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Do giới hạn của vận tốc truyền ánh sáng mà chúng ta chỉ có thể quan sát một phần nhỏ của vũ trụ, được gọi là "Vũ trụ nhìn thấy" hay "Vũ trụ quan sát được". | EARTHQUAKES Jacques Laskar of the Bureau des Longitudes in Paris was a pioneer in the study of planetary chaos. He found many fascinating effects including the possibility that Mercury may one day collide with Venus and he drew special attention to chaotic influences on the orientations of the planets. The giant planets are scarcely affected but the tilt of Mars for example which at present is similar to the Earth s can vary between 0 and 60 degrees. With a large tilt summers on Mars would be much warmer than now but the winters desperately cold. Some high-latitude gullies on that planet have been interpreted as the products of slurries of melt-water similar to those seen on Greenland in summer. All of the inner planets must have known a powerfully chaotic episode in the course of their history Laskar said. In the absence of the Moon the orientation of the Earth would have been very unstable which without doubt would have strongly frustrated the evolution of life. E Also of relevance to the Earth s origin are Comets AND ASTEROIDS and Minerals IN SPACE. For more on life-threatening events see Chaos Impacts Extinctions and Flood basalts . Geophysical processes figure in Plate motions Earthquakes and Continents and supercontinents. For surface processes and climate change see the cross-references in Earth sysTEM. EARTHQUAKES S HIPS THAT LEAVE TOKYO BAY crammed with exports pass between two peninsulas Izu to starboard and Boso to port. The cliffs of their headlands are terraced like giant staircases. The flat part of each terrace is a former beach carved by the sea when the land was lower. The vertical rise from terrace to terrace tells of an upward jerk of the land during a great earthquake. Sailors wishing for a happy return ought to cross their fingers and hope that the landmarks will be no taller when they get back. On Boso the first step up from sea level is about four metres and corresponds with the uplifts in earthquakes afflicting the Tokyo region in 1703 and .
