ocr: OPEN UNIVERSE The model of the universe which is considered correct at the moment. The uni- verse was born in the big bang about 12 billion years ago and has been ex- panding ever since. If gravitation someday overcomes the repulsion caused by the expansion, the universe will begin shrinking. This model is called closed universe. Between these models there is a special case: if the expansion's ki- netic energy is equal to the contracting force of gravitation, the universe will just barely keep expanding. Present colculations show the universe's expansion ve- locity to be very near the critical ...
