Forbidding Planet: Scientists find remains of monster asteroid impacts on early Earth

Artist’s view of Earth several billion years ago during the Late Heavy Bombardment, when the planet is thought to have been battered by impacts of comets and asteroids. Credit: Chris Butler/SPL

Earth 3.5 billion years ago was a terrifying place. Picture a rocky landscape pounded by meteorites and asteroids with a surface resembling that of the moon. Volcanoes spewed water vapor but also a toxic mix of carbon dioxide, sulfur dioxide and methane. If you could whisk yourself back to this world by time machine, you’d need to be fully protected by a spacesuit and lucky enough to not get picked off by a falling space rock. Oh, and bring a boat too. Hot-water oceans likely covered a fair portion of the planet back then.


This time-lapse illustration of the Nice (pronounced ‘neece’) model of solar system evolution shows how outer planet migrations kick asteroids into the inner solar system

Scientists call the period from about 3.8 billion to 1.8 billion years ago the Late Heavy Bombardment (LHB), a time when the number of asteroids and their fragments pelting the inner planets and their moons spiked. Why then? No one’s absolutely certain, but the leading theory posits that the migration of the giant outer planets to their present positions “stirred the gravitational pot”, slinging boatloads of asteroids into the inner solar system, where they rained down on Earth and its neighbors in hellish monotony for millions of years.

Anyone with a small telescope can see resulting devastation to this day. Just take a long look at the moon’s battered and cratered surface and thank your lucky stars you’re around during a more peaceful time. Finding Earth’s craters is trickier because water and wind erosion, along with the continual recycling of much of our planet’s crust through plate tectonics, has erased much of our violent past.

The Vredefort Dome – these concentric hills, which rebounded after the impact that created Vredefort Crater – are what remains after an asteroid about 3-6 miles wide struck Earth 2 billion years ago. Credit: NASA

About 180 craters are known on Earth today, but we’re aware of only three resulting from the Late Heavy Bombardment. The oldest, estimated at 3 billion years old and 62 miles (100 km) wide, is also the most recently discovered. Found in western Greenland in 2012, all that remains of the impact are rocks rattled by the massive shock wave that penetrated 15 miles (25 km) deep within Earth’s crust.

You can still see the remains of the impacts that formed the 112-mile-wide (180 km) Vredefort Crater in South Africa, which is 2 billion years old, and the youngest LHB member, the 155-mile (250-km) Sudbury crater in Canada dated at 1.85 billion years.

Map of South Africa with the Barberton greenstone belt shown in red. Shock waves from the impact of an asteroid 3.26 billion years ago created telltale formations within the belt. No one knows yet where the impact happened.

Now, a group of scientists have announced they’ve found evidence for an even older impact, one that occurred 3.26 billion years ago and left its signature in a South African region known as the Barberton greenstone belt.

A recent press release describes the huge impactor as between 23 and 36 miles wide (37- 58 km). Colliding with the planet at 12 miles per second, the jolt delivered was bigger than a 10.8 magnitude earthquake and propelled seismic waves hundreds of miles through the Earth, breaking rocks and setting off other large earthquakes. Tsunamis thousands of feet deep swept across the oceans that covered most of the planet at that time.

A graphical representation of the size of the asteroid thought to have killed the dinosaurs (left), and the crater it created, compared to an asteroid thought to have hit the Earth 3.26 billion years ago and the size of the crater it may have generated. A new study reveals the power and scale of the event some 3.26 billion years ago which scientists think created geological features found in a South African region known as the Barberton greenstone belt. Credit: American Geophysical Union

“We knew it was big, but we didn’t know how big,” Donald Lowe, a geologist at Stanford University and a co-author of the study, said of the asteroid.

The collision would have blasted out a crater some 300 miles (500 km) wide, filled the atmosphere with fiery rock vapor and set the surface of the ocean a-boil. We’re talking serious cataclysm. Somehow life found a way through the heat and crater-punching to gift us with the rolling green hills, coral reefs and forests that characterize Earth today.

Table from the book “Near Earth Objects – Finding Them Before They Find Us” by Donald Yeomans showing average asteroid impact results and probabilities by size. Credit: Donald Yeomans

I try to imagine the dark days of the LHB to help me appreciate these calmer times. Yet we know in our gut – and in fact, thanks to probability – that we’ll never truly be out of the woods. Asteroids lurk in the deep that could one day cause a similar scenario. Don’t let it worry you too much – the chance of a 10-mile-wide space rock striking Earth is once every 89 million years. You’ve still got time to take a nap, catch a show and enjoy a few nights out on the town. Probably.

Happy equinox! Time to tip your hat to Earth’s tipped axis

One of the earliest of spring flowers, a crocus blooms on a sunny spring afternoon. Credit: Bob King

Such a beautiful flower. Look as hard as you like and you won’t find a single one in my town where more than two feet of snow still blankets the good brown earth. I’m not worried. Two weeks from now, the spring sun will reduce it all to puddles.

Today’s the vernal equinox, the start of spring in the northern hemisphere. It began at 11:57 a.m. CDT, the instant the center of the sun’s blazing disk crossed the imaginary circle in the sky called the celestial equator. If you live on the real equator, the celestial version passes directly overhead. That means no shadows at noon today for residents of places like Quito, Ecuador and Kampala, Uganda.


North Pole webcam 2013

Travel north of the equator and the celestial equator drops lower and lower in the southern sky. At the north pole, it sits exactly on the horizon 360 degrees all around. If you could stand there today, you’d be seeing your first sunrise since the autumnal equinox last September. It would also be the start of six months of uninterrupted daylight. By the way, the weather’s fantastic there today – sunny with a high of 24 degrees!

Because of the 23.5 tilt of Earth’s axis, the altitude of the sun varies cyclically across a year. In winter it’s 23.5 degrees below the celestial equator, while in summer it’s 23.5 degrees above. At the equinoxes, it straddles the equator. Created with Stellarium

Most of live between the pole and equator, where the sun stands roughly halfway up in the southern sky at local noon. That’s a far cry from winter, when the sun stood 23.5 degrees (a little more than two fists held at arm’s length) below the equator. Its rays were less direct and intense, and the time it spent above the horizon relatively brief, the two key factors that make a winter.

In summer, we experience just the opposite. The sun stands 23.5 degrees above the celestial equator; its rays are more direct and it spends many more hours above the horizon. Long days and short nights are a delight for many  … including the bugs.

The sun’s cyclic journey above and below the celestial equator all goes back to Earth’s tipped axis. As Earth travels around the sun in a year, the north polar axis tilts toward the sun in summer, taking it 23.5 degrees above the equator, and away from the sun in winter for a ride 23.5 degrees below the equator.

The tip of Earth on its axis causes the seasons. On the first day of spring or vernal equinox, the axis is perpendicular to the sun and days and nights are equally long in both northern and southern hemispheres. Notice the axis doesn’t “flip-flop” but remains pointed in the same direction. It’s the Earth’s orbital travel that causes it to point toward and away from the sun. Credit: Tao-olunga with my own additions

On the first days of spring and fall, the axis is oriented neither toward nor away from the sun. Day and night across the planet are paired up at 12 hours apiece. After today, daylight slowly gains the upper hand by 2-4 minutes a day. Doesn’t sound like much, but like snow, it quickly adds up. By June the mid-latitudes will have gained some four additional hours of solar photons.

What spring looks like where in Duluth this season – a high sun but plenty of snow to go around. Photo taken March 16, 2014. Credit: Bob King

You’ve probably heard that you can balance an egg on its end on the first days of spring and fall. Like water going down the bathtub drain in different directions depending on your hemispher this is an urban myth. It’s hard to balance an egg ANY time of year. Just try it.

I think we all relate to the new season for the same reasons generations of humans before us have. Rebirth, renewal and the return of warmth and light capture the essence of spring. We tip our hats to the random impact at the dawn of the solar system that set Earth’s axis askew.

Daylight forces the hand of night as we surge toward spring

Animation showing the Earth – with tipped axis – revolving around the sun. Seasons are shown for the northern hemisphere.

It happens every mid-winter. I wake up earlier and earlier, unconsciously responding to the daylight that spills beneath the window shade as the pace of the season quickens.

We’ve been putting seconds and minutes in our sunny-day piggy bank every since the winter solstice last Dec. 21. Those deposits are now accumulating rapidly as February gives way to March. Where I live, days were as short as 8 hours 32 minutes in late December. Today that time has swelled to 10 hours 24 minutes.

As Earth revolves around the sun, its 23.5 degree-angled axis points toward, perpendicular to and away from the sun over the year to make the seasons. Credit: Tao’olunga with additions by B. King

While a half hour of extra light may not be enough to notice, 1 hour and 52 minutes is a revelation. Many of us now drive home in bright twilight at the end of a work day. This has beneficial effects like seeing more sunsets and full moon rises. We also feel more connected with the world because we can see it. Humans weren’t born to live as troglobites in dark caves. We crave sunlight as much as clear,dark nights.

I like the extra daylight for hiking and skiing. Shorter nights also mean less time for the Earth to loose heat and the temperature to dip below zero. If you’d like to see how your day/night account is coming along, check out the UNSO’s Duration of Daylight/Darkness Table.

All things warm and fuzzy (and cold and spiky) come our way because of Earth’s axial tilt. The axis remains fixed at an inclination of 23.5 degrees, but as the planet revolves about the sun during the year, the northern hemisphere tilts toward the sun in summer and away in winter. These are the extremes. In between, we have the spring and fall equinoxes, when both hemispheres are “face on” to the sun and receive equal amounts of daylight and night.

There are mini-seasons too. Mid-February is as good a time as any to call by that name. We’re moving away from winter toward spring with night on the run and daylight gaining the upper hand. A month from today, on the verge of the spring equinox, daylight will have increased an additional 1 1/2 hours to 12 hours. For a moment day and night will balance. The next moment day surpasses night and won’t relinquish its lead until after the fall equinox.

The sun’s always high in the sky at low tropical latitudes, so the seasons don’t vary much. This diagram shows the sun’s position around noon on the winter and summer solstices and equinoxes. Stellarium

Daylight length depends upon your latitude. If you took a tropical vacation this winter, you probably noticed that the sun rose around 6 a.m. and set around 6 p.m. Closer to the equator, the sun’s path is steeply inclined to the horizon every day of the year with little change in sunrise and sunset times. The sun’s always high in the sky there at the noon hour, bringing with it those consistently warmer temperatures we’re willing to pay big bucks for.

A mid-winter sun shines through an icicle formation on Lake Superior. Credit: Bob King

At mid and high latitudes, the yearly variation in sun’s position in the sky puts it high in the sky during summer and low in the sky during winter. Low means less time above the horizon, shorter daylight hours and cold temperatures.

To better understand this, consider that on the first day of spring and fall on the equator, the sun rises due east, passes directly overhead and sets due west. On the first day of summer, the sun at noon passes 23.5 degrees ( a little more than two fists held at arm’s length) north of the overhead point, while on the winter solstice it’s 23.5 degrees south of overhead. No matter the season, the sun will always shine down from a high altitude at noon.

This view shows the sun from a mid-northern latitude city like Minnepolis, Minn. Notice how the sun’s yearly elevation spread take it much closer to the horizon (wintertime) and also quite high (summertime). The scale of this map is different from the one above because it doesn’t need to include as much sky near the overhead point. Stellarium

In Minneapolis, halfway between the equator and north pole at latitude 45 degrees north, the sun is 45 degrees high at noon on the first day of spring and fall or halfway between the overhead point and southern horizon. Come the first day of summer, it’s way up there at 68.5 degrees and roasts the back of your neck, but on the winter solstice it peaks out at just 21.5 degrees high. Better protect that neck with a scarf.

The full range of the sun’s yearly motion – 23.5 degrees north to 23.5 degrees south of the celestial equator – is the same no matter where you are on Earth, but if you live far from the equator, the sun’s altitude reaches greater extremes, making the seasons more pronounced.

Curiosity rover snaps 1st photos of Earth and moon from Mars

Earth is the brightest “star” in Mars’ western evening sky as seen and photographed by the Curiosity Rover on Jan. 31, 2014. As seen through Martian eyes, Earth is in the constellation Pisces near its brightest star Al Rischa. Click to enlarge. Credit: NASA/JPL-Caltech/MSSS/TAMU

How many people can you fit inside a pale blue dot? Try 7 billion. We’re all there along with nearly 9 billion other species in these first photos ever taken of planet Earth by the Curiosity rover.

In this scene, the inset photo shows enlarged view revealing the fainter moon close by. Click to enlarge. Credit: NASA/JPL-Caltech/MSSS/TAMU

The pictures were made on Jan. 31, 2014 from the sandy dunes of Dingo Gap inside Gale Crater and show the Earth setting in the evening sky over the crater’s rim. If you could be there in person, the home planet would appear as a pale blue “star” shining at magnitude -1, a little fainter than Sirius, the brightest star in the skies of both planets.

Standing on the ground next to Curiosity’s location at 4.5 South latitude an observer would face west during twilight this evening to see a brilliant blue Earth in the constellation Pisces. Click to learn more about Earth in the Martian sky. Stellarium

The moon would also be visible very close to the planet and much fainter at around magnitude 2.7. Observers with keen vision might see the two tightly-spaced worlds with the naked eye, but a pair of binoculars would come in handy for most of us.

Earth in a telescope in early February as seen from Mars. Stellarium

If you happened to pack your telescope along and pointed it at Earth, you’d be delighted to see our planet as a thick crescent and near its greatest brilliancy. Because Earth orbits the sun inside Mars’ orbit, it passes through phases exactly like Venus and Mercury do as seen from Earth.

These aren’t the first photos of Earth from Mars. The Spirit Rover took a portrait of the home base in 2004 and NASA’s Mars Global Surveyor did the same in 2003 and Mars Reconnaissance Orbiter in 2007.

Every one of these images is a great treasure. They remind us that Earth swims in a cosmos vast beyond imagination.

Time exposure photo of the starry sky taken by Curiosity on Jan. 31, 2014. Do you recognize any? Click to enlarge. Credit: NASA/JPL-Caltech/MSSS/TAMU

The view inside Gale Crater from sandy Dingo Gap yesterday Feb. 6, 2014. Credit: NASA/JPL-Caltech/MSSS/TAMU

Rise and shine! Yutu wakes up / New photos of Earth from the moon

Planet Earth seen from the moon photographed by the Chang’e 3 lander on December 24, 2013 at 12:15 p.m. CST. No stars are visible because the picture was exposed to capture the bright Earth. To record stars, the Earth would have been greatly overexposed. Credit: Chinese Academy of Sciences

The Chang’e 3 moon lander and Yutu rover got their way up call this weekend. Roused from hibernation after more than two weeks chilling in the long lunar night, they’re back in business taking pictures and examining the moon’s crust and minerals.

With temperatures dipping to -292 F (-180 C) and no sunlight to generate electricity with their solar panels, mission control powered down the pair on December 26. The sun will shine over rover and lander for another two weeks until setting again on Jan. 25.

Earth’s plasmasphere photographed in far ultraviolet light by the lander camera on December 16, 2013. The plasmasphere is the inner part of Earth’s vast magnetic bubble called the magnetosphere and consists of dense, cold plasma or ionized atoms and molecules. Click to learn more. Credit: Chinese Academy of Sciences

We’ve seen precious few quality, high resolution images yet from the mission – most have been screen-grabbed off TV and video. Here are few new ones, including a couple featuring a favorite planet.

360-degree panorama of the landing site around the landing site taken by the Chang’e 3 lander on Dec. 17 and 18, 2013. Multiple images have been combined to create the view. Click to enlarge. Credit: Chinese Academy of Sciences

360-degree panorama around the Yutu rover. Click to enlarge. Credit: Chinese Academy of Sciences

 

Chang’e 3 lander photographed by the Jade Rabbit “Yutu” rover on Dec. 16, 2013. Click to enlarge. Credit: Chinese Academy of Sciences

Merry Christmas to all, and to all a clear night!

Ornament hanging from a Christmas tree? Cassini peers up at Saturn’s south polar region from 44 degrees beneath the ring plane last July. The black, curved stripes are the shadows of the rings on the planet’s atmosphere. Credit: NASA/JPL

Merry Christmas everyone! It’s been a joy to share the sky with you the past year. Thank you for sharing your comments, observations and photos. I hope this day finds you with family, friends and maybe even the stars.

We’ll soon step into a brand new year filled with eclipses – two lunars and a partial solar – an extremely close conjunction of Jupiter and Venus, a Mars opposition and much more. In a couple days I’ll have a complete month-by-month list of upcoming astronomical highlights.

Seen from STEREO-B, Earth, Jupiter and Venus line up inside a 2-degree-wide circle in conjunction on Dec. 24. Jupiter and the Earth were especially close – just 0.4 degrees or slightly less than one full width apart. Credit: NASA

Did you know that today the Earth is in conjunction with Venus and Jupiter today? Too bad you have to floating in outer space to see it. NASA’s STEREO-B probe, which looks back toward Earth from the opposite side of the sun, photographed a very compact grouping of the three worlds on Christmas Eve.

The three planets early this Christmas morning as seen by STEREO-B. Credit: NASA

Today they’re still very close with Jupiter practically on top of Venus. Coincidentally, a similar near-overlap of the two planets (as seen from Earth) on June 17, 2 B.C. was one possibility for the famed Star of Bethlehem we explored in yesterday’s blog.

Winter solstice offers hope in our darkest hour

Ah, winter. Water dripping from a building rooftop in downtown Duluth grew into a shape resembling a perched bird this week. Credit: Bob King

The nights are long. You never seem to warm up. It must be winter. Or it will be anyway at 11:11 a.m. (CST) tomorrow Dec. 21 when the sun bottoms out in its yearly circuit of the sky like a cigarette crushed in an ashtray.

But every winter solstice has a silver lining; after tomorrow the sun begins moving northward again, chipping away at the darkness as it rises higher with each passing day.

Winter takes getting used to which is why we still call it fall in November and much of December. By the time the solstice rolls around on the 21st, we’ve long accepted the cold, snow and driving home at 5 with the headlights on.

The fundamental facts of life all revolve about the tilt of Earth’s axis. If our planet rotated straight up and down like Mercury, we’d have no seasons. Mid-latitudes would experience eternal spring with the sun forever stuck halfway between its summer high point and winter low. Some of you might like this … for a while.

The Earth’s tilt combined with its yearly revolution of the sun tip the northern hemisphere toward the sun in summer and away in winter. Credit: Tao’lunga / Wikipedia with my annotations

Meanwhile, those living at the equator would see the sun directly overhead at noon every day of the year, while  polar explorers and researchers would watch it skirt the horizon and never rise higher. For everyone the sun would rise and set at nearly the same time every day.

The sun’s noontime elevation changes from season to season thanks to the 23.5 tilt of the Earth’s axis. Stellarium

But no. The 23.5 degree tip of the Earth’s axis combined with our planet’s revolution around the sun break the monotony and create the seasons. The tilt ensures that the northern hemisphere of the planet nods toward the sun in summer and away in winter when we’re on the other end of our orbit.

Ethel O’Leary of Duluth deals with the consequences of Earth’s tilted axis as she clears the sidewalk in front of her house Dec. 5, 2013. Credit: Bob King

As a result of that nod, the sun appears high in the sky in summer. Its longer, steeper path across the sky means longer days and more intense heat. In the winter, the northern hemisphere “leans back” from the sun. Slanted, less intense solar rays and short days follow.

On Dec. 21 the sun reaches its lowest altitude above the southern horizon at noon for the year. Here in Duluth, that’s about 20 degrees or two fists held at arm’s length. For Chicagoans, it’s 25 degrees, a bit higher. But if you live in Anchorage, the solar disk climbs to just under 6 degrees before slinking back toward the southwestern horizon.

The sun’s path during the year hits a low in winter and a high in summer. Around the winter solstice, the sun travels little in the northward direction and appears to “stand still” in the sky. The same happens at the summer solstice. Come late January,the sun’s path is more steeply inclined to the horizon and it moves northward and higher in the sky. Longer days result. Credit: Dr. John Lucey, Durham University

Solstice literally means “sun stands still” and refers to the fact that around the solstice sunrise and sunset times change very little and the sun seems stuck in the same low spot in the sky. In December the sun sits at the “bottom” of its yearly path around the sky. Most of its daily motion is to the east and very little to the north. For the sun to get higher in the sky (and days to grow longer), it needs to spend more time moving “upward” or to the north. That starts happening in late January and accelerates during the spring when the sun’s path is more steeply angled to the horizon.

We’ve spent the last three months watching the sun glide to the cold bottom of the celestial sphere. Beginning tomorrow there’s nowhere to go but up. The next time you grab that snow shovel and heave a chunk of winter over the bank, know that the sun – starting tomorrow afternoon – will be on your side.

Spectacular new images of Saturn’s rings with Earth, Mars and Venus

Cropped view of the new natural color Saturn pictures by Cassini showing Earth and the moon. Click for complete version. Credit: NASA/ JPL-Caltech/SSI

Stop it NASA, you’re killing me. More amazing Cassini pictures of Earth seen from Saturn? Yes! The agency released new photos in natural color today showing the ringed planet backlit by the sun and accompanied by seven of its moons, Venus, Mars and the Earth.

“In this one magnificent view, Cassini has delivered to us a universe of marvels,” said Carolyn Porco, Cassini’s imaging team lead at the Space Science Institute in Boulder, Colorado.

Full view of Saturn, its rings, seven moons and three planets shot by Cassini on July 19, 2013. Click for giant version.

141 individual images were assembled into a high-resolution mosaic that with one click will fill your entire screen. The final result sweeps 404,880 miles (651,591 km) across Saturn and its inner ring system all the way out to the E ring, the planet’s second outermost ring.

The E ring shines like a halo around Saturn and the inner rings. Because it’s so tenuous, it’s best seen with light shining from behind it the same way sunlight illuminates your breath on cold mornings. Geyser-like sprays of ice particles from the moon Enceladus (left side of hi-res image) continually resupply the ring; you can even see the sprays by zooming in.

Cropped portion of the photo shows Mars and Venus as starlike points of light above and below the E-ring. The moon Janus and associated Janus ring are also shown. Click to enlarge. Credit:

All the photos were taken during the July 19 “Wave at Saturn” campaign when earthlings waved and shouted “cheese” at Cassini as it snapped pictures for the panorama almost 900 million miles away. While beautiful to look at, the image also provides scientists with a bonanza of information about ring structures only visible when the sun shines through them instead of reflecting off the rings.

“The E ring in particular shows patterns that likely reflect disturbances from such diverse sources as sunlight and Enceladus’ gravity,” explained Matt Hedman, a Cassini participating scientist at the University of Idaho in Moscow. Curious clumps are also seen in the A-ring near the bottom of the mosaic.

Click HERE to relish several versions of the new Saturn images and learn more about what they reveal.

(Note to class: We are “GO” 4:30 a.m. Weds. Nov. 13 for Comet ISON viewing!)

Cassini releases 1,400 image mosaic of Earth waving at Saturn

A mosaic of more than 1,400 images of taken around the world of people waving back at NASA’s Cassini spacecraft the day it took a picture of Earth as part of a larger mosaic of the Saturn system. The images arrived at NASA via Twitter, Facebook, Flickr, Instagram, Google+ and e-mail. Click for large version. Credit: NASA/JPL-Caltech

Are you in this photo? People around the world shared more than 1,400 images
of themselves as part of NASA’s Wave at Saturn event on July 19. Cassini used its high-resolution camera that day to snap a portrait of the pale blue dot Earth alongside the planet Saturn. Meanwhile, back on the planet, we waved back.

A small cropped portion of the mosaic pictured above. Credit: NASA/JPL-Caltech

“While Earth is too small in the images Cassini obtained to distinguish any individual human beings, the mission has put together this collage so that we can celebrate all your waving hands, uplifted paws, smiling faces and artwork,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory.

Earth is the blue dot in this photo taken by the Cassini spacecraft at Saturn on July 19, 2013 from a distance of 898 million miles (1.44 billion km). The dark side of Saturn, its bright limb, the main rings, the F ring, and the G and E rings are clearly seen. Credit: NASA/JPL-Caltech/Space Science Institute

If the Earth stops spinning, we’d be in big trouble

The Earth spins once every 23 hours and 56 minutes in relation to the background stars. It takes 24 hours for the sun to return to the same spot in the sky.

Like you, I’m given to wondering about “what ifs” to better understand the assumptions we make about the world. One of my favorites is what if the Earth stopped rotating?

Let’s just say things would go sideways fast. Since the Earth spins us at 1,000 mph to the east, a sudden brake on its rotation would send everything not bolted to bedrock through the air in a terrifying tsunami of bricks, buildings, trees, people and cars. The deceleration alone would pulverize many common materials.

Picture a car traveling at 1,000 mph hitting a wall. That’s what we’re talking about here. Now imagine everything around you doing the same; the chaos and destruction would put the kibosh on civilization as we know it.

If the headlong flight of everything around you doesn’t do the trick, wind and water will take care of everything else. The atmosphere also shares in the Earth’s rotation, and since it’s not attached to anything, it’s free to move. Stop the Earth and suddenly you’ll have supersonic 1,000 mph winds clawing away at what little is left standing.

The same holds true for water. With 71% of Earth’s surface covered in water, 1,000 mph tsunamis would rise up over much of the planet’s landmass and scrub it to the nubs.

A small sampling of rotation speeds across the northern half of the globe. Illustration: Bob King

Depending where you live, the speed of your now flying car during this theoretical disaster would vary. Earth’s circumference is 25,000 miles at the equator and the planet rotates once in about 24 hours. If you could look down and see Earth spin, people at the equator would be scooting along at 1,041 mph (25,000 divided by 24). As you move north or south of the equator the distance around the Earth shrinks until you arrive at the poles where it’s zero. Since a smaller “circle of Earth” spins through the same 24 hours, folks north and south of the equator travel more slowly.

Here at 47 degrees north latitude in Duluth, Minn., my kitchen, computer and typing fingers are merry-go-rounding the planet at 708 mph. Things aren’t crashing into each other because everything around me partakes of the same speed so long as I don’t rush hot tea to my lips and cause a nasty spill. Essentially, the world appears at rest.

To find your own PBV (personal ballistic velocity) number during our hyper-emergency, multiply the speed at the equator by the cosine of your latitude. Don’t sweat cosines. Just go to Google and type in the word cosine followed by your latitude like this – cosine 47 degrees. Take that number and multiply it by 1,041 mph to find how fast you’re traveling. Here’s a table of sample latitudes:

* 0 degrees (equator) = 1,042 mph
* 20 degrees N or S = 978 mph
* 40 degrees N or S =  797 mph
* 60 degrees N or S = 520 mph
* 80 degrees N or S = 180 mph
* 90 degrees N or S (poles) = 0 mph

Only the poles stand out as potential places to avoid the worst of our sickening scenario. But not for long, as we’ll soon learn.

Assume for a moment you’ve just survived this worst catastrophe since that Mars-sized planet slammed the Earth 4.5 billion years ago liberating rocks that later coalesced into the moon. Once the smoke cleared and the wind died down, you’d notice a few oddities.

The sun stays up for about six months on a non-rotating Earth. Illustration: Bob King

Without rotation, one side of Earth would be in darkness, the other in sunlight. If you ended up on Earth’s sunny side at sunset, you’d be surprised to see the sun traveling backwards (from west to east) very slowly – about the width of your little finger a day. After approximately 182 days or half-a-year, it would finally set in the east followed by a couple weeks of twilight and then a night lasting nearly five months. If that sounds cold and dark it would be, since that’s pretty much what Antarctica experiences every year. After another couple weeks of twilight you’d be grateful to see the sun finally return again in the west.

Without rotation to provide the familiar 24-hour day-night cycle, we’d have to wait for Earth’s much more ponderous 365-day-long revolution around the sun to experience day and night. Our planet would now take a full year to do what it used to in a day. The pinkie-width daily movement of the sun is a reflection of Earth’s revolution.

At this point you might be wondering what else could go wrong if Earth stopped spinning. The Earth’s spin creates centrifugal force that causes its equator to bulge outward. Without rotation to maintain the bulge, Earth would become a near perfect sphere as equatorial waters flowed towards the poles. In their wake, we’d likely see a brand new equatorial supercontinent exposed.

The structure of the Earth including its interior solid core surrounded by the liquid outer core. The inner core is similar to the temperature of the surface of the sun: 10,800 F (6000 C). Credit: Wikipedia

Finally, let’s consider the Earth’s innards. The latest data show that our planet has a solid core of iron-nickel 1,500 miles (2,400 km) that spins in the same direction at nearly the same speed as our rotation.  Assuming the core would keep on turning once the brakes were put on Earth’s turning, it would continue to spin,  likely tearing the planet apart from the bottom up. You’d end up with a blazing ball of lava surrounded by rings made the former Europe, U.S. and all the rest.

OK, so let’s stop the core. Not a good idea. Spinning a big ball of iron-nickel helps to create a magnetic field around the planet that protects us from dangerous solar and cosmic radiation. Without it, we’d get fried from above. And worst of all, without a magnetic field, we’d have to kiss the aurora borealis goodbye … probably forever. That hurts, but by then Earth wouldn’t be any fun anymore anyway.

Nothing short of getting whacked by another planet, something that won’t happen anytime soon, would drastically change Earth’s spin. Meanwhile you and I will just keep going around in circles trying to make sense out of this crazy life.

Artist’s view of the early Earth still under bombardment by comets and meteorites some 4 billion years ago. The moon was closer to our planet then and rotated faster than it does today. So did the Earth. Credit: Dr. David Aguilar

Our pale blue planet started turning long ago when dust and gases orbiting the infant sun drew together under the force of gravity to form the seed that would later become Earth. As the material collapsed towards its center, it rotated faster and faster just as a skater does when she draws her arms in during a spin. It probably took around 100 million years (2% the age of the solar system) for the Earth to form through the gradual accumulation of smaller objects.

Earth began its existence with a much faster rotation than the current. Shortly after the moon formed some 4.5 billion years ago, a full day on the planet lasted just 5 hours – barely enough time to get out of bed, eat breakfast and go to work before the sun would set.  Because of gravitational friction via the tides raised by the moon’s gravitational pull, our spin has been slowing down ever since. In 140 million years, a day will be 25 hours long.