Chapter 538: Zhang 252: Turn His World Upside Down!! (8.8K)_2

An hour later.

Night had completely fallen.

Da da da—

A Student Union officer walked briskly into the tent, the cowhide boots making crisp contact sounds with the ground.

He whispered a few words with his colleague and then said to Xu Yun,

"Classmate Luo Feng, the time and equipment are just about ready. Please follow me."

Xu Yun nodded, followed him out of the small tent, and arrived at an open space.

At this time, the open space, except for the central area, was already surrounded by a dense crowd of people:

Among them were Wheat and Aveline—one was the second bursary student at Trinity College, known as 'Little Niu the Second,' and the other was simply the only direct descendant of the Aesku Clan. It was quite normal for them to be here.

There was also Angus Roman,

Frederick Agar Ellis, who saw Thomson as a rival,

The future composer Max Christian Friedrich Bruch, and so on.

These were all selected student representatives, witnessing the entire process on behalf of the student body.

The rest included leaders and professors such as Prince Albert, William Whewell, Faraday, Stokes, and others present in full.

At the center where they gathered were some prepared equipment.

The equipment Xu Yun required was actually very simple, consisting of four modules distributed in four different areas:

Firstly, there was Xu Yun's station.

Here was a table, a flashlight fixed on the table, a silver-plated lens, and a telescope.

The second area was directly to his left...about twenty meters at the nine o'clock direction.

There stood an imaging board.

The third area was at the ten-thirty direction in front of him.

There was a rotating mirror constantly spinning, and the line connecting the imaging board was perpendicular to the line connecting the operation table with the imaging board.

The rotating mirror, imaging board, and operation table formed an "L" shape.

As for the last module, it was five kilometers away, where a concave mirror was guarded by a few teaching assistants from Trinity College.

The line connecting the concave mirror and the rotating mirror was perpendicular to the line connecting the rotating mirror and the imaging board, that is, a line pulled horizontally from the top of the 'L' on the left side.

Seeing up to here.

Presumably, some clever students would have guessed it by now.

That's right.

What Xu Yun was preparing to use this time was precisely the rotating mirror light measurement method invented by Foucault!

Previously mentioned.

The speed of light value calculated by Little Niu and Huygens was regarded as authoritative for a long period.

This situation lasted until 1849.

At that time, a scientist named Armand Fizeau, inspired by Arago, devised a precise experiment that broke this 'authority':

He designed a gear and placed it between the light source and the mirror.

When the gear was not moving, the light emitted from the source passed through the gaps in the gear.

After being reflected by the mirror, it would pass through the same gap to be observed by the observer.

When the gear started to rotate and reached a certain speed, the light would just miss the original gap upon return.

The light would hit the gear and could not be observed.

If the gear's speed continued to increase, the light would pass through the next gap and be reflected back again.

The entire process needed no consideration for human visual reaction speed, just knowing the number of teeth on the gear, the speed, and the distance between the observer and the mirror to calculate the speed of light.

However, due to technical limitations, there were still some issues with this method.

After all, it involved blocking light with a gear, resulting in about a 5% deviation in the final measured light speed.

Therefore, the later Foucault—who was the one who came up with the Foucault Pendulum—thought for a bit and replaced the gear with a rotating mirror.

He also made some optimization in the process, locking the precision at 289,000 kilometers.

By the time Michelson came along, he replaced it with an eight-sided mirror, further increasing the precision.

Xu Yun once discovered while researching in the library.

In the dungeon, due to the changes in the world line, the inspiration Armand Fizeau got from Arago didn't include the idea of light measurement. After graduating from college, he plunged into the expanse of wave theory.

As a natural consequence.

Armand Fizeau didn't complete his gear light measurement experiment a year ago.

If the gear light measurement hadn't happened yet, there's no mention of Foucault:

Foucault finished his rotating mirror light measurement about a year and a half later. Foucault's inspiration came directly from Fizeau's paper.

Thus, at the library, Xu Yun had already prepared a plan, ready to use light speed measurement as an entry point.

Just didn't expect the opportunity to come so quickly.

Of course.

Perhaps some students would ask:

Isn't it true that Michelson's precision is higher, so why not use the eight-sided mirror?

The reason is simple, it boils down to just two words:

Venue.

Don't be fooled by the seeming simplicity of Fizeau's light measurement steps, the indicated distances seem quite short.

In fact, due to the exceedingly fast light speed, the gear couldn't block the light at all, and Fizeau's experiment initially failed.

He could only keep extending the experimental distance and teeth number, and increased the gear's rotation speed, hoping to block the reflected light.

In the later days online, illustrations of Fizeau's light measurement could be found, making the distance seem short, but the actual optical path in practice reached 8,633 meters.

As for the eight-sided mirror…

Sorry.

22 miles, bring a couple more and you can reach London.

Therefore, after some considerable thought.

Xu Yun eventually chose the rotating mirror light measurement method invented by Foucault.