Zoom out but background stays the same

How do you zoom out so that everything in the foreground get smaller( as usual), but the background remains the same size?

You want a Skybox

It almost sounds like you are talking about a “reverse” dolly zoom, that effect in filmmaking where you move the camera closer to a subject while simultaneously zooming out the focal length of the lens (or vice versa). In Unity terms it would amount to adjusting the camera distance (translation) and Camera.fieldOfView at the same time to get the desired effect.

If memory serves me correctly, there might be a tutorial on this in the online docs/reference section.

Found it:

http://docs.unity3d.com/Documentation/Manual/DollyZoom.html