Naked Science Forum

General Science => General Science => Topic started by: Karsten on 17/02/2010 20:26:36

Title: How do I prove that an event has occurred at a certain time but not later?
Post by: Karsten on 17/02/2010 20:26:36

I know how to prove that an event has not occurred at an earlier time. You take a photograph with something in it that did not exist before, e.g. a newspaper. But how can I do this if I want to prove that an event has not occurred later? What common thing stops existing at a certain time? What else could I do/use?

No, I have no particular plans. This question is just on my mind since I was a teenager and saw a picture of a hostage holding a newspaper to prove that he was still alive at a certain date.

Thanks.

Title: How do I prove that an event has occurred at a certain time but not later?
Post by: Bored chemist on 17/02/2010 22:21:41

Post a picture of it here. The website will date stamp it. You can't have produced it after that time.
The classic versions include posting a copy to yourself and not opening it so the postmark fixes the date or lodging a copy with a lawyer.

Title: How do I prove that an event has occurred at a certain time but not later?
Post by: lightarrow on 18/02/2010 19:49:49

Or, (fantasy answer): you could take a picture of the event printed in common paper, write something on the paper, also describing the exact kind of paper, printer and inks that you used (for the photo and for the writing). Then you seal up the paper hermetically inside a plastic bag (for example) to protect it. The paper and the ink (and the photo as well) will age; after many tens of years, an expert could analyze paper and ink (with also the help of the informations that you provided to him  [:)]) and he will have to conclude that it's an old document, and evaluate its age with some precision.

In case, ask an expert of ancient documents.