Earth

Earth reaches its farthest point from the Sun, aphelion, in early July—the Northern Hemisphere's summer. At ~152 million km, it is 5 million km farther than in January. Seasons come from axial tilt, not distance: Earth is farthest from the Sun in midsummer.

The International Space Station orbits Earth every 92 minutes, so its crew sees 16 sunrises and sunsets daily. A 45-minute day-night cycle would wreck their sleep — so astronauts keep window shades closed and run the station on Greenwich time, regardless of the light outside.

Earth's magnetic field has flipped hundreds of times; the last reversal was about 780,000 years ago. During reversals the field can weaken to under 10% of today’s strength, letting auroras appear near the equator. Since 1840, Earth’s field has already weakened by about 9%.

The Moon drifts 3.8 cm farther from Earth every year, about the rate fingernails grow. Two hundred million years ago, in the dinosaur era, the Moon was closer and Earth's spin faster: a day lasted about 23 hours. Apollo 11 retroreflectors let lasers measure the retreat.

A photon born in the core of the Sun takes tens of thousands to hundreds of thousands of years to reach the surface. Trapped in ultradense plasma, it is absorbed and re-emitted in a random walk. Once it escapes, it crosses 150 million km to Earth in just eight minutes.

Helium was discovered on the Sun before on Earth. During an 1868 eclipse, astronomers found an unknown yellow line in the solar Spectrum; Norman Lockyer named the new element after Helios. It was not isolated on Earth until 1895.

The point farthest from Earth's centre isn't Everest but Ecuador's Chimborazo. Earth's spin bulges the equator, pushing sea level there ~22 km farther out than at the poles. Although Chimborazo stands 2,585 m lower than Everest, its summit sits 2.1 km farther from the centre.

There are more trees on Earth than stars in the Milky Way. A 2015 Nature study estimated about 3 trillion trees, while NASA counts 100 to 400 billion stars—over seven times more trees. The same study found Earth's trees have dropped about 46% since civilization began.

Earth's closest planet on average isn't Venus but Mercury. Bigger orbits spend longer on the far side of the Sun, so average distance grows. Mercury's tiny orbit keeps it near every planet. Earth–Mercury averages 1.04 AU, Earth–Venus 1.14 AU. The "Whirly Dirly Corollary."

The Moon's orbit doesn't spiral around Earth as most people imagine. Because the Earth-Moon distance is tiny compared to the Earth-Sun distance, the Moon's actual path through space is nearly circular, traveling alongside Earth around the Sun.

Earth has 365 days in a year, but actually rotates 366 times. The extra rotation comes from its orbit around the Sun — an example of the coin rotation paradox.