"Not yet," Thor growled, and told them of the Discoverer, and the astral voyage they had made.
Gordon wrinkled furrowed brows. "Can't see what good knowing that is, you know. It—"
"Think, man. I'm not too good at chemistry, but there are clues and hints all over this planet. Most of it is sand, rolling mile after mile. Even the red grasslands have sandy beds. And the rocks. There is almost as much rock as sand. What do you and the robots build your cities of? Clay! What jewels are embedded in the cave where Aava dwells? Opal, onyx, carnelian, jasper!
"Aava lives in a circle of pure quartz. Look!"
Thor put his hand in his pocket, drew out tiny green flecks of crystal, "I got this by scraping the urn where Aava appeared to his androids in the temple. It's glass! Something in Aava's nature was hardened by oxygen, and the sand in the substance of the urn turned into glass!
"When the Discoverer took me out into space and back in Time, when I saw the worlds of this space-realm created, one thing struck me. I watched Aava and his planet evolve from an empty void, saw the planet grow and take form.
"Gordon, I saw no fern forests, no great jungles of vegetation whose rotting and sinking into peat bogs gave us coal. Coal is carbon. And there were no petroleum wells, and petroleum is a compound of hydrocarbons."
Gordon rubbed his chin, frowning. "It's all jolly interesting, old man."
Thor waved a hand. "Can't you see? It all argues just one thing. No coal, no oil. No forms of carbon at all. Just quartz, sand, onyx, jasper, clay, carnelian, opal, rock—all forms of silicon.