Large parts of today's Sahara Desert were green thousands of years ago. Prehistoric engravings of giraffes and crocodiles testify to this, as does a stone-age cave painting in the desert that even shows swimming humans. However, these illustrations only provide a rough picture of the living conditions. Recently, more detailed insights have been gained from sediment cores extracted from the Mediterranean Sea off the coast of Libya. An international research team examined these cores and discovered that the layers of the seafloor tell the story of major environmental changes in North Africa over the past 160,000 years. Cécile Blanchet of the German Research Centre for Geosciences GFZ and her colleagues from Germany, South Korea, the Netherlands and the USA report on this in the journal Nature Geoscience.

Together with the GEOMAR Helmholtz Centre for Ocean Research Kiel, a team of scientists organized a research cruise on the Dutch vessel Pelagia to the Gulf of Sirte in December 2011. "We suspected that when the Sahara Desert was green, the rivers that are presently dry would have been active and would have brought particles into the Gulf of Sirte", says lead author Cécile Blanchet. Such sediments would help to better understand the timing and circumstances for the reactivation of these rivers.

Researchers said Wednesday they had observed water vapour escaping high up in the thin atmosphere of Mars, offering tantalising new clues as to whether the Red Planet could have once hosted life.

The traces of ancient valleys and river channels suggest liquid water once flowed across the surface of Mars. Today, the water is mostly locked up in the planet's ice caps or buried underground.

But some of it is vaporising, in the form of hydrogen leaking from the atmosphere, according to the new research co-authored in the journal Science Advances by two scientists at Britain's Open University.

An international team of astronomers has found signs that a habitable planet may be lurking in Alpha Centauri, a binary star system a mere 4.37 light-years away. It could be one of the closest habitable planet prospects to date, although it's probably not much like Earth if it exists.

What's Alpha Centauri? It's the closest star system to our own, comprising three different stars. There are Alpha Centauri A and B, which are sun-like stars that form a tight binary orbit around one another about 4.37 light years away. And then there's Proxima Centauri, a small red dwarf that's actually closer to us (4.24 light-years away) and has a much looser gravitational relationship with the other two stars.

Proxima Centauri is orbited by two planets, one of which (Proxima b) seems be an Earth-size exoplanet in the habitable zone (the region of a star's orbit where liquid water can form on the surface). But Proxima b is thought to be tidally locked and inundated by stellar winds, which means it's unlikely to be habitable.

Dragons lurk at the edges of the map of known elements - atomic giants so delicate, and so scarce, they defy easy study.

One such behemoth has finally given up at least some of its secrets, with chemists managing to gather just enough einsteinium to flesh out important details on the mysterious element's chemistry and ability to form bonds.

For the better part of 70 years, isotopes of einsteinium have proven frustratingly difficult to study. Either they're way too hard to make, or they have a half-life of less than a year, and what precious little is created begins to fall apart like a sandcastle at high tide.

Systems designed to detect deepfakes--videos that manipulate real-life footage via artificial intelligence--can be deceived, computer scientists showed for the first time at the WACV 2021 conference which took place online Jan. 5 to 9, 2021.

Researchers showed detectors can be defeated by inserting inputs called adversarial examples into every video frame. The adversarial examples are slightly manipulated inputs which cause artificial intelligence systems such as machine learning models to make a mistake. In addition, the team showed that the attack still works after videos are compressed.

Shehzeen Hussain, a UC San Diego computer engineering Ph.D. student and first co-author on the WACV paper, said:

"Our work shows that attacks on deepfake detectors could be a real-world threat. More alarmingly, we demonstrate that it's possible to craft robust adversarial deepfakes in even when an adversary may not be aware of the inner workings of the machine learning model used by the detector."

In deepfakes, a subject's face is modified in order to create convincingly realistic footage of events that never actually happened. As a result, typical deepfake detectors focus on the face in videos: first tracking it and then passing on the cropped face data to a neural network that determines whether it is real or fake. For example, eye blinking is not reproduced well in deepfakes, so detectors focus on eye movements as one way to make that determination. State-of-the-art Deepfake detectors rely on machine learning models for identifying fake videos.

Supernova explosions seed the galaxy with elements vital for life and serve as tracers revealing the fate of the universe to us. Yet for all their importance, they include some sub-types we barely understand. Perhaps the most confusing are those known as Type Iax (pronounced one-ax), but the possible remnants of one of these events could provide some major clues to understanding them, and it could be the first one ever found in the Milky Way.

Before we had any idea what caused them, supernovas - powerful, luminous stellar explosions - were categorized based on their dominant spectral lines. The most useful of these for research purposes turned out to be those known as Type Ia, which have the very convenient trait of always being roughly the same in their intrinsic brightness. By measuring how much light we see from a Type Ia supernova astronomers can get a good estimate of how far away the explosion, and therefore the galaxy in which it is housed, is from us.

This has served us well enough to reveal the fact the universe's expansion is accelerating, but between one-sixth and one-third of what at first looks like Ia supernovae aren't. Among these are a group sometimes called Type Iax supernovas, which have a spectrum marked by ionized silicon like ordinary Type Ias, but are considerably fainter.

While at the University of Amsterdam, study lead Ping Zhou observed a supernova remnant known as Sagittarius A East using the Chandra X-Ray telescope. Zhou thinks this is the first residue of an Iax supernova we have found in our galaxy.

There has been talk out thar in the wildlands of Twitter from people who don't believe the evidence that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is real.

Has the 'the COVID virus' ever been isolated in cell culture, visualised by electron microscopy, reacted with antibodies, genetically sequenced and otherwise characterised in many samples collected from people with coronavirus disease 19 (COVID-19) all over the world during the past nine months?

Sigh, yes, and yes the 'COVID virus' is real. Here are a few of the scientific endeavours that show this virus has been isolated from clinically diagnosed, ill and laboratory-confirmed human COVID-19 cases.

False claims fueling the widespread delusion that SARS-CoV-2 doesn't exist are harming efforts to combat the authoritarian responses to COVID-19.

For months, I have been continually confronted with the belief held by many within my own community of readers that SARS-CoV-2, the virus that causes COVID-19, has not even been proven to exist.

I would much prefer to spend my time fact-checking the self-proclaimed "fact checkers" that are censoring factual information while hypocritically misinforming the public. But there's one claim in particular that I've been faced with repeatedly that really needs to be put to rest because it is serving only to legitimize the "fact checker" narrative that opponents of authoritarian "lockdown" measures are spreading misinformation.

The specific claim is that the Centers for Disease Control and Prevention (CDC) has admitted that SARS-CoV-2 has not been isolated — in other words, that it has not been proven to exist.

The "smoking gun" document in which the CDC ostensibly admitted that the virus hasn't been isolated is titled "CDC 2019-Novel Coronavirus (2019-nCov) Real-Time RT-PCR Diagnostic Panel". It is published on the website of the Food and Drug Administration (FDA).

Yesterday, we noted that in a debate with four other philosophers of physics, Charles Sebens argued that there are no particles, everything is fields.

A friend now writes to remind us that physics great Max Planck had quite immaterial views on the nature of the universe:

Max Planck: Gentlemen, as a physicist who all his life, within the most sober and rational science, has been devoted to the study of matter, I am certain to be free of the suspicion of being a dreamer, and so I say after my research on the atom; matter as such does not exist.

All matter originates and exists only by virtue of a force that brings the parts of the atom in vibration, and keeps the smallest solar system of the universe together. As there in the entire universe does not exist an intelligent force, nor an eternal force- man has not yet succeded in inventing the perpetuum mobile- so must we assume behind this force the existence of a conscious intelligent spirit. This spirit is the basis of all matter. The visible but impermanent matter is not the reality and truth- because without spirit, matter wouldn't exist at all- but the invisible, immortal spirit is the truth. Because every spirit belongs to a being, we are forced to assume it to be a spiritual being. Because spiritual beings do not come about by themselves, but must be created, I will not hesitate in fact, to call this secretive creator, like people of all cultures through millennia has done, God. Thereby moves the physicist who dealt with matter, from the realm of stuff to the realm of the spirit. And so is our task ended, and we must then pass on the research into the hands of the philosophers. - Lecture, 'Das Wesen der Materie' [The Essence/Nature/Character of Matter], Florence, Italy (1944). Archiv zur Geschichte der Max-Planck-Gesellschaft, Abt. Va, Rep. 11 Planck, Nr. 1797. Excerpt in Gregg Braden, The Spontaneous Healing of Belief: Shattering the Paradigm of False Limits (2009), 334-35.

Astronomers are using tree rings as a historical record of solar activity — and they've found that the Sun was much more active in the past.

Our Sun is not the faithfully constant light source it appears to be. Solar activity varies in a fairly regular cycle of 11 years, most notably in the periodic rise and fall in the number of sunspots. Though German astronomer Samuel Heinrich Schwabe discovered the cycle in the 19th century, sunspot observations commenced about 400 years ago with Galileo Galilei, and the solar cycle has been traced back to these early observations.

Now, a team of scientists based in Switzerland has successfully reconstructed the 11-year Schwabe cycle all the way back to the year AD 969, using the Sun's imprint on ancient trees on Earth. Their report appears in Nature Geoscience.