possible explanation for the red thread in the air:

1. my first reaction - there is a giant mutant spider
2. which logically comes with the first (provided by qh) - spiderman paid a visit
3. someone was trying to fly a kite sitting on the tree and the kite was caught on the roof of my block (not the other way round coz there is no kite on the tree).
4. since it was likely that the thread was led to 8th floor of my block where the laundry room is, i was thinking maybe someone's clothes got so torn up a long thread was blown out of the window and somehow landed on the tree.
5. a girl was having an affair with a guy staying on the 8th floor and she had to have an escape route.
6. 月老在牵红线的过程中撞到了树上.

click on the photo below to see an enlarged version. the red arrows are pointing to the thread.