Building a Shared Language
Measuring mass in zero-g, exponential vocabulary, and loneliness
Spoiler warning: this page discusses the novel's plot up to this chapter. It doesn't quote passages from the book.
Grace and Rocky build shared vocabulary at exponential speed. Grace invents a method to measure mass without gravity, and Rocky reveals a devastating truth: his entire crew died from interstellar radiation.
How to measure mass in zero gravity
Grace ties a string with two containers at the ends and balances water against an iron ball until they spin at the midpoint.
The science behind it
Weight depends on gravity: you weigh less on the Moon, more on Jupiter, nothing in space. But mass is intrinsic: it doesn't change regardless of where you are.
Grace's trick: two objects on the ends of a spinning rope. If both have the same mass, the center of rotation stays in the middle. If one is heavier, the center shifts toward it.
Using water as reference (density = 1 kg/L), Grace measured the water's volume with a syringe (in cubic centimeters = milliliters) and directly got mass in grams. Result: 325 g.
Rocky already knew the answer: the ball was iron (element 26). With the measured diameter and iron's density (7.87 g/cm³), the theoretical mass is 328.25 g. Grace was only off by 1%.
Key terms
Try it yourself
How to use the simulator
In free fall a scale is useless, because nothing has weight. Mass is still there, though, and it shows up as inertia. Tie two objects together and spin them, and the pair rotates around its center of mass, which sits closer to the heavier one. When the masses are equal, the center is right in the middle and the system spins evenly.
Controls
- Water (mL = g): the amount of water in the reference bag. One milliliter of water has a mass of one gram.
- Object (g): the mass of the object you want to measure.
Things to try
- Recreate Grace's experiment: adjust the water until it balances a 328 g object. The system counts it as balanced once the difference is under 5 g.
- Make the masses very unequal and watch the system shift toward the heavier side.
- Think about precision: 325 versus 328 g is an error of about 1%, excellent for an improvised instrument.
Loading simulator…
Open “Measuring mass without gravity” on its own page, with an explanation and a worked example →
Language grows exponentially
Grace and Rocky go from numbers to "yes/no" to abstract concepts. The dictionary grows faster with each new word.
The science behind it
Zipf's law applied: the first words in any language are the most used (numbers, "yes," "no," basic verbs). With each new word, you can define more words using the ones you already have.
It's like compound interest: progress starts slow (10 words → 20 in a day). Then accelerates exponentially (100 → 300 in a day) because you combine existing ones.
Rocky has perfect auditory memory: remembers every chord without notes. In humans, a large brain area is dedicated to vision. In Eridians, that area likely serves sound.
Mathematical base is universal: you don't need a natural language for two intelligent species to start communicating. Numbers + pointing at objects + yes/no is enough to begin.
Key terms
Rocky's loneliness: 23 crew members killed by radiation
Rocky reveals he was the sole survivor. His crew of 23 died from cosmic radiation. Rocky survived because he was surrounded by astrophages.
The science behind it
Erid has a magnetic field 25× stronger than Earth's and 29 atmospheres of protection. Eridians NEVER evolved radiation resistance because their planet protected them 100%.
Leaving Erid's magnetosphere, the crew received lethal doses of galactic cosmic rays (GCRs): protons traveling near light speed, created by supernovae.
Rocky survived because he was in the workshop, surrounded by astrophage containers. Astrophages block all radiation (supertransversality): not even neutrinos pass through them.
When Rocky speaks softly (an octave lower), he expresses sadness. Humans also lower pitch and volume when sad. Emotional expression through sound is a biological universal.
Key terms
Worked example: how precise does Grace's balance need to be?
Two masses joined by a string of length L spin around their centre of mass, which sits L·m₂/(m₁ + m₂) from the first one. If the masses are equal, that point is exactly in the middle. Its shift from the centre of the string is (L/2)·(m₂ − m₁)/(m₁ + m₂).
With the chapter's numbers, 325 g of water against 328.25 g of iron on a 1-metre string, the shift is 0.5 × 3.25 / 653.25 ≈ 0.0025 m: just 2.5 millimetres. To spot a 1% difference, Grace had to notice whether the pivot moved by a couple of millimetres. Her error is perfectly reasonable for a device made of string and bags.
You can also check the size of the ball. 328.25 g of iron (7.87 g/cm³) takes up 41.7 cm³, which is a sphere about 4.3 cm across: a little smaller than a golf ball.
Real astronauts solve the problem differently. On the International Space Station, the SLAMMD device pushes the crew member with springs that apply a known force and measures the resulting acceleration, so mass comes from F = m·a. Other devices bounce the person on a spring and time the period, because T = 2π·√(m/k): the more mass, the slower the oscillation.