WELL, we’re over the shortest day and all that, to say nothing of far too much eating and drinking. So, why don’t the days start to lengthen till mid-January, which is pretty annoying to say the least.

The reason is that our seasons, the warmth of summer and the chill of winter, are due to the tilt of the Earth either towards or away from the Sun.

The Earth is tilted about 23.5 degrees off vertical, probably caused by being hit by a large object that created enough debris to form the Moon and gave us the tilt.

As the tilt is constant, it means for half the year each of our hemispheres is closer to the Sun and, therefore, gets more light and energy.

We also tend to assume the Earth has always had days of 24 hours over its history, but in fact they are getting longer anyway. This is because the Earth’s rotation is slowing very slowly - by about 74 thousandths of a second per year. Or, to put it another way, over the last 1.4-billion years, our days have gone from about 18 hours and 41 minutes a day to our current 24 hours.

This is due to the Moon moving, ever so slowly, further from the earth. It is getting about 1.5 inches further away each year and this is likely to continue for another 15-billion years, but I’ll let you know if that happens.

However, the issue is pretty academic as the Sun will enter its red giant phase in six to seven billion years, when it will expand and swallow up the inner planets.

This will happen when the Sun has used up all its hydrogen and burns helium which will cause the expansion.

The habitable zone will move out with the increasing temperature. The best current guess is Saturn’s planet Triton will retain its atmosphere and be the best place for Earth’s refugees to aim for. Ryan Air will be taking bookings soon.

Happy New Year.

• Fred Knobbit is a nature blogger. He grew up in the Pennines in Lancashire on the edge of an industrial town but is now safely in Cornwall. You can read his archive at www.bodminblogger.com