Here one for the older readers:
I read this short story, in an anthology, back in the '70's or early 80's.
A spaceship is approaching planet Earth at light speed, or maybe just really really fast, so humanity sends a ship to investigate. When they board, they find no-one on board, so they start looking round to see what's happening. The investigator finds a piece of paper on a desk with a few words on it. I can't remember what it said, but when he later goes back, he sees that there are a few more letters added to the sentence. Because the ship is going so fast, time is slower on the ship, so the person writing is doing the writing at their normal speed, and it just appears slow to the normal-paced investigator. I can't remember anything else, but the whole anthology was excellent but I left it on the 159 bus – if you found it then PM me.