This document discusses black holes and some of the key contributors to the field of black hole research. It provides information on what a black hole is, defines key terms like the event horizon, and discusses the goal of understanding the term "black hole" and learning about important contributors and discoveries. Three contributors are highlighted: John Michell who first proposed the idea of a body so massive that light could not escape in 1783; Albert Einstein whose theory of general relativity helped establish the modern concept of black holes; and Stephen Hawking who showed in 1974 that black holes emit thermal radiation known as Hawking radiation.

1. MAHAVIR SWAMI COLLEGE OF
ENGINEERING AND TECHNOLOGY

3. IMAGES OF BLACK HOLES

4. •A black hole is a region of • Around a black hole there is a
spacetime from which gravity mathematically defined
surface called an
prevents anything, including light, event horizon that marks the
from escaping. 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.
•This temperature is inversely
proportional to the mass of the • Quantum field theory in curved spa
black hole, making it difficult to predicts that event horizons
observe this radiation for emit radiation like a black
black holes of stellar mass or body with a finite temperature.
greater.

5. PROJECT GOAL
TO KNOW ABOUT:-
THE TERM “BLACK HOLE”.
CONTRIBUTOR’S IN THE FIELD OF BLACK HOLE.
DISCOVERY & RESEARCH ABOUT BLACK HOLE.

6. 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.

7. 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)

8. 1.Geologist john michell
John Michell was an
English natural
philosopher and
geologist whose work
spanned a wide range
of subjects from
astronomy to geology,
optics, and gravitation.
Born : December 25, 1724
He was both a Died : April 29, 1793
theorist and an Education : University of
Cambridge, Queens'
experimenter.
College, Cambridge

9. 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

10. 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.

11. 2. PHYSICIST ALBERT EINSTEIN
Albert Einstein was a German-born theoretical physicist who developed
the general theory of relativity, one of the two pillars of modern physics.
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

12. ALBERT EINSTEIN CONTRIBUTION
•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.

13. 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.

14. 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

15. STEPHAN HAWKING’S CONTRIBUTION
In 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.

16. 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.