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Earth's Constant Hum Explained 336

MattSparkes writes "It has been known for some time that there is a constant hum that emanates from the Earth, which can be heard near 10 millihertz on a seismometer. The problem was that nobody knew what caused it. It has now been shown that it is caused by waves on the bottom of the sea, and more specifically 'by the combination of two waves of the same frequency travelling in opposite directions.'"
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Earth's Constant Hum Explained

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  • by Anonymous Coward on Friday February 16, 2007 @06:32AM (#18036738)
  • by MattSparkes (950531) on Friday February 16, 2007 @06:37AM (#18036764) Homepage Journal
    When I'm in a quiet room I can often hear a quiet hum. It started after I went to an Arctic Monkeys concert...
  • by niconorsk (787297) on Friday February 16, 2007 @06:42AM (#18036782)
    I've always just assumed it was the Earth purring.
  • please (Score:5, Funny)

    by baldass_newbie (136609) on Friday February 16, 2007 @06:45AM (#18036796) Homepage Journal
    For the love of God, make it stop!
  • That, or it is the power plant of an alien base hidden in the hollow shelf off the Vancouver coast. Or both.
  • Damn (Score:5, Funny)

    by sharp-bang (311928) <(sharp.bang.slashdot) (at) (gmail.com)> on Friday February 16, 2007 @06:52AM (#18036818) Homepage
    So all this time I guess I should have put the tinfoil in my shoes.
    • For some reason I read that in completely the wrong tone.

      "So all this time I guess I should have put the tinfoil... in my shoes!"

      I'm currently at university, and have had to endure hearing every other sentence ending with "in my pants!", so that might explain it...
  • by crosbie (446285) <crosbie@digitalproductions.co.uk> on Friday February 16, 2007 @06:56AM (#18036824) Homepage
    ...as Douglas Adams might have said.
    • by Veetox (931340) on Friday February 16, 2007 @07:33AM (#18036990)
      You may be closer to the truth than you know: $10 (Yeah, I know I'm cheap...) says that researchers will later find out that human activity is impeding the waves and if that impediment continues, it will ruin biological interactions all over the planet... Yeah, you know whats going to happen: monkeys falling out of trees, birds migrating the wrong way, and lesbian women becoming sexually attracted to nerds. Also, hell freezing over.
  • Wow (Score:5, Funny)

    by Anonymous Coward on Friday February 16, 2007 @06:58AM (#18036836)

    All this time, I just assumed it was because it couldn't remember the words.

    • Re: (Score:3, Funny)

      by mmdog (34909)

      All this time, I just assumed it was because it couldn't remember the words.

      Actually the earth knows the words but was concerned that the RIAA might sue.

  • Why? (Score:2, Interesting)

    by khristian (1009227)
    I think these people "researching" it have too free time in their hands...

    (...)This creates a standing wave that "goes thump, thump, thump on(...)
    Sound more like a kid that's happy for having found out how something works. Well, if that keeps 'em happy, they should go for it ^^
  • by torrija (993870) on Friday February 16, 2007 @06:59AM (#18036840)
    I think this is a concept related to Pythagoras' Musica Universalis http://en.wikipedia.org/wiki/Musica_universalis [wikipedia.org]. An inaudible sound on all celestial bodies.
    • Re: (Score:3, Insightful)

      by kestasjk (933987) *
      No, Pythagoras didn't have a seismometer capable of detecting 10 millihertz..
  • Hmmmmmmmm (Score:5, Insightful)

    by dcw3 (649211) on Friday February 16, 2007 @07:01AM (#18036850) Journal
    Ok, so the waves are making the sound. Now tell us what causes the waves. I didn't notice a source in TFA.
    • by FormOfActionBanana (966779) <slashdot2@douglasheld.net> on Friday February 16, 2007 @07:08AM (#18036896) Homepage
      The Thetans?
    • But wait! (Score:5, Interesting)

      by camperdave (969942) on Friday February 16, 2007 @07:21AM (#18036952) Journal
      ...the waves are making the sound.

      Wait a minute. How do we know that it's the waves that are causing the hum, and not the other way around? Perhaps the planet is still ringing from meteor impacts, and the hum is just the resonant frequency. The deep ocean waves may be just a side effect.
      • by radtea (464814)
        How do we know that it's the waves that are causing the hum, and not the other way around? Perhaps the planet is still ringing from meteor impacts, and the hum is just the resonant frequency.


        Note to mods: you misspelled "funny".
      • Re: (Score:3, Insightful)

        by rucs_hack (784150)
        given the fact that most natural systems exist in some kind of homeostatic relationship with other systems, its likely that the cause is rather complex. I wouldn't have a clue where to start.

        That's what I love about science though, there's yet another thing to explain. I wonder what it will reveal?
    • by Lumpy (12016)
      Ok, so the waves are making the sound. Now tell us what causes the waves.

      The exaust ports on the engines.... DUH!
    • Re:Hmmmmmmmm (Score:4, Informative)

      by ChrisA90278 (905188) on Friday February 16, 2007 @11:37AM (#18039494)
      "Now tell us what causes the waves."

      The answer is "wind" this has been known at least a century, no need to put it in the article. Now you ask what makes wind. This to has been known for a long time, the basic answer at the bottom of all of this is uneven heating of the atmosphere by solar radiation. Why "uneven"? The Earth is not uniform all over it's surface? Why is that? Something about plate tectonics? Why is that? The core is liquid and the "lighter" crust floats on the liquid while the liquid circulates. You can go on forever.....

      But seriously, wind blowing over water causes ripples, the hight and period of the riples depends on the speed of the wind and the "fetch". Fetch being the distance the wind has to act on the water.
  • by Dr. Eggman (932300) on Friday February 16, 2007 @07:02AM (#18036864)
    Your article was very interesting, but it's wrong. I have a better idea. You see, the center of the earth is full of bees. They make the earth hum and the turtle stack keeps turning to find out what's buzzing. You see? Mine's a much better explaination: explains the humming and the rotation of the Earth!
    • Re: (Score:3, Informative)

      by Prune (557140)
      This would have been funny except you seem to lack reading comprehension. The article said ten MILLIhertz! That's a single beat every hundred seconds. Bees' buzzing is about three orders of magnitude higher in frequency.
    • No, No, No! The sound is caused by the spirits of dead pirates all saying "Arrgh." His Noodlyness merely alters the frequency so we think it's caused by waves. Yet more proof of his existence.
    • Re: (Score:2, Redundant)

      by Dunbal (464142)
      Phooey. Those of us who keep the faith know all along that it's a giant dragon imprisoned beneath the Earth, and you're merely listening to his snore. How do you explain earthquakes and volcanoes with BEES? The dragon makes much more sense. Convert now, unbeliever!

            While we might accept the turtles, our wise men actually explain to us that the last turtle is actually standing on a dog that is chasing it's own tail - which explains the rotation.
  • Whales (Score:5, Funny)

    by Fist! Of! Death! (1038822) on Friday February 16, 2007 @07:06AM (#18036874)
    It is probably driving the whales crazy. They think it's the Voices...
    • Re: (Score:3, Insightful)

      by Prune (557140)
      This would have been funny, except the ten MILLIhertz frequency (one beat per hundred seconds) is a couple of orders of magnitude lower than what whales can hear.
  • by Centurix (249778) <centurix AT gmail DOT com> on Friday February 16, 2007 @07:07AM (#18036882) Homepage
    When I shutdown my PC. Turns out the bearing was on its way out.
  • hertzs (Score:5, Informative)

    by mapkinase (958129) on Friday February 16, 2007 @07:24AM (#18036960) Homepage Journal
    10 milliHz is a beat every 100 seconds. Must be really tricky to detect. I wonder how far below that frequency the sensitivities of seismometers go.

    http://en.wikipedia.org/wiki/Seismometer#Modern_re cording [wikipedia.org] mentiones only down to 1Hz. Need to see original article in Nature from work.
    • Well many seismometers are constantly on and have very long periods of this noise recorded.
      So with enough stacking you can pretty much detect as low frequencies as you want if only the amplitude is strong enough to be detected by the seismometers, so my guess is that the limiting factor is not the 1 Hz, but lies in how small amplitudes these seismometers detect.

      These suggested waves would hold quite an amount of energy so it does make sense that they are able to detect these to me.
      • by mapkinase (958129)
        May be it could be related to the noise of higher frequencies. I do not see a problem detecting amplitudes in the absence of that noise.
  • Balrog (Score:5, Funny)

    by tore (26817) on Friday February 16, 2007 @07:32AM (#18036988)
    I always thought it was the Balrog humming.
  • by 140Mandak262Jamuna (970587) on Friday February 16, 2007 @07:34AM (#18036996) Journal
    These atheistic God-denying scientists attribute the constant hum detected by the seismometers to some random wave action at the ocean floors. But they ignore the fact that it violates the second law of thermodynamics (whatever it is). The real cause for the hum is the intelligent shaking by the Shaker. We demand equal time in all classrooms and seminars and conferences, wherever these surfologists congregate to rebut their theory (not fact) with our scientifically formulated real sceintific fact that intelligent shaking is the fundamental cause for all the hum on earth.
    • Actually the hum is the planetary ring down of the violent shaking the earth received after the continents rapidly moved to their present locations due to a global-scale flood tectonic cataclysm. BTW I predict that the magnitude of this hum is exponentially decaying just like the speed of light and earth magnetic field.
  • by fmobus (831767) on Friday February 16, 2007 @07:37AM (#18037018)
    If this humming is omnipresent, it means that every music is "sampling" it without authorization. We then sue RIAA out of existence for unlicensed sampling.
  • by hey! (33014) on Friday February 16, 2007 @07:44AM (#18037060) Homepage Journal
    Nobody's figured out how to ground the dang thing.
  • If I know which one maybe I can tune it to make music and really stump the scientist.
    (re: my user handle)
  • Throbbing (Score:2, Insightful)

    by andrewuwe (997499)
    10 millihertz sounds more like a throb than a hum to me, perhaps even a chug.
    • Re: (Score:3, Interesting)

      by mysticgoat (582871)

      It's more like "bang the drum softly". Once every ten seconds.

      So are there any biological processes that are using this omnipresent beat for a clock frequency? Do any of the intracellular membranes we are familiar with quiver in resonance with the Earth beat? Would it be possible to predict the shape of such a biological structure?

      I'm guessing that life has found a way to take advantage of this constant beat to organize sequences of activity. If that it so, there would be health consequences for astrona

  • I have an idea (Score:5, Interesting)

    by LaughingCoder (914424) on Friday February 16, 2007 @08:09AM (#18037206)
    Maybe we could build a clock that used this hum as some sort of synchronization. Then every clock on the planet could be synchronized, since this signal is presumably detectable everywhere.

    OK, I didn't say it was a *good* idea :-)
    • by hcdejong (561314)
      If the sound originates on the seafloor, you presumably need to account for propagation delays. If the sound is generated over a large area, it'll be muddled enough that you won't be able to lock onto a specific phase of the soundwave. Also, TFA doesn't say how regular the sound is. If it's 10 mHz +/- 50%, you've got too much clock drift to be usable.
  • That was just the bass on my kickin' car stereo. I turned it down, so it shouldn't be a problem. Those nine-foot quartz drivers are tite!

    But seriously, how much power would it take to put such a vibration into the air, and how far would it travel? I'm just picturing the hair on my head blowing this way and that way with the changes in sound pressue.
  • what's driving the very low frequency waves then??? Atmospheric turbulence??? Which if so, would mean that the indirect cause of the "hum" IS atmospheric turbulence...
  • To paraphrase DNA, "Maybe it just feels good about being a planet?"
  • by mtec (572168) on Friday February 16, 2007 @08:59AM (#18037566)
    We're living inside an inter-galactic boy band.

    Venus is the hot one and will turn out to be gay (natch, I mean Venus?)
    Earth is the um, down-to-earth one - full of life.
    Mars - the cold and distant one - always at war with the other members
    Jupiter - slightly overweight - jolly
    Saturn - Gaudy over-compensator wears lots of jewelry and rings - looks up to Jupiter

    Hot headed Mercury - left in a huff to form his own band - his manager is the real star though.
    Uranus was an asshole and left before fame came.
    Neptune - always blue, committed suicide after what happened to Pluto...
    Pluto? Well, Pluto was thrown out when it was discovered he never could sing.
  • The Spongebob Squarepants cartoon was accurate all the time when it showed that there ARE beaches on the bottom of the ocean!!! We now know for sure that they have waves and everything. Who need Atlantis? If we could only find Bikini Bottom.
  • Not quite right (Score:4, Interesting)

    by unixfan (571579) on Friday February 16, 2007 @09:23AM (#18037812) Homepage
    All objects have a mean frequency which in this example is causing the frequency that they are observing in the water. The frequency in the water comes from the planet's own resonance, or a harmony thereof.

    Tesla noticed this and build a little tool which hit on the harmonic frequency and kept accelerating the oscillation with a device he built until there were "earthquakes" observed all around, and he had to cut short a trip to run home and turn it off. Indeed in manufacturing speakers you try to get this frequency down below audioble range as you don't want the speaker to resonate and alter the sound it's supposed to generate.

    It's a very common mistake made by many when they observe a symptom (not realizing there is a real why behind it.)
  • this is what I found (Score:5, Interesting)

    by mapkinase (958129) on Friday February 16, 2007 @09:24AM (#18037828) Homepage Journal
    Article reporting the milliHz hum in 1998 [sciencemag.org]
    IDA (International Deployment of Accelerometers) [ucsd.edu] used to detect the hum.
    Article in Nature (1979) [nature.com] assesses if IDA can be used to detect very low frequency seismic data. Looking at the figure 1 of amplitude(?) ("MD counts" at Rarotonga station not shown on the current IDA map [ucsd.edu]) I can see the aftershocks in 2 hour intervals after the Indonesia earthquake, but the subj frequencies could be detected only by obtaining the spectrum (Fig.2) at mHz range which frankly looks like white noise - irregular beats.

    Most interesting figure is Fig.3 which shows the 0.43-0.52mHz of the _processed_ spectrum measured at six different stations around the world at Hour 25 and on. The Alaska station (CMO) has much clearer spectrum compared to the closest (?) RAR station.

    All of it must have meant something for a seismologist which I am not.
  • by jhfry (829244) on Friday February 16, 2007 @09:26AM (#18037860)
    If our whole planet were vibrating at a constant frequency... it seems to be that there is a lot of energy in that hum... any way to harness this?
  • Rachel: It's coming from Joey

    Phoebe: Oh my God turn him off!
  • ..I'll stop now.
  • by peter303 (12292) on Friday February 16, 2007 @12:51PM (#18040822)
    A key breakthough was figuring out how to locate continuous signals. For normal earthquakes you have a sharp beginning. Using four or more seismographs you can invert for x,y,z and t0 (called triangulation).

    For continuous signals you can find source by cross-corelating long pieces of signal from multiple locations. I first saw this in ambient noise submarine location, but the seismologists have now adopted it for analyzing some kinds of difficult signals like hum.

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