Friedrich Miescher in 1869
<span>Protected left turns are areas for turning that are controlled by a traffic signal or traffic sign. The traffic sign may be light.</span>
A green light means you may turn left. while <span>a red light means you must stop. Opposite to this, non protected left turns are not controlled by traffic sign.
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A satellite in a polar orbit passes over both poles, but the earth rotates beneath it. The time taken for each orbit of the earth depends on the height of the satellite. If the satellite is in a circular orbit 260 kilometers above the surface it will have an orbital period of two hours.
