Galileo Galilei1564-1642

From Spyglasses to Space Telescopes

orA Saga That Began With Galileo

Galileo was…….

• An inventor

• Father of Experimental Physics

• Father of Modern Astronomy

Born: 15 Feb 1564Pisa

Professor of MathematicsUniversity of Padua1592-1610

1610: Chief Mathematician to Grand Duke of TuscanyCosimo II de Medici

Development of Telescope

is linked to that of spectacles

With age, the eye progressively loses its power to accommodate, that is to change its focus from faraway objects to nearby ones. This condition, becomes noticeable for most people in their forties, when they can no longer focus on letters/ books held at a comfortable distance from the eye. Magnifying glasses became common in the thirteenth century for reading

Lipperhey (or Lippershey!) was a spectacle maker in Holland. One story behind the creation of the telescope states that two children were playing with lenses in his shop. The children discovered that images were clearer when seen through two lenses, one in front of the other. Lipperhey was inspired by this and created a device very similar to today's telescope.

Lipperhey (or Lippershey!)

In 1608, Lipperhey found that while viewing a distant object through combination of a convex and a concave lens, the object appeared closer and magnified. For this purpose, however, the two lenses had to be placed at just the right distance from each other.

Lipperhey never used his telescope to look at the stars. He believed that his new invention would mainly benefit seafarers and soldiers - and for spying purposes.

This is how the telescope was born - in the garb of a spyglass!

Significance of Galileo• He did not just ‘use’ the telescope -

he fabricated his own …

• He did not just ‘see’ the heavens, but applied scientific method to interpret what he saw…

The actual term "telescope" was coined on April 14, 1611 by Prince Frederick Cesi at a reception where Galileo was demonstrating one of his instruments.

Galileo’s telescope

Galileo found out about this invention in the early 1609 and immediately set about improving it.

•He realized that the magnification was proportional to the ratio of the power of the concave (eyepiece) lens to the convex (more distant) lens. •In other words he needed a weak convex lens and a strong concave lens. • Opticians only made glasses in a narrow range of strengths, and three or so was the best magnification available with off the shelf lenses.

Galileo learned to grind his own lenses, and by August 1609, he had achieved about eight-fold linear magnification. He demonstrated his new invention to a gathering of officials on August 1609.

Galilean TelescopeGalileo used a long focal length objective and a short focal length eye piece. If the focal length of the objective is Fo and the focal length of the eyelens is -Fe, the distance between them must be Fo - Fe, and the power (angular magnification) is Fo/Fe. Image is upright.

"When there are no glasses in the tube, the rays proceed to the object FG along the straight lines ECF and EDG, but with the glasses put in they proceed along the refracted lines ECH and EDI. They are indeed squeezed together and where before, free, they were directed to the object FG, now they only grasp the part HI"

His initial version had magnification of 8x but was soon refined to the 20x

Galileo begins a revolution..

He then turned his telescope to the Heavens…

January 19, 1610 stellar occultation

Galileo could see stellar occultation, mountains on Moon, and so on. At one stroke he could change the way the Moon looked.

He observed that some parts of the Moon were illuminated well before its surroundings by the sunlight. We know that mountain tops are illuminated at the dawn well before the valleys. He built a convincing case for the reality of the mountains by sketching the appearance of parts of the Moon’s surface at different times of the month, that is, under different angles of lighting. Obviously this caused an uproar. The orthodox were enraged, how can Galileo claim that Moon, an celestial body to be ‘imperfect’ ?!

Sun is blemished, changing, and rotating

Galilean Moons

Galileo’s next major discovery began with his observation on January 7, 1610, of what he took to be a rather odd set of three small fixed stars near Jupiter. These ‘stars’ were invisible to the naked eye. Observations over successive night revealed that actually four star-like objects in a line with it. The objects moved from night to night, sometimes disappearing behind or in front of the planet. Galileo correctly inferred that these objects were moons of Jupiter and orbited it just as our Moon orbits Earth. By the 15th January 1610 had realized that he was looking at moons of Jupiter.

Galileo then turned his attention to most numerous objects in the night sky- stars. Rather to his disappointment the stars showed no features- they were still point source, even through a telescope the stars still appeared as points of light. Galileo suggested that this was due to their immense distance from Earth. On turning his telescope to the band of the Milky Way Galileo saw it resolved into thousands of hitherto unseen stars. In like manner when ex explored the region of Pleiades, he found stars that were unseen to naked eye. His exploration of the Orion nebula also revealed unseen stars.

Through naked eye Through telescope

Galileo Galilei published Sidereus Nuncius, or the 'Starry Messenger ' in March 1610. In it he provided a lively and accessible account of his telescopic observations. This revolutionized the astronomy – in fact all the sciences.

Galileo’s drawing of the phases of Venus and modern photo-mosaic

Copernicus

Ptolemy

Observation of the phases of Venus helped establish the heliocentric theory on a firm footing.

His telescopic observation of Saturn resulted in total shock. Initially Saturn appeared to have ears, and latter some kind of appendage. Galileo could not make sense of it.

Few decades later, Huygens using a better telescope resolved it as a ring around Saturn.

In any case Galileo’s observation showed that stellar objects need not be perfect sphere.

Galileo's extensive telescopic observations of the heavens made it more and more plausible that they were not made from a perfect, unchanging substance. In particular, Galileo's observational confirmation of the Copernican hypothesis suggested that the Earth was just another planet, so maybe it was made from the same material as the other planets.

It was radical and an epistemic rupture of celestial and terrestrial.

Same laws of physics applied in both cases. One set of science is all that is required to explain ‘heaven and Earth’!

Just as Aryabhata was condemned for his views against the purnaic myth of Rahu - Ketu, Galileo was punished by the orthodoxy in Europe for daring to put forth his theories. He was to suffer for many years for upholding science and spirit of quest against mindless dogmas.

In July 1633, he was imprisoned and latter his sentence was converted into life-long house arrest, because of health reasons. He was not allowed to have contact with the outside world. Until his death, even at his old age he kept working.

Although Galileo was ill and mentally exhausted, he started to write a book about mechanics, based on his research in Padua. This book, Discorsi, or Dialogues Concerning Two New Sciences was published by Elzevier in Leiden, because it could, of course, not be published in Catholic lands. The book convincingly argued against the Earth-centered universe and upheld the scientific spirit. No wonder the 400th annivesary of Galileo’s use of telescope is celebrated as International Year of Astronomy.

Down but not Out

JOHANNES KEPLER

1571 to 1630

A useful resource:http://kepler.nasa.gov/johannes

Born: 27 Dec 1571Weil der Stadt

1594-1600: Teacher of astronomy & mathematics at the Protestant School in Graz

1600: Meets Tycho Brahe; 1601: Imperial Mathematicus

Astronomy

Optics

The last scientific astrologer

Mathematics: logarithms, calculus

Kepler published First two Laws of Planetary Motion in 1609 – A Fact not much publicized!

This too exactly 400 years ago!

It’s the Law!

Planetary orbits are ellipses, with the Sun at one focus.

Planets sweep out equal areas in equal times

1619: Third Law of Planetary Motion1618: 3rd Law of Planetary Motion

Kepler's Third Law quantifies the observation that more distant orbits have longer periods:

a 3 = P 2

Here, the semimajor axis a is measured in A.U. and the orbital period P is measured in years.

1618: 3rd Law of Planetary Motion

P2 = a3

Standing on the shoulders of Johannes Kepler,through the analysis of Kepler’s Laws of Planetary Motion, Isaac Newton discovered the Law of Universal Gravitation.

Issac Newton built a telescope from mirrors, not lenses

Reflecting telescopes solved the problem of colored images obtained with lenses, and other problems as well!

Reflecting Telescope: Schematic Diagram

A telescope in which light from the object is gathered and focused by a concave mirror, with the resulting image magnified by the eyepiece.

A concave mirror reflects the light and brings it to a focus to form a small inverted image

In both, refracting and reflecting telescopes, image formed will be inverted, but this can be re-inverted by using extra lens. But this would not be required in astronomical telescopes.

Recording what we see

Photographic film: in 1850, the first permanent images recorded, but wet emulsions were very slow, and long exposures were needed

“dry” emulsions made astrophotography much easier!

Which ushers us into the

modern era…

First image of the Moon, 1852

Telescopes are light buckets!

The greater the diameter of the lens or mirror, the more light it collects - and the fainter the object we can see

Stars seen with larger and larger telescopes

An older Refracting Telescope

The 0.9 meter Lick Refractor on Mt. Hamilton, CA

versus a 35 year old reflecting telescope

The 4 meter telescope at Kitt Peak

versus a very modern and large Reflecting Telescope

The 8 meter Gemini North telescope at Mauna Kea

• The largest single telescope for visible and infrared light in the world today is the Great Canary Telescope situated at La Palma, Canary Islands, with the main mirror 10.4 m (410 inches) in diameter.

Asia’s largest telescope of 2.34 meter diameter

It is located at 175 km away from Bangalore, at Kavalur in TN

Vainu Bappu TelescopeIt is operated by Indian Institute of Astrophysics

Observing nights are comparatively large in number

Himalayan Chandra Telescope

World’s highest telescope(4.5km) located at Hanle in J & K

Telescope works in optical and Near Infrared region of EMR

It is remotely operated by Indian Institute of Astrophysics

Aperture is 2 metres with Alt-azimuth mount

Located at the height of about 1680 m and located at Mt Abu (Rajasthan)

Telescope works in near- infrared and optical regions.

It is operated by Physical Research Laboratory, Ahmedabad

Aperture is 1.2 m. Operating since 1994.

Gurushikhar Telescope

Undoubtedly…

Telescope is a striking example of how technology could help push the frontiers of science further ahead; and help improve our understanding of the natural phenomena.

13 March 1781 Uranus was discovered by William Hershel and his sister Carolina.

Discoveries with telescopes from the 1600s through the 1800s laid the foundations for modern astronomy.

Neptune was discovered by Adams and Leverrier by mathematically calculating where it should be from the gravitational perturbation it caused on the path of Uranus.

It was discovered in 1846. Thus it has not even completed one round about sun since its discovery.

Next, the asteroids between the orbits of Mars and Jupiter were discovered. Between the orbit of Mars and Jupiter there are numerous space rocks of varying sizes. These together are called asteroids or minor planets.

Asteroids are composed of rocks and boulders bound together due to gravity and the surface is covered with fine dust

Newton’s colleague Edmond Halley used the new theory of gravitation to calculate the orbits of comets. Based on his calculations, he predicted that this comet would return in about 1758. Although Halley had died by 1758, when the comet did indeed appear as he had predicted it was given the name Halley’s Comet.

Halley did not live to see Venus transits in his lifetime, but, his efforts gave rise to many expeditions in 1761 and 1769 to observe the transits of Venus which gave astronomers their first good value for the Sun’s distance from Earth, that is, The Astronomical Unit (AU).

The Astronomical Unit

Pluto was discovered by American astronomer Clyde Tombaugh in 1930. Pluto (which was formerly classified as a planet, then a dwarf planet, and yet again classified as plutoid) has not yet been visited by a spacecraft. A spacecraft launched in 2006 is expected to rendezvous with Pluto in 2015.

Telescopic studies of double stars, also known as binary star systems, provided the evidence that gravity is truly universal and that the same physical processes that we can study here on Earth can be applied to studies of distant objects, including stars. Observation through telescopes in 1838 helped measure distances to stars.

Hubble image of the Sirius binary system, in which Sirius B can be clearly distinguished (lower left).

In 1864 British astronomer Sir William Huggins showed that the pattern of dark lines in the spectrum of a star matched the patterns produced by elements known on the Earth. This showed that the physical processes that we study here on Earth can be used to study the whole universe. Study of spectra of stars provides information about their temperatures, masses, and their motions in space.

As the 20th century began, Albert Einstein advanced his General Theory of Relativity, which fundamentally changed our understanding of gravity, and the Universe. One of the predictions of his theory was that the light should bend as it passed by a massive body like a star. In 1919, a team of astronomers led by British astronomer Sir Arthur Stanley Eddington used the occasion of a total solar eclipse to measure the deflection of starlight as it passed by the Sun and arrived at numbers that agreed with Einstein’s predictions.

Edwin Hubble’s studies of distant galaxies revealed that the universe was not static, as had been previously believed, but was expanding in size.

The second half of the 20th century was truly a golden age for astronomy. Advances in technology expanded our vision by enabling us to look at the heavens in different parts of the electromagnetic spectrum and not just restrict our observations to the visible part of the spectrum alone.

In a radio telescope, radio waves from celestial sources are reflected by a metallic surface and are brought to a focus, then sent to an electric receiver, where they can be recorded and analyzed. Radio astronomy proved to be instrumental in verifying the Big Bang theory of the origin of the Universe.

New windows on the Universe opened up with the ability to launch spacecraft. Astronomical objects not only give off radio waves and light of the kind that our eyes are sensitive to. They also emit other forms of energy ranging from high-energy gamma rays and X-rays, to infrared or heat radiation. Much of this electromagnetic radiation is absorbed by Earth’s atmosphere and hence does not reach the ground. Technology again made it possible to launch telescopes above Earth’s atmosphere to observe the astronomical objects in different types of electromagnetic radiation.

many spacecraft designed to exploit the advantages of being outside Earth’s atmosphere have been launched. The Chandra X-ray Observatory, the Spitzer Space Telescope, and the Hubble Space Telescope (HST) were particularly powerful. Turbulence in the Earth’s atmosphere blurs astronomical images. Because the Hubble Space Telescope is unaffected by this blurring, it can take extremely sharp images and has given astronomers both scientifically important and stunningly beautiful images of planets, star clusters, and galaxies.

Hubble Space Telescope

Chandra X-ray Observatory

Spitzer Space Telescope

Spacecraft have been sent to orbit all of the planets. Pluto (which was formerly classified as a planet, then a dwarf planet, and yet again classified as plutoid) has not yet been visited by a spacecraft.

New Horizons to Pluto launched in 2006. To visit in 2015

India’s Moon probe Chandrayaan-1 has already entered the lunar orbit with an aim to observe it in the visible, near Infrared, low energy X-rays and high-energy X-ray regions.

India is also poised to launch Astrosat, a satellite to observe and study astronomical phenomena in 2011.

Now, we have discovered that our solar system is not the only one. Astronomers have found some 350 planets orbiting other stars. Surely, we have come a long way since Galileo observed the heavens through his tiny telescope in 1609. Now telescopes on the ground and in space explore the Universe 24 hours a day, across all wavelengths of light. Will it bring us closer to our search of life elsewhere in the Universe?

With the International Year of Astronomy 2009 (IYA 2009) we celebrate a momentous event, the first astronomical use of a telescope by Galileo, an invention that initiated 400 years of incredible astronomical discoveries; and pay homage to one of the greatest of scientists. Indeed, Galileo’s telescope triggered a scientific revolution which has profoundly affected our world view. At the same time we celebrate yet another momentous event - the publication of the first two laws of Planetary Motions by Johannes Kepler.

Galileo lived at about the same time as Kepler (they did their most important work around 1600-1610) and exchanged letters with him.

. “Pure logical thinking”, Einstein once wrote, “cannot yield us any knowledge of the empirical world; all knowledge of reality starts from experience and ends in it. Because Galileo saw this, and particularly he drummed it into the scientific world, he is the father of modern physics – indeed of modern science altogether.”

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