Hi, I am pleased to have joined and I hope to browse this forum when I have some time. I have started reading A Brief History of Time for the first time and wanted to express how awesome this book is already (chapter 3 started) and how much it is making me think (and not about work). Chapter 2 has diagrams of cones but I am more comfortable for now thinking in spheres than cones, so I envisage a future light sphere and a past light sphere. Is it possible I could come unstuck at a a later point if I persist? I am thinking of light bulbs moving away from me but thier light is coming towards me, coming towards everything actually, as an expanding sphere. As the bulb moves away someone 'switches it on' and a solid white sphere starts expanding outwards, and as it says in the book regardless of the speed of the bulb or its direction. When someone switches the bulb off a black sphere starts expanding outwards from the bulb representing the lack of light - in the centre of the white sphere if the bulb was stationary or off-centre if it kept moving but still a sphere and still at the same speed as the white sphere. I am hoping I am on track with this.. Light is in waves, but I don't know if that makes it discrete or continuous or something else. Also, the sphere of white light engulfs a sun at some point and continues. Being a sphere I am thinking it doesn't matter where the sun is in relation to the start of the event (bulb switching on) because all points on the surface are equal? I am having trouble visualising how the sun will distort the shape of my sphere and even harder for me - how it will affect time (or speed? think this might take a while). I also don't know if it matters from what position this engulfment is being observed. ..and wrestling still with the idea that an expanding universe will look the same from one time period to the next, in every direction from any position (if I have read and understood that part correctly - better re-read). Thoroughly looking forward to the rest of the book and can see I won't be finishing it any time soon. Could be the best book I've ever read. That was a bit long, sorry.