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NASA Still Trying to Verify Anti-Gravity Claims
uncoda writes "The L.A. Times has an article about NASA research into a phenomenon in which the effect of gravity is supposedly reduced. It sounds like cold fusion or polywater to me, but who knows?" We've posted two previous stories about Podkletnov's research: one from a couple of years ago and another more recently.
This has been going on for a while. See the most recent note on this subject from Bob Park's "What's New." He refers to an earlier $2M that got dropped on this crackpottery.
Quote: "Gravity has NOTHING to do with mass, anyone who took high school physics should be able to tell you that."
Actually, gravity depends on three things,
1) The mass of the object that is being attracted
2) The mass of the object 1) is attracted to(typically much greater than the mass of 1))
3) The distance separating the two.
This relationship is called Newton's law of gravitation:
F(gravity) = G*(mass(small)*mass(big))/(distance)^2
Gravity has NOTHING to do with mass, anyone who took high school physics should be able to tell you that.
Check your high school physics notes again. Gravity has everything to do with mass. Gravity is the attraction of objects to each other because of their mass. Every object posessing mass has a gravitational field. The strength of that field is proportional to the amount of... wait for it... mass.
If you witness/measure less gravitational force in a system, you can conclude at least one of three things, according to the high school physics you speak of:
1. The universal gravitational constant has been reduced.
2. One or more masses in the system have been reduced.
3. The distance between the masses has been increased.
Evgeny Podkletnov and Giovanni Modanese have posted one of their papers on the arXiv: http://xxx.lanl.gov/abs/physics/0108005
From the article:
...
The law of gravity is one of science's most sacrosanct principles; any breaching of its walls would represent a major threat to the current theoretical framework.
Really? One of the few things I can remember from my Physics courses at school is that noone understands why gravitation mass is the same as intertial mass. The closest anyone's got to an explanation is Einstein with his Equivalence Principle, but even this seems a bit woolly (only works in a uniform gravitational field). So there are still aspects of mass (and so gravity) that are not fully understood.
Of course, this experiment sounds rather dodgy, and it's unclear from the article what they're measuring. Got me wondering though
Sustained rotation in a given plane (as when in a rotating craft) causes the inner-ear fluid to flow with the same angular velocity. If the head is moved out of the plane of rotation (as by turning your head), the continuing fluid movement in the old plane gives a sense of rotation in the new plane, even though no such movement is occurring. This disorienting and nauseating sensation, called Coriolis cross-coupling, is made worse by high rotation rates and short radial arms. Any movement not parallel to the axis of rotation will provoke Coriolis forces. An astronaut climbing towards the axis of rotation decelerates as he/she moves into an area of lower velocity, and experiences a force in the direction of rotation. An astronaut climbing down the same ladder feels a force pushing him/her against the direction of rotation. An astronaut running in the direction of rotation gains angular velocity and thus feels heavier, and one running against rotation feels lighter. Research at NASA Langley Rotating Space Station Simulator indicates that ambulation in the direction of rotation at rotation rates corresponding to greater than 0.3 g produces a disturbing heaviness in the legs, while ambulation against the direction of rotation is not possible below 0.05g. Finally, Coriolis forces act on any moving object; even fluid poured in a rotating field deviates in its course.
Then there's the problem of gravity gradients. Centripetal acceleration (the 'gravity') is a linear function of radius; thus, there is a 100% gravity gradient running from the axis of rotation to the outer rim. An object weighing 10 kg on the 'floor' (rim) would weigh 5 kg if moved half-way up towards the 'ceiling' (axis). The percentage weight change an object moving from a point Ra to a point Rb experienced is given by:
W1/W2 = (Ra - Rb)/Rb
Thus, an object raised to a 1 meter shelf in a 4-meter rotating station (from Ra = 4 m to Rb = 3 m) would lose 25% of its weight. It is unknown how this sudden weight loss would affect materials handling; e.g., would a suddenly lightened box tend to fly out of one's hands?
In addition, a 2-meter tall astronaut standing in a 4-meter rotating station would feel literally 'light-headed'; the head (nearer the axis of rotation) weighs 50% less than the feet!
Despite these concerns, the gravity gradient appears to be the problem of least concern in designing a rotating habitat, and was considered a 'non-problem' in NASA's recent Artificial Gravity Working Group.
How we know is more important than what we know.