magnetic declination

Moon’s magnetic field lasted far longer than once believed

Rutgers and MIT experts lead lunar rock study with implications for life and habitability on other moons and planetary bodies

The moon’s magnetic field lasted 1 billion to 2.5 billion years longer than once thought - a finding with important implications for habitability on other moons and planets throughout the universe, a Rutgers University-New Brunswick professor says.

“The Earth’s magnetic field is a shield that protects us from dangerous solar wind particles and ionizing radiation, so magnetic fields play a key role in the habitability of planets and, possibly, moons,” said Sonia Tikoo, lead author of a study published online today in Science Advances and an assistant professor in Rutgers’ Department of Earth and Planetary Sciences.

“Without this shield, we’d have more radiation, we’d have lots of mutations and who knows how life would respond in an unstable environment like that,” said Tikoo, who began working on the study in 2013 while she was a graduate student at the Massachusetts Institute of Technology and who has examined more than 10 moon rocks. “It would be a harsher place to survive in.”

In their study, the researchers – for the first time – successfully heated a lunar rock brought to Earth during an Apollo space mission to retrieve an accurate intensity for the lunar magnetic field, she said. The energetic cores of planets and moons generate magnetic fields, and rocks can record magnetic fields to which they were exposed.

Tikoo reanalyzed a moon rock collected by the Apollo 15 crew on Aug. 1, 1971, on the southern rim of Dune Crater within eastern Mare Imbrium. The small, young rock – partially coated with melted glass – likely formed during a meteor impact on the lunar surface.

Tikoo used a rock magnetometer to analyze the lunar rock. The device measures the strength and direction of magnetic fields in rocks. She slowly demagnetized the rock to reveal its original magnetization, heating it to 1,436 degrees Fahrenheit in a controlled atmosphere chamber at MIT to keep the heat from altering the rock.

The researchers think the moon’s magnetic field declined by about 90 percent from its high point 3.56 billion years ago or earlier. That’s when the moon’s magnetic field was about the same strength as the Earth’s is today – an average of about 50 microtesla, a measure of magnetism. The lunar rock Tikoo tested, which is about 1 billion to 2.5 billion years old, recorded 5 microtesla.

The moon has no core-generated magnetic field today, and scientists don’t know when it turned off. Lingering questions include trying to figure out when the field ceased and what the field was like between 3.56 billion and 2.5 billion years ago, she said.

“We didn’t think that small planetary bodies could generate magnetic fields for a very long time because they have smaller cores that would cool quickly and crystallize early in their lifetimes,” she said.

“Because the rate of crystallization depends on the core composition, our finding may challenge what we think the lunar core is made of. It’s mostly made of iron, but something must be mixed in with it: sulfur, carbon or another element.”

When a planet’s magnetic field dies, ionizing particles from its sun can lead to the loss of its water over hundreds of millions of years, Tikoo said. “That’s a big deal in terms of habitability,” she said, adding that Mars once had lots of water but lost nearly all of it after its magnetic field died about 4 billion years ago.

“Whenever we look at exoplanets or the moons of exoplanets that could be in the habitable zone, we can consider the magnetic field as an important player in habitability,” she said. “Then the question becomes what size planets and moons should we be considering as possibly habitable worlds.”

IMAGE….The Apollo 15 breccia (rock) sample 15498 analyzed by Professor Sonia Tikoo of Rutgers University-New Brunswick. The rock consists of basalt fragments welded together by a dark glassy matrix that was produced by melting from a meteorite impact. The black scale cube is 1 centimeter across. Credit NASA

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Raindrops on roses and whiskers on kittens Bright copper kettles and warm woolen mittens Brown paper packages tied up with strings These are a few of my favorite things You’ll be humming that all day ;) 1. Ray Jardine uses a Victorinox Classic, but I reckon the Signature trumps it with a pen and tweezers. A whole tool/manicure set at 22g. 2. The Photon packs such a punch. I love lots of flashlights, but for EDC this is is as ‘light’ as it gets. Sowwy. 3. A Belgian master carver made this for me. I’d love to be able to carve as well as this. In Belgium they are called porridge spoons, but can be used for anything. A work of art. 4. This French Army satchel is my everyday bag. The inside is completely lined with the same brown leather. Bombproof. 5.Timepiece, masterpiece. Art Deco, 1922, green gold Abe Lincoln, 21 jewels. I could wax, so I’ll shut it. 6.Michael Morris is a wonderful maker of knives from the USA. He will make knives to suit you. Note this little devil has a hidden bottle opener. 7. Hat is old and battered but still keeps the weather at bay. I added some paracord, just in case. 8. This is Michael Morris’ EDC 60, made from an old file. 9. I wore this at my wedding so it means a lot. I usually only wear it when I wear a waisty 10. Copper imparts its fine purities into the water. Leave in the fridge overnight and all the goodies are there ready to be absorbed. 11. I copied this design shamelessly from a photograph. We need coins here so this fits the bill. I mean, the coin :) 12. This was my Grandad’s belt, handed down. Apparently it did service on my Dad’s derrière. 13. I made this to carry bits in, currently my fire stuff. 14. I always carry this loupe. At 20x it is excellent for seeing details in nature, and a splinter in your finger looks like a Cadbury’s flake in an ice cream! 15. Roger Harrington at Bison Bushcraft makes all his own excellent knives on special order. I am just about to get a new one after an 18 month backlog, so this is up for grabs. 16. I designed this case for a notebook a buddy had bought me. 17. I’m always looking at minimalist wallets and am currently designing a new one. This is an experimental fill-in, but very useful as it will just take a single folded £20 note, and about eight cards at a pinch. 18. Mr Pen in the UK is a wonderful gentleman, and gave sterling advice on purchasing a pen for life. My signature colour ink is sepia. It’s old, like me. 19. My handle on forums is White Knight, and part of my company logo. My white steeds have two wheels, however. 20. Just in case I spot that special piece of wood that has a spoon hidden in it. 21. I’m into Celtic stuff, and the triquetra is an ancient symbol, with many meanings eg eternity, earth symbols. Each of our wedding guests left with one. 22. A bandana has so many uses; I never leave home without one. 23. Fred Rowe is a wonder smithy. This feels great in the hand, and puts food on his table. Amen. 24. This compass is good enough for Ray Mears, and it works for me too. Love the magnetic declination adjuster and built-in clinometer. 25. This was supposed to last for at least ten years, and it’s 12 now. Still allows me to find my key easily in the dark. 26. This watch is so old they don’t make it any more. It is super accurate and was able to distinguish the height of two separate peaks 100m apart by three metres, saving me falling off a Scottish crag. 27. Making these bracelets is such good fun. It becomes a tad tiring when all your mates and their wives want one, however. 28. This means a lot to me as it was given by a special someone. Looks good on my sickles too. 29. Ray Mears even made me a case for my compass. Well, his lovely leather crafter Becky did, on his behest. I also use if for loads of other things - pack of cards, snifter flask etc. But not at the same time ;) 30. This was the first ever kuksa I made. It’s got lots wrong with it, but I use it all the time. Kuksa is Finnish for 'little cup’. 31.I switch cases but this is soo luxurious. Can you smell the leather from there? Samsung Note 4 fits in. I got a second Note 4 as the new 5 has no sd card / battery access. Humph, but I do love the phone, and the pen. The pen. NB. I usually only carry one of the knives, if it is appropriate to task, especially living in the UK.


The 18th Century Scientific Dream Team

Medical quackery has been a part of the human experience for thousands of years, going back to ancient times and still being practiced today. In the 18th century, the most popular medical fraud was a German physician and theologian named Dr. Franz Mesmer.  Mesmer believed that there was a natural energetic transference between inanimate and animate objects, a universal force he called “animal magnetism”. Mesmer claimed that he could control this energy, using it to heal people.  For decades he traveled around Europe “curing” people of various maladies, providing services to all people, from the poor lower classes to kings and emperors. Even Mozart was a follower of Mesmer, who composed a musical play in his honor. He often used techniques which would best be described today as hypnotism, thus his name forms the root of the word “mesmerize”.

 When French Queen Marie Antoinette became one of Mesmer’s clients in 1781, King Louis XVI immediately became suspicious.  Thus, he brought together some of the most brilliant thinkers of the age, a veritable Dream Team of 18th century scientists. First there was Antionne Lavoisier. A French scientist now known as the “Father of Modern Chemistry”, Lavoisier’s studies are detailed in the first dozen or so chapters of any high school or college chemistry book.  He is best known for discovering the Law of Conservation of Mass, the combustibility of oxygen, that diamonds are made of carbon, establishing that sulfur is an element not a compound,and credited with the naming of oxygen and hydrogen.  Second was Dr. Joseph Guillotin, an expert in human anatomy who helped pioneer early vaccination techniques.  He is often credited with inventing the guillotine, but in fact he didn’t, only suggesting it as a more humane alternative to execution techniques of the time. The third was an astronomer and mathematician named Jean Sylvain Bailly, who is known for discovering several of Jupiter’s moons. The fourth was Antoine Laurent de Jussieu, a botanist with a photographic memory whose work formed the foundation of modern taxonomic classification. The fifth was Jean Darcet, professor of chemistry at the College de France and the first person to manufacture porcelen in France. Finally, to round off the scientific dream team was the Great Sage and American inventor, Dr. Benjamin Franklin, then serving as US Ambassador to France as part of the American Revolution.  While today Franklin is best known for his studies in electricity, Franklin was an 18th century Renaissance man whose diverse fields of study included oceanography, meteorology, theoretical physics, fluid dynamics, medicine, anatomy and physiology, thermodynamics, demographics, political theory, civic activism, diplomacy, language, theology, music, economics, finance, optometry, sexuality, and human flatulance. King Louis XVI’s Commission on Animal Magnetism was “The Avengers” of late 18th century science.  Ben Franklin was the 18th century version of Tony Stark.     

In order to test Mesmer’s Theory of Animal Magnetism, the Dream Team proposed Mesmer take part in some simple tests, which were to be conducted  at Franklin’s residence in Passy. Instead of showing up personally, Mesmer sent one of his associates, a man named Dr.Charles Deslon, to take part in the experiment. Deslon explained to the scientists how animal magnetism worked.  As part of a demonstration, Deslon would “magnetize” one of the trees in Franklin’s collection of potted plants.  Deslon’s assistant, a boy wearing a blindfold, would then hug each tree, correctly declaring which tree was the one Deslon had magnetized. It was then that the Dream Team proposed that Deslon repeat his demonstration, except before the blindfolded boy tried to identify the “magnetized” tree, the trees were to be randomly moved and shuffled in order. In further attempts, the boy could not identify the magnetized tree, and the test ended when the boy faked a fainting spell.

The Dream Team called bullshit on Animal Magnetism, stating that the cures attributed to it may have either happened through a normal remission of the problem, or that the cure was a form of self delusion.  Mesmer was outraged by the finding, first blaming Deslon for failing to manipulate Animal Magnetism properly, then claiming that the act of testing Animal Magnetism itself created flawed results.  In other words, a peculiar trait of Animal Magnetism was that it could not function under scientific investigation, and thus could not be tested.  After the experiment, belief in Mesmer and his Animal Magnetism began to decline, however it dragged on in medical theory until the mid 19th century. After a job well done. the 18th Century Scientific Dream Team retired to a local pub, where Ben Franklin got them all drunk and they all had a wild sex orgy with many women. (I made up that part)

Magnetic declination

Also called magnetic variation, it is defined as the angle between compass north and true north at a point on the Earth. Compass north is the direction shown on the north end of a compass needle while true north is the actual direction on the Earth’s surface pointing toward the geographic North Pole. Magnetic declination changes based on one’s location on the globe and as a result it is very important to surveyors, map makers, navigators and anyone using a compass to find their direction such as hikers. Without adjusting for magnetic declination work done by surveyors could turn out wrong and people like hikers using a compass could easily get lost.

Before learning about the essentials of magnetic declination it is important to first learn about the Earth’s magnetic field. The Earth is surrounded by a magnetic field that changes in time and location. According to the National Geophysical Data Center this field resembles the magnetic field generated by a dipole magnet (one that is straight with a north and south pole) that is located at the center of the Earth. In the case of the Earth’s magnetic field the axis of the dipole is offset from that of the Earth’s rotation by around 11 degrees.

Because the Earth’s magnetic axis is offset the geographic north and south poles and the magnetic north and south poles are not the same and the difference between these two is magnetic declination.

The Earth’s magnetic field is very irregular and it changes with location and time. This irregularity is caused by variations and movement of material inside the Earth’s interior that occur over long periods. The Earth is made up of different types of rock and molten rock that have different magnetic properties and as they move around inside the Earth, so too does the magnetic field.

According to the Wisconsin State Cartographer’s Office, variation inside the Earth “causes a ‘drift’ of magnetic north and oscillations of the magnetic meridian.” The normal change of magnetic declination is called annual change and it is very difficult to predict over long periods.

The only way to predict changes in magnetic declination is to take various measurements in many locations. This is typically done via satellite and maps are then created for reference. Most maps of magnetic declination are made with isolines (lines representing points of equal value) and they have one line along which magnetic declination is zero. As one moves away from the zero line there are lines showing negative declination and positive declination. Positive declination is added to orient a compass with a map, while negative declination is subtracted. Most topographic map salso state the magnetic declination for the areas they show in their legend (at the time the map was published).

When stating magnetic declination it is important to pay attention to whether the calculated declination is positive or negative. A positive declination shows an angle that is clockwise from true north and a negative is counter clockwise.

An easy and often inexpensive tool to use for navigation is a compass. Compasses operate by having a small magnetized needle that is placed on a pivot so that it can rotate. The Earth’s magnetic field places a force on the needle, causing it to move. The compass needle will rotate until it aligns itself with the Earth’s magnetic field. In some areas this alignment is the same as true north but in others magnetic declination causes the alignment to be off and the compass must be adjusted to avoid getting lost.

Image credit: Balderas 2009/Getty Images
Earth's Magnetic Field Declination from 1590 to 1990 - Wikipedia, the free encyclopedia

(frelling Tumblr, won’t post the damn gif directly)


See, the magnetic North and South Poles - which magnetic compasses point to - aren’t quite at the same places as the ones the earth actually rotates around. So your magnetic compass might not point “true [rotational] north”. Depending where you are on earth, it may be off by several degrees.

And how much it’s off? Depends on not only where but when you are. It changes. Before gyrocompasses started being used in the early 1900s, you had to correct your magnetic compass using an up-to-date map of “magnetic declinations” if you were traveling a long way and wanted to actually get where you were going.

This is an animation of ALL those maps, from 1590 to 1990. You can literally see here how the earth’s magnetic field has shifted in the last 400 years. BECAUSE SCIENCE. ^_^