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If alien technological civilizations exist, they almost certainly use solar energy. Along with wind, it’s the cleanest, most accessible form of energy, at least here on Earth. Driven by technological advances and mass production, solar energy on Earth is expanding rapidly.

It seems likely that ETIs (Extraterrestrial Intelligence) using widespread solar energy on their planet could make their presence known to us.

If other ETIs exist, they could easily be ahead of us technologically. Silicon solar panels could be widely used on their planetary surfaces. Could their mass implementation constitute a detectable technosignature?

The authors of a new paper examine that question. The paper is “Detectability of Solar Panels as a Technosignature,” and it’ll be published in The Astrophysical Journal. The lead author is Ravi Kopparapu from NASA’s Goddard Space Flight Center.

In their paper, the authors assess the detectability of silicon-based solar panels on an Earth-like habitable zone planet. “Silicon-based photovoltaic cells have high reflectance in the UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept like the Habitable Worlds Observatory (HWO),” the authors write. The HWO would search for and image Earth-like worlds in habitable zones. There’s no timeline for the mission, but the 2020 Decadal Survey recommended the telescope be built. This research looks ahead to the mission or one like it sometime in the future.

Naturally, the authors make a number of assumptions about a hypothetical ETI using solar power. They assume that an ETI is using large-scale photovoltaics (PVs) based on silicon and that their planet orbits a Sun-like star. Silicon PVs are cost-effective to produce, and they are well-suited to harness the energy from a Sun-like star.

Kopparapu and his co-authors aren’t the first to suggest that silicon PVs could constitute a technosignature. In a 2017 paper, Avi Loeb and Manasvi Lingam from the Harvard-Smithsonian Center for Astrophysics wrote that silicon-based PVs create an artificial edge in their spectra. This edge is similar to the ‘red edge‘ detectable in Earth’s vegetation when viewed from space but shifted to shorter wavelengths. “Future observations of reflected light from exoplanets would be able to detect both natural and artificial edges photometrically if a significant fraction of the planet’s surface is covered by vegetation or photovoltaic arrays, respectively,” Lingam and Loeb wrote.

“The “edge” refers to the noticeable increase in the reflectance of the material under consideration when a reflected light spectrum is taken of the planet,” the authors of the new research explain. Satellites monitor the red edge on Earth to observe agricultural crops, and the same could apply to sensing PVs on other worlds.

This figure shows the reflection spectrum of a deciduous leaf (data from Clark et al. 1993). The large sharp rise (between 700 and 800 nm) is known as the red edge and is due to the contrast between the strong absorption of chlorophyll and the otherwise reflective leaf. Image Credit: Seager et al. 2005.
This figure shows the reflection spectrum of a deciduous leaf (data from Clark et al. 1993). The large sharp rise (between 700 and 800 nm) is known as the red edge and is due to the contrast between the strong absorption of chlorophyll and the otherwise reflective leaf. Image Credit: Seager et al. 2005.

While Lingam and Loeb suggested the possibility, Kopparapu and his co-authors dug deeper. They point out that we could generate enough energy for our needs (as of 2022) if only 2.4% of the Earth’s surface was covered in silicon-based PVs. The 2.4% number is only accurate if the chosen location is optimized. For Earth, that means the Sahara Desert, and something similar may be true on an alien world.

The authors explain, “This region is both close to the equator, where a comparatively greater amount of solar energy would be available throughout the year, and has minimal cloud coverage.”

The authors also work with a 23% land coverage number. This number reflects previous research showing that for a projected maximum human population of 10 billion people, 23% land coverage would provide a high standard of living for everyone. They also use it as an upper limit because
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10 Great, Big Dayhikes in the Tetons

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By Michael Lanza

The Tetons stand out for many reasons, most of all that iconic skyline of jagged peaks and spires that invites comparisons to cathedrals—although these cathedrals reach over 12,000 and 13,000 feet high. But while backpackers flock to the Teton Range for multi-day hikes and these peaks offer numerous five-star dayhikes of “normal” length, they also harbor some of the best long dayhikes in the country.

Thanks to a unique combination of the trail network and trailhead access, hikers capable of knocking off 15 to 20 or more miles and 3,000 to over 4,000 vertical feet in a day can explore virtually the entire range on one-day outings—holding enormous appeal for hikers and trail runners seeking that level of challenge or fit backpackers who fail to obtain a highly coveted Grand Teton National Park backcountry permit for a multi-day hike.

This list of the 10 best big dayhikes in the Teton Range includes popular spots like Garnet Canyon, Lake Solitude, and the Paintbrush Canyon-Cascade Canyon loop, as well as some trails and peaks you may not have heard of—some of which see little traffic.

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Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-books to classic backpacking trips. Click here to learn how I can help you plan your next trip.

A backpacker on the Teton Crest Trail in Grand Teton National Park.
” data-image-caption=”Jeff Wilhelm backpacking the Teton Crest Trail n Grand Teton National Park. Click photo for my e-book “The Complete Guide to Backpacking the Teton Crest Trail.”
” data-medium-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/11/06231551/Tet19-110-Tet19-107-Jeff-Wilhelm-backpacking-the-Teton-Crest-Trail-through-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg?fit=300%2C203&ssl=1″ data-large-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/11/06231551/Tet19-110-Tet19-107-Jeff-Wilhelm-backpacking-the-Teton-Crest-Trail-through-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg?fit=900%2C608&ssl=1″ tabindex=”0″ role=”button” src=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/11/06231551/Tet19-110-Tet19-107-Jeff-Wilhelm-backpacking-the-Teton-Crest-Trail-through-North-Fork-Cascade-Canyon-Grand-Teton-N.P.-1024×692.jpg?resize=900%2C608&ssl=1″ alt=”A backpacker on the Teton Crest Trail in Grand Teton National Park.” class=”wp-image-36371″ srcset=”https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/11/06231551/Tet19-110-Tet19-107-Jeff-Wilhelm-backpacking-the-Teton-Crest-Trail-through-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg 1024w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/11/06231551/Tet19-110-Tet19-107-Jeff-Wilhelm-backpacking-the-Teton-Crest-Trail-through-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg 300w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/11/06231551/Tet19-110-Tet19-107-Jeff-Wilhelm-backpacking-the-Teton-Crest-Trail-through-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg 768w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/11/06231551/Tet19-110-Tet19-107-Jeff-Wilhelm-backpacking-the-Teton-Crest-Trail-through-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg 1080w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/11/06231551/Tet19-110-Tet19-107-Jeff-Wilhelm-backpacking-the-Teton-Crest-Trail-through-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />Jeff Wilhelm backpacking the Teton Crest Trail n Grand Teton National Park. Click photo for my e-book “The Complete
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Galaxies Regulate their Own Growth so they Don’t Run Out of Star Forming Gas

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Look at most spiral or barred spiral galaxies and you will see multiple regions where stars are forming. These star forming regions are comprised of mostly hydrogen gas with a few other elements for good measure. The first galaxies in the Universe had huge supplies of this star forming gas. Left unchecked they could have burned through the gas quickly, generating enormous amounts of star formation. Life fast though and die young for such an energetic burst of star formation would soon fizzle out leaving behind dead and dying stars. In some way it seems, galaxies seem to regulate their star formation thanks to supermassive black holes at their centre. 

The first galaxies formed about 400 to 700 million years after the Big Bang, during the Epoch known as Reionization. These early galaxies were small and faint, mostly composed of hydrogen and helium, and contained dense clusters of massive, short-lived Population III stars (the first generation of stars.) The intense radiation from these stars ionised the surrounding gas, clearing the fog that permeated space making the universe transparent for the first time. These primordial galaxies began merging and interacting, laying the foundation for the galaxy types seen today.

A new study published in the Monthly Notices of the Royal Astronomical Society explores why galaxies are not as large as astronomers would expect. The research suggests that galaxies, even those that formed first, avoid an early death because they have mechanisms similar to “heart and lungs,” which regulate their “breathing”. Without these regulatory processes our bodies, and galaxies would have aged much faster, resulting in massive galaxies filled with dead and dying stars and devoid of new star formation.

Observations show that galaxies are not so big and full of dying stars having outgrown themselves. It seems something limits their ability to allow gas to form into stars. Astrophysicists at the University of Kent believe they may have the answer: galaxies could be controlling their growth rate through a process not too dissimilar to “breathing.” They compare the supermassive black hole at the centre of a galaxy to a heart and the supersonic jets emerging from the poles with the radiation and gas they emit to airways feeding a pair of lungs.

The supermassive black holes seem to pulse just like a heart. These pulses cause a shock front to oscillate along the jets like a diaphragm inflating and deflating the lungs. This process transmits energy along the jet slowly counteracting the pull of gravity and slowing gas accretion and star formation. The idea was developed by PhD student Carl Richards and his simulations showed a black hole pulsing like a heart. 

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Assisted by magnetic fields, a spiraling wind helps the supermassive black hole in galaxy ESO320-G030 grow. In this illustration, the core of the galaxy is dominated by a rotating wind of dense gas leading outwards from the (hidden) supermassive black hole at the galaxy’s center. The motions of the gas, traced by light from molecules of hydrogen cyanide, have been measured with the Atacama Large Millimeter/submillimeter Array. Image credit: M. D. Gorski/Aaron M. Geller, Northwestern University, CIERA, the Center for Interdisciplinary Exploration and Research in Astrophysics.

Richards explains “We realised that there would have to be some means for the jets to support the body – the galaxy’s surrounding ambient gas – and that is what we discovered in our computer simulations,” He continued “The unexpected behaviour was revealed when we analysed the computer simulations of high pressure and allowed the heart to pulse.”

Evidence of ripples just like those in Richards’ simulations, in extra-galactic media have been found in galaxy clusters like the Perseus cluster. These ripples are thought to sustain a galaxy’s environment, though their generation mechanism was unclear. Conventional simulations fail to explain gas flows into galaxies, but the work of the team from the University of Kent may well have answered the question.

Source : How the ‘heart and lungs’ of a galaxy extend its life.

The post Galaxies Regulate their Own Growth so they Don’t Run Out of Star Forming Gas appeared first on Universe Today.

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Bear Essentials: How to Store Food When Backcountry Camping

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By Michael Lanza

On our first night in the backcountry of Yosemite National Park on one of my earliest backpacking trips, two friends and I—all complete novices—hung our food from a tree branch near our camp. Unfortunately, the conifer trees around us all had short branches: Our food stuff sacks hung close to the trunk.

During the night, the predictable happened: We awoke to the sound of a black bear clawing up the tree after our food.

Despite our nervousness and incompetence, we somehow managed to shoo that black bear off, though not before he (or she) departed with a respectable haul from our food supply. But by virtue of having started out with way more food than we needed—another rookie mistake that, ironically, compensated for this more-serious rookie mistake (read my tips on not overpacking)—we made it through that hike without going hungry and ultimately had a wonderful adventure.

And we went home with a valuable lesson learned.

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Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-books to classic backpacking trips. Click here to learn how I can help you plan your next trip.

A black bear along the Sol Duc River Trail in Olympic National Park.
” data-image-caption=”A black bear along the Sol Duc River Trail in Olympic National Park.
” data-medium-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg?fit=300%2C201&ssl=1″ data-large-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg?fit=900%2C602&ssl=1″ tabindex=”0″ role=”button” src=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2-1024×685.jpg?resize=900%2C602&ssl=1″ alt=”A black bear along the Sol Duc River Trail in Olympic National Park.” class=”wp-image-34782″ srcset=”https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg 1024w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg 300w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg 768w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg 1080w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />A black bear along the Sol Duc River Trail in Olympic National Park.

I’ve learned much more about storing food properly in the backcountry over the more than three decades since that early trip, including the 10 years I spent as the Northwest Editor of Backpacker magazine and even longer running this blog. This article shares what I’ve learned about protecting food from critters like bears and, more commonly, mice and other small animals and some birds like ravens.

Follow the tips below and you’ll not only save yourself and your party or family from going hungry, you might save a bear from developing a habit of seeing humans as sources of food, which too often leads to a bad outcome for that animal.

If you have any questions or tips of your own to share, please do so in the comments section at the bottom of this
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