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Darja
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« Reply #2145 on: Nov 08, 2019, 04:31 AM »

Hubble spots our second interstellar visitor — a comet

"It's traveling so fast it almost doesn't care that the Sun is there."

Alexandru Micu
ZME
11/8/2019

Based on its current speed and trajectory, 2I/Borisov likely came from outside our solar system. It is the second such object after the asteroid ‘Oumuamua (identified in 2017). However, the two are very different beasts — while ‘Oumuamua was a rocky, solid body, 2I/Borisov is a comet. The image taken by Hubble is the best look we’ve had at 2I/Borisov so far and reveals a body of dust around a central core (which is too small to be seen in the image).

Watch: https://www.youtube.com/watch?v=JG9x6tkf8mg

It cometh second

    Whereas ‘Oumuamua appeared to be a rock, Borisov is really active, more like a normal comet. It’s a puzzle why these two are so different,” said David Jewitt of the University of California, Los Angeles (UCLA), leader of the Hubble team who observed the comet.

Being the second interstellar object we’ve found so close to home, researchers are very keen to study the properties and nature of 2I/Borisov. Its chemical composition, structure, and the dust around it are products of its host star system and can teach us about how they form. We won’t know for sure without further observation, but so far, the comet’s properties appear to be very similar to those in the Solar System.

The comet was 260 million miles from Earth when Hubble took its picture. It is on a hyperbolic path around the Sun, currently moving at around 110,000 miles per hour. Its closest approach will be on Dec. 7, 2019, when it will be twice as far from the Sun as Earth. By mid-2020, NASA adds, it will make its way past Jupiter and onto interstellar space.

    “It’s traveling so fast it almost doesn’t care that the Sun is there,” said Jewitt.

2I/Borisov was first discovered by Crimea-based amateur astronomer Gennady Borisov on Aug. 30, 2019. After a week of observations, the International Astronomical Union’s Minor Planet Center and the Center for Near-Earth Object Studies at NASA’s Jet Propulsion Laboratory in Pasadena, California, confirmed that it came from interstellar space. Future Hubble observations of 2I/Borisov are planned through January 2020, with more being proposed.
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« Reply #2146 on: Nov 09, 2019, 05:23 AM »

Astronomers confirm heavy elements are born from neutron star collisions

You like gold? That too may have been forged by the catacylsmic merger of neutron stars millions of years ago.

Tibi Puiu
ZME
11/9/2019

Heavier elements like iron, calcium, and nickel are made after atoms fuse in massive stellar explosions known as supernovae. Other relatively light elements, like aluminum, are made inside giant stars and blown out into space by stellar winds. But until now astronomers weren’t sure how much heavier elements such as gold, silver, or strontium formed.

This is where a groundbreaking new study comes in — the findings suggest that strontium, and likely other heavy-weight elements, is produced in the aftermath of a merger of two neutron stars.
A team of European researchers, using data from the X-shooter instrument on ESO’s Very Large Telescope, has found signatures of strontium formed in a neutron-star merger. This artist’s impression shows two tiny but very dense neutron stars at the point at which they merge and explode as a kilonova. In the foreground, we see a representation of freshly created strontium.

In 2017, astronomers detected a cosmic cataclysmic event: The merger of two neutron stars from 130 million years ago. The force of the collision was so strong that it literally shook the fabric of space-time, generating gravitational waves that eventually reached Earth, where they were detected. The two neutron stars either merged into a huge single neutron star or collapsed into a black hole.

A neutron star is the collapsed core of a large star — they’re the smallest and, at the same time, densest stars we know of. Most models suggest that they are made almost exclusively of neutrons — hence the name.

The existence of gravitational waves, which were first predicted by Einstein’s Theory of General Relativity about a hundred years ago, was confirmed only in 2016. The event was recorded by the Laser Interferometer Gravitational-Wave Observatory (LIGO), whose founders were awarded this year’s Nobel Prize in Physics.

Gravity waves are essentially ripples in the fabric of spacetime which are generated by interactions between very massive accelerating cosmic objects, such as neutron stars or black holes. Physicists liken gravity waves to the waves generated when a stone is thrown into a pond.

But, it’s not just gravitational waves that emerged out of the neutron star merger. The merger, known as GW170817, also generated a kilonova — a massive explosion that is much brighter than a regular nova but less so than a supernova. This was the first time that this type of nova was ever witnessed.

Scientists had suspected for some time that heavier elements may be forged during neutron star collisions. In a new study published in Nature, astronomers used ESO’s X-shooter spectrograph on the Very Large Telescope (VLT) to look for signatures of such elements in the kilonova.

Astronomers recorded a series of spectra from the ultraviolet to the near-infrared, which, when analyzed, revealed the presence of strontium.

Strontium is naturally found in the soil and some minerals. It’s what gives fireworks their dazzling red color.

To make strontium, other atoms need to be bombarded very rapidly with a huge number of neutrons under high pressure and temperature. The process, known as rapid neutron capture, needs to happen fast enough for an atomic nucleus to capture some of the neutrons before they decay in order to produce very heavy elements.

    “By reanalysing the 2017 data from the merger, we have now identified the signature of one heavy element in this fireball, strontium, proving that the collision of neutron stars creates this element in the Universe,” says the study’s lead author Darach Watson from the University of Copenhagen in Denmark.

    “This is the final stage of a decades-long chase to pin down the origin of the elements,” says Watson. “We know now that the processes that created the elements happened mostly in ordinary stars, in supernova explosions, or in the outer layers of old stars. But, until now, we did not know the location of the final, undiscovered process, known as rapid neutron capture, that created the heavier elements in the periodic table.”

This montage of spectra taken using the X-shooter instrument on ESO’s Very Large Telescope shows the changing behavior of the kilonova in the galaxy NGC 4993 over a period of 12 days after the explosion was detected on 17 August 2017. Each spectrum covers a range of wavelengths from the near-ultraviolet to the near-infrared and reveals how the object became dramatically redder as it faded. Credit: ESO.

This kind of research is still in its infancy. There is still much to learn about how neutron stars merge and their subsequent kilonovae. In the future, by analyzing more such events, astronomers hope to identify other heavy elements.

    “This is the first time that we can directly associate newly created material formed via neutron capture with a neutron star merger, confirming that neutron stars are made of neutrons and tying the long-debated rapid neutron capture process to such mergers,” says Camilla Juul Hansen from the Max Planck Institute for Astronomy in Heidelberg, who played a major role in the study.

    “We actually came up with the idea that we might be seeing strontium quite quickly after the event. However, showing that this was demonstrably the case turned out to be very difficult. This difficulty was due to our highly incomplete knowledge of the spectral appearance of the heavier elements in the periodic table,” says University of Copenhagen researcher Jonatan Selsing, who was a key author on the paper.


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« Reply #2147 on: Nov 11, 2019, 04:37 AM »

Titan’s sand dunes could be caused by cosmic rays

These findings will have unprecedented implications for the next space mission to Titan.

ZME
11/11/2019

Saturn’s largest moon has long intrigued scientists as its chemical composition is believed to mirror that of our own primordial planet. Now, thanks to new data obtained by researchers by the University of Hawaii (UH) at Manoa, we might be able to provide some answers to key question’s about Titan’s surface.

The team, led by physical chemist Ralf I. Kaiser, examined remote sensing data from NASA’s Cassini-Huygens mission to Titan to study its huge swathes of desert which are covered in sand dunes. These dunes stretch across the moon’s equatorial region in a space over 10 million kilometers (6,213,712 miles) and reach heights of up to about 100 meters in some places — think Egyptian pyramids tall.

The UH Manoa team exposed acetylene ice — a chemical that is used on Earth in welding torches and exists at Titan’s equatorial regions — at low temperatures to proxies of high-energy galactic cosmic rays.
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    “Titan’s dunes represent the dominating surface sink of carbon in Titan’s organic chemistry,” said Matthew Abplanalp, former chemistry graduate student at UH’s W.M. Keck Research Laboratory in Astrochemistry, and current researcher at the Naval Air Warfare Center Weapons Division at China Lake. “Therefore, unraveling the origin and chemical pathways to form this organic dune material is vital not only to understand Titan’s chemical evolution, but also to grasp how alike the chemistries on Titan and on Earth might have been like before life emerged on Earth 3.5 million years ago.”

The UH researchers exposed a rapid cosmic-ray-driven chemistry which converts simple molecules like acetylene to more complex organic molecules like benzene and naphthalene, a compound which is found in mothballs, but hopefully without the scent.

These findings will have unprecedented implications for the next space mission to Titan. In 2034, the three‐meters‐long Dragonfly rotorcraft will land in the ‘Shangri‐La’ dune‐fields near the moon’s equator. From there, it will use 1its eight rotors to traverse dozens of sites across Titan’s surface, taking samples and performing analysis. The purposes of the mission is to search for alien life and its molecular precursors.

    “Overall, this study advances our understanding of the complex organics and fundamental chemical processing of simple molecules in deep space and provides a scientifically sound and proven mechanism of formation of aromatic structures in extreme environments in low temperature ices,” Kaiser concluded. “Since Titan is nitrogen-rich, the incorporation of nitrogen in these PAHs may also lead to carbon-nitrogen moieties (parts of a molecule) prevailing in contemporary biochemistry such as in DNA and RNA-based nitrogen-bases.”

Discovered in 1655 by the Dutchman Christiaan Huygens, Titan is located approximately 760,000 miles (1,223,101 kilometers) from Saturn. Cassini showed us that Titan’s surface has lakes, rivers, and even seas of liquid ethane and methane (the main component of natural gas), as well as vast expanses of sand dunes. Its climate is such that the methane can form clouds and even rain, as water does here on Earth. The moon’s atmosphere is four times denser than ours and its gravity is approximately 1/7th of Earth’s. Because it is so far from the Sun, Titan’s surface temperature hovers around a chilly ‐290 degrees Fahrenheit (‐179 degrees Celsius).


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« Reply #2148 on: Nov 12, 2019, 04:37 AM »

Could wormholes actually exist?

A new study describes a technique that could be used to find wormholes.

Jordan Strickler
ZME
11/12/2019

In the move Interstellar, former NASA pilot Joseph Cooper (Matthew McConaughey) is sent hurtling through time and space via a wormhole in order to save humanity. Essentially, humans have screwed up this planet to the extent that in order to survive, we all have to move to a less-screwed-up planet. The quickest way to this new future home is through a wormhole near Saturn. This opening is the entrance to a distant galaxy located near a black hole named Gargantua. And, of course, if anyone can do it, it’s the bad-ass McConaughey.

Wormholes have always been the fascinating stuff of sci-fi, because come on, intertwining dimensions by bending space and time is pretty cool. Unfortunately, they’ve never been proven to actually exist. Luckily, however, that hasn’t put off scientists from trying. Now a new study out of the University of Buffalo (UB) has attempted to take a look at what they would look like if they were real.

Obviously, the first place you would look for a wormhole would be a black hole or a binary black hole system, which involves two black holes circling one another. Theoretically, the insane amount of gravity would pull them together and create a tunnel.

For their study, the researchers focused on Sagittarius A*, an object that’s thought to be a supermassive black hole at the heart of the Milky Way galaxy. While there’s no evidence of a wormhole there, it’s a good place to look for one because wormholes are expected to require extreme gravitational conditions, such as those present at supermassive black holes.

Black holes are massive pits of gravity that will bend space-time due to their incredibly dense centers, or singularities. When a massive star dies, it collapses inward, and as it does so, the star explodes into a supernova — a catastrophic expulsion of its outer material. This dying star will continue to collapse until it becomes either a neutron star or a singularity — something consisting of zero volume and infinite density. This seemingly impossible contradiction is what causes a black hole to form.

The UB scientists believed that if a wormhole does exist at Sagittarius A, nearby stars would be influenced by the gravity of stars at the other end of the passage. As a result, it would be possible to detect the presence of a wormhole by searching for small deviations in the expected orbit of stars near Sagittarius A.

    “If you have two stars, one on each side of the wormhole, the star on our side should feel the gravitational influence of the star that’s on the other side. The gravitational flux will go through the wormhole,” says Dejan Stojkovic, PhD, cosmologist and professor of physics in UB’s College of Arts and Sciences. “So if you map the expected orbit of a star around Sagittarius A*, you should see deviations from that orbit if there is a wormhole there with a star on the other side.”

The research, which was published in Physical Review D, focuses on how scientists could hunt for a wormhole by looking for perturbations in the path of S2, a star that astronomers have observed orbiting Sagittarius A*.

While current surveying techniques are not yet precise enough to reveal the presence of a wormhole, Stojkovic says that collecting data on S2 over a longer period of time or developing techniques to track its movement more precisely would make such a determination possible. These advancements aren’t too far off, he says, and could happen within one or two decades.

The good doctor cautions, however, that although this new method might be used to detect a wormhole if one is there, it will not strictly prove that a wormhole is present.

    “When we reach the precision needed in our observations, we may be able to say that a wormhole is the most likely explanation if we detect perturbations in the orbit of S2,” he says. “But we cannot say that, ‘Yes, this is definitely a wormhole.’ There could be some other explanation, something else on our side perturbing the motion of this star.”

Wormholes were originally conceived in 1916 by Ludwig Flamm. The Austrian physicist was reviewing another physicist’s solution to the equations in Albert Einstein’s theory of general relativity when he believed another solution might, in fact, be possible. His “white hole” was a theoretical time reversal of a black hole. Entrances to both black and white holes could be connected by a space-time conduit.

Though, if we ever do find one, it probably won’t be the one that science fiction has shown us.

    “Even if a wormhole is traversable, people and spaceships most likely aren’t going to be passing through,” says Stojkovic . “Realistically, you would need a source of negative energy to keep the wormhole open, and we don’t know how to do that. To create a huge wormhole that’s stable, you need some magic.”


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« Reply #2149 on: Nov 13, 2019, 04:38 AM »

Researchers may have spotted the smallest dwarf planet in the solar system

Small but significant

Alexandru Micu
ZME
11/13/2019

The European Space Observatory’s SPHERE instrument has spotted what may be the smallest small planet in our solar system.

The object christened Hygiea is currently considered an asteroid — but it might be classified as a dwarf planet. It’s the fourth largest body in the asteroid belt after Ceres, Vesta, and Pallas. The reclassification follows on the heels of new observations: for the first time, astronomers were able to look at Hygiea with a sufficiently-high resolution to study its surface and to determine that it is spherical (a condition necessary to be considered a planet).

Hygiea might thus officially become the smallest dwarf planet in our solar system — a title currently held by Ceres,

    “Thanks to the unique capability of the SPHERE instrument on the VLT (Very Large Telescope), which is one of the most powerful imaging systems in the world, we could resolve Hygiea’s shape, which turns out to be nearly spherical,” says lead researcher Pierre Vernazza from the Laboratoire d’Astrophysique de Marseille in France.

    “Thanks to these images, Hygiea may be reclassified as a dwarf planet, so far the smallest in the Solar System.”

Prior to this discovery, we already knew that Hygiea satisfied three of the four requirements to be considered a dwarf planet: it orbits around the Sun, it is not a moon, and it has not cleared the neighborhood around its orbit (like a proper planet would). The final requirement is for it to have enough gravitational force to pull itself into a roughly spherical shape. Thanks to new observations, we now know that Hygiea passes this criterion as well.

Based on the SPHERE data, the team estimated Hygiea’s size to be around 430 km in diameter. Ceres is closer to 950 km in diameter while Pluto, the largest dwarf planet, comes close to 2400 km.

One surprising find was that Hygiea lacks any large impact craters on its surface. The team really expected to find such a structure on its surface as Hygiea is the main member of one of the largest asteroid families (with around 7000 members) that all come from the same parent body. It was believed that Hygiea would have been left scarred by the event that led to that original body breaking apart. Although the astronomers observed Hygiea’s surface with a 95% coverage, they could only identify two relatively small craters.

    “This result came as a real surprise as we were expecting the presence of a large impact basin, as is the case on Vesta,” says Vernazza.

    “Neither of these two craters could have been caused by the impact that originated the Hygiea family of asteroids whose volume is comparable to that of a 100 km-sized object. They are too small,” explains study co-author Miroslav Bro of the Astronomical Institute of Charles University in Prague, Czech Republic.

Computer simulations suggest that Hygiea’s shape and the large number of members in its asteroid family were the result of a major head-on collision between the parent body and an object between 75 and 150 km in diameter around 2 billion years ago, The simulations showed that this violent impact completely shattered the parent body. Hygiea, the simulations suggest, is the product of left-over pieces that reassembled themselves into a round shape surrounded by companion asteroids.

    “Such a collision between two large bodies in the asteroid belt is unique in the last 3-4 billion years,” says Pavel Ševeček, a PhD student at the Astronomical Institute of Charles University and paper co-author.

    “Thanks to the VLT and the new generation adaptive-optics instrument SPHERE, we are now imaging main belt asteroids with unprecedented resolution, closing the gap between Earth-based and interplanetary mission observations,” Vernazza concludes.

The paper “A basin-free spherical shape as outcome of a giant impact on asteroid Hygiea” has been published in the journal Nature Astronomy.


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« Reply #2150 on: Nov 14, 2019, 04:39 AM »

New dark energy experiment may solve one of the universe’s greatest mysteries

Will we have to rewrite Einstein's theory of gravity? The DESI experiment could find out

ZME
11/14/2014

As an astronomer, there is no better feeling than achieving “first light” with a new instrument or telescope. It is the culmination of years of preparations and construction of new hardware, which for the first time collects light particles from an astronomical object. This is usually followed by a sigh of relief and then the excitement of all the new science that is now possible.

On October 22, the Dark Energy Spectroscopic Instrument (DESI) on the Mayall Telescope in Arizona, US, achieved first light. This is a huge leap in our ability to measure galaxy distances – enabling a new era of mapping the structures in the universe. As its name indicates, it may also be key to solving one of the biggest questions in physics: what is the mysterious force dubbed “dark energy” that makes up the 70% of the universe?

The cosmos is clumpy. Galaxies live together in groups of a few to tens of galaxies. There are also clusters of a few hundreds to thousands of galaxies and superclusters that contain many such clusters.
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This hierarchy of the universe has been known from the first maps of the universe, which looked like a “stickman” in graphs by the pioneering Centre for Astrophysics (CfA) Redshift Survey. These striking images were the first glimpse of large-scale structures in the universe, some spanning hundreds of millions of light years across.

The CfA survey was laboriously constructed one galaxy at a time. This involved measuring the spectrum of the galaxy light – a splitting of the light by wavelength, or colour – and identifying the fingerprints of certain chemical elements (mostly hydrogen, nitrogen and oxygen).

These chemical signatures are systematically shifted to longer redder wavelengths due to the expansion of the universe. This “red shift” was first detected by the astronomer Vesto Slipher and gave rise to the now famous Hubble’s Law – the observation that more distant galaxies appear to be moving away at a faster rate. This means that galaxies that are close by appear to be moving away relatively slowly by comparison – they are less redshifted than galaxies far away. Therefore, measuring the redshift of a galaxy is a way to measure its distance.

Crucially, the exact relationship between redshift and distance depends on the expansion history of the Universe which can be calculated theoretically using our theory of gravity and our assumptions of the matter and energy density of the universe.

All these assumptions were ultimately tested at the turn of the century with the combination of new observations of the universe, including new 3D maps from larger redshift surveys. In particular, the Sloan Digital Sky Survey (SDSS) was the first dedicated redshift survey telescope to measure over a million galaxy redshifts, mapping the large scale structure in the universe to unprecedented detail.

The SDSS maps included hundreds of superclusters and filaments and helped make an unexpected discovery – dark energy. They showed that the matter density of the universe was much less than expected from the Cosmic Microwave Background, which is the light left over from the Big Bang. That meant there must be an unknown substance, dubbed dark energy, driving an accelerated expansion of the Universe and become increasingly devoid of matter.

The puzzle

The combination of all these observations heralded a new era of cosmological understanding with a universe consisting of 30% matter and 70% dark energy. But despite the fact that most physicists have now accepted that there is such a thing as dark energy, we still do not know its exact form.

There are several possibilities though. Many researchers believe that the energy of the vacuum simply has some particular value, dubbed a “cosmological constant”. Other options include the possibility that Einstein’s hugely successful theory of gravity is incomplete when applied on the huge scale of the entire universe.

New instruments like DESI will help take the next step in resolving the mystery. It will measure tens of millions of galaxy redshifts, spanning a huge volume of the universe up to ten billion light years from Earth. Such an amazing, detailed map should be able to answer a few key questions about dark energy and the creation of the large scale structures in the universe.

For example, it should be able to tell us if dark energy is just a cosmological constant. To do this it will measure the ratio of pressure that dark energy puts on the universe to the energy per unit volume. If dark energy is a cosmological constant, this ratio should be constant in both cosmic time and location. For other explanations, however, this ratio would vary. Any indication that it is not a constant would be revolutionary and spark intense theoretical work.

DESI should also be able to constrain, and even kill, many theories of modified gravity, possibly providing an emphatic confirmation of Einstein’s Theory of General Relativity on the largest scales. Or the opposite – and again that would spark a revolution in theoretical physics.

Another important theory that will be tested with DESI is Inflation, which predicts that tiny random quantum fluctuations of energy density in the primordial universe were exponentially expanded during a short period of intense growth to become the seeds of the large scale structures we see today.
 
A team at a vendor in Santa Rosa Calif poses behind a DESI lens. VIAVI Solutions

DESI is only one of several next generation dark energy missions and experiments coming in the next decade, so there’s certainly reason to be optimistic that we could soon solve the mystery of dark energy. New satellite missions like Euclid, and massive ground based observatories like the Large Synoptic Survey Telescope, will also offer insights.

There will also be other redshift instruments like DESI including 4MOST at the European Southern Observatory. Together, these will provide hundreds of millions of redshifts across the whole sky leading to an unimaginable map of our cosmos.

It seems a long time ago now when I wrote my PhD thesis based on just 700 galaxy redshifts. It really goes to show it’s an exciting time to be an astronomer.

Bob Nichol, Professor of Astrophysics and Pro Vice-Chancellor (Research and Innovation), University of Portsmouth

This article is republished from The Conversation under a Creative Commons license. Read the original article.


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« Reply #2151 on: Nov 15, 2019, 04:23 AM »

Study on quantum mechanics suggests objective reality doesn’t exist

on November 15, 2019
By The Conversation
- Commentary

Alternative facts are spreading like a virus across society. Now it seems they have even infected science – at least the quantum realm. This may seem counter intuitive. The scientific method is after all founded on the reliable notions of observation, measurement and repeatability. A fact, as established by a measurement, should be objective, such that all observers can agree with it.

But in a paper recently published in Science Advances, we show that, in the micro-world of atoms and particles that is governed by the strange rules of quantum mechanics, two different observers are entitled to their own facts. In other words, according to our best theory of the building blocks of nature itself, facts can actually be subjective.

Observers are powerful players in the quantum world. According to the theory, particles can be in several places or states at once – this is called a superposition. But oddly, this is only the case when they aren’t observed. The second you observe a quantum system, it picks a specific location or state – breaking the superposition. The fact that nature behaves this way has been proven multiple times in the lab – for example, in the famous double slit experiment (see video below).

In 1961, physicist Eugene Wigner proposed a provocative thought experiment. He questioned what would happen when applying quantum mechanics to an observer that is themselves being observed. Imagine that a friend of Wigner tosses a quantum coin – which is in a superposition of both heads and tails – inside a closed laboratory. Every time the friend tosses the coin, they observe a definite outcome. We can say that Wigner’s friend establishes a fact: the result of the coin toss is definitely head or tail.

Wigner doesn’t have access to this fact from the outside, and according to quantum mechanics, must describe the friend and the coin to be in a superposition of all possible outcomes of the experiment. That’s because they are “entangled” – spookily connected so that if you manipulate one you also manipulate the other. Wigner can now in principle verify this superposition using a so-called “interference experiment” – a type of quantum measurement that allows you to unravel the superposition of an entire system, confirming that two objects are entangled.

When Wigner and the friend compare notes later on, the friend will insist they saw definite outcomes for each coin toss. Wigner, however, will disagree whenever he observed friend and coin in a superposition.

This presents a conundrum. The reality perceived by the friend cannot be reconciled with the reality on the outside. Wigner originally didn’t consider this much of a paradox, he argued it would be absurd to describe a conscious observer as a quantum object. However, he later departed from this view, and according to formal textbooks on quantum mechanics, the description is perfectly valid.

The experiment

The scenario has long remained an interesting thought experiment. But does it reflect reality? Scientifically, there has been little progress on this until very recently, when Časlav Brukner at the University of Vienna showed that, under certain assumptions, Wigner’s idea can be used to formally prove that measurements in quantum mechanics are subjective to observers.

Watch: https://www.youtube.com/watch?v=A9tKncAdlHQ&feature=emb_title

Brukner proposed a way of testing this notion by translating the Wigner’s friend scenario into a framework first established by the physicist John Bell in 1964. Brukner considered two pairs of Wigners and friends, in two separate boxes, conducting measurements on a shared state – inside and outside their respective box. The results can be summed up to ultimately be used to evaluate a so called “Bell inequality”. If this inequality is violated, observers could have alternative facts.

We have now for the first time performed this test experimentally at Heriot-Watt University in Edinburgh on a small-scale quantum computer made up of three pairs of entangled photons. The first photon pair represents the coins, and the other two are used to perform the coin toss – measuring the polarisation of the photons – inside their respective box. Outside the two boxes, two photons remain on each side that can also be measured.

Despite using state-of-the-art quantum technology, it took weeks to collect sufficient data from just six photons to generate enough statistics. But eventually, we succeeded in showing that quantum mechanics might indeed be incompatible with the assumption of objective facts – we violated the inequality!

The theory, however, is based on a few assumptions. These include that the measurement outcomes are not influenced by signals travelling above light speed and that observers are free to choose what measurements to make. That may or may not be the case.

Another important question is whether single photons can be considered to be observers. In Brukner’s theory proposal, observers do not need to be conscious, they must merely be able to establish facts in the form of a measurement outcome. An inanimate detector would therefore be a valid observer. And textbook quantum mechanics gives us no reason to believe that a detector, which can be made as small as a few atoms, should not be described as a quantum object just like a photon. It may also be possible that standard quantum mechanics does not apply at large length scales, but testing that is a separate problem.

This experiment therefore shows that, at least for local models of quantum mechanics, we need to rethink our notion of objectivity. The facts we experience in our macroscopic world appear to remain safe, but a major question arises over how existing interpretations of quantum mechanics can accommodate subjective facts.

Some physicists see these new developments as bolstering interpretations that allow more than one outcome to occur for an observation, for example the existence of parallel universes in which each outcome happens. Others see it as compelling evidence for intrinsically observer-dependent theories such as Quantum Bayesianism, in which an agent’s actions and experiences are central concerns of the theory. But yet others take this as a strong pointer that perhaps quantum mechanics will break down above certain complexity scales.

Clearly these are all deeply philosophical questions about the fundamental nature of reality. Whatever the answer, an interesting future awaits.The Conversation

By Alessandro Fedrizzi, Professor of Quantum Physics, Heriot-Watt University and Massimiliano Proietti, PhD Candidate of Quantum Physics, Heriot-Watt University

This article is republished from The Conversation under a Creative Commons license. Read the original article.


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« Reply #2152 on: Nov 16, 2019, 05:13 AM »


An asteroid as large as 2,000 feet across will speed past Earth later this month

Mike Wehner
BGR
11/16/2019

A large space rock known to scientists as 481394 (2006 SF6) will make its closest approach to Earth in just a couple of weeks. NASA scientists believe it will pass our lively little sphere on November 20th, coming within 0.029 astronomical units of Earth. That’s close enough that NASA considers the rock to be a potentially hazardous object, but it looks like it’s going to miss us this time around.

I know, 0.029 sure sounds like a close miss — and in the grand scheme of things, you could argue that it is — but astronomical units (au) are huge. 1au is the average distance between the Earth and our Sun, which is nearly 93 million miles. That means 2006 SF6 will still be around 2.7 million miles away from our planet when it passes by.

Researchers who have been tracking the path of the asteroid since its discovery over a decade ago believe the rock is roughly 1,000 to 2,000 feet wide. It’s not the kind of planet-killing space rock that you’d see in an end-of-the-world apocalypse flick, but it could still do some serious damage if it were on a collision course with Earth.

But before you go wringing your hands over this particular space rock, it’s worth remembering that this flyby is fairly mundane. The asteroid’s closest approach will still leave it over ten times farther away than the distance between Earth and the Moon. The most dangerous near-Earth objects pass by much closer, sometimes even within the Moon’s orbit of our planet.

2006 SF6 will remain at a relatively safe distance for now. It’ll be several hundred years before the rock comes this close again, so, for the time being, we won’t really have to worry about it.


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« Reply #2153 on: Nov 18, 2019, 04:49 AM »


Curiosity just sent back some haunting photos of Mars

Mike Wehner
BGR
11/18/2019

NASA’s trusty Curiosity rover has been chilling out on Mars for year over six years now. The bot regularly beams back images from the Red Planet, showcasing its towering peaks and vast valleys, and many of those photos feature the planet’s signature orange hue. Some of the latest images sent back by the rover aren’t nearly as colorful but are nonetheless stunning.

The latest mission update post by the Curiosity team features a shot of a geographical feature called Central Butte, located within the Gale Crater. Curiosity has called the crater home since its landing back in 2012, and the bot is slowly but surely scaling the area around the mountain called Mount Sharp.

The image is bleak, with the rocky terrain pushing upwards against a hazy sky. It’s a lonely image and a reminder of just how isolated Curiosity — and any robot that is sent to Mars — truly is.

It also provides a great look at the kind of terrain the rover has to tackle as it continues to travel across the Martian surface. Smooth rocks battered by dust and wind over millions of years are punctuated by smaller debris that could pose a threat to the rover’s already damaged wheels.

Despite the dangers, the rover continues to perform well. Geographical features like Central Butte provide scientists on Earth a clear look at the layering of the Mars landscape, revealing crucial details about how the planet’s surface has changed over time. As it slowly makes its way along, the rover’s science instruments return data on the chemical makeup of the rock and loose soil.

The Mars 2020 rover will be even better-equipped to tell scientists exactly what secrets the surface of Mars may be hiding, but Curiosity is far from finished. The rover’s nuclear power source can continue to provide power for well over a decade, and if the rover’s other systems remain functional we can expect it to continue exploring the planet for years to come.


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« Reply #2154 on: Nov 19, 2019, 04:36 AM »

Saturn moon Titan shaped by same forces as Earth

on November 19, 2019
By Agence France-Presse

The largest of Saturn’s many moons has lakes, mountains and dunes, with its surface scarred and crafted by many of the same forces which have shaped Earth, scientists said Monday.

A team led by Rosaly Lopes at the California Institute of Technology (Caltech) said Titan’s visible exterior was “one of the most geologically diverse in the Solar System.”

“Despite the differences in materials, temperatures and gravity fields between Earth and Titan, many of their surface features are similar and can be interpreted as products of the same geologic processes,” the scientists said in an article in Nature Astronomy.

Using radar and infra-red data generated by the now defunct Cassini probe, which completed a 20-year mission by crashing into Saturn in 2017, the scientists said they could fill in many of the gaps in mapping Titan, some 1.2 billion kilometres (800 million miles) from Earth.

Dunes and lakes, they said, were relatively young while mountainous terrain appeared older.

Titan’s surface was sculpted by the accumulation and erosion of sediment and showed “clear latitudinal variation, with dunes at the equator, plains at mid-latitudes and labyrinth terrains and lakes at the poles,” they said.

The region around the equator is arid, with Titan getting wetter closer to the poles.

Just as on Earth, Titan’s surface has been marked by impact craters, liquid- and air-driven erosion, methane-laden rainfall, tectonic plate movement and possible volcanic activity.

Alice Le Gall, one of the team and working at Paris-Saclay University, said Titan “is the only known extra-terrestrial body to have liquid bodies on its surface.”

Methane exists in three states — solid, liquid and gas — at super-cold temperatures. It produces a cycle similar to that of rain falling on Earth to form rivers and lakes, and then evaporating to form clouds again, Le Gall told AFP.


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« Reply #2155 on: Nov 20, 2019, 05:04 AM »


Nobody knows what’s creating oxygen on Mars

Mike Wehner
BGR
11/20/2019

NASA’s Curiosity rover returned some seriously surprising data to Earth earlier this year, with readings of elevated methane levels that were hard to explain. Subsequent tests attempted to pin down the cause of the higher-than-expected readings but scientists have yet to come up with a definitive answer.

Now, as questions about methane continue to swirl, scientists studying the behavior of gasses on Mars have noticed that oxygen on the Red Planet also acts much differently than it does on Earth. The observations were made in the Gale Crater, which the rover has called home since it landed there back in 2012.

Curiosity “breathes” the air on Mars and analyzes it to determine the levels of various types of gasses that are present. On Earth, the background levels of certain gasses rise and fall with seasons, and the same seems to be true on Mars, but only to a point.

The air on Mars is largely carbon dioxide. In fact, a full 95% of the gas Curiosity breathes in during its tests is CO2. The remaining 5% is a mix of nitrogen, argon, oxygen, and carbon monoxide. By plotting levels of these gasses over the course of a full Martian year, scientists have noticed anomalies with regard to the amount of oxygen, relative to other gasses.

NASA explains:

    Within this environment, scientists found that nitrogen and argon follow a predictable seasonal pattern, waxing and waning in concentration in Gale Crater throughout the year relative to how much CO2 is in the air. They expected oxygen to do the same. But it didn’t. Instead, the amount of the gas in the air rose throughout spring and summer by as much as 30%, and then dropped back to levels predicted by known chemistry in fall.

The fact that the oxygen levels vary as wildly as they do is significant because it hints at as-of-yet undiscovered processes at work on the surface of the planet. For the oxygen levels to see a significant upward spike and then a dramatically fall, something must be creating it and then another something is using it.

“We’re struggling to explain this,” Melissa Trainer of NASA’s Goddard Space Flight Center says. “The fact that the oxygen behavior isn’t perfectly repeatable every season makes us think that it’s not an issue that has to do with atmospheric dynamics. It has to be some chemical source and sink that we can’t yet account for.”

Before you start dreaming of a subterranean race of Martian monsters, it’s important to know that this isn’t a smoking gun for life on Mars. In fact, it’s far from it. There are natural processes that can generate oxygen in the absence of life, and since we have yet to find evidence of life on the Red Planet, yet can’t rule it out, scientists are considering all possible options.


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« Reply #2156 on: Nov 21, 2019, 04:57 AM »


China is going to Mars, and it just hit a major milestone

Mike Wehner
BGR
11/21/2019

All eyes have been on NASA’s Mars 2020 rover as the space agency prepares it to travel to the Red Planet midway through next year, but it’s not the only piece of high-tech hardware making such a trip. China is working hard on a Mars mission of its own, and it just completed a very important trial that suggests the Chinese space program is on schedule.

As CNN reports, the public test was conducted to demonstrate the ability of China’s new Mars lander to safely touch down on the surface of the planet. To ensure a soft landing, the spacecraft has to be capable of slowing its descent, hovering, and performing rapid alterations to its trajectory.

Aiming a spacecraft at Mars is really only half the battle, and once China’s mission reaches the Red Planet it’s going to have to find a safe spot within its landing zone. That means avoiding obstacles on the surface while decelerating to a speed that won’t lead to the destruction of the spacecraft once it reaches the ground.

To test this, the lander was suspended high above the ground at a test facility near Beijing. The spacecraft successfully hovered and then performed a controlled descent, but did not actually land on the ground below. This was apparently exactly what China’s engineers were hoping for, and they told an assembled group of reporters that the test was a success, though they didn’t provide additional details or take questions.

It’s a big step for China’s Mars ambitions, but there are still more hurdles standing between the country and a 2020 launch. The Chinese Long March 5 rocket that will put the spacecraft on a path toward Mars still has to pass a test before the end of the year in order for the mission to proceed, IEEE Spectrum reports. If it fails, the mission would have to be scrubbed for at least 26 months. This is due to the orbits of Earth and Mars


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« Reply #2157 on: Nov 22, 2019, 04:30 AM »


NASA’s adorable underwater rover might be the first to discover alien life

Mike Wehner
NGR
11/22/2019

NASA is about to put a rover to the test in Antarctica, and it’s unlike any robot the agency has ever shot into space. A far cry from the bulky, boxy Mars rovers Opportunity and Curiosity, the BRUIE rover looks almost like a toy by comparison. Its cutesy form factor belies its incredible potential to discover something that scientists have spent decades hunting for: Alien life on other worlds.

BRUIE — short for Buyant Rover for Under-Ice Exploration — is built for a very specific purpose. Its design allows it to crawl along the underside of an ice cap, fully submerged in incredibly chilly water. Antarctica is the perfect place to test such a bot, but its creators hope it will one day explore the waters of icy moons like Enceladus and Europa.

As scientists from NASA and other scientific institutions continue to search for life outside of Earth, moons like Enceladus and Europa appear to offer the best chance of finding it close to home. These frosty worlds are encased in ice, but their frozen shells are thought to hide vast oceans of liquid water.

“The ice shells covering these distant oceans serve as a window into the oceans below, and the chemistry of the ice could help feed life within those oceans,” Kevin Hand of NASA’s Jet Propulsion Laboratory explains. “Here on Earth, the ice covering our polar oceans serves a similar role, and our team is particularly interested in what is happening where the water meets the ice.”

Antarctica offers the opportunity to test BRUIE’s potential without having to leave Earth. During its trial run, the bot will be tasked with traveling along the underside of the ice while collecting data and capturing images. High-tech scientific instruments will be capable of reading the oxygen level of the water as well as temperature and salinity, all of which would be important information if we’re to adequately study otherworldly oceans.

There are no current plans to send BRUIE into space, but as the project continues and the robot evolves, it could find itself at the heart of new missions to our system’s icy moons.


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« Reply #2158 on: Nov 23, 2019, 05:15 AM »


Hibernation chambers might make space exploration a reality

Mike Wehner
BGR
11/23/2019

We’ve all seen it in sci-fi space movies: Deep-space travelers cruising to a new location and sleeping for weeks, months, or even years to pass the time. In fiction, hibernation pods are a convenient plot device, but would they work here in reality?

A new research effort by the European Space Agency suggests that if we can get the technology working as intended, placing astronauts into a state of suspended animation might actually be the best way to explore the cosmos. The benefits would be many, including the option to use a much smaller spacecraft for long-haul crewed missions.

There are many hurdles we still need to overcome before we could even think about sending humans to other planets, let alone other systems. Even if we figured out how to overcome things like space radiation and the toll of long-term low gravity on the human body, we’re still left with one major problem: Humans need living space and a lot of it.

When engineers dream up concepts for crewed spacecraft that could travel to distant locations they’re typically quite large. That’s because we need space to move around, exercise, and live our lives, regardless of whether or not we’re flying through space in a big metal cylinder. Sleeping astronauts require far less room to stretch their legs, so to speak, and that means a much smaller ship.

“We looked at how an astronaut team could be best put into hibernation, what to do in case of emergencies, how to handle human safety and even what impact hibernation would have on the psychology of the team,” Robin Biesbroek of ESA’s Concurrent Design Facility explains. “Finally we created an initial sketch of the habitat architecture and created a roadmap to achieve a validated approach to hibernate humans to Mars within 20 years.”

The team came up with a design that reduces the mass of a deep-space crew module by a third. This is largely thanks to the removal of crew living space that would no longer be needed, as well as a reduction in the supplies that would need to be carried along for the journey.

The design assumes a lot of technological advancements that, put simply, just don’t exist yet. That includes the ability to safely place a human into a state of hibernation and slow down their metabolism by as much as 75%. This comes naturally to animals who hibernate, but humans aren’t one of them. Additionally, the crew would need time to recover after waking up, and that could mean spending weeks in cramped quarters of a shrunken ship.

We still have some time to figure it all out, of course, but it’s incredibly interesting that a concept dreamt up by science fiction writers decades ago may end up being the best solution to exploring other worlds.


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« Reply #2159 on: Nov 25, 2019, 04:14 AM »


Daring Mars mission to send rocks back to Earth in hunt for past life

Europe poised to join US in complex plan to find evidence of fossil microbes on red planet

Robin McKie
Guardian
25 Nov 2019 09.03 GMT

Engineers plan to collect rocks on Mars and bring samples to Earth, in one of the most complex robot space projects envisaged. The scheme, being developed by Nasa and the European Space Agency (Esa), will involve robot rovers finding rocks that might contain evidence of past life.

The samples would be blasted into space, intercepted by an unmanned spacecraft, and dropped by parachute in the Utah desert, with the 500g of Martian soil and rock shared with researchers round the world.

Nasa recently gave outline approval for such a mission – which will cost billions of pounds – and research ministers from Esa’s member states will meet in Seville this week to decide if they will support it. The UK is a leading partner in Esa, and its membership is unconnected to Brexit.

“The Mars Sample Return is a key part of our future exploration programme, and I very much hope Europe’s science ministers will back it,” Jan Wörner, Esa’s director general, said last week. “However, we should be clear that every step of the mission is going to be very challenging.”

Scientists are keen to study Martian rock as conditions on the red planet billions of years ago were similar to those on Earth. It had a thick atmosphere and running water on its surface. Today, most of its atmosphere has gone and researchers want to know if life evolved before that. Hence their search for fossil microbes.

“We have only two ways to study Martian soil and rock at present,” said Open University astrobiologist Susanne Schwenzer. “We can send probes to Mars and analyse rock samples there or we can study bits of Mars that arrive on Earth as meteorites.”

But space probes are constrained by power supplies, data storage, the harsh Martian environment, the need to miniaturise equipment, and difficulties in landing on Mars.

By contrast, studying meteorites – bits of rock blasted into space when larger meteorites have struck Mars and thrown up debris – poses different problems. Schwenzer said: “They often get contaminated after their arrival on Earth and it is not known where on Mars they originated.”

The answer, say scientists, is to bring Martian rock and soil to Earth, to study it using the world’s most advanced laboratory equipment.

The mission will start by using the new Nasa Mars 2020 rover, which is set to land in Jezero crater in the Syrtis Major region of Mars in early 2021.

“Mars 2020 will collect soil samples, put them in small metal tubes, then seal them,” said Sanjay Vijendran, a lead member of Esa’s Mars Sample Return team. “Caches of these tubes will then be left at designated sites on the Martian surface.”

Then a second craft to be built by Esa, known as a fetch rover, will land on Mars, trundle round these sites, and load the samples into a football-sized canister. This will be taken to a US rocket that will blast the container into orbit round Mars.

A robot spaceship called the Earth-return orbiter will sweep round Mars, capture the canister, then head back to Earth, before releasing the capsule so that it lands on the Utah desert.

Lewis Dartnell, an astrobiologist at the University of Westminster, London. said: “The mission involves an incredibly complex sequence of manoeuvres, and there’s so much that could go wrong. However, if we want to find evidence that there was once life on Mars, this is the sort of thing we are going to have to do. It will be worth the effort.”

    If we want to find evidence of life on Mars this is what we need to do. It will be worth the effort
    Professor Lewis Dartnell

The prospect of finding past life on Mars excites scientists. However, there is also a chance that life still exists there. So researchers will have to take considerable care that the capsule does not carry potentially dangerous micro-organisms.

“It is extremely unlikely that we will bring back living organisms, and even if we do, it is unlikely they will be harmful,” said Vijendran. “However, we cannot take that for granted, and every measure to make sure the samples are sealed and pose no threat to the planet will be taken.”

Protective measures will include ensuring that the return capsule can withstand impact on Earth, even if its parachute fails. The samples will be handled only in laboratories that possess Biosafety Level 4 containment facilities, the most secure available to biological researchers at present.


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