In the northern suburbs of Xiyang City, Xiyang Wangfu Lakeside Manor, in the courtyard, Yu Wenwen is using the "Liu Shiyuan projector" to measure the latitude he is in. Pen, fun, and www.biquge.info

Longitude and latitude are a normal concept for him, but for this era, it is a fantasy.

When talking about latitude and longitude with people, it is similar to playing the piano to the cow, and Yang Ji can barely understand it, but Liu Zhuo, who has rich experience in astronomical observation, can understand what "latitude and longitude" is.

The premise is to recognize that the earth is actually a sphere, otherwise the concept of latitude and longitude cannot be discussed.

This kind of topic is too shocking, Yuwen Wen can only discuss relevant content with Yang Ji and Liu Zhuo, if it spreads, although there is no need to be burned at the stake, it will also make people think that he is crazy.

Recognize the "earth", then it is much easier to talk about latitude and longitude, but Yu Wenwen belongs to "you can't talk about theory, I can't talk about practice", he said that the latitude and longitude is a set, but he is confused about how to measure.

The principle of measuring latitude and longitude is very simple, use a sextant!

So the question is, what is the structure of the sextant?

Uh, don't know.

Yu Wenwen didn't know, but he knew this concept, at least he knew that the shape of the sextant was fan-shaped, and its indexing arc was one-sixth of the circumference.

And Yang Ji didn't know what a "sextant" was at all, because at the end of the Ming Dynasty, the sextant was not even invented in the Central Plains.

Yuwen Wen and Yang Ji couldn't "invent" the sextant even if they wanted to break their heads, but Liu Zhuo, a real astronomy expert, was "thoughtful" about this idea.

To measure latitude, you need to measure the shadow (angle) of the sun, which is very simple to achieve, that is, to set up a pole to observe the shadow of the sun, but if you want to make a portable instrument that can measure latitude in your hand, it is not simple.

After several years of continuous improvement, Liu Zhuo finally made a handheld projector that is simple to use but works very well.

The principle is simple: instead of looking directly at the sun, the user observes the shadow cast by the stick on the scale, the position of which indicates the height of the sun, so that the latitude can be calculated.

In line with the thinking of technology patents, Yu Wenwen once planned to name this instrument "Liu Shiyuan Projector", or "Liu's Projector", but that was just a thought.

After all, for the readers of this era, it is really disgraceful to use their name on objects.

Therefore, the official name of this instrument is: orthodox seven-year mass-produced projector, inventor: Xindu Liu Shiyuan, patent transfer fee: 5,000 yuan.

Everyone is so familiar, and the relationship is so good, talking about money hurts feelings, not talking about money but dampens the enthusiasm of invention and creation, in order to encourage technological innovation, Yuwenwen does not hesitate to spend money.

Latitude can be easily measured, but what about longitude? Not at the moment.

A projector that can only measure latitude, wants to evolve into a sextant that can measure latitude and longitude, when it can be realized, there is no bottom at all, but one thing Yu Wenwen can be sure of, longitude and time are related.

The earth is a sphere of 360 degrees, and one rotation is one day, which is counted as 24 hours, so the time difference of longitude is one hour for every fifteen degrees.

Continuing to subdivide, the time difference between each degree of longitude is four minutes, as long as the time difference between the two places can be known, then the longitude difference between the two places can be calculated.

Based on the time of the Huangzhou Xiyang City Observatory, if the time in a certain place is 8 o'clock in the morning, and at the same time the Xiyang time is 7 o'clock in the morning, and the time in that place is one hour earlier than the Xiyang time, then the longitude of this place is 15 degrees east of Xiyang.

If the time in a place is four minutes slower than the time of the sun, then the longitude of the place is one degree to the west of the sun.

Then measure the latitude, then there is the latitude and longitude coordinates here, the principle is very simple, but it is difficult to implement, because this requires an accurate clock, the error rate of the year \ month is very small, and the clock that Xiyang craftsmen can make can not reach such a low error.

The difference is thousands of miles, longitude and time are related, the error is a few minutes, the measured longitude error will lead to a gap of hundreds of kilometers, and if you want to make the method of measuring longitude practical, you can only rely on accurate clocks.

Used in navigation, it is a marine clock, because the sea is very turbulent, so the clock with a pendulum is greatly affected, and it must be replaced with another escapement that is not affected by gravity in order to put the marine clock into practical use.

It's very simple to say, but it's hard to do, Yuwenwen can only play lip service, Yang Ji doesn't have much energy, he can only rely on the craftsmen of the workshop to brainstorm and use exhaustive methods to ponder.

After pondering for several years, I barely managed to make a bump-resistant clock as large as a rice cylinder, and the yield was very low, barely enough to make up five units, so that people could take the ship to sail, so as to verify the accuracy, and then continue to improve until the requirements were met.

How long will it take to improve?

In the original history, it was a British craftsman who invented the practical marine clock, and his first marine clock was very large and took five years.

The second edition of the Nautical Clock, in which problems were identified during improvement, followed by the third, more accurate version, took almost two decades, and the fourth edition, which was miniaturized, took several more years.

How many twenty years are there in life? Yuwen Wen couldn't afford to wait, so he decided to find another way.

Columbus discovered the Americas, and there was no accurate clock at hand, and this navigator relied on the principle of "the earth is round" to sail in equal dimensions, so Yuwenwen, who could accurately measure the latitude, could send people to open up new routes.

"Discovery" of the Americas is unrealistic, because it requires a strong interest drive in order to maintain the transoceanic route, and the consequences of the great geographical discovery triggering the great voyage are not what Yuwenwen can bear today.

The maritime merchants of the Eastern Roman Empire, Persia, and the Tianzhu states had established well-established routes from West Asia to Canton in East Asia for hundreds of years, with a strong maritime trade group and a large number of experienced sailors.

Once it is known that there is a golden continent on the other side of the distant eastern ocean, the fleets of the maritime trade group of these countries can break through the stormy seas and go to gold panning without fear of hardships and dangers, but what about the fleet of the maritime trade group in the Central Plains? Where is it?

Not to mention that the imperial courts of the Central Plains were not interested in navigation at all: I am a dignified kingdom of the Heavenly Empire, rich in products, and fertile for thousands of miles, what do you want to do in the land of barbarians?

There is no strong demand for interests, and the discovery of the new continent is just to make wedding dresses for others, and Yu Wenwen, who burns money to study latitude and longitude measuring instruments at his own expense, is not so generous.

The most realistic choice is to "invent" a route that only matured in the middle of the Tang Dynasty in advance, that is, a direct route from the Central Plains to the Wa Kingdom.

The estuary of the Yangtze River (not far from the lower reaches of Guangling and Jingkou in this era) is at the same latitude as the Chikushi Island (later Kyushu Island) of the Wa Kingdom, so according to the principle of contour at equal latitude, it is possible to cross the Heishui Ocean to reach the southwest end of Chikushi Island by sailing directly to the east at the mouth of the Yangtze River.

With the navigation technology of the Tang Dynasty, sailing from Mingzhou in the Central Plains (later Ningbo) can reach the Wa Kingdom in six or seven days when the wind is downwind, saving time and effort, so Yuwenwen has high hopes for this new route that will appear more than 100 years in advance.

It only takes a few days for the new-style big ship to sail down the river to Guangling, and if it goes well, it only takes six or seven days to sail directly to the Wa Kingdom, and the whole journey adds up to less than 20 days.

Yu Wenwen optimistically estimated that it would take about a month and a half for the ship to return from the Wa Kingdom and enter the Yangtze River to reach Bakou in Huangzhou in the middle reaches. The total time for this round trip was about two months.

Large-scale caravans traveled by land to and from Xiyang and Yecheng, which took about two months, and the time required for the two trade routes to go back and forth was about the same, but the profits were very different, and with the drive of huge profits, the desire to maintain the route would be very strong.

The premise of sea trade is that the fleet does not encounter shipwrecks, otherwise people will lose all their money, but this is not a problem for businessmen.

Yuwen Wen didn't need to work so hard, but at this point, he had to take risks, in order to have a solid small group, he, the "leader of getting rich", had to find a way to find more ways to make money.

The new "money way" is in his hands, and the countless businessmen who rely on these "money roads" to support their families, as well as the owners behind them, that is, the local snakes, will be like drug addicts, can they still be separated from him?

It is even harder to touch interests than to touch souls!