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Scientists Measure Gravity Change From Earthquake
Science Daily is reporting that scientists were able to use satellite data to watch changes in the Earth's surface caused by a massive earthquake. These changes had two major measurable effects on the region. The massive uplift in the seafloor changed GPS measurements, and the density of the rock beneath the seafloor changed which produced a detectable change in gravity.
I thought I felt lighter this morning...
How much did it weigh?
I have a lot to keep track of, what with my checkbook, blogs, email, vehicle oil changes and tire rotation, bills, and keeping various client networks running.
So I'd appreciate it if someone could keep track of this whole gravity situation, and just give me a summary. Let me know if we're all about to go floating off into LEO, but otherwise, keep the announcements to a minimum.
Raise your children as if you were teaching them to raise your grandchildren, because you are.
Me too. And there was this strange seasick sensation while it happened...must have been gravity waves.
Brought to you by the Department of Redundancy Department...
Detecting "major" quakes - those measuring a magnitude of 7 to 8.9 - which occur frequently is being investigated. NASA's planned extension of the current mission, dubbed GRACE 2, and its enhanced instrumentation should aid in that effort.
However, Han is hopeful that NASA's planned expansion of the current mission, dubbed GRACE 2, and its enhanced instrumentation, might allow the detection of "major" quakes - those measuring a magnitude 7 to 8.9 - which occur frequently.
If we don't take this threat seriously, we will all be smashed flat, like pancakes, and grilled by global warming.
Unconfirmed reports indicate that giant bird-like aliens will arrive shortly, and revel in the pancake carnage, gorging on the waste like so many crows on road kill. The same sources said they do not wish to imply that the aliens are in league with the Bush administration.
Really bland article I mean I can change the gravitation fields on my desk my moving my glass of water around and I do believe that is measurable. (Maybe not by a satellite.) So anyone out there have an idea of the magnitude of the change. Will athletes gain a boost there by training in a higher gravity environment? What are the effects of the lower gravity environment or is it so insignificant that who cares.
Or more interesting dose anyone have a map of the earth and differences in gravity in different areas? (I smell a new google map)
Just my 2 cents
Let's hope this is the final nail in the coffin for the theory of 'intelligent falling' proposed as an alternative to gravity.
What we really want to know is can this data be fitted to measurements immediately before the quake. Since earthquakes are essentially relaxation oscillations in plate movement very careful extrapolation with some fancy signal processing techniques (linear prediction maybe) might be able to spot some features in the gravity field out in space.
I think there's no magic bullet for quake prediction, but the solution is a very holistic thing by aggregating lots and lots of different measurements. For example the gravometric measurements may say "there's about to be a quake somewhere on Earth, but we can't say where for sure" while more local measurements might help pin down the likely shift location.
With everything moving all over and us trying to define property lines (including international borders) reliably, we sure do have a mess.
If GPS is tied to some NAVY building in Maryland and the building moves, do we then declare that the building DID NOT MOVE because it is by definition in a particular place? Everybody else moved?
(I do not in fact know: it could be an Air Force cave in the Rocky Mountains, etc.)
If half of the Earth moves relative to the other half, which set of property owners has a problem?
Is it in one spot . . .
Yes.
Put a cement block on the floor in front of you. Now stand on it.
Ta da! Instant local gravity increase, because there is now more mass underneath you.
KFG
Does anyone know if there are scientific instruments that are sensitive enough that they would have to be recalibrated for this change in gravitational field strength?
Reading code is like reading the dictionary - you have to read half of it before you can go back and understand it.
But now you're furthur from the earth's core, so it must cancel out :)
But now you're furthur from the earth's core, so it must cancel out :)
Whether that is true or not is left as an exercise for the student.
KFG
Britain devalues the pound.
This is heavy, and weight has something to do with it.
Sorry to burst your bubble, but I think you mean a local gravity decrease. Why use one cement block when you could use a million? Take it to the limit! When you step on the cement block(s), you're moved farther away from the center of the earth. The effects of gravity decrease with the square of the distances involved. And I think you can agree that the mass of a million cement blocks will not change the center of mass of the Earth enough to compensate.
Sorry to burst your bubble, but I think you mean a local gravity decrease.
.
I can't help it if you didn't notice the cement block shaped hole in the floor into which the cement block was supposed to be inserted.
I think you can agree . .
Not until you show your work, no, I cannot.
KFG
If it moves "a little", the people with a problem with be the ones that are poorer - as usual. By definiton the more well-to-do have the means to fix stuff (or higher a better lawyer to get the "new" property lines drawn in their favor :-)
On the other hand, if it moves "a bit", (like "end of the world as we know it") then maybe you would have been better off as a hunter gatherer, already in tune with the primative conditions that arise.
Of course, if it is "really a lot" (end of the world.) Then the point is moot.
This issue is a bit more complicated than you think.
I'm willing to bet the people at LIGO noticed it...
Yeah. Would you choose a neurosurgeon who pokes around people's brains in his spare time? I wouldn't.
I don't think so but particle accelerators have to be properly set up after earthquakes, and LEP at CERN was sensible to moon phases (literally, also the earth itself is bent during tides).
This reminds me a little of a physics practical I did this year. It was supposed to be the first practical where we would get a decent accuracy, measuring g using a pendulum to about 6 significant figures.
We were also told at the end of the practical about far more accuarte ways of measuring g, and that a university in Germany several decades ago had used this regularly as experimental training for graduate students. However, when the experiment was performed at different times of the year, a small but definte increase in g was noticed during the winter. More accurate measurements showed a sudden spike near the start of winter, followed by a slow decrease until the summer.
Professors were baffled, until someone remembered that the lab in which the experiments were carried out was above a coal cellar used to store a huge quantity of coal for burning during the winter.
So what happens when I fart? I personally have significantly less mess, but there's also significantly more mass around me (think of the change in size of a blowfish).
I've stood on a bathroom scale trying to measure this but my instruments are either too insensitive or are too greatly affected by the tremendous resultant atmospheric change. Any ideas?
So what happens when I fart? . . .I've stood on a bathroom scale trying to measure this but my instruments are either too insensitive or are too greatly affected by the tremendous resultant atmospheric change. Any ideas?
Use a satellite.
Contemplate other phenomenon that might affect the outcome of the experiment (hint: think of a balloon) and propose a means of compensating for their effect.
If the satellite turns out to be insufficiently precise ponder the limits of measurment and the concept of significance.
For extra credit ponder the relevence of your conlusions to measurements of, ummmmm, "gross" atmospheric changes and relate this to public policy.
This will account for 50% of your final grade.
KFG
That's why real men only work in ellipsoidal heights!
I dub thee... Sir Phobos, Knight of Mars, Beater of Ass.
He weighs more because all mass underneath him to the surface of the earth on the opposite side is pulling him down.
-Ed
So you see what had happened was....
Ahh....so finally, there will be a place where people will fall in love harder !
Primordial Soup
As long as it doesn't take California away so I can keep watching The O.C. it could blow whole north america away.
If I had them, well, I might give that one - it is almost funny, in a Jon Stewart kind of way.
This issue is a bit more complicated than you think.
Depends what the floor is made of - most basements have a concrete floor anyway so there would be no change.
So let's refine the experiment a bit.
How about we put our g meter on top of a stool, take a reading, and then shove a concrete block under the stool?
KFG
I can see the "Intelligent Falling"ists are out in full play today.
Please, for the good of Humanity, vote Obama.
When you step on the cement block(s), you're moved farther away from the center of the earth. ...and closer to the center of the cement block. Distance is going to be a bigger factor in terms of the cement block's gravity vs. the Earth's; realtive to your mass & size, Earth is so many billions of orders of magnitude bigger than you; whereas ten or fifteen cement blocks might equal your mass and exceed your density (and Earth's, at the surface anyway).
A terrestrial mass only a couple of kilometers in diameter owns enough gravity to hold itself together, IIRC from astronomy. If you were to climb a 5km mountain in Colorado, you'd be in a bigger gravity field than if you were below sea level in Holland or something.
Really, standing on a cement block probably wouldn't produce a measureable increase in gravity for decades to come (until we have the ability to measure it that precisely). But I'm certain standing on something that's on top of Earth's surface does increase the gravity you're subject to, if it has a greater density than you and a greater or equal density as Earth.
The really intersting question to ponder is, how significant is a human's own gravitational field? If you jump up and down, does the earth measurably oscillate accordingly? What if everyone in Japan jumped up and down synchronously? Given how many people per sq. km. there are?
Given enough sensitivity in the instruments you probably could detect gravity changes when I fart.
Satellite paths are measured at:
Hawaii, Kwajalein, Ascension Island, Diego Garcia, Colorado Springs
Perhaps your GPS unit thus gives you a position relative to the average of those sites. That would be two spots in the Pacific Ocean, one in the Indian Ocean, one in the South Atlantic Ocean, and one in the Rocky Mountains. If things disagree, I'll bet Colorodo Springs wins the argument.
If you're in Asia or Europe and your land moves... oh well!
Gravity + Macroscope + Nuke the Moon = Profit.
nt!
Really?
What I mean is this: does the extra attractive force between you and the cement block more than compensate for the extra distance you've put between yourself and the earth's center of mass (which would tend to decrease the gravitational force you feel from earth)?
"Provided by the management for your protection."
Really?
Wellllllll, not with a typical cement block, no.
does the extra attractive force between you and the cement block more than compensate for the extra distance you've put between yourself and the earth's center of mass
Gravity falls off by the inverse of the square of the distance. If your cement block is equal in mass to the average of the column of Earth underneath you the mass is only going up linearly with distance and the total force will go down. If it's equal to the square of the average mass you'll break even.
KFG
He weighs more because all mass underneath him to the surface of the earth on the opposite side is pulling him down.
But you are father away from the mass on the opposite side, reducing its contribution to the total force.
Turns out that if you average all the forces it works out to the same as if all the mass were concentrated at the Earth's center.
If you dig a hole and jump in gravity will be decreased, even though you're closer to the center, because the average force exerted on you by the entire shell of the Earth above your own center of mass averages to zero. You can intuit this easier if you imagine yourself at the center of the Earth, where you would be weightless.
KFG
This is true, but there is a slight increase in the downward direction in gravity even though it is very miniscule.
-Ed
So you see what had happened was....
Ahhhhh, but the increase in gravity due to mass is linear. Double the mass, double the force.
But the force of gravity also follows the inverse square law, get twice as far away and you quarter the force of gravity.
So if your added mass necessarily pushes you farther away from the center the force will fall off due to distance faster than it increases due to mass, lowering the net force, unless your cement block is very massive. Say about 1000 Kg.
KFG