כדור הארץ.

The only world we know of with oceans on its surface, a breathable atmosphere and life.

Earth is the largest and densest of the rocky planets. About 71% of its surface is covered by oceans, and its nitrogen-oxygen atmosphere and magnetic field shield life from much of the Sun’s harmful radiation.

Its spin axis is tilted about 23.4° to its orbit, which causes the seasons. It has one natural satellite, the Moon. The orbit data here are for the Earth-Moon barycentre, the balance point of the pair.

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מקורות נתונים

• NASA NSSDCA Planetary Fact Sheet
• JPL SSD: Planetary Physical Parameters