Remember the last post about SpaceX? Well they are at it again!
This time, SpaceX has propelled supplies to International space station on saturday.More so is that they used a verssel that has flown before.
The refurbished Dragon cargo capsule propeled into space annexed to a Falcon 9 rocket at 5:07 pm (2107 GMT) from Cape
Canaveral, Florida.
With a countdown made by NASA spokesman Mike Curie, the rocket blazed a steady vertical path into the clouds.
The last time this particular
spaceship(Dragon) flew to space was in 2014.
The Dragon on present mission is packed with almost
6,000 pounds (2,700 kilograms) of science research, crew supplies and hardware
and should arrive at the Monday(ISS time).
The supplies for special experiments
include live mice to study the effects of osteoporosis and fruit flies for
research on microgravity's impact on the heart.
The spacecraft is also loaded with
solar panels and equipment to study neutron stars.
After about 10 minutes after launch,
SpaceX successfully returned the first stage of the Falcon 9 rocket back to a
controlled landing at Cape Canaveral.
The rocket powered its engines and
guided itself down to Landing Zone One, not far from the launch site.
"The first stage is back,"
Curie said in a NASA live webcast, as video images showed the tall, narrow
portion of the rocket touch down steadily in a cloud of smoke.
SpaceX said it marked the company's
fifth successful landing on solid ground. Several of its Falcon 9 rockets have
returned upright to platforms floating in the ocean.
The effort is part of SpaceX's push
to make spaceflight cheaper by re-using costlyrocket
and spaceship components after each launch, rather than ditching them in the
ocean.
The launch was the 100th from NASA's
historic launch pad 39A, the starting point for the Apollo missions to the Moon
in the 1960s and 1970s, as well as a total of 82 shuttle flights.
A composite image of the Western hemisphere of the Earth. Credit: NASA
More than 90% of Earth's continental crust
is made up of silica-rich minerals, such as feldspar and quartz. But
where did this silica-enriched material come from? And could it provide a
clue in the search for life on other planets?
Conventional
theory holds that all of the early Earth's crustal ingredients were
formed by volcanic activity. Now, however, McGill University earth
scientists Don Baker and Kassandra Sofonio have published a theory with
a novel twist: some of the chemical components of this material settled
onto Earth's early surface from the steamy atmosphere that prevailed at
the time.
First, a bit of ancient geochemical history: Scientists believe that a
Mars-sized planetoid plowed into the proto-Earth around 4.5 billion
years ago, melting the Earth and turning it into an ocean of magma. In
the wake of that impact—which also created enough debris to form the
moon—the Earth's surface gradually cooled until it was more or less
solid. Baker's new theory, like the conventional one, is based on that
premise.
The atmosphere following that collision, however, consisted of
high-temperature steam that dissolved rocks on the Earth's immediate
surface—"much like how sugar is dissolved in coffee," Baker explains.
This is where the new wrinkle comes in. "These dissolved minerals rose
to the upper atmosphere and cooled off, and then these silicate materials that were dissolved at the surface would start to separate out and fall back to Earth in what we call a silicate rain."
To test this theory, Baker and co-author Kassandra Sofonio, a McGill
undergraduate research assistant, spent months developing a series of
laboratory experiments designed to mimic the steamy conditions on early
Earth. A mixture of bulk silicate earth materials and water was melted
in air at 1,550 degrees Celsius, then ground to a powder. Small amounts
of the powder, along with water, were then enclosed in gold palladium
capsules, placed in a pressure vessel and heated to about 727 degrees
Celsius and 100 times Earth's surface pressure to simulate conditions in
the Earth's atmosphere about 1 million years after the moon-forming
impact. After each experiment, samples were rapidly quenched and the
material that had been dissolved in the high temperature steam analyzed.
The experiments were guided by other scientists' previous experiments
on rock-water interactions at high pressures, and by the McGill team's
own preliminary calculations, Baker notes. Even so, "we were surprised
by the similarity of the dissolved silicate material produced by the
experiments" to that found in the Earth's crust.
Their resulting paper, published in the journal Earth and Planetary Science Letters,
posits a new theory of "aerial metasomatism"—a term coined by Sofonio
to describe the process by which silica minerals condensed and fell back
to earth over about a million years, producing some of the earliest
rock specimens known today.
"Our experiment shows the chemistry of this process," and could
provide scientists with important clues as to which exoplanets might
have the capacity to harbor life Baker says.
"This time in early Earth's history is still really exciting," he
adds. "A lot of people think that life started very soon after these
events that we're talking about. This is setting up the stages for the
Earth being ready to support life."
NASA's Juno spacecraft soared directly over Jupiter's south pole
when JunoCam acquired this image on February 2, 2017 at 6:06 a.m. PT
(9:06 a.m. ET), from an altitude of about 62,800 miles (101,000
kilometers) above the cloud tops. Credit: NASA
NASA's Juno mission to Jupiter, which has
been in orbit around the gas giant since July 4, 2016, will remain in
its current 53-day orbit for the remainder of the mission. This will
allow Juno to accomplish its science goals, while avoiding the risk of a
previously-planned engine firing that would have reduced the
spacecraft's orbital period to 14 days.
"Juno is healthy, its science
instruments are fully operational, and the data and images we've
received are nothing short of amazing," said Thomas Zurbuchen, associate
administrator for NASA's Science Mission Directorate in Washington.
"The decision to forego the burn is the right thing to do—preserving a
valuable asset so that Juno can continue its exciting journey of
discovery."
Juno has successfully orbited Jupiter four times since arriving at
the giant planet, with the most recent orbit completed on Feb. 2. Its
next close flyby of Jupiter will be March 27.
The orbital period does not affect the quality of the science
collected by Juno on each flyby, since the altitude over Jupiter will be
the same at the time of closest approach. In fact, the longer orbit
provides new opportunities that allow further exploration of the far
reaches of space dominated by Jupiter's magnetic field, increasing the
value of Juno's research.
During each orbit, Juno soars low over Jupiter's cloud tops—as close
as about 2,600 miles (4,100 kilometers). During these flybys, Juno
probes beneath the obscuring cloud cover and studies Jupiter's auroras
to learn more about the planet's origins, structure, atmosphere and
magnetosphere.
The original Juno flight plan envisioned the spacecraft looping
around Jupiter twice in 53-day orbits, then reducing its orbital period
to 14 days for the remainder of the mission. However, two helium check
valves that are part of the plumbing for the spacecraft's main engine
did not operate as expected when the propulsion system was pressurized
in October. Telemetry from the spacecraft indicated that it took several
minutes for the valves to open, while it took only a few seconds during
past main engine firings.
"During a thorough review, we looked at multiple scenarios that would
place Juno in a shorter-period orbit, but there was concern that
another main engine burn could result in a less-than-desirable orbit,"
said Rick Nybakken, Juno project manager at NASA's Jet Propulsion
Laboratory in Pasadena, California. "The bottom line is a burn
represented a risk to completion of Juno's science objectives."
Juno's larger 53-day orbit allows for "bonus science" that wasn't
part of the original mission design. Juno will further explore the far
reaches of the Jovian magnetosphere—the region of space dominated by
Jupiter's magnetic field—including the far magnetotail, the southern
magnetosphere, and the magnetospheric boundary region called the
magnetopause. Understanding magnetospheres and how they interact with
the solar wind are key science goals of NASA's Heliophysics Science
Division.
"Another key advantage of the longer orbit is that Juno will spend less time within the strong radiation belts on each orbit,"
said Scott Bolton, Juno principal investigator from Southwest Research
Institute in San Antonio. "This is significant because radiation has
been the main life-limiting factor for Juno."
Juno will continue to operate within the current budget plan through
July 2018, for a total of 12 science orbits. The team can then propose
to extend the mission during the next science review cycle. The review
process evaluates proposed mission extensions on the merit and value of
previous and anticipated science returns.
The Juno science team continues to analyze returns from previous
flybys. Revelations include that Jupiter's magnetic fields and aurora
are bigger and more powerful than originally thought and that the belts
and zones that give the gas giant's cloud top its distinctive look
extend deep into the planet's interior. Peer-reviewed papers with more
in-depth science results from Juno's first three flybys are expected to
be published within the next few months. In addition, the mission's
JunoCam—the first interplanetary outreach camera—is now being guided
with assistance from the public. People can participate by voting on
which features on Jupiter should be imaged during each flyby.
"Juno is providing spectacular results, and we are rewriting our
ideas of how giant planets work," said Bolton. "The science will be just
as spectacular as with our original plan."
This is the "South Pillar" region of the star-forming region
called the Carina Nebula. Like cracking open a watermelon and finding
its seeds, the infrared telescope "busted open" this murky cloud to
reveal star embryos tucked inside finger-like pillars of thick dust.
Credit: NASA
Physicists have proposed that the
violations of energy conservation in the early universe, as predicted by
certain modified theories in quantum mechanics and quantum gravity, may
explain the cosmological constant problem, which is sometimes referred
to as "the worst theoretical prediction in the history of physics."
The
physicists, Thibaut Josset and Alejandro Perez at the University of
Aix-Marseille, France, and Daniel Sudarsky at the National Autonomous
University of Mexico, have published a paper on their proposal in a
recent issue Physical Review Letters.
"The main achievement of the work was the unexpected relation between
two apparently very distinct issues, namely the accelerated expansion
of the universe and microscopic physics," Josset told Phys.org. "This offers a fresh look at the cosmological constant problem, which is still far from being solved."
Einstein originally proposed the concept of the cosmological constant in 1917 to modify his theory of general relativity in order to prevent the universe from expanding, since at the time the universe was considered to be static.
Now that modern observations show that the universe is expanding at
an accelerating rate, the cosmological constant today can be thought of
as the simplest form of dark energy, offering a way to account for current observations.
However, there is a huge discrepancy—up to 120 orders of
magnitude—between the large theoretical predicted value of the
cosmological constant and the tiny observed value. To explain this
disagreement, some research has suggested that the cosmological constant
may be an entirely new constant of nature that must be measured more
precisely, while another possibility is that the underlying mechanism
assumed by theory is incorrect. The new study falls into the second line
of thought, suggesting that scientists still do not fully understand
the root causes of the cosmological constant.
The basic idea of the new paper is that violations of energy conservation in the early universe
could have been so small that they would have negligible effects at
local scales and remain inaccessible to modern experiments, yet at the
same time these violations could have made significant contributions to
the present value of the cosmological constant.
To most people, the idea that conservation of energy is violated goes
against everything they learned about the most fundamental laws of
physics. But on the cosmological scale, conservation of energy is not as
steadfast a law as it is on smaller scales. In this study, the
physicists specifically investigated two theories in which violations of
energy conservation naturally arise.
The first scenario of violations involves modifications to quantum
theory that have previously been proposed to investigate phenomena such
as the creation and evaporation of black holes, and which also appear in
interpretations of quantum mechanics in which the wavefunction
undergoes spontaneous collapse. In these cases, energy is created in an
amount that is proportional to the mass of the collapsing object.
Violations of energy conservation also arise in some approaches to
quantum gravity in which spacetime is considered to be granular due to
the fundamental limit of length (the Planck length, which is on the
order of 10-35 m). This spacetime discreteness could have led
to either an increase or decrease in energy that may have begun
contributing to the cosmological constant starting when photons
decoupled from electrons in the early universe, during the period known
as recombination.
As the researchers explain, their proposal relies on a modification
to general relativity called unimodular gravity, first proposed by
Einstein in 1919.
"Energy from matter components can be ceded to the gravitational
field, and this 'loss of energy' will behave as a cosmological
constant—it will not be diluted by later expansion of the universe,"
Josset said. "Therefore a tiny loss or creation of energy in the remote
past may have significant consequences today on large scale."
Whatever the source of the energy conservation violation, the
important result is that the energy that was created or lost affected
the cosmological constant to a greater and greater extent as time went
by, while the effects on matter decreased over time due to the expansion
of the universe.
Another way to put it, as the physicists explain in their paper, is
that the cosmological constant can be thought of as a record of the
energy non-conservation during the history of the universe.
Currently there is no way to tell whether the violations of energy
conservation investigated here truly did affect the cosmological
constant, but the physicists plan to further investigate the possibility
in the future.
"Our proposal is very general and any violation of energy conservation
is expected to contribute to an effective cosmological constant,"
Josset said. "This could allow to set new constraints on
phenomenological models beyond standard quantum mechanics.
"On the other hand, direct evidence that dark energy is sourced by
energy non-conservation seems largely out-of-reach, as we have access to
the value of lambda [the cosmological constant] today and constraints on its evolution at late time only."
