Ok I'm now convinced.
In a perfectly sealed environment, the air displaced to create lift for the birds is being supported by the cabin structure and thus the airframe. Therefore will have no weight change.
For all intensive purposes, an aircraft cabin
is a sealed environment. The air that does flow has negligible effect.
The mesh aviary example given by
GW_04 however would have a weight change since the air displaced to create lift is free to flow out of the cage and is thus not still supported by the structure.
Thanks for all your help! I am now a wiser man
Oh and the other questions raised...
1. Yes, the air between the two pilots will still have zero velocity
2. If the train could hypothetically reach the speed of light, the light emitted from the lamp at the front will still appear to travel at the speed of light towards an observer in front of the train. It is time that becomes the variable as
c is a constant from
any frame of reference. See
time dilation....
3. Simply a question of legality rather than physics
Thanks again, I will surely spring another 'thought experiment' on you when I think of one!
...Disco