The Pendulum and the Dying Sun
Pendulums, exponential decay, and extraterrestrial life
Spoiler warning: this page discusses the novel's plot up to this chapter. It doesn't quote passages from the book.
Grace builds a pendulum to determine if he's in a centrifuge or a ship. Meanwhile, flashbacks reveal the Sun is losing energy exponentially, and a probe sent to Venus discovers something that will change everything: the dots are moving. They're microbes.
The pendulum as a fake-gravity detector
Grace builds a pendulum and hangs it at two different heights. He counts 346 cycles in 10 minutes at both heights. If it were a centrifuge, the results would differ.
The science behind it
A simple pendulum swings with a period that depends ONLY on the string length and local gravity. It doesn't depend on the object's weight or how hard you push it. Formula: T = 2π√(L/g).
In a centrifuge, the "gravity" you feel depends on your distance from the center of rotation. The farther from the center, the more centripetal force you feel. This means a pendulum hung higher up (closer to center) would have a different period than one hung below (farther from center).
Grace measures at two heights and gets the same result: 346 cycles in both cases. This rules out a centrifuge.
To generate 15 m/s² with a centrifuge on Earth would require a 700-meter radius spinning at 88 m/s. In space, 1,280 m radius. These are absurd numbers for a built structure.
Conclusion: the "gravity" comes from constant acceleration. A ship's engines push, creating a force indistinguishable from gravity. This is Einstein's Equivalence Principle.
Key terms
Try it yourself
How to use the simulator
A simple pendulum always takes the same time to swing there and back, and that period depends on only two things: string length and gravity (T = 2π√(L/g)). The simulator animates the pendulum with its real period and counts how many full swings it would make in ten minutes, which is exactly what you can measure with a watch.
Controls
- Scenarios: buttons that set Earth gravity (9.8 m/s²), Hail Mary gravity (15 m/s²) or Moon gravity (1.6 m/s²).
- String length: 0.1 to 3 m.
- Gravity: 0.5 to 30 m/s².
Things to try
- The starting values recreate Grace's experiment: with Hail Mary gravity and a 1.14 m string you get 346 cycles in 10 minutes. Now find the length that gives the same count under Earth gravity (about 0.74 m).
- Make the string four times longer and notice the period only doubles: it scales with the square root.
- Switch from Earth to the Moon with the same string. The swing is about 2.5 times slower, because √(9.8/1.6) ≈ 2.5.
Loading simulator…
Open “Pendulum period calculator” on its own page, with an explanation and a worked example →
The Sun is losing energy: exponential decay
Marissa tells Grace that the Japanese probe Amaterasu has detected the Sun losing luminosity exponentially. In 9 years it will lose 1%, in 20 years 5%.
The science behind it
Solar luminosity is the total energy the Sun emits every second. If it decreases, Earth receives less heat and light.
Exponential decay means something decreases faster and faster over time. At first it seems insignificant (0.01%, 0.1%), but accelerates dramatically (1%, 5%, 20%...).
Don't confuse this with the 11-year solar cycle, a natural variation in the Sun's activity (sunspots, flares). What they detect in the novel is an additional downward trend, something completely new.
A 1% drop in solar energy would cause notable global cooling. A 5% drop would trigger a severe ice age. For context: the last ice age (20,000 years ago) was caused by just ~5°C lower average temperature.
Key terms
Try it yourself
How to use the simulator
This model shows what would happen if the Sun dimmed steadily, at a compounding rate on the order of 0.3% a year. It isn't an astronomical forecast, since the real Sun is very stable. It's a way to see how sensitive Earth's climate is to small changes in the energy we receive.
Controls
- Years from now: 0 to 100. The Sun's disc shrinks and the panel shows the remaining luminosity and its rough effect.
Things to try
- Check how many years it takes to lose 5%. That sounds small, yet the panel already links it to an ice age.
- Compare it with the real 11-year solar cycle, during which luminosity changes by only about 0.1%.
- Move to 100 years and notice the decline slowing down: each year loses a percentage of what's left, not a fixed amount.
Loading simulator…
Open “Solar luminosity simulator” on its own page, with an explanation and a worked example →
Discovery of extraterrestrial life
The ArcLight probe orbits Venus and collects samples from the Petrova line. Onboard microscope images (10,000x) show black dots ~10 micrometers across that MOVE.
The science behind it
To travel between planets efficiently, there are "transfer windows": optimal moments where the relative position of planets allows spending less fuel. Outside these windows, the cost is prohibitive.
10 micrometers = 0.01 mm. This is the typical size of a human biological cell, or a large bacterium. At this scale, you need a microscope of at least 1,000x magnification to see details.
Scientists first rule out artifacts: probe vibrations, magnetic fields, static electricity... Only when they eliminate all non-biological explanations do they accept that the dots move on their own.
The X-ray spectrometer reveals chemical composition: what elements these organisms contain. The microscope shows shape and movement; the spectrometer tells what they're made of.
Key terms
Induced coma as suspended animation
Grace understands he was in a medically induced coma, not cryogenics. Robotic arms handled everything: feeding, hygiene, muscle stimulation, rotation.
The science behind it
Cryogenic freezing (freezing a body to revive later) does NOT exist as functional technology. Ice crystals that form during freezing destroy cells.
Induced coma IS real: used in ICUs for critical patients. Drugs are administered that reduce brain activity, protecting the brain from damage.
Electrical muscle stimulation (EMS) prevents atrophy. The robots also rotated Grace regularly to prevent pressure ulcers (bedsores), exactly as nurses do with real patients.
The risk is enormous: a coma of weeks is already dangerous. Years-long is extremely lethal. Only Grace survived out of 3 crew members, which is realistic.