LEONARDO DA VINCI (1452-1519)

1502 – Florence, Italy

‘In the Renaissance science was reinvented’

Image of the VITRUVIAN MAN

VITRUVIAN MAN

Leonardo is celebrated as the Renaissance artist who created the masterpieces ‘The Last Supper’ (1495-97) and ‘The Mona Lisa’ (1503-06). Much of his time was spent in scientific enquiry, although most of his work remained unpublished and largely forgotten centuries after his death. The genius of his designs so far outstripped contemporary technology that they were rendered literally inconceivable.

The range of his studies included astronomy, geography, palaeontology, geology, botany, zoölogy, hydrodynamics, optics, aerodynamics and anatomy. In the latter field he undertook a number of human dissections, largely on stolen corpses, to make detailed sketches of the body. He also dissected bears, cows, frogs, monkeys and birds to compare their anatomy with that of humans.

It is perhaps in his study of muscles where Leonardo’s blend of artistry and scientific analysis is best seen. In order to display the layers of the body, he developed the drawing technique of cross-sections and illustrated three-dimensional arrays of muscles and organs from different perspectives.

Leonardo’s superlative skill in illustration and his obsession with accuracy made his anatomical drawings the finest the world had ever seen. One of Leonardo’s special interests was the eye and he was fascinated by how the eye and brain worked together. He was probably the first anatomist to see how the optic nerve leaves the back of the eye and connects to the brain. He was probably the first, too, to realise how nerves link the brain to muscles. There had been no such idea in GALEN’s anatomy.

Possibly the most important contribution Leonardo made to science was the method of his enquiry, introducing a rational, systematic approach to the study of nature after a thousand years of superstition. He would begin by setting himself straightforward scientific queries such as ‘how does a bird fly?’ He would observe his subject in its natural environment, make notes on its behaviour, then repeat the observation over and over to ensure accuracy, before making sketches and ultimately drawing conclusions. In many instances he would directly apply the results of his enquiries into nature to designs for inventions for human use.

Self portrait of LEONARDO DA VINCI

LEONARDO DA VINCI

He wrote ‘Things of the mind left untested by the senses are useless’. This methodical approach to science marks a significant stepping-stone from the DARK AGES to the modern era.

1469 Leonardo apprenticed to the studio of Andrea Verrocchio in Florence

1482 -1499 Leonardo’s work for Ludovico Siorza, the Duke of Milan, included designs for weaponry such as catapults and missiles.
Pictor et iggeniarius ducalis ( painter and engineer of the Duke )’.
Work on architecture, military and hydraulic engineering, flying machines and anatomy.

1502 Returns to Florence to work for Pope Alexander VI’s son, Cesare Borgia, as his military engineer and architect.

1503 Begins to paint the ‘Mona Lisa’.

1505-07 Wrote about the flight of birds and filled his notebooks with ideas for flying machines, including a helicopter and a parachute. In drawing machines he was keen to show how individual components worked.

1508 Studies anatomy in Milan.

1509 Draws maps and geological surveys of Lombardy and Lake Isea.

1516 Journeys to France on invitation of Francis I.

1519 April 23 – Dies in Clos-Luce, near Amboise, France.

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CHARLES LYELL (1787-1875)

1850 – UK

‘An Attempt to explain the Former Changes of the Earth’s Surface by Reference to Causes Now in Operation’

Portrait of CHARLES LYELL

At the start of the nineteenth century, most people believed that a few major events had shaped the Earth, one of which was Noah’s great biblical flood. In between these catastrophic events the Earth had remained unchanged.

Charles Lyell replaced catastrophe theory with uniformitarianism, which proposed that the Earth changed gradually as constantly present forces acted upon it. He attributed ages to rock strata, by looking at the fossils they contained. This introduced a way of studying the Earth and led to modern geology. Lyell started a chain of thought that has now generated a complex understanding of the Earth’s history, allowing it to be divided into discrete eons, eras, periods and epochs.

There is evidence that Darwin was influenced by Lyell, although Lyell was deeply troubled by Darwin’s concept of natural selection. Darwin wrote “The greatest merit of the Principles (of Geology) was that it altered the whole tone of one’s mind, and therefore that, when seeing a thing never seen by Lyell, one yet saw it through his eyes.”

Lyell believed that geological, and therefore biological, history was cyclical. While Lyell destroyed one major dogma, his adherence to other ideas prevented geology moving forward.

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Geological evolution – Charles Lyell

CHARLES DARWIN (1809- 82)

1859 – England

‘All present day species have evolved from simpler forms of life through a process of natural selection’

Portrait of Charles Darwin ©

Organisms have changed over time and the ones living today are different from the ones that lived in the past. Furthermore, many organisms that once lived are now extinct.

The orthodox view was that of the Creationists. According to the Book of Genesis in the Bible, ‘God created every living creature that moves….’. Against this background, thinkers such as French naturalist Jean-Baptist Lamarck developed a picture of how species evolved from single-celled organisms.

Darwin’s breakthrough was to work out what evolution is and how it happens. His insight was to focus on individuals, not species and to show how individuals evolve by natural selection. The mechanism explained how all species evolved to become well suited to their environment. Later commentators have characterized this idea as ‘survival of the fittest,’ but this was never a phrase that Darwin himself used.

Darwin was influenced by CHARLES LYELL’s newly published book ‘Principles of Geology’, showing how landscapes had evolved gradually through long cycles of erosion and upheaval and by ‘An Essay on the Principle of Population’ written in 1798 by THOMAS MALTHUS.

The publication of Darwin’s book ‘On the Origin of Species by Means of Natural Selection’ in 1859 generated social and political debate that continues to this day. Darwin did not discuss the evolution of humans in this book.
In ‘The Descent of Man’, published in 1871, he presented his explanation of how his theory of evolution applied to the idea that humans evolved from apes. In modern form the theory contains the following ideas:

  • members of a species vary in form and behaviour and some of this variation has an inherited basis

  • every species produces far more offspring than the environment can support

  • some individuals are better adapted for survival in a given environment than others

this means that there are variations within each population gene pool and individuals with most favourable variations stand a better chance of survival – the survival of the fittest.

  • the favourable characteristics show up among more individuals of the next generation

there is thus a ‘natural selection’ for those individuals whose variations make them better adapted for survival and reproduction.

  • the natural selection of strains of organisms favours the evolution of new species, through better adaptation to their environment, as a consequence of genetic change or mutation.

Knowledge of DNA has enriched the theory of evolution. The modern view is still based on the Darwinian foundation; evolution through natural selection is opportunistic and it takes place steadily.

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ALFRED LOTHAR WEGENER (1880-1930)

1915 – Germany

‘Continental land masses are constantly in motion. The Earth’s land surface was once one big super-continent. About 250 million years ago it broke up into the continents we know today, which have since drifted to their present positions’

Photograph of ALFRED WEGENER ©

ALFRED WEGENER

Wegener proposed that the continental land masses are moving over the face of the Earth.
Rock under the ocean is principally Basalt, a denser rock than the Granite that makes up the continents. At the start of the Earth’s history there was just a single landmass, which began to break up 200 million years ago, and the parts are still moving. Mountain ranges have been produced where one moving land mass crashes into another, pushing rocks together and forcing them upwards in folds. The tectonic plates move over the asthenosphere carried by convection currents in the magma below.

Up until and beyond Wegener’s death his ideas had little scientific credence – until in the 1950s the mid-Atlantic ridge was discovered. It was this discovery that led to the concept of the tectonic plates.

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CHARLES RICHTER (1900- 85)

1935 – USA

‘A scale ranging from 0 to 9 to measure the magnitude of earthquakes’

photo of CHARLES RICHTER who devised a scale for measuring the magnitude of earthquakes ©

CHARLES RICHTER

The Richter scale is a numerical scale that gives the magnitude of an earthquake by calculating the energy of shock waves at a standard distance. The scale is logarithmic, so each additional point represents a tenfold increase in severity. Thus a magnitude 7.0 earthquake is 10 times as powerful as one of magnitude 6.0 and 100 times as powerful as one of magnitude 5.0.
In terms of energy, one unit represents an increase in the energy of roughly 3 times. A magnitude 7.0 earthquake unleashes about 1000 times the energy released by a magnitude 5.0 earthquake.

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