However, I really was gobsmacked by the level of scientific illiteracy
in the article “Fly by Light” in the 9 September 2006 issue,
concerning the supposed “electromagnetic drive” of Roger Shawyer. If
Shawyer’s claims have been accurately reported, they violate
conservation of momentum. This is not a contested matter; in its
modern, relativistic form it is accepted by every educated physicist
on the planet. The writer of this article, Justin Mullins, seems
aware that conservation of momentum is violated, but then churns out a
lot of meaningless double-talk about “reference frames” which he seems
to think demonstrates that relativity somehow comes to the rescue:
Hang on a minute, though. If the cavity is to move, it must be pushed by
something. A rocket engine, for example, is propelled by hot exhaust
gases pushing on the rear of the rocket. How can photons confined inside
a cavity make the cavity move? This is where relativity and the strange
nature of light come in. Since the microwave photons in the waveguide are
traveling close to the speed of light, any attempt to resolve the forces
they generate must take account of Einstein’s special theory of
relativity. This says that the microwaves move in their own frame of
reference. In other words they move independently of the cavity - as if
they are outside it. As a result, the microwaves themselves exert a push
on the cavity. Each photon that a magnetron fires into the cavity creates an equal and
opposite reaction - like the recoil force on a gun as it fires a bullet.
With Shawyer’s design, however, this force is minuscule compared with the
forces generated in the resonant cavity, because the photons reflect back
and forth up to 50,000 times. With each reflection, a reaction occurs
between the cavity and the photon, each operating in its own frame of
reference. This generates a tiny force, which for a powerful microwave
beam confined in the cavity adds up to produce a perceptible thrust on
the cavity itself.
