Chapter 173: Observation and Collapse

Klein’s voice was soft.

But in the dead silence of the hall, it was like a clap of thunder.

‘What do you want to “see”?’

This sentence led people through a forbidden door that no one had dared to touch before.

The blood drained from Laurent’s face.

He stood stiffly on the stage, like a stone statue from which the soul had been ripped.

“What… what nonsense are you talking?”

His voice was dry and raspy, devoid of all strength.

“I’m not talking nonsense.”

Klein’s gaze was as calm as a bottomless pool of frigid water.

“I am simply stating a fact that you dare not admit.”

He turned and faced the thousands of mages in the audience, who were stunned into a daze by the excessive shock.

“Light has no fixed essence.”

“Its essence depends on how you ‘look’ at it.”

An uproar instantly flooded the entire hall.

“He’s mad! He’s completely mad!”

“Gods, what am I hearing? The essence of matter depends on the observer?”

“This is idealism! This is blasphemy!”

The goatee-ed academician on the stage, like a cat whose tail had been stepped on, jumped up again.

“Utter nonsense!”

“Klein! Take back your insane words! Otherwise, I will, in the name of the Royal Academy of Sciences, request the Magic Association to strip you of all your honors!”

“Master Laurent!”

The goatee turned to the desolate old man.

“Please give the order! Stop this absurd farce!”

Laurent slowly raised his head.

A glimmer of mad, final brilliance flashed in his eyes.

‘This must be the other party’s sophistry.’

‘It’s a final struggle.’

‘As long as I expose this lie, I still have a chance to turn the tables.’

Laurent’s voice was hoarse, but it carried a desperate determination.

“Lord Klein, since you claim that the nature of light depends on the observer,”

“then prove it to us!”

He pointed to the other side of the hall, where a set of experimental equipment had already been prepared.

A double-slit interference experiment apparatus.

This was the most classic experiment in optics.

Laurent’s words came out in a rush, as if he had grasped the last straw.

“It irrefutably proves the wave nature of light.”

“Now, I demand that you, in front of everyone, use this apparatus to make light display your so-called ‘particle nature’!”

“If you cannot, everything you have said today will become an eternal stain on your academic career!”

This was the final checkmate.

He was going to force Klein into a dead end.

All eyes focused on Klein.

Lia’s heart was in her throat.

She knew what Klein wanted to say.

But she hadn’t expected him to say it in such a direct, such a subversive way.

Klein met Laurent’s gaze, his face devoid of any emotion.

“Alright.”

He said only those two words.

Then, he walked straight towards the double-slit interferometer.

The apparatus was simple.

A monochromatic light source, a baffle with a pair of parallel slits, and a fluorescent screen to receive the image.

Klein activated the light source.

A slender beam of light shot towards the baffle.

Subsequently, on the fluorescent screen behind it, a series of alternating light and dark fringes clearly appeared.

An interference pattern.

The ironclad proof of wave nature.

“Do you see?”

Laurent’s voice rose again, filled with excitement.

“This is the nature of light! It is a wave! It will always be a wave!”

A faint cheer rose from the wave camp’s section.

Although their god had fallen, their god’s weapon still seemed sharp.

Klein ignored his clamor.

He quietly looked at the interference pattern.

“It’s beautiful, isn’t it?”

He said softly.

“This will be the beginning of a new era.”

He turned his head to look at Laurent.

“Now, Master, it is your turn.”

“What?”

Laurent was taken aback.

“Didn’t you want to ‘see’ the particles?”

Klein pointed to the two slits.

“It’s very simple.”

“I have a question right now. I really want to know which slit the photon actually went through.”

He sketched a model of a tiny detector in the air with magic.

“This is a miniature observation device built on a short-range induction field.”

“When any particle passes through its detection range, it will emit a faint signal.”

“Now, I need someone to place these two detectors behind each of the two slits, respectively.”

“To ensure the fairness of the experiment, to eliminate the possibility of me ‘cheating’,”

Klein’s gaze swept over the stage.

“I sincerely invite Master Laurent to perform this operation himself.”

He stared at Klein.

He wanted to see, in those calm blue eyes, even the slightest hint of a bluff.

But he failed.

In those eyes, there was only a bottomless confidence.

“Fine!”

Laurent gritted his teeth, forcing a single word out.

He refused to believe that the other party could pull a rabbit out of a hat.

Under the gaze of the entire hall, Laurent walked down from the stage.

He took the two miniature detectors from Klein’s hand.

He examined them carefully, again and again.

He confirmed that there were no deceptive magical traps on them.

Then, he personally placed the two detectors, carefully, directly behind the two slits.

“Is that alright?”

He looked up, his voice somewhat distorted with nervousness.

“It is.”

Klein took a step back and made a “please” gesture.

“Now, please restart the light source.”

“And then, please watch carefully.”

Laurent took a deep breath.

He reached out and pressed the activation rune.

The light beam shot out again.

This time, one of the two detectors placed behind the slits instantly lit up with a faint glow.

This meant that a “photon” had passed through this slit.

‘Success!’

A flash of delight crossed Laurent’s mind.

‘He saw it!’

‘He saw the particle!’

But, what did that prove?

It only proved that photons did exist.

But the interference fringes…

He shot his head up and looked at the fluorescent screen behind.

In that instant, all the expression on his face froze.

Time seemed to freeze at this moment.

In the hall, after a deathly silence, came a tsunami of gasps.

On the fluorescent screen.

That beautiful pattern of alternating light and dark interference fringes…

had vanished.

Completely and utterly vanished.

In its place…

were two bright vertical lines, corresponding exactly to the slits.

It was as if…

…countless tiny bullets had passed through the two slits, leaving their marks on the wall behind.

Wave nature.

At the very moment they tried to “see” the particle’s path…

had disappeared.

All that was left was irrefutable particle nature.

“N-no… impossible…”

Laurent staggered back two steps and fell to the ground.

He pointed at the two bright lines, then at Klein, his lips trembling, but he couldn’t form a complete sentence.

“This… is magic… an illusion!”

“Is it?”

Klein’s voice was calm and steady.

“Then please, remove those two detectors again.”

Laurent seemed to have been drained of all his strength.

An academician behind him rushed up and crudely ripped off the two detectors.

The “miracle,” or rather, the devil’s whisper, happened again.

The moment the detectors were removed, the two lonely bright lines on the fluorescent screen began to blur and spread.

Then, they wove together again.

That beautiful pattern of alternating light and dark interference fringes returned.

As if everything just now had been a hallucination.

The entire hall was silent.

Every single person felt as if their worldview had been thrown to the ground and repeatedly crushed.

“When you don’t look, it is a wave.”

“When you do look, it becomes a particle.”

“Light is like a shy maiden.”

“When you turn your head away, she dances gracefully, her skirt rippling into beautiful waves.”

“But when you try to see her steps clearly, she immediately gathers her skirt, stands tall and elegant, and becomes a quiet point.”

“What is this?”

“What in the world is this?”

“Now,”

Klein’s voice broke the suffocating silence.

“Do you see?”

“The nature of light is not what ‘it’ is.”

“But rather, how we choose to ‘look’ at it.”

“When we choose not to interfere with its path, to let it dance freely, it shows us the beauty of its wave-like superposition of possibilities.”

“And when we choose to spy with our instruments, to determine which path it actually took, its countless possibilities, at the very moment of our observation…”

“…collapse.”

“Collapse into this single, definite reality before our eyes.”

He paused, his gaze sweeping over the completely dazed Laurent.

“So, Master.”

“What you saw, was it the nature of light?”

“Or was it your obsession with wanting to see everything clearly?”