Stephen W Hawking Scientific Life and Legacy for Humanity 17 de marzo de 2018

Le champ de gravitation d'un trou noir stellaire entouré d'un disque d'accrétion chaud et lumineux déforme fortement l'image de ce disque. On peut s'en
rendre compte avec cette image, extraite d'une simulation de ce que verrait un observateur s'approchant de l'astre compact selon une direction légèrement
inclinée au-dessus du disque d'accrétion. La partie du disque située derrière le trou noir semble tordue à 90° et devient visible. Jean-Pierre Luminet a fait la
première simulation de ces images en 1979, comme il l'explique dans une vidéo au début de cet article. © Jean-Pierre Luminet, Jean-Alain Marck
BH Thermodynamics
Universe Wave Function
Theory of Everything
Stephen W. Hawking
(08Jan1942-14March2018)
Scientific Life and Legacy for Humanity
Une brève histoire d'un scientifique hors norme
By: Herman J. Mosquera Cuesta (PhD Astrophysics)
Resumé:
Steph Hawking, one of the most influential physicists of the twentieth century and perhaps the most celebrated
icon of contemporary science, has died at the age of 76. On the occasion of this very sad ephemerides for
science and humanity, in this conference I will briefly review some aspects of personal life, and scientific legacy
for humanity by -Astrophysicist, Cosmologist and Physicist -Prof. Stephen W. Hawking. There is a number of
contributions to our current understanding about the universe. I will readily focus on his theories about the
origin and evolution of the cosmos (beginning singularity, wave function, i.e. no boundary proposal, quantum
gravity, i.e. theory of everything) , the elusive nature of black holes and related fundamental problems:
astrophysical existence by itself, Hawking radiation and its relation -or not- to the information paradox. As a
humanist worried about Humans survival on Earth, Hawking states: “…We are close to the tipping point, where
global warming becomes irreversible”. On space exploration he stated: « … l’humanité doit se préparer à quitter
la Terre tout de suite … ». And subsequently, about the aliens he advised: « … je vous déconseille à nouveau de
parler aux extraterrestres ... ». As for his mortality, Hawking was remarkably blunt: There is no heaven or
afterlife for broken-down computers; that is a fairy story for people afraid of the dark. Hawking passed away on
this date it’s a great loss for humanity. The scientific community and people loving science are all very saddened.

A Brief history of Stephen W. Hawking’s Family: Jane (Ex-
Wife), Lucy, Robert, Timothy, Frank (Father), Isobel (Mother)

A Brief history of Stephen W. Hawking: 20 Yrs Old PhD Grad
Cambridge University – Adviser Prof. Denis Sciama
Science Popular/Technical Books

Look up to the stars, not
down at your feet. Try to
make sense of what you
see, and wonder about
what makes the Universe
exist. Be curious.
Stephen Hawking

Copernican Model vs. Cosmos Through Black Hole Limb
Gravitational Lensing
Classically, a black hole should be 'perfectly cold' in the
sense that it absorbs everything but emits nothing.
This is how they were understood in the early 1970s.
Hawking’s quantum effects changed all that !! Making
them to thermally radiate at a temperature inversely
proporcional to its mass M (1974)

Hawking Contribution to BHs Understanding: dS = dQ/T
The randomness of quantum creation becomes the randomness of heat: Entropy
Quantum Physics + General Relativity
LIGO Direct GWs Detection vs. Actual Astrophysical BHs
Celestial Dome Distorted by SM Black
Hole in Front of Milky Way Center
LIGO BHs Merger Direct Detection

Stephen Hawking: Top 5 de ses découvertes scientifiques
• 1 - La croissance de la surface d’un trou noir
Il s'attarde sur les phénomènes se déroulant
sur l'horizon, cette limite immatérielle
marquant en quelque sorte la frontière du
trou noir.
Hawking aboutit à une curieuse conclusion.
« Si deux trous noirs se heurtaient avant de se
fondre pour n'en former plus qu'un, la surface
de l'horizon du trou noir final serait
supérieure à la somme des surfaces des trous
noirs originaux.
Cette propriété de non-croissance limite
considérablement le comportement possible
d'un trou noir. Je fus si excité par ma
découverte que je ne dormis guère cette nuit-
là. Le lendemain, j'appelais Roger Penrose. »
Stephen Hawking et sa fille Lucy.
Timothy and Robert are his sons. Jane
mother
• 1 - La croissance de la
surface d’un trou noir
• 2 - Le rayonnement de
Hawking
• 3- Le paradoxe de
l’information qui disparaît
• 4 - Les théorèmes sur les
singularités
• 5 -Le temps imaginaire de
Hartle-Hawking

Quantum Gravity, Hawking Radiation and
Information Paradox

• 2 - Le rayonnement de Hawking
Il montre surtout que si un trou noir
émet un rayonnement, il doit
adopter le spectre du rayonnement
d'un corps chaud particulier que l'on
appelle un corps noir, avec une
température ne dépendant que de sa
masse.
C'est précisément ce qu'il fallait pour
assurer l'existence de l'entropie d'un
trou noir. Il trouve cette explication
dans la physique quantique.
Les fluctuations quantiques du vide
créent des paires de particule-
antiparticule virtuelles qui ne vivent
que très peu de temps avant de
s'annihiler mutuellement sans quoi
elles violeraient le principe de
conservation de l'énergie
Tout près de l'horizon d'un trou noir, juste
son extérieur, les paires de particules
peuvent être séparées par des forces de
marée qui fournissent de l'énergie et
rendent ces particules réelles, autant
que celles qui nous entourent.
Lorsque l'une d'elles passe l'horizon, pour un
observateur extérieur, elle se comporte
comme une particule d'énergie négative,
tandis que l'autre a une énergie positive.
Le même observateur extérieur voit donc de
l'énergie émise par le trou noir sous forme
de particules (de matière ou d'antimatière),
lequel absorbe en permanence un flux
d'énergie négative, ce qui, d'après la
célébrissime formule E=mc2, correspond à
une perte de masse.
Un trou noir s'évapore, annonce Stephen
Hawking. Lentement, mais sûrement.

• Si la surface d'un trou noir ne peut que croître,
ce comportement évoque une quantité
physique qui se comporte de la même
manière: l'entropie. Elle décrit le désordre d'un
système et le second principe de la
thermodynamique affirme qu'elle ne peut que
croître dans un système isolé.
• Mais le rapprochement semblait initialement
problématique. Si un trou noir se trouve
entouré de gaz qu'il avale en partie, il absorbe
aussi l'entropie du gaz.
• Or, le second principe de la thermodynamique
implique que l'entropie totale de
l'ensemble gaz-trou noir ne peut diminuer.
• Il n'est pas violé que si la surface de l'horizon
des événements est bien une mesure de
l'entropie du trou noir. Alors, en effet,
elle augmente avec l'absorption de ce gaz.
Or, un système physique qui a de
l'entropie a aussi une température et
ce qui a une température émet un
rayonnement. Et à cette époque, les
trous noirs ne sont pas censés
émettre quoi que ce soit.
=============================
=============================
In the mid-1970s, Hawking
discovered that black holes are not
truly black, and in fact emit some
radiation2.
According to quantum physics, pairs
of particles must appear out of
quantum fluctuations just outside
the event horizon — the black hole’s
point of no return.
Some of these particles escape the
pull of the black hole but take a
portion of its mass with them,
causing the black hole to slowly
shrink and eventually disappear.

Basics: Hawking Radiation vs.
Information Paradox
On parle de l'évaporation des trous noirs due au
rayonnement de Hawking. Cette évaporation
induit une énigme connue sous le nom de
paradoxe de l'information avec la physique des
trous noirs.
Toutefois, la même théorie quantique, qui
implique l'existence du rayonnement Hawking,
affirme que l'information est indestructible.
Techniquement on parle de conservation de
l'unitarité. Il devrait donc exister des structures
dans le trou noir qui gardent la mémoire de
cette information.
On pourrait penser qu'elle est codée dans le
rayonnement émis par le trou noir qui, en
réponse, doit s'évaporer puisqu'il perd de la
masse, du moment cinétique et de la charge
sous la forme des particules émises. Mais
comme ce rayonnement doit être celui d'un
corps noir, le plus désordonné possible, ce ne
pouvait pas être le cas.
Une symétrie qui code l'information dans la géométrie de l'espace-temps?
Basiquement, il semble que tout tourne autour des ondes gravitationnelles
émises par une étoile en train de s'effondrer en donnant un trou noir et qui
sont émises aussi lorsqu'un objet tombe dans un trou noir.

• 3- Le paradoxe de l’information qui disparaît
Tout ce qui tombe dans un trou noir disparaît à
jamais. Ou plus exactement, le trou noir semble ne
retenir des caractéristiques de cette matière que sa
masse, son moment cinétique et ses charges
électriques et magnétiques.
Plus de formes ni de structures : une planète
entière avec tout ce qu'elle portait serait réduite à
une collection d'objets décrits par ces quatre
nombres.
Autrement dit, toute l'information, qui était
nécessaire pour décrire (ou représentée par) les
océans, les plaques tectoniques, les organismes
vivants, les bibliothèques ou les pages Web, aura
disparu. Impossible dit la physique quantique qui,
pourtant, affirme que le rayonnement de corps noir
émit par le trou noir ne doit pas coder de
l'information, étant aussi désordonné que possible!
• 4 - Les théorèmes sur les singularités
Hawking va étendre les travaux de
Penrose, d'abord seul puis en sa
compagnie, au cas du Big Bang.
Là aussi, les deux chercheurs
aboutissent à la conclusion qu'une
singularité est inévitable... si la théorie
de la relativité générale seule est
employée pour décrire ces
phénomènes.
The beginning of the Universe means
fundamentally the origin of space and
time, and flying apart matter of course.
Thereby, asking about what was there
before the Big Bang makes no sense, at
all !! … All this according to the general
relativistic standard model of cosmology
(ʌCDM).

• 5 -Le temps imaginaire de Hartle-Hawking
En 1983, Jim Hartle et Steph Hawking proposent une
description quantique de l'univers tout près du Big
Bang dans laquelle le temps se comporte exactement
comme une dimension d'espace (for τ < 0! Euclidean
(Quantum Gravity/Path Integral Techniq) ≠ Relativistic).
Le temps ne serait apparu, si l'on peut dire, qu'après la
fameuse ère de Planck relevant d'une théorie
quantique de la gravitation.
L'espace-temps doit alors se décrire non pas
uniquement par des nombres réels mais aussi par des
nombres complexes, au sens mathématique du terme,
le temps pouvant alors même être décrit uniquement
par la partie imaginaire de ces nombres (toujours au
sens mathématique du terme). Il n'y aurait plus alors
de singularité.
Au moment du Big Bang, le temps tel que nous le
ressentons aujourd'hui n'existait pas et la question de l
Quantum bounce could make black holes explode.
Idem for the Universe Big Bang, via Planck stars !!
ds2 = (-i cτ)2 + dx2 +dy2 + dz2 : Euclidean – C=0
≠
ds2 = - (ct) 2 + dx2 +dy2 + dz2 : Riemannian – C>0
A sort of Penrose’s Conformal Cyclic Cosmology
Or
M. Novello’s Eternal Universe
l'avant-Big Bang n'a plus de sens.

Solution to The Information Paradox
Firewall vs. Apparent Horizon
Le plus fameux d'entre eux est celui du paradoxe de l'information. Il a aussi été découvert par
Stephen Hawking alors qu'il réfléchissait aux conséquences de l'association d'une entropie à
l'horizon des événements d'un trou noir (par Jacob Bekenstein) et au fait que le rayonnement
dont il avait démontré l'existence était celui d'un corps noir.
• Cette symétrie est décrite par un groupe dit BMS, pour
Bondi–Metzner–Sachs, ses découvreurs. Ce groupe décrit
une symétrie particulière, des supertranslations (rien à
voir avec la supersymétrie et la supergravité) et qui dans
l'espace-temps plat, via le groupe de Poincaré (qui en est
un sous-groupe), explique la conservation de la quantité
de mouvement.
• Ce groupe BMS est associé à une structure géométrique
équivalente à une sphère, comme l'est la géométrie de
l'horizon des événements. Comme dans le cas du
principe holographique et de la conjecture AdS-Cft, il
semble que Hawking ait établi un pont entre ce qui se
passe à l'infini de l'espace-temps entourant un trou noir,
et sa dynamique, y compris son horizon, en découvrant la
symétrie des supertranslations cachée dans la géométrie
de cet horizon.
• Comme ces supertranslations existe en nombre très
élevé, et même infini en relativité générale classique, et,
qu'en physique, des symétries dans les équations
impliquent des quantités conservées, de l'information
serait donc codée de façon très subtile dans la géométrie
de l'horizon. Elle serait probablement très compliquée et
pas parfaitement lisse comme on le pensait. C'est là que
l'information serait conservée. Elle ne tomberait jamais
dans le trou noir, ce qui permet peut-être de résoudre un
autre paradoxe, celui du pare-feu (Firewall).
S. W. Hawking and Lawrence Krauss

Solution to The Information Paradox: Tricky Transfer
Hawking, Strominger & Perry (2014-2015)• The paper goes on to suggest a mechanism for
transferring that information to the black hole —
which would have to happen for the paradox to be
solved. The authors do this by calculating how to
encode the data in a quantum description of the
event horizon, known whimsically as ‘black hole
hair’.
• Other physicists are more optimistic about the
method’s prospects for solving the information
paradox, including Sabine Hossenfelder of the
Frankfurt Institute for Advanced Studies in
Germany. She says that the results on soft hair,
together with some of her own work, seem to
settle a more-recent controversy over black holes,
known as the firewall problem.
• This is the question of whether the formation of
Hawking radiation makes the event horizon a very
hot place. That would contradict Albert Einstein’s
general theory of relativity, in which an observer
falling through the horizon would see no sudden
changes in the environment“.
• If the vacuum has different states,” Hossenfelder
says, “then you can transfer information into the
radiation without having to put any kind of energy
at the horizon. Consequently, there’s no firewall.”
• In a paper3 published in 1976, Hawking pointed out that the
outflowing particles — now known as Hawking radiation —
would have completely random properties. As a result, once
the black hole was gone, the information carried by anything
that had previously fallen into the hole would be lost to the
Universe. But this result clashes with laws of physics that say
that information, like energy, is conserved, creating the
paradox. “That paper was responsible for more sleepless
nights among theoretical physicists than any paper in history”.
• The mistake, Strominger explained, was to ignore the
potential for the empty space to carry information. In their
paper, they turn to soft particles. These are low-energy
versions of photons, hypothetical particles known as
gravitons and other particles. Until recently, these were
mainly used to make calculations in particle physics. But the
authors note that the vacuum in which a black hole sits need
not be devoid of particles — only energy — and therefore
that soft particles are present there in a zero-energy state.
• It follows that anything falling into a black hole would leave
an imprint on these particles. “If you’re in one vacuum and
you breathe on it — or do anything to it — you stir up a lot of
soft gravitons”. After this disturbance, the vacuum around the
black hole has changed, and the information has been
preserved after all.

Tricky Transfer: Continued …
• Still, the work is incomplete.
Abhay Ashtekar, who studies
gravitation at Pennsylvania
State University in University
Park, says that he finds the
way that the authors transfer
the information to the black
hole — which they call ‘soft
hair’ — unconvincing.
• And the authors
acknowledge that they do
not yet know how the
information would
subsequently transfer to the
Hawking radiation, a further
necessary step.
• Steven Avery, a theoretical
physicist at Brown University
in Providence, Rhode Island,
is sceptical that the approach
will solve the paradox, but is
excited by the way it
broadens the significance of
soft particles.
• He notes that Strominger has
found that soft particles
reveal subtle symmetries of
the known forces of nature4,
“some of which we knew and
some of which are new”.

Other HJMC’s Scientific Articles
On Black Stars vs. Black Holes
Farewell to black hole horizons and
singularities?
C. Corda
(Assoc. Sci. Galileo Galilei),
D. Leiter
(Unlisted)
H.J. Mosquera Cuesta
(Acarau State U., Sobral & Rio de Janeiro,
CBPF & ICRA, Pescara)
S. Robertson
(Southwestern Oklahoma State U.)
R.E. Schild
(Harvard-Smithsonian Ctr. Astrophys.)
Published in J. Cosmol. 17 (2011) 7412
Irreversible gravitational collapse: Black stars
or black holes?
Christian Corda
(IBR, Palm Harbor & PRATO, Italy)
Herman J. Mosquera Cuesta
(Acarau State U., Sobral & Rio de Janeiro,
CBPF & ICRA, Pescara & PRATO, Italy)
Published in Hadronic J. 34 (2011) 149-159

Black Hole Pretenders Could Really Be Bizarre Quantum Stars
New research reveals a possible mechanism allowing “black stars” and “gravastars”
When giant stars die, they don’t just fade
away. Instead they collapse in on
themselves, leaving behind a compressed
stellar remnant, usually a city-size,
superdense ball of neutrons appropriately
called a neutron star.
In extreme cases, however, most theorists
believe an expiring giant star will form a
black hole—a pointlike “singularity” with
effectively infinite density and a
gravitational field so powerful that not even
light, the fastest thing in the universe, can
escape once falling in.
Now a new study is reinvigorating an
alternate idea, that objects with names
such as “black stars,” or “gravastars,” might
exist midway between neutron stars and
black holes. If real, these exotic stellar
corpses should appear nearly identical to
black holes save in one key way—they could
not irretrievably swallow light.
16 March 2018

Black Hole Pretenders Could Really Be Bizarre Quantum Stars
New research reveals a possible mechanism allowing “black stars” and “gravastars”
• There are good reasons to seek such alternatives,
because black holes raise a host of theoretical
problems.
• For instance, their singularities are supposedly
hidden by invisible boundaries known as event
horizons. Throw something into a black hole, and
once it passes the event horizon it should be
gone—forever—with no hope whatsoever of
return. But such profound annihilation clashes with
other long-cherished laws of physics that suggest
the destruction of information is impossible,
including information encoded within anything
falling into black holes.
• Conceived and developed across the past two
decades, in part to sidestep such conundrums,
models of black stars and gravastars postulate
these objects would lack singularities and event
horizons. But questions have lingered as to whether
such objects could actually form—and remain
stable after they did.
• New research from theoretical physicist Raúl
Carballo-Rubio at the International School for
Advanced Studies in Italy provides a novel
mechanism that might allow black stars and
• Carballo-Rubio investigated a strange phenomenon
known as quantum vacuum polarization.
• Quantum physics, the best description yet of how all
known subatomic particles behave, suggests reality is
fuzzy, limiting how precisely one can know the
properties of the most basic units of matter—for
instance, one can never absolutely know a particle's
position and momentum at the same time.
• One strange consequence of this uncertainty is that a
vacuum is never completely empty but instead foams
with so-called “virtual particles” that continuously
fluctuate into and out of existence.
• In the presence of gigantic amounts of energyof the
sort produced by the collapse of a giant starprevious
research found these virtual particles can polarize, or
arrange themselves depending on their properties,
much as magnets are divided into north and south
poles.
• Carballo-Rubio calculated the polarization of these
particles can produce a surprising effect inside the
powerful gravitational fields of dying giant stars—a
field that repels instead of attracts.

Open, Flat or Closed UniverseCosmic Expansion History
Role of Dark Energy
Latest PLANCK SAT Results
On CMB Anisotropies
COSMOLOGY
What We Currently Know About The Universe

Structure Formation in the Universe
--- Timeline ---

Some Products of Growth of Mass Segregation:
Smallest, Faintest, Most Distant Galaxies

Hartle-Hawking (1980’s) -Hertog
The No Boundary Proposal: Early Universe Model
The No Boundary Proposal
• In the 1960’s and 70’s Hawking and
Penrose showed that according to
classical general relativity, given some
minimal assumptions the origin of an
expanding universe is a singularity: a
point of infinite density and spacetime
curvature.
• But this and other singularity theorems
do not take into account the strange
world of quantum mechanics.
Quantum Cosmology, i. e.
Universe Creation from Nothing
• So in the 1980’s Hawking and
collaborators started to build a model
of the big bang that included quantum
effects.
• The result is the No Boundary Proposal,
a model that may be able to explain
some of the deepest mysteries of the
cosmos such as, is there a multiverse?
• how is there an arrow of time and,
• what really happened at the big bang?
First hints are emerging of a universe that existed before our own: an alien world of chaos where time, space and geometry were
yet to form

Wave Function of the Universe
Jim B. Hartle & Stephen W. Hawking
Phys. Rev. D 28, 2960 – 15 December (1983)
In theoretical physics, the Hartle–Hawking state is a proposal concerning the
state of the Universe prior to the Planck epoch• Hartle and Hawking suggest that if we
could travel backward in time toward
the beginning of the Universe, we
would note that quite near what might
have otherwise been the beginning,
Universe has no beginning, but it is not
the steady state Universe of Hoyle; it
simply has no initial boundaries in time
nor space.
• Time gives way to space such that at
first there is only space and no time.
• Beginnings are entities that have to do
with time; because time did not exist
before the Big Bang, the concept of a
beginning of the Universe is
• According to the Hartle–Hawking
proposal, the Universe has no
origin as we would understand it:
the Universe was a singularity in
both space and time, pre-Big Bang.
• Thus, the Hartle–Hawking state is
the wave function of the
Universe—a notion meant to figure
out how the Universe started—that
is calculated from Feynman's path
integral.
• More precisely, it is a hypothetical
vector in the Hilbert space of a
theory of quantum gravity that
describes this wave function

Wave Function of the Universe
Jim B. Hartle & Stephen W. Hawking
Phys. Rev. D 28, 2960 – 15 December (1983)
Technical explanation
• It is a functional of the metric
tensor defined at a (D − 1)-
dimensional compact surface, the
Universe, where D is the spacetime
dimension.
• The precise form of the Hartle–
Hawking state is the path integral
over all D-dimensional geometries
that have the required induced
metric on their boundary.
• According to the theory, time
diverged from a three-state
dimension— as we know time
now—after the Universe was at
the age of Planck time.
• Such a wave function of the
Universe can be shown to satisfy
the Wheeler–DeWitt equation.

Hawking and the Future of Humanity on the Planet Earth
(2005) It is a waste of time to be angry about my disability. One has to get on with life and I
haven't done badly. People won't have time for you if you are always angry or complaining.
Hawking was asked: "What mystery do you find most intriguing, and why?" His answer?
"Women. My PA reminds me that although I have a PhD in physics, women should remain
a mystery.“
As for his mortality, Hawking was remarkably blunt: I regard the brain as a computer which
will stop working when its components fail. There is no heaven or afterlife for broken-
down computers; that is a fairy story for people afraid of the dark.
About space exploration
he stated:
Humanity either colonizes
space or disappears
On the climate
change he advised:
We are close to the
tipping point,
where global
warming becomes
irreversible

Hawking warned that the ever-rising human population, and its mounting
energy needs, could render Earth uninhabitable by the year 2600
Hawking About the Future of
Humanity on Planet Earth
• Shouldn't we be content to be cosmic
sloths, enjoying the universe from the
comfort of Earth?
• The answer is, no. The Earth is under
threat from so many areas that it is
difficult for me to be positive (June
20, 2017)
• The whole history of science has been
the gradual realization that events do
not happen in an arbitrary manner,
but that they reflect a certain
underlying order, which may or may
not be divinely inspired
Hawking About Contact to Aliens
One day, we might receive a signal from a planet
like this, Hawking said, referring to the
potentially habitable alien planet Gliese 832c.
But we should be wary of answering back
Meeting an advanced civilization could be like
Native Americans encountering Columbus. That
didn't turn out so well (2016, Documentary
Hawking's Favorite Places)
If aliens ever visit us, I think the outcome would
be much as when Christopher Columbus first
landed in America, which didn't turn out very
well for the Native Americans. (Episode of the
Discovery Channel's "Into the Universe
with Stephen Hawking," a show hosted by the
Discovery Channel, 2010)

During a lecture entitled "The Origin of the Universe," Hawking mentioned the
idea that people continue to seek divine solutions to counter physicist's
theories, quipping, What was God doing before the divine creation?, Was he
preparing hell for people who asked such questions? (April 16, 2013)
On Human Behaviour
• The human failing I would most like
to correct is aggression
• It may have had survival advantage
in caveman days, to get more food,
territory or partner with whom to
reproduce, but now it threatens to
destroy us all (February 2015)
• Although the chance of a disaster
to planet Earth in a given year may
be quite low, it adds up over time,
and becomes a near certainty in
the next thousand or 10 thousand
years (2016)
About Climate Change
• We are close to the tipping
point, where global
warming becomes irreversible.
• Trump's action could push the
Earth over the brink, to become
like Venus, with a temperature
of 250 degrees [Celsius], and
raining sulfuric acid, referring to
the president's decision in June
2017 to pull the U.S. out of the
Paris climate deal.
Five-year average variation of global surface temperatures. Dark blue indicates areas cooler than
average. Dark red indicates areas warmer than average. Credit NASA Global Climate Change

NASA Remembers Dr. Stephen Hawking
Acting Administrator Robert Lightfoot‌:‌Today, the world lost a giant among men,
whose impact cannot be overstated. His loss is felt around the world by all he inspired
with his work and his personal story of perseverance. Our condolences go out to the
family and friends of Stephen Hawking. Thanks to his monumental contributions, the
pioneer in all of us is ever the closer to reaching new destinations beyond our planet.
Stephen Hawking was a brilliant cosmologist who has
changed our view of the universe with his remarkable
theories and outreach. He also inspired generations
around the world, making some of the most complicated
physics of our time accessible to the masses.
Hawking delivers a speech entitled "Why we
should go into space“. Lecture part of a series
honoring NASA's 50th Anniversary, April 21,
2008, at George Washington University's
Morton Auditorium in Washington.

Thomas Zurbuchen
Associate Administrator of NASA’s Science Mission
Directorate at NASA Headquarters in Washington:
• Along with groundbreaking and
inspiring work came another
attribute that made Stephen a
hero not just to younger
generations, but also to his
peers.
• A longtime friend to NASA,
Stephen was a passionate
communicator who wanted to
share the excitement of
discovery with all.
• Although humanity has lost one of
the most prominent cosmologists
and astrophysicists of our time, his
work and vision will last forever.
• His ability to communicate to the
general public about the
importance to study the universe
and move science forward is a
legacy that will endure to achieve
greater heights to explore the solar
system and beyond.

Hommage à Stephen Hawking :
Une brève histoire d'un scientifique hors norme

Stephen W Hawking Scientific Life and Legacy for Humanity 17 de marzo de 2018

Stephen W Hawking Scientific Life and Legacy for Humanity 17 de marzo de 2018

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Stephen W Hawking Scientific Life and Legacy for Humanity 17 de marzo de 2018