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."
Betteridge's law of headlines (Score:3, Insightful)
"Any headline which ends in a question mark can be answered by the word no."
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"Does this dark matter make Earth look fat?"
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Subject != headline.
There YOU go.
Readability (Score:5, Informative)
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.
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Let's wait for the proceeding or the full paper even though it's true we should be skeptical at this point.
This is Slashdot. That never happens.
Re:Readability (Score:5, Informative)
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.
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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?"
except ... (Score:3)
The Moon and Sun would act to counter earths gravity, making it appear lighter not heavier.
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They usually last 30 to 45 minutes
It has been many years since I have presented at an AGU meeting, but back then at least, you were given about 12 minutes. This just the kind of thing to present at one of these meetings. You have preliminary work and have a working hypothesis, and you put it out in a brief talk to your colleagues for comments and criticism. Some of these talks are summaries of work that has been, or will be sent in, as a formal refereed paper, a lot of it are graduate students presenting their work in progress, and some
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Of course, but just saying "What if it's dark matter?" without accounting for any of the many sources of errors I can think of off the top of my head (plus many more which I can't) is an indicator for grade-A bullshit.
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it's obviously an alien invasion (Score:2, Funny)
The excess mass is an invasion force of cloaked ships.
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Oil (Score:2)
I thought we'd been using tiny variations in gravity to detect Oil for 20 or so years now, fly over an area and map the underground caverns based off gravity variation.
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I thought we'd been using tiny variations in gravity to detect Oil for 20 or so years now, fly over an area and map the underground caverns based off gravity variation.
Yea, this whole thing sounds really sketchy. Like the guy made a miscalculation when helping design the satellites, only discovered after reports of accuracy issues with the system, and now he's floating a balloon about some wild theory so he doesn't have to admit to making a stupid, multi-billion dollar mistake.
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My point was more, "how come this thing that's been working for 20 years works, if you theory says it shouldn't". Not if it's actually any use in the field or not ;)
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...and he says to the farmer, I have found a solution to your problem: Imagine spherical cows [wikipedia.org] in a vacuum, uniformly radiating milk in all directions...
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Ehm, that's probably because gps does not work by measuring gravitational pull. Instead, differences in signal run time are considered
WTF (Score:2)
" one ringing the earth in a band 120 miles thick and 45,000 miles wide."
Presumably that would be outside the planet, and therefore would be counteracting the force of gravity towards the centre of the planet.
Or is there some other wierd geometry involved.
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If the ring was perpendicular to the orbit of the satellite, it would have an additive effect to the earth's gravity in proportion to how far out of the plane of the ring the satellite is. If the satellite is in the plane of the ring, it would have no effect, as it would pull equally in all directions.
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If you can accept that there may be more physical dimensions than our standard 3 + Time and that there could be a 4th physical dimension then it most certainly could be perpendicular to the orbit of the satellite.
https://groups.csail.mit.edu/mac/users/rfrankel/fourd/FourDArt.html [mit.edu]
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A ring doesn't make any sense at all given existing ideas about dark matter. Rings and disks form as a result of friction gradually eliminating all rotation except along a single, common axis. Friction is exactly the sort of thing that makes matter non-dark. Where would a ring come from?
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geostationary GPS satellites (Score:5, Insightful)
> geostationary GPS satellites
A what now?
Re:geostationary GPS satellites (Score:5, Insightful)
> geostationary GPS satellites
A what now?
Yeah, I had the same thought, if the summary cannot tell the difference between geostationary and lower earth orbits, what hope it there that it gets anything else right?
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GPS satellites are not in LEO, but not quite GEO either...
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so 'lower' is 'higher' than 'low'?
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They've probably had a devil of a time finding the Geopens to write on the Geostationary satellites.
Re:geostationary GPS satellites (Score:5, Informative)
No GPS Satellites are geostationary, sure they all orbit in very predictable paths but they are not geostationary.
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and they're geostationary (or at least some of them are)
Are you sure?
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Re:geostationary GPS satellites (Score:5, Informative)
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.
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They are in near exactly 12 sidereal hour inclined orbits (i.e., the period is 1/2 a sidereal, not solar, day). That makes them decidedly not geostationary (24 hour equatorial orbits) or geosynchronous (24 hour inclined orbits), but it does mean that their positions repeat every two orbits (more or less) compared to the "fixed" stars (not the Sun).
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Yes, some of them are [wikipedia.org] geostationary.
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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 s
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Probably misled by all those GPS graphics that show them just sitting up there, not moving.
If someone had added the "whoosh" lines behind these satellites on the graphics, we wouldn't have this kid of confusion.
Of course, then we'd have to correct people for saying; "the GPS satellites are constantly using propulsion" .. "NO!" you explain; "That's a whoosh line so people wouldn't think they were Geo-stationary and a lot of math had to be used to calculate position of satellite and triangulate with objects u
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Sorry. GPS satellites have 12 hour orbits, geostationary satellites have 24hr orbits. I.e., GPS satellites are not geostationary. If they were, they'd be all but useless in many (most?) locations on earth (where PDOP would be outrageously high). Imagine you were near the equator using a GPS comprised of geostationary satellites. You'd know your longitude very well but you wouldn't have any pseudorange data to let you determine latitude worth a damn.
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They are absolutely not geostationary. The whole reason your GPS needs time to 'lock' when you haven't used it in a while is it is downloading the orbital path(Ephemeris) data from the satellites themselves. Once it knows where they should be at which times exactly, it knows where it is relatively.
So basically, none of them are geostationary, unless you count ground based DGPS stations, that obviously don't move haha.
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he forgot a word.
Which word? "Not"?
massive and undetectable (Score:2)
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?
Re:How? (Score:4, Informative)
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.
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I think that accurately predicting the orbit of satellites requires more than just the mass of the earth as a point. I think that generally predicting the orbit requires less data (and maybe only requires a point mass estimate), but results in errors accumulating over time between where the satellite is predicted to be versus where it really is. Its my understanding that satellites intended for long-term use have mechanisms to correct for the error (i.e., discover the delta and alter the orbit).
Accuratel
It's... (Score:3)
You fools! (Score:5, Funny)
Your screams of terror will be like the song of angels to me.
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You laugh at the power of Lord Cthulhu, the Great and Glorious One. You try to come up with "scientific" theories and fancy math but the truth will become apparent to you very soon.
Your screams of terror will be like the song of angels to me.
How does this get rated +4 insightful? Funny maybe but insightful? I'm confused.
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the truth is always insightful?
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Funny? Your mockery will be met with the fury of The Great Cthulhu. Trying to stop Cthulhu would be like trying to stop the winds with your bare hands. Await your doom, meatbag.
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You laugh at the power of Lord Cthulhu, the Great and Glorious One. You try to come up with "scientific" theories and fancy math but the truth will become apparent to you very soon. Your screams of terror will be like the song of angels to me.
I'm not laughing. I, for one, welcome our new tentacle-faced overlords. Wait...that sounded weird.
Dark Matter = Entropic Pressure (Score:2)
More information complexity creates more entropic potential energy.
http://en.wikipedia.org/wiki/Entropic_force [wikipedia.org]
http://arxiv.org/abs/1207.4803 [arxiv.org]
http://arxiv.org/abs/1001.0785 [arxiv.org]
No, this isn't even published. (Score:5, Informative)
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]
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His calculations are nonrelativistic! Wouldn't that make the satellites seem to be going unphysically fast, implying his stronger-than-accepted value for the Earth's mass?
Hypothesis vs. conclusion (Score:3)
The dark matter ring is merely a hypothesis. In my field (or science, engineering, or mathematics generally) we should follow the scientific method when reporting results at a meeting.
This guy was unfortunately presenting a hypothesis. He should have waited and tried to find more compelling evidence before presenting. New Scientist should be familiar enough with the scientific method to avoid publicizing a radical and unproven hypothesis.
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:Hypothesis vs. conclusion (Score:5, Insightful)
It's not just a hypothesis. It's a hypothesis that fits some data, from GPS satellites and the Juno probe. It's solid enough to present as an idea to other scientists.
It's not solid enough to present as an idea to the general public, but unfortunately that's what popular science publications do for a living. They want "news"; their readers want to be the first ones to hear about exciting new developments. So they publish highly speculative material without the kinds of caveats, qualifications, and context that other scientists in the field bring automatically.
I have a love-hate relationship with them. They're helpful in drumming up public interest in science, playing up the romantic parts that help young proto-scientists engage with the field before the years of drudge work that go into actually becoming a scientist. And they help keep people feeling good about science and voting to fund it. But they mis-inform as much as they inform, and real scientists are continually having to provide the context that the magazines frequently refuse to.
(New Scientist is better than most daily newspapers, but worse than Science News. Frequency of publication seems to make a big difference: the longer your readership is willing to wait for accurate information, and the less they demand to have it ten seconds before the next guy, the more informative they are. Web-only sources are generally the worst.)
Inaccuracy in article on what 80% of universe is (Score:2)
Dark matter/energy = Fudge factor? (Score:2)
80% of the universe is made up of with Dark Matter and Dark Energy. The theories suggests the universe is made up of about 27% dark matter (not 80%) which is the subject of the article. Dark energy is a sort of negative gravity and is the force pushing galaxies apart faster and not relevant to this article's topic.
The whole notion of "dark matter/energy" seems a little desperate to me. We have evidence that our models of gravity cannot account for certain observations. That means one of two things. Either A) the model is correct and there is something out there that has mass that we cannot presently see OR B) the we can see all the matter out there meaning the model is wrong and needs revision. So far I've seen no compelling argument that A is more likely than B. I understand the hesitation to revise our model
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Dark matter = hypothetical (Score:2)
No one has ever come up with a theory of Modified Gravity that can explain the data we have , but Dark Matter does.
Never mind the tiny, little, minor detail that we have NO idea if dark matter actually exists or what it might be composed of it it does exist. It's not an unreasonable theory to investigate but I'm pretty reluctant to invoke some new exotic form of matter as a go-to explanation. Remember it was 400 years between Newton and Einstein. If the math model needs adjusting (and dark matter turns out to not be the answer) it might be a while before we figure it out.
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True , but we know that every test of relativity has strengthened it, not even once have we gathered data that contradicts it
So you are arguing that the theory of relativity only gives the right numbers if dark matter exists? Then if it turns out that dark matter does not exist you are proving the theory of relativity wrong. Relativity is a super well tested model and it might imply that dark matter exists but that is a HUGE leap away from proving the existence of dark matter. There are lots of things we haven't reconciled relativity with, quantum mechanics not the least of them. Just because relativity doesn't rule something o
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We have so many ideas what dark matter might be composed of that they span 5 Wikipedia articles.
And not one of them has experimental evidence to back it up. We simply don't know if dark matter actually exists nor do we know what it might be composed of. We're basically just guessing at this point. It's quite possible it doesn't exist at all and we simply have an incomplete model.
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Either A) the model is correct and there is something out there that has mass that we cannot presently see...
Like, I dunno, maybe dark matter?
Making the data fit the model (Score:2)
Like, I dunno, maybe dark matter?
Maybe but the point you ignored is maybe-not. With the evidence in hand, an incorrect model is a much cleaner explanation than some as yet undiscovered exotic form of matter than we aren't actually sure exists. I'm not saying dark matter doesn't exist, merely that I'm skeptical in light of the lack of evidence. It sounds like an effort to make the data fit the current model when there is a non-trivial chance the current model is wrong somehow.
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27 + 68 = 95. Our physical laws don't predict about 95% of the universe.
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))
Bullshit Flag (Score:5, Informative)
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I agree, this is likely a mistake. Most grand new discoveries fizzle when peers start falsifying (as in 'to test and prove false') them.
Having said that, a matter type can be imagined whose 'drag' on GPS sats would be so rare and trivial as to be mistaken for part of the drag that near-atmospheric objects feel. Neutrinos fit this example. All we need here are massive nonreactive slow cloudy fat (but I repeat myself) particles that do gravitationally interact but don't bump into each other, don't coalesce,
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Well, the earth is certainly weighed down by a plethora of bullshit artists out there.
The guy making the "observation" is himself the dark matter which weighs us down... :P
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Radiation Pressure [wikipedia.org] is momentum transfer purely with EM radiation, not the plasma ions from the solar wind. It is a very noticeable effect and must be accounted for anything in orbit more than a few hours.
The GRACE [wikipedia.org] experiment utilizes satellites in polar LEO (310km above the Earth's surface) to created detailed maps of the distribution of matter below it. Depending on the configuration of the dark matter, it may not be visible to GRACE. If the dark matter was a spherical shell around the earth, we woul
This would fail peer review (Score:2)
From New Scientist :
That, alone, would make this fail peer review, not to mention that the GPS satellites (which are big and messy and do stationkeeping and get replaced) are not the satellites to use to do this with (the Lageos satellites fit both requirements, being both well monitored and with very low non-gravitational perturbations). The Lageos orbit at a lower
not fair (Score:2)
Wait what? (Score:2)
Isn't the whole point of DM that we can't detect it except by the gravity distortion? Its basically "unfound matter"...
And what means is what we really have is a distortion of gravity in a given area that we cannot count for... its therefore not dark matter but dark gravity.
Or am I wrong? have we actually found dark matter? The actual stuff. Proven to exist? Or is it just what we write down when our math doesn't add up?
If the headline is a question... (Score:2)
If the headline is a question the en answer is almost certainly "No", and the reporter unqualified for the topic.
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.
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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.
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Who had been around for millions of years to detect them?
Your question implies you also have a theory about trees silently falling in the woods, right? It is not all about you, sometimes it is about them .
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Both your post and his are quite funny. And stupid.
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I'm surprised no one has pointed out yet that this was exactly the behavior predicted by the Flying Spaghetti Monster pressing down on objects to keep them from floating into space.
Re:It's God (Score:5, Funny)
I don't trust this whole "theory of gravity." Obviously, this "theory" is just an unknowable guess and therefore doesn't have the full consensus of "science". I say we need to teach the controversy that the reason we stay on the earth is because some supreme being wants us there. Birds and planes only work because when their wings are outstretched they make a holy cross.
Teach the controversy. Don't believe "theories".
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I say we need to teach the controversy that the reason we stay on the earth is because some supreme being wants us there. Birds and planes only work because when their wings are outstretched they make a holy cross.
OK, then, explain balloons and the Flying Wing aircraft! Clearly your cross-based supreme being is a fraud, and the FSM is the One True Being (not to be confused with the molpy-laden One True Thread, but I digress even deeper into metasarcasm).
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C'mon, don't reinvent the wheel here. The theory of Intelligent Falling [wikipedia.org] is the go-to parody, and is well-known enough to have a Wikipedia page. You might also find last-Thursdayism amusing.
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Do NOT burn the goats - they're much better medium rare.
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Dark matter's really unambiguous in the experimental data. You need a lot of theoretical solipsism such as weird new forms of gravity to write it back out of the physics.
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Dark matter is nothing but unexplained data. There is unambiguous experimental data that indicates there is something we don't understand about the universe, but not what that something is. "Dark matter" is the current popular hypothesis, but nothing more than that.
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We would of had to know the precise mass and gravitational pull for any of the rockets or satellites we sent into space to work. Given that they have not all fallen back to earth, if their is any invisible matter out there, it is obviously in insignificant infinitesimally small amounts.
Well, the linked refutation points out the problems with the argument, but the guy is arguing that the amount of dark matter is fairly small. It wouldn't mess with the ability to launch a rocket. Sure, you might end up in a slightly different orbit than intended, but you'd end up in orbit. Almost all launches involve minor corrections anyway - it isn't like you can just calculate nothing but a burn time when the rocket to LEO spends its entire time inside the earth's atmosphere, and the target orbit is i
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Usually because they contain fuel and thrusters designed to last the lifetime of the satellite in order to make regular course correction because those, especially in LEO, are actually falling back into the atmosphere. Although part of that may be on purpose incase the sat fails it will eventually fall back into the atmosphere and burn up. But I've heard before the other reason was the tendency for them to want to fall back to earth despite calculations saying otherwise...
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Would've. It's a contraction of "would have".
And, no, we don't need to know the precise mass of Earth for satellites to work. Admittedly, we'd need to be pretty damn close for things to actually be in their design orbits.
However, this guy is making noise because he's seeing long-term effects on his satellites that he (supposedly) can't account for by more conventional means. Personally, I think it would have been noticed before now, if such effects exist, but you never can tell.
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I read this several years ago.
And have you read anything about it since?
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Earth loses 100kg, the mini blackhole gains 100kg, but from the outside the combined mass of both the earth and the mini blackhole would be constant.
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Obviously it'd be dumping the mass of the earth out the other end of the black hole.
If television has taught me anything, it's that black holes are portals to other places - mostly bad places, but other places nonetheless.
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