Cover art to Czech edition of Dragon's Egg

This implies that they contain the same number of nuclei, so it is not surprising that on Earth their mass is about the same as human beings – 70 kilograms. Their bodies consist of complex molecules of bare nuclei. The cheela are flat, flexible creatures about 50 millimeters in diameter and 0.5 millimeters high. They have a density of about 7 million grams per cubic centimeter, the density of the crust of the neutron star... Cheela cannot breath or talk because the "atmosphere" of Dragon's Egg is only a few micrometers thick (around the "toes" of the cheela). The cheela communicate by strumming the crust with their lower surface, or "tread" to produce directed vibrations in the neutron star's crust.

Talking to these beings would be difficult. Their biology depends upon the strong nuclear force instead of the electromagnetic force. Nuclear reactions happen much faster than chemical reactions, because the nuclear force is much stronger... With a time difference of a million to one, a second to a human - the time it takes to say "Hello" - would be the equivalent of a week to a star creature. It would hear "He ... " on Sunday and "... lo" on the following Saturday.