Tibor Pacher has been kind enough to publish the text of my public lecture in Aosta, Italy on his PI Club site. The lecture took place at the Aosta town hall and wasn’t part of the ongoing conference just down the street, although some conference participants attended. It’s a broad overview of earlier work on interstellar flight. My intention was to acquaint non-scientists with the fact that the subject has been under study for decades in ways that do not violate the laws of known physics. A major challenge is how to scale some of the colossal engineering involved down to realistic levels.
Although I only touched upon it in the lecture, I often talk about the twin tracks of interstellar studies. The first track comprises work that tries to scale current technology up for an interstellar mission. The second track is oriented toward examining physical laws in hopes of finding potential breakthroughs that current theory doesn’t allow. No one knows if such breakthroughs are possible, but we want to keep banging on prevailing ideas to see if there are areas that need revision.
Into the Eclipse
On that score, be aware of tomorrow’s total solar eclipse, which gets particular attention because six Chinese teams will be monitoring the event to look for the possibility of anomalous gravitational effects. Does gravity undergo a slight change during a total eclipse? The French physicist Maurice Allais noted unusual behavior in a swinging pendulum back in 1954 during the eclipse that passed over Paris that year. Since then, measurements to pin down what is going on have been inconclusive. A New Scientist story provides more background, as does this NASA page, which details subsequent, often contradictory follow-ups.
The first step in this kind of investigation is to find out whether the anomaly actually exists. The six Chinese monitoring sites will include gravimeters and pendulums, and will encompass a large enough area (3000 kilometers between those that are farthest apart) that local changes in weather or problems with instrumentation should be ruled out. If General Relativity is in need of a tweak, these results could provide a clue.
Explaining an Anomaly
Back in 2004, Chris Duif (Delft University of Technology, The Netherlands) looked at anomalous eclipse observations to see whether they could be explained by seismic disturbances, meteorological conditions, changes in the geomagnetic field or other possibilities. He found none of these solutions satisfactory, and went on to write:
Although, despite all proposed conventional explanations fail to explain the observations either qualitatively or quantitatively, it is still possible that the reported anomalies will turn out to be due to a combination of some of these effects and instrumental errors. And, of course, there may be yet unidentified conventional causes which play a role. The judgment of some of the experimental results is hampered by the lack of a statistical analysis and/or data of sufficient length. Nevertheless, there exist some strong data which cannot be easily explained away.
So we’ll see what turns up in China. New Scientist quotes Tang Keyun (Chinese Academy of Sciences), as saying: “If our equipment operates correctly, I believe we have a chance to say the anomaly is true beyond all doubt.” That would be a fascinating result, and one that would lead to a great deal of new theorizing about how to incorporate the eclipse anomaly into our current views on how gravity works.
The Duif paper is “A review of conventional explanations of anomalous observations during solar eclipses,” available online.
Am I the only one that thinks that the results will only be able to rule out anything above the instrument’s detection limits? (i.e. a non-detection of any anomalous gravitational effects)
Thomas, while that’s true, what I imagine they would strive to show is whether a particular hypothesis that predicts an effect above the detection limit can be ruled out. However, I have yet to read the paper to see just what they plan.
So, did they find anything?
Doug M.
No word yet on results, I’m afraid.
Now that I’ve read the paper (and Paul’s article more carefully!) I have a better understanding. While the anomaly may be real, the past experiments which show it are very suspect. All attempts to explain the high magnitude of the anomaly by conventional factors or gravitational “screening” are looked at and discounted. So they’re left with (unspecified) non-GR gravitational explanations. That’s the motivation to do the experiment with more rigor, to see if the anomaly persists. From what I understand of their methodology, the anomaly, if present, should be known soon after the experiment concludes. If it’s there, I expect they’d spend some time building a strong defense before publishing or going public. Exceptional claims require exceptional evidence.
I recommend you this article.
“Precise measurement of gravity variations during a total solar eclipse”
Based on a 1997 eclipse.
http://home.t01.itscom.net/allais/blackprior/wang/wangetal.pdf
They write about shielding, but i don’t see how a shielding effect would produce that curve.
Icdvasrm, I agree. The (apparent) gravitational anomaly spikes occur at first contact and last contact. Surely a shielding effect would be maximum when the centre of the moon is directly in line withe sun. This is the opposite of what is observed in that paper, so I don’t see why they jump to this as an explanation.
It’s certainly a weird effect, but I can’t help thinking there must be a more prosaic explanation, perhaps wobbles in the crust or something.
Planets, Great Wall, and Solar Eclipse
Credit & Copyright: Terry Cuttle Brisbane, Australia
Explanation: This dramatic skyscape was recorded during the August 2008 total solar eclipse. The Moon’s silhouette surrounded by a glistening solar corona hangs above the Jiayuguan Fort along the western edge of the Great Wall of China.
Lined-up along the ecliptic plane, all the planets of the inner solar system, Mercury, Venus, Mars, (and Earth!) can also be seen along with Saturn and bright star Regulus, as the Moon’s shadow tracks across the landscape. Beyond the Moon’s shadow, outside the total eclipse track, sunlight still brightens the sky over mountains on the horizon 30 – 50 kilometers away.
Much anticipated, the 2009 July 22nd total solar eclipse will again be visible from China. Planets and bright stars will briefly appear in darkened daytime skies, though a total eclipse won’t be seen from the Great Wall. Still, major cities and populated areas lie along the 2009 total eclipse track that begins in India and sweeps eastward across Asia and into the Pacific Ocean.
http://antwrp.gsfc.nasa.gov/apod/ap090718.html
Our group observed pendulum anomalies during the total solar eclipse (TSE) of July 15, 2009, so
Allais pendulum anomalies during TSEs were probably true.
http://www.ursi.org/proceedings/procGA11/ursi/HP2-25.pdf
:)
also this is interesting: http://preprint.nstl.gov.cn/main.html?action=showFile&id=2c928282294f991101295516dcac0002
Thanks chinagoeson.
I cannot retreive the preprint. could you generate a pdf of it ?