Why must the window shades be "up" for takeoff?

I never before realized that one’s window shade on a commercial plane is supposed to be up during takeoff. Why is that? Who makes such rules?

I suspect that it’s for people who are prone to motion sickness to be able to see land/water/horizon to gain their bearings. Is this true? Are there any safety or physical reasons why this is needed?

Maybe it’s so passengers can see if there are any gremlins on the wings tearing the engines apart? :wink:

This has been discussed several times but the general reasons are:

  1. Light. If something happens and power is lost, you will need to be able to see. Open window shades let more light into the cabin.

  2. Safety. If if is neccessary to evacuate the plane in a hurry, you want to make sure the side you are evacuating to isn’t the one with the fire. Open shades let you check the outside before opening the emergency doors.

  3. It saves someone from having to go around and open all of them before the next set of passengers get on board.