Astronomy Picture of the Day |
APOD: 2002 February 24 - Isaac Newton Explains the Solar System
Explanation:
Sir Isaac Newton changed the world.
Born in 1642,
Newton was only an above-average student.
But he went home from
Cambridge
one summer in 1665, thought a lot about the
physical nature of the world, and came back two
years later with a revolutionary understanding of
mathematics,
gravitation, and optics.
A Professor of his, upon understanding what Newton had done,
resigned his own position at Cambridge so
Newton could have it.
Newton's
calculus
provided a new mathematical framework for the rapid solution of
whole classes of physical problems.
Newton's law of
gravitation explained
in one simple formula how apples fall and planets move.
Newton's insights proved to be so
overwhelmingly powerful he was the
first scientist ever knighted.
APOD: 2005 April 22 - Albert Einstein's Miraculous Year
Explanation:
In 1905
Albert
Einstein had a miraculous
year.
One hundred
years ago, he wrote four papers which
revolutionized our understanding of the Universe.
The papers outlined;
the idea that
light could behave as a
quantized particle (a photon),
an explanation of the
thermal
motion of atoms and molecules
(at a time when atoms themselves were just theories),
a theory reconciling motion
and the constant speed of light
(Special
Relativity), and
the idea of
mass-energy
equivalence
(E=mc²).
Virtually every facet of our modern exploration of the Universe
is touched by his now century old insights, along with his later
theory of
gravity
and space-time - General Relativity.
In centennial celebration,
consider this
thoughtful view of
a small telescope beside the
Einstein
Memorial on the grounds of the
National Academy of Sciences in Washington DC, USA.
The marble platform at the bronze statue's feet is embedded with a
map showing the positions of the planets, sun, moon and stars
on the memorial's dedication date, 100 years after Einstein's birth
in 1879.
Albert
Einstein died 50 years ago, on April 18, 1955.
APOD: 1999 June 6 - Kepler Discovers How Planets Move
Explanation:
Johannes Kepler used simple mathematics
to describe how planets move. Kepler was an assistant to the most accurate
astronomical observer of the time, Tycho Brahe.
Kepler was able to use
Brahe's data
to show that planets move in ellipses around the Sun
(Kepler's First Law),
that planets move proportionally faster in their
orbits when they are nearer the Sun (Kepler's Second Law), and that more
distant planets take proportionally longer to
orbit the Sun (Kepler's Third
Law).
Kepler lived from 1571 to 1630,
during the time of discovery of the telescope. Kepler was one of the few vocal supporters of
Galileo's discoveries and the
Copernican system of planets orbiting the
Sun instead of the
Earth.
APOD: 2002 January 13 - Hypatia of Alexandria
Explanation:
Sixteen hundred years ago, Hypatia became one of the world's leading
scholars in mathematics and astronomy.
Hypatia's
legendary knowledge, modesty,
and public speaking ability flourished
during the era of the Great Library of Alexandria.
Hypatia is credited with contributions to geometry and
astrometry, and she is thought
instrumental in the development of the sky-measuring
astrolabe.
"Reserve your right to think, for even to think wrongly is
better than not to think at all,"
Hypatia
is credited with saying.
"To teach superstitions as truth is a most terrible thing."
APOD: 2000 September 3 - Henrietta Leavitt Calibrates the Stars
Explanation:
Humanity's understanding of the relative brightness and variability of stars
was revolutionized by the work of Henrietta Swan Leavitt (1868-1921).
Working at
Harvard College Observatory, Leavitt precisely
calibrated the photographic magnitudes of 47 stars to which all other
stars could be compared.
Leavitt discovered and cataloged over 1500
variable stars
in the nearby
Magellanic Clouds.
>From this catalog, Leavitt discovered that brighter
Cepheid variable stars
take longer to vary, a fact used today to calibrate the
distance scale of our universe.
APOD: 1999 May 30 - Tycho Brahe Measures the Sky
Explanation:
Tycho Brahe was the most meticulous astronomical observer of his time.
Brahe, who lived between 1546 and 1601,
set out to solve the day's most pressing astronomical problem:
to determine whether the
Earth or the
Sun was at the center of the
Solar System.
To do this he and his assistants created the first major astronomical observatory where they devised and used the most accurate
pre-telescopic astronomical instruments.
Tycho Brahe thus compiled tables of
precise measurements of the positions and
brightnesses of planets and stars.
Brahe
never solved the Solar System problem himself -
but left data so impressively accurate his assistant
Johannes Kepler
was able to develop definitive laws. Brahe is also remembered for witnessing a supernova in 1572,
showing that the Great Comet of 1577 was not an
atmospheric phenomena, and for his metal nose.
APOD: 1998 September 13 - Galileo Demonstrates the Telescope
Explanation:
Galileo Galilei made a good discovery great. Upon hearing at age 40 that a
Dutch optician had invented a glass that made distant objects appear
larger,
Galileo crafted his own
telescope and turned it toward the
sky.
Galileo quickly discovered that our
Moon had
craters, that
Jupiter had its own
moons, that the
Sun has
spots,
and that
Venus has phases like our
Moon.
Galileo, who lived from 1564 to 1642, made many more discoveries.
Galileo
claimed that his observations only made sense if all the planets revolved
around the
Sun, as championed by
Aristarchus and Copernicus, not the
Earth,
as was commonly believed then. The powerful
Inquisition made
Galileo publicly
recant this conclusion, but today we know he was correct.
APOD: 1996 December 26 - Carl Sagan 1934-1996
Explanation:
Carl Sagan died last Friday at the age of
62. Sagan
was the world's most famous astronomer. Among his many activities
as a scientist, he contributed to the discovery that the atmosphere
of Venus is prohibitively hot and
dense, and found evidence that Saturn's
moon Titan contains oceans stocked with the building blocks of life.
Sagan
was an outspoken proponent of the search for extra-terrestrial life,
including sending probes to other planets and
listening with large radio telescopes
for signals from intelligent aliens. Sagan's
outstanding ability to explain allowed almost a billion people
to better understand the cosmos in which they live.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings, and
Disclaimers
NASA Official: Jay Norris.
Specific rights apply.
A service of:
EUD at
NASA /
GSFC
& Michigan Tech. U.