Scientists often field check their findings, heading outside to see if computer models match with what is happening in the real world. But doing so is challenging when the field is 2 1/2 miles (4,000 m) up. Enter a new field assistant: the great frigatebird.

Great frigatebirds live in tropical regions and routinely fly to 1.25 miles (2,000 meters) in altitude. Occasionally they even reach heights of 2.5 miles (4,000 meters). A new study shows that great frigatebirds equipped with tiny sensors can give detailed information about the planetary boundary layer. The planetary boundary layer is the dynamic atmospheric layer closest to Earth. It’s where we experience weather, air quality and climate impacts. Scientists presented the new research at the AGU Annual Meeting on Wednesday, December 13, 2023, in San Francisco and online.

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Investigating the planetary boundary layer

The planetary boundary layer connects the atmosphere with the surface ocean, land and ice. It rises and falls throughout the day. Ian Brosnan, a marine scientist at NASA’s Ames Research Center who led the work, said:

Many weather and climate processes are related to that fluctuation. So understanding planetary boundary layer dynamics is fundamental to answering a lot of questions about the Earth system.

Current techniques typically rely on ground-based measurements or remote sensing, but for far-flung regions over the oceans, Brosnan said:

… getting in situ samples of any sort at scale is a challenge.

Enter the great frigatebirds

Brosnan’s co-author, NASA ecologist Morgan Gilmour, previously used sensor-laden great frigatebirds to assess whether the boundaries of a marine protected area around Palmyra Atoll in the Pacific Ocean protected the animals within it. Brosnan suspected the frigatebirds’ flights were related to the planetary boundary layer. If so, Gilmore’s project had also collected critical planetary boundary layer samples. Brosnan said:

I instantly thought the birds could be traveling to the top of the planetary boundary layer, turning around, and coming back down. And they’re probably covering a pretty broad area, too.

To check if the birds’ flight patterns matched planetary boundary layer altitudes, they compared planetary boundary layer measurements from 2006-2019 analysis to frigatebirds’ flights. They found that the long-term average planetary boundary layer heights in that area very closely matched the bird’s altitude data. Brosnan’s hunch was right.

The tagged frigatebirds had sampled temperature profiles in the planetary boundary layer and had no trouble collecting data during cloudy weather or at night, unlike traditional sampling approaches. Brosnan said:

These novel approaches to using animal tracking data can help NASA measure the planetary boundary layer and improve climate predictions and weather and air quality forecasts.

Internet of Animals

Brosnan mentioned that after hearing from interagency scientists about how important global, satellite-based animal tracking data was for their research projects, NASA created the Internet of Animals project. This allows scientists to integrate data from remote sensing measurements with data from sensors on animals, now including the great frigatebird planetary boundary layer data.

Brosnan said their work is a good example of how interagency and interdisciplinary collaborations can help tackle larger science questions:

One of the things we’re trying to do is bridge between these two communities – animal tracking and atmospheric science – and see if we can enrich the work that we both do.

Bottom line: A new study from NASA’s ‘Internet of Animals’ project shows that high-flying great frigatebirds can provide detailed sampling of the atmospheric layer located closest to Earth, where weather and climate directly impact us.

Source: A31M-2550 Can tagged great frigatebirds (Fregata minor) be used to track the dynamics of the planetary boundary layer height?

Via AGU

Read more: Animals on the brain? There’s a scientific reason

The post Birds with backpacks to help study Earth’s atmosphere first appeared on EarthSky.

Reprinted from a December 12, 2023, statement from the SETI Institute. Edits by EarthSky. Video by EarthSky.

SETI team ‘converses’ with a humpback whale

SETI stands for the Search for Extraterrestrial Intelligence. On December 12, 2023, a team of scientists from the SETI Institute, University of California Davis and the Alaska Whale Foundation, said they had a close encounter with a non-human (aquatic) intelligence. The Whale-SETI team has been studying humpback whale communication systems in an effort to develop what SETI researchers call “intelligence filters” in the search for extraterrestrial intelligence.

In response to a recorded humpback ‘contact’ call played into the sea via an underwater speaker, a humpback whale named Twain approached and circled the team’s boat, while responding in a conversational style to the whale ‘greeting signal.’

As a matter of fact, during the 20-minute exchange, Twain responded to each playback call and matched the interval variations between each signal.

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A description and analysis of the encounter appears in the November 29, 2023, issue of the journal Peer J, titled: “Interactive Bioacoustic Playback as a Tool for Detecting and Exploring Nonhuman Intelligence: Conversing with an Alaskan Humpback Whale.”

According to the lead author Brenda McCowan of U.C. Davis:

We believe this is the first such communicative exchange between humans and humpback whales in the humpback language.

Coauthor Fred Sharpe of the Alaska Whale Foundation said:

Humpback whales are extremely intelligent, have complex social systems, make tools – nets out of bubbles to catch fish – and communicate extensively with both songs and social calls.

Communicating with non-human intelligence

Similar to studying Antarctica as a proxy for Mars, the Whale-SETI team is studying intelligent, terrestrial, non-human communication systems to develop filters to apply to any extraterrestrial signals received. With this in mind, the mathematics of information theory to quantify communicative complexity – for example rule structure embedded in a received message – will be utilized.

According to Laurance Doyle, a coauthor on the paper, of the SETI Institute:

Because of current limitations on technology, an important assumption of the search for extraterrestrial intelligence is that extraterrestrials will be interested in making contact and so target human receivers. This important assumption is certainly supported by the behavior of humpback whales.

Bottom line: SETI researchers are studying how humpback whales communicate. This may eventually help us communicate with non-human intelligence of an alien civilization.

Source: Interactive Bioacoustic Playback as a Tool for Detecting and Exploring Nonhuman Intelligence: Conversing with an Alaskan Humpback Whale

Via SETI

Read more: SETI looks to Milky Way’s heart for alien signals

The post Will humpback whales train us to communicate with aliens? first appeared on EarthSky.

Earliest sunset isn’t on the shortest day

Have you noticed your sunsets coming later now? That’s true for many of us, even though the December solstice is still more than a week away. For the mid-northern U.S. and similar latitudes – around 40 degrees north latitude – the earliest sunsets of the year came around December 8. That would be the latitude of New York City; Philadelphia, Pennsylvania; Kansas City, Missouri; Denver, Colorado; Reno, Nevada; Beijing, China; Madrid, Spain; and Naples, Italy.

For more southerly latitudes – say around 30 degrees north latitude – the earliest sunsets of the year came in late November and early December.

And what about the Southern Hemisphere? At this same time, the year’s earliest sunrises have happened or are happening, as you progress toward your longest day at the December solstice.

Then, closer to the Arctic and Antarctic Circles, the earliest sunset and earliest sunrise happen nearer the solstice.

Want to know the date of your earliest sunset (or sunrise)? Sunrise-sunset.org provides the sunrise/sunset times to the second for locations around the globe.

The exact date of the Northern Hemisphere’s earliest sunset and the Southern Hemisphere’s earliest sunrise varies by latitude.

But at temperate latitudes, both of these annual hallmarks in our sky come a few to several weeks before the December solstice, not at the solstice as you might expect.

Available now! 2024 EarthSky lunar calendar. A unique and beautiful poster-sized calendar showing phases of the moon every night of the year! And it makes a great gift.

Why?

The next solstice in 2023 comes at 3:27 UTC on December 22 and marks an unofficial beginning for winter in the Northern Hemisphere. So for the Northern Hemisphere, this upcoming solstice brings the shortest day and longest night of the year. Then why isn’t the earliest sunset on the year’s shortest day?

Basically, it’s because of the discrepancy between the clock and the sun. A clock ticks off exactly 24 hours from one noon to the next. But an actual day – as measured by the spin of the Earth, from what is called one solar noon to the next – rarely equals 24 hours exactly.

Also, solar noon is simply called midday, because it refers to that instant when the sun reaches its highest point for the day. Thus, in the month of December, the time period from one solar noon to the next is actually half a minute longer than 24 hours. For example, in Philadelphia, Pennsylvania on December 7 the sun reaches its noontime position at 11:52 a.m. local standard time. Then, two weeks later – on the winter solstice – the sun will reach its noontime position around 11:58 a.m. So that’s six minutes later than on December 7.

Visit Sunrise Sunset Calendars to know the clock time for sunrise, solar noon and sunset plus day length in your part of the world, remembering to check the solar noon and day length boxes.

Another key point is that the later clock time for solar noon means a later clock time for sunrise and sunset. This can be seen in the table below.

For Philadelphia, Pennsylvania

Latest sunrise and earliest sunset aren’t on the solstice

As you might have guessed, the latest sunrises aren’t on the day of the solstice either. For middle latitudes in the Northern Hemisphere, the latest sunrises come in early January.

Although there’s variation in the exact dates, the sequence is always the same for both hemispheres. First, earliest sunset before the winter solstice, the winter solstice itself, latest sunrise after the winter solstice. Then, half a year later, earliest sunrise before the summer solstice, the summer solstice itself, latest sunset.

So by all means, check out the earliest and latest sunsets and sunrises in your area. They are always lovely and happen around every solstice.

Sunsets from the EarthSky Community

Bottom line: The solstice comes on December 22, 2023, at 3:27 UTC. Does that coincide with the earliest sunsets? It depends on where you live. The earliest sunsets at mid-northern latitudes happen weeks before the solstice. By comparison, latitudes closer to the equator have their earliest sunsets in late November, or earlier in December. And then latitudes closer to the Arctic Circle will have their earliest sunsets closer to the December solstice.

Solstice tale of two cities: New York, New York, and St. Augustine, Florida

EarthSky’s monthly night sky guide: Visible planets and more

The post The earliest sunset comes before the winter solstice first appeared on EarthSky.

Indranil Banik, University of St Andrews

One of the biggest mysteries in cosmology is the rate at which the universe is expanding. Scientists can predict this using the standard model of cosmology, also known as Lambda-cold dark matter. This model is based on detailed observations of the light left over from the Big Bang, the so-called cosmic microwave background.

The universe’s expansion makes galaxies move away from each other. The further away they are from us, the more quickly they move. The relationship between a galaxy’s speed and distance is governed by Hubble’s constant, which is about 43 miles (70 km) per second per megaparsec (a unit of length in astronomy). This means that a galaxy gains about 50,000 miles per hour for every million light-years it is away from us.

But unfortunately for the standard model, there’s a dispute over the value, leading to what scientists call the Hubble tension. When we measure the expansion rate using nearby galaxies and supernovas, it is 10% larger than when we predict it based on the cosmic microwave background.

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Do we live in a giant void?

In our new paper, we present one possible explanation: that we live in a giant void in space (an area with below average density). We show that this could inflate local measurements through outflows of matter from the void. Outflows would arise when denser regions surrounding a void pull it apart. They’d exert a bigger gravitational pull than the lower density matter inside the giant void.

In this scenario, we would need to be near the center of a void about a billion light-years in radius and with density about 20% below the average for the universe as a whole. So, not completely empty.

Such a large and deep void is unexpected in the standard model … and therefore controversial. The cosmic microwave background gives a snapshot of structure in the infant universe, suggesting that matter today should be rather uniformly spread out. However, directly counting the number of galaxies in different regions does indeed suggest we are in a local void.

Tweaking the laws of gravity

We wanted to test this idea further by matching many different cosmological observations by assuming that we live in a large void that grew from a small density fluctuation at early times.

To do this, our model didn’t incorporate Lambda-cold dark matter. Instead, it incorporated an alternative theory called Modified Newtonian Dynamics (MOND).

Theorists originally proposed MOND to explain anomalies in the rotation speeds of galaxies. These anomalies are what led to the suggestion of an invisible substance called dark matter. MOND instead suggests that the anomalies can be explained by Newton’s law of gravity breaking down when the gravitational pull is very weak, as is the case in the outer regions of galaxies.

The overall cosmic expansion history in MOND would be similar to the standard model. However, structure (such as galaxy clusters) would grow faster in MOND. Our model captures what the local universe might look like in a MOND universe. And we found it would allow local measurements of the expansion rate today to fluctuate depending on our location.

Bulk flow

Recent galaxy observations have allowed a crucial new test of our model based on the velocity it predicts at different locations. Scientists can do this by measuring something called the bulk flow. The bulk flow is the average velocity of matter in a given sphere, dense or not. This varies with the radius of the sphere, with recent observations showing it continues out to a billion light years.

Interestingly, the bulk flow of galaxies on this scale has quadruple the speed expected in the standard model. It also seems to increase with the size of the region considered, opposite to what the standard model predicts. The likelihood of this being consistent with the standard model is below one in a million.

This prompted us to see what our study predicted for the bulk flow. We found it yields a quite good match to the observations. That requires that we are fairly close to the void center, and the void being most empty at its center.

Case closed?

Our results come at a time when popular solutions to the Hubble tension are in trouble. Some believe we just need more precise measurements. Others think it can be solved by assuming the high expansion rate we measure locally is actually the correct one. But that requires a slight tweak to the expansion history in the early universe so the cosmic microwave background still looks right.

Unfortunately, an influential review highlights seven problems with this approach. If the universe expanded 10% faster over the vast majority of cosmic history, it would also be about 10% younger. And that contradicts the ages of the oldest stars.

The existence of a deep and extended local void in the galaxy number counts and the fast observed bulk flows strongly suggest that structure grows faster than expected in Lambda-cold dark matter on scales of tens to hundreds of millions of light-years.

If we live in a giant void, do conflicting observations resolve?

Interestingly, we know that the massive galaxy cluster El Gordo formed too early in cosmic history. Also, it has too high a mass and collision speed to be compatible with the standard model. This is yet more evidence that structure forms too slowly in this model.

Since gravity is the dominant force on such large scales, we most likely need to extend Einstein’s theory of gravity, general relativity. But only on scales larger than a million light-years.

However, we have no good way to measure how gravity behaves on much larger scales. There are no gravitationally bound objects that huge. We can assume general relativity remains valid and compare with observations. But it is precisely this approach that leads to the very severe tensions currently faced by our best model of cosmology.

Einstein supposedly said that we cannot solve problems with the same thinking that led to the problems in the first place. Even if the required changes are not drastic, we could well be witnessing the first reliable evidence for more than a century that we need to change our theory of gravity.

Indranil Banik, Postdoctoral Research Fellow in Astrophysics, University of St Andrews

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: Scientists think we could live in a giant void, a bubble of less-dense matter leftover from the Big Bang. If so, it could explain the expansion rate of the universe that we see.

The post Could a giant void explain the universe’s expansion? first appeared on EarthSky.

The University College London published this article on December 4, 2023. Reprinted here with permission. Edits by EarthSky.

Einstein’s gravity and quantum mechanics

Modern physics is founded upon two pillars. One is quantum theory, which governs the smallest particles in the universe. The other is Einstein’s theory of general relativity, which explains gravity through the bending of spacetime. But these two theories are in contradiction with each other, and a reconciliation has remained elusive for over a century.

The prevailing assumption has been to modify Einstein’s theory of gravity, or “quantized” to fit within quantum theory. This is the approach of two leading candidates for a quantum theory of gravity, string theory and loop quantum gravity.

But Jonathan Oppenheim at University College London Physics & Astronomy has developed a new theory. In a new paper in the peer-reviewed open-access journal Physical Review X (PRX), he challenges that consensus and takes an alternative approach by suggesting that spacetime may be classical. That is, not governed by quantum theory at all.

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Here’s how Einstein’s gravity and quantum mechanics works

Instead of modifying spacetime, the theory – dubbed a “postquantum theory of classical gravity” – modifies quantum theory. It predicts an intrinsic breakdown in predictability that is mediated by spacetime itself. This results in random and violent fluctuations in spacetime that are larger than envisaged under quantum theory, rendering the apparent weight of objects unpredictable if measured precisely enough.

A second paper, published simultaneously in the peer-reviewed, open-access journal Nature Communications and led by Oppenheim’s former Ph.D. students, looks at some of the consequences of the theory. It also proposes an experiment to test it: to measure a mass very precisely to see if its weight appears to fluctuate over time.

For example, the International Bureau of Weights and Measures in France routinely weighs a 1 kilogram mass, which used to be the 1kg standard. If the fluctuations in measurements of this 1kg mass are smaller than required for mathematical consistency, they can rule out that theory.

A 5,000:1 odds bet

The outcome of the experiment, or other evidence emerging that would confirm the quantum versus classical nature of spacetime, is the subject of a 5,000:1 odds bet between Professor Oppenheim and theoretical physicists Carlo Rovelli and Geoff Penington. Rovelli and Penington are leading proponents of quantum loop gravity and string theory, respectively.

For the past five years, the UCL research group has been stress-testing the theory and exploring its consequences.

Professor Oppenheim said:

Quantum theory and Einstein’s theory of general relativity are mathematically incompatible with each other. So it’s important to understand how this contradiction is resolved. Should spacetime be quantized, or should we modify quantum theory, or is it something else entirely? Now that we have a consistent fundamental theory in which spacetime does not get quantized, it’s anybody’s guess.

The experimental proposal

Co-author Zach Weller-Davies, who, as a Ph.D. student at UCL, helped develop the experimental proposal and made key contributions to the theory itself, said:

This discovery challenges our understanding of the fundamental nature of gravity but also offers avenues to probe its potential quantum nature.

We have shown that if spacetime doesn’t have a quantum nature, then there must be random fluctuations in the curvature of spacetime which have a particular signature that can be verified experimentally.

In both quantum gravity and classical gravity, spacetime must be undergoing violent and random fluctuations all around us, but on a scale which we haven’t yet been able to detect. But if spacetime is classical, the fluctuations have to be larger than a certain scale, and this scale can be determined by another experiment where we test how long we can put a heavy atom in superposition* of being in two different locations.

The analytical and numerical calculations of co-authors Carlo Sparaciari and Barbara Šoda helped guide the project. They expressed hope that these experiments could determine whether the pursuit of a quantum theory of gravity is the right approach.

More about the proposal

Šoda (formerly UCL Physics & Astronomy, now at the Perimeter Institute of Theoretical Physics, Canada) said:

Because gravity is made manifest through the bending of space and time, we can think of the question in terms of whether the rate at which time flows has a quantum nature, or classical nature.

And testing this is almost as simple as testing whether the weight of a mass is constant, or appears to fluctuate in a particular way.

Sparaciari (UCL Physics & Astronomy) said:

While the experimental concept is simple, the weighing of the object needs to be carried out with extreme precision.

But what I find exciting is that starting from very general assumptions, we can prove a clear relationship between two measurable quantities, the scale of the spacetime fluctuations, and how long objects like atoms or apples can be put in quantum superposition of two different locations. We can then determine these two quantities experimentally.

Weller-Davies added:

A delicate interplay must exist if quantum particles such as atoms are able to bend classical spacetime. There must be a fundamental trade-off between the wave nature of atoms, and how large the random fluctuations in spacetime need to be.

Einstein’s gravity and quantum mechanics background

Quantum mechanics. All the matter in the universe obeys the laws of quantum theory, but we only really observe quantum behavior at the scale of atoms and molecules. Quantum theory tells us that particles obey Heisenberg’s uncertainty principle, and we can never know their position or velocity at the same time. In fact, they don’t even have a definite position or velocity until we measure them. Particles like electrons can behave more like waves and act almost as if they can be in many places at once (more precisely, physicists describe particles as being in a “superposition” of different locations).

Quantum theory governs everything from the semiconductors that are ubiquitous in computer chips, to lasers, superconductivity and radioactive decay. In contrast, we say that a system behaves classically if it has definite underlying properties. A cat appears to behave classically: it is either dead or alive, not both, nor in a superposition of being dead and alive. Why do cats behave classically, and small particles quantumly? We don’t know, but the postquantum theory doesn’t require the measurement postulate, because the classicality of spacetime infects quantum systems and causes them to localize.

About gravity

Einstein’s gravity. Newton’s theory of gravity gave way to Einstein’s theory of general relativity (GR), which holds that gravity is not a force in the usual sense. Instead, heavy objects such as the sun bend the fabric of spacetime in such a way that causes Earth to revolve around it. Spacetime is just a mathematical object consisting of the three dimensions of space, and time considered as a fourth dimension. General relativity predicted the formation of black holes and the Big Bang. It holds that time flows at different rates at different points in space, and the GPS in your smartphone needs to account for this to properly determine your location.

Illustration at top

At the top of this article is an artistic version of Figure 1 in the PRX paper. It depicts an experiment in which heavy particles (illustrated as the moon) cause an interference pattern (a quantum effect), while also bending spacetime. The hanging pendulums depict the measurement of spacetime. The actual experiment typically uses Carbon-60, one of the largest known molecules. The UCL calculation indicates that the experiment should also use higher density atoms such as gold. Image via Isaac Young/ University College London. Used with permission.

Physical Review X paper
Nature Communications paper
Public lecture by Professor Jonathan Oppenheim in January 2024
Professor Oppenheim’s academic profile
UCL Physics & Astronomy
UCL Mathematical & Physical Sciences

Bottom line: Einstein’s gravity and quantum mechanics are the two bases for modern physics. But these two theories contradict each other. Have we reached a reconciliation?

Via UCL

The post Einstein’s gravity and quantum mechanics united at last? first appeared on EarthSky.

The Audubon Society’s Christmas Bird Count is one of the longest-running citizen science projects. It had a modest beginning on Christmas Day in 1900. And it’s since become a strong data-gathering project to study bird population trends. This year’s count – the 124th – runs from December 14, 2023, to January 5, 2024. You have to sign up in advance, and the signup has already begun. Go here to sign up for the Christmas Bird Count 2023.

Available now! 2024 EarthSky lunar calendar. A unique and beautiful poster-sized calendar showing phases of the moon every night of the year! Makes a great gift.

Audubon Christmas Bird Count – how it’s done

The Christmas Bird Count is a carefully run event. Each count site is a 15-mile (24-km) wide circle; you can see what it looks like by zooming in on this map to inspect a region near you. Counts for each circle are organized by a “circle compiler.” On the day of the count (set by the circle’s compiler), people head out to designated routes within a circle to count every species and number of birds that they see and hear during the day. And, if you live within the range of a count site, you can also tally the birds you see in your yard and at the feeder.

To participate in the count – it’s free – you need to sign up with a local circle compiler at the Audubon’s website. If you’re a beginning birder, you’ll be matched up with a more experienced birder. Make sure you register early, because the compiler will need time to organize the event.

In addition, you can share your bird count photographs and experiences on social media with the hashtag #ChristmasBirdCount. We here at EarthSky would love to have you send us your photographs, too!

Audubon Christmas Bird Count history

In some parts of the U.S., there used to be bird-hunting competitions on Christmas Day. However, Frank M. Chapman, an ornithologist at the American Museum of Natural History, came up with an alternative, an activity to count birds in a given area each Christmas to build up a record of their numbers.

That first count was in 1900. Overall, 27 birders conducted counts at 25 sites, tallying about 89 bird species.

Since then, the Christmas Bird Count has come a long way. It’s continued annually since the inaugural event, growing in volunteers and census sites. For instance, the 121st Christmas Bird Count took place from December 14, 2020, to January 5, 2021. That count occurred at 2,459 locations, with 72,815 volunteers in the U.S., Canada, Latin America, the Caribbean and Pacific Islands. Altogether, volunteers observed a total of 2,355 bird species.

What have we learned from these counts?

Additionally, Audubon and other research groups use Christmas Bird Count data to monitor population trends that will help guide conservation efforts. To date, scientists have published more than 300 peer-reviewed studies based on this data. The data is also used by federal agencies to craft policy on bird conservation.

Each annual count provides a snapshot of the birds at a given time and place. It’s hard to draw conclusions from one year to the next, because changes happen gradually. To understand trends, scientists do a statistical analysis of data taken over several years.

Warning signs of environmental degradation show up in declines of bird populations in some types of habitats. For instance, the sharpest declines in bird populations have been in grassland habitats, followed by coastal habitats.

Bird census data also informs scientists about the effects of climate change on wildlife. In a 2014 report, National Audubon predicted how the ranges of 588 species of birds in North America could be affected by climate change. They concluded that more than 314 species could lose over 50% of their current climatic range by 2080.

Bottom line: Audubon’s 124th Christmas Bird Count will take place from December 14, 2023, to January 5, 2024. You can join in to help collect important data about birds. Find out how to join in the Audubon Christmas Bird Count.

The post Audubon Christmas Bird Count signup has begun first appeared on EarthSky.

Ofer Cohen, UMass Lowell

The Earth’s magnetic field plays a big role in protecting people from hazardous radiation and geomagnetic activity that could affect satellite communication and the operation of power grids. And the magnetic field moves and flips.

Scientists have studied and tracked the motion of the magnetic poles for centuries. The historical movement of these poles indicates a change in the global geometry of Earth’s magnetic field. It may even indicate the beginning of a field reversal – a flip – between the north and south magnetic poles.

I’m a physicist who studies the interaction between the planets and space. While the north magnetic pole moving a little bit isn’t a big deal, a reversal could have a big impact on Earth’s climate and our modern technology. But these reversals don’t happen instantaneously. Instead, they occur over thousands of years.

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Magnetic field generation

So how are magnetic fields like the one around Earth generated?

Moving electric charges are what generate magnetic fields. A material that enables charges to move easily in it is called a conductor. Metal is one example of a conductor; people use it to transfer electric currents from one place to the other. The electric current itself is simply negative charges called electrons moving through the metal. This current generates a magnetic field.

The Earth’s liquid iron core has layers of conducting material. Currents of charges move throughout the core. And the liquid iron is also moving and circulating in the core. These movements generate the magnetic field.

Irregularities in a magnetic field

Earth isn’t the only planet with a magnetic field; gas giant planets like Jupiter have a conducting metallic hydrogen layer that generates their magnetic fields.

The movement of these conducting layers inside planets results in two types of fields. Larger motions, such as large-scale rotations with the planet, lead to a symmetric magnetic field with a north and a south pole … similar to a toy magnet.

These conducting layers may have some local irregular motions due to local turbulence or smaller flows that do not follow the large-scale pattern. These irregularities will manifest in some small anomalies in the planet’s magnetic field or places where the field deviates from being a perfect dipole field.

These small-scale deviations in the magnetic field can actually lead to changes in the large-scale field over time. And they can potentially cause a complete reversal of the polarity of the dipole field, where the north becomes south and vice versa. The designations of “north” and “south” on the magnetic field refer to their opposite polarities; they’re not related to geographic north and south.

The Earth’s magnetosphere, a protective bubble

The Earth’s magnetic field creates a magnetic “bubble” called the magnetosphere above the uppermost part of the atmosphere, the ionosphere layer.

The magnetosphere plays a major role in protecting people. It shields and deflects damaging, high-energy, cosmic-ray radiation, which is created in star explosions and moves constantly through the universe. The magnetosphere also interacts with solar wind, which is a flow of magnetized gas from the sun.

The magnetosphere and ionosphere’s interaction with magnetized solar wind creates what scientists call space weather. Usually, the solar wind is mild and there’s little to no space weather.

However, there are times when the sun sheds large magnetized clouds of gas – or coronal mass ejections – into space. If these coronal mass ejections make it to Earth, their interaction with the magnetosphere can generate geomagnetic storms. Geomagnetic storms can create auroras, which happen when a stream of energized particles hits the atmosphere and lights up.

During space weather events, there’s more hazardous radiation near Earth. This radiation can potentially harm satellites and astronauts. Space weather can also damage large conducting systems, such as major pipelines and power grids, by overloading currents in these systems.

Space weather events can also disrupt satellite communication and GPS operation, which many people rely on.

Field flips

Scientists map and track the overall shape and orientation of the Earth’s magnetic field using local measurements of the field’s orientation and magnitude and, more recently, models.

The location of the north magnetic pole has moved by about 600 miles (965 km) since it was first measured in 1831. The migration speed has increased from 10 miles per year to 34 miles per year (16 km to 54 km) in more recent years. This acceleration could indicate the beginning of a field reversal, but scientists really can’t tell with less than 200 years of data.

The Earth’s magnetic field reverses on time scales that vary between 100,000 to 1,000,000 years. Scientists can tell how often the magnetic field reverses by looking at volcanic rocks in the ocean.

These rocks capture the orientation and strength of the Earth’s magnetic field when they are created. So dating these rocks provides a good picture of how the Earth’s field has evolved over time.

Field reversals happen fast from a geologic standpoint, though slow from a human perspective. A reversal usually takes a few thousand years. But during this time, the magnetosphere’s orientation may shift and expose more of the Earth to cosmic radiation. These events may change the concentration of ozone in the atmosphere.

Scientists can’t tell with confidence when the next field reversal will happen, but we can keep mapping and tracking the movement of Earth’s magnetic north.

Ofer Cohen, Associate Professor of Physics and Applied Physics, UMass Lowell

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: Earth’s magnetic field helps protect life on Earth. But the magnetic poles wander, and they flip polarity every 100,000 to 1,000,000 years.

The post Earth’s magnetic field shields us. But it can move and flip first appeared on EarthSky.

Derryck Telford Reid, a professor of physics at Heriot-Watt University in Edinburgh, Scotland, wrote this article. It was published originally at The Conversation with the title “How we’re building the world’s biggest optical telescope to crack some of the greatest puzzles in science.”

The world’s largest optical telescope

Astronomers get to ask some of the most fundamental questions there are, ranging from whether we’re alone in the cosmos to what the nature of the mysterious dark energy and dark matter making up most of the universe is.

Now a large group of astronomers from all over the world is building the biggest optical telescope ever – the Extremely Large Telescope (ELT) – in Chile. Once construction is completed in 2028, it could provide answers that transform our knowledge of the universe.

With its 39-meter (128-foot) diameter primary mirror, the ELT will contain the largest, most perfect reflecting surface ever made. Its light-collecting power will exceed that of all other large telescopes combined, enabling it to detect objects millions of times fainter than the human eye can see.

There are several reasons why we need such a telescope. Its incredible sensitivity will let it image some of the first galaxies ever formed, with light that has traveled for 13 billion years to reach the telescope. Observations of such distant objects may allow us to refine our understanding of cosmology and the nature of dark matter and dark energy.

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Alien life

The ELT may also offer an answer to the most fundamental question of all: Are we alone in the universe? The ELT is expected to be the first telescope to track down Earth-like exoplanets. These are planets that orbit other stars but have a similar mass, orbit and proximity to their host as Earth.

Occupying the so-called Goldilocks zone, these Earth-like planets will orbit their star at just the right distance for water to neither boil nor freeze, providing the conditions for life to exist.

The ELT’s camera will have six times better resolution than that of the James Webb Space Telescope. This resolution will allow it to take the clearest images yet of exoplanets. But fascinating as these pictures will be, they will not tell the whole story.

To learn if life is likely to exist on an exoplanet, astronomers must complement imaging with spectroscopy. While images reveal shape, size and structure, spectra tell us about the speed, temperature and even the chemistry of astronomical objects.

The world’s largest optical telescope will examine exoplanets

The ELT will contain not one but four spectrographs. Spectrographs are instruments that disperse light into its constituent colors, much like the iconic prism on the Pink Floyd’s The Dark Side of the Moon album cover.

Each about the size of a minibus, and carefully environmentally controlled for stability, these spectrographs underpin all of the ELT’s key science cases. For giant exoplanets, the Harmoni instrument will analyze light that has traveled through their atmospheres, looking for the signs of water, oxygen, methane, carbon dioxide and other gases that indicate the existence of life.

To detect much smaller Earth-like exoplanets, the more specialized Andes instrument will be needed. With a cost of around €35 million (£30 million or $38 million), Andes will be able to detect tiny changes in the wavelength of light.

From previous satellite missions, astronomers already have a good idea of where to look in the sky for exoplanets. Indeed, there have been several thousand confirmed or “candidate” exoplanets detected using the transit method. Here, a space telescope stares at a patch of sky containing thousands of stars and looks for tiny, periodic dips in their intensities, caused when an orbiting planet passes in front of its star.

Looking for tiny wobbles

But Andes will use a different method to hunt for other Earths. As an exoplanet orbits its host star, its gravity tugs on the star, making it wobble. This movement is incredibly small. Earth’s orbit causes the sun to oscillate at just 10 centimeters per second … the walking speed of a tortoise.

Just as the pitch of an ambulance siren rises and falls as it travels toward and away from us, the wavelength of light observed from a wobbling star increases and decreases as the planet traces out its orbit.

Extreme precision

Remarkably, Andes will be able to detect this minuscule change in the light’s color. Starlight, while essentially continuous (“white”) from the ultraviolet to the infrared, contains bands where atoms in the outer region of the star absorb specific wavelengths as the light escapes, appearing dark in the spectra.

Tiny shifts in the positions of these features – around 1/10,000th of a pixel on the Andes sensor – may, over months and years, reveal the periodic wobbles. This could ultimately help us to find an Earth 2.0.

At Heriot-Watt University, we are piloting the development of a laser system known as a frequency comb. This system will enable Andes to reach such exquisite precision. Like the millimeter ticks on a ruler, the laser will calibrate the Andes spectrograph by providing a spectrum of light structured as thousands of regularly spaced wavelengths.

This scale will remain constant over decades, mitigating the measurement errors that occur from environmental changes in temperature and pressure.

With the ELT’s construction cost coming in at €1.45 billion ($1.58 billion), some will question the value of the project. But astronomy has a significance that spans millennia and transcends cultures and national borders. It is only by looking far outside our solar system that we can gain a perspective beyond the here and now.

Derryck Telford Reid, Professor of Physics, Heriot-Watt University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: The world’s largest optical telescope will be the Extremely Large Telescope, currently under construction in the Chilean desert. It will get a good look at exoplanets, including their atmospheres, and help us look for life in our galaxy.

The post World’s largest optical telescope – the ELT – going up in Chile first appeared on EarthSky.

When is the next meteor shower? Click here for EarthSky’s meteor shower guide

It’s meteor time! There are several meteor showers starting in December and around the December solstice. How can you optimize your chances for seeing the most meteors? Follow the tips below. See EarthSky’s meteor guide for upcoming meteor showers.

1. Know the peak time

Meteor showers generally happen over many days as Earth encounters a wide stream of icy particles in space. These particles are debris left behind by a comet. The peak is a point in time when Earth is expected to encounter the greatest number of comet particles. To find the peak dates of meteor showers, try EarthSky’s meteor guide.

And here’s the catch … the peak of the shower comes at the same time for all of us on Earth. Meanwhile, our clocks are saying different times. You’ll often need to adjust from UTC to your local time.

The predictions are not always right on the money, by the way. And remember … it’s possible to see nice meteor displays in the hours – even days – before or after the predicted peak.

Just remember, meteor showers are part of nature. They often defy prediction.

2. Location, location, location

We can’t say this strongly enough. You need a dark place to observe in the country. Visit EarthSky’s Best Places to Stargaze.

And … you need a wide-open view of the sky. A farmer’s field? A stretch of country road? A campsite with a clear view in one or more directions? An open sky will increase your chances of seeing some meteors.

3. Oh no! The moon is out

In meteor showers, a bright moon is not your friend. Nothing dampens the display of a meteor shower more effectively than a bright moon.

If the moon is out, look at areas of the sky away from the moon. Anything in the moon’s vicinity – including meteors – will likely be washed out by its bright light. Another tip for watching in moonlight: place some object between yourself and the moon. Observing from the shadow of a barn, or vehicle, even a tree, can help you see more meteors.

4. Know the expected rate

Here we touch on a topic that sometimes leads to some disappointment, especially among novice meteor-watchers: the rate.

Tables of meteor showers almost always list what is known as the zenithal hourly rate (ZHR) for each shower.

The ZHR is the number of meteors you’ll see if you’re watching in a very dark sky, with the radiant overhead, when the shower is at its peak. In other words, the ZHR represents the number of meteors you might see per hour given the very best observing conditions during the shower’s maximum.

If the peak occurs when it’s still daylight at your location, if most of the meteors are predominantly faint, if a bright moon is out, or if you’re located in a light-polluted area, the total number of meteors you see will be considerably reduced.

5. Don’t worry too much about radiant points

You don’t need to stare all night in a single direction – or even locate the radiant point – to have fun watching the shower. The meteors will appear all over the sky.

But … although you can see meteors shoot up from the horizon before a shower’s radiant rises, you’ll see more meteors after it rises. And you’ll see the most when the radiant is highest in the sky. So find out the radiant point’s rising time. It can help you pinpoint the best time of night to watch the shower.

And … the radiant point is interesting. If you track meteors backward on the sky’s dome, you’ll find them streaming from their radiant point, a single point within a given constellation. Hence the meteor shower’s name.

6. Watch for an hour or more

Meteor showers will be better if you let your eyes adapt to the dark. That can take as long as 20 minutes. Plus, the meteors tend to come in spurts, followed by lulls. Be patient! You’ll see some.

7. Notice the meteors’ speeds and colors

The Leonid meteors seem to zip across the sky, while the Taurids are slow enough everyone can see them when someone yells “Meteor!” Also, some meteor showers, such as the Perseids, can be colorful. Another beloved shower, the Geminids, tend to be bright and white.

8. Watch for meteor trains

A meteor train is a persistent glow in the air left by some meteors after they have faded from view. Trains are from luminous ionized matter left in the wake of this incoming space debris.

9. Bring a blanket, a buddy, a hot drink and a lawn chair

A reclining lawn chair helps you lie back in comfort for an hour or more of meteor-watching.

If several of you are watching, take different parts of the sky. If you see one, shout “Meteor!” Dress warmly; the nights can be cool or cold, even during the spring and summer months. You’ll probably appreciate that blanket and warm drink in the wee hours of the morning. Also, leave your laptops and tablets home; even using the nighttime dark mode will ruin your night vision. And this will be tough on some people: leave your cell phone in your pocket or the car. It can also ruin your night vision.

10. Enjoy nature

Relax and enjoy the night sky. Not every meteor shower is a winner. Sometimes, you may come away from a shower seeing only one meteor. But if that one meteor is bright, and takes a slow path across a starry night sky … it’ll be worth it.

To be successful at observing any meteor shower, you need to get into a kind of zen state, waiting and expecting the meteors to come to you, if you place yourself in a good position (country location, wide open sky) to see them.

Or forget the zen state, and let yourself be guided by this old meteor watcher’s motto:

You might see a lot or you might not see many, but if you stay in the house, you won’t see any.

Photos of meteors from EarthSky’s community

Post your own photos at EarthSky Community Photos

Bottom line: Meteor showers are unpredictable but always a fun and relaxing time. Maximize your viewing time with these tips.

The post Winter meteor showers are here: Top 10 tips for watching first appeared on EarthSky.

Between now and early December, radio signals used to send commands from Earth to Mars spacecraft – and to receive signals from the spacecraft – can be disturbed by the sun’s corona, its outermost atmosphere. So communications from Earth with spacecraft, landers, rovers and future humans at the red planet are currently limited. Reprinted from the European Space Agency. Edits by EarthSky.

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Mars spacecraft fall silent

The space between Earth and Mars is usually buzzing with science data, telemetry and commands racing to and from almost a dozen missions at the red planet. But for roughly 1 1/2 days, communication between the planets will fall silent as Mars passes behind the sun on November 18.

Solar conjunction for Mars occurs roughly once every 25 months. During conjunction, Mars is located on the opposite side of the sun from Earth.

Around the time of conjunction, the radio signals used to send commands from Earth to the spacecraft and to receive signals from the spacecraft can be disturbed by the sun’s active atmosphere, the solar corona.

The period of time during which communications are significantly disturbed depends on the size and power of a Mars spacecraft’s communication equipment. But it typically takes place while the angle in the sky between the sun and Mars as seen from Earth is within 3 to 4 degrees.

In 2023, this period lasts from early November to early December.

No earthly instructions for Mars spacecraft

As a result of the disruption, mission controllers can’t reliably send commands to, or receive data from, their spacecraft. Special precautions have to be taken.

For ESA’s Mars Express and ExoMars Trace Gas Orbiter (known as MEX and TGO, because we enjoy our acronyms), this means uplinking all the critical instructions the spacecraft would need to operate without any contact from Earth for the entire period. That’s three or four weeks of commands when we normally send up only one week at a time.

Of course, these conjunctions also affect the missions of other space agencies, and this kind of thing isn’t unique to Mars.

Ground stations to full power!

Due to the disturbance from the sun’s atmosphere during conjunction season, we have to reduce the amount of data we exchange with MEX and TGO.

We cut the amount of data that we “uplink” to MEX, for example, down from 2000 bits per second to just 250, and reduce the amount of data that MEX sends down to Earth to as little as 300 bits per second.

We also set our Estrack ground stations to maximum transmission power to make sure our spacecraft hears us loud and clear despite the disturbance, i.e., we use a louder voice but say fewer words.

This limits the kind of information that MEX can send to its operators on Earth to “housekeeping” data – health status and telemetry – and is too low for MEX to send any science data.

Like a diver holding their breath, any data gathered by MEX’s instruments during the conjunction period must be stored in the limited onboard memory until the period is over.

What makes the 2023 conjunction special?

Mars Express arrived at the red planet on December 25, 2003, and is one of Europe’s longest-serving missions. The team celebrated 20 years since launch this summer with the 1st-ever live webcast from another planet.

This will be MEX’s tenth solar conjunction and TGO’s third. However, as the orbits of Mars and Earth have slightly different inclinations, Mars doesn’t usually pass directly behind the sun.

The 2023 conjunction is unusual in that it will be the first time that Mars passes behind the disk of the sun since the two ESA spacecraft arrived.

While Mars is behind the sun, for roughly 1 1/2 days on November 17-18, communication with MEX and TGO won’t just be limited, it’ll be impossible.

These windows of limited or impossible communication between Earth and Mars will pose a challenge for future human settlers, too.

Are you worried?

James Godfrey, Spacecraft Operations Manager for Mars Express. said:

At the beginning of the mission, the team was very cautious about conjunctions. If something goes seriously wrong during the conjunction period, it could be difficult to recover the spacecraft until it’s over.

We used to suspend all science operations. But, over the years, we’ve only ever experienced minor disruptions.

In 2019, we discovered that we can continue using some of MEX’s instruments in a limited way, as long as all commands are uploaded before the season begins, and all science data are stored on board until the season ends.

Originally, planning for conjunctions was a very manual process. But over the years, it’s become largely routine.

Peter Schmitz, Spacecraft Operations Manager for Trace Gas Orbiter, added:

With its larger communications antenna and data storage capacity, TGO is able to continue with its data relay activities for Mars surface assets throughout the conjunction period – even when Mars is directly behind the sun – and prepare to downlink all of the stored data to Earth when it is once again safe to do so.

Bottom line: Solar conjunction for Mars happened yesterday, November 18, 2023. That’s when Mars was most directly behind the sun for this 25-month period. In 2023, the season of Mars’ conjunction takes place between November 5 and December. During this period, data exchange between Mars spacecraft and Earth is limited.

Via ESA

The post Mars spacecraft fall silent as red planet goes behind sun first appeared on EarthSky.