If i shoot my 1W 450nm blue laser pointer at the sky from my room, will the beam be so bright that people who for example are walking in the street, will see the beam from side and get scared and catch their attention to the beam?
I would definitely not recommend doing that. Depending on what country you're in you may also have the Feds bust your door down and fire beanbag rounds into your groin. Seriously though it's not a good idea and be sure to know all your local laws. Where I live any use of lasers over 1mW outdoors within 10km of an airport is a huge no-no. Even if it is legal in your area it could well alarm people and cause a problem. Also it is your responsibility to check for aircraft and make sure your beams never go anywhere near them.