What is a cosmic address?
A cosmic address is your address written for the whole universe. A normal address zooms in: country, city, street, house. A cosmic address zooms out from where you stand. Planet, star system, galaxy, galaxy group, supercluster, universe. Each line sits inside the next, like boxes inside boxes.
Earth's cosmic address, from small to large:
Earth → Solar System → Milky Way Galaxy → Local Group → Virgo Supercluster → Laniakea Supercluster → Observable Universe
That's the list the Cosmic Address tool prints. Type your latitude and longitude, or let your browser fill them in, and it shows each of those seven levels with its size and the source for the number. The levels are the same for every person on Earth. What changes is the first line, your hemisphere. Your coordinates set the return label. The rest is the route everyone shares.
Our cosmic address in order, with sizes
Here are the seven lines the tool shows, smallest first. The sizes are the ones the tool displays.
| # | Level | Size the tool shows | What it is |
|---|---|---|---|
| 1 | Earth | 6,371 km (radius) | Our planet, third from the Sun |
| 2 | Solar System | 123 AU (to the heliopause) | The Sun and everything orbiting it |
| 3 | Milky Way Galaxy | 100,000 light-years across | Our galaxy, a barred spiral of 100–400 billion stars |
| 4 | Local Group | 10,000,000 light-years across | About 80 galaxies bound together, led by the Milky Way and Andromeda |
| 5 | Virgo Supercluster | 110,000,000 light-years across | Around 100 galaxy groups and clusters, including ours |
| 6 | Laniakea Supercluster | 520,000,000 light-years across | About 100,000 galaxies, mapped in 2014 |
| 7 | Observable Universe | 93,000,000,000 light-years across | Everything light has had time to reach us from |
One AU is the average distance from Earth to the Sun, 149,597,870.7 km. A light-year is about 9.46 trillion km. The jumps are uneven. From the Milky Way outward, each line is about 5 to 180 times bigger than the one before. Below that, the gaps are huge. The Solar System's edge is about 3 million times farther out than Earth's radius. And one light-year is about 63,000 AU, so the Milky Way is tens of millions of times wider than the Solar System.
Completing the cosmic address: the school question
A lot of people land here from a worksheet. The usual prompt reads something like: "Identify our place in the universe by completing the cosmic address. Earth, Solar System, Milky Way…"
The answer continues: Local Group, Virgo Supercluster, Laniakea Supercluster, Universe. Some older textbooks stop at "Local Supercluster" (another name for the Virgo Supercluster) and skip Laniakea, which was only named in 2014. Check which list your class uses.
What is the first line of our cosmic address?
It depends on where your list starts. If it starts at the planet, the first line is Earth. Many classroom versions start closer to home: your house, street, city, country and continent, then Earth. The tool starts at Earth and adds your hemisphere on top.
What is the third line?
Counting from Earth, the third line is the Milky Way Galaxy: Earth, Solar System, Milky Way. If your list starts with a street address, count down from there instead.
From large to small
Some lessons go the other way, the way a letter gets sorted: Universe, Laniakea Supercluster, Virgo Supercluster, Local Group, Milky Way, Solar System, Earth. Same address, read from the outside in.
The longer version: layers the short list skips
The seven-line version jumps straight from the Solar System to the whole galaxy. Astronomers can fill in a few more layers in between. The tool doesn't show these as their own lines, but they're real, and some lessons ask for them:
- Oort Cloud. A huge shell of icy bodies thought to surround the Sun, far beyond the planets. Nobody has seen it directly; long-period comets are the evidence. It's still held by the Sun's gravity.
- Local Interstellar Cloud. A wisp of gas about 30 light-years across that the Solar System is drifting through right now.
- Local Bubble. A thin, hot region about 1,000 light-years wide, likely blown out by old supernovae.
- Orion Arm. A minor spiral arm of the Milky Way, about 3,500 light-years wide. The Sun sits in it, about 26,000 light-years from the galaxy's centre, roughly halfway out.
So the full address reads: Earth, Solar System, Local Interstellar Cloud, Local Bubble, Orion Arm, Milky Way, Local Group, Virgo Supercluster, Laniakea, Universe. That's about as specific as anyone can get today.
Where does the Solar System end? It depends on what you count. The tool uses the heliopause, where the Sun's wind gives way to interstellar space. Voyager 1 crossed it in August 2012 at about 122 AU, and the tool lists 123 AU. The Sun's gravity reaches much farther, out through the Oort Cloud, thousands of times that distance.
How the Cosmic Address tool works
The tool runs on a short table of reference numbers, not a live astronomy feed. Most of the address doesn't change from day to day, so there's nothing to look up. The only part that depends on you is the hemisphere label:
- Latitude above 0 is the Northern Hemisphere. Below 0 is the Southern. Exactly 0 is the Equator.
- Longitude above 0 is the Eastern Hemisphere. Below 0 is the Western. Exactly 0 is the Prime Meridian.
Latitude must be between -90 and 90 and longitude between -180 and 180. Anything outside that isn't a place on Earth, so the tool shows an error instead of guessing.
A worked example. The page opens on the Royal Observatory in Greenwich, at latitude 51.4779 and longitude 0. Latitude is positive, so it's the Northern Hemisphere. Longitude is exactly zero, so it's the Prime Meridian. The banner reads You are here — Northern Hemisphere, the Prime Meridian, and the seven levels follow underneath.
A few more cities to try:
| City | Latitude, longitude | Hemisphere label |
|---|---|---|
| Tokyo | 35.6762, 139.6503 | Northern Hemisphere, Eastern Hemisphere |
| New York | 40.7128, -74.0060 | Northern Hemisphere, Western Hemisphere |
| Sydney | -33.8688, 151.2093 | Southern Hemisphere, Eastern Hemisphere |
| Buenos Aires | -34.6037, -58.3816 | Southern Hemisphere, Western Hemisphere |
| Quito | -0.1807, -78.4678 | Southern Hemisphere, Western Hemisphere |
Quito is a fun one. The city is famous for the Equator, but its centre sits just south of it, so the label says Southern.
Use my location asks your browser for your position. Your browser asks you first. The coordinates are rounded to four decimal places and only used to pick the hemisphere label. If you'd rather not share, type your city's coordinates instead.
Copy address puts a plain-text version on your clipboard, ready for a slide, a notebook or a message:
My cosmic address — Northern Hemisphere, the Prime Meridian:· Earth (6,371 km)· Solar System (123 AU)· Milky Way Galaxy (100,000 light-years)
…and so on, down to the Observable Universe.
Why the observable universe is 93 billion light-years wide
This is the number that surprises people most. The universe is about 13.8 billion years old, so how can we see farther than 13.8 billion light-years?
Because space kept stretching while the light was on its way. The oldest light we see left its source 13.8 billion years ago. Since then, expansion has carried that source to about 46 billion light-years away. That's the radius of what we can see in every direction. Double it and you get about 93 billion light-years. The universe beyond that edge almost certainly keeps going. We just can't see it, because its light hasn't reached us yet.
Using it in class, or just for perspective
A good lesson opener: have students write their street address, then their cosmic address, and compare the two. It works for science-fair boards and astronomy clubs too, and for the moment someone at dinner asks what Laniakea is.
Don't use it to give directions. "Laniakea Supercluster" won't get a taxi to your door. And the sizes are measurements, not fixed laws. They get sharper as telescopes improve, which is why each line in the tool shows its source.
For more of your place in the universe in human terms, see your age on Mars with Age on Other Planets. Or find what you'd weigh on Jupiter with Weight on Other Planets. Light Travel Since Birth shows how far light has gone since the day you were born. Back on Earth, the Sunrise/Sunset Calculator uses the same latitude and longitude for something more practical.
Frequently asked questions
What is Earth's cosmic address?
Earth, Solar System, Milky Way Galaxy, Local Group, Virgo Supercluster, Laniakea Supercluster, Observable Universe. That's from smallest to largest. Longer versions add the Local Interstellar Cloud, Local Bubble and Orion Arm between the Solar System and the Milky Way.
What is our galactic address?
Inside the galaxy, we live in the Orion Arm of the Milky Way, about 26,000 light-years from the centre. Outside it, the Milky Way belongs to the Local Group, in the Virgo Supercluster, inside Laniakea.
Is my location sent anywhere?
No. The hemisphere check runs in your browser. "Use my location" asks your permission, rounds the coordinates to four decimals and uses them only for the hemisphere label.
Why is the address the same for everyone?
Because everyone on Earth shares the same planet, star, galaxy and superclusters. Someone in London and someone in Sydney get different hemisphere labels, and every line after that is the same.
What is Laniakea?
The supercluster that holds the Milky Way and about 100,000 other galaxies, roughly 520 million light-years across. Astronomers defined it in 2014 by mapping which way galaxies are moving. The name is Hawaiian for "immeasurable heaven."
Why does the tool list both Virgo Supercluster and Laniakea?
Before 2014, the Virgo Supercluster was the biggest structure we were known to live in. The 2014 map showed it's one part of the larger Laniakea. Keeping both matches older textbooks and the newer picture.
Is this the same as the Voyager Golden Record map?
No, but it's the same idea. The Voyager record used 14 pulsars as beacons to point back to the Sun. This tool writes the address in words instead.