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What Would Happen if Everyone Jumped at Once?

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Something would definitely happen—but it wouldn't be a big something.

As mass moves towards the center of a rotating object, the rate of rotation increases. Imagine, for example, an ice skater pulling her limbs in to increase the speed of spinning. So, technically, you can make the Earth rotate more rapidly all on your own simply by crouching down on the ground—but at a totally negligible amount.

Powerful earthquakes can redistribute mass in a slighter more impactful—but still ultimately negligible—way. The earthquake in Japan in 2011 moved so much mass toward Earth's center that every day since has been 0.0000018 seconds shorter. However, if we tried to recreate the force of that earthquake simply by jumping, we'd would need seven million times more people than currently live on Earth.

But what about all of us in one place pushing down on the earth as we jump away from it? If everyone in the world stood shoulder-to-shoulder, we could all fit into a space the size of Los Angeles—that’s more than seven billion people packed into 500 square miles. But even if we all jumped at once in that small area, not much would happen. Our collective mass is an awful lot—just not compared to the mass of the Earth.

Let’s assume we all jump 30 centimeters. Our force would propel Earth away from us, but not very far at all. Earth would only move away from us 1/100 of the width of a single hydrogen atom. Additionally, just as we would return to our original starting position on Earth, the Earth would return to its original position in the universe. No lasting effects here.

Over on YouTube, VSauce covered this topic in more detail. Watch his explanation:

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This Organization Wants Your Old Eclipse Glasses
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On Monday, August 21, America hosted what may have been the most-viewed solar eclipse in history. While those of us in the United States are still processing the awesome sight, residents of South America and Asia are just starting to look forward to the next total eclipse in 2019—and anyone who still has their protective glasses on hand can help them prepare.

According to Gizmodo, Astronomers Without Borders is accepting donations of used eyewear following Monday’s event. Any glasses they collect will be redistributed to schools across Asia and South America where children can use them to view the world’s next total eclipse in safety.

Astronomers Without Borders is dedicated to making astronomy accessible to people around the world. For this most recent eclipse, they provided 100,000 free glasses to schools, youth community centers, and children's hospitals in the U.S. If you’re willing to contribute to their next effort, hold on to your specs for now—the group plans to the announce the address where you can send them in the near future. Donors who don't have the patience to wait for updates on the group's Facebook page can send glasses immediately to its corporate sponsor, Explore Scientific, at 1010 S. 48th Street, Springdale, Arizona 72762.

Not sure if your glasses are suitable for reuse? Here’s the criteria they should meet for sun-gazing.

[h/t Gizmodo]

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Here's How to Tell If You Damaged Your Eyes Watching the Eclipse
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Amid the total solar eclipse craze, experts repeatedly warned spectators not to watch the rare phenomenon on August 21 with their naked eyes. But if you caught a peek sans glasses, pinhole projector, or protective filter, you may be wondering if your peepers were damaged. (After the sky show, "my eyes hurt" spiked as a Google search, so you’re not alone.)

While the sun doesn’t technically harm your eyes any more than usual during a solar eclipse, it can be easier to gaze at the glowing orb when the moon covers it. And looking directly at the sun—even briefly—can damage a spot in the retina called the fovea, which ensures clear central vision. This leads to a condition called solar retinopathy.

You won’t initially feel any pain if your eyes were damaged, as our retinas don’t have  pain receptors. But according to Live Science, symptoms of solar retinopathy can arise within hours (typically around 12 hours after sun exposure), and can include blurred or distorted vision, light sensitivity, a blind spot in one or both eyes, or changes in the way you see color (a condition called chromatopsia).

These symptoms can improve over several months to a year, but some people may experience lingering problems, like a small blind spot in their field of vision. Others may suffer permanent damage.

That said, if you only looked at the sun for a moment, you’re probably fine. “If you look at it for a second or two, nothing will happen," Jacob Chung, chief of ophthalmology at New Jersey's Englewood Hospital, told USA TODAY. "Five seconds, I'm not sure, but 10 seconds is probably too long, and 20 seconds is definitely too long."

However, if you did gaze at the sun for too long and you believe you may have damaged your eyes, get a professional opinion, stat. “Seeing an optometrist is faster than getting to see an ophthalmologist,” Ralph Chou, a professor emeritus of optometry and vision science at the University of Waterloo, in Ontario, Canada, told NPR. “If there is damage, the optometrist would refer the individual to the ophthalmologist for further assessment and management in any case.”

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