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The circumference of the Earth has already been calculated in ancient Egypt. The calculations...
The last Ice Age ended about 13 thousand years ago.
Within the lethal embrace of deserts, life can only flourish because of large springs. Here...
Water is one of our key natural resources; we must protect it vigorously.
Human activity increases the greenhouse effect and leads to global warming.
The oxygen cycle describes the movement of oxygen within its three main reservoirs.
The four outer planets (Jupiter, Saturn, Neptune and Uranus) do not have solid surfaces, thus...
It is a sedimentary rock with high calcium carbonate content.