Lets say I have a way to buy goods (say gold) from the past (say 30 years ago). I would like to take my new 100$ bill and buy the stuff, and then bring them back to the future (any movie references unintended). Sell the stuff for a profit because obviously its worth more here. Would the dollar bills I am using to pay for the goods be considered counterfeit in the past?

I am thinking this would be the case because the treasurer who signed it and serial numbers don't exist as yet or the serial number is duplicate.

closed as off-topic by NikolaiDante, Paul D. Waite, James Sheridan, Stan, Izkata Mar 25 '14 at 11:57

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  • 3
    It's not that gold is worth so much more in the present, but $100 was worth a lot more in the past than it is now. Don't try to pass modern currency in the past. Buy gold in the present and sell it in the past (like Heinlein's hero did in The Door into Summer) for good money, and use it to buy something that is more valuable now than it was then: well chosen stocks, mint copies of valuable comic books, etc. – user14111 Mar 25 '14 at 8:17
  • Gold is actually worth more in $ today. Although, I agree that your suggestions could actually be more profitable, and more legitimate. – LazyLeopard Mar 25 '14 at 11:17
  • Mrs Tachyon always carefully checked the dates on her money before spending it. – TRiG Mar 25 '14 at 11:37
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    This question appears to be off-topic because it is about how real-life monetary and government systems would deal with time travel, not sci-fi/fantasy. – Izkata Mar 25 '14 at 11:57
  • Bringing currency/valuables (even gold) into the future to sell isn't necessarily the best idea. See The Rip Van Winkle Caper. – phantom42 Mar 25 '14 at 12:58

It very much depends on the regime and the theory of time travel that you choose to use

  • Multiverse Theory

If your travelling into the past creates an alternate timeline then it's arguable that the future Treasurer who signed your bill may not end up being the Treasurer at the moment your bill was signed. Since there's no reliable way to know, then the bill would be ruled invalid under US Title 31, Subtitle 4 : Authorised Officers.

  • Single Universe Theory

If traveling into the past doesn't create a new timeline then you're guilty of duplicating currency and will almost certainly be guilty of an offence under US Title 31, Section 411 : Creating a color copy without permission.

Either way you can be pretty damn sure that the government would use their Domain laws to seize your money and prevent you from adulterating their currency.

  • +1 For proof that time travelling with money would be a federal crime! – user20155 Mar 25 '14 at 10:34

I've only seen this addressed once, on the show Journeyman. In an early, or possibly the pilot, episode Dan jumps into the past and tries to buy something using a modern banknote, which the proprietor doesn't accept - I believe he says something about the note being a forgery because he doesn't recognise the signature on the note (or the design changed or whatever).

Later on Dan is advised by another time jumper to get some old currency from the 60s/70s and keep it with him; in a yet later (or possibly the same) episode, he meets a plane hijacker who escaped with his ransom (I thought it was the actual D.B. Cooper, but Wikipedia says it was someone who stole money in the style of Cooper) and is able to take a large amount of the ransom money to use in his subsequent time jumps.

  • This is how I would assume it would go down - currency design changes frequently over the years and occasionally undergo massive changes. Our current $100 doesn't really resemble one from 20 years ago, at least not to any kind of inspection. – joshbirk Mar 25 '14 at 19:48

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