Earth sits about 93 million miles from the Sun, roughly halfway from the center of a galaxy called the Milky Way, on the outer edge of one of the largest known structures in the universe. Your “cosmic address” stretches across several layers of increasingly massive structures, from our solar system all the way out to a supercluster complex hundreds of millions of light-years wide.
Earth’s Place in the Solar System
Earth is the third planet from the Sun, orbiting at an average distance of about 93 million miles (150 million kilometers), a measurement astronomers call one Astronomical Unit, or AU. That distance isn’t fixed, though. Earth’s orbit is slightly elliptical, so the gap between us and the Sun shifts throughout the year. At perihelion (closest approach, around January 3), Earth is about 3.2 million miles closer to the Sun than at aphelion (farthest point, around July 4). That’s a 3.4 percent variation, enough that about 6.8 percent more solar energy reaches Earth in January than in July.
This slight stretch in our orbit is called eccentricity, and it’s currently very low, meaning Earth’s path is close to a perfect circle. Over a roughly 100,000-year cycle, the orbit gradually becomes more or less elliptical. Right now, eccentricity is slowly decreasing. One everyday effect: summers in the Northern Hemisphere are currently about 4.5 days longer than winters, because Earth moves a bit slower when it’s farther from the Sun. As the orbit becomes more circular, those seasonal differences will even out.
Earth also sits within the Sun’s habitable zone, the range of distances where temperatures allow liquid water to exist on a planet’s surface. Venus, our inner neighbor, is just inside the hot edge of that zone. Mars sits near the cold outer boundary. Earth is comfortably in the middle, which is one reason liquid water has persisted here for billions of years.
How Fast Earth Is Moving
Even when you’re standing still, you’re moving through space at extraordinary speeds. Earth rotates on its axis at about 1,670 kilometers per hour (1,037 mph) at the equator. If you live at around 40 degrees north latitude (roughly the latitude of New York or Madrid), that speed drops to about 1,280 km/hr because the circumference of Earth is smaller at higher latitudes.
On top of that, Earth revolves around the Sun at approximately 107,000 km/hr (about 67,000 mph), or 30 kilometers every second. You don’t feel any of this because everything around you, the atmosphere, the ground, your coffee, is moving at the same speed. And these two motions are just the beginning. The entire solar system is also hurtling through the galaxy, which is itself moving through intergalactic space.
Our Spot in the Milky Way
The Milky Way is a barred spiral galaxy, a pinwheel-shaped disk of stars, gas, and dust roughly 100,000 light-years across. Our solar system sits about 26,000 light-years from the galactic center, placing us roughly halfway between the core and the outer edge. At the very center of the galaxy lies Sagittarius A*, a supermassive black hole with a mass about four million times that of our Sun.
If you’ve seen illustrations of the Milky Way’s spiral arms, you might wonder which one we’re on. The solar system lives on a relatively minor arm called the Orion Arm (also known as the Orion-Cygnus Arm, the Local Arm, or sometimes just the Orion Spur). It sits between two much larger arms: the Perseus Arm on the outside and the Scutum-Centaurus Arm closer to the center. Think of it like living on a side street between two major highways. The Orion Arm is roughly 3,500 light-years across and about 10,000 light-years long, which sounds enormous but is modest compared to the galaxy’s primary arms.
From Galaxy to Supercluster
Zoom out further and the Milky Way is part of a small collection of galaxies called the Local Group. This cluster contains about 80 galaxies, the two largest being the Milky Way and the Andromeda Galaxy, which is about 2.5 million light-years away and on a slow collision course with us (the merger will happen in roughly 4 to 5 billion years). Most of the other Local Group members are small dwarf galaxies gravitationally bound to one of the two big ones.
The Local Group is, in turn, part of the Virgo Supercluster (also called the Local Supercluster), named for the Virgo Cluster of galaxies near its heart. The Virgo Supercluster contains roughly 100 galaxy groups and clusters spread across about 110 million light-years. But even this massive structure is just one piece of something bigger: the Laniakea Supercluster, identified in 2014, which spans about 520 million light-years and contains the mass of roughly 100 million billion suns. The Milky Way and its Local Group sit on Laniakea’s outer edges.
Beyond Laniakea, the structure continues. Laniakea is part of the Pisces-Cetus Supercluster Complex, one of the largest known structures in the universe. So your full cosmic address, from small to large, reads something like: Earth, Solar System, Orion Arm, Milky Way, Local Group, Virgo Supercluster, Laniakea Supercluster, Pisces-Cetus Supercluster Complex.
Why Earth Seems Like the Center (But Isn’t)
If you’ve ever seen a map of the observable universe, Earth appears to be right at the center. That’s not because we occupy a special position. It’s because the observable universe is defined by how far light has had time to travel since the Big Bang, about 13.8 billion years ago. Since light has been traveling toward us from all directions for the same amount of time, the bubble of space we can observe naturally forms a sphere with Earth at the middle. Every point in the universe has its own observable bubble centered on itself.
The full universe almost certainly extends far beyond what we can see. The observable portion has a radius of about 46 billion light-years (larger than 13.8 billion because space itself has been expanding during that time). What lies beyond the edge of our observable bubble is, by definition, something we can’t yet detect. But there’s no scientific reason to think Earth is at or near the center of the universe as a whole. We’re in a fairly ordinary spot: a mid-sized planet orbiting a mid-sized star on a minor spiral arm, about halfway out in an average galaxy, on the outskirts of a supercluster. Cosmically speaking, it’s a quiet neighborhood.