WHY WEAKNESSES? 1 - All reference frames are equally valid. Relativity is based on observable facts and not in real facts. 2 - Time is a dimension of space. Time is flowing, space is static, the bodies move in it. 3 - It is possible the time travel. Time has only one dimension: from past to future. Never from future to past. 4 - Gravity is not a force. Gravity is one of the fundamental forces. 5 - The cosmological constant. Einstein couldn't prove it.