High gas prices and problems with nuclear energy output also have meant that the country has become increasingly reliant on coal for power generation.

Overall industrial production rose 0.4% thanks to a cold-weather boost to energy output.

Also, as noted above, the energy output of a star increases over time, so the habitable zone actually moves outward as the star ages.

The trackers accurately measured energy output when walking but were off the mark with the less strenuous activities.

By solar maximum, the sun's total energy output rises by just 0.1 per cent, but its ultraviolet radiation increases by about 10 per cent.