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Part 2 · Episode 12 B1-B2

It Can’t Be Real

📐 can't/cannot (impossibility/negative deduction)

Wilhelm Röntgen · 1895: Röntgen's X-ray discovery 📖 6 min read

Episode 12: It Can’t Be Real

can’t: impossibility — Wilhelm Röntgen, 1895 (B1-B2)

Grammar Box

Meaning: “Can’t” or “cannot” expresses strong logical certainty that something is impossible or untrue, the negative equivalent of “must” for deduction.

Form: can’t/cannot + base verb; can’t/cannot be + adjective/noun

Example 1: “That can’t be John—he’s in Paris this week.” (logical impossibility based on facts)

Example 2: “She can’t be hungry. She just ate an hour ago.” (deduction from recent event)

Common mistake: Wrong: “It can’t is true.” Better: “It can’t be true.” (can’t + base verb, not can’t + is)

The Challenge

Luna received an email claiming she had won a million dollars from a contest she never entered. “This must be real!” she said excitedly. Professor Wisdom appeared, shaking his head gently. “Based on what you know, is that logical? Or does the evidence point to impossibility?” Luna reread the email, noticing the poor grammar and suspicious link. The watch pulsed with an intense glow, taking them to a German laboratory where impossibility was about to become reality.

The Journey

Wilhelm Röntgen sat alone in his darkened laboratory at the University of Würzburg on November 8, 1895, staring in disbelief at something that shouldn’t exist. The fifty-year-old physicist had been experimenting with cathode ray tubes when he noticed a strange glow on a nearby screen coated with barium platinocyanide. This glow appeared even when the tube was completely covered with black cardboard, which should have blocked all known forms of light.

“This can’t be happening,” Röntgen muttered to himself in German, moving the screen farther away. The glow persisted. He placed various objects between the tube and the screen—a book, pieces of metal, his own hand. Most materials barely dimmed the glow, but when he held up his hand, he saw something that made his breath catch: the bones of his fingers clearly visible as dark shadows surrounded by the hazy outline of his flesh.

The scientific community’s initial reaction, when Röntgen finally published his findings weeks later, was predictable skepticism. “This can’t be real,” many scientists insisted. “Light cannot pass through solid objects. This must be some experimental error or trick.” Some accused Röntgen of fraud, others of misinterpreting his results. The idea that invisible rays could penetrate flesh and wood but not bone or metal contradicted everything they knew about light and matter.

Röntgen, trained in rigorous scientific method, had anticipated this reaction. He spent seven weeks alone in his laboratory, repeating the experiments dozens of times, testing every possible explanation for what he was seeing. Each time, the evidence forced him to abandon his own doubts. “I thought this can’t be possible,” he later told his wife Bertha. “But the facts kept proving it must be real.”

The smell of ozone from electrical discharge filled the laboratory, mixed with the chemical scent of the photographic materials Röntgen used to capture images of his discovery. His wife became the first person to see an X-ray photograph when he asked her to place her hand on a photographic plate. When she saw the image of her bones with her wedding ring clearly visible, she gasped, “This can’t be my hand!” Yet it was.

The Deep Dive

“Can’t” or “cannot” expresses logical impossibility or strong certainty that something is false, based on evidence or reasoning. It’s the negative counterpart to “must” for deduction: where “must” says something is certainly true, “can’t” says something is certainly false. “He can’t be the thief—he was with me all evening” uses evidence to eliminate possibility, just as firmly as “He must be innocent” would assert it.

This deductive “can’t” differs from “can’t” meaning inability or prohibition. “I can’t swim” describes lack of ability, “You can’t park here” states a rule, but “That can’t be right” expresses logical impossibility based on reasoning. Context reveals which meaning applies, though deductive “can’t” typically appears in statements evaluating truth or possibility rather than describing abilities or rules.

The strength of “can’t” matches the strength of “must”—both express near-certainty (95%+ confidence) based on logic and evidence. For weaker negative deductions, use “might not” or “may not”: “She might not be home” (uncertain) versus “She can’t be home—I have her only key” (logically impossible). Never use “mustn’t” for negative deduction; it only expresses prohibition or strong advice: “You mustn’t tell anyone” means don’t tell, not “it’s impossible that you’ll tell.”

More Examples

History: “The Vikings can’t have had advanced technology—archaeological evidence shows otherwise.” (impossibility based on facts)

Science: “This species can’t survive in saltwater—all tests show it requires freshwater.” (conclusion from experimental evidence)

Everyday: “That can’t be the right address. This is a park, not an office building.” (logical impossibility from observation)

Formal: “The data cannot support that conclusion given the sample size and methodology.” (professional impossibility statement)

Informal: “You can’t be serious! There’s no way that happened.” (strong disbelief based on logic)

Contrast: “I can’t attend the meeting” (unable to) vs “That can’t be the meeting time—the calendar shows Friday” (logically impossible)

Practice & Reflection

Exercises:

  1. Fill in the blank: She __ (can’t/might not) be the director—she only started working here last week.

  2. Correct the mistake: “That cannot is the correct answer based on the evidence.”

  3. Choose and explain: Which shows logical impossibility?
    a) “I can’t solve this problem.”
    b) “This can’t be the solution—it doesn’t fit the equation.”

  4. Rewrite: Use “can’t” for impossibility: “I’m certain this isn’t the right building because the address doesn’t match.”

  5. Compare: Explain: “You can’t smoke here” vs “You can’t be smoking—I don’t smell anything.”

  6. Your reflection: Think of something you concluded was impossible based on evidence. Write about it using “can’t.”

Answer Key:
1. can’t (logical impossibility—not enough time to become director)
2. That cannot be the correct answer (cannot + base verb “be”)
3. (b) — shows logical impossibility from evidence; (a) shows inability
4. This can’t be the right building—the address doesn’t match (impossibility from evidence)
5. First is prohibition/rule; second is deduction (impossibility of smoking without smell)
6. Check: Does “can’t + base verb” express impossibility based on logical reasoning?

The Lesson

Luna deleted the suspicious email with new confidence. “This can’t be real,” she told Professor Wisdom. “I never entered a contest, and real companies don’t send emails full of errors.” The Professor smiled with approval. “Exactly. Röntgen’s colleagues said ‘this can’t be real’ because it contradicted their knowledge, but evidence proved them wrong. You’re saying ‘this can’t be real’ because evidence proves you right. Both use the same grammar, but your logic is sound. That’s the power of ‘can’t’—it expresses certainty about impossibility when facts support your conclusion.”