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."
Re: Impressive (Score:0, Interesting)
Who had been around for millions of years to detect them?
How? (Score:2, Interesting)
How was the accepted mass of earth measured? It should at least be consistent with large-scale behavior of our solar system. Now satellites see a harder pull from earth. The same pull should be seen from the sun. It would make sense to me if satellites saw a lower pull than sun, implying that some mass is at earth, but further out than the satellites. This way, not so much.
Is it drag induced by the outer parts (not perfectly vacuum) of the atmosphere?
Weight Gain (Score:5, Interesting)
planets can't gain weight over the holidays like the rest of us
Actually they do. It's estimated that the Earth gains at least 164,000 kg per day from meteoric accretion. (Barker, J.L. and Anders, E. "Accretion rate of cosmic matter from iridium and osmium contents of deep-sea sediments." Geochimica et Cosmochimica Acta 32, 627-645 (1968))
Re:Hypothesis vs. conclusion (Score:4, Interesting)
What's wrong with presenting ideas to collegues who may be able to help you come up with ways to test that idea? That's what conferences are for. Papers in a peer reviewed journal are where you publish actual results.
Re:geostationary GPS satellites (Score:3, Interesting)
Yes, some of them are [wikipedia.org] geostationary.
You're referring to the WAAS and/or EGNOS payloads on geostationary satellites. While they transmit to GPS receivers using the same data format and signals (and in fact show up as GPS satellites so as to not break older GPS receivers) they are not actually GPS satellites. They do not broadcast the timing data used by the GPS system to actually position itself, instead they broadcast correction factors that the GPS receivers use to correct for atmospheric effects on the signal.
The atmosphere can have all sorts of subtle effects on the speed of light at RF, and while not a big deal for most things, GPS requires such precise timing that it is significant. Military receivers, which use both the L1 and L2 frequencies, can gauge the atmospheric effects from the differences between the two signals. Standard commercial receivers rely on WAAS earth stations to estimate the atmospheric effects, and then uplink them via the WAAS payloads in geosynchronous orbit.
Re:Impressive (Score:4, Interesting)
It's not direct detection of gravitational radiation, but observations of PSR B1913+16 [wikipedia.org] have been considered convincing enough proof of the existence of gravitational waves as predicted by general relativity. It's a binary pulsar: a neutron star and another object that might be another neutron star or possibly a black hole, orbiting each other. They're spiraling in together, which could only happen if their orbits were losing energy due to gravitational radiation, and calculations based on their observations conform exactly with the predictions of general relativity for gravity waves. This was convincing enough to have won the 1993 Nobel Prize in Physics for the scientists involved in the discovery and analysis of the pulsar, Russell Alan Hulse and Joseph Hooton Taylor Jr.