Chapter 446: Set off again

In addition to observing the starry sky, you must also observe the sun and its incident angle to the local area at different times.

After ten years of continuous exploration and improvement, Su You discovered with laughter that with the glass lens and the brass instrument panel with precise angles, the theodolite was transformed by Taoist priests to become more and more like the sextant of later generations, even the black light-shielding

The glass sheets are installed and divided into different layers to withstand sunlight with different intensities at different times.

No one is a fool! This is almost indistinguishable from the sextant of later generations!

After the national statistical data were compiled, Si Tianjian and Yu Juguan discovered that at the same time point and at different locations, the incident angle of the sun was different! There was a difference between the time calculated based on the star catalog and the time calculated based on solar measurements.

, there is a difference!

In terms of people's lives, this thing actually has no impact. Just work when the sun rises and rest when the sun sets.

But this is a very serious problem for Si!

First of all, it is a question of legality. Which time is the standard?

This matter also attracted various gods and demons to fight, from Yu Gong to Kyushu, to Sunrise Fusang in the world. Finally, the boss of Si Tianjian solemnly stated that Your Majesty, the throne position of the Zichen Palace in the Bianjing City Palace must be the only one in the world.

Standard time observation point!

Zhao Shu was dumbfounded when he heard it. Aiqing, what you said makes sense. There is only one question. Are you going to climb on top of my head to observe?

Fortunately, one of the important application methods in science and engineering is flexibility. Si Tianjian replied: "This question is very technical, but after our observation, we found that this time has a greater relationship with the east-west position of the region and less with the north-south position. We can

Set up an observation point in the direction of due south and due north of the throne, and just measure it accurately."

Zhao Shu breathed a sigh of relief. It was so dangerous, but fortunately there was a perfect solution.

A few years later, an astronomical calendar with this point as the origin was produced, and the Taoist priests made a new discovery, that is, lines connecting the same time points cannot divide the earth according to normal straight lines on the map!

Question after question, everyone in Si Tianjian almost cried.

Who can solve it? Everyone thinks of one person.

It's not Su You, it's Su You's clan brother, Su Song.

Su Song studied the map and the longitude lines on it and came up with an idea.

"Huainanzi Lan Mingxun": "In ancient times, the four poles were abandoned and the nine states were divided; the sky was not covered, and the earth was not divided. So Nvhu made five-color stones to mend the sky, and cut off the Ao to stand up the four poles."

Could it be that the earth is not completely flat? Instead, it is like the back of a turtle? Only in this way can such an effect appear when the sun shines on it?

Damn it! Su Zigao is indeed amazing! This is the only explanation!

After such a happy decision, Kyushu Meridian was launched.

There has always been a theory of divisions in ancient China. After the theodolite became easy to use, the Taoist priests converted the geographical divisions corresponding to the stars into the scale divisions of the theodolite, so that measurements could be more accurate.

This also requires the measurement of latitude.

The measurement of latitude is relatively simple because there is Polaris, the standard positioning star that astronomers have been using in the northern hemisphere.

The altitude angle of Polaris is the latitude.

Therefore, due to various errors, the longitude and latitude of the celestial sphere that existed long ago became the longitude and latitude of the ground.

As for the hourglass, the length of the day is measured, and then divided into twenty-four parts, so that the sand in the hourglass can drain out in exactly half an hour.

The hourglass is made of glass, so you can easily see the leakage of sand inside.

It's still the same as the subtle and pure one. The sun's time is different every day. This is called a true solar day.

So we need to take an annual average, which is called a mean solar day.

Zhang San understood mathematical trigonometric relations and light refraction, but when Su You placed this pile of things in front of him, he was still a little confused.

Brother Qi used a sky-gazing mirror to look at the moon, but he got into a lot of trouble.

Su You patiently drew pictures and explained that the sextant is only useful on the sea, but there is really no way to use it conveniently in Meishan.

Because this thing requires a sea level.

But the principle can be drawn, and it's not complicated at all. It's just an angle ruler, a horizon mirror on one side, an index mirror, and a telescope.

When the index arm coincides with zero degree of the angle ruler, the horizon mirror and the index mirror are parallel.

An observer uses a telescope to observe the sea level, and his sight goes through the horizon mirror. The horizon mirror is half transparent and half a mirror. At this time, there is no sun in the mirror.

Keep the telescope stationary, rotate the angle ruler, and the angle ruler drives the index mirror to adjust its angle. Gradually, the sun is reflected by the index mirror, appears on the horizon mirror, and is finally tangent to the sea level.

Write down the angle reading on the sextant scale at this time, and through a series of calculations, you can get the incident angle of the sun.

At different latitudes, the angle of incidence of the sun at noon is different. This can be checked through the astronomical calendar. Even if it is not within the statistical range of the Kyushu astronomical calendar, the precise latitude of the location can be obtained through calculation.

Longitude can be calculated using time difference.

Through the ephemeris, the standard time of Bianjing can be observed at night, and then the time is recorded with an hourglass. Then the sun at noon at the location of the ship is measured during the day, and the time difference between the measuring point and Bianjing can be obtained, and the longitude can then be calculated.

For Zhang San, this is a life-saving magic weapon.

On the vast sea, there is nothing more important than knowing where the nearest port is and which direction to drive.

Also, in the past, the only way to proceed was by sailing along the coastline to find landmarks. From now on, we can adjust to taking shortcuts.

What does the Meishan proverb say? Time is money, efficiency is life!

Of course, these are only feasible in principle. Only through repeated measurements, experiments, and combination with experience can an effective method be finally formed.

This task fell on Zhang San. Compared with shipbuilding, this was a core technology that the Qian family could not master for a while.

From now on, every time I go to sea, I will improve my nautical charts and route charts step by step. With giant high-speed schooners and navigational surveying skills, the sea will no longer be a daunting journey.

As for the human threat, even in a few hundred years, no country's sea vessels can be a rival to armed schooners equipped with ballistae.

In June, the renovation of the new sailboat was completed, and Suzhou Petroleum began an inspection tour within its own jurisdiction.

When people get old, they are reluctant to move. Hachigong has never been out of Kerongli in his life. Su You wants him to go to Bianjing to enjoy his life, which is a luxury hope.

What's more, you may not necessarily enjoy more happiness in Bianjing than in Meishan.

In Bagong's eyes, apart from being crowded and close to the official residence, what else is better than Meishan?!

No matter how reluctant he was to leave, Su You could only wave goodbye to Hachigong and his group who were seeing them off. Many people didn't know if they could see each other again after leaving.

Zhong Yi's mathematics has improved by leaps and bounds, because interest is the best teacher.

The six thousand elite troops of the Xia army in Shuiluochuan were annihilated like butter with the help of grenades; a fire and explosion outside Weizhou City plunged the 70,000-strong army into chaos and leaderless. This completely overturned this child's understanding of the war.

know.

The decisive force in future wars must be firearms!

To use a ballista flexibly and freely, knowledge of mathematics and physics is indispensable. Any good artillery commander in later generations must first be a scholar proficient in mathematics.

Su You was indispensable. Mathematics problems, ten years of translation, compilation and memory, as well as practical applications in science and engineering, accumulated them one by one, which is a lot.

In the future, I may not have many opportunities to lead an army in battle. When these boys grow up, they will be the real minions of the Song Dynasty.

The canal boats followed the newly rising river water all the way eastward. Everywhere they went, Su You summoned the barbarians and Han people to preach the new policies of the court, check warehouses, roads, bridges, and taxation, and listen to the work reports of the canal officials.

As the spokesperson of the emerging commercial and financial consortium, it goes without saying that it promotes the use of Shu banknotes. With the company's elite accounting team as a statistical and verification force, it is almost impossible for subordinates to get through the accounts.

The healthy economic growth of Sichuan for more than ten years has covered up many flaws in local governance.
Chapter completed!