Celebrate Science Day 2020 by proving the Earth is not flat.
- Flat-Earthers drive rational people nuts.
- A physicist offers three experiments to confirm it is those people who are crazy, not you.
- The experiments, however, do require a belief in mathematics.
Experiment 1: Catch a sunset twice<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDc2ODQxMC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1Mjk0Mzg5NX0.VR2LnQx4TKhyTwmSoZSkDfsOMgqac4d6Drm49vyYCGA/img.jpg?width=980" id="64198" class="rm-shortcode" data-rm-shortcode-id="294982a49a33773d038f756f7227b37d" data-rm-shortcode-name="rebelmouse-image" />
Credit: Johannes Plenio/Unsplash<p>At the top of the calculator is the "Select an experiment" drop-down menu. Let's start with the "<a href="https://www.omnicalculator.com/physics/flat-vs-round-earth#sunset-twice-experiment" target="_blank">sunset twice</a>" experiment.</p><p>Wooding notes that you can prove the Earth is round by standing up quickly right after the Sun goes down and getting ahead of the shadow cast by the horizon so you can see the sun set a second time. If the planet were flat, once it went over the edge from your first viewing position it would be gone.</p><p>You may want to find out the time of sunset before testing out the calculator. There are many places online to find this information. <a href="https://www.timeanddate.com/sun/" target="_blank">Here's one</a>.</p><p>To use the calculator, begin by selecting a city in your time zone. Wooding has pre-entered the sunset duration for you, though you can look up the precise value online for your location.</p><p>There are three ways to increase your height, selected from the "Ideas" menu: standing up from a lying down position, taking the sky-lift elevator at the <a href="https://en.wikipedia.org/wiki/Burj_Khalifa" target="_blank" rel="noopener noreferrer">Burj Khalifa Hotel</a> in Dubai, or sending up a drone with a camera on it. Most of us will select the first option.</p><p>Next, you enter your starting height (the default for lying down is .6562 feet), how long it will take you to stand up, and then the final standing elevation, presumably of your eyes.</p><p>What the calculator finds for you is the percentage of the second sunset you'll see. Note that for the sky-lift and drone tests, you see a lot more of that second sunset given the greater height and your accelerated ascent speed.</p>
Experiment 2: Disappearing object<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDc2ODQxMy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0MDIzOTU5MX0.NUrgcREKhtrD4TfGtDTDB7_WuCbYTreoXSTnWCsE3Mw/img.jpg?width=980" id="fdac5" class="rm-shortcode" data-rm-shortcode-id="d6fd8797e0bffb64f96d6104e04d09c4" data-rm-shortcode-name="rebelmouse-image" />
Credit: Michael Olsen/Unsplash<p>Thanks to the curvature of the Earth, you can make an object on a distant lake shore seem to <a href="https://www.omnicalculator.com/physics/flat-vs-round-earth#disappearing-object-experiment" target="_blank">disappear</a> with a change in viewing height.</p><p>You'll need binoculars for this one. And, um, a lake.</p><p>The calculator will tell you how much of the object will become unobservable after you fill in the three values.</p><p>(You may also need a boat to measure the distance.)</p>
Experiment 3: Stick shadows<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDc2ODQyMS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NTM2MTg0Nn0.eyqFl7ulLoMf8UvNYXoPrZ3vcLwyygaM9QJ70EjD9NI/img.jpg?width=980" id="3d767" class="rm-shortcode" data-rm-shortcode-id="2ba382e4212a5f7a8ad4e58dba4e38b1" data-rm-shortcode-name="rebelmouse-image" />
Credit: Logan Radinovich/Unsplash<p><a href="https://www.omnicalculator.com/physics/flat-vs-round-earth#instructions-for-measuring-how-big-the-earth-is-using-stick-shadows" target="_blank">For this one</a> you'll need a cooperative friend who lives at least some distance away, or a teleporter. Also two sticks and a day with enough sunlight to cast shadows in both locations.</p><p>This experiment involves measuring shadows cast at two different locations and calculating the angle between them to arrive at the Earth's circumference.</p><p>This experiment is a little advanced mathematically, and Wooding offers a help link if you're confused.</p>
The study identified superhabitable planets outside of our solar system.
- The odds are that if Earth had the right conditions for the development of life, other places probably do, too.
- Scientists have identified two dozen planets that match some items on the list of desirable traits.
- All of these planets are too far away to reach with current tech, but may be valuable research targets.
Superhabitable<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQ3MzYwNC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxMjYwOTE5NX0.7WH5907n-K3Ew9QP96D1ohm_yUDEcwH_XjnDwnICYQM/img.jpg?width=980" id="206f9" class="rm-shortcode" data-rm-shortcode-id="ef375f57087011a2324d7f086e3b96c1" data-rm-shortcode-name="rebelmouse-image" />
The 24 candidates in their habitable zone near K dwarf stars
Credit: Schulze-Makuch, et al./Astrobiology<p>On the other hand, all that desirable real estate is pretty far away — none of these 24 "superhabitable" planets are less than 100 light years from Earth. They were identified in a study led by geologist <a href="https://news.wsu.edu/tag/dirk-schulze-makuch/" target="_blank" rel="noopener noreferrer">Dirk Schulze-Makuch</a> of WSU and Technical University in Berlin, Germany. He was joined in the research by astrophysicists <a href="https://www2.mps.mpg.de/homes/heller/" target="_blank">René Heller</a> of the Max Planck Institute for Solar System Research in Germany and <a href="https://firstname.lastname@example.org&xsl=bio_long" target="_blank">Edward Guinan</a> of Villanova University.</p><p>The open-access study is published in the journal <a href="https://www.liebertpub.com/doi/10.1089/ast.2019.2161" target="_blank">Astrobiology</a>.</p><p>Ignoring the possibility that other planets might be even more likely to support life than ours is, after all, like someone insisting they live in the best country in the world without having visited any others. The study puts it this way: "Neglecting this possible class of 'superhabitable' planets, however, could be considered anthropocentric and geocentric biases."</p><p>In searching for superhabitable planets among the 4,500 known candidates, the scientists were not so much looking for somewhere for us to escape to as they were spotting planets that were most likely to be populated by intelligent life. Their hope is to offer up interesting targets for future investigation by instruments such as the European Space Agency's <a href="https://sci.esa.int/web/plato" target="_blank" rel="noopener noreferrer">PLATO space telescope</a>, as well as NASA's <a href="https://www.jwst.nasa.gov" target="_blank">James Webb Space Telescope</a> and <a href="https://asd.gsfc.nasa.gov/luvoir/" target="_blank" rel="noopener noreferrer">LUVOIR space observatory</a>.</p><p>Schulze-Makuch tells <a href="https://news.wsu.edu/2020/10/05/planets-may-better-life-earth/" target="_blank">WSU Insider</a>:</p><p style="margin-left: 20px;">"With the next space telescopes coming up, we will get more information, so it is important to select some targets. We have to focus on certain planets that have the most promising conditions for complex life. However, we have to be careful to not get stuck looking for a second Earth because there could be planets that might be more suitable for life than ours."</p><p>Before one can go searching for superhabitable planets, once must figure out what that word means.</p>
Blame it on the sun<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQ3MzYxNC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2NjAwNDUyNn0.bv9FioVLoHPE7IxjWnmRzfNKkeGI6UOioEorxSqMapU/img.jpg?width=980" id="7f28c" class="rm-shortcode" data-rm-shortcode-id="5613866aa3c976f165e51f4565517e90" data-rm-shortcode-name="rebelmouse-image" />
Credit: Tungdil Preston/Unsplash<p>The scientists first had to work out the type of sun a superhabitable planet would be most likely to orbit. Interestingly, they decided against dwarf type G stars — also known as "dG stars" — similar to our own sun. After all, they write, "Since it took about 3.5 billion years on Earth until complex macroscopic life appeared, and about 4 billion years for technologically advanced life (us), life on many planets orbiting dG stars may simply run out of time."</p><p>Another issue is that young dG stars spin 10 times as fast as our mature Sun now does, producing "high levels of magnetic dynamo-driven activity and very intense coronal X-ray and chromospheric FUV emissions, which makes the origin and early evolution of life challenging."</p><p>The study settles on planets orbiting type K stars. These stars are a bit cooler than ours and less luminous, but they live a long time, longer than the Sun, from 20 to 70 billion years. This would give their planets more time to get life going.</p>
Size matters<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQ3MzYxNy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNjkxMzg4Nn0.x8YqDvGmdmooMUSRu7oJCGTKiwg5VPrqZaoboVOa5fQ/img.jpg?width=980" id="f48b4" class="rm-shortcode" data-rm-shortcode-id="372b444990b8ca7a2520d3bca8124851" data-rm-shortcode-name="rebelmouse-image" />
Credit: AleksandrMorrisovich/Shutterstock<p>Planets with a greater mass than ours were deemed desirable for a few reasons, so long as they were not so big as to become gas giants and so on. These planets would have robust, thick atmospheres, slightly higher temperatures for nurturing life, and lots of elbow room: "This would have advantages for the distribution of species and settlements of islands and continents."</p>
Environmental requirements<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQ3MzYyNC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MjQ4NzM5Mn0.9dDvWvYfJY63wX2QbZ0SnITCtsSAMzAoK0H4pfG7D8Q/img.jpg?width=980" id="d973e" class="rm-shortcode" data-rm-shortcode-id="b2e925bc9949378ce37bbc318ff35493" data-rm-shortcode-name="rebelmouse-image" />
Credit: BeeBright/Shutterstock<p>The researchers also settled on an environmental checklist for superhabitable planets. Based on the conditions that allowed life to form on Earth, a planet would have to have the following life-supporting conditions as explained in the study:</p><ul><li><em>T</em><em>emperatures</em> —"Submarine hydrothermal systems, geothermal hot springs, brine pockets in sea ice at about −30°C, deep continental areas"</li><li><em>pH</em> — "Acid mine drainage, geothermal sulfurous sites (e.g., Yellowstone) Soda lakes, peridotite-hosted hydrothermal systems (e.g., Lost City vent)"</li><li><em>Water activity</em> — "Deep-sea brines, soda lakes, evaporate ponds, dry soils and rocks, food with high solute content"</li><li><em>Lower O2 content </em>— "Anoxic marine or lacustrine sediments, intestinal organs, early Earth environments"</li><li><em>Pressure</em> — "Deep oceanic trenches such as the 11,100 m deep Marianas Trench, Martian surface conditions (based on laboratory experiments)"</li><li><em>Radiation</em> — "No natural source of radiation on Earth at levels tolerated by D. radiodurans"</li><li><em>Chemical extremes</em> — "Submarine hydrothermal vent fluids and sulfides; some high-metal containing lakes"</li></ul>
We have some winners. Sort of.<p>Of the superhabitable candidates the study detected, none totally meet the researchers' criteria, though one has four of them, meaning it may be more likely to have life on it than Earth did, and it might be a place we could consider quite comfy.</p><p>Concludes Schulze-Makuch, "It's sometimes difficult to convey this principle of superhabitable planets because we think we have the best planet. We have a great number of complex and diverse lifeforms, and many that can survive in extreme environments. It is good to have adaptable life, but that doesn't mean that we have the best of everything."</p>
The theory could resolve some unanswered questions.
- Most stars begin in binary systems, why not ours?
- Puzzles posed by the Oort cloud and the possibility of Planet 9 may be solved by a new theory of our sun's lost companion.
- The sun and its partner would have become separated long, long ago.
If most stars form in binary pairs, what about our Sun? A new paper presents a model supporting the theory that the Sun may have started out as one member of a temporary binary system. There's a certain elegance to the idea — if it's true, this origin story could resolve some vexing solar-system puzzles, among them the genesis of the Oort Cloud, and the presence of massive captured objects like a Planet Nine.
The paper is published in Astrophysical Journal Letters.
The Oort cloud
Image source: NASA
Scientist believe that surrounding the generally flat solar system is a spherical shell comprised of more than a trillion icy objects more than a mile wide. This is the Oort cloud, and it's likely the source of our solar system's long-term comets — objects that take 200 years or more to orbit the Sun. Inside that shell and surrounding the planets is the Kuiper Belt, a flat disk of scattered objects considered the source of shorter-term comets.
Long-term comets come at us from all directions and astronomers at first suspected their origins to be random. However, it turns out their likely trajectories lead back to a shared aphelion between 2,000 astronomical units (AU) from the Sun to about 100,000 AU, with their different points of origin revealing the shell shape of the Oort cloud along that common aphelion. (An astronomical unit is the distance from the Sun to the Earth.)
No object in the Oort cloud has been directly observed, though Voyager 1 and 2, New Horizons, and Pioneer 10 and 11 are all en route. (The cloud is so far away that all five of the craft will be dead by the time they get there.) To derive a clearer view of the Oort cloud absent actually imagery, scientists utilize computer models based on planetary orbits, solar-system formation simulations, and comet trajectories.
It's generally assumed that the Oort cloud is comprised of debris from the formation of the solar system and neighboring systems, stuff from other systems that we somehow captured. However, says paper co-author Amir Siraj of Harvard, "previous models have had difficulty producing the expected ratio between scattered disk objects and outer Oort cloud objects." As an answer to that, he says, "the binary capture model offers significant improvement and refinement, which is seemingly obvious in retrospect: most sun-like stars are born with binary companions."
"Binary systems are far more efficient at capturing objects than are single stars," co-author Ari Loeb, also of Harvard, explains. "If the Oort cloud formed as [indirectly] observed, it would imply that the sun did in fact have a companion of similar mass that was lost before the sun left its birth cluster."
Working out the source of the objects in the Oort cloud is more than just an interesting astronomical riddle, says Siraj. "Objects in the outer Oort Cloud may have played important roles in Earth's history, such as possibly delivering water to Earth and causing the extinction of the dinosaurs. Understanding their origins is important."
Image source: Caltech/R. Hurt (IPAC)/NASA
The gravitational pull resulting from a binary companion to the Sun may also help explain another intriguing phenomenon: the warping of orbital paths either by something big beyond Pluto — a Planet 9, perhaps — or smaller trans-Neptunian objects closer in, at the outer edges of the Kuiper Belt.
"The puzzle is not only regarding the Oort clouds, but also extreme trans-Neptunian objects, like the potential Planet Nine," Loeb says. "It is unclear where they came from, and our new model predicts that there should be more objects with a similar orbital orientation to [a] Planet Nine."
The authors are looking forward to the upcoming Vera C. Rubin Observatory (VRO) , a Large Synoptic Survey Telescope expected to capture its first light from the cosmos in 2021. It's expected that the VRO will definitively confirm or dismiss the existence of Planet 9. Siraj says, "If the VRO verifies the existence of Planet Nine, and a captured origin, and also finds a population of similarly captured dwarf planets, then the binary model will be favored over the lone stellar history that has been long-assumed."
Missing in action
Lord and Siraj consider it unsurprising that we see no clear sign of the Sun's former companion at this point. Says Loeb, "Passing stars in the birth cluster would have removed the companion from the sun through their gravitational influence. He adds that, "Before the loss of the binary, however, the solar system already would have captured its outer envelope of objects, namely the Oort cloud and the Planet Nine population."
So, where'd it go? Siraj answers, "The sun's long-lost companion could now be anywhere in the Milky Way."
A recent study tested how well the fungi species Cladosporium sphaerospermum blocked cosmic radiation aboard the International Space Station.
- Radiation is one of the biggest threats to astronauts' safety during long-term missions.
- C. sphaerospermum is known to thrive in high-radiation environments through a process called radiosynthesis.
- The results of the study suggest that a thin layer of the fungus could serve as an effective shield against cosmic radiation for astronauts.
Shunk et al.<p>Additionally, the fungus is self-replicating, meaning astronauts would potentially be able to "grow" new radiation shielding on deep-space missions, instead of having to rely on a costly and complicated interplanetary supply chain.</p><p>Still, the researchers weren't sure whether <em>C. sphaerospermum</em> would survive on the space station. Nils J.H. Averesch, a co-author of the <a href="https://www.biorxiv.org/content/10.1101/2020.07.16.205534v1.full.pdf" target="_blank">study published on the preprint server bioRxiv</a>, told <a href="https://www.syfy.com/syfywire/fungus-that-eats-radiation-could-be-cosmic-ray-shield" target="_blank">SYFY WIRE</a>:</p><p style="margin-left: 20px;">"While on Earth, most sources of radiation are gamma- and/or X-rays; radiation in space and on Mars (also known as GCR or galactic cosmic radiation) is of a completely different kind and involves highly energetic particles, mostly protons. This radiation is even more destructive than X- and gamma-rays, so not even survival of the fungus on the ISS was a given."</p>
International Space Station
NASA<p>To be sure, the researchers said more research is needed, and that <em>C. sphaerospermum</em> would likely be used in combination with other radiation-shielding technology aboard spacecraft. But the findings highlight how relatively simple biotechnologies may offer outsized benefits on upcoming space missions.</p><p style="margin-left: 20px;">"Often nature has already developed blindly obvious yet surprisingly effective solutions to engineering and design problems faced as humankind evolves – C. sphaerospermum and melanin could thus prove to be invaluable in providing adequate protection of explorers on future missions to the Moon, Mars and beyond," the researchers wrote.</p>
The Sun, as its never been seen before.
How to take a picture of a giant ball of fire<p>Situated 77,000,000 kilometers (48,000,000 miles) from Earth, roughly halfway to the Sun, the Solar Orbiter's cameras have taken high-quality images from a closer vantage point than any camera ever. More importantly, they can take pictures in ultraviolet light, which is highly filtered by Earth's atmosphere and challenging to do as well without being in space.</p><p>The images, seen below, are stunning.</p>
The arrow points to a "nanoflare" approximately 700 km across.
SOLAR ORBITER/EUI TEAM (ESA & NASA)
These images show the sun's appearance at a wavelength of 17 nanometers, which is in the extreme ultraviolet region of the electromagnetic spectrum. Images at this wavelength reveal the upper atmosphere of the sun, the corona, with a temperature of around one million degrees. (quoted from https://phys.org/news/2020-07-close-ups-sun.html)
Credit: Solar Orbiter/EUI Team (ESA & NASA); CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL