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BRS: A very common misunderstanding of how science works
In "Are the foundations stable"
EnergyLoop asks
This seems to have become a very common refrain, particularly since the recent discovery of an accelerating expansion. (Cosmologists quickly adjusted; the general public did not!) I'd actually like to see a PF FAQ somewhere which addresses this, mentioning some of the same points I've made so often in the past, including:
In "Dark Matter Distribution Around Galaxies"
RLutz asks
In "Black Holes are Tears in Space"
In "Re: Big Bang and PreExisting Void?"
JDoolin, whose "knowledge" of cosmological models is apparently based upon Wikipedia, not textbooks plus graduate level schoolwork, is arguing with Chalnoth and others about the Milne chart for the Minkowski vacuum, claiming that this chart is "inequivalent" to the cartesian chart. Of course that hinges on the meaning of "inequivalent"; gtr is however based upon Lorentzian geometry, and in Lorentzian geometry, any chart covering a region U in a spacetime (M,g) is just as good as any other.
In "velocity of gravity wave"
spikenigma seems to think the European Gravity Field and Steady-State Ocean Circulation Explorer project has something to do with comparing the speed of gravitational and EM radiation! Needless to say, the investigators say something very different: from
In "Are the foundations stable"
Code:
physicsforums.com/showthread.php?t=429435
We are constantly finding new information that does not fit the current model, but by adding a new constant or variable into the equations it repairs the problem, but gives us new things to look for such as dark matter and dark energy. I can’t help thinking about Aristotle’s crystalline spheres and the Earth centered universe, this was a simple concept initially, until the motion of the planets was realized, then it became a complex mathematical model to try to explain this motion, Copernicus then simplified the problem, and removed the complexity.
I hope we are not heading in that direction again, is the foundation sound, equations are build on previously established equations does anyone re-examine these?
This seems to have become a very common refrain, particularly since the recent discovery of an accelerating expansion. (Cosmologists quickly adjusted; the general public did not!) I'd actually like to see a PF FAQ somewhere which addresses this, mentioning some of the same points I've made so often in the past, including:
- All scientific knowledge is provisional. Constantly finding new information and constantly trying to fit new data or theoretical speculations into the body existing well-established theories is precisely what scientists do on a day-to-day basis. The fact that scientific theories can be tested by comparing quantitative predictions with quantitative data, and the fact that scientific theories are constantly up for revision is what makes science the most powerful tool known to man for the discovery and organization of knowledge about the natural world.
- Scientific knowledge consists of a vast body of experimental/observational data plus the terminology, notation, and theories we use to interpret the data. We make theories and we make predictions from theories using mathematical reasoning, and you need to know the appropriate mathematical background to understand the theories.
- When new data cannot be fit into existing theories, scientists look for explanations. First and foremost, a careful examination of the possibility that the data collection or analysis contained some subtle systematic bias or other flaw. If that fails, then one searches for the change to the theories which is "the least possible".
- The public seems to generally misunderstand the nature of scientific advances: they should be astonished not by how much has changed, but by how little, even in such an extreme revelation as the "accelerating Hubble expansion". That is, one benefit of knowing the data and the theories is that you can appreciate how "introducing nonzero Lambda" is actually the smallest possible change to the theories. Also, the data hasn't changed, only our interpretation. Making a minimal change means that only a very small portion of our interpretation/understanding of the universe changed as the result of that particular "cosmological revolution".
- To repeat: the public seems to generally misunderstand the nature of scientific revolutions. Newtonian gravitation was never "discarded", it is still used, and more often than gtr, which is a bit harder to work with. If and when a successful theory of quantum gravity appears, gtr will still be used (most likely) because the new theory will be (most likely) a bit harder to work with. Similar remarks hold for non-relativistic physics, and various specific theories which are known to be "wrong" but are still useful for limited purposes.
In "Dark Matter Distribution Around Galaxies"
Code:
www.physicsforums.com/showthread.php?t=429521
Ditto Chalnoth, plus a reminder that a black hole of mass M gravitates just like any star of mass M; unless you are very close to it you won't encounter the strong portions of the exterior field which result from the fact that the hole is so much more compact than the star.Is there any reason why galactic black holes might have something to do with dark matter creation? The squashed beachball of dark matter sort of looks like what I would expect say field lines coming out of a pulsar to look like or something.
In "Black Holes are Tears in Space"
Code:
www.physicsforums.com/showthread.php?t=429376
Actually, that is tragic. Due to the global financial crisis, at least one state university in the U.S. has just eliminated its science majors.I`m not a scientist, i`m actually a 3D Artist. I just have a lot of faith in science unfortunately didn`t have the attention span to pay attention enough in high school and even more tragic is that my university didn`t offer any science courses!
It's vaguely reminiscent of various possibilities discussed in serious physics like wormholes or curvature singularities, but much too vague to make much sense in a scientific discussion. So the best short answer is probably: a black hole is a region of spacetime characterized by the presence of an event horizon, which you can think of as an imaginary surface which you can fall through, but once you do, you can't ever emerge from behind the horizon, at least not into the same external region of spacetime in which you started. A very good book for poets which IMO can enable persons with only a high school science education to actually understand this, sort of, from (good!) pictures, is Geroch, General Relativity from A to B, University of Chicago Press.Could it be possible that a black hole is a tear in space? It seems like it could be a way of explaining why some say you could travel through a black hole or worm hole and wind up somewhere else. If space itself was really in a shape we couldn't comprehend then maybe a tear in one place could wind up opening in an entirely different place. Does that make sense?
In "Re: Big Bang and PreExisting Void?"
Code:
www.physicsforums.com/showthread.php?t=425597&page=4
In "velocity of gravity wave"
Code:
physicsforums.com/showthread.php?t=429166
Code:
www.esa.int/esaLP/ESAJJL1VMOC_LPgoce_0.html
GOCE will be gathering data or around 20 months to map the Earth's gravity field with unprecedented accuracy and spatial resolution. The final gravity map and model of the geoid will provide users worldwide with a well-defined data product that will lead to:
- A better understanding of the physics of the Earth's interior to gain new insights into the geodynamics associated with the lithosphere, mantle composition and rheology, uplift and subduction processes.
- A better understanding of the ocean currents and heat transport.
- A global height-reference system, to serve as a reference surface to study topographic processes and sea-level change.
- Better estimates of the thickness of polar ice-sheets and their movement.
One can use the next section to compute whether or not GOCE will be able to track ballistic missile submarinesbut in any case, it will be clear to anyone here, I think, that GOCE has nothing to do with "speed of gravity".