I understand that the double slit experiment (i.e. the creation of interference pattern) holds also when the "particle" is not just a single particle but any item, experimentally proven even for a C60 molecule.
I am wondering what is the correct interpretation of the double slit experiment when the particle under test is a macroscopic object, like a space capsule with people inside.
I think that in order to obtain the interference pattern the capsule shouldn't be hit by any photon coming from the external environment (or any other particle). So the people inside the capsule are not able to understand which slit they are going through since they can't receive any information from the outside world.
People outside the capsule are not able either to see the capsule during his flight otherwise the wave function of the capsule will collapse to a specific position.
I guess the experiment setup would require extremely low temperature of the objects involved (at least on their external surface) and a very controlled environment.
Is this interpretation correct?
Are the people inside the capsule able to make some internal experiment to cause the capsule wave function to collapse (and to avoid any interference pattern when they hit the final wall?) even without interacting with the external environment?
[Edit] Thanks for your answers. Actually I want to clarify my question. I am not asking why we don't usually see interference pattern on macroscopic objects. I am wondering what's the interpretation of the interference pattern we see (do we see it?) when we setup an experiment with such macroscopic object. Obviously it is a thought experiment and it doesn't really matter if it's technically unfeasible.
In example, considering the numbers that tom proposed, we have that _lambda is 4e-38m. Now, if the slits are 10m wide and they are 1000m apart, the interference pattern should emerge for angles of about 4e-41 radiants. So if the wall is like 1e45m far (let's forget about cosmology) then we should see the crests of the interference pattern kilometers apart.
So what really happens in such scenario? I can think of the following options: 1) Interference pattern emerge, passengers and external observer can't tell which slit the ship went through since the experiment itself requires no interaction between the ship and the environment 2) Interference pattern doesn't emerge even if the ship doesn't interact with the other objects as it's too complex and its wavefunction collapses anyway. 3) ?
We can make the experiment cosmologically more realistic. We can use a nanorobot (able to record some observations and perform little experiments, so conceptually equivalent to a human being) with a mass of 1e-18kg and make it travel at 1mm/s. If the slits are .1m apart, we should expect interference crests .1m apart after a Sun-Earth distance.