I have been reading Lee Smolin's "The Trouble With Physics" (by Penguin Group, 2006) and Roger Penrose's "The Road to Reality" (by Vintage Books, 2004). I have also studied physics all the way through upper high school, 3 years, for the Norwegian equivalent of GCSE Science and I've looked carefully into Bayesian problems in philosophy (relating to the Raven's Paradox by Carl Hempel).
Cheers!
[Edit:] I withdraw the accusation of NASA, although I claim to have seen the wrongful statement on one of their webpages. Here is a better reference: http://helios.gsfc.nasa.gov/qa_gp_elm.html. It says:
I must say, though, that the web is marred by numerous assertions like these (thus impelling me to do some public education): http://van.physics.illinois.edu/qa/listing.php?id=2009.Magnetic Fields and Light
I recently read that the magnetic fields found in pulsars are strong enough to change the vacuum index of refraction. Does this mean that it is possible to use magnetic fields to bend light? I thought that the vacuum index of refraction couldn't be changed. How does this mechanism work?
Yes, the vacuum index of refraction can change. This is a consequence of quantum field theory, where virtual electron-positron pairs result from vacuum fluctuations. These e-p pairs cause a virtual polarization of the vacuum, which can then change the index of refraction.
Recent work also shows that a strong magnetic field can affect the vacuum polarization through its effect on the e-p pairs. This then changes the vacuum index of refraction. This of course then implies that light rays can be bent by the influence of the magnetic field.
I do not know of any experimental verification of this effect.
Dr. Randy Jokipii
(November 2003)
It says:
The underlining is on me. So this is the reason for making this topic. Not that I intend to ridicule people, but rather to set the standard straight!How far can a magnetic field bend light? Could it be bent enough so that it goes around a three dimensional object and comes out (after going 180 degrees, I guess) the other side, being bent by the magnet, therefore making it seem as though the object had the light bass through it completely, and it does not appear to the human eye? Here is the best example I can give: -->=light, O=Object, *=mag. field, / or \=light bent. ___ |***| If this can be done, please tell --->/*O*\---> me how, and what would be needed to perform such a thing. Thank you. (PS - This would need to be done in a round sense, as in all around the 3-d object, not in just one line, so please keep that in consideration. Also, if you know any other way to get the desired effect please inform me.)
- Jon (age 15)
The King’s Academy, Marion, IN, U.S.A.
A:
Hi Jon --
Nice try. Unfortunatley, the path light takes is not affected by the presence of a magnetic field. Light itself is composed of an oscillating electric and magnetic field, and one very important property of electric and magnetic fields is what we call "linearity." That is, if you have two sources of electric and/or magnetic fields, you can predict what the combined field is just by adding the two source fields together. The two fields don't change each other at all. So if you add the field of a light ray to any other field we can imagine, the light ray will continue as before and the extra field will just stay the same, adding to it in places where the extra field is strong, but having no effect beyond the reach of the extra field. So there is no way that a magnetic field can bend light.
