A reading series for physics-loving high-school and undergraduate students

Black Holes That Click

A black hole is the diagonal of physics' "cube" ── the one laboratory where c, ℏ and G all act at once. There, every piece of physics turns into a "dimensionless ratio of information (bits)." The horizon is a blackboard carrying one bit per Planck area, and there sits the doorway into an unfinished quantum gravity. With information and ratios alone, we read the farthest reaches of the universe.

6 main episodes · complete + 2 bonus Each episode: everyday words → one ratio → the reveal → exercises With interactive figures / print- and PDF-ready
One sentence is the backbone ── in a black hole, all of physics becomes a "dimensionless ratio of information."
The horizon is the surface where the escape velocity reaches c (Episode 1). Its entropy is S=A/(4ℓ_P²) ── the area divided by the Planck area, a bit count, and the first equation where c, ℏ and G all gather in a single line (Episode 2). The temperature goes as ∝1/M, so lighter is hotter and it evaporates (Episode 3), and the interior is the fastest computer (Episode 4). Information is written not in the volume but on the surface (holography, Episode 5), and the question of whether evaporation destroys information ── the information paradox ── is the head-on collision of ℏ and G, the heart of quantum gravity (Episode 6). The dimensionful c, ℏ and G are stage machinery; what remains is nothing but ratios of bits.
Download all published files at once The button below bundles the published episodes into a single ZIP (as more episodes are released, more will be included).
Main series
Episode 1interactive figure
The Horizon — the surface information can't leave

The radius where the escape velocity reaches the speed of light c is the event horizon (R_s=2GM/c²). Seen from outside, time freezes there (a frozen star), while the one falling in slips right through ── "stopping" depends on your point of view. A one-way membrane for information.R_s = 2GM/c²

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Episode 2interactive figure
Entropy = Bit Count — the equation where four constants meet

S=k_B c³A/(4Gℏ)＝A/(4ℓ_P²). The entropy is just a bit count ── the horizon's area divided by the Planck area. The one equation where all the constants of physics gather in a single line. And its skeleton can be derived from "ratios" alone.S/k_B = A/(4ℓ_P²)

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Episode 3interactive figure
Hawking Temperature & Evaporation — lighter is hotter

The horizon has a temperature: T∝1/M. The lighter the black hole, the hotter it is, and with its negative heat capacity, heating it makes it waste away until it finally evaporates (lifetime ∝M³). It falls out from "the energy of the largest photon that fits in = the temperature," by a ratio.T = ℏc³/(8πGMk_B)

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Episode 4interactive figure
The Fastest Computer — scrambler and queue

A black hole is nature's fastest and densest computer (Lloyd's ultimate laptop). The speed at which it scrambles information is the physical upper limit (the chaos bound). Information that falls in is stacked in the surface's queue at maximal mixing, and returns in the radiation.λ ≤ 2πk_BT/ℏ

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Episode 5interactive figure
The Holographic Principle — the world is written on the surface

The information you can pack into a region is set not by its volume but by its surface area (in Planck units) ── the Bekenstein bound. Three-dimensional contents are encoded on a two-dimensional surface ── AdS/CFT is a concrete example (though our universe is not AdS).S ≤ A/(4ℓ_P²)

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Episode 6interactive figureFinale
The Information Paradox & Quantum Gravity — the cube's diagonal

Does evaporation destroy information (unitarity vs. Hawking)? This is the head-on collision of ℏ and G ── the heart of quantum gravity. The recent progress on the Page curve and islands, information → gravity (Jacobson), and the one last corner that remains.the corner of c, ℏ, G

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Bonus
Bonusinteractive figure
Deriving the 1/4 by Hand — you only import one thing: 2π

Actually build up the 1/4 coefficient from Episode 2 by hand: R_s → surface gravity → temperature → first law → area, and out comes 1/4 = 4π/16π. The only thing ratios can't give you is the 2π in step ③ (the once-around of the imaginary-time loop) ── and we break even that down to "one full turn is 2π".1/4 = 4π ÷ 16π

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Bonus · closinginteractive figureseries complete
Is the Universe a Computer?

The big question after reading black holes through information. The constants as a hardware spec (c = bandwidth · ℏ = operation cost · area = memory), the universe's RAM ≈ 10¹²² bits (set by Λ), and the end of computation = heat death. We close on the honest line: "obeys computational limits" is established, "is a computer" is speculation.the universe's RAM ≈ 1/(Λℓ_P²)

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