Dino ha scritto:
> Elio Fabbri ha scritto:
Punto primo: ti dispiacerebbe scrivere il mio cognome come si deve?
Scusa, ma su questo sono un po' suscettibile, perche' "Fabri" con una
sola "b" e' relativamente raro, e quindi ci tengo :-)
> Comunque volevo chiedere se qualcuno sa se tale esperimento � stato
> effettivamente fatto.
Non credo. Pero' tieni presente che da parecchi anni esiste una rete
di orologi atomici situati nei piu' diversi punti del globo per
latitudine e altezza s.l.m.
Questi orologi sono tenuti sotto controllo continuo tra loro, e per
farlo occorre tener conto appunto degli effetti dovuti alla loro
diversa posizione.
Se le previsioni della RG fossero errate in qualche modo, questi
confronti lo rivelerebbero senza fallo.
BTW, lo stesso problema si presento' quando vennero messi in orbita i
satelliti del sistema GPS, e c'e' una storia curiosa, raccontata da
Ashby:
http://relativity.livingreviews.org/Articles/lrr-2003-1/
Dato che puo' interessare anche ad altri, riporto il brano centrale:
"There is an interesting story about this frequency offset. At the time
of launch of the NTS-2 satellite (23 June 1977), which contained the
first Cesium atomic clock to be placed in orbit, it was recognized
that orbiting clocks would require a relativistic correction, but
there was uncertainty as to its magnitude as well as its sign. Indeed,
there were some who doubted that relativistic effects were truths that
would need to be incorporated [5]! A frequency synthesizer was built
into the satellite clock system so that after launch, if in fact the
rate of the clock in its final orbit was that predicted by general
relativity, then the synthesizer could be turned on, bringing the
clock to the coordinate rate necessary for operation. After the Cesium
clock was turned on in NTS-2, it was operated for about 20 days to
measure its clock rate before turning on the synthesizer [11]. The
frequency measured during that interval was +442.5 parts in 10^12
compared to clocks on the ground, while general relativity predicted
+446.5 parts in 10^12. The difference was well within the accuracy
capabilities of the orbiting clock. This then gave about a 1%
verification of the combined second-order Doppler and gravitational
frequency shift effects for a clock at 4.2 earth radii."
--
Elio Fabri
Received on Wed Apr 22 2009 - 21:22:13 CEST