I'm sitting here on the couch with my MacBook Pro on my lap. I have a window behind me which is reflecting on my glossy screen. I notice the reflection is bouncing ever so slightly. I thought it might be the hard drive spinning, or something else. However, no such movement when on the ottoman. So I think the laptop is bouncing ever so slightly due to my heartbeat- or in other words with my blood pumping through my legs. I don't notice the slight movement when I look at an image on the screen, but when there is a reflection- its there! Can anyone else recreate this?