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## Main Question or Discussion Point

Hello,

I have a question : is it possible to explain the first law of Kepler without any concept of mass ?

Kepler's first law states that satellites are moving on an ellipse and the object around which they are orbiting is localized at the focus of this ellipse. As far as I know Newton and Einstein explained this special natural behavior, in two different ways, and they needed to introduce the concept of mass to achieve this goal. However Galileo from the top of the Pisa tower, and the astronauts from the moon, experienced that bodies are falling at the same speed what ever their masses are. Therefore would it be possible to explain Kepler's first law without any use of the mass ?

Thanks for contributions.

Best regards

Herve

I have a question : is it possible to explain the first law of Kepler without any concept of mass ?

Kepler's first law states that satellites are moving on an ellipse and the object around which they are orbiting is localized at the focus of this ellipse. As far as I know Newton and Einstein explained this special natural behavior, in two different ways, and they needed to introduce the concept of mass to achieve this goal. However Galileo from the top of the Pisa tower, and the astronauts from the moon, experienced that bodies are falling at the same speed what ever their masses are. Therefore would it be possible to explain Kepler's first law without any use of the mass ?

Thanks for contributions.

Best regards

Herve