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A LIGHT wave, when reflected 1 at the surface of separation of two media, may be altered in amplitude, or wavelength, or phase. Whilst, however, a change of amplitude or wave-length produces an ...

FURTHER experiments on the reflection of hydrogen positive rays from crystals, similar to those described in NATURE for Jan. 11, have shown that the phenomenon is more complex than might have been ...

Can we turn back time? Ask a savvy physicist, and the answer will be “it depends.” Schemes for retrograde time travel abound but usually involve irreconcilable paradoxes and rely on outlandish ...