880880
MACH, ERNST
just as the object was passing through the experimental
space or Schlieren Head.
Beginning in 1884 Ernst Mach began using the
Schlieren Method to photograph bullets fi red by a pis-
tol, drawn into a controversy about whether or not the
French had used illegal explosive bullets, outlawed in
the Treaty of St. Petersburg of 1868, during the Franco-
Prussian war of 1870–71. New French rifl es had caused
extreme, crater-like wounds, and throughout the 1870s
a number of explanations for the phenomenon had
been put forward, including an idea suggested by Louis
Melsens of Belgium that a spherical projectile carried
compressed air with it in fl ight, the amount depending
on its velocity. In his fi rst experiments Mach saw no
signifi cant turbulence in the air because the bullets
were travelling too slowly; he asked his colleagues
Peter Salcher and S. Riegler at the Marine Academy in
Fiume to continue his experiments, and they modifi ed
another Schlieren apparatus to Mach’s specifi cations,
photographing bullets fi red from several types of rifl es.
In summer 1886 the shock waves from a bullet travelling
faster than the speed of sound were photographed for
the fi rst time. Mach, assisted by his son Ludwig, then
continued the experiments that autumn making more
photographs of the air turbulence around a variety of
projectiles, and even built a remarkable apparatus at the
Krupp artillery range in Meppen where a 4 cm rapid-
fi ring cannon was fi red through a specially-built shed
that provided the darkness needed to make a photograph
where the plate was exposed by illumination from an
electric spark. Mach began publishing his results with
Salcher in 1887, and caused much excitement in both the
scientifi c and photographic worlds. Ottomar Anschütz
was inspired to make the only daylight photograph of
a fl ying cannonshell in 1888, using specially designed
weighted, pneumatically driven and electrically released
focal plane shutters that operated at 76 millionths
of a second at the Krupp Gruson works at Buckau-
Magdeburg. Sir Charles Vernon Boys, who had made
photographs of falling drops of water and other liquids
by moving a photographic plate by hand through a
camera while a slotted rotating disk shutter ran in front
of his camera lens in the late 1880s, repeated Mach’s
Schlieren-method work in 1891 and 1892, producing
photographs of bullets piercing a sheet of glass and
other materials. Unusually, Boys used no lens in his
camera, relying instead on the nearness of the bullet to
the plate and his own improvements in the design of the
electrical release mechanism, which much improved
the briefness of his spark, to produce a defi ned image.
Helmut Gernsheim’s dismissive comment on the work
of Mach and Boys, based on the fact that because the
subjects were back-lit from behind the Schlieren Head
the photographs produced only shadows of the passing
object, seems today distinctly ungenerous. Their in-
novative technical expansion of the usefulness of pho-
tography not only led to specifi c scientifi c discoveries,
but also gave new impetus to the fi eld of electric-spark
photography pioneered by Prof. Bernhard Wilhelm
Feddersen in the late 1850s, and ultimately led to the
striking images of Harold Edgerton at MIT in the 1930s
and the development of modern stroboscopic fl ash units
both large and small.
Deac RossellBiography
Born at Turas, Moravia (today Czech Republic), Ernst
Mach was educated at the University of Vienna, gaining
his PhD in 1860. Four years later he was named profes-
sor of mathematics at Graz, and next took the chair of
physics at the University of Prague in 1867, where he
remained for the next 28 years. At Prague, Mach con-
centrated on experiments in psychology and perception,
and worked on optics, mechanics and wave dynamics.
He discovered the function of the semicircular canals of
the ear; a phenomenon of the eye where it sees bright or
dark bands near the boundaries between areas of starkly
constrasting illumination, still called Mach’s Bands; and
fi rst described the shock waves in the air that precede an
object travelling faster than the speed of sound, leading
to the colloquial expression of “Mach I” or “Mach II” for
the speed of military and experimental aircraft. This last
discovery was made in a series of trials using advanced
photographic methods. Parallel with his experimental
work in the 1880s, Mach proposed that all knowledge
is derived from physical sensations, and began to argue
for a rigorous interpretation of science based only on
the interpretation of verifi able empirical observation.
He further developed a radical concept of inertia, which
he considered was exclusively a function of the interac-
tion between one body and all the other bodies in the
universe, a view which was not only controversial but
which was one of the inspirations for Einstein’s theory
of relativity. His rejection of the existence of atoms,
and his contention that matter was constructed wholly
out of pure sensation was equally infl uential on the
logical positivist philosophers, and embroiled him in
vivid public disputes with Max Planck, Oswald Külpe,
and even Vladimir Lenin. Mach’s scientifi c legacy is
principally as a philosopher of science although he al-
ways considered himself nothing other than a rigorous
physicist. Moving to the University of Vienna in 1895,
where he became professor of the history and theory
of the inductive sciences, Mach began an intense battle
against Einstein’s theory of relativity which dominated
his later work, even though he was partially paralysed
by a stroke in 1901. Widely infl uential on European
physics practitioners during his lifetime, his fi ght with
Einstein ultimately eclipsed his reputation until recently,