Why can't audible sound be used to create an image like ultrasound? Why does it have to be ultrasound?

Which instrument is used to measure air temperature

The seven sisters, seven stars located more than 400 light-years away in the taurus constellation can be seen here with venus and another constellation, orion. the seven stars stay grouped together but seem to move, like the planet venus. why do stars seem to move like planets in the night sky?

You can decrease the resistance of a length of wire by