Autumn equinox 2026 Earth orbit challenge

The September equinox happens while Earth is moving in an almost circular orbit around the Sun. State the force that keeps Earth in orbit around the Sun.

Earth's orbital speed is approximately constant during this simplified circular-orbit model. Explain why Earth is still accelerating as it moves around the Sun.

Use the following data to calculate Earth's mean orbital speed. Mean orbital radius, $r=1.50\times 10^{11}\mathrm{m}$ Time for one orbit, $T=3.16\times 10^7\mathrm{s}$ Use: circumference of a circle $=2\pi r$.

Earth is closest to the Sun during January, when it is winter in the UK. Earth is farthest from the Sun during July, when it is summer in the UK. Explain why this evidence supports the model that Earth's axial tilt, rather than its changing distance from the Sun, is the main cause of the UK seasons.