Space Encyclopedia
🌍 Earth
Overview
Earth is the third planet from the Sun and the only known world to harbor life. Its magnetic field and thick atmosphere shield the surface from most of the Sun's harshest radiation, while allowing enough solar energy through to drive climate, weather, and — during geomagnetic storms — the aurora borealis and aurora australis.
Key facts
- •Diameter: 12,742 km (7,918 mi)
- •Distance from Sun: ~149.6 million km (1 AU)
- •Day length: 23h 56m 4s (sidereal)
- •Orbital period: 365.25 days
- •Magnetic field strength at surface: ~25–65 microtesla
Why it matters
Earth's magnetosphere is our first line of defense against solar wind and coronal mass ejections. When that shield is compressed by strong solar activity, GPS accuracy degrades, HF radio can black out, satellites drag lower, and auroras push far south of the polar circle.
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Frequently asked questions
Why does Earth have auroras?
Charged particles from the Sun follow Earth's magnetic field lines down into the upper atmosphere near the poles. When they collide with oxygen and nitrogen atoms, those atoms glow — producing the aurora.
How does space weather affect Earth?
Strong solar storms can knock out radio communications, disrupt GPS, damage satellites, induce currents in power grids, and endanger astronauts. Earth's magnetic field absorbs most of the impact.
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