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Mapping Gravity
overThruster writes: "No, you don't need to drink the water... Gravity is less strong in India--enough so that you weigh almost 1% less there. See BBC story about NASA's gravity map." Here's another story about the mission, and the GRACE home page (or NASA's less-informative page).
No, then it would be cheaper to ship things FROM there, since you get more than a ton per ton. And you could get on the plane with 70 lbs. of stuff, and when you arrive in (wherever) laugh uproariously at the ticket agent, dancing around and saying "ha HA! I have 71 pounds in my bag!"
"If he thinks he can hide and run from the United States and our allies, he's sorely mistaken." Bush on bin Laden
I was poking around in all of the sites for a few minutes before I found out that the satellites haven't been launched, and aren't scheduled to go up until Feb 2002. The BBC says it's going to be just a few weeks, but the official site says 97 days.
Interesting note from their site: A secondary experiment that GRACE will perform is to examine how the atmosphere affects signals from the Global Possioning Satellites (GPS). Ahhh, another Slashdot hotbutton! This project just keeps looking better and better the more you check it out.
What's your damage, Heather?
This was Astronomy Picture of the Day last week.
Plenty of depth/background available from there, as always!
"If you create user accounts, by default, they will have an account type of Administrator with no password." KB Q293834
Mapping the geoid is one of the most fundamental problems in oceanography. Ocean currents are all basically caused by water running downhill. The problem is that "downhill" in this case is relative to the geoid, which is a bumpy, not-nice surface. With this kind of map, we should be able to map surface currents from space; their velocity, their position, everything you want to know about how the surface currents are moving. This is important for climate studies of global warming, since the ocean currents are one of the main transporters of heat from the equator to the poles. This will allow us to get a much better idea of where the heat in the world is going, and how long it takes to get there, which in turn will give us a better handle on global warming.
Oceanographers have been trying to figure out a way to remove the geoid from their equations for a hundred years. Now we can just measure the damn thing. Crazy.
"The contents of this package are shipped by weight, not volume. Some settling may have occured."
:)
They're consistently defrauding India. Honeycomb's big (yeah yeah yeah) but it's not quite AS big in India? Sue sue sue!
Try Viagra.
"If he thinks he can hide and run from the United States and our allies, he's sorely mistaken." Bush on bin Laden
Hell, in my physics classroom it's about 30% as strong as anywhere else. I proved it myself in a lab last week- it's about 3.2 m/s^2 in our corner of the room!
Strangely enough, it's just about 9.8 up front. I guess the earth is pretty aspherical.
-Toad
--
- It ain't easy, being green.
So if things weigh less in India, wouldn't launching rockets and shuttles from there be easier? A 500,000-pound rocket would only weigh 495,000 in India - not a huge savings overall, but you could reduce fuel consumption and save money or go a bit further on the same amount of fuel. And the location is about as far south as Florida, so that's enough planetary curve for them. Should we expect to see more US companies building launch facilities in SE Asia after this report has been out a while?
== Paul Rickard, Editor of The Microsoft Boycott Campaign ====
...the fact that moving at speeds approaching the speed of light will cause you to move faster through time, so that if you left Earth, travelled at near light speeds, and then came back shortly afterwards, 100 years might have elapsed on Earth in what you perceived as about 10 minutes.
I think that physical laws like this have a very significant effect on the lumpiness of the Earth, and therefore, on the variations in gravitational pull.
Imagine that you're running down a square field, from one side to the side parallel to it, and it takes you 10 minutes to run across this field. Ok, now imagine that you're running across the same field, but instead of running "straight," you're running at an angle, so that you're not perpendicular to the edges of the field that you're running from and to. It will take you a bit longer to get to the other side of the field, even though you're running at the same speed, because by going at an angle, you've increased the distance you have to go to get from one edge to the other.
Now suppose we call the field a 2-dimensional surface, like a piece of paper. You could say that the first time you ran across the field, you travelled along one axis, or dimension--let's say the X axis. But on the way back, you ran at an angle, which means that you've gone along two axes, the X and Y axes. But you went the same speed. This means that you have split the same speed across two dimensions.
We say that time is a fourth dimension. Now picture this: No matter what's happening, you're ALWAYS moving through the 4 axes (the three "space" dimensions and the one "time" dimension) at exactly the speed of light. It's just that you're splitting that speed (the speed of light) across some combination of the 4 dimensions. You're doing one of the following:
I think all of these physical laws have a very significant effect on the lumpiness of the Earth, and therefore, on the variations in gravitational pull.
And, of course, the obligatory OH WELL.
Is that why those people stand on their heads over there? You see all of these Hindu guys doing handstands for days and the like... I knew there was I reason I can't do a handstand. Damn that unfair gravity!
Um, this is my sig.
Big deal, you say? Think of the existing physical infrastructure in a city. Now think of a new development that has to tie into the existing water, sewer, storm drainage and roadway systems. If you use GPS and don't take these things into account, you're going to take a chance on sewers that don't drain, storm drainage forming lakes and a general mess (not to mention lawsuits).
Not the typical
Bleh!
You probably hear the 9.8 m/s^2 acceleration due to gravity touted but this is just the net affect across the whole of the globe which is actually very inaccurate when used at specific locations.
Did you know that its actually easier to break the force of gravity ontop of mount everest. I'll show it using the formula:
g = G*(m/r^2)
= ((6.67*10^-11)*(5.98*10^24))/(6.389*10^6)
= 9.77 m/s^2
The value of g also can vary locally on the surface because of the presence of irregularities and rocks of different densities. Such variations in g also known as 'gravity anomilies'. Mineral deposits, for example, have a greater density than surrounding material; because of the greater mass in a given volume g can have a greater value on top of such a deposit then at its sides.
Overall altitude, underground minerals and distance from the equator all play apart in changing the acceleration due to gravity across the globe.
Is it possible that gravity can increase over the lifespan of a planet? I read recently
that 50,000 tons of space dust fall on the earth every day.
Maybe in the time of dinosaurs the earth actually had lighter gravity. Let's see-
50,000 tons of dust X 50 million years = 2,500,000,000,000 (that's 2 trillion tons of dust) that would be enough to effect gravity wouldn't it.
I'm sure my math is off, and that the earth must also lose a fair amount of matter via outgassing etc- But it would explain why such impossible beasts like the brontosaurus were
able to stand under their own weight.
I have no pants and I must scream
As I recall, the debate is between an asteroid/comet impact in the Yucatan vs a violent and prolonged period of volcanic activity in India causing the mass extinctions 65 MYears ago. Both would produce huge amounts of dust and ash and lay waste to whole continents. Problem is, geology can't quite pin down which one caused it. Hell, it could be both that pushed them over the edge, though the timing for that would be rather amazing.
Dyolf Knip
No, what you are referring to is something called the twin paradox, but it is not a paradox since the cases aren't exactly the same. Why? If you move at high speed away from earth and return, then at a certain point in time, energy had to be used to make you change your velocity and head back to earth. Either you used the brakes, turned and accelerated again, or a giant with a large bat gave you a smack, but whatever way you look at it: work is done to make the change happen. This is not the case with the earth. So the earth might appear to move away at near light speeds, but time will not pass slower on earth with respect to your frame :)
I intend to live forever, so far so good.
Back in 1978, Arthur C. Clarke ended his book The View from Serendip by writing about a gravitational anomaly which was found off the coast of Sri Lanka (formerly Ceylon) -- the small island near India where he lives.
I am able to visit my favorite spot (Chapter 13) for only a few days a year. But now, quite unexpectedly -- and literally since I wrote the preceding paragraph! -- Serendipity has struck again. While researching a totally different subject, I've discovered a good reason for spending more time on the south coast.
It concerns the greak Sanskrit epic, the Ramayana. In this 2,200-year-old poem, the demon-king Ravanna kidnaps Sita, wife of Rama, and takes her to his island stronghold of Ceylon. Needless to say, she is ultimately released, after aerial battles involving what look suspiciously like atomic weapons and laser beams.
To heal the wounded, the heroic monkey-general Hanuman is later sent back to India to fetch a medicinal herb found only in the Himalayas. Unfortunately, when he gets to the right mountain he is unable to identify the herb. No problem; he brings the whole mountain back! However, one piece drops off, on the southern tip of Ceylon. The locals believe this fragment is in fact my favourite bay, for its name in Sinhalese means "there it fell down" (onna watuna).
There it fell down. Place names usually have a meaning, though it is often lost in the mists of time. Did something really fall down, centuries or millennia ago, at Unawatuna Bay? A meteorite would be the obvious explanation; it must have been a big one for the legend to have lasted down the ages.
And here's another weird coincidence. Little Unawatuna, believe it or not, is the closest point on dry land to the world's greatest gravitational anomaly, a few hundred kilometres out in the Indian Ocean. On the Goddard Space Flight Center's 3-D map of the Earth's Gravimetric Geoid, that strange phenomenon looks liek a deep pit [1] into which the whole island of Sri Lanka is about to slide.
Let's put two and two together. A few thousand years ago, a huge object of peculiar density plunged into the Indian Ocean, creating a tradition that is remembered to this day. And it's still there, distorting the earth's gravitational field -- Terran Gravitational Anomaly I.
That might make an opening for a pretty good science-fiction movie . . . and an even better ending for this book.
Ayu Bowan.
1. One hundred and ten metres below zero reference on the Goddard model (March & Vincent, 1974).