At the time of Isaac Newton, the celestial bodies are set into motion by the so-called ether, a substance that is supposed to fill the entire universe. But no one has been able to prove this substance. Newton recognizes: Instead of ether, there must be a universal long-distance effect, which starts from the heavenly bodies themselves: the heavier a body is, the stronger its attraction. So the heavenly bodies keep each other on their orbits.
<a href="//commons.wikimedia.org/wiki/User:ZDF_Terra_X_Redaktion" title="User:ZDF Terra X Redaktion">ZDF/Terra X/</a> T. Schultes/ Aleks &amp; Shantu
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