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    • By NASA
      3 min read
      What’s Made in a Thunderstorm and Faster Than Lightning? Gamma Rays!
      A flash of lightning. A roll of thunder. These are normal stormy sights and sounds. But sometimes, up above the clouds, stranger things happen. Our Fermi Gamma-ray Space Telescope has spotted bursts of gamma rays – some of the highest-energy forms of light in the universe – coming from thunderstorms. Gamma rays are usually found coming from objects with crazy extreme physics like neutron stars and black holes. So why is Fermi seeing them come from thunderstorms?
      About a thousand times a day, thunderstorms fire off fleeting bursts of some of the highest-energy light naturally found on Earth. These events, called terrestrial gamma-ray flashes, last less than a millisecond and produce gamma rays with tens of millions of times the energy of visible light. NASA’s Goddard Space Flight Center Thunderstorms form when warm, damp air near the ground starts to rise and encounters colder air. As the warm air rises, moisture condenses into water droplets. The upward-moving water droplets bump into downward-moving ice crystals, stripping off electrons and creating a static charge in the cloud.
      Updrafts and downdrafts within thunderstorms force rain, snow and ice to collide and acquire an electrical charge, which can cause lightning. Under just the right conditions, the fast-moving electrons can create a terrestrial gamma-ray flash. NASA’s Goddard Space Flight Center The top of the storm becomes positively charged, and the bottom becomes negatively charged, like two ends of a battery. Eventually the opposite charges build enough to overcome the insulating properties of the surrounding air – and zap! You get lightning.
      This illustration shows electrons accelerating upwards from a thunderhead. NASA’s Goddard Space Flight Center Scientists suspect that lightning reconfigures the cloud’s electrical field. In some cases, this allows electrons to rush toward the upper part of the storm at nearly the speed of light. That makes thunderstorms the most powerful natural particle accelerators on Earth!
      Interactions with matter can produce gamma rays and vice versa, as shown here in this illustration. High-energy electrons traveling close to the speed of light can be deflected by passing near an atom or molecule, producing a gamma ray. And a gamma ray passing through the electron shell of an atom transforms into two particles: an electron and a positron. NASA’s Goddard Space Flight Center When those electrons run into air molecules, they emit a terrestrial gamma-ray flash, which means that thunderstorms are creating some of the highest energy forms of light in the universe. But that’s not all – thunderstorms can also produce antimatter! Yep, you read that correctly! Sometimes, a gamma ray will run into an atom and produce an electron and a positron, which is an electron’s antimatter opposite!
      NASA’s Fermi Gamma-ray Space Telescope, illustrated here, scans the entire sky every three hours as it orbits Earth. NASA’s Goddard Space Flight Center Conceptual Image Lab Fermi can spot terrestrial gamma-ray flashes within 500 miles (800 kilometers) of the location directly below the spacecraft. It does this using an instrument called the Gamma-ray Burst Monitor which is primarily used to watch for spectacular flashes of gamma rays coming from the universe.
      Visualization of ten years of Fermi observations of terrestrial gamma-ray flashes. NASA’s Goddard Space Flight Center There are an estimated 1,800 thunderstorms occurring on Earth at any given moment. Over its first 10 years in space, Fermi spotted about 5,000 terrestrial gamma-ray flashes. But scientists estimate that there are 1,000 of these flashes every day – we’re just seeing the ones that are within 500 miles of Fermi’s regular orbits, which don’t cover the U.S. or Europe.
      The map above shows all the flashes Fermi saw between 2008 and 2018. (Notice there’s a blob missing over the lower part of South America. That’s the South Atlantic Anomaly, a portion of the sky where radiation affects spacecraft and causes data glitches.)
      Storm clouds produce some of the highest-energy light naturally made on Earth: terrestrial gamma-ray flashes. The tropical disturbance that would later become Hurricane Julio in 2014 produced four flashes within 100 minutes, with a fifth the next day. NASA’s Goddard Space Flight Center Fermi has also spotted terrestrial gamma-ray flashes coming from individual tropical weather systems. In 2014 Tropical Storm Julio produced four flashes in just 100 minutes!

      Last Updated Feb 05, 2024 Related Terms
      Black Holes Earth Extreme Weather Events Fermi Gamma-Ray Space Telescope Gamma Rays Gamma-Ray Bursts Neutron Stars The Universe Weather and Atmospheric Dynamics Explore More
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    • By NASA
      5 min read
      How is the 2024 Total Solar Eclipse Different than the 2017 Eclipse?
      On April 8, the Moon’s shadow will sweep across the United States, as millions will view a total solar eclipse. For many, preparing for this event brings memories of the magnificent total solar eclipse on Aug. 21, 2017.
      The total solar eclipse on Aug. 21, 2017, was photographed from Madras, Oregon. The black circle in the middle is the Moon. Surrounding it are white streams of light belonging to the Sun’s outer atmosphere, called the corona. NASA/Aubrey Gemignani In 2017, an estimated 215 million U.S. adults (88% of U.S. adults) viewed the solar eclipse, either directly or electronically. They experienced the Moon pass in front of the Sun, blocking part or all of our closest star’s bright face. The eclipse in 2024 could be even more exciting due to differences in the path, timing, and scientific research.
      Wider, More Populated Path
      The path of totality – where viewers can see the Moon totally block the Sun, revealing the star’s outer atmosphere, called the corona – is much wider during the upcoming total solar eclipse than it was during the eclipse in 2017. As the Moon orbits Earth, its distance from our planet varies. During the 2017 total solar eclipse, the Moon was a little bit farther away from Earth than it will be during upcoming total solar eclipse, causing the path of that eclipse to be a little skinnier. In 2017, the path ranged from about 62 to 71 miles wide. During the April eclipse, the path over North America will range between 108 and 122 miles wide – meaning at any given moment, this eclipse covers more ground. 
      The 2024 eclipse path will also pass over more cities and densely populated areas than the 2017 path did. This will make it easier for more people to see totality. An estimated 31.6 million people live in the path of totality this year, compared to 12 million in 2017. An additional 150 million people live within 200 miles of the path of totality.
      This map shows the path of the 2017 total solar eclipse, crossing from Oregon to South Carolina, and the 2024 total solar eclipse, crossing from Mexico into Texas, up to Maine, and exiting over Canada. To see a map showing which areas will experience the partial solar eclipse and which areas will experience the total solar eclipse on April 8, 2024, click the arrows.
      Ernest Wright/NASA’s Scientific Visualization Studio This map illustrates the paths of the Moon’s shadow across the U.S. during the 2024 total solar eclipse. On April 8, 2024, a total solar eclipse will cross North and Central America creating a path of totality. During a total solar eclipse, the Moon completely blocks the Sun while it passes between the Sun and Earth. The sky will darken as if it were dawn or dusk and those standing in the path of totality may see the Sun’s outer atmosphere (the corona) if weather permits. To see a map comparing the 2024 eclipse and the 2017 eclipse paths, click the arrows.
      NASA/Scientific Visualization Studio/Michala Garrison; Eclipse Calculations By Ernie Wright, NASA Goddard Space Flight Center

      You don’t need to live within the path of totality to see the eclipse – in April, 99% of people who reside in the United States will be able to see the partial or total eclipse from where they live. Every contiguous U.S. state, plus parts of Alaska and Hawaii, will experience at least a partial solar eclipse.
      Longer Time in Totality
      In April, totality will last longer than it did in 2017. Seven years ago, the longest period of totality was experienced near Carbondale, Illinois, at 2 minutes, 42 seconds. 
      For the upcoming eclipse, totality will last up to 4 minutes, 28 seconds, in an area about 25 minutes northwest of Torreón, Mexico. As the eclipse enters Texas, totality will last about 4 minutes, 26 seconds at the center of the eclipse’s path. Durations longer than 4 minutes stretch as far north as Economy, Indiana. Even as the eclipse exits the U.S. and enters Canada, the eclipse will last up to 3 minutes, 21 seconds. 
      During any total solar eclipse, totality lasts the longest near the center of the path, widthwise, and decreases toward the edge. But those seeking totality shouldn’t worry that they need to be exactly at the center. The time in totality falls off pretty slowly until you get close to the edge.
      Heightened Solar Activity
      NASA/ESA’s Solar and Heliospheric Observatory (SOHO) captured this video of a coronal mass ejection on March 13, 2023. NASA/Aubrey Gemignani

      Every 11 years or so, the Sun’s magnetic field flips, causing a cycle of increasing then decreasing solar activity. During solar minimum, there are fewer giant eruptions from the Sun, such as solar flares and coronal mass ejections. But during solar maximum, the Sun becomes more active.
      In 2017, the Sun was nearing solar minimum. Viewers of the total eclipse could see the breathtaking corona – but since the Sun was quiet, streamers flowing into the solar atmosphere were restricted to just the equatorial regions of the star. The Sun is more magnetically symmetrical during solar minimum, causing this simpler appearance. During the 2024 eclipse, the Sun will be in or near solar maximum, when the magnetic field is more like a tangled hairball. Streamers will likely be visible throughout the corona. In addition to that, viewers will have a better chance to see prominences – which appear as bright, pink curls or loops coming off the Sun.
      With lucky timing, there could even be a chance to see a coronal mass ejection – a large eruption of solar material – during the eclipse.
      Expanded Scientific Research
      The third rocket launched on Oct. 14, 2023, during the annular solar eclipse leaves the launch pad.  WSMR Army Photo During the total eclipse in 2024, NASA is funding several research initiatives that build on research done during the 2017 eclipse. The projects, which are led by researchers at different academic institutions, will study the Sun and its influence on Earth with a variety of instruments, including cameras aboard high-altitude research planes, ham radios, and more. In addition to those projects, instruments that were launched during the 2023 annular solar eclipse on three sounding rockets will again be launched during the upcoming total solar eclipse.
      Two spacecraft designed to study the Sun’s corona – NASA’s Parker Solar Probe and ESA (European Space Agency) and NASA’s Solar Orbiter – have also launched since the 2017 solar eclipse. These missions will provide insights from the corona itself, while viewers on Earth see it with their own eyes, providing an exciting opportunity to combine and compare viewpoints.
      To learn more about the 2024 total solar eclipse and how you can safely watch it, visit NASA’s eclipse website.
      By Abbey Interrante
      NASA’s Goddard Space Flight Center, Greenbelt, Md. 
      Special thanks to Michael Zeiler for his calculations on the populations in the eclipse path.
      The 2017 total solar eclipse viewing analysis was conducted by Professor Jon D. Miller of the University of Michigan. This study was supported by a collaborative agreement between the University of Michigan and the National Aeronautics and Space Administration (award NNX16AC66A).
      View the full article
    • By European Space Agency
      The first commercial flights of a programme that uses Iris satellite technology to help modernise air traffic management and reduce carbon emissions have taken place.
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    • By NASA
      Jakobshavn Isbrae, a glacier on Greenland’s western coast, is shown in imagery taken on Sept. 5, 1985, by the Landsat 5 satellite. Jakobshavn receded from 1985 to 2022, losing about 97 billion tons (88 billion metric tons) of ice, a recent study of the Greenland Ice Sheet’s glacial retreat found.NASA/USGS A Landsat 8 image from Sept. 4, 2022, shows Jakobshavn Isbrae breaking at its edge. A recent study found that from 1985 to 2022 the Greenland Ice Sheet shed about 1,140 billion tons (1,034 billion metric tons) – one-fifth more mass than previously estimated.NASA/USGS A new, comprehensive analysis of satellite data finds that majority of glaciers on the landmass have retreated significantly.
      The Greenland Ice Sheet has shed about one-fifth more ice mass in the past four decades than previously estimated, researchers at NASA’s Jet Propulsion Laboratory in Southern California reported in a new paper. The majority of glaciers on the landmass have retreated significantly, and icebergs are falling into the ocean at an accelerating rate. This additional ice loss has had only an indirect impact on sea levels, but could hold implications for ocean circulation in the future.
      Published in Nature on Jan. 17, the analysis offers a comprehensive look at retreat around the edges of the entire ice sheet from 1985 to 2022, drawing from nearly a quarter million pieces of satellite data on glacier positions. Of the 207 glaciers in the study, 179 retreated significantly since 1985, 27 held steady, and one advanced slightly.
      Most of the ice loss came from below sea level, in fjords on Greenland’s periphery. Once occupied by ancient glacial ice, many of these deep coastal valleys have filled with seawater – meaning the ice that broke off made little net contribution to sea level. But the loss likely accelerated the movement of ice flowing down from higher elevations, which in turn added to sea level rise.
      “When the ice at the end of a glacier calves and retreats, it’s like pulling the plug out of the fjord, which lets ice drain into the ocean faster,” said Chad Greene, a glacier scientist at JPL and the study’s lead author.
      Accounting for Glacial Retreat
      For decades researchers have studied the Greenland Ice Sheet’s direct contributions to global sea level rise through ice flow and melting. Scientists participating in the international Ice sheet Mass Balance Inter-comparison Exercise (IMBIE) estimated that the ice sheet had lost 5,390 billion tons (4,890 billion metric tons) between 1992 and 2020, adding about 0.531 inches (13.5 millimeters) to global mean sea level, according to the Intergovernmental Panel on Climate Change.
      Imagery from the Landsat 7 satellite taken on Aug. 5, 1999, shows Zachariae Isstrom, a glacier in northeast Greenland. This glacier lost about 176 billion tons (160 billion metric tons) of ice during its retreat from 1985 to 2022, a recent study found.NASA/USGS A Landsat 8 image from Aug. 22, 2022, shows icebergs breaking from Zachariae Isstrom. From 1985 to 2022, as icebergs fell into the ocean at an accelerating rate, the Greenland Ice Sheet shed about 1,140 billion tons (1,034 billion metric tons) – one-fifth more mass than previously estimated.NASA/USGS But the IMBIE measurements do not account for ice lost due to the retreat of terminal glaciers along the edges of Greenland. (These glacier edges were already in the water, whether submerged or floating.) The new study quantifies this amount: For the 1985 to 2022 period in the new paper, the ice sheet was estimated to have lost about 1,140 billion tons (1,034 billion metric tons) – 21% more mass lost than in the IMBIE assessment.
      Although it doesn’t add to sea levels, the additional ice represents a significant influx of fresh water to the ocean. Recent studies have suggested that changes in the salinity of the North Atlantic Ocean from melting icebergs could weaken the Atlantic Meridional Overturning Circulation, part of the global “conveyor belt” of currents that transport heat and salt around the ocean. This could influence weather patterns worldwide, as well as affect ecosystems, the authors said.  
      A Comprehensive View of Glacial Retreat
      Icebergs have tumbled from Greenland’s glaciers for thousands of years as part of a natural cycle that typically balanced glacier growth in the winter with melting and retreat in the summer. The new study finds that ice retreat has far outpaced growth throughout the 21st century.  
      The researchers also found that Greenland’s ice extent remained relatively steady from 1985 to 2000, then started a marked recession that continues to this day.
      The data showed a glacier in northeast Greenland called Zachariae Isstrom lost the most ice, dropping 176 billion tons (160 billion metric tons) of mass due to retreat. It was followed by Jakobshavn Isbrae on the western coast, which lost an estimated 97 billion tons (88 billion metric tons), and Humboldt Gletscher in the northwest, which lost 96 billion tons (87 billion metric tons).
      Only one glacier, Qajuuttap Sermia in southern Greenland, experienced any growth over the study period, but its gains were too small to offset the losses from other glaciers.
      The researchers also found that glaciers with the largest seasonal fluctuations in the position of their ice front experienced the greatest overall retreat. The correlation suggests the glaciers that are most sensitive to warming each summer will be most impacted by climate change in the coming decades.
      The discovery of a large-scale pattern of glacier retreat and its link to glacier sensitivity on seasonal time scales was the result of a big-data synthesis that looks at all parts of the ice sheet over time, said JPL cryosphere scientist Alex Gardner, a co-author of the paper. Scientists drew from five publicly available datasets that cumulatively tracked the month-to-month positions of 236,328 glacier edges as detected, either manually or by computer algorithms, in images collected by optical and radar satellites.
      “Previously, we had bits and pieces – lots of local studies,” Gardner said. “But what this study offers is a systematic and comprehensive view that has led to some pretty significant insights that we didn’t have about the ice sheet before.”
      News Media Contacts
      Andrew Wang / Jane J. Lee
      Jet Propulsion Laboratory, Pasadena, Calif.
      626-379-6874 / 818-354-0307
      andrew.wang@jpl.nasa.gov / jane.j.lee@jpl.nasa.gov
      Last Updated Jan 17, 2024 Related Terms
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    • By NASA
      1 min read
      Artificial Intelligence Plus Your Cell Phone Means Better Maps of Earth!
      GLOBE Observer data from various locations showing four directional views: west, north, south, and east.  Credit: Huang et al. 2023, International Journal of Applied Earth Observation and Geoinformation, Volume 122, 103382 In 2019, the GLOBE Land Cover project began asking volunteers to help map planet Earth by taking photos of their surroundings facing multiple directions, including north, south, east and west. Now, a new paper by Huang et al. demonstrates how to combine these images using Artificial Intelligence (AI).  The paper compares this “multi-view” approach with the old single-view approach–and finds that the multi-view capabilities of the GLOBE Observer app, processed with AI, enable much more accurate mapping. 
      “We are thrilled about our recent discovery! We’ve observed that the current AI model is increasingly exhibiting human-like behavior, adept at integrating multiple perspectives, synthesizing them, and striving to derive meaning from these views.”
      Xiao Huang
      The paper’s lead author
      “We are thrilled about our recent discovery!” said Xiao Huang, the paper’s lead author.  “We’ve observed that the current AI model is increasingly exhibiting human-like behavior, adept at integrating multiple perspectives, synthesizing them, and striving to derive meaning from these views.”
      The most detailed satellite-based maps of our whole planet still can’t show details smaller than hundreds of meters [about 330 feet]. That means that a park in a city may be too small to show up on the global map. When you use the GLOBE Observer: Land Cover app, you help scientists fill in local gaps and contribute to consistent, detailed global maps that should us how our world is changing. 
      Grab your smartphone and join the project!
      Facebook logo @DoNASAScience @DoNASAScience Share

      Last Updated Dec 04, 2023 Related Terms
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