The least important things sometimes, my dear boy, lead to the greatest discoveries.
The Doctor (William Hartnell) Serial: The Space Museum Episode: The Dimensions of Time (1965).

Gravity (Wikipedia):

Every planetary body (including the Earth) is surrounded by its own gravitational field, which exerts an attractive force on all objects. Assuming a spherically symmetrical planet, the strength of this field at any given point is proportional to the planetary body's mass and inversely proportional to the square of the distance from the center of the body.
The strength of the gravitational field is numerically equal to the acceleration of objects under its influence, and its value at the Earth's surface, denoted g, is expressed below as the standard average. According to the International Bureau of Weights and Measures, under the International System of Units (SI), the Earth's standard acceleration due to gravity is:
g = 9.80665 m/s2 (32.1740 ft/s2).
I'm beginning to have my doubts.

I know that explanation is simplistic but gravity is expected to be fairly constant on the surface of the Earth.

This week I checked out the Cosmos Mystery Area near Mount Rushmore and was astonished by one thing in particular. The pendulum.

I pushed the pendulum myself and the force required to push it to a 45o angle towards the wall from it's natural point was less than the force required to push it to a 30o angle away from the wall. The first 15o was fairly easy but the force required increased dramatically after that point.

I hate to speculate but I will. The cabin is on a hillside and there are cliffs to one side and gullies towards the other. The mountains on one side are denser than the air on the other and with much greater mass on one side it there is a greater attraction in that direction.

The pendulum naturally sets 10 to 15o off true zero. Once the pendulum is pushed passed true zero the gravitational attraction of the Earth adds to the force pulling from the mountains and makes the pendulum much harder to push.

While many of the demonstration presented in the tour may be attributed to optical illusion from the off level floors and walls or a false reference frames caused by the mountain range, I pushed the pendulum myself and the variation in force required to push it was remarkable.

I believe this and other similar areas deserve more attention than the blanket dismissals I have seen on many websites discussing the phenomena.

Update:

h/t to

h/t to LaFeminista from the Comments.

Recent analysis shows a much higher surface gravity variation.

Via Science Daily. Data from The Western Australian Centre for Geodesy.

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#### Comment Preferences

• ##### I'm not responsible...(9+ / 0-)

.. for the explanations presented in the video.

• ##### gravitational variation(9+ / 0-)

"I decided it is better to scream. Silence is the real crime against humanity." Nadezhda Mandelstam

• ##### There may be something to that.(1+ / 0-)
Recommended by:
thanatokephaloides

• ##### Let me try again(1+ / 0-)
Recommended by:
thanatokephaloides

• ##### no scale(4+ / 0-)

A lovely picture with no indication of just how tiny the variations really are in spite of the dramatic colors.

The plumb bob is accurate.

• ##### Good thing the builders had a True Zero handy(6+ / 0-)

so they didn't get confused by a plum bob that was off by 10-15°.

... The Meritocrats!

• ##### The didn't use a plumb bob.(1+ / 0-)
Recommended by:
thanatokephaloides

Or a level. The cabins are off level by a lot whether true or apparent.

• ##### Or perhaps this is the problem,(15+ / 0-)

A fo ben, bid bont. - Welsh proverb. ( translation: If you want to be a leader, be a bridge.)

• ##### That would certainly be a problem(5+ / 0-)

Especially for the kitteh drones, (humans) walking underneath when the gravity came back on. Yikes!

"Given the choice between a Republican and someone who acts like a Republican, people will vote for a real Republican every time." Harry Truman

[ Parent ]

• ##### Um(13+ / 0-)

The gravity map provided above would appear to depict the difference between the actual vertical component of the gravitational field and the standard reference geoid, expressed as equivalent altitude. Hence, the observed variation over the area -- about 13 meters -- is totally negligible, just as you cannot really tell the difference between the strength of the gravity field between first and fourth floors of a building.

Furthermore, the local strength of the vertical component is irrelevant to the kind of pendulum experiment that is described; for that you should be interested in deviations in the horizontal field. A quick googling will let you know that the maximal horizontal deviation observed in the GGMplus dataset that covers the entire Earth is about 100 arc seconds, which is less than 0,03 degrees. Again, for all practical purposes, that is a totally negligible value.

Our current understanding of the phenomenon of gravity lies on a very solid foundation; anything that seeks to refute that foundation is a most extraordinary claim, and thus requires most extraordinary evidence to be taken into consideration.

• ##### So are you saying that a guy(4+ / 0-)

in a cabin who has the personal experience of having to push a pendulum harder in one direction than the other is NOT extraordinary evidence? Is it safe to move on from this diary with the presumption that General Relativity has survived this assault, or are all bets off?

• ##### Not sure whether Devil's Advocate(7+ / 0-)

...or not, but the answer is no, this diary does not provide extraordinary evidence worth serious consideration. Specifically, no effort is used in trying to invalidate most obvious (and more simple) alternative explanations for the perceived anomaly; hence, the proposition falls to Occam's razor.

Please let me relate a short story that is somewhat relevant.

A while ago, a neutrino experiment in Europe suggested that the neutrinos sent from one laboratory to another were traveling at a superluminal speed. That caused quite a lot of commotion since the result persisted over several evaluations of the experiment.

When the situation was still unclear I had to deal with a particle physics amateur (no, really, there are people like that) in my job (forwarded to me by my supervisor so I couldn't refuse). The guy postulated a fundamental particle that would explain the observed anomaly (and all the other mysteries of modern physics as well) and demonstrated his theory with pages after pages of Feynmann diagrams. I proceeded to falsify his hypothesis by politely pointing out where it was in conflict with known facts of the world. In response, instead of adjusting his hypothesis he refuted the validity of the facts that I gave, in a progressively worse manner until he was questioning the kind of stuff that hasn't been controversial since the invention of rocks and pointed sticks.

At that point I explained that between two alternative hypotheses, that someone had made a simple but non-obvious error when interpreting the neutrino experiment, and that everything we know about the world is fundamentally wrong, Occam's razor demands that the first hypothesis must be chosen. I thanked the guy for his effort and closed the case.

A week after that the real culprit for the botched neutrino experiment was found -- a miscalibrated connector cable.

• ##### If only Feynmann himself were around(2+ / 0-)
Recommended by:
Tomtech, kurt

for this neutrino controversy. I thought he was an odd choice for the Challenger panel, given that this was an engineering problem and not one having anything to do with particle physics or QM. But as the panel labored away, he solved the (O-ring) riddle almost single-handedly. He invented Feynmann diagrams, a simple alternative to field theory that actually produces answers to problems using a pencil and paper. He came up with a totally different way of doing quantum mechanics using path integrals (though I don't think they are used all that much). The guy was one in a billion. He was a great educator, brilliant scientist, and the life of every party with his bongos and stories.

• ##### The video is telling if you analyze it(0+ / 0-)

At the end of the video and at the 49 sec mark the pendulum is still. It is at the same angle as the demonstrator which indicates that there isn't a magnetic field affecting it.

Between the 24 and 35 sec point the pendulum is swinging freely.

It takes 1.45 seconds to swing toward the wall and back to it's natural point. That occurs three times. Twice it swings away from the wall and back to the natural point. Those two swings take 1.15 seconds each.

That behavior does not comport to the swinging of a pendulum in most areas on the surface of the Earth.

My personal observation can be ignored but you can analyze the swing of the pendulum yourself with freely available video tools. I used Real Downloader and Windows Movie Maker.

Considering the location of this area near Mount Rushmore, which gets 3 million visitors a year, and it's popularity there are likely to be more than 1000 people who personally perform this experiment I performed annually.

I would bet you believe reported conclusions from experiments which cannot be repeated at a separate facility and cannot be personally observed or felt by any human (ie: Higgs Boson Discovery)

• ##### The video doesn't tell anything pertinent(3+ / 0-)
Recommended by:
atana, Tomtech, kurt

I watched the video and agree that the behavior of the pendulum appears somewhat irregular. However, I can think of a number of completely natural mechanisms that can be used to create the effect seen on the video. What I can't see is effort to exclude any of those natural explanations through relevant experiments. Furthermore, I'm also aware of direct consequences that we should be seeing if the irregularity had anything to do with a gravity differential, but nothing of the kind can be seen, either. That a large number of visitors has already performed the experiment is evidence in favor of it being just a party trick. Thus, Occam's razor.

And yes, I have no particular reason to doubt the recent discovery of the Standard Model Higgs, because the proper procedure was rigorously applied. Science is a bit like ice hockey -- goals only count if you play by the rules. :)

• ##### This is an illusion(8+ / 0-)

Like a car rolling "uphill", this is just a matter of perspective. Our visual clues lie to us from time to time and that fools us into thinking that we're seeing or experiencing something that we're not. In the case of the car, that road is actually going downhill but because it is on a slope that is much larger than what appears to be a "hill" from the perspective of the camera, we can't see the total picture. You experienced a similar phenomenon in that the environment has been constructed deliberately to fool your senses into believing something is level and neutral when it isn't. Your physics teacher didn't lie to you, your own perceptions did.

"Given the choice between a Republican and someone who acts like a Republican, people will vote for a real Republican every time." Harry Truman

• ##### We went to Cosmos and it is fun.(8+ / 0-)

Unfortunately, it does seem to use more than a little trickery in perspective.

However, I would recommend it to to visitors of the Black Hills, just because. If you google Black Hills and Cosmos, you will find multiple references to similar "tourist" spots around.

http://www.sandlotscience.com/...

Knowing the "science" and the fact that it is an "illusion" doesn't detract from the fun of the place.

Disclosure : I've visited twice and enjoyed it both times even knowing that it was an illusion. It is well done.

Character is what you are in the dark. Emilio Lizardo in Buckaroo Bonzai

• ##### What I want to know about gravity,(2+ / 0-)
Recommended by:
Wee Mama, Tomtech

or at least one of the things, does it go away as you approach the center of the earth? Logically, it must, since the mass is all around you, pulling you from all directions. So maximum gravity exists at the surface of the body and rolls off either direction you go, in or out, right? Gravity is toroidal?

If I ran this circus, things would be DIFFERENT!

• ##### Actually gravity increases(1+ / 0-)
Recommended by:
Tomtech

Actually gravity increases as you approach the center of a mass, until you reach the very middle. At that point, all directions are up.

"Given the choice between a Republican and someone who acts like a Republican, people will vote for a real Republican every time." Harry Truman

[ Parent ]

• ##### Gravity increases as you approach(4+ / 0-)
Recommended by:
CwV, happymisanthropy, Tomtech, atana

a mass from outside the mass. But once you penetrate the mass and start to tunnel through it, the only net gravity you feel is based on the mass of the sphere between you and the center, so it is decreasing.

• ##### No, gravity decreases(4+ / 0-)
Recommended by:
CwV, happymisanthropy, Tomtech, atana

Pressure increases but gravity decreases as you approach the center of the Earth. Specifically, assuming a spherical and horizontally homogeneous Earth, the portion that is above your current altitude does not contribute to the local gravitational field at all -- just as CwV says, the integrated gravitational force of an empty shell is exactly zero everywhere inside the shell. Thus, at the center of the Earth no gravity can be observed because there is an equal amount of pull in all directions.

• ##### Right. By Gauss' law the gravitational field insid(0+ / 0-)

a homogeneous mass shell is zero. For a spherical isotropic mass the gravitational force at distance r from the center is the same as if all the mass of the sphere out to radius r were concentrated at the center, while the mass from the shell farther out than r contributes nothing. Hence the gravitational force decreases as you approach the center.

American Presidents: 43 men, 0 women. Ready for Hillary

[ Parent ]

• ##### Well,(3+ / 0-)
Recommended by:
CwV, Tomtech, atana

The pull from the bit of mass right at the center of the earth does become stronger as you approach it, but the pull from the rest of the earth decreases.  For the reason CwV notes, there is no net gravitational pull inside a hollow sphere.  As you approach the center of the earth, more and more of the earth is like a hollow sphere that you're inside, so the total net pull on you decreases as you go deeper into the earth.

"If they give you lined paper, write the other way." (Juan Ramon Jimenez)

[ Parent ]

• ##### Gauss law. Learn it. Apply it.(3+ / 0-)
Recommended by:
Tomtech, CwV, atana

Here is the derivation for a solid charged sphere.
Since both gravitation and electrostatic fields are inverse square proportional, this analysis is valid for gravity as well.

Inside the sphere the field increases linearly with the distance from the center.

Outside the sphere the field is that of a point-charge positioned at the center and it drops off accordingly.

Queror Ergo Sum. -- Rene Descartes Shakshuka

[ Parent ]

• ##### If there was a shaft through the center ...(2+ / 0-)
Recommended by:
CwV, Tomtech

If there was a shaft through the center of the earth to the other side (a rather monumental accomplishment!) and you dropped something (or someone) down the shaft - the net gravitational force would be the usual 'g' as you enter and then would decrease to 0 at the center (linear drop off w.r.t to distance from center).

Now if you weren't in a shaft but just located at some point in the interior of the earth there would be other important forces to consider!

• ##### Yeah, like heat and pressure, just a bit.(1+ / 0-)
Recommended by:
Tomtech

Rei is doing a series of posts on the magma flow underground in Iceland (a great series that everyone should read) and even just a few Km underground, the forces are incredible!

If I ran this circus, things would be DIFFERENT!

[ Parent ]

• ##### These illusion houses....(8+ / 0-)

were all the rage in the 50's and 60's. They are making a comeback for the newer generations to enjoy, too.  They are always built near some "magical" hill or big rock outcrop. They are fun, but entirely a tourist scam (but as mentioned certainly an enjoyable one). I remember this exact pendulum trick at one we visited near Gatlinburg in the early 60's when that used to be a popular tourist area. Balls roll uphill, water flows the wrong way, when you walk across the floor (actually walking at quite an angle downhill) there seems to be an unnatural force drawing you toward the wall (we scientists call that "gravity".)

Newton can still rest easy in his grave. All is still well...(but he better keep an eye on those quantum cosmologist fellows - they are definitely out to get him!!!)

• ##### What if Newton rolls out of his grave - uphill!(4+ / 0-)

Course we'd have to move his grave to a "Magic Spot" (TM) with special magiky properties...

I went to one of these in Wisconsin Dells (Tourist. Trap!) as a kid and it was fun - the visual / scale tricks, the uphill ball roll, etc.

Knowing science now doesn't detract from the thrill of the weird back then.

"If you're in a coalition and you're comfortable, you know it's not a broad enough coalition /= GTFO" Dr. Bernice Johnson Reagon + JVolvo

[ Parent ]

• ##### Yes. The "Whacky Shack" in Houston(6+ / 0-)

Was at least partially responsible for interesting me in science. I figured the floor thing out right away. The water took me a little longer. ;)

"Given the choice between a Republican and someone who acts like a Republican, people will vote for a real Republican every time." Harry Truman

[ Parent ]

• ##### You're not accounting for all the forces(4+ / 0-)
Recommended by:
thanatokephaloides, Tomtech, RickD, atana

For all intents and purposes, there is a constant acceleration field g normal to Earth's surface.  At equilibrium, the tension on the line between the the weight and the pivot is equal and opposite to gravitational pull.  As you push the weight away from equilibrium, the line applies a restoring force tending towards central equilibrium.  This force increases with the angle, and that's why it's harder to push a weight to 45 degrees rather than 30.

• ##### Then why is the force different when pushed away?(0+ / 0-)

See my long comment above and perform the observation yourself.

• ##### Because you're taking on more of the component(2+ / 0-)
Recommended by:
atana, Tomtech

normal to the surface of the Earth with your own arms.

The restoring force isn't constant over the range of swing.  It increases the farther away it gets away from equilibrium.  That's what you're feeling.

• ##### Did you do it?(0+ / 0-)

I pushed the pendulum 45 degrees one way and then the other. Away from the wall developed much more resistance even at the same angle.

• ##### The Laws of Physics(2+ / 0-)
Recommended by:
thanatokephaloides, Tomtech

In one of his first lectures in freshman Physics, in a classroom located on the sixth floor of the building, my professor said, "The laws are physics cannot be broken, unlike laws created by people.  For instance, consider the law of gravity.  It is irrefutable.  If you wish to disagree with me, I invite you to step out the window."

I do not demand tolerance, I demand equal rights. --Anna Grodzka

• ##### Most HS physics teachers lie(2+ / 0-)
Recommended by:
Tomtech, atana

But it is usually because the students lack the mathematical   skills needed to understand it.

For example, most HS students graduate with the knowledge that the Rutherford model of the atom (electrons orbiting the nucleus) is true. They imagine the electrons as little beads zooming around under the electrostatic influence of the protons and held in orbit by the centrifugal force.

So if you want to throw a curveball to your Physics teacher ask her this:

We know that the electrons move in circular orbits. since their orbits are circular they must accelerate (Newton's first and second law).
Electrons are also charges.
An Accelerating charge radiates electromagnetic waves (Larmor's formula)- that is, the electron loses energy via radiation.
In order to compensate for this loss, the electron must fall further into the potential well of the nucleus, but then it will just circle until it completely collapses into the nucleus.
We know this doesn't happen - why?

Another lie - planes fly due the Bernoulli principle.
And a semi-lie - The sun does not revolve around the earth.

Queror Ergo Sum. -- Rene Descartes Shakshuka

• ##### My post secondary education was specific.(0+ / 0-)

The physics courses weren't designed to cover gravity and, while the instructor was honest about what he presented, it was actually a violation of U.S. Code to *disagree when him.

* That is only a slight exaggeration.

• ##### I was learning my physics from the Feynman books(0+ / 0-)

at that age, so my HS physics teachers made me teach the class on QM.

American Presidents: 43 men, 0 women. Ready for Hillary

[ Parent ]

• ##### Umm, yes you can measure variations on a local(1+ / 0-)
Recommended by:
Tomtech

level in gravity experienced at a point. Think about it, it is NOT rocket science.

Two giant cubes.

I place the first giant cube in the middle of the Nevada salt flats .... it is a 100 Cubic kilometer (10x10x10) cube of solid Lithium. I stand on top of it and measure gravity.... X

I now place a different giant cube in the same place, a 100 cubic kilometer cube of solid Uranium. I stand on top of it and measure gravity .... Y

Guess what, Y > X.

Because my PROXIMITY to the concentration of Uranium results in my perceiving higher gravity that my same proximity to Lithium.

However, regardless of how I arrange a pile of matter on the surface of the Earth, if I go out to 280,000 Miles above the surface of the Earth, the gravity s the same.

Whether I put the Uranium in China and Lithium in USA or vice-versa.

Gravity, as with any attractive force, falls off as the CUBE ROOT of the distance.

So OF COURSE you can measure micro-variations of gravity at different locations of ANY cosmic body that is not of UNIFORM structure.

The only Mystery is how stupid people can be.

• ##### some corrections(4+ / 0-)
Recommended by:
Tomtech, RickD, The Jester, atana

Not wanting to be pedantic, but...

The volume of a 10x10x10 km cube is 1,000 cubic kilometers, not 100.

The difference in gravitational attraction between Lithium and Uranium cubes of similar volume is not due to proximity but due to different density and thus different mass.

Gravity falls of as the inverse square of distance, not as a cube root.

Not all attractive forces work similarly. The strong force actually increases with distance ... and that is incidentally the reason why we cannot observe naked quarks -- when you pull two quarks far away from each other, instead of the meson getting unraveled it becomes two mesons, with the energy used for pulling converted into a quark-antiquark pair that binds to the dislocated quarks.

• ##### Yeah Oops, hadn't had my coffee yet. But(0+ / 0-)

Yes the mass is higher, so the instruments sensitive enough to be measuring an alleged difference would see a difference between a mountain of Lithium (I pick because it's hard to stand on a mountain of Hydrogen metal on earth) and a mountain of uranium.

The Earth's crust is NOT uniform, it is a conglomeration.

So I'm just pointing out that as a localized effect you can perceive differences in "gravity" if the instrument is sensitive enough, but it is not due to something WRONG with gravity, just the varying net proximate density of the earth you are standing on with the instrument.

In the BIG picture, Gravity is the manifestation in our universe [equal but opposite reaction] of the repellant force keeping our dimension/universe from colliding with neighboring dimension(s)/universe(s).

Where matter/energy cease to exist, there is no repellant force and no Gravity and collision ensues.

We call the most recent instance of this collision:

THE BIG BANG

• ##### But what happens when you stand beside the cube?(1+ / 0-)
Recommended by:
The Jester

If you placed a plumb bob 15 feet from the base of the uranium cube it would be deflected towards the cube. That is the phenomenon I observed.

• ##### Yes, I would assume the gravity of the cube would(1+ / 0-)
Recommended by:
Tomtech

Tug infinitesimally in the direction of the higher density material.

• ##### Republished to the KETI Project...(0+ / 0-)

...just because!

Float like a manhole cover, sting like a sash weight! Clean Coal Is A Clinker!