'Radio-loud' quasars - which are brighter at radio wavelengths
than in the optical range - emit two narrow beams of radiation
that emerge from opposite edges of the quasar. Blazars are a
type of radio-loud quasar that periodically send violent pulses
of radiowaves into space and were originally defined by the
'synchrotron' radiation that they emit when electrons are
accelerated in a magnetic field. But astronomers proposed five
years ago that this characteristic spectrum is only seen if the
beams of radiowaves are viewed end-on. This would mean that many
blazars had gone undetected. As the angle of observation
increases away from the beam, the synchrotron profile weakens,
and the spectrum changes further as the angle grows.  Ma and
Wills compared two sets of spectra of 62 quasars - one gathered
between 1998 and 2000, and the other ten years earlier. Some of
the recent spectra exhibited emission lines over 20% stronger
than those in the corresponding older spectra. These jumps in
intensity occurred over the sa