Einstein on CD

Einstein on CD
22 March 2005

Albert Einstein became famous before the advent of the mass media so there are very few recordings of him. However, as part of the celebrations of Einstein's famous discoveries in 1905 the British Library has released a CD containing various speeches and radio broadcasts by the great physicist. Although the CD starts with a 57 second explanation of E=mc2, most of the material concerns Einstein's interest in international affairs and the fate of the Jewish people.

The centrepiece of the CD is a 25 minute eulogy to Einstein by the Irish playwright George Bernard Shaw recorded at a dinner in support of two Jewish charitable organizations at the Savoy Hotel in London on 28 October 1930. Shaw contrasts Einstein's greatness with that of leaders like Napoleon. Men like Einstein, says Shaw, "are not makers of empires, but they are makers of universes. And when they have made those universes, their hands are unstained by the blood of any human being on earth....cont'd

http://physicsweb.org/articles/news/9/3/13/1


Seeing the Planks in Einstein's Cross



Summary - (Mar 21, 2005) All Quasar's have black holes for hearts - but that doesn't mean they are unfriendly. In fact, 9 billion light year distant QSO2237+0305 may like us so much that it wants to make sure we see it even though it is actually hidden by a much nearer spiral galaxy. What can we learn from QSO2237+0305? For one, the cross that bears Einstein's name can tell us a lot about space-time curvature. For another, it can teach us invaluable lessons about how to see things otherwise hidden from view. If you have access to the scope and the skies, you too can see what the whole spectacle is all about.

Spiral galaxy PGC 69457 is located near the boundary of fall constellations Pegasus and Aquarius some 3 degrees south of third magnitude Theta Pegasi - but don't dig out that 60mm refractor to look for it. The galaxy is actually some 400 million light years away and has an apparent brightness of magnitude 14.5. So next fall may be a good time to hook up with that "astro-nut" friend of yours who is always heading off into the sunset to get well away from city lights sporting a larger, much larger, amateur instrument...

But there are plenty of 14th magnitude galaxies in the sky - what makes PGC 69457 so special?

To begin with most galaxies don't "block" the view of an even more distant quasar (QSO2237+0305). And should others exist, few have just the right distribution of high-density bodies needed to cause light to "bend" in a way that an otherwise invisible object is visible. With PGC 69457 you get not one - but four - separate 17th magnitude views of the same quasar for the trouble of setting up one 20 inch truss tube dobsonian. Is it worth it? (Can you say "quadruple your observing pleasure"?)

But the phenomenon behind such a view is even more interesting to professional astronomers. What can we learn from such a unique effect?

The theory is already well established - Albert Einstein predicted it in his "General Theory of Relativity" of 1915. Einstein's core idea was that an observer undergoing acceleration and one stationary in a gravitational field could not tell the difference between the two on their "weight". By exploring this idea to its fullest, it became clear that not only matter but light (despite being massless) undergoes the same sort of confusion. Because of this, light approaching a gravitational field at an angle is "accelerated toward" the source of the gravity - but because the velocity of light is constant such acceleration only effects light's path and wavelength - not its actual speed.

Gravitational lensing itself was first detected during the total solar eclipse of 1919. This was seen as a slight shift in the positions of stars near the Sun's corona as captured on photographic plates. Because of this observation, we now know that you don't need a lens to bend light - or even water to refract the image of those Koi swimming in the pond. Light like matter takes the path of least resistance and that means following the gravitational curve of space as well as the optical curve of a lens. The light from QSO2237+0305 is only doing what comes naturally by surfing the contours of "space-time" arcing around dense stars lying along the line of sight from a distant source through a more neighboring galaxy. The really interesting thing about Einstein's Cross comes down to what it tells us about all the masses involved - those in the galaxy that refracts the light, and the Big One in the heart of the quasar that sources it...cont'd

http://www.universetoday.com/am/publish/planks_einstein_cross.html?2132005