 Writer Robert L. Forward described being inspired by astronomer Frank Drake 's suggestion in 1973 that intelligent life could inhabit neutron stars . Physical models in 1973 implied that Drake 's creatures would be microscopic . By the time Forward was outlining the book , newer models indicated that the cheela would be about the size of sesame seeds . Later Forward found an earlier letter in which he discussed the idea of high @-@ gravity life in the Sun with science fiction novelist Hal Clement . 
