Halley's Comet: Facts About the Most Famous Comet που ισως να σηματοδοτησε και την γεννηση του Χριστου!

Halley's Comet: Facts About the Most Famous Comet

By Elizabeth Howell, Space.com Contributor 

An image of Halley's Comet taken in 1986.

Credit: NASA

Halley's Comet is arguably the most famous comet. It is a "periodic" comet and returns to Earth's vicinity about every 75 years, making it possible for a human to see it twice in his or her lifetime. The last time it was here was in 1986, and it is projected to return in 2061.

The comet is named after English astronomer Edmond Halley, who examined reports of a comet approaching Earth in 1531, 1607 and 1682. He concluded that these three comets were actually the same comet returning over and over again, and predicted the comet would come again in 1758.

Halley didn't live to see the comet's return, but his discovery led to the comet being named after him. (The traditional pronunciation of the name usuallyrhymes with valley.) Halley's calculations showed that at least some comets orbit the sun.

Further, the first Halley's Comet of the space age – in 1986 – saw several spacecraft approach its vicinity to sample its composition. High-powered telescopes also observed the comet as it swung by Earth.

Halley's in history

The first known observation of Halley's took place in 239 B.C., according to the European Space Agency. Chinese astronomers recorded its passage in the Shih Chi and Wen Hsien Thung Khao chronicles.

When Halley's returned in 164 B.C. and 87 B.C., it probably was noted in Babylonian records now housed at the British Museum in London. "These texts have important bearing on the orbital motion of the comet in the ancient past," noted a Nature research paper about the tablets.

This portion of the Bayeux Tapestry shows Halley's Comet during its appearance in 1066.

Credit: Public domain

Halley's most famous appearance occurred shortly before the 1066 invasion of England by William the Conquerer. It is said that William felt the comet heralded his success. In any case, the comet was put on the Bayeux Tapestry – which chronicles the invasion – in William's honor.

Another appearance of the comet in 1301 possibly inspired Italian painter Giotto's rendering of the Star of Bethlehem in "The Adoration of the Magi," according to the Britannica encyclopedia.

Astronomers in these times, however, saw each appearance of Halley's Comet as an isolated event. Comets were often foreseen as a sign of great disaster or change.

Even when Shakespeare wrote his play "Julius Caesar" around 1600, just 105 years before Edmond Halley calculated that the comet returns over and over again, one famous phrase spoke of comets as heralds: "When beggars die there are no comets seen; The heavens themselves blaze forth the death of princes."

Discovery of Halley's recurrence

Astronomy began changing swiftly around the time of Shakespeare, however. Many astronomers of his time held that Earth was the center of the solar system, but Nicolaus Copernicus – who died about 20 years before Shakespeare's birth – published findings showing that the center was actually the sun.

It took several generations for Copernicus' calculations to take hold in the astronomy community, but when they did, they provided a powerful model for how objects move around the solar system and the universe.

Edmond Halley

Edmond Halley published "A Synopsis of the Astronomy of Comets" in 1705, cataloguing what he had found from searching historical records of 24 comets appearing near Earth between 1337 to 1698. Three of those observations appeared to be very similar in terms of orbit and other parameters, leading Halley to propose that one comet might be visiting Earth again and again.

The comet appeared in 1531, 1607 and 1682. Halley suggested the same comet could return to Earth in 1758. Halley did not live long enough to see its return – he died in 1742 – but his discovery inspired others to name the comet after him.

On each successive journey to the inner solar system, astronomers on Earth turned their telescopes skyward to watch Halley's approach.

The comet's pass in 1910 was particularly spectacular, as the comet flew by about 13.9 million miles (22.4 million kilometers) from Earth, which is about 1/15 the distance between Earth and the Sun. On that occasion, Halley's wascaptured on camera for the first time.

According to biographer Albert Bigelow Paine, the writer Mark Twain said in 1909, "I came in with Halley's Comet in 1835. It is coming again next year, and I expect to go out with it." Twain died on April 21, 1910, one day after perihelion, when the comet emerged from the far side of the sun.

This photo of Halley's comet was taken by the Russian Vega 2 spacecraft, one of two Soviet probes (Vega 1 was the other) to rendezvous with the comet during its 1986 trip through the solar system in March 1986. The closest approach of Vega 1 to Halley was 8890 km while Vega 2 had a close encounter at 8030 km.

Credit: ESA

Halley's in the Space Age

When Halley's Comet came by Earth in 1986, it was the first time we could send spacecraft up to look at it.

That was a fortunate occurrence, as the comet ended up being underwhelming in observations from Earth. When the comet made its closest approach to the sun, it was on the opposite side of that star from the Earth – making it a faint and distant object, some 39 million miles away from Earth.

Several spacecraft successfully made the journey to the comet. This fleet of spaceships is sometimes dubbed the "Halley Armada." Two joint Soviet/French probes (Vega 1 and 2) flew nearby, with one of them capturing pictures of the heart or nucleus of the comet for the first time.

The European Space Agency's Giotto got even closer to the nucleus, beaming back spectacular images to Earth. Japan sent two probes of its own (Sakigake and Suisei) that also obtained information on Halley.

Additionally, NASA's International Cometary Explorer (already in orbit since 1978) captured pictures of Halley from 17.3 million miles (28 million kilometers away.)

"It was inevitable that this most famous of all comets would receive unprecedented attention, but the actual magnitude of the effort has surprised even most of those involved in it," NASA noted in an account of the event.

Sadly, the astronauts aboard Challenger's STS-51L mission were also scheduled to look at the telescope when they arrived in the orbit, but they never got the chance. The shuttle exploded about two minutes after launch on Jan. 28, 1986, due to a rocket malfunction.

It will be many decades until Halley's gets close to Earth again, but in the meantime you can see its remnants every year. The Orionid meteor shower, which is spawned by Halley's fragments, occurs annually in October. Halley's also produced a shower in May, called the Eta Aquarids.

When Halley's sweeps by Earth in 2061, the comet will be on the same side of the sun as Earth and will be much brighter than in 1986.

One astronomer predicted it could be as bright as apparent magnitude -0.3. This is relatively bright, but well below that of the brightest star in Earth's sky: Sirius, at magnitude -1.4 as seen from Earth.

— Elizabeth Howell, SPACE.com Contributor

ΔΕΙΤΕ ΠΩΣ ΚΑΤΑΣΚΕΥΑΖΕΤΑΙ ΕΝΑ AUDI TT RS 400 HORSES 3.7 seconds.(video)

2017 Audi TT RS arrives with 400 horsepower

If the Audi TT was ever considered to be more style than substance, that stereotype can be put to rest with the arrival of the new TT RS. Revealed in both coupe and convertible bodystyles at the Beijing Motor Show today, Ingolstadt's latest performance models boast 400 horsepower. And for nostalgic VW and Audi fans, this is still the only way to buy a five-cylinder engine.

For those keeping track, that represents an increase of 60 hp over the previous version, accompanied by 354 pound-feet of torque. Channeled to all four wheels in typical Quattro style, those 400 horses will propel the TT RS to 62 miles per hour from a standstill in as little as 3.7 seconds.

That's enough to undercut the new Porsche 718 Cayman S by a good few tenths, and will leave the vast majority of drivers on the road or track looking at its pair of oval tailpipes, OLED taillights, and fixed rear wing rather than the new front end with its oversized air intakes. Those lucky enough to find themselves inside the new TT RS will find a pair of low-slung bucket seats along with standard TT fare like a 12.3-inch Virtual Cockpit display, Audi Connect infotainment system, and inductive smartphone charging.

US pricing and availability are still being worked out, but Audi of America spokesman Mark Dahncke tells Autoblog that the new TT RS will arrive in showrooms Stateside "sometime next year." Overseas the new model is set to launch in the fall. The starting price of €66,400 euros listed for Europe works out to nearly $75k at current exchange rates. More tellingly the TT RS price is just above the €64,118 that Porsche charges for the new 718 Cayman S. This is clearly one bout of sibling rivalry that's just heating up.
Read More http://www.autoblog.com/2016/04/25/20...

Typhoon Meranti: Taiwan and China brace for biggest storm of 2016

Shutdowns and evacuations ordered, electricity cut and trail of damage reported from ‘world’s strongest typhoon this year’
Satellite image of the Philippine island of Itbayat in the eye of typhoon Meranti. Photograph: CIMSS


Nicola Smith in Taipei and agencies

Wednesday 14 September 2016 07.50 BSTLast modified on Wednesday 14 September 201611.21 BST







Tens of thousands of homes lost power across Taiwan as the island was hit by super-typhoon Meranti – a storm rated the strongest in the world so far this year – forcing schools and businesses to close and leading to flight cancellations.

Taiwan’s Central Weather Bureau warned that the category 5 storm would threaten southern and eastern cities, including Kaohsiung and Hualien, with strong winds, torrential rain and flooding.

Meranti, which grew in strength as it neared Taiwan, was carrying maximum winds of 134mph (216km/h), meteorologists said. Fallen power cables and trees were among some of the early damage reported on Wednesday.

“This typhoon is the world’s strongest so far this year,” said weather bureau spokeswoman Hsieh Pei-yun. “Its impact on Taiwan will peak all day today.”
FacebookTwitterPinterest Composite image of Category 5 super-typhoon Meranti. Photograph: 2016 Eumetsat

Companies and schools in Kaohsiung and other cities were closed and almost 1,500 residents were evacuated, the Central Emergency Operation Centre said.

Nearly 200,000 households were without electricity, according to Taiwan Power. Most domestic flights were cancelled, including all of those from Kaohsiung airport, where international flights were also severely affected.

Taiwan was expected to feel the full force of the typhoon on Wednesday and into Thursday before the storm reached China, meteorologists said.

Meranti was expected to make landfall in the southern Chinese provinces of Guangdong and Fujian on Thursday, where authorities were already cancelling train services and preparing to evacuate people, state media said.



In eastern Guangdong province, authorities ordered trawlers to return to harbour and fishermen to shelter on land from Meranti, which the official China News Service said could be the strongest typhoon to hit that part of China since 1969.

Typhoons are generated at this time of year, picking up strength as they cross the warm waters of the Pacific before bringing strong winds and violent rainstorms when they hit land.

Meranti comes just over two months after the deadly typhoon Nepartak cut power, grounded flights and forced thousands to flee their homes across central and southern areas of Taiwan.

In 2009, typhoon Morakot cut a swath of destruction through southern Taiwan, killing about 700 people and causing up to £2.3bn ($3bn) of damage.

Earlier, Meranti crossed the Philippines where there were fears for the safety of 3,000 inhabitants of the tiny island of Itbayat after satellite images showed it directly in the eye of the megastorm.




A weatherman at the Pagasa meteorological station in Manila, who gave his name as Rene, said that communications had not been established with Itbayat and that the local government was desperately trying to reach inhabitants.

“Maybe we can fix communications by tomorrow,” he said, as strong gusts of wind were still being recorded in the area and night was falling. Residents, already familiar with strong typhoons, would hopefully have been protected by the traditional stone houses with strong, thick walls, Rene added. “We pray there will be no casualties,” he said.

The weatherman added that it was unusual for the eye of a storm to be bigger than the size of an entire island.

Mercedes-Benz has a Vision of autonomous, drone-launching delivery vans

Today in Stuttgart, Mercedes-Benz pulled the wraps off a concept that it hopes will allow the commercial vans division of the company to branch out into logistics and delivery. Think of it as the kitchen sink approach: not only does the van have every of-the-moment gizmo imaginable, it also represents an entirely Mercedes supply chain from warehousing to final delivery.

Oh, and it has a couple of delivery drones on the roof. That's so very 2016.

Mercedes calls it the Vision Van, which sounds a lot like something you'd see parked at an Arby's with a mural of a wizard riding a dragon on it. There aren't any murals on the big, blank, plain slab sides. Think of it as more of a collection of preexisting ideas brought together in an integrated system, or a particularly new vehicle idea, and you're on the right track. It's bringing all this stuff together that's the interesting part. After all, you've seen concept vehicles with joystick controls and plenty of fully electric city vehicles already.

The basic premise is that Mercedes will sell, lease, or even rent on demand the capacity in both the storage and delivery system, but also vans much like this concept themselves. The company doesn't feel strongly about the ownership model in this instance, because it can make a lot of money convincing buyers to adopt its system wholesale. In return, Mercedes is offering both a turn-key solution and multiple gains in efficiency over a partially-networked logistical system.

The Vision Van concept itself is a battery-electric vehicle intended for dense urban delivery, with about 100 horsepower and a range of just under 170 miles. Ignore the drones; the really neat stuff is in back. There's a "one-shot" loading system, essentially fitted smart racks that slide into the cargo area robotically. At the delivery location, the rack with the package maneuvers itself automatically to a pass-through just behind the driver, preventing time lost both loading the van efficiently and repacking the cargo area to get the packages ready for the next delivery. When it's done, the robot slides out the rack and slides in the next one. The robot loader isn't quick, but this is all a concept anyhow.

The precariously-perched rooftop drones look neat, and they also are loaded automatically through a port in the roof. It's an interesting idea to have delivery trucksserve as mobile drone carriers and probably the most gee-whiz feature here.

As long as this hypothetical supply chain eliminates humans at the distribution center and in the air, why have a human in the Vision Van at all? That seems to be the next logical step for the fully-autonomous logistical network of the immediate future. We'll look back on the Vision Van in 20 years and laugh that it had a seat for the delivery person at all. Until then, don't expect to see this particular van launching drones around your neighborhood soon – it's just a concept, but not a far-fetched one.

2017 Peugeot 3008 - interior Exterior and Drive

Δημοσιεύτηκε στις 5 Ιουν 2016

2017 Peugeot 3008 SUV: price, specs and release date - See more at:

The new Peugeot 3008 SUV has been revealed in Paris. The car previews a new design direction for the company along with giving it an up-to-date rival to the likes of the Nissan Qashqai, Renault Kadjar and Kia Sportage.

It’s the first to get the latest version of the company’s i-cockpit – known for its small steering wheel and digital dials that sit above it. The design seems to have been improved in the new model so that your view of the car’s systems will never be obstructed as they have in past models.

All 3008s come with a huge infotainment screen complete with super-crisp graphics – it’ll be compatible with Apple Carplay, Mirror Link and Android Auto, allowing easy integration with smartphone apps sat-nav, music streaming and various other functions.

Quality has been massively improved. Most of the interior has soft-to-the-touch expensive plastics, fabric trims pieces and satisfyingly cold-to-the-touch metal switchgear – it’s certainly more interesting to look at than the inners of its aforementioned rivals. Even the interior warning sounds are, we’re told, designed to be easy on the ear, and the options list includes a stereo made by French hi-fi company Focal. The 3008 can even be scented with a choice of three “exquisite” perfumes.

The new 3008 is 8cm longer than the old model and can easily accommodate four six-footers, with front-seat passengers getting the option to spec full-body massage seats. The boot apparently has the lowest load lip in the segment and also opens electrically, so the new 3008 should score well in our practicality test. From launch Peugeot will offer the car with a folding electric scooter that lives in a load-bay-charging dock and offers a 10km range.

We’re more interested in how the car drives, though, and have to say the initial signs are positive. Based on the same MP2 platform that underpins the 308 (and of course the GTi), it’s 100kgs lighter than the old model and Peugeot’s making bold claims that it’ll be the best car to drive in its class.

It’ll come with the company’s proven PureTech petrol and Blue HDi diesel engines – with the potential for around 80mpg fuel economy when combined with the company’s AT6 automatic gearbox.

Bookmark this page for all the latest info on what should be a huge model for the French firm, and stay tuned to carwow for a full review in the coming months.

Updated 20 April ’16

The 2017 replacement for the Peugeot 3008 will feature an updated version of the firm’s i-Cockpit concept (pictured above) that’ll improve both driver comfort and safety. Read on for full details and pictures of the new cabin – expected to be fitted to numerous Peugeot models in the near future.

Simply speaking, i-Cockpit is Peugeot’s term for its latest cabin design – characterised by an unusually small steering wheel and dials mounted above rather than behind it. The first-generation i-Cockpit has already seen service with 208, 2008 and 308 models but, the 3008 is expected to be the first car to feature the revised system.

If you can’t wait for the new model, Peugeot will be offering progressively better discounts on the outgoing version. Put the current Peugeot 3008 in our car configurator to see the deals carwow could help you get.

The new system features a head-up display working in tandem with a 12.3-inch digital screen on top of the dash in place of conventional dials, similar to Audi’s excellent Virtual Cockpit system. The steering wheel will be mounted below rather than in front of the display to ensure the driver’s view of the screen is unobstructed. Peugeot claims this will make its cars safer by removing the need to look away from the road to regularly check sat-nav directions or your speed.

Peugeot has reduced the size of the steering wheel further from its already diminutive proportions to offer drivers increased knee and leg room and aid forward visibility. The smaller wheel is also claimed to improve handling by requiring less arm movement to achieve a given amount of turning. Additional changes include a new eight-inch touchscreen display on the centre console that controls the infotainment system.

Peugeot’s i-Cockpit previews new atmospheric lighting with customisable settings, massaging front seats and a built in fragrance diffuser – all features that could be fitted to high-spec 3008 models.

Read More https://www.carwow.co.uk/news/peugeot...

Moon's Birth May Have Vaporized Most of Earth, Study Shows

This artist's conception shows the giant impact that created Earth's moon. New research suggests the impact was powerful enough to vaporize a large portion of the young Earth.

Credit: Dana Berry/SwRI

The massive collision that created the moon may have vaporized most of the early Earth, according to a new analysis of samples collected during the Apollo moon missions.

In the early days of planet formation, a grazing collision between the newborn Earth and a Mars-size rock named Theia (named after the mother of the moon in Greek myth) may have led to the birth of the moon, according to a prevailing hypothesis. Debris from the impact later coalesced into the moon. 

This "giant-impact hypothesis" seemed to explain many details about Earth and the moon, such as the large size of the moon compared with Earth and the rotation rates of the two bodies. But in the last 15 years, evidence has arisen that has challenged scientists to alter the details of this hypothesis. [How the Moon Evolved: A Timeline in Images]

Forming the moon

The moon is Earth's nearest neighbor, but its origins date back to a violent birth billions of years ago. See how the moon was made in this Space.com infographic.

Credit: By Karl Tate, Infographics Artist

In 2001, scientists began discovering that terrestrial and lunar rocks had a lot in common: the two bodies possess many of the same chemical isotopes. (Isotopes of an element have different numbers of neutrons from each other. These subvarieties are identified by different numbers; for example, potassium-39 or potassium-40). Isotopes can act as geologic fingerprints, because prior work has suggested that planetary bodies that formed in different parts of the solar system generally have different isotopic compositions. 

These discoveries threw the giant-impact hypothesis into crisis because previous computer simulations of the collision predicted that 60 to 80 percent of the material that coalesced into the moon came from Theia rather than Earth. The likelihood that Theia happened to have virtually the same isotopic composition as Earth seemed extremely unlikely.

At first, scientists thought more precise isotopic analyses might help resolve this "isotopic crisis." However, more accurate measurements of oxygen isotopes reported in 2016 only helped confirm this problem, said study lead author Kun Wang, a geochemist now at Washington University in St. Louis.

"Now we need to rethink the ideas that we had about the giant impact," Wang told Space.com. 

New ideas

New models of the giant impact seek to explain how the moon could have formed from mostly the same material that makes up the Earth, rather than mostly from Theia. 

A diagram showing two recent models for how the moon formed from a collision between the early Earth and another massive body. One model (top) allows for an exchange of material between the Earth and the moon through a silicate atmosphere, while the other model creates a more thoroughly mixed sphere of a supercritical fluid (bottom). Each of these models leads to a different prediction for potassium isotope ratios in lunar and terrestrial rocks (right).

Credit: Kun Wang

"There are many new models — everyone is trying to come up with one — but two have been very influential," Wang said in a statement. [How the Moon Formed: 5 Wild Lunar Theories]

The original giant-impact model suggested that a relatively low-energy collision melted part of Earth and the whole of Theia, flinging some of the molten debris outward. One relatively new model, proposed in 2007, starts with a low-energy impact just like the original model, but adds an atmosphere of silicate vapor around Earth and the disk of debris that ends up forming the moon. This model suggests that this vapor shroud helps Earth and the disk exchange material before the moon emerges from the debris.

One drawback of this low-energy impact model is that it would take a long time to exchange material through an atmosphere, Wang said. This scenario would make it difficult to achieve the mix of material seen in terrestrial and lunar rocks, he said.

Another model, proposed in 2015, suggests that a high-energy impact created the moon, one so violent that it vaporized Theia as well as most of Earth, including the young planet's mantle region (the layer just above the core). This dense vapor then formed an atmosphere that filled a space more than 500 times bigger than today's Earth. Much of this material would fall back onto the Earth as it cooled, but in addition, some of the debris formed the moon. 

In this high-energy model, the atmosphere would behave like a "supercritical fluid," without a distinct separation between liquids and gases. Material could mix thoroughly in such an atmosphere, which could help explain the identical isotopic compositions of Earth and the moon, Wang said.

To see which model might best explain how the moon formed, Wang and his colleague Stein Jacobsen at Harvard University focused on potassium isotope data from terrestrial rocks and lunar samples gathered during the Apollo missions. Potassium is volatile, or easy to evaporate, and previous research suggested that analyzing potassium isotopes could shed light on the conditions during the event that formed the moon. 

The scientists analyzed seven moon rocks collected during the Apollo 11, 12, 14 and 16 missions. They compared their potassium isotope ratios with those of eight rocks representative of Earth's mantle.

The researchers developed a method to analyze potassium isotopes with a level of precision 10 times better than the best previous technique. Potassium has three stable isotopes, but only two of them, potassium-39 and potassium-41, are abundant enough to be measured with sufficient precision for this research.

The scientists discovered that lunar rocks were richer by about 0.4 parts per thousand compared with Earth rocks when it came to potassium-41, the heavier stable isotope of potassium. 

These findings support the high-energy impact model, which predicted that lunar rocks would possess more of the heavier isotope than terrestrial rocks. In contrast, the low-energy impact model suggested that lunar rocks would contain less of the heavier isotope.

The best explanation for how the heavier isotope came to dominate was that the moon condensed in a cloud with a pressure of more than 10 bar, or about 10 times the atmospheric pressure on Earth at sea level.

"I'm kind of surprised that the new model fits the data the best," Wang said. Still, "we had no expectation which model we were going to support," he said.

Future research should conduct follow-up studies to test these new findings. "We're definitely hoping more people will follow up and try to confirm our results," Wang said.

Wang and Jacobsen detailed their findings online Sept. 12 in the journal Nature.

ΕΝΤΥΠΩΣΙΑΚΗ ΑΣΚΗΣΗ ΤΗΣ ΡΩΣΙΑΣ ΣΤΗΝ ΚΡΙΜΑΙΑ(VIDEO)

On Monday, Russian military forces began a massive six-day war games exercise codenamed Caucasus 2016 including servicemen from the country’s naval, airborne and aerospace units conducted in the South of Russia in and around Crimea.

The military exercise served the purpose of "planning, preparation and conducting combat operations," but many defense analysts interpreted the show of military force to be a direct message to Ukraine and its Western allies regarding Russia’s control over the Crimean peninsula. The exercise was conducted at the Opuk training range on the Black Sea Coast with drills involving warships, aircraft and tanks, with Moscow firing its S-300 and S-400 missile systems. 

"On such a scale and with the deployment of different force groupings, such drills are being held for the first time," said defense ministry spokesman Igor Konashenkov highlighting the unprecedented nature of the massive show of Russian military force. "This training range is the biggest on the Crimean peninsula, which allows for such exercises to be held." 

The drills were overseen by Russian Defense Minister Sergei Shoigu and the head of the General Staff Valery Gerasimov as well as Crimean leader Sergei Aksyonov. 
"Strategic drills are essential to military training in Russia in 2016 with a focus on different troops working together. You should not twist this into anything – there’s no politics," explained Konvashenkov emphasizing that the drills should not be construed as a message to Russia’s neighbors despite the West’s rush to describe it as just that. 

The war games come one month after President Vladimir Putin accused Ukraine of sending a group of saboteurs into Crimea to engage in terror strikes against Russian personnel adding to Western suspicions that Moscow wants to make its control over the peninsula clear
Read more: https://sputniknews.com/russia/201609...

Moon’s pull can trigger big earthquakes

Geologic strain of tides during full and new moons could increase magnitude of tremors.

Joe Raedle/Getty Images

The seaside town of Pelluhue, Chile, in 2010 after a magnitude 8.8 earthquake and the resulting tsunami.

Big earthquakes, such as the ones that devastated Chile in 2010 and Japan in 2011, are more likely to occur during full and new moons — the two times each month when tidal stresses are highest.

Earth’s tides, which are caused by a gravitational tug-of-war involving the Moon and the Sun, put extra strain on geological faults. Seismologists have tried for decades to understand whether that stress could trigger quakes. They generally agree that the ocean’s twice-daily high tides can affect tiny, slow-motion tremors in certain places, including California’s San Andreas fault¹ and the Cascadia region² of the North American west coast.

Satoshi Ide, a seismologist at the University of Tokyo, and his colleagues investigated three separate earthquake records covering Japan, California and the entire globe. For the 15 days leading up to each quake, the scientists assigned a number representing the relative tidal stress on that day, with 15 representing the highest. They found that large quakes such as those that hit Chile and Tohoku-Oki occurred near the time of maximum tidal strain — or during new and full moons when the Sun, Moon and Earth align.But a new study, published on 12 September in Nature Geoscience³, looks at much larger patterns involving the twice-monthly tides that occur during full and new moons. It finds that the fraction of high magnitude earthquakes goes up globally as tidal stresses rise.

For more than 10,000 earthquakes of around magnitude 5.5, the researchers found, an earthquake that began during a time of high tidal stress was more likely to grow to magnitude 8 or above.

Breaking point

The Asahi Shimbun via Getty Images

A lone pine tree that survived the 2011 earthquake and tsunami in Japan.

“This is a very innovative way to address this long-debated issue,” says Honn Kao, a seismologist at the Geological Survey of Canada and Natural Resources Canada in Sidney. “It gives us some sense into the possible relationship between tidal stress and the occurrence of big earthquakes.” Perhaps the miniscule added strain of tides, he says, could be the final factor that nudges a geological fault into rupturing.

The current study will not be the final word on the matter, adds Kao. There are just too many factors that contribute to triggering an earthquake — such as how stress transfers within the ground to cause a geological fault to move — to untangle exactly what role tides might have.

But “the results are plausible”, says John Vidale, a seismologist at the University of Washington in Seattle who helped to debunk some of the more tenuous tide–earthquake claims⁴. “They’ve done a very careful job.”

The discovery does not affect how societies should prepare for possible earthquakes, says Ide. Even if slightly enhanced by the tides, the probability of a quake happening on any particular day in an earthquake-prone region remains very low. “It’s too small to take some actions,” he says.

Ide is now looking at an additional list of earthquakes that occur where plates with oceanic crust plunge beneath continental crust, to see if the pattern holds up there as well.