Scientists already know that magnetic north shifts. Once every few hundred thousand years the magnetic poles flip so that a compass would point south instead of north. While changes in magnetic field strength are part of this normal flipping cycle, data from Swarm have shown the field is starting to weaken faster than in the past. Previously, researchers estimated the field was weakening about 5 percent per century, but the new data revealed the field is actually weakening at 5 percent per decade, or 10 times faster than thought. As such, rather than the full flip occurring in about 2,000 years, as was predicted, the new data suggest it could happen sooner.
You can read up on geomagnetic reversals on Wikipedia. A short sampling:
These periods [of polarity] are called chrons. The time spans of chrons are randomly distributed with most being between 0.1 and 1 million years with an average of 450,000 years. Most reversals are estimated to take between 1,000 and 10,000 years. The latest one, the Brunhes-Matuyama reversal, occurred 780,000 years ago. A brief complete reversal, known as the Laschamp event, occurred only 41,000 years ago during the last glacial period. That reversal lasted only about 440 years with the actual change of polarity lasting around 250 years. During this change the strength of the magnetic field dropped to 5% of its present strength.
"I think this is a very important piece of science," said Douglas J. McCauley of the University of California, Santa Barbara. That's particularly high praise coming from Dr. McCauley, who has been a scathing critic of Dr. Costanza's attempt to put price tags on ecosystem services.
"This paper reads to me like an annual financial report for Planet Earth," Dr. McCauley said. "We learn whether the dollar value of Earth's major assets have gone up or down."
The group last calculated this value back in 1997 and it rose sharply over the past 17 years, even as those natural habitats are disappearing. This line from the article stunned me:
Dr. Costanza and his colleagues estimate that the world's reefs shrank from 240,000 square miles in 1997 to 108,000 in 2011.
Coral reefs shrank by more than half over the past 17 years...I had no idea the reef situation was that bad. Jesus.
If the Moon orbited the Earth at the same distance as the International Space Station, it might look a little something like this:
At that distance, the Moon would cover half the sky and take about five minutes to cross the sky. Of course, as Phil Plait notes, if the Moon were that close, tidal forces would result in complete chaos for everyone involved.
There would be global floods as a tidal wave kilometers high sweeps around the world every 90 minutes (due to the Moon's closer, faster orbit), scouring clean everything in its path. The Earth itself would also be stretched up and down, so there would be apocalyptic earthquakes, not to mention huge internal heating of the Earth and subsequent volcanism. I'd think that the oceans might even boil away due to the enormous heat released from the Earth's interior, so at least that spares you the flood... but replaces water with lava. Yay?
About 250 million years ago, Earth suffered its fifth (and worst) mass extinction event. Nearly seventy percent of land species disappeared. And they got off easy compared to marine species. Are we headed for another mass extinction on Earth? I'm not ready to break that news. But something unusual is definitely going on and extinction rates seem to be speeding up. Here's an interesting chat with Elizabeth Kolbert, author of The Sixth Extinction.
The worst mass extinction of all time came about 250 million years ago [the Permian-Triassic extinction event]. There's a pretty good consensus there that this was caused by a huge volcanic event that went on for a long time and released a lot of carbon-dioxide into the atmosphere. That is pretty ominous considering that we are releasing a lot of CO2 into the atmosphere and people increasingly are drawing parallels between the two events.
"Theoretically, this place ought to be perfect," leading Terxus astrobiologist Dr. Srin Xanarth said of the reportedly blighted planet located at the edge of a spiral arm in the Milky Way galaxy. "When our long-range satellites first picked it up, we honestly thought we'd hit the jackpot. We just assumed it would be a lush, green world filled with abundant natural resources. But unfortunately, its damaged biosphere makes it wholly unsuitable for living creatures of any kind."
"It's basically a dead planet," she added. "We give it another 200 years, tops."
The alien researchers stated that the dramatically warming atmosphere of RP-26 contains alarming amounts of carbon dioxide and methane, as well as an ozone layer that-for reasons they cannot begin to fathom-has been allowed to develop a gaping hole. They also noted the presence of melting polar icecaps, floods, and enough pollutants to poison "every last drop of the planet's fresh water, if you can even call it that."
You finally really did it. You maniacs! You blew it up! God damn you! God damn you all to hell!
A pair of scientists looked at the rate at which the complexity of life increases and then extrapolated back to a point of zero complexity, aka the origin of life. The answer they came up with is 9.7 ± 2.5 billion years ago. Which is much older than the Earth. This idea has some provocative implications:
Sharov and Gordon say their interpretation also explains the Fermi paradox, which raises the question that if the universe is filled with intelligent life, why can't we see evidence of it.
However, if life takes 10 billion years to evolve to the level of complexity associated with humans, then we may be among the first, if not the first, intelligent civilisation in our galaxy. And this is the reason why when we gaze into space, we do not yet see signs of other intelligent species.
The storm had an unusually low central pressure area. Paul A. Newman, chief scientist for Atmospheric Sciences at NASA's Goddard Space Flight Center in Greenbelt, Md., estimates that there have only been about eight storms of similar strength during the month of August in the last 34 years of satellite records. "It's an uncommon event, especially because it's occurring in the summer. Polar lows are more usual in the winter," Newman said.
Arctic storms such as this one can have a large impact on the sea ice, causing it to melt rapidly through many mechanisms, such as tearing off large swaths of ice and pushing them to warmer sites, churning the ice and making it slushier, or lifting warmer waters from the depths of the Arctic Ocean.
My projections about increasing global temperature have been proved true. But I failed to fully explore how quickly that average rise would drive an increase in extreme weather.
In a new analysis of the past six decades of global temperatures, which will be published Monday, my colleagues and I have revealed a stunning increase in the frequency of extremely hot summers, with deeply troubling ramifications for not only our future but also for our present.
This is not a climate model or a prediction but actual observations of weather events and temperatures that have happened. Our analysis shows that it is no longer enough to say that global warming will increase the likelihood of extreme weather and to repeat the caveat that no individual weather event can be directly linked to climate change. To the contrary, our analysis shows that, for the extreme hot weather of the recent past, there is virtually no explanation other than climate change.
In many ways, the phrase "global warming" is grossly misleading. "Oh," we think, "it's gonna be a couple degrees warmer in NYC in 20 years than it is now." But the Earth's climate is a chaotic non-linear system, which means that a sudden shift of a degree or two -- and when you're talking about something as big as the Earth, a degree over several decades is sudden -- pushes things out of balance here and there in unpredictable ways. So it's not just that it's getting hotter, it's that you've got droughts in places where you didn't have them before, severe floods in other places, unusually hot summers, and even places that are cooler than normal, all of which disrupts the animal and plant life that won't be able to acclimate to the new reality fast enough.
Space always seems so far away and much of it actually is. But space is actually quite close to where we are all sitting right now. The Kármán line, the commonly accepted boundary between the Earth's atmosphere and space, is only 62 miles above sea level.
The line was named after Theodore von Kármán, (1881-1963) a Hungarian-American engineer and physicist who was active primarily in the fields of aeronautics and astronautics. He first calculated that around this altitude the Earth's atmosphere becomes too thin for aeronautical purposes (because any vehicle at this altitude would have to travel faster than orbital velocity in order to derive sufficient aerodynamic lift from the atmosphere to support itself). Also, there is an abrupt increase in atmospheric temperature and interaction with solar radiation.
A distance of 62 miles can covered by a car on the interstate in less than an hour. Stable Earth orbits are achievable at only 100 miles above the Earth, with the ISS and Space Shuttles usually orbiting at a height of ~200 miles. To show how small a distance that really is, I made the following image...the orange line in the upper left represents 200 miles away from the surface.
This is a wonderful seven-minute HD video tour of Earth using video shot from orbit.
Look at this neat picture of Great Salt Lake in Utah. And the variation in color? That's due to an almost a complete blockage of the circulation of the lake by a trestle for a railroad that crosses from one side to the other. It stops the circulation and things get a little bit saltier and certainly saltier at the north end of the lake.
In 2004, the astrophysicist Robin Canup, at the Southwest Research Institute in Texas, published some remarkable computer simulations of the Big Splat. To get a moon like ours to form -- instead of one too rich in iron, or too small, or wrong in other respects -- she had to choose the right initial conditions. She found it best to assume Theia is slightly more massive than Mars: between 10% and 15% of the Earth's mass. It should also start out moving slowly towards the Earth, and strike the Earth at a glancing angle.
The result is a very bad day. Theia hits the Earth and shears off a large chunk, forming a trail of shattered, molten or vaporized rock that arcs off into space. Within an hour, half the Earth's surface is red-hot, and the trail of debris stretches almost 4 Earth radii into space. After 3 to 5 hours, the iron core of Theia and most of the the debris comes crashing back down. The Earth's entire crust and outer mantle melts. At this point, a quarter of Theia has actually vaporized!
After a day, the material that has not fallen back down has formed a ring of debris orbiting the Earth. But such a ring would not be stable: within a century, it would collect to form the Moon we know and love. Meanwhile, Theia's iron core would sink down to the center of the Earth.
Back in July, Ben Terrett wrote a post about how many instances of the word "helvetica" set in unkerned 100 pt Helvetica it would take to go from the Earth to the Moon:
The distance to the moon is 385,000,000,000 mm. The size of an unkerned piece of normal cut Helvetica at 100pt is 136.23 mm. Therefore it would take 2,826,206,643.42 helveticas to get to the moon.
But let's say you wanted to stretch one "helvetica" over the same distance...at what point size would you need to set it? The answer is 282.6 billion points. At that size, the "h" would be 44,600 miles tall, roughly 5.6 times as tall as the Earth. Here's what that would look like:
The Earth is on the left and that little speck on the right side is the Moon. Here's a close-up of the Earth and the "h":
And if you wanted to put it yet another way, the Earth is set in 50.2 billion point type -- Helvetically speaking -- while the Moon is set in 13.7 billion point type. (thx, @brainpicker)
This video of what Earth would look like with Saturnine rings is pretty ho-hum, yeah, there's a shot from orbit of the Earth with Saturn's rings around it, and then BAM! here's what it would look like at night in NYC:
With the combination of GPS and orientation data that's baked in to so many digital photographs, it should be possible to create a filter -- I hear the kids call them apps now -- that automatically inserts properly positioned Saturn rings into any sky you want.
With these four recent advances -- Dr. Szostak's protocells, self-replicating RNA, the natural synthesis of nucleotides, and an explanation for handedness -- those who study the origin of life have much to be pleased about, despite the distance yet to go. "At some point some of these threads will start joining together," Dr. Sutherland said. "I think all of us are far more optimistic now than we were five or 10 years ago."
The whole-earth nature documentary space is quickly becoming crowded. We've got:
The Blue Planet, 2001
Deep Blue, 2003
Planet Earth, 2006
Nature's Great Events, 2009
The last one on the list is from Disney. If you watch the trailer, the company is attempting to say, "Planet Earth? Ha! Disney was down with nature all along!" Pfft. A point in Disney's favor however is that Oceans is being done by Jacques Perrin, the man responsible for Microcosmos and Winged Migration. Points against: the film has cost $75 million so far (for a documentary!), the footage in the trailer looks like it was lifted directly from The Blue Planet and Planet Earth, and no David Attenborough narration.
Update: I added Earth to the list, also from Disney. Here's the trailer. BBC and Discovery are listed as partners so it's likely that the footage in the film is from Planet Earth. (thx, @gjdsalinger)
If you liked Planet Earth, you should probably check out Nature's Great Events. Narrated by David Attenborough and currently airing in the UK on BBC1 and BBC HD, the series consists of six 50-minute shows, each of which features a large-scale annual event, like the spring thaw in the Arctic Circle and the sardine run along the coast of South Africa. The series was shot in HD using many of the techniques seen in Planet Earth.
If you're in the UK, you can check out the first three episodes on the BBC site. In the US, Discovery will be airing the show sometime in the spring under the title Seasons of Survival (apparently Nature's Great Events isn't dramatic enough for the American audience). No word on whether Attenborough's expert narration will also be replaced as it was in Planet Earth.
But what if you did dig a hole through the Earth and jump in? What would happen?
Well, you'd die (see below). But if you had some magic material coating the walls of your 13,000 km deep well, you'd have quite a trip. You'd accelerate all the way down to the center, taking about 20 minutes to get there. Then, when you passed the center, you'd start falling up for another 20 minutes, slowing the whole way. You'd just reach the surface, then you'd fall again. Assuming you evacuated the air and compensated for Coriolis forces, you'd repeat the trip over and over again, much to your enjoyment and/or terror. Actually, this would go on forever, with you bouncing up and down. I hope you remember to pack a lunch.
Note that as you fell, you accelerate all the way down, but the acceleration itself would decrease as you fell: there is less mass between you and the center of the Earth as you head down, so the acceleration due to gravity decreases as you approach the center. However, the speed with which you pass the center is considerable: about 7.7 km/sec (5 miles/second).
Fast forward to the year 2483 and we'll probably all be using such holes to quickly travel through the earth. Spain to New Zealand in 42 minutes! New York to the middle of the Indian Ocean? 42 minutes! I also recall reading somewhere that the tunnels don't need to run through the middle of the earth. You don't get the free fall effect, but with the proper contraption (mag-lev tunnel train?) you'll be pulled through the tunnel at a great speed. Does this ring anyone's bell?
Update: A bell has rung. The tunnels described above are called chord tunnels and the travel time through the earth in a frictionless chord tunnel is always 42 minutes, even if the tunnel is only a few hundred miles long or so (say from New York to Detroit). (thx, mike)
Update: In this short Nova clip, Neil deGrasse Tyson "demonstrates" a trip through the center of the earth. (thx, michael)
Flat-earthers are people who believe, here in the 21st century, that the earth is flat. (Believers in a round earth are called globularists.)
And what about the fact that no one has ever fallen off the edge of our supposedly disc-shaped world? Mr McIntyre laughs. "This is perhaps one of the most commonly asked questions," he says. "A cursory examination of a flat earth map fairly well explains the reason - the North Pole is central, and Antarctica comprises the entire circumference of the Earth. Circumnavigation is a case of travelling in a very broad circle across the surface of the Earth."
If, like me, you have questions about how the earth could possibly be flat, some of them are answered in the Flat Earth FAQ.
Q: "What about the stars, sun and moon and other planets? Are they flat too? What are they made of?"
A: The sun and moon, each 32 miles in diameter, circle Earth at a height of 3000 miles at its equator, located midway between the North Pole and the ice wall. Each functions similar to a "spotlight," with the sun radiating "hot light," the moon "cold light." As they are spotlights, they only give light out over a certain are which explains why some parts of the Earth are dark when others are light. Their apparent rising and setting are caused by optical illusions. In the "accelerating upwards" model, the stars, sun and moon are also accelerating upwards. The stars are about as far as San Francisco is from Boston. (3100 miles)
BTW, the "ice wall" is what separates the edge of the earth's disc with outer space or whatever ether or monsters are beyond the earth. We know the wall as Antarctica. I call shenanigans on all this...it's gotta be a hoax. Nobody's this ignorant, right? Please?
The images you see below were taken at the turn of the Millennium, when NASA's scientists had a brilliant idea: to scan through 400,000 images taken by the Landsat 7 satellite and display only the most the most beautiful. A handful of the best were painstakingly chosen and then displayed at the Library of Congress in 2000.
You must see these. Bonus: all the images are available in wallpaper size for your computer desktop.
This site lets you track the International Space Station, the Space Shuttle (when in orbit), and all sorts of other satellites in relation to their position over the earth with a familiar Google Maps interface. Very cool.
The Moon has been a stabilizing factor for the axis of rotation of the Earth. If you look at Mars, for instance, that planet has wobbled quite dramatically on its axis over time due to the gravitational influence of all the other planets in the solar system. Because of this obliquity change, the ice that is now at the poles on Mars would sometimes drift to the equator. But the Earth's moon has helped stabilize our planet so that its axis of rotation stays in the same direction. For this reason, we had much less climatic change than if the Earth had been alone. And this has changed the way life evolved on Earth, allowing for the emergence of more complex multi-cellular organisms compared to a planet where drastic climatic change would allow only small, robust organisms to survive.
In Galileo's time, nighttime skies all over the world would have merited the darkest Bortle ranking, Class 1. Today, the sky above New York City is Class 9, at the other extreme of the scale, and American suburban skies are typically Class 5, 6, or 7. The very darkest places in the continental United States today are almost never darker than Class 2, and are increasingly threatened. For someone standing on the North Rim of the Grand Canyon on a moonless night, the brightest feature of the sky is not the Milky Way but the glow of Las Vegas, a hundred and seventy-five miles away. To see skies truly comparable to those which Galileo knew, you would have to travel to such places as the Australian outback and the mountains of Peru.
If a virulent virus -- or even the Rapture -- depopulated Earth overnight, how long before all trace of humankind vanished? [...] Days after our disappearance, pumps keeping Manhattan's subways dry would fail, tunnels would flood, soil under streets would sluice away and the foundations of towering skyscrapers built to last for centuries would start to crumble.
Bob Holmes imagines an earth without people in New Scientist. "All things considered, it will only take a few tens of thousands of years at most before almost every trace of our present dominance has vanished completely. Alien visitors coming to Earth 100,000 years hence will find no obvious signs that an advanced civilisation ever lived here."