Kate Humble: 'As close to the Sun as I'll ever be'
On a day in early January, the Earth is closer to the Sun than at any other time during the year.
That day is known as perihelion. Despite the Sun being 3.1 million miles (5 million km) closer to the Earth on perihelion than in July, the Earth's tilt means it is still winter in the northern hemisphere.
See Orbit: Earth's Extraordinary Journey on BBC2 at 21:00 on Sunday March 11 and afterwards on the BBC iPlayer.