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Hagai Perets

Astronomers: Multiple Cosmic Collisions May Have Created Our Moon

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Hagai Perets

It looks so tranquil up there. So still. But we know space is neither tranquil nor still. Our own Moon is no exception. New research suggests the Moon was the product of some very, very violent moshing: Around 4.5 billion years ago, a rowdy gang of stellar objects smashed into our young planet, creating the debris that would one day become the Moon. The astronomers published their report in the journal Nature Geoscience.

We’ve known for a while now that the Moon is made at least partially out of pieces from a banged-up Earth. But we’re still trying to sort out the details of the collision itself. At first, scientists thought Earth had been hit by one big object, like another planet. Then they thought there must have been a bunch of objects all striking around the same time. As we learned more, the single-impactor theory returned to prominence and stayed there for decades.

One 2016 study named the object—the planet Theia—and even the angle of impact. The researchers theorized that the extremely similar molecular makeup of Earth and the Moon could only have resulted from a head-on collision.

Other astronomers disagree. The authors of the new paper ran hundreds of simulations, and they argue it’s far more likely that Earth was walloped by a score of different objects called planetesimals. Each of the repeated impacts smashed up a huge amount of the young planet’s matter. That debris then drifted into orbit around Earth, where it settled into disks, which then resolved into little (gargantuan) chunks called moonlets. Over time, the baby moonlets merged into one single, spinning rock.

“Our model suggests that the ancient Earth once hosted a series of moons, each one formed from a different collision with the proto-Earth,” co-author Hagai Perets said in a statement. “It’s likely that such moonlets were later ejected, or collided with the Earth or with each other to form bigger moons.”

Perets says the moonlets could easily have crossed orbits with one another, smashed together, and been rolled up into larger bodies. “A long series of such moon-moon collisions could gradually build-up a bigger moon—the Moon we see today.”

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Stare All You Want at These Photos of the Solar Eclipse
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George Frey/Getty Images

It’s Superman’s worst nightmare: the complete disappearance of the Sun from our perch on Earth. For non-Kryptonians, it’s a rare and awesome chance to see a unique spectacle that hasn’t happened for 99 years. Multitudes gathered Monday to observe the solar eclipse, a complete obstruction of the sun’s rays by the moon in an epic galactic photo-bombing. Here’s how stargazers across the country greeted the astronomy event.

Artist Orion Fredericks created this art installation, 'Exsucitare Triectus,' for the public at the Oregon Eclipse Festival in Ochoco National Forest.
Image Credit: ROBYN BECK/AFP/Getty Images

Twitter user Doug McArthur of Portland finds a novel way of avoiding direct eye contact.

Observers at Cal State Fullerton utilize a USPS-approved method for observing the eclipse safely.

That tiny little blemish isn't a bug on your screen: It's the International Space Station transiting the sun during the eclipse.

Pictured: an unidentified man and Zuul, Gatekeeper of Gozer.

The 'diamond ring' effect as seen from the Lowell Observatory in Madras, Oregon.
Image Credit: STAN HONDA/AFP/Getty Images

Another novel way to avoid retina damage while enjoying the spectacle.

Through a portal in Kansas City, Kansas.

Boston gets its view of the celestial sensation.

The safest way to be in awe.
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Here’s Why You Should Skip Selfies During the Solar Eclipse
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Following decades of hype, the Great American Eclipse will finally pass over the contiguous United States on Monday, August 21. If you’re one of the millions of people who will be watching the event, you may be tempted to document it with a quick over-the-shoulder selfie. But even if you’re facing away from the sun, using your phone to photograph it can still do damage, as Gothamist reports.

A viral post that recently circulated on Facebook instructs anyone without protective eyeglasses to view the eclipse live by filming it through their phone’s front-facing camera. Retina expert Tongalp Tezel, MD of Columbia University Medical Center explained to Gothamist why this is a bad idea: “What they may not realize is that the screen of your phone reflects the ultraviolet rays emitted during an eclipse directly toward your eye, which can result in a solar burn."

The power of the sun shouldn’t be underestimated, as NASA has warned people repeatedly in the weeks leading up to the eclipse. The rays that peek out when the sun is 99 percent covered are still enough to fry your retinas' delicate tissue and inflict lifelong damage. And your eyes aren’t all that's at risk—the lens of your camera, whether it’s part of a smartphone or not, also needs to be protected if you plan on pointing it at the eclipse.

If you’ve already secured a solar camera filter and ISO 12312-2-certified glasses, then you should have no trouble witnessing the phenomenon safely. But even without the proper eyewear there are plenty of ways to experience the eclipse without exposing your eyes to direct sunlight. And if you forgot to pick up a camera filter, that's a good excuse to watch the event unplugged.

[h/t Gothamist]

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