Francesco Siacci
Encyclopedia
Francesco Siacci an Italian
mathematician
, ballistician
, and officer in the Italian army
, was born in Rome
, Italy
. He was a professor of mechanics
in the University of Turin
and University of Naples. He is best known for his contributions to the field of exterior ballistics
.
. In 1861, he moved to Turin and enlisted in the army amidst the period of Italian unification
. He also became a professor of mechanics at the Military Academy. He remained there until war broke out in Italy in 1866.
Siacci was briefly part of the campaign against the Austrians
in a war in 1866, until he was sent back to Turin to teach ballistics at the Military Academy. In 1871, he began teaching mechanics in the University of Turin
. A year later, he was promoted to Professor of Ballistics at the School of Applied Artillery and Engineering in Turin and held that post until his retirement from the army as a major general
in 1892. In 1875, he became a Professor of Higher Mechanics in the University of Turin.
After two terms as a deputy in 1892, Siacci was appointed as a senator in Rome
in 1893. Since Turin is far from Rome, he requested a transfer to the University of Naples
to capably serve as senator and still teach. Consequently, Vito Volterra
took over his vacated position in Turin, but Siacci retained an honorary professorship there. Siacci stayed to teach in Naples for the rest of his life.
Siacci was a member of the most important national academies in Italy, including the Accademia dei Lincei
(corresponding member in 1872, full member in 1890), the Accademia Nazionale delle Scienze detta dei XL
, the Accademia delle Scienze in Turin, and the Accademia delle Scienze Fisiche e Matematiche in Naples.
A street in Rome, the Via Francesco Siacci, is named after him.
, distinguishing himself with a famous treatise Balistica, published in 1888 and translated to French in 1891. Of great importance is an approximation method he devised to calculate bullet trajectories of small departure angles. Known as Siacci’s method, it was a major innovation in exterior ballistics
and was widely used almost exclusively at the beginning of World War I. Several modifications of the method are still in use today, including those of H.P. Hitchcock and R.H. Kent, and James Ingalls
. Siacci also studied theoretical mechanics (Siacci’s theorem
, rigid body dynamics
, canonical transformations
, and inverse problems
) and mathematics (theory of conic sections
, Riccati differential equation
, etc.).
in dynamics
is the resolution of the acceleration
vector of a particle into radial and tangential components, which are generally not perpendicular to one another. Siacci formulated this decomposition in two papers which were published in 1879, the first for planar motions, and the second for spatial motions. The theorem is useful in situations where angular momentum
is constant (for example, in central forces).
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
mathematician
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
, ballistician
Ballistics
Ballistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.A ballistic body is a body which is...
, and officer in the Italian army
Italian Army
The Italian Army is the ground defence force of the Italian Armed Forces. It is all-volunteer force of active-duty personnel, numbering 108,355 in 2010. Its best-known combat vehicles are the Dardo infantry fighting vehicle, the Centauro tank destroyer and the Ariete tank, and among its aircraft...
, was born in Rome
Rome
Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
. He was a professor of mechanics
Mechanics
Mechanics is the branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment....
in the University of Turin
University of Turin
The University of Turin is a university in the city of Turin in the Piedmont region of north-western Italy...
and University of Naples. He is best known for his contributions to the field of exterior ballistics
External ballistics
External ballistics is the part of the science of ballistics that deals with the behaviour of a non-powered projectile in flight. External ballistics is frequently associated with firearms, and deals with the behaviour of the bullet after it exits the barrel and before it hits the target.-Forces...
.
Biography
Siacci graduated from the University of Rome in 1860 and received an honorary degree in mathematicsMathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
. In 1861, he moved to Turin and enlisted in the army amidst the period of Italian unification
Italian unification
Italian unification was the political and social movement that agglomerated different states of the Italian peninsula into the single state of Italy in the 19th century...
. He also became a professor of mechanics at the Military Academy. He remained there until war broke out in Italy in 1866.
Siacci was briefly part of the campaign against the Austrians
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
in a war in 1866, until he was sent back to Turin to teach ballistics at the Military Academy. In 1871, he began teaching mechanics in the University of Turin
University of Turin
The University of Turin is a university in the city of Turin in the Piedmont region of north-western Italy...
. A year later, he was promoted to Professor of Ballistics at the School of Applied Artillery and Engineering in Turin and held that post until his retirement from the army as a major general
Major General
Major general or major-general is a military rank used in many countries. It is derived from the older rank of sergeant major general. A major general is a high-ranking officer, normally subordinate to the rank of lieutenant general and senior to the ranks of brigadier and brigadier general...
in 1892. In 1875, he became a Professor of Higher Mechanics in the University of Turin.
After two terms as a deputy in 1892, Siacci was appointed as a senator in Rome
Italian Senate
The Senate of the Republic is the upper house of the Italian Parliament. It was established in its current form on 8 May 1948, but previously existed during the Kingdom of Italy as Senato del Regno , itself a continuation of the Senato Subalpino of Sardinia-Piedmont established on 8 May 1848...
in 1893. Since Turin is far from Rome, he requested a transfer to the University of Naples
University of Naples Federico II
The University of Naples Federico II is a university located in Naples, Italy. It was founded in 1224 and is organized into 13 faculties. It is the world's oldest state university and one of the oldest academic institutions in continuous operation...
to capably serve as senator and still teach. Consequently, Vito Volterra
Vito Volterra
Vito Volterra was an Italian mathematician and physicist, known for his contributions to mathematical biology and integral equations....
took over his vacated position in Turin, but Siacci retained an honorary professorship there. Siacci stayed to teach in Naples for the rest of his life.
Siacci was a member of the most important national academies in Italy, including the Accademia dei Lincei
Accademia dei Lincei
The Accademia dei Lincei, , is an Italian science academy, located at the Palazzo Corsini on the Via della Lungara in Rome, Italy....
(corresponding member in 1872, full member in 1890), the Accademia Nazionale delle Scienze detta dei XL
Accademia nazionale delle scienze
The Accademia Nazionale delle Scienze, or more formally L’Accademia Nazionale delle Scienze detta dei XL, is Italy's national academy of science. Its offices are located within the Villino Rosso, at the corner of via L...
, the Accademia delle Scienze in Turin, and the Accademia delle Scienze Fisiche e Matematiche in Naples.
A street in Rome, the Via Francesco Siacci, is named after him.
Exterior ballistics
Siacci is well known for his contributions in the field of ballisticsBallistics
Ballistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.A ballistic body is a body which is...
, distinguishing himself with a famous treatise Balistica, published in 1888 and translated to French in 1891. Of great importance is an approximation method he devised to calculate bullet trajectories of small departure angles. Known as Siacci’s method, it was a major innovation in exterior ballistics
External ballistics
External ballistics is the part of the science of ballistics that deals with the behaviour of a non-powered projectile in flight. External ballistics is frequently associated with firearms, and deals with the behaviour of the bullet after it exits the barrel and before it hits the target.-Forces...
and was widely used almost exclusively at the beginning of World War I. Several modifications of the method are still in use today, including those of H.P. Hitchcock and R.H. Kent, and James Ingalls
James Monroe Ingalls
James Monroe Ingalls was an American soldier and an authority on ballistics. His ballistic tables were the authoritative source for over 100 years.-Biography:...
. Siacci also studied theoretical mechanics (Siacci’s theorem
Siacci's theorem
In dynamics, the acceleration of a particle moving along a curve in space is the time derivative of its velocity. In most applications, the acceleration vector is expressed as the sum of its normal and tangential components, which are orthogonal to each other...
, rigid body dynamics
Rigid body dynamics
In physics, rigid body dynamics is the study of the motion of rigid bodies. Unlike particles, which move only in three degrees of freedom , rigid bodies occupy space and have geometrical properties, such as a center of mass, moments of inertia, etc., that characterize motion in six degrees of...
, canonical transformations
Canonical transformation
In Hamiltonian mechanics, a canonical transformation is a change of canonical coordinates → that preserves the form of Hamilton's equations , although it...
, and inverse problems
Inverse problem
An inverse problem is a general framework that is used to convert observed measurements into information about a physical object or system that we are interested in...
) and mathematics (theory of conic sections
Conic section
In mathematics, a conic section is a curve obtained by intersecting a cone with a plane. In analytic geometry, a conic may be defined as a plane algebraic curve of degree 2...
, Riccati differential equation
Riccati equation
In mathematics, a Riccati equation is any ordinary differential equation that is quadratic in the unknown function. In other words, it is an equation of the form y' = q_0 + q_1 \, y + q_2 \, y^2...
, etc.).
Siacci's theorem
Siacci's theoremSiacci's theorem
In dynamics, the acceleration of a particle moving along a curve in space is the time derivative of its velocity. In most applications, the acceleration vector is expressed as the sum of its normal and tangential components, which are orthogonal to each other...
in dynamics
Dynamics (mechanics)
In the field of physics, the study of the causes of motion and changes in motion is dynamics. In other words the study of forces and why objects are in motion. Dynamics includes the study of the effect of torques on motion...
is the resolution of the acceleration
Acceleration
In physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ...
vector of a particle into radial and tangential components, which are generally not perpendicular to one another. Siacci formulated this decomposition in two papers which were published in 1879, the first for planar motions, and the second for spatial motions. The theorem is useful in situations where angular momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...
is constant (for example, in central forces).