Whether you're a frequent jet-setter or a couch potato, you travel much more than you think.
In fact, that would be true even if you were to stay perfectly motionless your entire life. So how far, on average, does a person travel in their lifetime? The answer depends on whether you consider Earth as your vehicle.
As for distance on Earth's surface, the typical human will travel 30,000 to 50,000 miles (50,000 to 80,000 kilometers) in their lifetime, though some globe-trotters will go much farther. Considering most people accumulate the majority of this mileage from commutes and quick errands, that's an impressively large distance — enough to circumnavigate the globe at least once.
Related: How fast is Earth moving?
But as large as it is, that number pales in comparison to the motion we get simply by hitching a ride on Earth. Our planet spins on its axis. And because Earth is mostly solid, it rotates as a single rigid body, meaning that everywhere on the planet experiences the same angular speed and everyone travels a full circle every 24 hours.
But if you were to stand on the north or south geographic poles, you wouldn't actually travel anywhere; you would just spin around and around. Those on the equator, however, get a tremendous amount of linear speed thanks to this rotation — roughly 1,000 mph (1,600 km/h).
Most people don't live on the equator, however, so we can say that the average human is constantly traveling at roughly 930 mph (1,500 km/h). (As we will see, precision doesn't really matter here.) When you add that up over a roughly 80-year life span, each person travels around 600 million miles (1 billion kilometers) in their lifetime.
That's a tremendous leap above the travel we do on Earth's surface, but we're just getting warmed up. In addition to rotating, Earth orbits the sun. That orbit is an ellipse, which causes our planet to occasionally move more quickly or slowly depending on its distance from the sun. But on average, Earth's orbital speed is about 19 miles per second (30 km per second).
That's about 600 million miles (1 billion km) every year. So over a lifetime, each of us travels roughly 50 billion miles (80 billion km) — which, again, dwarfs the distance we travel due solely to the rotation of our planet.
But Earth is not the only object in motion in the universe. The sun travels in a long, lazy orbit around the center of the Milky Way galaxy. One of these "galactic years" takes roughly 230 million Earth years to complete. To put that into perspective, life first arose on Earth around 17 galactic years ago, and in only 25 more galactic years, the sun will die.
Compared with these enormous galactic scales, a human lifetime is barely perceptible, with the sun barely inching along its orbit. But on a human scale, it's almost incomprehensible; due to the motion of the sun orbiting the center of the Milky Way, each of us will travel around 370 million miles (600 billion km) in our lifetime.
And it doesn't stop there. Our entire galaxy is in motion, too. All galaxies are, on average, flying away from each other, but that's due to the expansion of the universe. On top of that expansion, each galaxy has some motion of its own — something astronomers dub "peculiar velocity." For example, the Milky Way is on a collision course with our nearest neighbor, the Andromeda galaxy. The mutual gravitational attraction is enough to overwhelm the general expansion of the universe, and in about five billion years, these galaxies will begin to merge.
On top of that, both the Milky Way and Andromeda are headed toward the Virgo cluster, a massive cluster of galaxies about 65 million light-years away. Beyond that, the Virgo cluster and its surrounding galaxies are all headed toward the Great Attractor, which is the center of our supercluster, called Laniakea.
Astronomers can calculate the combined motion of these gravitational influences by observing the cosmic microwave background (CMB), which is composed of radiation released when our universe cooled from a plasma state when it was only 380,000 years old. It completely soaks the universe and is the same to one part in a million across the entire sky.
Any motion in the universe will be visible in the CMB. Light in the direction we're headed in will get Doppler-shifted to higher frequencies (blueshift), and light in the direction we're moving away from will be shifted to lower frequencies (redshift). By measuring this shift, astronomers can calculate our total velocity through the universe, and those measurements give a number of around 390 miles per second (630 km per second).
When you add that up over an 80-year life span, it gives you a total movement of 930 billion miles (1.5 trillion km). Even if you never leave home, you will still travel that enormous distance — that's quite an accomplishment!
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Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute in New York City. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in 2011, and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe to the earliest moments of the Big Bang to the hunt for the first stars. As an "Agent to the Stars," Paul has passionately engaged the public in science outreach for several years. He is the host of the popular "Ask a Spaceman!" podcast, author of "Your Place in the Universe" and "How to Die in Space" and he frequently appears on TV — including on The Weather Channel, for which he serves as Official Space Specialist.
So in one lifetime you will travel 1/5th of a lightyear.Reply
Don't forget TIME. We are change travelers at the constant of the speed of light emission as well as space travelers, therefore we are time travelers too.Reply
Regarding the length of a human life span, you can measure a brain top to bottom, side to side, outside-in and inside-out, and beginning to end, but just try measuring a quantum entangled, entangling, mind (the "infinity of the mind" (even someone's, some being's, closed mind, shrinking mind, ego, id, matching their non-frontier closed universe view)). The body may go away, but the mind, however tied to the universe at large (enlarging minds) and/or small (shrinking minds), doesn't.
The premise of this article is a bit silly. You'll travel an arbitrarily large amount if you pick the right rest frame. Or an arbitrarily small amount (zero in your own rest frame). And the author knows this. The author wants to treat the rest frame in which the CMB is isomorphic as a privileged frame, but one of the most basic cardinal rules of GR is that there is no privileged frame.Reply
Another dozen years and I'll have done my 1.5 trillion kms. Now I know why I'm constantly tired, always on the move.Reply
So, if my math is correct, at any given moment we are traveling at around 1,327,000 mph? I tried to figure this out a few years ago but couldn't find the speeds of sun, galaxy, expansion, etc. to do the math.Reply