Rise of Rurik

　　Use the scraps of the boat-repairing board as a writing board, and charcoal as a pen.

　　Lurik prepared many planks and a large amount of charcoal, and quickly put into measurement with the participation of other tools.

　　 He already knows a lot of key data information, such as the earth’s inclination angle and the more accurate values ​​of the pi. These two data are of great significance to the geography of the entire earth.

　　 The research on Pi actually detonated a mathematical revolution.

　　Because theologians believe in the definition of the world in ancient mathematics, they believe that things created by God must be perfect, and therefore the pi must be an accurate value.

　　 Some people oppose it and some people support it. Calculating the exact value of Pi has become a competition.

　　 But is there any special significance in calculating the inclination of the earth and the value of the pi?

　　In today's era, people everywhere don't care about the inclination of the earth, and it doesn't even matter whether the world is a plane or a sphere. Because as long as they are alive, they are already very difficult, and those who can study natural philosophy are mostly theological scholars who have come to eat.

　　 Those theologians must use this method to further prove the greatness of the Lord.

　　 However, pi has at least one important purpose, which is to more accurately calculate the circumference of the wheel and the diameter of the wheel. In this way, craftsmen can make wheels with unique circumferences, which can be installed on mechanical devices from the Greco-Roman period to help the lord measure the length of his fief and even the distance between two cities.

But for the Vikings, they did not have an urgent need in this regard. They did not even have a city in the true sense. Even the overcrowded Roseburg was a large area of ​​"shanty houses" built by a group of wood and animal skins along the bay. Area".

　　 During this period of time, the sky is beautiful, and Lurik is very happy that the sun can normally illuminate the frozen earth here at noon every day.

The temperature is quite cold. In order to get an accurate value, Rurik had to go outside from time to time to pay attention to the changes in the length of the shadow of the sun. When the shadow became the longest, he immediately took out a rope ruler to measure it and measured it. The data is recorded on a wooden board.

　　 In fact, he only needs one value, and then according to today's date, he can calculate the specific value of the latitude that the sun shines on the earth today.

　　 Time gradually reached December in the Julian calendar, and Rurik knew very well that even if there were errors in the calendar of this era, the winter solstice was definitely in this month.

　　 This can be reflected in the length of the shadow of the sun. The sun at noon is only slightly above the horizon. The standard one-stika-length wooden pole stands tall, and its shadow grows amazingly. Even so, Rurik still struggled to make statistics.

　　According to the simple Pythagorean theorem, he used charcoal as a pen on a wooden board and did some trigonometric calculations to get an angle value, a very sharp acute angle.

The most important thing 　　Lurik needs to know is the direct angle of the sun on the day of measurement.

　　Theoretically, because the sun is absolutely direct at the equator on the autumnal equinox, and on the winter solstice, the sun is absolutely direct at the Tropic of Capricorn, which is 23°26' south latitude, which is a very accurate value.

　　 is that December 22 of the Julian calendar of this era is the winter solstice, it is not credible.

　　 But Rurik has measured multiple values ​​one after another!

　　He tentatively customized the winter solstice on December 22, and the next step is to bring in the formula.

　　Since the direct sun angle only changes 23°26' in dimensionality in a quarter of a year, Rurik calculates a very accurate value for the change in the direct sun angle every day. With this calculation, he calculated that on December 1st, the direct angle of fire had exceeded 17°.

　　 For example, on December 1st, a cold, dry and sunny day, he measured the angle of the sun’s shadow on the pole and calculated the direct angle of the sun today, and finally subtracted the two data from 90° to naturally get the local latitude data.

　　 In fact, Rurik has obtained five data in succession, and the difference between them is not big.

　　 All the data show that the location of Roseburg is about 63° north latitude, with an error of about 1°.

　　 It seems that Rurik's experiment at the junior high school level has been completed. After all, he has not used more knowledge and talents of his own.

　　 Then he is very satisfied with the math results that he has been busy with for so many days, with his dark hands? Do not! He is not satisfied.

　　 Because it is only 63° north latitude, even if the maximum error is 64°, Roseburg is not enough to fall into even one day of polar night.

　　 Contrary to what he felt, there was a polar night in Roseburg.

　　 Therefore, my own measurement needs to continue.

　　 Affected by the existence of the polar night, on the winter solstice day, the east will only be slightly reddish, and the sun seems to be coming out, but it just doesn't appear. If there was a haze in those few days, there would be no difference between the situation for many days and the polar night.

　　 Obviously, in Roseburg, the local latitude cannot be measured by Sunshade. If you want to obtain an accurate result by measurement alone, you obviously have to wait until the summer solstice. That is to say, the day when the shadow of the day becomes the shortest, the summer solstice is this day. To get the data on the summer solstice, you must also take long-term measurements and record the data.

　　This matter will be a very huge project. Do you want to become the first astronomer of the Ross tribe? !

It is undeniable that the measurement of the shadow of the sun to determine the time is also very important to the Rus tribe. After all, they must go to Novgorod at the right time to collect an offering, especially in the autumn with a batch of rye. , Wheat returns triumphantly.

　　In ancient times, for any huge country, it was enough food to maintain the root of the country’s stability.

　　A huge country means a huge population. Only by growing crops and eating grains can the country maintain a huge population and remain stable.

　　 The planting and harvesting of grain is closely related to the change of seasons. A big country must set its own calendar.

　　 The only thing that can be used as a valid reference for the compilation of calendars is probably only the moon and the sun. In the end, the lunar and solar calendars were compiled. There are also Maya people who come up with non-mainstream calendars. In addition to the yin and yang calendars, they also have the Venus calendar.

　　The calendar is surveyed and compiled by the state, and the subsequent revision rights are also in the state, because the common people have almost no knowledge of astronomy.

　　 When Rome entered the empire, it needed Egyptian food production in particular. To a large extent, the increasing demand for food also affected the direction of the empire's expansion. Rome is happy to land and occupy Britain, because the fields here have been developed very early, and he is really fertile ground. For the safety of the agricultural area, they simply built a stone wall of Hadrian.

　　 And those forest areas in Central and Eastern Europe have long been areas of Slavic tribes. It is because these areas lack agricultural value that Slavs can wander for a long time as forest hunters.

　　West Rome was destroyed. Eastern Rome once inherited the territory of Western Rome. They maintained it for a short time and were finally taken away by the Franks.

　　 The Frankish Kingdom was established on the ruins of Western Rome. A series of things are completely different from the previous Roman period.

　　 But the settled barbarians need to farm to support themselves. They rely very much on the calendar set by the Romans, but few people think that the calendar will gradually become inaccurate over time.

　　 The year of the Julian calendar is a little shorter than the earth's revolution period. After 800 years of accumulation, the calendar error has actually reached six days!

　　 So the winter solstice marked on the Julian calendar at this time is completely inconsistent with reality.

　　Rurik knows this of course, he just doesn't understand what the calendar error looks like.

　　 Do you have to measure the exact summer solstice by yourself?

　　 no need!

　　 The clever Rurik suddenly thought of something that made his hair tremble, because over the years, Veria could accurately predict which day the sun would not rise, and that day was the traditional Hanukkah of the tribe. The tribe will revel in unscrupulous carnivals, drink and sing, and together witness the first ray of sunshine of the new year hit the frozen sea of ​​the bay.

　　Villa, she knows the winter solstice!

　　 Does she know the "shadow measurement method"? Or do you know other measurement techniques? !

　　 She also knows the theory that the world is a ball. Maybe she already knows a lot of geographical knowledge, but she has not revealed it to others?

　　 Is she still a classical astronomer in her seventies? !

　　Liuric became more and more confused, thinking carefully about her measurement work in the past few days, Veria was just a quiet observation, she has been watching her series of work silently.

　　 Maybe, when he was busy, Veria had understood everything many years ago?