Discovery of expanding cosmos

Move over, Hubble: Discovery of expanding cosmos assigned to little-known Belgian astronomer-priest

By Daniel Clery | Oct. 29, 2018 , 3:45 PM

Hubble’s Law, a cornerstone of cosmology that describes the expanding universe, should now be called the Hubble-Lemaître Law, following a vote by the members of the International Astronomical Union (IAU), the same organization that revoked Pluto’s status as a planet. The change is designed to redress the historical neglect of Georges Lemaître, a Belgian astronomer and priest who in 1927 discovered the expanding universe—which also suggests a big bang. Lemaître published his ideas 2 years before U.S. astronomer Edwin Hubble described his observations that galaxies farther from the Milky Way recede faster.

The final tally of the 4060 cast votes, announced today by IAU, was 78% in favor of the name change, 20% against, and 2% abstaining. But the vote was not without controversy, both in its execution and the historical facts it was based on. Helge Kragh, a historian of science at the Niels Bohr Institute in Copenhagen, calls the background notes presented to IAU members “bad history.” Others argue it is not IAU’s job to rename physical laws. “It’s bad practice to retroactively change history,” says Matthias Steinmetz of the Leibniz Institute for Astrophysics in Potsdam, Germany. “It never works.”

Piero Benvenuti of the University of Padua in Italy, who stepped down as IAU general secretary in August, proposed the change last year because, he says, “historically, it felt not right.” In 1927 Lemaître calculated a solution to Albert Einstein’s general relativity equations that indicated the universe could not be static but was instead expanding. He backed up that claim with a limited set of previously published measurements of the distances of galaxies and their velocities, calculated from their Doppler shifts. However, he published his results in French, in an obscure Belgian journal, and so they went largely unnoticed.

In 1929, Hubble published his own observations showing a linear relationship between velocity and distance for receding galaxies. It became known as Hubble’s Law. “Hubble was clearly involved, but was not the first,” says astronomer Michael Merrifield of the University of Nottingham in the United Kingdom. “He was good at selling his story.”

The text of the IAU resolution, circulated to members ahead of the vote, asserts that Hubble and Lemaître met in 1928, at an IAU general assembly in Leiden, the Netherlands—between the publication of their two papers—and “exchanged views” about the blockbuster theory. Kragh says that meeting “almost certainly didn’t take place” and that IAU’s statement “has no foundation in documented history.” Benvenuti counters that historians know from comments from Hubble’s assistant that he returned very excited from Leiden and began to gather more data. “Who else could have talked to Hubble about this problem but Lemaitre?” Benvenuti asks.

The resolution has also come under fire for confusing two different issues: the expansion of the universe and the distance-velocity relation for galaxies, which is also known as the Hubble constant. Hubble never claimed to have discovered cosmic expansion, but did do much of observing work to nail down how fast the universe was expanding. “If the law is about the empirical relationship, it should be Hubble’s Law,” Kragh says. “If it is about cosmic expansion, it should be Lemaître’s Law.”

Members have also criticized IAU over the way the vote was conducted. Traditionally, IAU resolutions are debated at general assemblies, once every 3 years, and decided by a show of hands of attending members. But such a straw poll led to the unpopular 2006 vote that reclassified Pluto as a dwarf planet. “The IAU got badly burned over the Pluto thing,” Merrifield says. As a result, IAU introduced the provision of having an online vote of the whole 11,000 membership.

In the case of Hubble’s Law, attendees at the August general assembly in Vienna were frustrated by a very short debate, followed by a straw poll (74% in favor of the name change). The IAU executive committee invited others to submit questions electronically and launched the online vote at the beginning of October. Merrifield says there was not enough time and opportunity for debate. “The IAU presented the issue as neat and tidy, but it is a much more murky and messy tale,” he says. He says several other researchers could have a claim because they were also working on cosmic expansion and galaxy motion at the time.

A final concern is whether IAU is within its rights to weigh in on historical affairs. “There is no mandate to name physical laws,” Steinmetz says. IAU has acknowledged this and is only recommending the use of the term Hubble-Lemaître Law. Will it catch on? “No, I don’t think so,” Kragh says. “Hubble Law is ingrained in the literature for most of a century.”

In any event, says Merrifield, “It doesn’t matter all that much, really.”

Hverken Hubble eller Lemaître målte en eneste galakses radialhastighed. Alle astronomer vidste, at de anvendte radialhastigheder var målt af

Vesto Melvin Slipher

Lemaître var teoretiker, ikke en observerende astronom. Når han i den omtalte “obskure” artikkel finder den samme værdi for H0 som Hubble to år senere skyldes det, at han var i besiddelse af en liste med Hubbles afstandsbestemmelser. Sammenhængen mellem radialhastigheder og afstande viste ikke entydigt en lineær relation. Den kunne godt være kvadratisk. Hubble mente ikke, at den lineære relation var et bevis på, at Universet ekspanderede.

Det er efterhånden blevet kontroversielt hver gang IAU vedtager en resulution vedrørende et historisk emne.

Jeg vil derfor skrive lidt om de to forskellige versioner af den naturvidenskabelige metode:

  1. Den induktive metode, som finder en oftest lineær sammenhæng mellem to observerede størrelser. En sådan sammenhæng kaldes en “lov”, hvis sandhedsværdi beror på, at sammenhængen skal kunne gentages ved nye målinger. Der er ikke tale om en årsag/virkning-sammenhæng.
  2. Den deduktive metode, som ud fra nogle få fysiske principper udleder en matematisk model for nogle fysiske størrelser ud fra nogle begyndelsesbetingelser.

Teknisk set hører Hubbles lov hjemme under den induktive metode, hvorimod ideen om Universets ekspansion hører hjemme under den deduktive metode. Den deduktive metode kaldes også en teori.

Nu er rene kosmologiske målinger ofte så usikre, at de ikke kan stå alene. De kombineres næsten altid med den deduktive metode i form af en teori.

Lemaître fandt, at et ekspanderende univers medfører en lineær relation mellem afstand og rødforskydning. Lemaître fortalte i 1927 Einstein om denne lineære relation. Einstein fandt, at ideen var en matematisk mulighed, men en fysisk afskyelig tanke.

Einstein lægger meget mere vægt på fysisk intuition end på astronomiske observationer. Han var således overbevist om, at de lokale naturlove var bestemt af de fjerne massers indflydelse. Et ekspanderende univers ville åbne op for variable naturlove. Denne samme frygt var baggrunden for den senere “steady state”-teori.

Einstein blev først modstræbende overbevist om Universets ekspansion i 1933.

Hubbles lov ville aldrig være blevet godtaget, hvis det ikke havde været for Lemaîtres teoretiske udledning af loven, samt beviset for, at Einsteins statiske univers er ustabilt.

 

Ginzburg-Landau Dark Energy

Ginzburg-Landau Theory of Dark Energy: A Framework to Study Both Temporal and Spatial Cosmological Tensions Simultaneously

Abdolali Banihashemi, Nima Khosravi, Amir H. Shirazi

A dark energy model (DE) is proposed based on Ginzburg-Landau theory of phase transition (GLT). This model, GLTofDE, surprisingly provides a framework to study not only temporal tensions in cosmology e.g. H0 tension but also spatial anomalies of CMB e.g. the hemispherical asymmetry, quadrupole-octopole alignment and its orthogonality to dipole simultaneously. In the mean field approximation of GLTofDE, the potential is broken spontaneously. We modeled this transition and showed that GLTofDE can resolve both the H0 tension and Lyman-α anomaly in a non-trivial way. According to a χ2-analysis the transition happens at zt=0.746+0.028-0.039 while H0=73.5±1.1 km/s/Mpc and Ωk=-0.196+0.049-0.033 which are consistent with the latest H(z) reconstructions. In addition, the GLTofDE proposes a framework to address the CMB anomalies when it is considered beyond the mean field approximation. In this regime existence of a long wavelength mode is a typical consequence which is named the Goldstone mode in the case of continuous symmetries. This mode, which is an automatic byproduct in GLTofDE, makes different directions of the sky see different cosmological constants. This means one side of the sky should be colder than the other side which can describe observed dipole in CMB. In addition between initial stochastic pattern and the final state with one long wavelength mode, we can observe smaller patches or protrusions of the biggest remaining patch in the simulation. Our simulations show these protrusions are few in numbers and will be evolved according to Alan-Cahn mechanism. These protrusions can give an additional effect on CMB which is the existence of aligned quadrupole-octopole mode and its direction should be orthogonal to the dipole direction. We conclude that GLTofDE is a very rich framework both theoretically and phenomenologically.

 

Stemmelighed for to projekter

Usandsynligt resultat giver liv til SDU-forskers Mars-projekt

I 2020 sender NASA en ekspedition til Mars for at finde tegn på liv. SDU-forsker kan være med til at bestemme, hvad der skal ledes efter.

En SDU-forsker er med i kapløbet om at bestemme, hvor på Mars NASA skal lande, og hvilke former for liv, man skal lede efter, når de sender en stor ekspedition afsted til planeten i 2020.

Det blev besluttet natten til fredag, da NASA skulle vælge mellem fire projekter.

Men i stedet for én vinder endte man med et uafgjort resultat, og det kom bag på Magnus Ivarsson, der forsker i mikrobiologi på Syddansk Universitet.

– Jeg har lige fået besked fra Californien om, at der var stemme-lighed mellem vores projekt og et andet. For at være ærlig, så var det overraskende. Lige nu ved vi slet ikke, hvor den specifikke destination på Mars bliver, fortæller han til DR Fyn.

NASA havde bedt forskere over hele verden om at byde ind med projekter.

Siden 2014 er projekterne gradvist blevet kasseret, og nu er man altså nede på to. Heriblandt altså Magnus Ivarssons.

Han havde dog ikke regnet med, at dét ville blive resultatet. Faktisk troede han, at en sejr var lysår væk.

– Jeg havde ikke forventet, at vores projekt ville vinde. Det burde jeg måske ikke sige, men jeg er virkelig glad for, at vi stadig er med i kapløbet. Over de seneste år har diskussionerne i den videnskabelige verden handlet om et andet projekt. Så jeg er meget glad for, at det lykkedes os at overbevise dommerkomiteen.

Svampe eller vand?

Mens de tre øvrige projekter koncentrerede sig om at finde spor af vand på ‘den røde planet’, er planen for Magnus Ivarsson og hans arbejdsgruppe at finde spor efter mikroorganismer, som eksempelvis svampe, der lever dybt nede under planetens overflade.

– Hvis der nogensinde har været liv på Mars, tror vi, at det har været dybt nede under overfladen. Det sted, vi har foreslået, gør det muligt at undersøge de dybe klipper, forklarer han.

Tidligere er det blandt andet lykkedes Magnus Ivarsson at finde organismer, der lever helt uden ilt, i en svensk klippehule 600 meter under jordens overflade.

Nu er drømmen så et skridt tættere på at blive til virkelighed for ham.

– Det føles godt, men det er også meget forvirrende, for vi ved ikke, hvad der kommer til at ske, siger Magnus Ivarsson.

Den endelige beslutning skal tages af NASA’s øverste ledelse. Hvornår det sker, vides endnu ikke.

Projektet er beskrevet her:

Paleo-Rock-Hosted Life on Earth and the Search on Mars: a Review and Strategy for Exploration

Man læser her, at andenforfatteren er Bethany Ehlmann, som er medlem af Mars 2020 science team:

NASA’s next Mars rover could explore former mineral springs and a fossil river delta

Det er korrekt, at NASA i mange år har undgået ordet “liv” for ikke at blive beskyldt for at spilde skatteborgernes penge på “små grønne marsmænd”.

 

Mars: Er der liv i rummet?

SDU-forsker med i kapløbet om at bestemme ruten til Mars

I nat besluttes det, hvilken af fire ruter, en stor NASA-ekspedition skal benytte, når de i 2020 sætter kursen mod Mars. SDU-forsker er med i opløbet.

En ubemandet NASA-ekspedition skal efter planen lande på Mars i 2020. Ekspeditionens mission er blandt andet at undersøge liv på planeten.

Men det er en dyr udskrivning at sende en ekspedition til Mars, og derfor er det vigtigt, at det allerede nu bliver besluttet, hvor man skal lande.

For at finde ud af hvor chancen er størst for at finde liv, har NASA allieret sig med professorer over hele verden.

De har givet deres bud på, hvor ekspeditionen skal lede, hvad de skal lede efter, og hvorfor de skal lede efter netop det.

En af dem, der stadig er med i kapløbet om at bestemme udformningen af ekspeditionen, er Magnus Ivarsson. Han er forsker fra Nordisk Center for Jordens Udvikling på Syddansk Universitet

– Vi tænker sådan her: Hvor har det været mest muligt for liv at opstå og overleve tidligt i Mars’ historie, og det er altså på vulkanlignede steder, forklarer han.

Magnus Ivarssons – og resten af hans arbejdsgruppes plan – går ud på at finde svampe på svært tilgængelige steder. Tidligere har han fundet og undersøgt mikroskopiske svampe i klippehuler langt under jordens overflade og på havbunden.

Eksempelvis er det engang lykkedes ham at finde organismer, der lever helt uden ilt i en svensk klippehule 600 meter under jordens overflade.

Mikroorganismerne lever dybt inde i bjerge i sprækker og revner, og på Mars findes der også bjerge, der ifølge professor er oplagte at undersøge nærmere.

– Det sted vi foreslår var for fire milliarder år siden dybt inde i Mars’ indre, men i dag er det blottet, og derfor kan man undersøge, hvordan mikroorganismerne så ud. Alt ser ud som dengang, siger han og fortsætter:

– Det er meget som står på spil nu. Der er fire bud tilbage, så vi venter spændt. Vi håber virkelig at vores plads bliver valgt.

I nat dansk tid besluttes det på en kongres i Los Angeles, hvilket bud NASA ekspeditionen vælger.

 

Paleo-Rock-Hosted Life

Paleo-Rock-Hosted Life on Earth and the Search on Mars: a Review and Strategy for Exploration

T.C. Onstott, B.L. Ehlmann, H. Sapers, M. Coleman, M. Ivarsson, J.J. Marlow, A. Neubeck, P. Niles

We review the abundance and diversity of terrestrial rock hosted life, the environments it inhabits, the evolution of its metabolisms, and its fossil biomarkers to provide guidance in the search for the biomarkers of rock hosted life on Mars. Key finds are metabolic pathways for chemolithotrophic microorganisms evolved much earlier in Earth history than those of surface dwelling phototrophic microorganisms,the emergence of the former occurred at a time when Mars was habitable, whereas that of the latter occurred at a time when the martian surface would have been uninhabitable, subsurface biomass do not correlate with organic carbon and tends to be highest at interfaces where chemical redox gradients are most pronounced, deep subsurface metabolic activity does not rely upon the respiration of organic photosynthate but upon the flux of inorganic energy and the abiotic and biotic recycling of metabolic waste products, and the rock record reveals examples of subsurface life back to 3.45 Ga with several examples of good preservation potential in rock types that are quite different from those preserving the photospheric supported biosphere.These findings suggest that rock hosted life would have likely to emerge and be preserved in a martian context. We thus propose a Mars exploration strategy that scales spatially, focusing initially on identifying rocks with evidence for groundwater flow and low temperature mineralization, then identifying redox and permeability interfaces preserved within rock outcrops, and finally focusing on finding minerals associated with redox reactions and traces of carbon and diagnostic biosignatures. The lessons from Earth show that ancient rock hosted life is preserved in the fossil record and confirmable via a suite of morphologic, organic, mineralogical and isotopic fingerprints and microscopic textures.

 

NASA’s next Mars rover

NASA’s next Mars rover could explore former mineral springs and a fossil river delta

By Paul Voosen |

Sometimes, a problem really can be solved by meeting halfway. For the past 4 years, planetary scientists have wrestled over where to send NASA’s next Mars rover, a $2.5 billion machine to be launched in 2020 that will collect rock samples for eventual return to Earth. Next week, nearly 200 Mars scientists will gather for a final landing site workshop in Glendale, California, where they will debate the merits of the three candidate sites that rose to the top of previous discussions. Two, Jezero and Northeast Syrtis, hold evidence of a fossilized river delta and mineral springs, both promising environments for ancient life. Scientists yearn to visit both, but they are 37 kilometers apart—much farther than any martian rover has traveled except Opportunity.

Now, the Mars 2020 science team is injecting a compromise site, called Midway, into the mix. John Grant, a planetary scientist at the Smithsonian Institution’s Center for Earth and Planetary Studies at the National Air and Space Museum in Washington, D.C., who co-leads the landing site workshops, says the team wanted to know whether a rover might be able to study the terrains found at Jezero and Northeast Syrtis by landing somewhere in the middle.

So far, the answer appears to be yes. The Mars 2020 rover borrows much from the design of the Curiosity rover that has been exploring another Mars site for 6 years. But it includes advances such as a belly-mounted camera that will help it avoid landing hazards during its harrowing descent to the surface. This capability allowed scientists to consider Midway, just 25 kilometers from Jezero and close enough to drive there. At the same time, Midway’s rocks resemble those of Northeast Syrtis, says Bethany Ehlmann, a planetary scientist at the California Institute of Technology (Caltech) in Pasadena and member of the Mars 2020 science team.

Midway and Northeast Syrtis both hail from a time, some 4 billion years ago, when Mars was warmer and wetter. Surveys from orbit suggest the sites harbor rocks that formed underground in the presence of water and iron, a potential food for microbes. The rocks, exposed on the flanks of mesas, include a layer of carbonate deposits that many scientists believe were formed by underground mineral springs. Sheltered from a harsh surface environment, these springs would have been hospitable to life, Ehlmann says. “We should go where the action was.”

Nearby Jezero crater has its own allure, etched on the surface: a fossilized river delta. Nearly 4 billion years ago, water spilled into the crater, creating the delta. “It’s right there,” says Ray Arvidson, a planetary geologist at Washington University in St. Louis, Missouri. “It’s beautiful.” Geologists know deltas concentrate and preserve the remnants of life; they can see that on Earth in offshore deposits of oil—itself preserved organic matter—fed by deltas like the Mississippi’s. New work to be presented at the workshop by Briony Horgan, a planetary scientist at Purdue University in West Lafayette, Indiana, will show that Jezero crater has a bathtub ring of carbonate—a strong sign that it once contained a lake. On Earth, such layers are often home to stromatolites, cauliflowerlike minerals created by ancient microbial life.

Right now, the Mars 2020 team favors landing at Jezero and driving uphill to Midway, says Matt Golombek, a planetary scientist at NASA’s Jet Propulsion Lab (JPL) in Pasadena, and the other workshop co-leader. For the past year, the team has scoured potential routes between the two. “We haven’t identified any deal-breakers,” says Ken Farley, the mission’s project scientist and a Caltech geologist. The rover’s advanced autonomous driving should allow it to cover more ground than Curiosity, which often stops to plan routes. Even so, the path from Jezero to Midway would take nearly 2 years, Farley says. That means the rover could explore only one site during its primary 2-year mission, when it must drill and store 20 rock cores, to be picked up by future sample return missions. Exploration of the second site would have to come during an extended mission, after the rover’s warranty expires. “The further away you land from your gold mine, the higher the risk you might not get there,” Arvidson says.

Left out of those plans is the last leading candidate site: Columbia Hills. “I have a sense there’s a hill to climb,” says the site’s chief advocate, Steven Ruff, a planetary scientist at Arizona State University in Tempe. “I’ll go in with a lot of questions of whether they can make that drive between Midway and Jezero.” Columbia Hills sits within the large Gusev crater that the Spirit rover explored from 2004 to 2010. Driving backward while dragging a bad front wheel, Spirit gouged a trench that revealed opaline silica, a mineral that on Earth is a sure sign of life-supporting hot springs. Ruff has even proposed that the martian silica deposits are stromatolites.

The engineers building Mars 2020 will be glad to settle on a destination, says Matt Wallace, the rover’s deputy project manager at JPL. The lab’s clean room is starting to fill up. The “sky crane” that will lower the rover to the surface is done. The spacecraft that will shepherd the rover to Mars is nearly complete—it just needs a heat shield, which is being rebuilt after testing revealed a crack. Several weeks ago, the chassis of the rover arrived and is now being filled with computers, batteries, and other electronics. Assembly of its complex drilling and sample storage system is underway, with other scientific instruments due by the end of February. “This is the mad scramble,” Farley adds. “It is full bore get it done, get it done now.”

At the workshop’s end, scientists will vote on the candidates, followed by a closed-door meeting of the rover team to make a final choice. Engineers have deemed the sites safe for landing, Golombek adds, so it will come down to the science. The team’s recommendation won’t be the final word—the choice is ultimately up to NASA science chief Thomas Zurbuchen. But expect a decision within the next few months, if not sooner.

Landing site for next Mars rover

Scientists home in on landing site for the next Mars rover

By Paul Voosen |

After 3 days of intense debate, a nonbinding vote by planetary scientists meeting in Glendale, California, resulted in a virtual tie between several candidate landing sites for NASA’s next $2.5 billion Mars rover, due for launch in 2020.

The straw poll is the culmination of years of scientific and engineering analysis of three NASA-approved sites: Jezero, a fossilized delta that spills into an impact crater; Northeast Syrtis, a stretch of ancient crust that may have been created by underground mineral springs; and Columbia Hills, a potential former hot springs previously visited by the Spirit rover. Earlier this year, the team added to the mix a fourth site, nearly identical in composition to Northeast Syrtis, called Midway, with the potential that a mission could visit Jezero and then Midway, or vice versa.

All four sites were evaluated both for their suitability as the primary landing site and as an area for continued exploration following the rover’s first couple of years. In turn, each site was rated for the value of the science the rover could conduct itself, with its fleet of instruments, and the value of the samples that it will drill for return to Earth.

With 158 votes tallied, Jezero and Northeast Syrtis rated in a near tie for their value as a primary destination, with Midway close behind. Jezero and Midway, in turn, rated higher as destinations for an extended mission. Across both categories, only Columbia Hills was rated much lower. Although the method of the vote—rating candidates—did not lead to a clear recommendation, the combined ratings do seem to endorse the Midway-Jezero pairing. As Ryan Anderson, a planetary scientist at the U.S. Geological Survey’s Astrogeology Science Center in Flagstaff, Arizona, put it, “A mega-mission in either direction looks pretty likely.”

What the vote means will be up to the Mars 2020 team and, ultimately, NASA’s science chief, Thomas Zurbuchen, who made a brief appearance at the workshop. Although a plan to return the rover’s samples is not finalized, Zurbuchen noted, a mission should come into view by early 2020, after Europe, a vital potential contributor, finalizes its next round of science funding. “Make no mistake,” Zurbuchen told the scientists, “we want those samples back.”

Read our in-depth preview of the landing sites, including the rise of Midway here.

 

A recipe that jump-started life

Chemists find a recipe that may have jump-started life on Earth

By Robert F. Service |

ATLANTA—In the molecular dance that gave birth to life on Earth, RNA appears to be a central player. But the origins of the molecule, which can store genetic information as DNA does and speed chemical reactions as proteins do, remain a mystery. Now, a team of researchers has shown for the first time that a set of simple starting materials, which were likely present on early Earth, can produce all four of RNA’s chemical building blocks.

Those building blocks—cytosine, uracil, adenine, and guanine—have previously been re-created in the lab from other starting materials. In 2009, chemists led by John Sutherland at the University of Cambridge in the United Kingdom devised a set of five compounds likely present on early Earth that could give rise to cytosine and uracil, collectively known as pyrimidines. Then, 2 years ago, researchers led by Thomas Carell, a chemist at Ludwig Maximilian University in Munich, Germany, reported that his team had an equally easy way to form adenine and guanine, the building blocks known as purines. But the two sets of chemical reactions were different. No one knew how the conditions for making both pairs of building blocks could have occurred in the same place at the same time.

Now, Carell says he may have the answer. On Tuesday, at the Origins of Life Workshop here, he reported that he and his colleagues have come up with a simple set of reactions that could have given rise to all four RNA bases.

Carell’s story starts with only six molecular building blocks—oxygen, nitrogen, methane, ammonia, water, and hydrogen cyanide, all of which would have been present on early Earth. Other research groups had shown that these molecules could react to form somewhat more complex compounds than the ones Carell used.

To make the pyrimidines, Carell started with compounds called cyanoacetylene and hydroxylamine, which react to form compounds called amino-isoxazoles. These, in turn, react with another simple molecule, urea, to form compounds that then react with a sugar called ribose to make one last set of intermediate compounds.

Finally, in the presence of sulfur-containing compounds called thiols and trace amounts of iron or nickel salts, these intermediates transform into the pyrimidines cytosine and uracil. As a bonus, this last reaction is triggered when the metals in the salts harbor extra positive charges, which is precisely what occurs in the final step in a similar molecular cascade that produces the purines, adenine and guanine. Even better, the step that leads to all four nucleotides works in one pot, Carell says, offering for the first time a plausible explanation of how all of RNA’s building blocks could have arisen side by side.

“It looks pretty good to me,” says Steven Benner, a chemist with the Foundation for Applied Molecular Evolution in Alachua, Florida. The process provides a simple way to produce all four bases under conditions consistent with those believed present on early Earth, he says.

The process doesn’t solve all of RNA’s mysteries. For example, another chemical step still needs to “activate” each of RNA’s four building blocks to link them into the long chains that form genetic material and carry out chemical reactions. But making RNA under conditions like those present on early Earth now appears within reach.

 

ngVLA and Pulsar Timing Arrays

Science with the Next-Generation VLA and Pulsar Timing Arrays

Pulsar timing arrays (PTAs) can be used to detect and study gravitational waves in the nanohertz band (i.e., wavelengths of order light-years). This requires high-precision, decades-long data sets from sensitive, instrumentally stable telescopes. NANOGrav and its collaborators in the International Pulsar Timing Array consortium are on the verge of the first detection of the stochastic background produced by supermassive binary black holes, which form via the mergers of massive galaxies. By providing Northern hemisphere sky coverage with exquisite sensitivity and higher frequency coverage compared to the SKA, a Next-Generation Very Large Array (ngVLA) will be a fundamental component in the next phase of nanohertz GW astrophysics, enabling detailed characterization of the stochastic background and the detection of individual sources contributing to the background, as well as detections of (or stringent constraints on) cosmic strings and other exotica. Here we summarize the scientific goals of PTAs and the technical requirements for the ngVLA to play a significant role in the characterization of the nanohertz gravitational wave universe.

 

ROCK64 Single Board Computer

ROCK64 4K60P HDR Single Board Computer

ROCK64 is a credit card size 4K60P HDR Single Board Computer powered by Rockchip RK3328 Quad-Core ARM Cortex A53 64-Bit Processor and support up to 4GB 1600MHz LPDDR3 memory. It provides eMMC module socket, MicroSD Card slot, Pi-2 Bus, Pi-P5+ Bus, USB 3.0 and many others peripheral devices interface for makers to integrate with sensors and devices. Various Operating System (OS) are made available by open source community such Android 7.1, Debian, BSD and many more to come.

Jeg har fundet bionic-lxde-rock64-0.7.10-1072-arm64.img (Ubuntu 18.04), som jeg overførte til et 64GB MicroSD kort med dd kommantoen:

dd if=bionic-lxde-rock64-0.7.10-1072-arm64.img of=/dev/sdx bs=1M

Brugeren rock64 med uid=1000 er oprettet med password: rock64.
Man har masser af SD-plads til rådighed, og de 4GB RAM tillader kørsel af libreoffice, GIMP og OCTAVE.

The ROCK64 4GB board designated as LTS (long Term Supply) model, PINE64 committed to supply at least for 5 years until year 2022 and beyond.