"I did this to you and you may hate me for it; I do not know. That is up to you to decide, but it does not matter. What does matter, and not to you alone, is another decision which you must make. I am incapable of making it. "Who is writing this to you? I would rather not tell you just yet. By the time you have finished reading this, even though it is not signed (for I knew you would look first for a signature), I will not need to tell you who I am. You will know. "I am seventy-five years of age. I have, in this year 2004, been studying 'time' for thirty of those years. I have completed the first time machine ever built--and thus far, its construction, even the fact that it has been constructed, is my own secret. "You have just participated in the first major experiment. It will be your responsibility to decide whether there shall ever be any more experiments with it, whether it should be given to the world, or whether it should be destroyed and never used again." * * * * * End of the first page. You look up for a moment, hesitating to turn the next page. Already you suspect what is coming. You turn the page. "I constructed the first time machine a week ago. My calculations had told me that it would work, but not how it would work. I had expected it to send an object back in time--it works backward in time only, not forward--physically unchanged and intact. "My first experiment showed me my error. I placed a cube of metal in the machine--it was a miniature of the one you just walked out of--and set the machine to go backward ten years. I flicked the switch and opened the door, expecting to find the cube vanished. Instead I found it had crumbled to powder. "I put in another cube and sent it two years back. The second cube came back unchanged, except that it was newer, shinier. "That gave me the answer. I had been expecting the cubes to go back in time, and they had done so, but not in the sense I had expected them to. Those metal cubes had been fabricated about three years previously. I had sent the first one back years before it had existed in its fabricated form. Ten years ago it had been ore. The machine returned it to that state. "Do you see how our previous theories of time travel have been wrong? We expected to be able to step into a time machine in, say, 2004, set it for fifty years back, and then step out in the year 1954 ... but it does not work that way. The machine does not move in time. Only whatever is within the machine is affected, and then just with relation to itself and not to the rest of the Universe. "I confirmed this with guinea pigs by sending one six weeks old five weeks back and it came out a baby. "I need not outline all my experiments here. You will find a record of them in the desk and you can study it later. "Do you understand now what has happened to you, Norman?" * * * * * You begin to understand. And you begin to sweat.