MAHAVIR SWAMI COLLEGE OF ENGINEERING AND TECHNOLOGY

IMAGES OF BLACK HOLES

•This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass or greater.

•A black hole is a region of spacetime from which gravity prevents anything, including light, from escaping.

• Around a black hole there is a mathematically defined surface called an event horizon that marks the point of no return.

• It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect blackbody in thermodynamics.

• Quantum field theory in curved spacetime predicts that event horizons emit radiation like a black body with a finite temperature.

PROJECT GOAL

TO KNOW ABOUT:-

THE TERM “BLACK HOLE”.

CONTRIBUTOR’S IN THE FIELD OF BLACK HOLE.

DISCOVERY & RESEARCH ABOUT BLACK HOLE.

INTRODUCTION TO CONTRIBUTOR’S

• SOME GREAT CONTRIBUTORS IN THE FIELD OF BLACK HOLE ARE AS FOLLOWS :-

• JOHN MICHELL • ALBERT EINSTEIN • STEPHEN HAWKING • HENDRIC LORENTZ • DAVID HILBERT• JULES HENRI POINCARE• KARL SCHWARZSCHILD

• & MANY OTHERS.

SELECTED CONTRIBUTOR’S IN THE FIELD OF BLACK HOLE

• 1.GEOLOGIST JOHN MICHELL (25 December 1724 – 29 April 1793)

• 2.PHYSICIST ALBERT EINSTEIN(14 March 1879 – 18 April 1955)

• 3.COSMOLOGIST STEPHEN HAWKING (born 8 January 1942)

John Michell was an English natural philosopher and geologist whose work spanned a wide range of subjects from astronomy to geology, optics, and gravitation.

He was both a theorist and an experimenter. 

Born : December 25, 1724Died : April 29, 1793Education : University of

Cambridge, Queens' College, Cambridge

1.Geologist john michell

JOHN MICHELL CONTRIBUTION

• The idea of a body so massive that even light could not escape was first put forward by geologist John Michell in a letter written to Henry Cavendish in 1783 of the Royal Society:

• If the semi-diameter of a sphere of the same density as the Sun were to exceed that of the Sun in the proportion of 500 to 1, a body falling from an infinite height towards it would have acquired at its surface greater velocity than that of light, and consequently supposing light to be attracted by the same force in proportion to its vis inertiae, with other bodies, all light emitted from such a body would be made to return towards it by its own proper gravity.

—John Michell

CONT…• In 1796, mathematician 

Pierre-Simon Laplace promoted the same idea in the first and second editions of his book Exposition du système du Monde (it was removed from later editions). 

• Such "dark stars” were largely ignored in the nineteenth century, since it was not understood how a massless wave such as light could be influenced by gravity.

Born : March 14, 1879, Ulm

Died : April 18, 1955, Princeton

Children : Hans Albert Einstein, Eduard Einstein, Lieserl Einstein,Margot Einstein, Ilse Einstein

Education : University of Zurich (1905), ETH Zurich (1901), Aargau Cantonal School (1895 – 1896), Luitpold Gymnasium

Spouse : Elsa Einstein (m. 1919–1936), Mileva Marić (m. 1903–1919)

Awards : Nobel Prize in Physics, Copley Medal, Franklin Medal

2. PHYSICIST ALBERT EINSTEINAlbert Einstein was a German-born theoretical physicist who developed

the general theory of relativity, one of the two pillars of modern physics.

•Albert Einstein’s general theory of relativity helped much in believing the existence of black holes.

•Now experts say they have shown that the theoretical phenomenon, whose gravitational pull is thought to hold galaxies together, exist "beyond any reasonable doubt".

•The team of scientists spent 16 years studying the existence of a super massive black hole thought to be at the centre of our galaxy, the Milky Way.

•While the black hole itself is invisible to the eye, the team proved its existence by tracking the motions of 28 stars circling around it.

ALBERT EINSTEIN CONTRIBUTION

CONT...

•“The stellar orbits in the galactic centre show that the central mass concentration of four million solar masses must be a black hole, beyond any reasonable doubt”.

•The astronomers were also able to measure with great accuracy how far the Earth is from the centre of the galaxy - a distance of 27,000 light years.

•While the idea of a black hole dates back as far as 1783, it was only after Einstein published his general relativity theory in 1916 that the modern concept was introduced by the German physicist Karl Scharzchild. The actual phrase black hole was not, however, coined until 1968.

3.COSMOLOGIST STEPHAN HAWKING

•Stephen William Hawking, CH, CBE, FRS, FRSA is a British theoretical physicist, cosmologist and author.

•Born : January 8, 1942 (age 71), Oxford

•Spouse : Elaine Hawking (m. 1995–2006), Jane Hawking (m. 1965–1991)

•Children : Lucy Hawking, Timothy Hawking, Robert Hawking

•Movies and TV shows : Stephen Hawking's Universe, More

•Awards : Presidential Medal of Freedom, Copley Medal, More

STEPHAN HAWKING’S CONTRIBUTIONIn 1974, Hawking showed that black holes are not entirely black but emit small amounts of thermal radiation;an effect that has become known as Hawking radiation.

By applying quantum field theory to a static black hole background, he determined that a black hole should emit particles in a perfect black body spectrum.

If Hawking's theory of black hole radiation is correct, then black holes are expected to shrink and evaporate over time because they lose mass by the emission of photons and other particles.

The temperature of this thermal spectrum (Hawking temperature) is proportional to the surface gravity of the black hole, which, for a Schwarzschild black hole, is inversely proportional to the mass.

CONT...•A stellar black hole of one solar mass has a Hawking temperature of about 100 nanokelvins.

•This is far less than the 2.7 K temperature of the cosmic microwave background radiation.

•To have a Hawking temperature larger than 2.7 K (and be able to evaporate), a black hole needs to have less mass than the Moon.

•Such a black hole would have a diameter of less than a tenth of a millimeter.

•If a black hole is very small the radiation effects are expected to become very strong. Even a black hole that is heavy compared to a human would evaporate in an instant.