First Contact
Trigonometry, spacewalks, and ammonia
Grace calculates the alien ship's size with trigonometry, establishes communication through engine flashes, goes on a spacewalk in an Orlan suit to retrieve a cylinder, and discovers the alien lives in a high-temperature ammonia environment.
Calculating an object's size with trigonometry
Grace uses radar (angular width: 35.44°, distance: 217 m) and arctangent to determine the alien ship is 139 meters long.
The science behind it
If you know the distance to an object and the angle it occupies in your field of view (angular width), you can calculate its real size: size = 2 × distance × tan(angle/2).
With distance = 217 m and angle = 35.44°: size = 2 × 217 × tan(17.72°) = 2 × 217 × 0.3193 = 138.6 m. The Hail Mary is only 47 m.
This principle is used constantly in astronomy. The Moon's apparent size (angle) is ~0.5°. Knowing the distance (384,000 km), we calculate its real diameter: 3,474 km.
Proximity radar works by emitting radio waves and measuring the echo. The time difference between emission and reception gives distance. The echo's extent gives angular width.
Key terms
Try it yourself
Angular Size Calculator
Grace calculated 139 m for the Blip-A at 217 m and 35.44°
Communication through engine flashes
Grace briefly fires his engine and the other ship replicates the pattern. Basic communication established.
The science behind it
If an intelligent being replicates a pattern you send, it proves: (1) it perceives the signal, (2) recognizes it as communication, and (3) intends to respond. This is SETI's fundamental protocol.
The response is too quick for remote control: if the ship were controlled from a distant star, the signal would take years to arrive. A seconds-fast response confirms onboard intelligence.
The speed of light imposes an absolute communication limit. At any stellar distance (light-years), real-time remote control is physically impossible. Only onboard life can respond instantly.
Key terms
The Orlan suit and extravehicular activity
Grace puts on a Russian Orlan suit in 5 minutes and goes out into space. The Hail Mary operates at 40 kPa, eliminating prebreathing.
The science behind it
The Russian Orlan suit is one piece: you enter through a rear hatch, like a closet. Much faster to put on than the American EMU suit, which has two separate pieces and requires assistance.
On the ISS, hours of pre-breathing are needed before an EVA. The station operates at normal pressure (101 kPa) and the suit at ~40 kPa. Reducing pressure too quickly causes decompression sickness (nitrogen bubbles in the blood, like divers).
The Hail Mary already operates at 40 kPa (40% of atmospheric pressure). Grace breathes pure oxygen at lower pressure, like Apollo astronauts. Advantage: he can suit up and go directly.
EVA golden rule: always one tether attached to the cable. Never free-float. If you let go without propulsion, you drift forever. The NASA suit has an emergency SAFER unit; the Orlan doesn't.
Key terms
The alien cylinder: ammonia and extreme heat
Opening the cylinder inside the ship, Grace smells strong ammonia and the object is still hot after 40 minutes in space.
The science behind it
In space, without air, objects lose heat ONLY through radiation (no convection or conduction). This process is slow: follows the Stefan-Boltzmann law (P = σ × A × T⁴). If still hot after 40 minutes, its initial temperature was very high.
Ammonia (NH₃) residue in the cylinder reveals the alien ship's interior has an ammonia atmosphere. NH₃ is gas at room temperature (boils at -33°C), but under pressure it can be liquid at much higher temperatures.
This validates Grace's academic thesis: life exists that doesn't need liquid water. The aliens live in a hot, pressurized ammonia environment.