Scanned Mail

You know how banks (with good online systems) scan your checks when they are deposited, and allow you to view them online to keep track of what's what?

You should be able to register an email address with the USPS or have online accounts. Then they should scan outgoing mail as soon as it's received and routed, and send you or post for you a picture of the mail that is coming to you. That way you can know if, say, a client has sent a check when they say they have. Or your landlord will know that a check is on the way. Or the IRS knows that you have sent your taxes in on time.

time travel and the grandfather paradox

I think that perhaps the Grandfather Paradox would not present a problem, because of the existence of True Randomness. In contrast to the pseudo randomness available to computer programmers, True Randomness is seen in nature in things like radioactive decay.

Say an individual has discovered a way to travel into the past. I believe that because of True Randomness, this individual's visit to the past means that it is not necessarily an identical past to the one experienced in that individual's 'present' timeline. Small differences in the results of Truly Random events will create changes. Perhaps these changes will be extremely minor, except when necessary.

Necessary differences will occur due to paradox. In the Grandfather Paradox, if a time traveler travels to the past and kills his grandfather he would have created circumstances such that he would never have been born -- which means that the grandfather would not have been killed, and the traveler would be born after all. And so on.

Presumably, these conflicting realities would flip back and forth, back and forth, ad infinitum.

In programming, in order to avoid repeating a value, you would use a while loop:

[pseudocode]
oldValue = 5
newValue = random()
while (newValue == oldValue) {
newValue = random()
}
[/pseudocode]

I think that if a time travel would encounter such a paradox that would result in conflicting realities flipping back and forth, the realities themselves would be slightly different each time because of different outcomes in normal Truly Random events. Eventually, a version of reality would occur that would result in the negation of the paradox.

Example: a time traveler travels back in time to kill his grandfather. Reality flipping ensues, but in an alternate reality the Truly Random event of the time traveler's conception would result in an invalid fetus instead of the DNA sequence that resulted in the time traveler. The new reality would continue, which would contain both the grandfather, and no murdering time traveler.