"The sun and the moon are bright."

Zhu Gaoxu's thinking seemed to be extremely active today, and he immediately asked a strange question.

"Mr. Jiang just said that there is a law of gravitation, that is, the greater the mass of an object, the greater the gravitational force between them; The farther apart the objects, the less gravitational pull there is between them. ”

"Exactly." Jiang Xinghuo affirmed.

"Then Mr. Jiang, if gravity is true and the sun is the center, then the sun is so far away from our earth, it can emit gravity and pull our earth to rotate, so how massive does the sun have? Or rather, how big is the sun? Zhu Gaoxu asked curiously.

Hearing this question, Old Man Zhuo also looked at Jiang Xinghuo.

Obviously, Old Man Zhuo was also very concerned about this issue.

After all, everyone has watched the sun hang there since ancient times, but no one can say exactly how big the sun is, whether it is bigger or smaller than the earth.

And if you follow the theory of gravity, Old Man Zhuo deduced an obvious conclusion.

That is, the sun is the center of the universe, or the sun is the center of the earth and celestial bodies such as gold, wood, water, fire, and earth, so the mass or weight of the sun must be extremely large.

Otherwise, it is obviously an extremely unreliable thing for a small sun to attract a bunch of large celestial bodies.

But Old Man Zhuo didn't have much hope for this problem.

Old man Zhuo didn't have hope that Jiang Xinghuo would answer this question, but he didn't have hope at all if there was an answer to this question.

The reason is also very simple. Guo Shoujing used manpower to measure the area of the earth, and in Zhuo's opinion, this is already the limit of astronomy and geography.

After all, the earth area does exist, but it is not easy to measure, it does not mean that it cannot be measured.

But the question is, how to measure the mass, area, and distance of the sun?

Do you fly over the sun and get a ruler to measure?

Apparently impossible.

Therefore, Old Man Zhuo really didn't expect Jiang Xinghuo, an amazingly talented descendant, to give any answer.

But

But

Jiang Xinghuo closed his lips one by one.

"Easy to do."

——————

"Is this wall broken?"

Zhu Gaochi turned his head in disbelief and asked the two officials.

The two little officials, Guo Jin and the chai cart, shook their heads in unison.

It is an indisputable fact that the eavesdropping sound wall is not broken at the moment, and the sound is coming very clearly.

"The wall isn't broken, but the ears are broken?"

Zhu Gaochi stretched out his fingers again and tried to pluck out his ears and eyes, but his short and thick little thumb was obviously unable to do this.

Zhu Gaochi finally reluctantly believed that the wall was not broken, and the ears were not broken.

Jiang Xinghuo actually said that he could measure the mass and size of the sun!

In Zhu Gaochi's view, this is simply listening to the myth of Houyi shooting the sun and Jingwei reclamation.

Zhu Yuanzhang only forbade people to learn such things as astronomy, but in the Qin Heavenly Prison, as well as the princes and grandsons wanted to learn, there was no prohibition.

After all, in a sense, astronomy is closely related to imperial power, and there is nothing wrong with the royal family.

And Zhu Gaochi has also learned some astronomical knowledge since he was a child, and there are also some astronomy-related books in the Yanwang Mansion (the former Yuan Dynasty Dadu Palace), Zhu Gaochi believes that in astronomy, he still has some skills.

But even so, the so-called measurement of the trajectory of the sun's motion and the like only exist in some notes, and the traditional Chinese astronomical method still cannot draw the trajectory of the sun's motion.

However, if we can't even draw the trajectory of the sun, we can only rely on the vague model of the armillary sphere and the traditional Chinese astronomy, which has accumulated a large amount of data accumulated for thousands of years and calculated by algebraic methods, so naturally we have no ability to measure the distance between the earth and the sun, as well as the mass and surface area of the sun.

Of course, it's not that Chinese astronomy is not good, but in the times, no one can measure it.

The most basic astronomical telescope has not been pointed out, how can you observe it? How to measure?

Therefore, Zhu Gaochi did not believe this.

Moreover, Zhu Gaochi felt that if he really wanted to calculate the position and size of the sun, he would definitely need some specific opportunities first, and he would need to cooperate with the time to calculate it fuzzily.

Now that Jiang Xinghuo said that he could measure the position and size of the sun, Zhu Gaochi didn't believe it at all.

But...... Jiang Xinghuo, who came from the other side of the wall, spoke faster than usual, and his mood fluctuations when he spoke also became a little strong, as if he was stimulated by some kind of stimulation, so that Zhu Gaochi did not dare to despise the possibility of Jiang Xinghuo's words, and he did not dare to speak casually to interrupt his listening thoughts.

——————

"How do you measure the sun?"

Jiang Xinghuo asked himself: "The first step, of course, is the twisted scale experiment just mentioned, first of all, we have to measure the constant of gravitation. ”

"This experiment is very easy to do, as long as you insist on repeating the test to eliminate interference, anyone with qualified mathematical knowledge can calculate the gravitational constant by themselves."

"As for the second step." Jiang Xinghuo paused and continued, "It is to measure the mass of the earth through the gravitational constant through an experiment of throwing balls from a tower. ”

"Slow down, little friend."

Old man Zhuo hurriedly interrupted Jiang Xinghuo's speech.

Jiang Xinghuo's from the first step to the second step is like a person taking a piece of iron ore, and then "snapping", conjuring up a steel knife, and then telling you - "Look, just do it and that's it." ”

Jiang Xinghuo stopped speaking as he said.

"I wonder what the old gentleman has to say?"

"I can't talk about advice." Zhuo Jing's old eyes were a little confused, "Twist the scales. The experiment can calculate the gravitational constant, and the old man can still understand it, but why can the tower throw a ball and calculate the mass of the earth? ”

Jiang Xinghuo silently continued to write on the ground with small branches.

Earth's mass = (gravity * Earth's radius to the second power) / gravitational constant * Mass of the tower iron ball experimental object

Jiang Xinghuo wrote another line of small print remarks: * means multiplication.

After writing the formula for calculating the mass of the earth, Jiang Xinghuo looked up and asked.

"Do we know the radius of the earth?"

This question sounds a bit outrageous, and Old Man Zhuo really knows the answer.

"Guo Shoujing has measured, 120,000 miles."

Jiang Xinghuo continued to ask: "After doing the twist scale experiment, do you know the gravitational constant?" ”

"Yes."

Old man Zhuo was still a little puzzled: "What does that have to do with the quality of the tower iron ball experimental object?" ”

"Of course it does."

Jiang Xinghuo explained: "Gravity, that is, the embodiment of gravity on the earth, can this be understood? ”

The three of them nodded in unison, this is another way of saying that gravitational force is gravity on the earth, of course it can be understood.

"How do you measure gravity? It doesn't matter if you don't know, I'll tell you, you can see and judge whether what I said makes sense. Jiang Xinghuo said.

Jiang Xinghuo wrote on the ground.

Gravity = Experimental object * Acceleration of falling object

This time, Zhu Gaoxu was numb, but Zheng He and Zhuo Jing, two people who are quite accomplished in this area, understood in an instant.

Zhuo Jing even picked up a small stone, directly raised his arm and put it on a high place, and then let the stone fall.

This was repeated four or five times, and even Zhu Gaoxu had a good taste.

The principle, in fact, is a little clear.

Zhu Gaoxu said suddenly: "This thing, to put it bluntly, is it not the same as the strength of the bow and arrow, and the torque of the trebuchet?" ”

"Almost." Zheng He stiffly maintained the state of stroking his beard, and his arms were numb, for fear that his long hair would fall off.

"So, as long as you do the torsion scale experiment and the tower throwing ball experiment, then don't you have the gravity, the radius of the earth, the gravitational constant, and the mass of the object needed to calculate the mass of the earth?"

Jiang Xinghuo stretched out his finger and pointed to the formula on the ground.

"Bring it in, and the mass of the earth will come out."

"Little friend, this is still not right, right?"

Old man Zhuo patiently waited for Jiang Xinghuo to finish speaking this time, and asked again: "How do you know this formula to be able to calculate the mass of the earth?" In other words, how do you prove that the formula is correct? If the formula is not correct, then even if the numbers in it can be calculated, it does not prove to be correct. ”

Jiang Xinghuo chuckled.

Subsequently, Jiang Xinghuo continued to write a formula with twigs on the sandy earth.

Gravity = gravitational constant * [(mass of the experimental object * mass of the earth) / quadratic of the radius of the earth]

"Does this formula make sense?" Jiang Xinghuo asked.

The three of them pondered for a moment on the formula, combined with their previous understanding of archery and stone throwing, but after discussing for a while, they understood, and it seemed that there was no problem.

Next, Jiang Xinghuo drew a few lines between the two formulas as if by magic, and matched all the numbers one by one.

Wait for Jiang Xinghuo to finish drawing the corresponding line.

Under the tree, several exclamations suddenly sounded!

"That's the case?"

"The old man understands! The old man understands! ”

"I know Mr. Jiang won't be wrong."

Don't look at Old Man Zhuo's age, his brain is spinning fast, first combined with Jiang Xinghuo's previous words, and then remembering Jiang Xinghuo's answer to his steps to calculate the sun, he immediately understood.

"So, the next step should be to measure the distance between the sun and our earth!"

"Exactly."

Jiang Xinghuo nodded and said affirmatively: "You only need to calculate the distance between the sun and the earth to get the area of the sun, and you only need to get the distance and area of the sun, and then combine the rotation period (revolution) of the sun and the earth, you can complete the simple matter of measuring the sun." ”

The secret room next door.

The eldest prince Zhu Gaochi and the two junior officials Guo Jin and the diesel car were already completely brain down.

You told me that measuring the sun is a very simple thing?

If someone had dared to say that a day ago, the result would have been a big mouth.

But right now, Zhu Gaochi involuntarily had a thought.

If you follow the steps that Mr. Jiang said.

It seems that it is not difficult to measure the sun?

(End of chapter)