How can US adapt to threat of water shortages?

Drought-induced drops in water levels have been extreme in some reservoirs such as Lake Mead in the southwestern U.S. Image via U.S. Geological Survey.

Over the 21st century, serious water shortages are likely in several areas of the U.S. unless actions are taken soon to adapt to future changes in water resources, according to a new study.

The study, published February 28, 2018 in Earth’s Future, not only looked at future trends in water supply and water demand across the contiguous U.S., but also examined which adaptation measures would be the most effective to use. The analysis showed that reductions in water use for agriculture will likely be one of our best adaptation tools.

Water shortages inevitably occur when the demand for water outpaces the water supply. In the U.S., water demand is expected to broadly increase as the population grows from its current size of approximately 328 million people to 514 million people in 2100. Meanwhile, water supplies will undergo variable changes in response to climate change. In some communities, the supplies are expected to drop as temperatures warm and droughts become more common. In other communities, supplies could increase if the precipitation increases as expected, but rising temperatures will still boost water evaporation rates and put a strain on water supplies in many areas.

Of the 204 watersheds examined in the U.S., shortages will likely occur in 83 basins in the near future (2021–2045), 92 basins in the mid-future (2046–2070), and 96 basins in the far future (2071–2095) if no adaptation measures are taken, according to the new study. These shortages are projected to happen even with continued improvements in water efficiency on pace with the rate at which water efficiency is changing today.

Water shortage frequencies that can be expected in U.S. watersheds in the mid-future (2046–2070) if no adaptation measures are taken. Image via Brown et al. (2019) Earth’s Future, vol. 7.

To stave off the shortages, the scientists used their water resource model to examine how effective several measures would be, including reservoir storage enhancements, instream flow reductions, and groundwater depletion among others. Reservoir storage enhancements, which can be used to store water when it is plentiful for later times when it is scarce, were found to be largely ineffective for many of the drought prone regions where water for such enhancements is simply unavailable. As for diverting water from streams and rivers and tapping into more groundwater supplies, these approaches would help to reduce shortages but would carry heavy external costs. For example, excessive water withdrawals could lead to the collapse of fish populations. Hence, the authors caution against a heavy reliance on their use while acknowledging that pressure to employ these options will likely increase in the future.

Of all the options studied, reductions in water use for agriculture appeared to be the most promising for preventing water shortages. This could potentially be achieved by making drastic improvements to irrigation efficiency beyond the current pace of technological advances as well as abandoning irrigation practices on low-value crops, the scientists say.

Clearly, the future choices that many communities will have to make to maintain adequate water supplies will not be easy, as demonstrated by this sobering new study. Comprehensive planning studies such as this one can help guide communities to the best options. Future studies to explore other water conservation options would also be worthwhile. Sandra Postel, an expert on water resources issues, is championing a technologically smarter and more natural approach to fixing our broken water cycles, which could involve solutions like precision irrigation systems and wetland restoration. She recently wrote in Trend:

It’s tempting to try to solve our water problems with bigger dams, deeper wells, and longer water transfers. But as Albert Einstein reminded us decades ago, ‘We can’t solve problems by using the same kind of thinking we used when we created them.’ That means thinking differently about how we use, manage, and value water. And it means figuring out how to repair and replenish the water cycle even as we prosper. It’s a tall order. But some pioneers are showing the way.

Source: Adaptation to Future Water Shortages in the United States Caused by Population Growth and Climate Change by Thomas Brown, Vinod Mahat, and Jorge A. Ramirez

Bottom line: Future water shortages in parts of the U.S. are likely given increasing water demands and decreasing water supplies. A new study suggests reductions in water use for agriculture may be one of the best approaches for avoiding future water shortages.

from EarthSky https://ift.tt/2HWgB5u

Drought-induced drops in water levels have been extreme in some reservoirs such as Lake Mead in the southwestern U.S. Image via U.S. Geological Survey.

Over the 21st century, serious water shortages are likely in several areas of the U.S. unless actions are taken soon to adapt to future changes in water resources, according to a new study.

The study, published February 28, 2018 in Earth’s Future, not only looked at future trends in water supply and water demand across the contiguous U.S., but also examined which adaptation measures would be the most effective to use. The analysis showed that reductions in water use for agriculture will likely be one of our best adaptation tools.

Water shortages inevitably occur when the demand for water outpaces the water supply. In the U.S., water demand is expected to broadly increase as the population grows from its current size of approximately 328 million people to 514 million people in 2100. Meanwhile, water supplies will undergo variable changes in response to climate change. In some communities, the supplies are expected to drop as temperatures warm and droughts become more common. In other communities, supplies could increase if the precipitation increases as expected, but rising temperatures will still boost water evaporation rates and put a strain on water supplies in many areas.

Of the 204 watersheds examined in the U.S., shortages will likely occur in 83 basins in the near future (2021–2045), 92 basins in the mid-future (2046–2070), and 96 basins in the far future (2071–2095) if no adaptation measures are taken, according to the new study. These shortages are projected to happen even with continued improvements in water efficiency on pace with the rate at which water efficiency is changing today.

Water shortage frequencies that can be expected in U.S. watersheds in the mid-future (2046–2070) if no adaptation measures are taken. Image via Brown et al. (2019) Earth’s Future, vol. 7.

To stave off the shortages, the scientists used their water resource model to examine how effective several measures would be, including reservoir storage enhancements, instream flow reductions, and groundwater depletion among others. Reservoir storage enhancements, which can be used to store water when it is plentiful for later times when it is scarce, were found to be largely ineffective for many of the drought prone regions where water for such enhancements is simply unavailable. As for diverting water from streams and rivers and tapping into more groundwater supplies, these approaches would help to reduce shortages but would carry heavy external costs. For example, excessive water withdrawals could lead to the collapse of fish populations. Hence, the authors caution against a heavy reliance on their use while acknowledging that pressure to employ these options will likely increase in the future.

Of all the options studied, reductions in water use for agriculture appeared to be the most promising for preventing water shortages. This could potentially be achieved by making drastic improvements to irrigation efficiency beyond the current pace of technological advances as well as abandoning irrigation practices on low-value crops, the scientists say.

Clearly, the future choices that many communities will have to make to maintain adequate water supplies will not be easy, as demonstrated by this sobering new study. Comprehensive planning studies such as this one can help guide communities to the best options. Future studies to explore other water conservation options would also be worthwhile. Sandra Postel, an expert on water resources issues, is championing a technologically smarter and more natural approach to fixing our broken water cycles, which could involve solutions like precision irrigation systems and wetland restoration. She recently wrote in Trend:

It’s tempting to try to solve our water problems with bigger dams, deeper wells, and longer water transfers. But as Albert Einstein reminded us decades ago, ‘We can’t solve problems by using the same kind of thinking we used when we created them.’ That means thinking differently about how we use, manage, and value water. And it means figuring out how to repair and replenish the water cycle even as we prosper. It’s a tall order. But some pioneers are showing the way.

Source: Adaptation to Future Water Shortages in the United States Caused by Population Growth and Climate Change by Thomas Brown, Vinod Mahat, and Jorge A. Ramirez

Bottom line: Future water shortages in parts of the U.S. are likely given increasing water demands and decreasing water supplies. A new study suggests reductions in water use for agriculture may be one of the best approaches for avoiding future water shortages.

from EarthSky https://ift.tt/2HWgB5u

NASA proposes mission to Neptune moon Triton

Neptune’s largest moon Triton as seen by Voyager 2 during its flyby in 1989. The south polar cap – with its nitrogen geysers – is in the bottom portion of this image and Triton’s famous “cantaloupe terrain” is at the top. Image via NASA/JPL/USGS.

Over the past few decades, robotic missions to the outer solar system have shown that water worlds seem to be quite common. We’ve seen multiple moons with an icy surface crust and, scientists believe, a liquid water ocean below. Jupiter’s moon Europa and Saturn’s moons Enceladus and Titan are among the most intriguing of these water moons. Even Pluto might have a subsurface ocean and evidence suggests that the dwarf planet Ceres had one as well, in the past.

But there’s another compelling world that hasn’t been visited again yet for decades – and should be – according to NASA. That is Neptune’s largest moon Triton. On March 19, 2019, at the Lunar and Planetary Science Conference 2019 (LPSC 50), NASA announced a proposed flyby mission called Trident to investigate whether Triton does, as suspected, have a subsurface ocean, an ocean with the potential for habitability.

The flyby, similar to the New Horizons flyby of Pluto in 2015, would occur in 2038. The proposal is outlined in two papers, available here and here.

The mission, if approved, would be part of NASA’s Discovery Program, which supports lower-cost missions for under $500 million. Those missions are launched every two years, with the InSight lander on Mars being the most recent.

Titan is one of many known and suspected ocean worlds. It is also 1 of 3 bodies known or thought to have active cryovolcanic plumes, and is believed to be a captured Kuiper Belt Object (KBO). Image via L. M. Prockter et al./LPSC/USRA/JPL/SwRI.

A flyby mission would be a good way to determine if Triton’s ocean is really there and to get a good idea as to what the conditions are like without having to spend a lot more money on a flagship mission such as Cassini, which explored Saturn and its moons from 2004 until 2017. As explained by Louise Prockter, director of the Lunar and Planetary Institute (LPI) in Houston and the principal investigator of the proposed mission:

The time is now to do it at a low cost. And we will investigate whether it is a habitable world, which is of huge importance.

Such a mission would be well-equipped to examine Triton’s unique surface features and assess the habitability of the ocean below. The mission concept, as outlined in one of the papers at LPSC:

We have identified an optimized solution to enable a New Horizons-like fast flyby of Triton in 2038 that appears at this preliminary stage to fit within the Discovery 2019 cost cap. The mission concept uses high heritage components and builds on the New Horizons concepts of operation. Our overarching science goals are to determine: (1) if Triton has a subsurface ocean; (2) why Triton has the youngest surface of any icy world in the solar system, and which processes are responsible for this; and (3) why Triton’s ionosphere is so unusually intense. If an ocean is present, we seek to determine its properties and whether the ocean interacts with the surface environment. Trident will pass within 500 km of Triton, inside its atmosphere, imaging the surface, sampling its ionosphere, and getting sufficiently close as to permit highly detailed magnetic induction measurements. Passage through a total eclipse makes possible atmospheric occultations. Trident’s focus on the internal structure, surface geology, organic processes, and atmospheric characteristics of Triton closely align with key priorities established in the NRC 2013 Planetary Decadal Survey and the NASA 2018 Roadmaps to Ocean Worlds white paper.

Planned trajectory route of Trident from Earth to Triton. Image via K. L. Mitchell et al./JPL/LPSC/USRA.

According to Amanda Hendrix of the Planetary Science Institute (PSI) in Tucson, Arizona, and a leader of the Roadmap study:

Triton shows tantalizing hints at being active and having an ocean. It is a three-for-one target, because you can visit the Neptune system, visit this interesting ocean world, and also visit a Kuiper Belt Object without having to go all the way out there.

Along the way, Trident would also visit Venus and Jupiter’s moon Io – the most volcanically active body in the solar system. Although the current Juno orbiter has been able to view Io from a distance, the moon hasn’t been studied up close since the Voyager 2 mission in 1979. The last time that Triton was observed by a spacecraft was in 1989, also by Voyager 2. Although “only” a flyby as well, the Trident mission would be much more advanced than Voyager 2, according to Karl Mitchell, proposed project scientist for the mission, speaking to The New York Times:

We are comparing with the Voyager encounter in 1989, which was built on early 1970s technology, essentially a television camera attached to a fax machine.

A closer view of Triton’s “cantaloupe terrain.” Image via NASA/JPL/Wikipedia.

Dark plumes from nitrogen geysers on Triton. Image via NASA/JPL.

Voyager 2’s ethereal view of Neptune (top) and Triton (bottom) in 1989. Image via NASA/JPL.

Even apart from the possible ocean, Triton is a fascinating and active world, with geyser-like cryovolcanoes venting dark plumes of nitrogen gas, tectonic “cantaloupe terrain,” few craters and a tenuous nitrogen atmosphere. It is so cold on the surface, -391 degrees Fahrenheit (-235 degrees Celsius), that most of its nitrogen condenses on the surface as frost. It is also the only large moon – 1,680 miles (2,700 kilometers) in diameter – to orbit in the opposite direction of its planet’s rotation. Like our own moon, it is in synchronous rotation, keeping one side always facing Neptune.

Triton was discovered on October 10, 1846, by British astronomer William Lassell, just 17 days after Neptune itself was discovered. Triton was named after the son of Poseidon, the Greek god comparable to the Roman Neptune.

Bottom line: As a possible ocean moon, Triton is a tantalizing destination for future robotic missions. If approved, Trident would be the first spacecraft to explore this mysterious world in decades. What new surprises are waiting to be discovered?

Source: Implementation of Trident: A Discovery-Class Mission to Triton

Source: Exploring Triton with Trident: A Discovery-Class Mission

Via The New York Times

from EarthSky https://ift.tt/2HNTlY6

Neptune’s largest moon Triton as seen by Voyager 2 during its flyby in 1989. The south polar cap – with its nitrogen geysers – is in the bottom portion of this image and Triton’s famous “cantaloupe terrain” is at the top. Image via NASA/JPL/USGS.

Over the past few decades, robotic missions to the outer solar system have shown that water worlds seem to be quite common. We’ve seen multiple moons with an icy surface crust and, scientists believe, a liquid water ocean below. Jupiter’s moon Europa and Saturn’s moons Enceladus and Titan are among the most intriguing of these water moons. Even Pluto might have a subsurface ocean and evidence suggests that the dwarf planet Ceres had one as well, in the past.

But there’s another compelling world that hasn’t been visited again yet for decades – and should be – according to NASA. That is Neptune’s largest moon Triton. On March 19, 2019, at the Lunar and Planetary Science Conference 2019 (LPSC 50), NASA announced a proposed flyby mission called Trident to investigate whether Triton does, as suspected, have a subsurface ocean, an ocean with the potential for habitability.

The flyby, similar to the New Horizons flyby of Pluto in 2015, would occur in 2038. The proposal is outlined in two papers, available here and here.

The mission, if approved, would be part of NASA’s Discovery Program, which supports lower-cost missions for under $500 million. Those missions are launched every two years, with the InSight lander on Mars being the most recent.

Titan is one of many known and suspected ocean worlds. It is also 1 of 3 bodies known or thought to have active cryovolcanic plumes, and is believed to be a captured Kuiper Belt Object (KBO). Image via L. M. Prockter et al./LPSC/USRA/JPL/SwRI.

A flyby mission would be a good way to determine if Triton’s ocean is really there and to get a good idea as to what the conditions are like without having to spend a lot more money on a flagship mission such as Cassini, which explored Saturn and its moons from 2004 until 2017. As explained by Louise Prockter, director of the Lunar and Planetary Institute (LPI) in Houston and the principal investigator of the proposed mission:

The time is now to do it at a low cost. And we will investigate whether it is a habitable world, which is of huge importance.

Such a mission would be well-equipped to examine Triton’s unique surface features and assess the habitability of the ocean below. The mission concept, as outlined in one of the papers at LPSC:

We have identified an optimized solution to enable a New Horizons-like fast flyby of Triton in 2038 that appears at this preliminary stage to fit within the Discovery 2019 cost cap. The mission concept uses high heritage components and builds on the New Horizons concepts of operation. Our overarching science goals are to determine: (1) if Triton has a subsurface ocean; (2) why Triton has the youngest surface of any icy world in the solar system, and which processes are responsible for this; and (3) why Triton’s ionosphere is so unusually intense. If an ocean is present, we seek to determine its properties and whether the ocean interacts with the surface environment. Trident will pass within 500 km of Triton, inside its atmosphere, imaging the surface, sampling its ionosphere, and getting sufficiently close as to permit highly detailed magnetic induction measurements. Passage through a total eclipse makes possible atmospheric occultations. Trident’s focus on the internal structure, surface geology, organic processes, and atmospheric characteristics of Triton closely align with key priorities established in the NRC 2013 Planetary Decadal Survey and the NASA 2018 Roadmaps to Ocean Worlds white paper.

Planned trajectory route of Trident from Earth to Triton. Image via K. L. Mitchell et al./JPL/LPSC/USRA.

According to Amanda Hendrix of the Planetary Science Institute (PSI) in Tucson, Arizona, and a leader of the Roadmap study:

Triton shows tantalizing hints at being active and having an ocean. It is a three-for-one target, because you can visit the Neptune system, visit this interesting ocean world, and also visit a Kuiper Belt Object without having to go all the way out there.

Along the way, Trident would also visit Venus and Jupiter’s moon Io – the most volcanically active body in the solar system. Although the current Juno orbiter has been able to view Io from a distance, the moon hasn’t been studied up close since the Voyager 2 mission in 1979. The last time that Triton was observed by a spacecraft was in 1989, also by Voyager 2. Although “only” a flyby as well, the Trident mission would be much more advanced than Voyager 2, according to Karl Mitchell, proposed project scientist for the mission, speaking to The New York Times:

We are comparing with the Voyager encounter in 1989, which was built on early 1970s technology, essentially a television camera attached to a fax machine.

A closer view of Triton’s “cantaloupe terrain.” Image via NASA/JPL/Wikipedia.

Dark plumes from nitrogen geysers on Triton. Image via NASA/JPL.

Voyager 2’s ethereal view of Neptune (top) and Triton (bottom) in 1989. Image via NASA/JPL.

Even apart from the possible ocean, Triton is a fascinating and active world, with geyser-like cryovolcanoes venting dark plumes of nitrogen gas, tectonic “cantaloupe terrain,” few craters and a tenuous nitrogen atmosphere. It is so cold on the surface, -391 degrees Fahrenheit (-235 degrees Celsius), that most of its nitrogen condenses on the surface as frost. It is also the only large moon – 1,680 miles (2,700 kilometers) in diameter – to orbit in the opposite direction of its planet’s rotation. Like our own moon, it is in synchronous rotation, keeping one side always facing Neptune.

Triton was discovered on October 10, 1846, by British astronomer William Lassell, just 17 days after Neptune itself was discovered. Triton was named after the son of Poseidon, the Greek god comparable to the Roman Neptune.

Bottom line: As a possible ocean moon, Triton is a tantalizing destination for future robotic missions. If approved, Trident would be the first spacecraft to explore this mysterious world in decades. What new surprises are waiting to be discovered?

Source: Implementation of Trident: A Discovery-Class Mission to Triton

Source: Exploring Triton with Trident: A Discovery-Class Mission

Via The New York Times

from EarthSky https://ift.tt/2HNTlY6

Large Magellanic Cloud over Neill Island

View at EarthSky Community Photos. | Photo taken in February 2019 by Aman Chokshi.

Aman Chokshi said he was walking along the coast of Neill Island, India, last month, when he noticed a faint bright patch along the horizon. He wrote:

I’ve always believed that the Large Magellanic Cloud was only visible from the Southern Hemisphere. My sky map showed that the Large Magellanic Cloud was barely 10 degrees above the horizon, below the bright star Canopus. I immediately set up my camera, and took a long exposure to see if I could capture it.

The sky was lit with brilliant airglow, within which a bright density of stars. So thrilled to have shot this!

By the way, Aman also said:

I shot this using an old Canon film lens, 50mm f/1.4 stopped down to f/4. The sky is a stack of 90x8s images, while the foreground is a stack of 3x30s images. I manually aligned the reflected stars in the tide pools, in Photoshop.

Thank you, Aman!

Read more: The spectacular Large Magellanic Cloud

Neill Island, in the Indian Ocean. Map via Wikipedia.

Bottom line: Large Magellanic Cloud, captured from Neill Island, India.

from EarthSky https://ift.tt/2WtlhUi

View at EarthSky Community Photos. | Photo taken in February 2019 by Aman Chokshi.

Aman Chokshi said he was walking along the coast of Neill Island, India, last month, when he noticed a faint bright patch along the horizon. He wrote:

I’ve always believed that the Large Magellanic Cloud was only visible from the Southern Hemisphere. My sky map showed that the Large Magellanic Cloud was barely 10 degrees above the horizon, below the bright star Canopus. I immediately set up my camera, and took a long exposure to see if I could capture it.

The sky was lit with brilliant airglow, within which a bright density of stars. So thrilled to have shot this!

By the way, Aman also said:

I shot this using an old Canon film lens, 50mm f/1.4 stopped down to f/4. The sky is a stack of 90x8s images, while the foreground is a stack of 3x30s images. I manually aligned the reflected stars in the tide pools, in Photoshop.

Thank you, Aman!

Read more: The spectacular Large Magellanic Cloud

Neill Island, in the Indian Ocean. Map via Wikipedia.

Bottom line: Large Magellanic Cloud, captured from Neill Island, India.

from EarthSky https://ift.tt/2WtlhUi

Machine learning used to understand and predict dynamics of worm behavior

The roundworm C. elegans is a well-established laboratory model system. While the worm is a fairly simple living system, it is complicated enough to serve as "a kind of sandbox" for testing out methods of automated inference, says Emory biophysicist Ilya Nemenman.

By Carol Clark

Biophysicists have used an automated method to model a living system — the dynamics of a worm perceiving and escaping pain. The Proceedings of the National Academy of Sciences (PNAS) published the results, which worked with data from experiments on the C. elegans roundworm.

“Our method is one of the first to use machine-learning tools on experimental data to derive simple, interpretable equations of motion for a living system,” says Ilya Nemenman, senior author of the paper and a professor of physics and biology at Emory University. “We now have proof of principle that it can be done. The next step is to see if we can apply our method to a more complicated system.”

The model makes accurate predictions about the dynamics of the worm behavior, and these predictions are biologically interpretable and have been experimentally verified.

Collaborators on the paper include first author Bryan Daniels, a theorist from Arizona State University, and co-author William Ryu, an experimentalist from the University of Toronto.

The researchers used an algorithm, developed in 2015 by Daniels and Nemenman, that teaches a computer how to efficiently search for the laws that underlie natural dynamical systems, including complex biological ones. They dubbed the algorithm “Sir Isaac,” after one of the most famous scientists of all time — Sir Isaac Newton. Their long-term goal is to develop the algorithm into a “robot scientist,” to automate and speed up the scientific method of forming quantitative hypotheses, then testing them by looking at data and experiments.

While Newton’s Three Laws of Motion can be used to predict dynamics for mechanical systems, the biophysicists want to develop similar predictive dynamical approaches that can be applied to living systems.

For the PNAS paper, they focused on the decision-making involved when C. elegans responds to a sensory stimulus. The data on C. elegans had been previously gathered by the Ryu lab, which develops methods to measure and analyze behavioral responses of the roundworm at the holistic level, from basic motor gestures to long-term behavioral programs.

C. elegans is a well-established laboratory animal model system. Most C. elegans have only 302 neurons, few muscles and a limited repertoire of motion. A sequence of experiments involved interrupting the forward movement of individual C. elegans with a laser strike to the head. When the laser strikes a worm, it withdraws, briefly accelerating backwards and eventually returning to forward motion, usually in a different direction. Individual worms respond differently. Some, for instance, immediately reverse direction upon laser stimulus, while others pause briefly before responding. Another variable in the experiments is the intensity of the laser: Worms respond faster to hotter and more rapidly rising temperatures.

For the PNAS paper, the researchers fed the Sir Isaac platform the motion data from the first few seconds of the experiments — before and shortly after the laser strikes a worm and it initially reacts. From this limited data, the algorithm was able to capture the average responses that matched the experimental results and also to predict the motion of the worm well beyond these initial few seconds, generalizing from the limited knowledge. The prediction left only 10 percent of the variability in the worm motion that can be attributed to the laser stimulus unexplained. This was twice as good as the best prior models, which were not aided by automated inference.

“Predicting a worm’s decision about when and how to move in response to a stimulus is a lot more complicated than just calculating how a ball will move when you kick it,” Nemenman says. “Our algorithm had to account for the complexities of sensory processing in the worms, the neural activity in response to the stimuli, followed by the activation of muscles and the forces that the activated muscles generate. It summed all this up into a simple and elegant mathematical description.”

The model derived by Sir Isaac was well-matched to the biology of C. elegans, providing interpretable results for both the sensory processing and the motor response, hinting at the potential of artificial intelligence to aid in discovery of accurate and interpretable models of more complex systems.

“It’s a big step from making predictions about the behavior of a worm to that of a human,” Nemenman says, “but we hope that the worm can serve as a kind of sandbox for testing out methods of automated inference, such that Sir Isaac might one day directly benefit human health. Much of science is about guessing the laws that govern natural systems and then verifying those guesses through experiments. If we can figure out how to use modern machine learning tools to help with the guessing, that could greatly speed up research breakthroughs.”

Related:
Biophysicists take small step in quest for 'robot scientist'
Physicists eye neural fly data, find formula for Zipf's law
Biology may not be so complex after all

from eScienceCommons https://ift.tt/2JLvqKA

The roundworm C. elegans is a well-established laboratory model system. While the worm is a fairly simple living system, it is complicated enough to serve as "a kind of sandbox" for testing out methods of automated inference, says Emory biophysicist Ilya Nemenman.

By Carol Clark

Biophysicists have used an automated method to model a living system — the dynamics of a worm perceiving and escaping pain. The Proceedings of the National Academy of Sciences (PNAS) published the results, which worked with data from experiments on the C. elegans roundworm.

“Our method is one of the first to use machine-learning tools on experimental data to derive simple, interpretable equations of motion for a living system,” says Ilya Nemenman, senior author of the paper and a professor of physics and biology at Emory University. “We now have proof of principle that it can be done. The next step is to see if we can apply our method to a more complicated system.”

The model makes accurate predictions about the dynamics of the worm behavior, and these predictions are biologically interpretable and have been experimentally verified.

Collaborators on the paper include first author Bryan Daniels, a theorist from Arizona State University, and co-author William Ryu, an experimentalist from the University of Toronto.

The researchers used an algorithm, developed in 2015 by Daniels and Nemenman, that teaches a computer how to efficiently search for the laws that underlie natural dynamical systems, including complex biological ones. They dubbed the algorithm “Sir Isaac,” after one of the most famous scientists of all time — Sir Isaac Newton. Their long-term goal is to develop the algorithm into a “robot scientist,” to automate and speed up the scientific method of forming quantitative hypotheses, then testing them by looking at data and experiments.

While Newton’s Three Laws of Motion can be used to predict dynamics for mechanical systems, the biophysicists want to develop similar predictive dynamical approaches that can be applied to living systems.

For the PNAS paper, they focused on the decision-making involved when C. elegans responds to a sensory stimulus. The data on C. elegans had been previously gathered by the Ryu lab, which develops methods to measure and analyze behavioral responses of the roundworm at the holistic level, from basic motor gestures to long-term behavioral programs.

C. elegans is a well-established laboratory animal model system. Most C. elegans have only 302 neurons, few muscles and a limited repertoire of motion. A sequence of experiments involved interrupting the forward movement of individual C. elegans with a laser strike to the head. When the laser strikes a worm, it withdraws, briefly accelerating backwards and eventually returning to forward motion, usually in a different direction. Individual worms respond differently. Some, for instance, immediately reverse direction upon laser stimulus, while others pause briefly before responding. Another variable in the experiments is the intensity of the laser: Worms respond faster to hotter and more rapidly rising temperatures.

For the PNAS paper, the researchers fed the Sir Isaac platform the motion data from the first few seconds of the experiments — before and shortly after the laser strikes a worm and it initially reacts. From this limited data, the algorithm was able to capture the average responses that matched the experimental results and also to predict the motion of the worm well beyond these initial few seconds, generalizing from the limited knowledge. The prediction left only 10 percent of the variability in the worm motion that can be attributed to the laser stimulus unexplained. This was twice as good as the best prior models, which were not aided by automated inference.

“Predicting a worm’s decision about when and how to move in response to a stimulus is a lot more complicated than just calculating how a ball will move when you kick it,” Nemenman says. “Our algorithm had to account for the complexities of sensory processing in the worms, the neural activity in response to the stimuli, followed by the activation of muscles and the forces that the activated muscles generate. It summed all this up into a simple and elegant mathematical description.”

The model derived by Sir Isaac was well-matched to the biology of C. elegans, providing interpretable results for both the sensory processing and the motor response, hinting at the potential of artificial intelligence to aid in discovery of accurate and interpretable models of more complex systems.

“It’s a big step from making predictions about the behavior of a worm to that of a human,” Nemenman says, “but we hope that the worm can serve as a kind of sandbox for testing out methods of automated inference, such that Sir Isaac might one day directly benefit human health. Much of science is about guessing the laws that govern natural systems and then verifying those guesses through experiments. If we can figure out how to use modern machine learning tools to help with the guessing, that could greatly speed up research breakthroughs.”

Related:
Biophysicists take small step in quest for 'robot scientist'
Physicists eye neural fly data, find formula for Zipf's law
Biology may not be so complex after all

from eScienceCommons https://ift.tt/2JLvqKA

What happened before the Big Bang?

Artist’s concept showing the patterns of signals generated by primordial standard clocks in different theories of the primordial universe. Top: Big Bounce. Bottom: Inflation. Image via CfA.

Can we get an inkling of what existed before our universe began? Some theories suggest that, before the Big Bang, whatever existed was contracting, rather than expanding, as our universe is today. Perhaps what was contracting was an earlier universe, for example. If so, what we perceive as a Big Bang was actually a part of a Big Bounce. But a popular theory of our universe, called the inflation theory, doesn’t call for the idea of a previously contracting universe.

So what if inflation theory could be proven false? If so, the door would open to other theories, some of which do suggest a state of contraction before our universe began. If inflation theory could be proven false, we’d have some potential to probe – via these other theories – the universe before the Big Bang.

Now a team of scientists at the Harvard-Smithsonian Center for Astrophysics (CfA) has laid out a method that might be used to falsify inflation experimentally. The study will appear in the physics journal Physical Review Letters as an Editors’ Suggestion.

Let’s start from the beginning here … literally. Inflation is the theory that speaks of a time immediately after the Big Bang. It describes a universe that dramatically expanded in size for a fleeting fraction of a second. Inflation theory solves some important mysteries about the structure and evolution of our universe. But, according to the CfA scientists, other very different theories – including those that do allow for a previously contracting universe and a Big Bounce – can also explain these mysteries. These scientists said in a statement:

To help decide between inflation and these other ideas, the issue of falsifiability – that is, whether a theory can be tested to potentially show it is false – has inevitably arisen.

Some researchers, including Avi Loeb of CfA – who is a part of the new study – had previously raised concerns about inflation, on the grounds that it was difficult, if not impossible, to falsify. Loeb said:

Falsifiability should be a hallmark of any scientific theory. The current situation for inflation is that it’s such a flexible idea, it cannot be falsified experimentally. No matter what value people measure for some observable attribute, there are always some models of inflation that can explain it.

A team of scientists led by the CfA’s Xingang Chen, along with Loeb, and Zhong-Zhi Xianyu of the Physics Department of Harvard University, have applied an idea they call a primordial standard clock to the non-inflationary theories, and laid out a method that may be used to falsify inflation experimentally.

In an effort to find some characteristic that can separate inflation from other theories, the team began by identifying the defining property of the various theories – the evolution of the size of the primordial universe. Xianyu said:

For example, during inflation, the size of the universe grows exponentially. In some alternative theories, the size of the universe contracts. Some do it very slowly, while others do it very fast.

The attributes people have proposed so far to measure usually have trouble distinguishing between the different theories because they are not directly related to the evolution of the size of the primordial universe.

So, we wanted to find what the observable attributes are that can be directly linked to that defining property.

According to these scientists, the signals generated by the primordial standard clock can serve such a purpose. They explained:

That clock is any type of heavy elementary particle in the primordial universe. Such particles should exist in any theory and their positions should oscillate at some regular frequency, much like the ticking of a clock’s pendulum.

The primordial universe was not entirely uniform. There were tiny irregularities in density on minuscule scales that became the seeds of the large-scale structure observed in today’s universe. This is the primary source of information physicists rely on to learn about what happened before the Big Bang.

The ticks of the standard clock generated signals that were imprinted into the structure of those irregularities. Standard clocks in different theories of the primordial universe predict different patterns of signals, because the evolutionary histories of the universe are different.

Chen said:

If we imagine all of the information we learned so far about what happened before the Big Bang is in a roll of film frames, then the standard clock tells us how these frames should be played. Without any clock information, we don’t know if the film should be played forward or backward, fast or slow, just like we are not sure if the primordial universe was inflating or contracting, and how fast it did so. This is where the problem lies. The standard clock put time stamps on each of these frames when the film was shot before the Big Bang, and tells us how to play the film.

The team calculated how these standard clock signals should look in non-inflationary theories, and suggested how they should be searched for in astrophysical observations. Co-author Xianyu said:

If a pattern of signals representing a contracting universe were found, it would falsify the entire inflationary theory.

Chen added that the success of this idea lies with experimentation. He said:

These signals will be very subtle to detect, and so we may have to search in many different places. The cosmic microwave background radiation is one such place, and the distribution of galaxies is another. We have already started to search for these signals and there are some interesting candidates already …

As always, they said, more observational data is needed to bear out these theoretical ideas.

Bottom line: We don’t know what happened before the Big Bang, but some cosmological theories suggest a contraction prior to it. Perhaps an earlier universe was contracting. Unfortunately, the most popular cosmological theory of today – inflation theory – doesn’t call for this idea. Now scientists at CfA have devised a way that inflation theory might be falsified. If it were falsified, the door would be open to some of the other theories that hint at a pre-Big-Bang contraction.

Source: Unique Fingerprints of Alternatives to Inflation in the Primordial Power Spectrum

A related previous work: Quantum Primordial Standard Clocks

Via CfA

from EarthSky https://ift.tt/2FCmtz5

Artist’s concept showing the patterns of signals generated by primordial standard clocks in different theories of the primordial universe. Top: Big Bounce. Bottom: Inflation. Image via CfA.

Can we get an inkling of what existed before our universe began? Some theories suggest that, before the Big Bang, whatever existed was contracting, rather than expanding, as our universe is today. Perhaps what was contracting was an earlier universe, for example. If so, what we perceive as a Big Bang was actually a part of a Big Bounce. But a popular theory of our universe, called the inflation theory, doesn’t call for the idea of a previously contracting universe.

So what if inflation theory could be proven false? If so, the door would open to other theories, some of which do suggest a state of contraction before our universe began. If inflation theory could be proven false, we’d have some potential to probe – via these other theories – the universe before the Big Bang.

Now a team of scientists at the Harvard-Smithsonian Center for Astrophysics (CfA) has laid out a method that might be used to falsify inflation experimentally. The study will appear in the physics journal Physical Review Letters as an Editors’ Suggestion.

Let’s start from the beginning here … literally. Inflation is the theory that speaks of a time immediately after the Big Bang. It describes a universe that dramatically expanded in size for a fleeting fraction of a second. Inflation theory solves some important mysteries about the structure and evolution of our universe. But, according to the CfA scientists, other very different theories – including those that do allow for a previously contracting universe and a Big Bounce – can also explain these mysteries. These scientists said in a statement:

To help decide between inflation and these other ideas, the issue of falsifiability – that is, whether a theory can be tested to potentially show it is false – has inevitably arisen.

Some researchers, including Avi Loeb of CfA – who is a part of the new study – had previously raised concerns about inflation, on the grounds that it was difficult, if not impossible, to falsify. Loeb said:

Falsifiability should be a hallmark of any scientific theory. The current situation for inflation is that it’s such a flexible idea, it cannot be falsified experimentally. No matter what value people measure for some observable attribute, there are always some models of inflation that can explain it.

A team of scientists led by the CfA’s Xingang Chen, along with Loeb, and Zhong-Zhi Xianyu of the Physics Department of Harvard University, have applied an idea they call a primordial standard clock to the non-inflationary theories, and laid out a method that may be used to falsify inflation experimentally.

In an effort to find some characteristic that can separate inflation from other theories, the team began by identifying the defining property of the various theories – the evolution of the size of the primordial universe. Xianyu said:

For example, during inflation, the size of the universe grows exponentially. In some alternative theories, the size of the universe contracts. Some do it very slowly, while others do it very fast.

The attributes people have proposed so far to measure usually have trouble distinguishing between the different theories because they are not directly related to the evolution of the size of the primordial universe.

So, we wanted to find what the observable attributes are that can be directly linked to that defining property.

According to these scientists, the signals generated by the primordial standard clock can serve such a purpose. They explained:

That clock is any type of heavy elementary particle in the primordial universe. Such particles should exist in any theory and their positions should oscillate at some regular frequency, much like the ticking of a clock’s pendulum.

The primordial universe was not entirely uniform. There were tiny irregularities in density on minuscule scales that became the seeds of the large-scale structure observed in today’s universe. This is the primary source of information physicists rely on to learn about what happened before the Big Bang.

The ticks of the standard clock generated signals that were imprinted into the structure of those irregularities. Standard clocks in different theories of the primordial universe predict different patterns of signals, because the evolutionary histories of the universe are different.

Chen said:

If we imagine all of the information we learned so far about what happened before the Big Bang is in a roll of film frames, then the standard clock tells us how these frames should be played. Without any clock information, we don’t know if the film should be played forward or backward, fast or slow, just like we are not sure if the primordial universe was inflating or contracting, and how fast it did so. This is where the problem lies. The standard clock put time stamps on each of these frames when the film was shot before the Big Bang, and tells us how to play the film.

The team calculated how these standard clock signals should look in non-inflationary theories, and suggested how they should be searched for in astrophysical observations. Co-author Xianyu said:

If a pattern of signals representing a contracting universe were found, it would falsify the entire inflationary theory.

Chen added that the success of this idea lies with experimentation. He said:

These signals will be very subtle to detect, and so we may have to search in many different places. The cosmic microwave background radiation is one such place, and the distribution of galaxies is another. We have already started to search for these signals and there are some interesting candidates already …

As always, they said, more observational data is needed to bear out these theoretical ideas.

Bottom line: We don’t know what happened before the Big Bang, but some cosmological theories suggest a contraction prior to it. Perhaps an earlier universe was contracting. Unfortunately, the most popular cosmological theory of today – inflation theory – doesn’t call for this idea. Now scientists at CfA have devised a way that inflation theory might be falsified. If it were falsified, the door would be open to some of the other theories that hint at a pre-Big-Bang contraction.

Source: Unique Fingerprints of Alternatives to Inflation in the Primordial Power Spectrum

A related previous work: Quantum Primordial Standard Clocks

Via CfA

from EarthSky https://ift.tt/2FCmtz5

Jupiter’s 700,000-year journey toward the sun

Artist’s concept of Jupiter’s Trojan asteroids. A group moves in front of the gas giant and a group follows behind. Image via NASA/JPL-Caltech.

According to new research from Lund University in Sweden, the planet Jupiter formed four times farther from the sun than its current orbit. Its migration inward through the solar system to its current orbit took only 700,000 years. The new study was published February 12, 2019, in the journal Astronomy and Astrophysics. The evidence for Jupiter’s journey comes from in an analysis of asteroids that move in the same orbit as Jupiter, in front of and behind the planet.

Astronomers know that gas giants planets around other stars are often very close to their star. According to current theory, these gas planets formed far away and later migrated inward toward their stars. Could that have happened in our own solar system?

For the new study, a team of researchers used computer calculations to trace Jupiter’s history in our solar system starting 4.5 billion years ago. Jupiter was then newly formed, as were the other planets in the solar system. The planets were gradually built up by the cosmic dust, which revolved around our young sun in a flat disk of gas and dust. At that time, said the study, Jupiter was no bigger than our own planet and about four times farther away from the sun than its current position.

Astronomer Simona Pirani of Lund University is the study’s lead author. She said in a statement:

This is the first time we have evidence that Jupiter was formed far from the sun and then migrated to its current path.

The study also made calculations on the gas giant Saturn and the ice giant planets Uranus and Neptune. The researchers think that even these giant planets must have migrated in the same way as Jupiter. Pirani said:

The evidence for the migration can be found in the Trojan asteroids that revolve around the sun near Jupiter.

The Trojans are a large group of asteroids that share Jupiter’s orbit around the sun. They consist of two groups of thousands of asteroids that lie in front of and behind Jupiter, respectively. There are about 50 percent more Trojans in front of Jupiter than behind, and this asymmetry turned out to be key for scientists in understanding Jupiter’s migration.

This time-lapsed animation shows the movements of the inner planets (Mercury, brown; Venus, white; Earth, blue; Mars, red; Jupiter, orange), and the two Trojan swarms (green). Image via Astronomical Institute of CAS/Petr Scheirich/NASA.

The research world has so far been unable to explain why the two asteroid groups are different in size. Anders Johansen, Professor of Astronomy at Lund University, is a study co-author. Johansen said:

This asymmetry has been a mystery in the solar system.

The new study investigated the asymmetry by recreating the sequence of events in Jupiter’s formation and the planet’s gradual capture of its Trojan asteroids. Using computer simulations, the researchers calculated that the current asymmetry could only have occurred if Jupiter was formed four times farther away in the solar system and then migrated to its present location. During the journey to the sun, Jupiter’s own gravity captured more Trojans in front of it than behind it.

According to the researchers’ calculations, Jupiter’s migration took around 700,000 years, starting about 2 to 3 million years after Jupiter began its life as asteroid far from the sun. The journey inward into the solar system took place in a spiral-shaped movement, say the researchers, where Jupiter continued to circle around the sun but in an increasingly narrow path. The underlying reason for the migration itself has to do with gravity forces from the surrounding gas in the solar system.

The computer simulations show that the Trojan asteroids were captured when Jupiter was a young planet without a gas body, which means that these asteroids most likely consist of similar building blocks to the ones that formed Jupiter’s interior.

Bottom line: A new study traces Jupiter’s journey inward though the solar system to its current orbit.

Source: The consequences of planetary migration on the minor bodies of the early Solar System

Via Lund University

from EarthSky https://ift.tt/2FDR2Va

Artist’s concept of Jupiter’s Trojan asteroids. A group moves in front of the gas giant and a group follows behind. Image via NASA/JPL-Caltech.

According to new research from Lund University in Sweden, the planet Jupiter formed four times farther from the sun than its current orbit. Its migration inward through the solar system to its current orbit took only 700,000 years. The new study was published February 12, 2019, in the journal Astronomy and Astrophysics. The evidence for Jupiter’s journey comes from in an analysis of asteroids that move in the same orbit as Jupiter, in front of and behind the planet.

Astronomers know that gas giants planets around other stars are often very close to their star. According to current theory, these gas planets formed far away and later migrated inward toward their stars. Could that have happened in our own solar system?

For the new study, a team of researchers used computer calculations to trace Jupiter’s history in our solar system starting 4.5 billion years ago. Jupiter was then newly formed, as were the other planets in the solar system. The planets were gradually built up by the cosmic dust, which revolved around our young sun in a flat disk of gas and dust. At that time, said the study, Jupiter was no bigger than our own planet and about four times farther away from the sun than its current position.

Astronomer Simona Pirani of Lund University is the study’s lead author. She said in a statement:

This is the first time we have evidence that Jupiter was formed far from the sun and then migrated to its current path.

The study also made calculations on the gas giant Saturn and the ice giant planets Uranus and Neptune. The researchers think that even these giant planets must have migrated in the same way as Jupiter. Pirani said:

The evidence for the migration can be found in the Trojan asteroids that revolve around the sun near Jupiter.

The Trojans are a large group of asteroids that share Jupiter’s orbit around the sun. They consist of two groups of thousands of asteroids that lie in front of and behind Jupiter, respectively. There are about 50 percent more Trojans in front of Jupiter than behind, and this asymmetry turned out to be key for scientists in understanding Jupiter’s migration.

This time-lapsed animation shows the movements of the inner planets (Mercury, brown; Venus, white; Earth, blue; Mars, red; Jupiter, orange), and the two Trojan swarms (green). Image via Astronomical Institute of CAS/Petr Scheirich/NASA.

The research world has so far been unable to explain why the two asteroid groups are different in size. Anders Johansen, Professor of Astronomy at Lund University, is a study co-author. Johansen said:

This asymmetry has been a mystery in the solar system.

The new study investigated the asymmetry by recreating the sequence of events in Jupiter’s formation and the planet’s gradual capture of its Trojan asteroids. Using computer simulations, the researchers calculated that the current asymmetry could only have occurred if Jupiter was formed four times farther away in the solar system and then migrated to its present location. During the journey to the sun, Jupiter’s own gravity captured more Trojans in front of it than behind it.

According to the researchers’ calculations, Jupiter’s migration took around 700,000 years, starting about 2 to 3 million years after Jupiter began its life as asteroid far from the sun. The journey inward into the solar system took place in a spiral-shaped movement, say the researchers, where Jupiter continued to circle around the sun but in an increasingly narrow path. The underlying reason for the migration itself has to do with gravity forces from the surrounding gas in the solar system.

The computer simulations show that the Trojan asteroids were captured when Jupiter was a young planet without a gas body, which means that these asteroids most likely consist of similar building blocks to the ones that formed Jupiter’s interior.

Bottom line: A new study traces Jupiter’s journey inward though the solar system to its current orbit.

Source: The consequences of planetary migration on the minor bodies of the early Solar System

Via Lund University

from EarthSky https://ift.tt/2FDR2Va

SOHO looks at equinox sun

Image via ESA/NASA, SOHO.

Where were you a week ago on the March equinox (March 20, 2019)? The SOHO solar observatory was some 900,000 miles (1.5 million km) from Earth, orbiting the first Lagrange point (L1), monitoring the sun.

The above montage of images shows what SOHO saw early on equinox morning. The four images show the sun at different ultraviolet wavelengths. From left to right, the images shown in this view were taken at increasing wavelengths (171 Å, 195 Å, 284 Å and 304 Å, respectively) with SOHO’s Extreme ultraviolet Imaging Telescope, which currently takes snapshots of the sun twice a day.

Each wavelength channel is sensitive to solar material at a different range of temperatures, peering at different heights into the sun’s atmosphere. From left to right, the brightest material in each image corresponds to temperatures of 1 million, 1.5 million, 2 million and 60,000–80,000 degrees C, respectively.

Bottom line: Four images of the sun by the SOHO solar observatory taken on the March 2019 equinox.

Via ESA

from EarthSky https://ift.tt/2JJmkya

Image via ESA/NASA, SOHO.

Where were you a week ago on the March equinox (March 20, 2019)? The SOHO solar observatory was some 900,000 miles (1.5 million km) from Earth, orbiting the first Lagrange point (L1), monitoring the sun.

The above montage of images shows what SOHO saw early on equinox morning. The four images show the sun at different ultraviolet wavelengths. From left to right, the images shown in this view were taken at increasing wavelengths (171 Å, 195 Å, 284 Å and 304 Å, respectively) with SOHO’s Extreme ultraviolet Imaging Telescope, which currently takes snapshots of the sun twice a day.

Each wavelength channel is sensitive to solar material at a different range of temperatures, peering at different heights into the sun’s atmosphere. From left to right, the brightest material in each image corresponds to temperatures of 1 million, 1.5 million, 2 million and 60,000–80,000 degrees C, respectively.

Bottom line: Four images of the sun by the SOHO solar observatory taken on the March 2019 equinox.

Via ESA

from EarthSky https://ift.tt/2JJmkya