Non-Spherical Magnetic Cows!

By Mark Trodden | August 26, 2008 1:54 pm

Physicists often simplify or idealize phenomena to make them more amenable to an initial mathematical treatment. We jokingly refer to this as considering a “spherical cow”. Sometimes one can understand even very subtle phenomena using this technique. However, there are always important effects that one needs the full, non-symmetric nature of the situation to understand.

Here, from The Telegraph, is an example of experimental data illustrating just this point (emphasis mine)!

Dr Sabine Begall and colleagues from the University of Duisburg-Essen looked at thousands of images of cattle on Google Earth in Britain, Ireland, India and the USA. They also studied 3,000 deer in the Czech Republic. The deer tended to face north when resting or grazing.

Although, in many cases, the images were not clear enough to determine which way the cattle were facing they were aligned on a north/south axis.

The scientists concluded that they were behaving in the same way as the deer.

Huge variations in the wind direction and sunlight in the areas where the beasts were found meant that the scientists were able to rule out those factors as being responsible for the direction they were facing.

“We conclude that the magnetic field is the only common and most likely factor responsible for the observed alignment,” the scientists wrote in an article published in the Proceedings of the National Academy of Sciences journal.

All joking aside, I found this fascinating. It is hard to see why this feature would be useful to cows these days, but if you accept the evil theory of evolution, things become a lot clearer.

Their innate ability to find north is believed to be a relic from the days when their wild ancestors needed an accurate sense of direction to migrate across the plains of Africa, Asia and Europe.

  • Michael Bacon

    To test the theory they’ll need to put magnets on thousands of cows and see if it affects how they orient themselves. It was a great story.

  • Kenneth Finnegan

    Couldn’t it be something more mundane like: they face North so the sun is never in their eyes? All the countries they studied are in the Northern Hemisphere…

  • Jolly Bloger

    I dunno… even if cows had an internal compass to help them navigate while on the move, that doesn’t explain why they would stand facing north while grazing. My first intuition is that a north/south orientation maximizes the heat they get from the sun – their broad sides are always facing the direction of the sun. That wouldn’t explain why they choose north specifically rather than either north or south, but as you have pointed out, they don’t KNOW that the cows were facing north specifically, and the deer only “tended” to face north. How strong is the tendency, I wonder?

    I love the title of this post. I used to describe undergrad physics as “where cows are spheres, spheres are points, and friction can always be ignored.”

  • Jolly Bloger

    Also, I wonder if they accounted for the time of day. Perhaps the deer and cows face north in the morning, and south in the afternoon (or vice versa) because of some internal asymmetry – for example they want to heat their hearts, which are further left.

  • starwed

    However, there are always important effects that one needs the full, non-symmetric nature of the situation to understand.

    To be fair, the dipole term is probably enough here…. :)

  • insider

    I believe the technical term is Spontaneously Non-Spherical Cows (a.k.a. cows).

    P.S. Moo!

  • michaelspierce

    Actually… Anyone know if they’re still putting magnets in cows? ie the canonical “cow magnet” seen in freshman EM courses? There seem to be plenty of websites still selling them for use as a cow magnet.

    Not having a gauss meter, nor a cow magnet handy, and only my memory to work off of…. It seems like depending upon the orientation of the magnet you might get at least 1-10 gauss within 5.-1 meters of the magnet (that’s a guess, I should really look up a real starting point and make an estimate, but sigh…) Since the strength of the earth’s field is usually around 1/2 a gauss… do cows with magnets align to their own field from within their stomachs?

    Or to put it another way… if the cows have magnets that are randomly oriented inside them producing fields comparable (or potentially much larger) to the “sense organ”, then how can they align to the earth’s field?


  • http://deleted Simon DeDeo

    Is there a B-mode detection in the cow polarization field?

  • Lab Lemming

    succinct version: “When we assumed that all equivocal data supported our hypothesis, support was found.”

  • Michael Bacon

    “Couldn’t’t it be something more mundane like: they face North so the sun is never in their eyes?”

    “My first intuition is that a north/south orientation maximizes the heat they get from the sun . . .”

    “if the cows have magnets that are randomly oriented inside them producing fields comparable (or potentially much larger) to the “sense organ”, then how can they align to the earth’s field?”

    So, attach magnets to the cows and see if it affects how they orient themselves. If it does have a statistically significant impact, then at least we know that maganetism may well have something to do with the original hypothesis.

  • charly

    “The deer tended to”, “huge variations”. What is this, liberal arts? We’re scientists, were is the statistical data?

  • Mike Bevington

    The magnets may interfere with the cows’ directional ability but they’ll double their gas milage.

  • kurt

    National Geographic is reporting this also


    Some relevant quotes:
    “The magnetic field of the Earth has to be considered as a factor,” the scientists said.

    Two-thirds is close to what the researchers found in their look at 8,510 cattle in 308 pastures. In the study, 60 percent to 70 percent of cattle were oriented north-south, which Begall termed a “highly significant deviation from random distribution.”

    Hinchley stressed that one factor that must be considered is cow comfort.

    “They don’t like to get hot. Their body temperature is 102, and they are wearing black leather jackets, literally! If turning north-south would keep them cooler, they would stand that way.”

    The research team noted that in very windy conditions cattle tend to face the wind, and have been known to seek out the sun on cold days. But they said they were able to discount weather effects in the study by analyzing clues such as the position of the sun based on shadows.

    It would be interesting if it were true but I am still very skeptical.

  • Mark

    Guys – its a (not particularly good) newspaper article about a study, not the study itself.

  • Plato

    I had heard the term “spherical cows” before but I could not place it. On a quick search I found this below

    Spherical cow is a metaphor for highly simplified scientific models of reality. The phrase comes from a joke about theoretical physicists:

    Milk production at a dairy farm was low so the farmer wrote to the local university, asking help from academia. A multidisciplinary team of professors was assembled, headed by a theoretical physicist, and two weeks of intensive on-site investigation took place. The scholars then returned to the university, notebooks crammed with data, where the task of writing the report was left to the team leader. Shortly thereafter the farmer received the write-up, and opened it to read on the first line: “Consider a spherical cow. . . see variant on this. .”[1]

    [1] Harte, John (1988), Consider a Spherical Cow: A Course in Environmental Problem Solving, University Science Books, ISBN 978-0935702583

  • JR

    If the cows are spheres, how were they able to determine any orientation?

  • Plato

    The article is supposed to be a joke on the methods used? :)

  • Traums

    Yeah, I doubt 3000 pictures from Google Earth makes for a reliable sample space for observation. As was suggested, a lab controlled test is in order.
    THe body heat hypothesis has more weight to it.

  • TwisMinion

    I like Kenneth Finnegan’s guess about not wanting the sun in the eyes the best… a most plausible alternative anyway…

    also, while 60 to 70 % north south facing is interesting, it’s not as chilling a frequency as say 80 to 90 % would be…

    still… it’s not unheard of in other farm animals…

    and the fact that this sort of number crunching on grass munching creatures exists at all is very cool…


  • TwisMinion


    It’s the spin of the spherical cow that determines orientation…

  • Blake Stacey

    In case I missed somebody else giving a pointer to the study itself, here you go.

    Sabine Begall et al. (25 August 2008) “Magnetic alignment in grazing and resting cattle and deerPNAS direct submission.

    We demonstrate by means of simple, noninvasive methods (analysis of satellite images, field observations, and measuring “deer beds” in snow) that domestic cattle (n = 8,510 in 308 pastures) across the globe, and grazing and resting red and roe deer (n = 2,974 at 241 localities), align their body axes in roughly a north–south direction. Direct observations of roe deer revealed that animals orient their heads northward when grazing or resting. Amazingly, this ubiquitous phenomenon does not seem to have been noticed by herdsmen, ranchers, or hunters. Because wind and light conditions could be excluded as a common denominator determining the body axis orientation, magnetic alignment is the most parsimonious explanation. To test the hypothesis that cattle orient their body axes along the field lines of the Earth’s magnetic field, we analyzed the body orientation of cattle from localities with high magnetic declination. Here, magnetic north was a better predictor than geographic north. This study reveals the magnetic alignment in large mammals based on statistically sufficient sample sizes. Our findings open horizons for the study of magnetoreception in general and are of potential significance for applied ethology (husbandry, animal welfare). They challenge neuroscientists and biophysics to explain the proximate mechanisms.

  • Jason Dick

    I’m not so sure about the “sun in the eyes” idea. Remember that cows have eyes on the sides of their heads. They’d have to have their backs pointing almost directly at the Sun to not have it in their eyes, which would make sense, but would also be easily detectable from an analysis of the satellite imagery, as it would be possible to measure a difference in orientation between morning and afternoon. So, I don’t know. Maybe, but it doesn’t require any new observations to check. So it would somewhat surprise me if it hasn’t already been checked.

  • Plato

    If one has a particular bend toward their research perspective one might from this angle with regard to the New Scientist article think it is indeed a joke? :)

  • rob

    i read in one blurb about this study that the cows didn’t just face north, they faced *magnetic north*, which varies depending on where the cows are.

    i wonder if you can use a cow to attach things to your refrigerator?

  • Contrary

    Magnetic North deviates from True North (by about 12 degrees in Montana) so you would think that if there *were* any magnetic effect, it would show as a bias from True North, increasing as you travel up through Canada.

    Unless they are simply aligning with the local power grid or fenceline. Birds align as part of their flocking behavior, herds may have a migratory directional sense.

  • Jonathan Vos Post

    When the magnets are switched on at LHC, do nearby cows wander across the landscape, or give milk which is better for making string cheese?

  • Moshe

    Actually, seems to me this demonstrates one of the weaknesses of evolution, the fact that it can stretched to support non-quantitative “just so stories”, to explain pretty much any fact (or its converse). I can certainly think about a few stories, at the same level of detail, explaining the cows aligning in the east-west direction, or in no direction at all.

  • Sili

    My sister is a cowherd (I kid you not) and she shared my intuition that cows tend to stand with their arse to the wind.

    The sun hypothesis only works if all aerial photographs are taken within a few hours of noon. Does anyone know if that’s the case?

    But of course the next step is to find a goodish number of freerange farms, put up some webcams and equip the cattle the strong magnets (cowmagnets would indeed prolly be enough, but they’d prolly have to be fitted externally is the experiment is to last long enough to reach statistical significance).

    I’m looking forward to the next batch of results.

  • PeterS

    I don’t think you can rule out the linear nature of their food as a contributing factor

  • Alex

    In the orignal report on this story as reported around the world, the explanation is given as being ” parsimonious”.

    No one apparently noticed this crucial fact. The word really means stingy with money. Nothing to do with cows or magnetism. Maybe this misuse of english is a clue that the whole story is a prank on the scientific world.

  • daisy rose


    Maybe so – but I looked at photographs of cows I took – and they were all pretty much facing either north or south; to my surprise mostly north – The cattle farmer said they lie any which way there is room.

  • Nathan Myers

    “Parsimonious” refers to the grant committee. It’s a subtle hint reminding them that only a little more money would have produced much more compelling results. Unfortunately grant committees are completely deaf to subtlety.

  • bane


    “parsimonious” with the meaning of “using as few resources as remotely possible” (although often applied to money) is frequently used in learning theory. Saying an explanation is parsimonious is basically applying Occam’s razor with mentioning competing more complicated theories.

    The big thing here is that a paper that’s an interesting quick-and-dirty experiment’s write-up, which might be followed up with more monetarily expensive equipment if a grant could be obtained, has been picked up by all sorts of general media and presented so that it seems like a bold, definitive statement.

  • bane

    Ugh, that should be “Saying an explanation is parsimonious is basically applying Occam’s razor without mentioning any competing more complicated theories.”

  • Lab Lemming

    I have always wondered why it is that cows grazing under power lines oscillate 60 times per second…

  • Jolly Bloger

    No one has mentioned predators… What are the wolves doing? A deer’s number one concern – above grazing, above body heat, above migration, and way above sun in his eyes, is avoiding wolves. Predators will attack from downwind, so as not to be detected. I have also heard that they will minimize their silhouette when standing on a hill (no idea if this is actually true). What other tactics could predators be using related to sun position or magnetic direction that the cows and deer could be watching or smelling for?

    The problem with that theory is that cows don’t really have to worry about wolves. Any anti-predator behaviour would have been artificially bred out long ago. Then again, so would migratory behaviour, as they don’t have to worry about that either. What possible selection pressures do cows currently face, that they share with deer, that could explain the orientation?

  • swety

    I agree with Mark. Truly this is a news paper article about a study .I love the title of this post.

  • John R Ramsden

    “My sister is a cowherd (I kid you not) and she shared my intuition that cows tend to stand with their arse to the wind.”

    As cows don’t use loo paper, maybe another advantage for them in standing with backs to the sun and/or wind is that this will tend to dry their hindquarters quickest. Also the sun’s UV radiation will help sterilize any mess round the cow’s tail, and maybe even dry out and kill parasite eggs laid by things like flies.

  • Jonathan Vos Post

    At last, we can do perturbation analysis as a function of the radius of spherical cows, in our grazing/search for the Unified Field Theory (original meaning of “field”).

    August 17, 2008
    Just right for the garden: a mini-cow
    Miniature cattle farming is catching on with families trying to stay ahead of rising food prices
    Chris Gourlay

    It’s the little cow with a big future. Rising supermarket prices are persuading hundreds of families to turn their back gardens into mini-ranches stocked with miniature cattle.

    Registrations of the most popular breed, the Dexter, have doubled since the millennium and websites are sprouting up offering “the world’s most efficient, cutest and tastiest cows”.

    For between £200 and £2,000, people can buy a cow that stands no taller than a large German shepherd dog, gives 16 pints of milk a day that can be drunk unpasteurised, keeps the grass “mown” and will be a family pet for years before ending up in the freezer. …

  • Sandy

    Its time to study the direction the grasses and forbs are leaning, likely towards the sun. If that is towards the south, the yummy seed heads would be easier to get at while facing north.

  • danajohnson0

    As the greatest intellectual danger a cow can suffer is the terrible North wind of blizzards, I can’t be much confused. We know that humans are made ‘special’ to think, with all other many legged things not quite so effortful at intelligent behavior….lets see…
    The greatest mass exposure for warming in the comfort weather would be N/S or S/N, with the head to North in the low angle sun of the cold winter, still the better statistical preference, while habituated from the bad weather periods.
    In the high summer, the North facing animal still avoids the sun on the head preferentially.
    I have always believed this process was at fault for weakening the survival skills of the Dinosaur types of the past- a migration process gone bad statistically, additional to other reasons. It is claimed that many dinosaurs commonly used the head and nasal passages for cooling mechanisms, requiring they be facing the North preferentially during the year, or alternating E/W during the days travel path,avoiding the sun angle, in a reversal of paths without gain during weather stress.
    Now, am I thinking just like a cow, or not?
    site included as a link at top to quell the stressed humans, as again, they are sure the ‘other’ group has the upper hand intellectually, and we must therefore dwell on the natural.
    Why do humans prefer north facing homes? Cool idea, or not?
    My real thinking here:

  • danajohnson0

    I would like to defend my supposition with one additional observation, as the details are accumulative when an argument is finalized. Humans use the same technique to dress themselves, warming the backsides greater than the front, as a sign of polarity in coping. Not non-symmetric, axial, as would be expected of most tetra-pods.

  • NickP

    This may be the right occasion to reexamine the navigational practices of the Vikings. Perhaps the etymology of L’Anse aux Meadows really should reference fields of grass instead of jellyfish, since clearly the Vikings were seeking fodder for their quadrupedal compasses when they landed in Newfoundland.


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Cosmic Variance

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About Mark Trodden

Mark Trodden holds the Fay R. and Eugene L. Langberg Endowed Chair in Physics and is co-director of the Center for Particle Cosmology at the University of Pennsylvania. He is a theoretical physicist working on particle physics and gravity— in particular on the roles they play in the evolution and structure of the universe. When asked for a short phrase to describe his research area, he says he is a particle cosmologist.


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