I wished to reach Mars at the moment of opposition, and during the whole of the journey to keep the Earth between myself and the Sun, for a reason which may not at first be obvious.

The moment of opposition is not necessarily that at which Mars is nearest to the Earth, but is sufficiently so for practical calculation.

At that moment, according to the received measurement of planetary distances, the two would be more than 40 millions of miles apart.

In the meantime the Earth, travelling on an interior or smaller orbit, and also at a greater absolute speed, was gaining on Mars.

The Astronaut, moving at the Earth's rate under an impulse derived from the Earth's revolution round the Sun (that due to her rotation on her own axis having been got rid of, as aforesaid), traveller in an orbit constantly widening, so that, while gaining on Mars, I gained on him less than did the Earth, and was falling behind her.