 Why did Peter choose to break all the mirrors inside the ship?
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. 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. Out there, away from the muffling, distorting, damnable blanket of atmosphere, away from Earth's inexorable gravitational pull, would be a laboratory such as man had never seen. "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. "I have no fear that the people of Earth will fail to meet this challenge, for there is no alternative. Not only our individual lives are threatened, but our existence as a race. It was only two stories down the moving ramp to Lorelei Cooper's laboratory. Peter took it in fifteen seconds, running, and stumbled to a halt in front of the door marked "Radiation." 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 will be panics and suicides, and they know it; but they have to do it. This isn't like a war, where the noncombatants' morale has to be kept up. There aren't going to be any noncombatants, this time. It was impossible to say whether they had gone through the solid wall, or simply melted away. Peter walked down the narrow aisle, past bakelite-sheathed mechanisms and rows of animal cages, and paused just short of it.
 He didn't want to see the changes to himself due to the rays.
 The mirrors were harmful to the embryos  The mirrors reflected too much light.  He needed his full attention on the task at hand.  He didn't want to see the changes to himself due to the rays.