 What isn't something the guest expects the younger man to do?
There is one fact no sane man can quarrel with ... But some men aren't sane; thus it isn't always so! You will, you know, so why quibble about it? At least, you always have ... or do ... or will. You're wondering whether to give me a drink, as I remember it. And naturally, since we have the same tastes, you can make the same for me as you're having. It's a real wrench when a man meets himself for the first time. So let's begin when you get up in half an hour and come out with me. Yes, it'll be pretty obvious it must be a time machine. You'll be puzzling over what I'll tell you, and you'll be getting used to the idea that you are the man who makes atomic power practical. You won't exactly believe it, but you'll want to go along. You are completely outside of time and space, as best you can guess how things are. Doesn't hurt, and when you pull your arm back, you're still sound and uninjured. Then you feel silly, because you'll remember that I said you'd ask that. Well, I asked it after I was told, then I came back and told it to you, and I still can't help answering when you speak. Maybe there is no machine, and it's just easier for us to imagine it. When you spend thirty years thinking about it, as I did—and you will—you get further and further from an answer. Anyhow, you sit there, watching nothing all around you, and no time, apparently, though there is a time effect back in the luggage space. That means you either carry a small time field with you, or you are catching a small increment of time from the main field. You suddenly realize that everything in the machine is wide open, yet you haven't seen any effects of air loss. "This is like the things they wear in this century, as near as I can remember it, and I should be able to pass fairly well. He told me, just as I'm telling you, that it's an interstellar civilization." We have to walk up a flight of stairs, and there is an elevator waiting, fortunately with the door open. There's no feeling of acceleration—some kind of false gravity they use in the future.
 listen to his directions very carefully
 steal something from a museum  take credit for an invention from the future  run the time machine  listen to his directions very carefully