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Collision Course: A Brief Guide to Earth's Most Interesting Impact Craters

A Norwegian family arrived at their cabin to open it up for the spring and found a surprise: a large rock had smashed through the roof. It was identified as a 1.3 pound breccia meteorite. It didn't hurt anybody, and its sale price should easily cover the damage to the roof; meteorites are valuable to collectors. But although most meteorites are very small, and to date nobody has been more than bruised by one, some of them are big and make a violent impression where they hit. Here are a few of the more interesting impact craters around:

Barringer Crater, Arizona, USA


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Also known as "Meteor Crater," this was the first crater identified, due to its relatively pristine appearance. It's young, as craters go -- just 50,000 years old -- and it was created by a nickel-iron meteorite about 50 meters across, excavating a crater about 1.2 km across.

Obolon' Crater, Poltava Oblast, Ukraine


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Not all craters are so obvious; sometimes their structure is only apparent in aerial views. Obolon' Crater was detected from the presence of shocked minerals in the surrounding, a tell-tale sign of an impact event. It's 20 km across and is estimated to be about 169 million years old, though there is some evidence it may be quite a bit older. (More on that next.)

Manicouagan Crater, Quebec, Canada


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Visible from space as a ring-shaped lake, this 100 km multi-ringed crater (with a 70 km central ring that is now Manicouagan Reservoir) was created by the impact of a 5km asteroid about 216 million years ago. What's interesting about this crater is that, if you account for plate tectonics and then roll the clock back about 216 million years, this crater has an eerily precise alignment with several other craters: Rochechouart in France, St. Martin in Manitoba, Obolon' in the Ukraine, and Red Wing crater in North Dakota. All of these craters may have been produced by a meteor train, the result of an object breaking up due to tidal forces or collisions.

Gosses Bluff Crater, Northern Territory, Australia


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What's left of this one is only 5 km across, but that's really only the central uplift that is found in some larger craters; the outer rim has mostly eroded away. This crater dates back about 142 million years. The local Aborigines regard it as sacred and, interestingly, give it an origin story hinting at its true origins: their story is that the child of the morning and evening stars fell out of the sky and hit the Earth in this spot; the shape of the bluff is evocative of its origin.

Karakul Crater, Pamir Mountains, Tajikistan


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This relatively young crater (between 5 and 25 million years old) is in Tajikistan and features a large lake at its center. The overall depression is 52 km across.

Sudbury Basin, Ontario, Canada


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This highly elliptical and also frighteningly large impact crater is difficult to see; it is shallow (the blow was a glancing one) and is heavily eroded and largely covered in vegetation. There is a large lake at one end, and the shape of it is crudely visible as human settlement has been mostly in the valley. The impactor would have been about 10-15 km in size, and struck the Earth about 1.849 billion years ago.

Vredefort Crater, Free State Province, South Africa


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Sudbury is big, but it's not the biggest. At 300 km across, Vredefort is the biggest confirmed impact crater on Earth. It's also the second oldest, at a little over 2 billion years of age. This impactor was probably 5-10 km, but traveling on a more direct course than the one that created Sudbury.

Chicxulub Crater, Yucatan, Mexico

This is not the largest crater on Earth, and you cannot see it at all from the surface. But it's one of the most famous, because this is the one widely suspected to have done in the dinosaurs. It's 180 km across, and the impactor is believed to have been at least 10 km across, striking Earth with a force of roughly 96 teratons of TNT. Geologic evidence indicates that the region was completely underwater at the time, and it would have produced a phenomenal tsunami.

[Gravity map created from public data by Milan Studio and released through Wikimedia Commons.]

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Space
Now You Can Train to Be an Astronaut on Your Smartphone
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Just because you don't work for NASA doesn't mean you'll never make it as an astronaut. In the world of private space tourism, a little training could be all you need. And there's an app for that.

Space Nation, a Finnish space tourism startup, recently launched Space Nation Navigator, which the company touts as the first astronaut training app in the world. The app aims to train future space travelers using games, quizzes, and fitness challenges that fall into three categories: "body," "mind," and "social."

Each of the challenges is tailored to help you develop the skills you'd need to survive in space—even the mundane ones. One mission is called "Did you clean behind the fridge?" and is designed to highlight the unpleasant chores crew members on the ISS have to do to keep things tidy. There are "survival" quizzes that test your knowledge of how to properly build a fire, read a map, and dispose of your poop in the forest. The app also plugs into your smartphone fitness data so that you can participate in athletic challenges, like a 650-foot sprint designed to train you to escape a meteor impact zone.

Screenshots of the Space Nation Navigator app
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"Space Nation Navigator offers a way for anyone, anywhere to have a 15-minute astronaut experience every day. These astronaut skills—team building, problem solving, positive life hacks—are not just vital to survive in space," Space Nation CEO Kalle Vähä-Jaakkola said in a press statement. "They are also crucial in your daily life."

New challenges are added to your queue every few hours, and you can compete against other users for high scores. If you get enough points, you can become eligible for real-life training experiences with Space Nation, including a trip to Iceland. In 2019, Space Nation plans to hold an international competition to find one astronaut that the program will send to space.

If you're going to start training, we suggest you take some of the tests Project Mercury applicants faced back in 1958 to see how you'd stack up against the first NASA astronauts.

Get it: iOS, Android

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Big Questions
If Earth is Always Moving, Then How Do We See the Same Constellations Every Night?
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Luis Medrano:

6700 mph is nothing in cosmological speeds and distances. Constellations are freakin’ far away.

Get in a car at night and drive on a straight road, then look at the moon. The angle of the moon in respect to your point of view doesn’t change; it seems like the moon is following you wherever you go. Meanwhile, things that are really close to you—like electric poles, roadside buildings, and trees—seem to fly by really fast.

The effect is known as parallax. Things that are close seem to move faster and “travel more distance” (not really) than things that are far away.

In the video above, there are several objects in perspective. The light in the center, which represents the sun, was placed so far away you can barely see it move.

The sun is only eight light-minutes away; that’s 146 million km on average. At human scale it seems like a lot, but in cosmic distances it is nothing. Orion, for example, has stars that are from 243 to 1360 light years away from us. Imagine traveling at the speed of light for 1360 years. That’s how far these stars are. And these are not even the farthest stars. Some stars are Giga-light years away from us.

Now, with the proper precision instruments you can indeed notice the parallax in distant stars, just not with the naked eye. Furthermore, our solar system has moved so much since the early days of astronomy and astrology, the constellations do not correspond to the early astrology maps. The constellations appear shifted.

As a free info nugget: In case your life is ruled by astrology, whatever sign you think you are, you are not.

This post originally appeared on Quora. Click here to view.

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