"As we all have known since last Wednesday, this is precisely what Tremaine has in mind. The cobalt bomb is actually a hydrogen bomb with a layer of cobalt isotope surrounding it. While radioactive cobalt tritium from the H-bomb trigger is quickly dispersed and rendered harmless because the half-life of tritium is so short, radioactive cobalt can spread through the Earth's upper atmosphere on the jet-stream, raining lethal gamma rays from pole to pole.
"It is this terrible force which Alan Tremaine has threatened to unleash on the Earth."
"That's a lie!" Laura cried. "You are not even there. It's Keifer, using your name."
Alan nodded grimly. "He couldn't give such an ultimatum himself. The Outworld people wouldn't listen. But if they believe it's my decision...."
The commentator was saying: "... brief review of the points of Tremaine's ultimatum. One, unconditional surrender of all remaining Earth forces on the Outworlds. Two, repair of the space-warp bringing water from Venus to Mars. Tremaine claims Earth broke the warp, but the government has denied this right along. It is believed Tremaine is instilling hatred for Earth in the Federation peoples with this diabolical lie. Three, total independence for the Outworlds. Four, Tremaine threatens that if the first three conditions are not complied with by tomorrow night, twenty-three hundred hours Greenwich Time, he will unleash the cobalt bomb.
"Since Tremaine's Federation has sundered the space-warp itself, Earth is unable to comply with the second of Tremaine's points. While radar defenses are being alerted on a planet-wide basis, an unmanned rocket with a cobalt-bomb warhead, approaching the Earth at interplanetary speeds, could not be stopped. The Earth government has continued its hourly appeal to Tremaine not to destroy the civilization which has carried mankind out to the planets. So far, Tremaine has not responded."
"He—he wouldn't dare," Laura said as Alan shut the radio. But her voice lacked conviction.
"He might, Laura. He just might do anything. The radioactivity wouldn't last forever. Keifer might be planning to wait until it's dispersed, then return to Earth and extend his plans for empire there. All life would die, but he could replant crops, bring his hand-picked leaders to settle with him, and govern the solar system as a small totalitarian state."
"But I thought he wanted to take over Earth and all its people."
"He might figure they won't listen to him. If they do, he takes over. If they don't, he goes through with his ultimatum. Either way, he has Earth."