"Let's go and make a sundial!"

Having solved the problem of brushing teeth and toilet paper, Sun Yi immediately set out to solve the timing problem. Pen, fun, pavilion www. biquge。 info

——The time in Sun Yi's mobile phone and the actual time in Wolf Mountain do not match, and Sun Yi has to look at the sun every time he estimates the time.

In the morning, Sun Yi had already arranged for someone to place a spear in the open space next to the shack, recording the position of the spear's shadow at different times.

Now just connect the positions of these shadows to get the sun's trajectory and make a simple timekeeping sundial.

Jia Daoshi straightened his chest, "No problem, let's look at the poor Dao means!" ”

Taoist priest, two rituals and four elephants gossip compass, it's not easy to draw a sundial?

Sun Yi took the baby's hand, the baby blushed with shame, and the three of them came to the open space.

I saw a spear stuck diagonally on the ground, and there were many small stones scattered on the north side.

These small stones are where the shadow of the spear is.

Jia Daoshi was stunned, these small stones are not on a circle! The long grass is not perpendicular to the ground!

I had the intention to re-erect the long grass, but the shadow position recorded in that way was useless.

Daoist Jia muttered, "Master, I can't draw this sundial, and the spear on the ground is not straight at all." ”

The milk baby broke away from Sun Yi's hand, "Master, let me try." ”

The baby trotted back to the hut to fetch a ball of thread, hoisted a small stone from the top of the thread, raised it high to become a plumb weight, and raised her hands and toes to reach the highest point of the spear.

Sun Yi understood, and picked up the baby at once.

The baby was so ashamed that the roots of her ears were hot.

The baby reached the top of the spear, and when the little stone under it stopped shaking, let go, and the stone fell—this is the center of the circle.

The milk baby almost struggled to push Sun Yi away, pulling the line from the center of the circle to the nearest shadow position and stopped.

Sun Yi held down the center of the circle and threw a freshly made chalk to the milk baby.

"Baby, go on!"

The baby didn't catch it.

The milk baby picked up the chalk that had been broken into several pieces, stretched the line, and drew a standard circle around the center of Sun Yi's circle.

The baby first drew a chalk line in the shortest part of the shadow - this is due north.

The baby walked and stopped along the circle, and drew a chalk line in the position of due south, west, and east.

The baby walked a few more times, on each quarter of the arc, and evenly drew two lines, the whole circle was divided into twelve equal parts, and finally the baby in every twelfth of the arc dotted a dot, twenty-four equal circles completed.

Sun Yi circled around in confusion.

The circle is very evenly divided, and the ruler is no more than that.

"Baby, how did you do that?"

The baby's heart is still "pounding",

"I'll first estimate the position in my heart, and when there are more or less, I will adjust it in my heart, and when I get it right in my heart, I can just draw it directly."

Sun Yi looked at the baby in disbelief.

"Who taught you to use a plumb to find a vertical and a line to draw a circle?"

"I've watched Da do this since I was a kid, so naturally it will."

"Have you ever used chalk before?"

"Nope. I do all my needlework with drawing stones. ”

The milk baby picked out a small piece of white stone from the thread ball and handed it to Sun Yi.

This little white stone is delicate and soft to the touch, and Sun Yi drew one on the ground, which is much better than his own chalk.

Sun Yi rubbed the little white stone vigorously, a familiar feeling - talcum powder!

It turns out that the painting stone is talc, no wonder it is more delicate than chalk.

Sun Yi wanted to laugh a little.

I deliberately played with it just now, but I didn't think that the "chalk" of the milk baby was much easier to use than my own.

Jia Daoshi asked for a piece of chalk and lay on the ground to write the name of the twelve hours.

Sun Yi estimated the current time according to the position of the spear's shadow on the circle, and changed the clock of his mobile phone to "Wolf Mountain local time". The error is estimated to be at least plus or minus 10 minutes, but it is sufficient.

The circle on the earth is empty between two hours next to each other.

Sun Yi said to Daoist Jia, "Can you draw the scale as well?" ”

Daoist Jia shook his head resolutely,

"The big and small moments are different between the hours, I can't draw them!"

Sun Yi couldn't help but wonder.

Jia Daoshi explained to Sun Yi that the timekeeping system of the Ming Dynasty at this time was one hundred quarters a day and twelve hours a day.

In this case, each hour is eight and a third of a quarter.

In order to solve the problem of one-third quarter, the Ming Dynasty divided each hour into eight quarters, two small quarters, each of which was equal to one-sixth of a quarter. The small tick is placed at the beginning and the first position of each hour.

For example, noon in the Ming Dynasty began at 12 o'clock in later generations.

The first quarter of noon = 12:00:00

One quarter at noon = 12:02:24, which is equivalent to one-sixth of a quarter

Two quarters of noon = 12:16:48, which is equivalent to one and a sixth of a quarter

Three quarters of noon = 12:31:12, which is equivalent to two and one-sixth quarters

Four quarters of noon = 12:45:36, which is equivalent to three and a sixth quarter

Sun Yi almost knelt down, it turned out that Harry Potter's nine and three-quarters platform really existed in reality.

When Sun Yi was a child, he hated to do the math problem of speed conversion, from meters per second to kilometers per hour, and then from kilometers per hour back to meters per second. At that time, Sun Yi thought that one hour and sixty minutes, one minute and sixty seconds were deliberately invented to torture elementary school students.

Now it seems that every hour and a third of the hour in the Ming Dynasty did not leave a way for primary school students to live at all!

It is no wonder that some people say that the level of mathematics in ancient China has been regressing, so that many mathematical works of the previous dynasties were not understood by the Ming Dynasty.

Such a timekeeping system absolutely properly strangled the little mathematicians in the cradle.

Sun Yi announced without hesitation,

"From now on we will have ten quarters of an hour and ten minutes at a quarter! Baby, you immediately draw ten more partitions between every two hours! ”

Jia Daoshi gave a salute to Sun Yishen: "The master wants to restore the Han system, I agree!" ”

Sun Yi was surprised, his own regulations were actually Han system!

Seeing that Sun Yi didn't understand, Daoist Jia explained,

"In Qin, the day and night were five minutes each. The day is the morning, Yu, middle, sun, and night. The night is A, B, C, D, and E. The night watch, the first night, the second night, the third night, the second night, the second night, the fifth watch, is also called the first watch, the second watch, the third watch, the fourth watch, and the fifth watch. This is actually the number of ten days, which is ten watches. ”

"In the Han Dynasty, a day was twelve minutes, called midnight, rooster crow, pingdan, sunrise, eclipse time, yuzhong, day, sunday, sunset, sunrise, dusk, and people. It is represented by the twelve earthly branches, which is twelve hours. ”

"Since then, it has become customized, if a day is recorded at twelve o'clock, it is said that the child is ugly and the sun is not applied for the noon, and the clock is used to tell the time, which is called the hour or the time point; If a day is recorded with ten changes, it is said that A, B, C, D, pentahyl, hexageng, xin, and non decay, and the drum is reported to be more, which is called a drum beat or a change point. ”

"The Han system is one hundred and twenty quarters a day, but one hour and ten quarters. The Ming system is 100 minutes a day, but it is to take 10 minutes. ”

"The lord returned to the Han system, one hundred and twenty quarters a day, ten quarters at one hour, and twelve quarters at one shift. And the master emphasized in his words that the minutes, the quarter of the hour, and the minutes are the clocks, which are different from the drums of the Ming Dynasty for a hundred quarters a day. ”

After that, Jia Daoist actually squatted down, counted twelve and twelve on the circumference of the one hundred and twenty quarters that the milk baby had been divided, and marked the position of the five watches respectively.

Sun Yi calculated in his mind that the five watches started at 19:12 on the first watch, 21:36 on the second watch, 00:00 on the third watch, 02:24 on the fourth watch, and 04:48 on the fifth watch.

Daoist Jia then solemnly suggested to Sun Yi, "The rules since ancient times, morning bells and dusk drums. The first is closed, and the fifth is open. The soldiers on night duty were divided into four shifts, one shift per shift. When they heard that there were soldiers on duty, the people's hearts were steady. Master, we have to have someone to change it. ”