Chapter 533: Zhang 251: Chaos, Chaos, the Entire 19th Century is in Turmoil! (7.4K)

Light.

A word so simple it can hardly be simpler.

A phenomenon so common it couldn’t be more common.

Yet it’s a strand that runs through human scientific history, a mystery that remains elusive even into the 22nd century.

Speaking of light, later generations often first think of wave-particle duality.

Then comes Ultraman Tiga, followed by terms like interference and diffraction of light.

Actually.

Humankind’s contemplation about the nature of light started to show hints even before the Common Era.

For example, in ancient East.

People believed the Sun was an embodiment of Divine Spirit, for instance, Xi He, Sun Lord, East Lord, and the Golden Crow shot down by Hou Yi, among others.

And in ancient West, the prevailing idea initially was Empedocles’ view.

He believed the world was composed of four elements: water, fire, air, and earth, and human eyes were ignited by the goddess Aphrodite, with light also belonging to fire.

After Empedocles came Plato, who believed there were three different kinds of light.

Originating from the eyes, the observed objects, and the light source itself.

As for vision, it was the result of the interplay of these three.

Following Plato, a slew of idealistic thoughts appeared, like those of Lucretius and Al Hassan.

And where there’s abundant thought, naturally some would attempt to validate truth through practical means.

It’s worth mentioning.

The first documented scientific research on the propagation of light wasn’t from the West, but authored by ancient Huaxia sages in the "Mo Jing."

The "Mo Jing," completed around the 14th year of King An of Zhou—Year of Gui Si, 388 BCE—contains a famous research case.

This case comes from "Mozi: Explaining Downward Chapter 43":

[A shadow, two lights sandwiching one light, one light is the shadow. The person in the shadow light looks to shine like shooting, the lower person is in the high place, the higher person is in the low place. The lower light is blocked by the foot, thus the shadow forms above; The upper light is blocked by the head, thus the shadow forms below. There’s depth and proximity with respect to light, hence the shadow is within the light-well.]

A shadow refers to an object’s image.

Thus, this passage means:

Light travels in straight lines like shooting arrows.

The lower part of the human body blocks the incoming light, going through a small aperture, forming a shadow in the upper part.

The upper part of the human body blocks the incoming light, going through a small aperture, forming a shadow in the lower part, thus forming an inverted image.

This describes the macroscopic properties of light uniformly and is the first scientific explanation for light’s linear propagation.

Besides.

The Mo School also understood another concept—light converges before a lens or a concave mirror:

"There’s depth and proximity with respect to light, hence the shadow is within the light-well."

內 means 纳, which translates to gathering at a point.

In the "Mo Jing," focal points are often referred to as "正" or "内," suggesting the Mo School had already studied the principle of light convergence.

Yet unfortunately.

Due to the incomplete scientific system in ancient Huaxia, points of brilliance in subsequent optical development were scarce.

Of course.

This doesn’t mean no one in Huaxia researched optics, but after the "Mo Jing," there’s lack of a chronologically structured record of optical research.

Meanwhile, in the West, Euclid studied light’s reflection in his book "Reflection Optics," with Ptolemy providing insights into the macroscopic properties of light.

Later, researchers like Kepler appeared.

By 1621.

Netherlands physicist Snell summarized the law of refraction of light.

Around the same time.

Descartes proposed in one of the three appendices of his "Methodology," titled "Refraction Optics," such possibilities:

Light is a form of pressure that travels within medium, and ether exists in the world.

This event marked a critical point, a source of all evil in modern optics.

Nowadays.

Since then.

Optics, akin to Sword Sect and Qi Sect, split into two distinct schools of thought.

The wave theory emerged first.

Today, the wave theory is generally attributed to Huygens, but actually, the first to find evidence of wave theory was an Italian mathematician.

This person was named Francesco Grimaldi.

He conducted an experiment at that time:

He allowed a beam of light to pass through two small holes to find a screen in a dark room, observing a pattern of light and dark stripes at the edge of the projection.

Grimaldi thus suggested light might be a wave similar to water waves, and this was the earliest wave theory of light.

Unfortunately, the mathematician’s limited ability prevented further in-depth research, ultimately leading Huygens to first comprehensively define light:

Light is not a material particle but a wave produced by the vibration of medium.

As for the medium through which light propagates, it’s the ’ether’ reignited by Descartes.

Later, Hook took the lead, followed by Little Niu proposing the particle theory.

It’s worth noting.

Even though Little Niu’s particle theory and wave theory were mortal enemies, Little Niu didn’t deny the ’ether.’

In Little Niu’s original insistence on absolute space-time perspective, ether was the representation of absolute motion.

Even Wheat later couldn’t escape the circle, introducing the concept of ether in electromagnetism and attempting to deduce the expression equation of ether in inertial systems in his later years.

The result, in 1887.

United Kingdom physicist Michelson and chemist Morey refuted the existence of ether with the "ether drift" experiment, sending shockwaves through the scientific community for a long time—one of the two dark clouds mentioned earlier.

Classical physics relied on ether to develop many correct results, but suddenly it found the foundation of these derivations was wrong, ain’t it uncanny?