Ethan's time machine

Ethan has a big, inquisitive, and philosophical brain. Sometimes he can't remember to close the door behind him, and other times he floors us with a thought he has. This morning he got out a pencil and a notebook, and he told me the notebook would henceforth contain his inventions. Invention number one is a time machine. He drew a crude sketch, and then wrote out very specific instructions as to whom the time machine would be handed over to -"to the army for emergency uses only". Maybe a little naive, but he knows he doesn't want any "bad guys" getting a hold of it. So, the time machine has a power source, a generator, some knobs, and a few other things, and I said to him, "Well, bud, you know you need a mechanism that actually makes time travel possible (I was thinking of the "flux capacitor" from "Back to the Future")."
I told him that he will need to study lots of math and physics in order to one day see his plans for a time machine come to fruition. He said to me, "I believe someone can make anything they want to if they want it enough, even if everyone else says it's impossible." I said, "I think you are right." The we talked a little more about the specifics of what would be needed to make his time machine work. He said that in order to go back in time in his machine you would have to take with you an object that was from the time period to which you wanted to travel. I said something like, "So, if you wanted to go back to 5 Christmas's ago you would need, for example, a Christmas ornament that we used on our tree that year." He said that was correct. I said that it wouldn't work if I tried to use something that had just been made because it wasn't around from that time, and he said I was right. We were on the same page. Then, he said he hadn't yet figured out how to travel to the future, because if you needed an object from the past to travel there, how do you acquire an object from the future to travel there? I was standing at the kitchen sink thinking about his statement when, after a pause, he answered his own question. This is the part where I was just very impressed by my 8 year old's mind..He said, "You would need to use something that would grow in the future, like a plant." I was taken aback at his logic. He had reasoned it out way before I did. I said, a wee bit excitedly, "Yeah, so if you had a sapling, and of course one day it would probably grown into a big tree, you could use part of it to place in the time machine to take you to a future point in time!" See, I probably know only a fraction more about time travel than Ethan does, and what I know has to do with some of the theoretical problems associated with it; ie, can you kill your own grandfather if you travel to the past (without undoing your own future); can you travel back further than the time when your time machine was created; and can you travel back in time before you were born, and what happens if you die in the past? Anyway, so here is my eight year old child figuring that you need an object to actually link you to a point of time in the past, and then figuring out that the reciprocal of that is needing an object from the future, and solving it in a matter of seconds with the possibility of using something organic like a plant that is sure to grow in the future. Never mind that a person is technically an object that can be from a certain point in the past or future, he knows that some objects have been around for a long time, and some objects will exist into the future for quite some time. See, he didn't just have an idea and see it as boundless, he saw possible problems and came up with solutions to those problems. I don't care how rudimentary his notions may be, I see a real genius in it. I could be biased, and I am sure I am, but I believe if anyone is going to grow up and finally solve the problem of space/time travel, and successfully build a time machine it is going to be Ethan. Perhaps it is my belief in his potential that is also a necessary component to making his time machine work.