I have been watching the series, The Universe with great interest and there are a few of things that i am curious about, well more than a few but lets start with just 3 questions.
1st. From what i can gather, gravity and the effect it has on stars and planets is heat. As something is more compressed by gravity it creates friction and this creates heat, hence volcanoes on Neptune and so on. with a star, the gravity creates so much heat that it starts to effect elements such as hydrogen and helium and they create fusion and then eventually, gradually, they create higher based elements such as calcium and iron. By this reasoning, i was wondering how much heat a black hole creates. In all the discussions on black holes they are described literally as a hole that nothing can escape from, not even light. But what about heat? the only way to recognize a black hole is by the gravitational effect it has on stars around it but what if they were looked at in the infra red spectrum? Do black holes give off heat? How hot do they get and what elements are they creating?
2nd. It has been said that the universe is 156 billion light years across. Now, if nothing can go faster than the speed of light then i would think the furtherest thing we could see away from us would be about 13.5/14 billion light years. Even if we looked at the furtherest object to our south and the furtherest from our north that would still only be about 27/28 billion light years. How can they tell that the Universe is 156 billion light years across? I mean they cant possibly see anything in this universe that is say, 25 billion light years away so how do they know it is 156 billion light years across?
3rd. As a star starts to burn up hydrogen and helium and create heavier elements, does it become more massive (heavier) and will this effect happen to our sun and increase its gravitational strength. Or, does the act of fusion cancel out the weight difference and the sun will stay relatively the same weight until it dies.