Space > NASA
The Earthrise image
beamed from Apollo 8, 176,000 miles away,
to the Mission Operations Control Room in Houston.
Credit NASA/Johnson Space Center
Apollo 8’s Earthrise: The Shot Seen Round the World
Half a century ago today,
a photograph from the moon
helped humans rediscover Earth.
Dec. 21, 2018
Control Room - 10ft x 10ft Wind Tunnel
One of three control panels in the control
of the Lewis Unitary Plan Wind Tunnel.
The tunnel model (top center)
of the valves
that control the operating cycle of the tunnel.
The TV monitor screens can be connected
any of 3 closed-circuit TV cameras
used to monitor tunnel components.
NASA Center: Glenn Research Center
Image # : C1956-40250
Date : 10/17/1955
Center Number: C1956-40250
GRIN DataBase Number: GPN-2000-000598
Creator/Photographer: Martin Brown
Great Images in NASA
National Aeronautics and Space Administration NASA
NASA > Planet quest - The search for another Earth
Nasa marks 50 years of space photography - in pictures
29 December 2012
It's half a century
since Mariner 2 swept past Venus
at a distance of 22,000
and this year's stunning pictures
from across the solar system
show how much technology
Astronomy Picture of the Day Archive
NASA Photography from the NASA Photography Office
These official NASA photographs
are being made available via Flickr
what is making news across the agency.
Dryden Photo Gallery
This collection contains photos
of many of the unique research aircraft flown
at NASA Dryden Flight Research Center
at Edwards, California.
date from the 1940s to the present.
NASA Voyager ships
exoplanets > NASA’s TESS Spacecraft
NYT - 16 April 2018
/ NASA's Stardust spacecraft
NASA's mission control in Houston / Mission
Control Center at Johnson Space Center
scheduled to be the third lunar landing,
was launched at 1313 Houston time
on Saturday, April 11, 1970
'Houston, we have a problem'
NASA > libraries of space images
NASA > Great Images in Nasa GRIN
NASA > Images
‘Dark Energy’ Reported
November 17, 2006
The New York Times
By DENNIS OVERBYE
A strange thing happened to the universe five billion years
ago. As if God had turned on an antigravity machine, the expansion of the cosmos
speeded up, and galaxies began moving away from one another at an ever faster
Now a group of astronomers using the Hubble Space Telescope have discovered that
billions of years before this mysterious antigravity overcame cosmic gravity and
sent the galaxies scooting apart like muscle cars departing a tollbooth, it was
already present in space, affecting the evolution of the cosmos.
“We see it doing its thing, starting to fight against ordinary gravity,” Adam
Riess of the Space Telescope Science Institute said about the antigravity force,
known as dark energy. He is the leader of a team of “dark energy prospectors,”
as he calls them, who peered back nine billion years with the Hubble and were
able to discern the nascent effects of antigravity. The group reported their
observations at a news conference yesterday and in a paper to be published in
The Astrophysical Journal.
The results, Dr. Riess and others said, provide clues and place new limits on
the nature of dark energy, a mystery that has thrown physics and cosmology into
turmoil over the last decade.
“It gives us the ability to look at changes in dark energy,” he said in an
interview. “Previously, we knew nothing about that. That’s really exciting.”
The data suggest that, in fact, dark energy has changed little, if at all, over
the course of cosmic history. Though hardly conclusive, that finding lends more
support to what has become the conventional theory, that the source of cosmic
antigravity is the cosmological constant, a sort of fudge factor that Einstein
inserted into his cosmological equations in 1917 to represent a cosmic repulsion
embedded in space.
Although Einstein later abandoned the cosmological constant, calling it a
blunder, it would not go away. It is the one theorized form of dark energy that
does not change with time.
Sean Carroll, a cosmologist at the California Institute of Technology who was
not on the team, said: “Had they found the evolution was not constant, that
would have been an incredibly earthshaking discovery. They looked where no one
had been able to look before.”
The paper by Dr. Riess and his colleagues represents a sort of progress report
from the dark side, where astrophysicists have found themselves more and more as
they try to understand what is happening to the universe.
This encounter with the invisible began eight years ago, when two competing
teams of astronomers were using exploding stars known as Type 1a supernovas as
cosmic distance markers to determine the fate of the universe.
Ever since the Big Bang 14 billion years ago, the galaxies and the rest of the
universe have been flying apart like a handful of pebbles tossed in the air.
Astronomers reasoned that gravity would be slowing the expansion, and the teams
were trying to find out by how much and, thus, determine whether all would
collapse one day into a “big crunch” or expand forever.
Instead, to their surprise, the two teams, one led by Saul Perlmutter of the
University of California, Berkeley, and the other by Brian Schmidt of the Mount
Stromlo and Siding Spring Observatories in Australia, found that the universe
was speeding up instead of slowing down.
But the ground-based telescopes that the two teams used could track supernovas
to distances of just seven billion light-years, corresponding to half the age of
the universe, and the effect could have been mimicked by dust or a slight change
in the nature of the supernova explosions.
Since then, Dr. Riess, who was a member of Dr. Schmidt’s team, and his
colleagues have used the Hubble telescope to prospect for supernovas and dark
energy farther out in space or back in time.
The new results are based on observations of 23 supernovas that are more than
eight billion years in the past, before dark energy came to dominate the cosmos.
The spectra of those distant supernovas, Dr. Riess reported, appear to be
identical to those closer and more recent examples. By combining the supernova
results with data from other experiments like the NASA Wilkinson Microwave
Anisotropy Probe, Dr. Riess and his colleagues could begin to address the
evolution of dark energy.
“That’s one of the $64,000 questions,” he said. “Is dark energy changing?”
So far, he said, the results are consistent with the cosmological constant, but
other answers are also possible. The possibility that it is the cosmological
constant is a mixed blessing. Physicists concede that they do not understand it.
Dr. Carroll of Caltech said, “Dark energy makes us nervous.”
Einstein invented his constant to explain why the universe does not collapse.
After he abandoned it, the theory was resuscitated by quantum mechanics, which
showed that empty space should be bubbling with staggering amounts of repulsive
energy. The possibility that it really exists in the tiny amounts measured by
the astronomers has flummoxed physicists and string theorists.
Because it is a property of empty space, the overall force of Einstein’s
constant grows in proportion as the universe expands, until it overwhelms
everything. Other theories of dark energy like strange force fields called
quintessence or modifications to Einstein’s theory of gravity can change in more
complicated ways, rising, falling or reversing effects.
Astronomers characterize the versions of dark energy by their so-called equation
of state, the ratio of pressure to density, denoted by the letter w. For the
cosmological constant, w is minus one.
Dr. Riess and his group used their data to make the first crude measurement of
this quantity as it stood nine billion years ago. The answer, he said, was minus
one — the magic number — plus or minus about 50 percent. By comparison for more
recent times, with many more supernovas observable and thus more data, the value
is minus one with an uncertainty of about 10 percent.
“If at one point in history it’s not minus one,” Dr. Riess said, “then we have
killed the very best explanation.”
Getting to the precision needed to kill or confirm Einstein’s constant, however,
will be very difficult, he conceded. One of the biggest sources of uncertainty
is the fact that the Type 1a explosions are not completely uniform, introducing
scatter into the observations.
The Hubble is the sole telescope that can pursue supernova explosions deeply
enough to chart the early days of dark energy. The recent announcement that the
National Aeronautics and Space Administration will send astronauts to maintain
and refurbish the Hubble once again, enabling it to keep performing well into
the next decade, is a lift for Dr. Riess’s project. A new camera could extend
observations to 11 billion or 12 billion years back.
‘Dark Energy’ Reported,
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