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Frame Dragging by Earth Reconfirmed
smooth wombat writes "After 11 years of watching the movements of two Earth-orbiting satellites, researchers found each is dragged by about 6 feet (2 meters) every year because the very fabric of space is twisted by our whirling world.
The results, announced today, are much more precise than preliminary findings published by the same group in the late 1990s.
The researchers say their result is 99 percent of the predicted drag, with an error of up to 10 percent. The details are reported in the Oct. 21 issue of the journal Nature."
What one of the recent satelites was sent up to do?
Hmmm... I read this earlier because CNN jumped on it, but there are questions (noted in the Nature article) about its actual accuracy. There's some concern that the original gravity field maps that this method used weren't accurate enough.
This is a good step forward, but I think until we call the frame dragging prediction confirmed we should wait to see what Gravity Probe B comes up with.
Alito: A vote for Alito is a punch in the eye to put that bitch back in her place!
The original linked article IS CNN's writeup. Read the Nature article. CNN may have beat them to the punch, but there's some question as to the accuracy of these findings that CNN conveniently didn't mention.
Alito: A vote for Alito is a punch in the eye to put that bitch back in her place!
Read up the history of this project sometime. This is the longest running single project in the history of the federal government, it took like 50 years to complete because they kept getting stalled and most of the work was being done by grad students. In order to do this experiment they had to build what are, more likely than not, the two most perfectly round objects in the entire universe and then spinning them really really really quickly in a vacuum in outer space.
Crazy shit.
You're thinking of NASA's Gravity Probe B. That one isn't finished yet.
"with 1% accuracy" is perfectly acceptable. If you have a meter stick that you can measure the length of something "with 1 mm accuracy," that's what you're interested in. The statement you quote means Gravity Probe B will be able to measure with an accuracy of 1% of the predicted value.
Actually, the article could do better to explain the difference between the law of gravity (which is the mathematical formula which describes the attraction between two masses) and the theory of gravity, which attempts to explain how or why two masses attract each other exactly that way.
Ideology: A tool used primarily to avoid the bother of thinking.
This idea of this drag was originally proposed by Einstein. Almost fifty years ago, the idea of how to experimentally verify this effect was proposed; however, it required the launch of a very accurate gyroscope. That gyroscope, which is the center-piece of the longest running NASA project ever, was just recently launched into space. More info about it (Gravity Probe-B) and a good description of this drag can be found at http://einstein.stanford.edu. Yes, the article is describing a different project than GP-B; however, it references the skeptism that the folks at GP-B have expressed at this latest experiment, and the GP-B folks are considered the experts in the field. Check out their site, it's fascinating.
No. Scientific theories don't get promoted to laws. Laws are observations of things that appear to hold true. For example, the law of gravity ("what goes up, must come down"), Snell's Law, Ohm's Law, the Law of conservation of Mass/Energy, the Laws of Thermodynamics, etc. A theory is an *explanation* that models some observed phenomena and which has the power to predict other phenomena. Theories are either falsified (i.e. proven wrong), or are confirmed (i.e. shown to be consistent with some new observation.) Theories are never proven true; rather, they are simply confirmed to a greater and greater degree. No matter how well a theory is confirmed, it can always be falsified by a new experiment testing some as-yet-untested prediction. In this case, the theory is either revised to account for the new observation, or it is simply discarded.
For those of you like me who didn't have a clue what this article is about check out the Wikipedia entry for frame dragging.
Plus, they say that the drag is about 6 feet or 2 meters? Not quite. I must nitpick.
2 meters is about 6'7", or 6 feet is about 1.82 meters. So which is it?
The metric system strikes again, I guess.
I couldn't fail to disagree with you less.
Frame dragging IS the simpler explanation :)
frame dragging was predicted in the early 1900s by the various equations that make up relativity. if we were to observe that it wasn't happening and some other effect were causing it, then that would be very odd indeed, as that would imply that all the equations which have been right in so many other ways are wrong in this one little regard making things much much more complicated.
The simplest possible explanation for this is frame dragging.
Also, the gravity effects you mention would not affect the sattelite in this way, a downward pull has no effect on the horizontal motion of a satellite and the moon and suns gravity can easily be accounted for. Also, imagine the root cause was the moon and suns gravity, then that would imply there is something fundamentally new about the gravitational laws we do not yet understand, which again is very interesting and much more complicated than frame dragging.
http://notanumber.net/
Newton's laws have not been proved, they are just very likely. And there are some problems with them. So why not extend this naming to relativity?
I could say "My theory includes everything in General Relativity, except for a small sphere four miles wide in the center of Andromeda, where light travels twice as fast."
Then while you have a theory that has not been disproved, Ockhams Razor advises us to use the simplest one that explains all the data, and that's not yours.
Yes, this makes truly proving anything in the physical world basically impossible.
Which is why it is not a good idea for us to require theories to be "proven" before becoming "natural laws". We call a proven "theory" a "theorem".
This post written under Gentoo-linux with an SCO IP license.
I took a course on the philosophy of modern physics at university and on the our text books was Einstein's own called Relativity : the Special and General Theory fairly informative and yet accesible. It is available for free from Project Gutenberg. Just click on the first link.
Your CPU is not doing anything else, at least do something.
The moon doesn't move into the depression. The moon , like every other object, keeps traveling in a straight line until it collides with something. All the depression does is change the shape of a straight line. Any object in "free fall" is travelling in a straight line through curved space. Yes, satellites in orbit are falling unhindered in a straight line - that looks like a circle due to the curvature of space.
You're missing the OP's point. His computer analogy obviously doesn't hold literally; he's trying to explain that causality doesn't have much sway in Modern Physics. While we may be unable to send our entire bodies back in time, particles do it essentially all the time. It seems as though our current understanding of physics (both on the macroscopic general relativity scale and on the microscopic quantum scale) not only allows but actually encourages this kind of bizarre behaviour.
The confusion comes from classical mechanics, where we typically would model real-world behaviour parametrically -- and time was the parameter. So for example, we would explain the movement of a particle as vector function of time. This works fine, most of the time. But it isn't general enough.
Relativity showed that time is not a parameter anymore than classical dimensions could be considered a parameter, it's just that we perceive it that way. Time is actually a quantity much like space. It doesn't behave exactly the same way, but that's a result of the metric of the spacetime continuum (see Lorentz transforms in Special Relativity for an example of this).
So, now we have a particle occupying a position (x,y,z,t) instead of occupying a position (x,y,z) at a particular time t. In the same way that we accept that a particle can retrace its path when moving along the x axis, we must accept that a particle can move backwards on the t axis (it just isn't thermodynamically efficient to do so).
Let's talk about you and your grandfather. Your grandfather is at point (x,y,z,t) and you are at point (x',y',z',t'), presumably with t' > t. You time travel back to time t, and kill him. He ceases to exist at (x,y,z,t).
Now, because time is a positional coordinate, if you will, and not a parameter, you have not "arrested his movement". People like to wrap their heads around this by imagining that in changing the past you have "forked" the universe and that this new forked version will never produce you, but you aren't destroyed because you come from a different version of the future.
The point is that physics doesn't care why you came into being, only that you came into being. You exist; you will not cease to exist just because the thing that "created" you was destroyed. This leads philosophers to suggest that everything exists inherently, and that we just pick our way through a myriad of decision universes. It's a way of making our logic apply to physics. At the moment there's no evidence for it.
The "kill your grandpa" paradox was used in the old days to explain why time travel was impossible; and yet time travel is manifestly possible, even if harnessing it poses an engineering problem. It happens at the particle level all the time (positrons are electrons moving backwards in time, says Feynman). This suggests, then, that our starting principle is flawed (reducto ad absurdum). The "fall guy" in this case is causality. Causality doesn't matter. We hold on to it because we have memory. But cause can follow effect, etc... I mean, it's a bizarre world we live in.
You obviously don't understand margin of error. The large error suggests imprecise measurement, the central limit suggests that the end value will in fact be close to the predicted. 99% +/- 10% is more promising with regards to the theory than 99% +/- 0.01% would be.
Statistics lesson.
Margin of error is not a bound within which any result is equally likely. Depending on the distribution, it can be anywhere from equal likelihood (uniform distribution, which is extremely rare in natural processes) to single point (in which case the MOE is obviously zero, and the result is definitive.) For example, most things with a binary outcome (yes or no, 1 or 0, etc) follow what's known as the binomial distribution. If the probability of either result is equal, the binomial pattern is equivalent to the normal (Gaussian) distribution, which looks like a bell, and is produced by many processes, especially processes involved in noise and measurement error.
Now, depending on the expected distribution this changes, but for a normal distribution the likelihood is probably 95% that the actual value is within that +/-10% (assuming they're using the typical definition of 2 sigma for margin of error) - but it's around 65% likely that the result is within +/- 5%, and the most likely single result is in fact 99% - not 99% likely, but the maximum likelihood points to 99%.
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Mod me down, you fucking twits. Go ahead. I dare you.
(I read with sigs off.)
Most of people in this thread seem to be very confused, so please let me explain the most basic terms, using the most relevant quotes taken from several Wikipædia articles.
Axiom in epistemology is a self-evident truth upon which other knowledge must rest, from which other knowledge is built up. To say the least, not all epistemologists agree that any axioms, understood in that sense, exist.
Axioms in mathematics are not self-evident truths. They are of two different kinds: logical axioms and non-logical axioms. Axiomatic reasoning is today most widely used in mathematics.
The word axiom comes from the Greek word axioma, which means that which is deemed worthy or fit or that which is considered self-evident. The word comes from axioein, meaning to deem worthy, which in turn comes from axios, meaning worthy. Among the philosophers of the ancient Greeks an axiom was a claim which could be seen to be true without any need for proof.
Laws of logic and mathematics describe the nature of rational thought.
Law of nature or physical law in science is a statement that describes regular or patterned relationships among observable phenomena. It is a scientific generalization based on empirical observations. Laws of nature are conclusions drawn from, or hypotheses confirmed by, scientific experiments. The production of a summary description of nature in the form of such laws is the fundamental aim of science. Laws of nature are distinct from legal code and religious Law, and should not be confused with the concept of natural law.
Often, those who understand the mathematics and concepts well enough to understand the essence of the physical laws also feel that they possess an inherent intellectual beauty. Many scientists state that they use their perception of this beauty as a guide in in developing hypotheses, since there seems to be a connection between beauty and truth.
Physical laws are distinguished from scientific theories by their simplicity. Scientific theories have many of the same properties as laws, but are generally more complex than laws; they have many component parts, and are more likely to change as the body of availabe experimental data and analysis develops.
Theory in mathematics is a set of statements closed under logical implication. In mathematical logic, "theory" is the term for a set of well-formed formulae consisting of certain axioms and all theorems provable from said axioms. Gödel's incompleteness theorem states that no theory (formalized using a consistent set of axioms in First-order logic), that defines the concept of natural numbers, can include all true statements.
Theory in sciences is a model or framework for understanding. In physics, the term theory generally is taken to mean mathematical framework derived from a small set of basic principles capable of producing experimental predictions for a given category of physical systems. An example would be "electromagnetic theory", which is usually taken to be synonymous with classical electromagnetism, the specific results of which can be derived from Maxwell's equations.
The term theoretical to describe certain phenomena often indicates that a particular result has been predicted by theory but has not yet been observed. For example, until recently, black holes were considered theoretical. It is not uncommon in the history of physics for theory to produce such predictions that are later confirmed by experiment, but failed predictions do occur. Conversely, at any time in the study of physics, there can also be confirmed experimental results which are not yet explained by theory.
For a given body of theory to be considered part of established knowledge, it is usually necessary for the theory to characterize a critical experiment, that
Sincerely,
Pan Tarhei Hosé, PhD.
"Homo sum et cogito ergo odi profanum vulgus et libido."
Well, the Adam and Eve issue (as someone else pointed out) is that we don't have enough genetic diversity in one couple to produce all of humanity. Just consider the inbreeding problems that the royalty of Europe had a few hundred years ago due to intermarriage. If you wanted to populate the moon, for example, you could not just send one couple. Within a few generations, inbreeding related problems would be their downfall.
Bad example -- the Eve Hypothesis seems to indicate that all of humanity is decended from a relatively "small" population of humans (where "small" is defined as less then 20k).
There is also a corresponding Adam Hypothesis
In science, tiny populations can give rise to large populations (Founder's Effect), although sometimes there are side-effects.
Wisent (European Bison) are all decended from twelve individuals. Wisent bulls suffer from some lack of diversity, only having two distinct Y-chromosomes in their genetic pool, but there are only limited effects from interbreeding.
Golden Hamsters tend to be all decended from one litter found in Syria in 1930.
IIRC, Noah was supposed to have several people on the Ark -- himself, his children, and his children's spouses. Although clearly not an optimal setup, it would probably be enough to prevent the species from dying out.
I wouldn't be surprised if some islands in the world started out with roughly the same population.
Don't get the wrong impression -- I'm not arguing for Creationism or literal interpretations of the bible. I just don't want to see bad science being repeated.
Somewhere, General Relativity must break down so that it can match up with wherever Quantum Mechanics breaks down, permitting the two theories to be joined in some coherent fashion.
Read up on string theory. Neither GR nor QM must "break down" to join them together. But science makes progress by assuming that existing theory is always improvable, so a search for where existing theory fails will continue as long as science continues. But the math of strings that combines GR and QM does not break either like Newton's laws which ARE broken by both GR and QM.
May be you need to learn basic math? The result predicted by theory was 2.02 meters. Their measurement was 2 meters, but this is just an estimate and the correct result (real) should be between 1.8 and 2.2 meters (with a probability of something, such as 95 or 99% - not mentioned in the article).
According to current results, the theory may be correct (may be even "is likely to be"). But of course, we need more precise measurements.
Future Wiki -- If you don't think about the future, you cannot have one.