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Space Science

Is Earth Weighed Down By Dark Matter? 247

Nerval's Lobster writes "There may be a giant ring of dark matter invisibly encircling the Earth, increasing its mass and pulling much harder on orbiting satellites than anything invisible should pull, according to preliminary research from a scientist specializing the physics of GPS signaling and satellite engineering. The dark-matter belt around the Earth could represent the beginning of a radically new understanding of how dark matter works and how it affects the human universe, or it could be something perfectly valid but less exciting despite having been written up by New Scientist and spreading to the rest of the geek universe on the basis of a single oral presentation of preliminary research at a meeting of the American Geophysical Union in December. The presentation came from telecom- and GPS satellite expert Ben Harris, an assistant professor of mechanical and aerospace engineering at the University of Texas- Arlington, who based his conclusion on nine months' worth of data that could indicate Earth's gravity was pulling harder on its ring of geostationary GPS satellites than the accepted mass of the Earth would normally allow. Since planets can't gain weight over the holidays like the rest of us, Harris' conclusion was that something else was adding to the mass and gravitational power of Earth – something that would have to be pretty massive but almost completely undetectable, which would sound crazy if predominant theories about the composition of the universe didn't assume 80 percent of it was made up of invisible dark matter. Harris calculated that the increase in gravity could have come from dark matter, but would have had to be an unexpectedly thick collection of it – one ringing the earth in a band 120 miles thick and 45,000 miles wide. Making elaborate claims in oral presentations, without nailing down all the variables that could keep a set of results from being twisted into something more interesting than the truth is a red flag for any scientific presentation, let alone one making audacious claims about the way dark matter behaves or weight of the Earth, according to an exasperated counterargument from Matthew R. Francis, who earned a Ph.D. in physics and astronomy from Rutgers in 2005, held visiting and assistant professorships at several Northeastern universities and whose science writing has appeared in Ars Technica, The New Yorker, Nautilus, BBC Future and others including his own science blog at Galileo's Pendulum."
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Is Earth Weighed Down By Dark Matter?

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  • Readability (Score:5, Informative)

    by Anonymous Coward on Monday January 06, 2014 @09:19AM (#45877273)

    Making elaborate claims in oral presentations, without nailing down all the variables that could keep a set of results from being twisted into something more interesting than the truth is a red flag for any scientific presentation,

    It's standard not to write all the technicalities down in a scientific presentation. They usually last 30 to 45 minutes. There is no way, even for a scientific mind, to follow all the technicalities in 45 minutes when it took several months for the speaker to grasp the subject. Nobody in the audience would understand anything aside from the coauthors. Imagine your 20 hours advanced graduate course on physics condensed in 45 minutes with no simplification at all.

    Disclosure: I'm a mathematician, not a physicist.

    Let's wait for the proceeding or the full paper even though it's true we should be skeptical at this point.

  • Re: Impressive (Score:2, Informative)

    by Anonymous Coward on Monday January 06, 2014 @09:38AM (#45877361)

    There are two types of waves in water. Gravity Waves are the ones large enough to be held together by gravity, and capillary waves are held together by surface tension.

  • Re:Readability (Score:5, Informative)

    by professionalfurryele ( 877225 ) on Monday January 06, 2014 @09:47AM (#45877399)

    Not to mention that this is a completely bullshit attitude to take to oral presentations. I often present preliminary data at conferences, part of the point of these things is to get feedback from colleagues about things like what variables might explain the results seen and to search for collaborators who have the expertise to help you pin down your result precisely. Most talks I go to are "I collected this data to test X, I saw Y, X either can or cannot explain Y but Z definitely can, comments?".
    The exception is some engineering conferences where you are presenting finished work and it is a peer reviewed paper which other can cite, then you should know your shit.

  • by imjustmatthew ( 1164609 ) <(matthew) (at) (royhousehold.net)> on Monday January 06, 2014 @09:56AM (#45877445) Homepage

    No, this research wasn't even published, it's a conference talk and a PR release. Go read the actual link, at the bottom of the long post, where Matthew Francis dishes it out. Here it is again in case you missed it:

    http://galileospendulum.org/2014/01/02/no-dark-matter-is-not-messing-up-gps-measurements/ [galileospendulum.org]

  • re: (Score:5, Informative)

    by Anonymous Coward on Monday January 06, 2014 @09:57AM (#45877449)

    The later link from Dr Francis points out that the calculation has yet to be adjusted for the gravitational contributions of the Moon or Sun, and that it also doesn't make any relativistic corrections.

    Those omissions puts the dark matter claim on par with "hey guys I haven't looked at it from far away but from right here it looks the Earth is pretty flat, yeah?"

  • by Richard_at_work ( 517087 ) <richardprice@gm a i l . com> on Monday January 06, 2014 @10:05AM (#45877475)

    No GPS Satellites are geostationary, sure they all orbit in very predictable paths but they are not geostationary.

  • Re:How? (Score:4, Informative)

    by Anonymous Coward on Monday January 06, 2014 @10:12AM (#45877521)

    For geostationary satellites, drag is unlikely. The upper altitude limit for atmospheric drag is considered to be 2000km, geostationary are at 36 thousands km high.

    The earth mass is computed from the semi axis and the (sideral) period of any satellite (including the moon) orbiting earth: http://en.wikipedia.org/wiki/Standard_gravitational_parameter which gives you the standard gravitational parameter. To get the mass, you need to measure the gravitational constant which is harder but can be done with Cavendish experiment: http://en.wikipedia.org/wiki/Cavendish_experiment.

  • by sjbe ( 173966 ) on Monday January 06, 2014 @11:14AM (#45877885)

    GPS means Global Positioning System, and they're geostationary (or at least some of them are) and they're satellites

    No they are not [wikipedia.org] geostationary. They have orbits that make at least 6 satellites visible from nearly every point on earth at all times. Each satellite completes two orbits each sidereal day.

  • Bullshit Flag (Score:5, Informative)

    by jasnw ( 1913892 ) on Monday January 06, 2014 @12:16PM (#45878579)
    I work with GPS a lot, and there are many MANY people around the world who spend their entire lives making sure that there are very precise measurements of where those satellites are and how good predictions of where they'll be going are. These orbit calculations take into account the pressure of light from the sun on the satellites along with several other very small effects, so if there was some large extra mass in a ring around the earth it would have been noticed many years ago. I think this guy needs to recheck his calculations.

I've got a bad feeling about this.