A 3D rendering of a swarm of meteorites or asteroids entering the earth's atmosphere. A 3D rendering of a swarm of meteorites or asteroids entering the earth's atmosphere. A 3D rendering of a swarm of meteorites or asteroids entering the earth's atmosphere. (Photo: Oliver Denker / Shutterstock)

Aliens might be hitching rides across the Milky Way, Harvard physicists say

Dr. Avi Loeb calls them 'tiny astronauts sitting in a natural spacecraft.'

The aliens are coming! The aliens are coming!

While a cowboy hat-wearing E.T. may not be riding the back of a comet as if it's a horse, something like that may actually be happening on a less cinematic scale.

Professor Avi Loeb, the chair of Harvard's Astronomy Department, has just published a study explaining how aliens can travel throughout the galaxy on the backs of everything from meteoroids to space dust. "Our paper considers the possibility that life could be transported across the entire Milky Way galaxy and beyond," Loeb said. "The solar system acts as a gravitational 'fishing net' that contains thousands of bound interstellar objects of this size at any given time. These bound interstellar objects could potentially plant life from another planetary system and in the solar system."

Think of it this way. Life exists throughout the universe. And those lifeforms – whether it's a tiny microbe or an alien species – can hitch a ride on a comet or an asteroid from one section of the galaxy to another. This theory is known as panspermia. Indeed, many scientists believe this is how life on our planet actually began. "The idea of panspermia is that life on earth did not originate on earth, but it came from somewhere else," said the University of Arizona's Dr. Jay Melosh, who was not involved in this study. Meaning, a life form from outer space rode the back of a comet which landed on earth, and planted the seeds for life here. Dr. Melosh explains in this video below:

The new study – which Dr. Loeb worked on with two of his post-doc students, Idan Ginsburg and Manasvi Lingam – was just published in The Astronomical Journal.

Dr. Loeb is an Israel-born theoretical physicist and graduate of Jerusalem's Hebrew University, a school that was founded by one of his heroes, Albert Einstein. Loeb is no stranger to alien study. He's devoted much of his career to looking outside our planet for answers. He's heavily involved with the Breakthrough Starshot Initiative, a $100 million program that is currently looking for alien life.

The Green Bank Telescope in the Allegheny Mountains of W. Virginia is the the world's largest fully steerable radio telescope. Dr. Loeb and the Breakthrough Starshot Initiative are using the Green Bank Telescope in West Virginia, the world's largest fully steerable radio telescope, to search for alien life. (Photo: Jamiev_03 / Flickr)

Along with many scientists, Loeb knows that humans' time on Earth is finite. The sun will eventually boil the oceans to the point where we'll have to find a new home. Or there could be a catastrophic asteroid. It won't happen tomorrow, or even in the next century. But he knows it will happen eventually. Habitable planets just outside our solar system have already been discovered. "We just need to think about the big picture and, you know, have a plan B."

To that end, Loeb and the other scientists at Breakthrough (Stephen Hawking was involved prior to his passing earlier this year) are trying to contact alien species to ask if we could move to their planet. Seriously.

"This will be the biggest leap forward since the Apollo mission. I like challenges," Loeb told us. "It's not fun otherwise."

If you want to hear Dr. Loeb explain his alien research, you're in luck. We traveled to his office on Harvard's campus, turned on a tape recorder and let him speak for nearly an hour about the ins and outs of life on other planets. You can listen to it here:

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Aliens might be hitching rides across the Milky Way, Harvard physicists say
Dr. Avi Loeb, the chair of Harvard's Astronomy Department, calls them 'tiny astronauts sitting in a natural spacecraft.'