I was thinking about this when I read the article. I found myself thinking that you'd have to present convincing evidence that you were from the future in such

I was thinking about this when I read the article. I found myself thinking that you'd have to present convincing evidence that you were from the future in such a way that you didn't change history - but then I realized that the whole purpose of the time travel would be to change history, so maybe that wouldn't be a limiting condition. Maybe the time traveler could present a working ray gun?