excited, thinking about going home.

"You can say that, but this map is currently blank and incomplete. I need a few years to correct it. Are you willing to work with me on this?"

Hong Tao felt very dirty, always using Karl's desire to go home as leverage.

"I am extremely grateful. I swear to the Lord that I will not reveal the map to anyone without your permission." If Karl had been skeptical when Hong Tao first told him he could take him home, now he almost fully believed it. A person who could draw a map of the sea would be a king's honored guest anywhere, even if they could only draw a map of the empire.

"Uncle, I won't say anything either!" Bo Jiao didn't understand what Karl and Hong Tao were talking about, but seeing Karl kneel, he realized the seriousness of the matter and also knelt down.

"In the future, don't call me Uncle on the ship; call me Captain. Do you see this? It's called an hourglass. When all the sand has fallen to the bottom, it takes one and a half hours. Each time you flip it, you must mark a line on the wooden base. Whoever flips it must mark it, and you must not forget or mark too many, or we might never be able to go home." After explaining the latitude and longitude lines, Hong Tao pointed to two large hourglasses fixed in wooden boxes on the cabin wall and continued to instruct Karl and Bo Jiao.

These hourglasses were made of silver frames inlaid with crystal thin sheets, very exquisite, and Hong Tao had specially commissioned a goldsmith to make them for over 20 units of labor. The sand inside had been washed many times and sieved through several different sieves to ensure the grains were of similar size. They had also been calibrated with the water clock at the city's maritime office in Zhenzhou, making them relatively accurate. Hong Tao couldn't think of a better way to measure time. The water clocks of the Song Dynasty were large, could not be jolted, and were affected by temperature, making them unsuitable for use on ships.

"… Yes …" This time, Karl and Bo Jiao understood and immediately focused their attention on the two hourglasses fixed in the wooden boxes, watching them intently.

The place Hong Tao was going to was Hong Kong Island, and he needed to find the approximate location of the Central Pier from his previous life. The intersection of the horizontal and vertical lines on the whale skin, which were perfectly straight, marked the Central Pier. Why did he need to find the Central Pier and fix the latitude and longitude baseline there? The reason was simple: Hong Tao could remember the specific coordinates of a few ports, most of which were in North America and Europe. The two places he was most familiar with in Asia were the Central Pier in Hong Kong and Mai Island in Qingdao. This was closely related to his experience of driving sailboats and private planes in his previous life, where the GPS navigation devices on sailboats and planes displayed coordinates as numbers, and he naturally remembered a few frequently visited places.

With these two coordinates, Hong Tao could use them to draw a preliminary global latitude and longitude map. Since the numbers were absolutely accurate, with two points and their specific coordinates, extending other latitude and longitude lines would be very easy. With the accurate baseline, this would be the zero point, and Greenwich and the Prime Meridian could take a back seat. In the future, the latitude and longitude lines on the map would be called the Hong Line and the Bo Line. He doubted anyone would object, and if they did, they could keep their opinions to themselves. If they had the ability, they wouldn't use it.

Since he had accurate latitude and longitude lines, why did he need to measure them personally? Was Hong Tao going to use his rudimentary instruments to verify the authority of satellite laser positioning? No, Hong Tao wasn't that foolish. On the contrary, he was going to use the accurate latitude and longitude lines to verify the precision of his equipment and calibrate them more accurately, while also drawing a small part of the sea map.

With these grids on the sea map, he could use a sextant to measure the latitude and use the stars to determine the longitude, then use the existing latitude and longitude to draw a basically accurate coastline and island coordinate map. Each time he went to sea, he would measure some data and continuously add it to the sea map. When Bo Jiao, Bo Yu, Bo Xia, and others grew up and had their own ships, they would bring back data and marked sea maps from all over the world. By comparing and integrating this data, Hong Tao's overall map would become increasingly rich and would eventually become a world sea map.

With this sea map, even without the entire map, just a few parts, Hong Tao could dominate the world's oceans. The sextant, hourglass, and sea map were his navigation tools. If he could also build seaworthy long-distance sailing ships, he couldn't think of anyone who could challenge him on the high seas. As long as he was willing, he could use these three tools to extract enough wealth from any country, build enough warships, recruit enough sailors, and blockade, invade, or destroy any country that relied on the sea.

Moreover, this sea map was not afraid of being stolen. Without a sextant and an accurately timed hourglass, it would be impossible to measure accurate latitude and longitude. Having the map would be useless, and venturing into the open sea would mean certain death. Even if they stole the sea map, sextant, and hourglass and knew how to use them, without his brain, it would still be useless. In the 13th century, were there people who could perform accurate calculations using trigonometric functions?

Don't mention ancient Greek or Indian mathematicians; they only proposed a concept and a vague calculation method. They didn't know the precise formulas. Furthermore, if they didn't understand that the Earth is an oblate spheroid, the latitude and longitude lines on the map would be a trap for them. Since the spherical surface is flattened into a plane, both maps and sea maps are projections, which have significant errors compared to reality. Navigating strictly according to the latitude and longitude on the sea map would be very dangerous.

Hong Tao didn't plan to keep this secret forever. When he had the ability to control his own destiny, he would establish a school to teach these skills and let the knowledge spread naturally. Before that, he would make a fortune by selling sea maps to other countries. If someone wanted a sea map for a specific route, he would give it to them, but they would have to pay for it. They wouldn't be able to use it without hiring graduates from his school to help with the measurements, thus providing the students with decent jobs.

When this technology spread and he no longer had a technological advantage, he would probably be too old to do much. By then, he would have accomplished what he needed to do, and what he couldn't do would still be impossible even after a hundred years. New, more precise technologies and equipment would likely be developed, and he would have completed his mission. It would be time to close his eyes and rest, as living too long would be a burden.

In fact, even with sea maps, sextants, compasses, and hourglasses, long-distance navigation remains a very dangerous endeavor. Longitude is easy to measure but difficult to measure accurately. To obtain relatively accurate longitude, a marine chronometer is needed. This is a clock that can resist temperature and humidity changes, withstand jolts and waves, and have a small error. It is like an accurate hourglass, faithfully recording the passage of time. With this as a standard, longitude is easy to determine. Theoretically, longitude is a time difference. By measuring the time difference between your current position and your starting position and using a formula, you can obtain a relatively accurate longitude value.

Unfortunately, Hong Tao couldn't make a marine chronometer. Not to mention a marine chronometer, he couldn't even make the oldest pendulum clock. Clockmaking was not a profession he was interested in, and he only had a general understanding of clock mechanisms, not enough to replicate them.

Without a marine chronometer, the position of the moon and stars can be used to determine longitude, and a sextant can do this. However, a lunar distance table is needed. This is a table compiled by ancient astronomers over many years, showing the relationship between the moon's orbit and several fixed stars. Hong Tao had seen and used this table, but it was created by later astronomers and did not exist in this era. Therefore, only he could use the lunar distance method to measure longitude. In other words, he was the only person in this era who could measure relatively accurate longitude.

PS: Click, collect, and recommend! Throw them all to Hong Tao...

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