| Scenario | Wheels (billions) | Doors (billions) | Winner |
|---|---|---|---|
| Narrow human-made (vehicles, bikes, “real” doors) | ~11.4 | ~54 | Doors |
| Creative human-made (toys, chairs, cabinets, appliances) | ~51.9 | ~120 | Doors |
| + Biology: heart valves as doors | ~42 | ~283 | Doors |
| Strictly shape+function wheels/doors (modern tech + biology, no flagella) | see below | see below | Depends on inclusions |
Interpretation: With ordinary human-made stuff (including toys) and cabinet doors, doors win. Adding shape-true rotary elements (HDD platters, discs, turbines, bearings) boosts wheels; adding shape-true biological gates (ion channels, nuclear pores, stomata) boosts doors dramatically.
- HDD/SSD moving-media: Hard disk platters (circular, spin to read/write). SSDs are solid-state (no wheel).
- Optical media: CDs/DVDs/Blu-rays (discs that spin in use).
- Turbine rotors: Jet engines, wind turbines, hydro turbines (circular rotors, continuous rotation under load).
- Ball bearings: Each ball is a tiny wheel; bearing races (rings) are circular, roll/rotate to reduce friction.
- Pulleys & gears: Circular, rotational transmission of force.
- Rotary encoders/flywheels: Circular, rotational sensing/energy storage.
- Biology: ATP synthase rotor: A bona fide molecular rotary machine (F₀F₁-ATP synthase) that spins to synthesize ATP.
- Building doors: Interior/exterior doors, cabinet doors, appliance doors.
- Industrial valves: Butterfly, gate, globe, ball valves (gating fluid flow). Ball valves have rotating spherical “plugs” with circular ports (door-like gate function).
- Camera shutters: Mechanical blades that open/close.
- Circuit breakers/switch flaps: Mechanical open/close of electrical path.
- Biology: ion channels: Protein gates in cell membranes (ligand/voltage/mechanical gated).
- Biology: nuclear pore complexes: Massive gated pores for nucleus-cytoplasm transport.
- Biology: stomata: Adjustable leaf openings; paired guard cells act as a door.
- Biology: heart valves: One-way flaps (mitral, tricuspid, aortic, pulmonary) behaving as doors.
These additions build on the earlier human-made estimates. They are Fermi-style and intentionally rounded; the point is scale, not exactness.
| Item | Very rough stock/flow assumption | Wheel-equivalent count |
|---|---|---|
| Hard disk platters | Cumulative HDDs shipped on the order of 8–12B; 1–5 platters/drive typical | 8–40B platters |
| Optical discs | CDs+DVDs+Blu-rays cumulative likely O(10¹¹–10¹²) | 100–1000B discs |
| Ball bearings (balls) | Global production likely O(10¹¹) balls/year; multi-decade stock large | 100s of billions–trillions balls |
| Pulleys/gears | Ubiquitous in machines; no good global registry | “Many 10⁹–10¹²” elements |
| Turbine rotors | Wind ( |
Millions of rotors (10⁶–10⁷) |
| Rotary encoders | Robotics/automation/consumer devices | 10⁹–10¹⁰ discs |
| ATP synthase rotors (biology) | 10³–10⁵ per cell typical order; 10²⁸–10³⁰ total cells on Earth → astronomical | >10³¹ rotors (order-of-mag) |
Implication: If ATP synthase is admitted (shape-true rotary), “wheels” at the molecular scale overwhelmingly dominate counts, far beyond human-made totals.
| Item | Very rough stock/flow assumption | Door-equivalent count |
|---|---|---|
| Industrial fluid valves | Water/oil/gas/chemical/power sectors globally; likely O(10⁹–10¹⁰) installed | Billions–tens of billions |
| Camera shutters | Billions of cameras shipped historically | Billions |
| Circuit breakers/switches | Multiple per electrical panel/device; installed base potentially >10¹¹ | 10s–100s of billions |
| Nuclear pore complexes (biology) | ~2k–5k pores/nucleus; nucleated cells on Earth → astronomical | >10³¹ (order-of-mag) |
| Ion channels (biology) | 10⁶+ channels per neuron; enormous across all cells | >>10³¹ (order-of-mag) |
| Stomata (biology) | Densities ~10²–10³ per mm²; global foliage area huge | >10²⁴ (very rough) |
| Heart valves (biology) | ~4 per mammal/bird; prior calc ~1.6×10¹¹ for humans+livestock+chickens | ~1.6×10¹¹ |
Implication: With biological gates (ion channels, nuclear pores, stomata) admitted, “doors” also scale to astronomical counts. The winner depends on which microscopic categories you’re comfortable including.
- Human-made macro world: counting toys + cabinet doors → doors tend to win.
- Add modern tech discs/platters/bearings: wheels gain a lot, but still within 10¹¹–10¹² scale.
- Include biology, shape-true: both sides jump to astronomical scales (≥10³¹). The question becomes philosophical.
- Definitional clarity matters: agreeing on what “counts” (e.g., ATP synthase, ion channels) determines the outcome.
- Start from earlier baselines (vehicles, bikes, toys, furniture, cabinets, appliances, non-residential doors).
- Add wheel-like tech (discs/platters/bearings/pulleys/encoders/turbines) with conservative order-of-magnitude ranges.
- Add door-like tech (valves/shutters/breakers) with conservative ranges.
- Add biological wheel-like (ATP synthase) and door-like (ion channels, nuclear pores, stomata, heart valves) using textbook-level typical densities.
- Prefer stock (installed base) to flow (annual shipments) when reasoning about what exists now.
These are representative, high-level sources suitable for anchoring the orders of magnitude. If you want, we can replace any with more formal primary literature.
- HDD shipments & platters: Industry shipment trackers (IDC, TrendFocus); vendor whitepapers (Seagate, WD) describing typical platter counts.
- Optical disc volumes: IFPI reports, RIAA historical shipment data for CDs/DVDs/Blu-rays.
- Bearings: Industry associations (World Bearing Association), annual reports (SKF, NSK, NTN) for production units.
- Turbines: Global Wind Energy Council (GWEC), IRENA for wind/hydro counts; FAA/EASA and OEM data for engine fleets; turbine stage counts from OEM tech briefs.
- Pulleys/gears/encoders: Robotics and industrial automation vendor catalogs; IEC/ISO market reports.
- ATP synthase: Biochemistry textbooks/reviews on F₀F₁-ATP synthase structure and rotary mechanism.
- Ion channels: Neuroscience/physiology texts; ligand/voltage-gated channel overviews.
- Nuclear pore complexes: Reviews noting ~2,000–5,000 pores per nucleus in vertebrate cells.
- Stomata: Plant physiology texts on stomatal density and global leaf area estimates.
- Heart valves: Human anatomy references; FAO livestock statistics for animal counts.
- Swap in specific, cited numeric anchors (HDD cumulative units, CDs/DVDs cumulative, bearings production, GWEC fleet sizes, ATP synthase per cell, NPC per nucleus, stomatal densities + global leaf area) and recompute ranges.
- Separate stock vs. flow and active vs. retired assets (e.g., discs in landfill vs. in use) depending on your definition of “in the world.”
- Provide scenario toggles (include/exclude microscopic biology; include/exclude retired tech) and show which side wins under each.