Dragon's Egg
Robert Forward
 Half a million years ago and 50 light-years from Earth, a star in the constellation Draco turns supernova, and the star's remnant becomes a neutron star. The radiation from the explosion causes mutations in many Earth organisms, including a group of hominina that become the ancestors of Homo sapiens. The star's short-lived plasma jets are lop-sided because of anomalies in its magnetic field, and set it on a course passing within 250&nbsp;astronomical units of the Sun. In 2020&nbsp;CE, human astronomers detect the neutron star, call it "Dragon's Egg", and send an expedition to explore it. The star contains about half of a solar mass of matter, compressed into a diameter of about , making its surface gravity 67&nbsp;billion times that of Earth. Its outer crust, compressed to about 7,000&nbsp;kg per cubic centimeter, is mainly iron nuclei with a high concentration of neutrons, Around 3000&nbsp;BC Dragon's Egg cools enough to allow a stable equivalent of "chemistry", in which "compounds" are constructed of nuclei bound by the strong force, rather than of Earth's atoms bound by the electromagnetic force. As the star's chemical process are about one&nbsp;million times faster than Earth's, self-replicating "molecules" appear shortly and life begins on the star. As the star continues to cool, more complex life evolves, until plant-like organisms appear around 1000&nbsp;BC. One lineage of these later became the first "animals", the earliest of these stealing seedpods from sessile organisms and some later lineages becoming predators. The adults of the star's most intelligent species, called cheela (no flexion for gender or number), have about the same mass as an adult human. However, the extreme gravity of Dragon's Egg compresses the cheela to the volume of a sesame seed, but with a flattened shape about high and about in diameter. Their eyes are wide. Such minute eyes can see clearly only in ultraviolet and, in good light, the longest wavelengths of the X-ray band. {| class="wikitable" style="font-size:80%; margin-left:2px; margin-top:-5px" align="right" width="300" |+ Timeline |- | 3000 BC || Life appears |- | 1000 BC || "Plants" |- | &nbsp; || Animals |- | 2032 || First weapon |- | rowspan="3" | 22 May 2050, 14:44:01 || Invention of agriculture |- | Volcano emerges |- | Clan invents new foraging techniques |- | rowspan="3" | 22 May 2050, 16:45:24 | Volcano forces clan to find new territory |- | Invention of mathematics |- | Self-sacrifice of the aged saves the clan |- | || Organized religion among cheela |- | 14 June 2050, 22:12:30 || Cheela develop writing |- | rowspan="2" | 20 June 2050, 06:48:48 || Cheela build religious arena |- | Humans send first message to cheela |- | || Cheela recognize "digital" pictures of humans |- | 20 June 2050, 07:58:24 || First successful cheela transmission to humans |- | 20 June 2050, 11:16:03 || Cheela realized both races were created by same supernova |- | 20 June 2050, 20:29:59 || Cheela's first experiments in gravity manipulation |- | 20 June 2050, 22:30:10 || Cheela expedition to human space craft |- | 21 June 2050, 06:13:54 || Final communication between cheela and humans |} In 2032, a cheela develops the race's first weapon and tactics while overcoming a dangerous predator. In November 2049 a human expedition to Dragon's Egg starts building orbital facilities. The rest of the story, including almost the whole history of cheela civilization, spans from 22 May 2050 to 21 June 2050. By humans standards, a "day" on Dragon's Egg is about 0.2&nbsp;seconds, and a typical cheela's lifetime is about 40&nbsp;minutes. One clan organizes the first cheela agriculture, which brings predictable food supply but provokes grumbling about the repetitive work. Shortly after, a volcano emerges in the area, and the clan invents the first sledge to carry food from more distant sources. However, within a few generations the volcano pollutes the soil. One clan leads its population on a long, arduous journey to new territory that is fertile and uninhabited. Although one genius invents mathematics to calculate and measure the band's food supply, the situation is desperate and the clan's survival depends on the self-sacrifice of the oldest members. Over the course of generations, the cheela come to worship the humans' spacecraft as a god, and their records of its satellites' movements cause them to develop writing. Several generations later, the cheela build an arena to accommodate thousands of worshippers. The humans notice this novel and very regular feature, conclude that intelligent beings inhabit the star, and use a laser to send simple messages. Cheela astronomers gradually realize that these are diagrams of the spaceships, its satellites and its crew – impossibly spindly creatures, who communicate with frustrating slowness, and are apparently almost 10% as long as the cheela's great arena. A cheela engineer proposes to send messages to the humans. As her attempts to transmit from the civilization's territory are ineffective, she travels to a mountain range to transmit directly under the spacecraft – conquering the fear of heights that is instinctive for flattened creatures living in 67&nbsp;billion g. The humans recognize her message and realize that the cheela live a million times faster than humans. Since real time conversations are impossible, the humans send sections of the expedition's library. After reading an astronomy article, a cheela realizes that the supernova half a million human years ago created both their races. Many cheela generations later, but only a few hours for humans, cheelas develop gravity manipulation. A few generations later, a cheela spacecraft visits the human one. Although they still need extreme gravity fields to survive, the cheela can now control them precisely enough for both races to see each other face-to-face in safety. The cheela have decided that transferring their technologies, now far advanced of humans', would stunt humanity's development. However the cheela leave clues in several challenging locations, before going their separate ways. <!--