As a scientist, Leonardo had no formal education in Latin and mathematics and did not attend a university. Because of these factors, his scientific studies were largely ignored by other scholars.

Leonardo's approach to science was one of intense observation and detailed recording, his tools of investigation being almost exclusively his eyes.

Although Leonardo's training was primarily as an artist, it was largely through his scientific approach to the art of painting, and his development of a style that coupled his scientific knowledge with his unique ability to render what he saw that created the outstanding masterpieces of art for which he is famous.

His journals give insight into his investigative processes.
Leonardo kept a series of journals in which he wrote almost daily, as well as separate notes and sheets of observations, comments and plans which were left to various pupils and were later bound. Many of the journals have survived to illustrate Leonardo's studies, discoveries and inventions. Most of the journals were written backwards in mirror script.

Leonardo da Vinci is famous for having written most of his personal notes in mirror, only using standard writing if he intended his texts to be read by others.
There are two popular theories on why he did this.
Leonardo da Vinci was left-handed, causing the ink to smudge easily if he wrote in standard writing. He may also have wanted to protect his ideas from theft or hide them from the Roman Catholic Church (with whom his scientific findings sometimes collided). However, the latter idea, popular among conspiracy theorists, is highly unlikely: it is (and was even at the time) clear, even to a child, that the text in question could be easily read "backwards" (either directly or through its reflection, such as in a mirror). The true purpose of this practice thus remains unknown.
A third theory is that he taught himself to write: given the propensity of children to start writing from the bottom right hand corner of a page[citation needed], this would have led him to produce mirror writing.
Related readings:mirror script

His journals were later published, 165 years after his death.

Natural Science

For an artist working in the 15th century, some study of the nature of light was essential.
It was by the effective painting of light falling on a surface that modeling, or a three dimensional appearance was to be achieved in a two-dimensional medium.
It was also well understood by artists like Leonardo's teacher, Verrocchio, that an appearance of space and distance could be achieved in a background landscape by painting in tones that were less in contrast and colors that were less bright than in the foreground of the painting.

The effects of light on solids were achieved by trial and error, few artists except Piero della Francesca, having accurate scientific knowledge of the subject.
In the painting generally titled The Lady with an Ermine (about 1483) he sets the figure diagonally to the picture space and turns her head so that her face is almost parallel to her nearer shoulder. The back of her head and the further shoulder are deeply shadowed. Around the ovoid solid of her head and across her breast and hand the light is diffused in such a way that the distance and position of the light in relation to the figure can be calculated.

Medicine

As a student he would have been taught to draw the human body from life, to memorize the muscles, tendons and visible subcutaneous structure and to familiarize himself with the mechanics of the various parts of the skeletal and muscular structure. It was common workshop practice to have plaster casts of parts of the human anatomy available for students to study and draw.

 

Leonardo not only studied human anatomy, but the anatomy of many other animals as well. He dissected cows, birds, monkeys and frogs, comparing in his drawings their anatomical structure with that of humans. On one page of his journal Leonardo drew five profile studies of a horse with its teeth bared in anger and, for comparison, a snarling lion and a snarling man.

Leonardo painted the torso (still disputed) and arms of Christ in The Baptism of Christ on which he famously collaborated with his master Verrocchio, then his understanding of topographical anatomy had surpassed that of his master at an early age as can be seen by a comparison of the arms of Christ with those of John the Baptist in the same painting.
In the 1490s he wrote about demonstrating muscles and sinews to students: "Remember that to be certain of the point of origin of any muscle, you must pull the sinew from which the muscle springs in such a way as to see that muscle move, and where it is attached to the ligaments of the bone".
He disproved the belief that the heart was not a muscle and showed it consists of four chambers and not two, as was commonly held He suggested that arteries fur up over a lifetime, creating a health risk

Engineering and invention

Da Vinci utilized leverage and cantilevering, pulleys, cranks, gears, including angle gears and rack and pinion gears; parallel linkage, momentum, centripetal force and the aero foil.

 

 

Leonardo's inventions date from an era before the issue of patents, it is impossible to say with any certainty how many or even which of his inventions passed into general and practical use, and thereby had impact over the lives of many people. Among those inventions that are credited with passing into general practical use are the strut bridge, the automated bobbin winder, the machine for testing the tensile strength of wire and the lens-grinding machine pictured at right.
Leonardo's study of the motion of water led him to design machinery that utilized its force.

In 1502, Leonardo produced a drawing of a single span 240 m (720 ft) bridge as part of a civil engineering project for Ottoman Sultan Beyazid II of Istanbul. The bridge was intended to span an inlet at the mouth of the Bosphorus known as the Golden Horn. Beyazid did not pursue the project, because he believed that such a construction was impossible. Leonardo's vision was resurrected in 2001 when a smaller bridge based on his design was constructed in Norway. On 17 May 2006, the Turkish government decided to construct Leonardo's bridge to span the Golden Horn.

War Machines

Leonardo's notebooks there is an array of war machines which includes a tank to be propelled by two men powering crank shafts. Although the drawing itself looks quite finished, the mechanics were apparently not fully developed because, if built as drawn, the tank, with a lot of effort, might be made to rotate on the spot, but would never progress in a forward direction.
Another machine, propelled by horses with a pillion rider, carries in front of it four scythes mounted on a revolving gear, turned by a shaft driven by the wheels of a cart behind the horses.

 

Helicopter and Flying Machine

The desire to fly is expressed in the many studies and drawings. His later journals contain a detailed study of the flight of birds and several different designs for wings based in structure upon those of bats which he described as being less heavy because of the impenetrable nature of the membrane. There is a legend that Leonardo tested the flying machine with one of his apprentices, and that the apprentice fell and broke his leg. Experts Martin Kemp and Liana Bortolon agree that there is no evidence of such a test, which mentioned in his journals.
One design that he produced shows a helicopter to be lifted by a rotor powered by four men. It would not have worked since the body of the craft itself would have rotated in the opposite direction to the rotor.

There have been many projects which have sought to turn diagrams on paper into working models. One of the factors is the awareness that, although in the 15th and 16th centuries Leonardo had available a limited range of materials, modern technological advancements have made available a number of robust materials of light-weight which might turn Leonardo's dreams into reality. This is particularly the case with his designs for flying machines.

 

Credits and related readings.
-*-http://en.wikipedia.org/wiki/
-*-Moon, Francis C. (2007). The Machines of Leonardo Da Vinci and Franz Reuleaux, Kinematics of Machines from the Renaissance to the 20th Century. Springer.

-*-http://news.bbc.co.uk/2/hi/health/4289204.stm
-*-ttp://www.pbs.org/treasuresoftheworld/index.htmll
-*-http://dsc.discovery.com/tv/doing-davinci/doing-davinci.html
-*-http://en.wikipedia.org/wiki/Mirror_writing