 Why was Peter Karson initially relieved when he first heard the news of the invasion?
Outside, the stars were as before: tiny, myriad points of light, infinitely far away. I do not think it was what Peter called an emotion; and yet it had nothing to do with logic, either. His dream was perfect; the Citadel was complete, every minutest detail provided for—on paper. Then there would remain only the task of blasting the great, shining ship out into the carefully-calculated orbit that would be its home. He could see, too, the level on level of laboratories and storerooms that filled its interlocking segments; the meteor deflectors, the air renewal system, the mighty engines at the stern—all the children of his brain. He stared at them dully, and then he reached over to the newsbox on his desk, and switched it on. The order was made public early this morning by R. Stein, Secretary of the Council, who said in part: "The reason for this ... order must be apparent to all civilized peoples. "The peoples of the world, then, know what they are, and know that we face the most momentous struggle in our history. "Since the Invaders first appeared in Wood River, Oregon, 24 hours ago, they have not once acknowledged our attempts to communicate, or in any way taken notice of our existence as reasoning beings. They have treated us precisely as we, in less enlightened days, might have treated a newly-discovered race of lower animals. They have examined us, dissected us, driven us mad, killed us with no discernable provocation; and this is more intolerable than any normal invasion. Peter sank back in his chair, the full shock of it striking him for the first time. " Peter took it in fifteen seconds, running, and stumbled to a halt in front of the door marked "Radiation." He mouthed the syllables, had to repeat them because he put an accent in the wrong place, and squeezed through the door as soon as it opened far enough to admit him. It was a street scene in the Science City of Manhattan, flooded by the warm spring sunshine. Down on the lowest level, visible past the transport and passenger tubes, the parks and moving ways should have been dotted with colorful, holiday crowds. There were left only two blood-red, malignant monstrosities somehow defiling the air they floated in; and below them, a pitiful huddle of flesh no longer recognizable as human beings.
 It confirmed that what he saw was real, and he wasn't losing his mind.
 He was glad to know he wasn't the only person who had seen something.  He was glad to hear it reported, rather than ignored.  It confirmed that what he saw was real, and he wasn't losing his mind.  He feared he was going mad and was relieved to hear something from the real world.