As a field, the Search for Extraterrestrial Intelligence suffers from some rather significant constraints. Aside from the uncertainty involved (e.g., is there life beyond Earth we can actually communicate with?), there are the limitations imposed by technology and the very nature of space and time. For instance, scientists are forced to contend with the possibility that by the time a message is received by an intelligent species, the civilization that sent it will be long dead.
Harvard astronomers Amir Siraj and Abraham Loeb tackle this very question in a new study that recently appeared online. Taking their cue from the Copernican Principle, which states that humanity and Earth are representative of the norm (and not an outlier), they calculated that if any transmissions from Earth were heard by an extraterrestrial technological civilization (ETC), it would take about 3000 years to get a reply.
The globally distributed dishes of the European VLBI Network are linked with each other and the 305-m William E. Gordon Telescope at the Arecibo Observatory in Puerto Rico. Credit: Danielle Futselaar
Loeb is also renowned for theorizing that the interstellar object ‘Oumuamua, which flew past Earth in 2017, could have been extraterrestrial lightsail. This theory was originally put forth in a 2018 paper he co-wrote with postdoctoral researcher Shmuel Bialy (of the ITC). The arguments presented therein have since been expanded upon in Loeb’s most recent book, Extraterrestrial: The First Sign of Intelligent Life Beyond Earth.
Prof. Loeb recently partnered with Dr. Frank Laukien and other colleagues to launch the Galileo Project, a multinational non-profit dedicated to the study of Unidentified Aerial Phenomena (UAPs). Siraj serves as the Director of Interstellar Object Studies for this project, and he and Loeb have published extensively on subjects ranging from black holes and meteors to panspermia and interstellar objects (many of which were on the subject of ‘Oumuamua).
For the sake of this study, Siraj and Loeb focused on a particular aspect of SETI, which they dubbed the Search for Extraterrestrial Responding Intelligence (SETRI). By this, they mean ETIs that would be motivated to message Earth in response to the detection of technological activity on our planet (aka. “technosignatures”). This addresses a question of growing importance to the SETI community.
In short, does humanity have a chance of ever hearing from an ETC before our civilization collapses or is wiped out by a natural disaster? As Siraj told Universe Today via email:
“It is important to estimate the response time from extraterrestrial responding intelligences (ETRIs) since such an estimate informs the nature of effective SETI searches — as well the implications of a confirmed signal if we ever receive one. The question we try to answer in our paper is: when might we expect our first cosmic conversation to take place?”
This artist’s impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. Credit: ESO/M. Kornmesser
This establishes the first parameter of their study, which was the amount of time that humanity has been emitting detectable signatures. Of all potential technosignatures that have been considered to date, the most likely and most widely investigated by SETI researchers are still radio transmissions. In keeping with the Copernican Principle, we can assume that ETIs are also engaged in the search for signs of intelligence other than their own.
“The Copernican principle asserts that we are unlikely to live at a privileged time and so the likelihood of another habitable planet like Earth going right now through an analog of our first century of radio communication, given a few billion years of its history, is below one part in ten million,” said Loeb. “Therefore, a response is expected only within a large enough volume, containing more than ten million stars.”
It can also be safely assumed that an ETI would see radio signals as a possible technosignature and would be actively listening for them. The first long-range radio broadcast took place in 1901, when Italian inventor Guglielmo Marconi sent the first transatlantic broadcast from Cornwall, England, to St. John’s, Newfoundland. Since then, humans have been sending radio transmissions to space without thinking about the consequences.
This means that if there is a civilization within a hundred light-years of Earth with sensitive radio telescopes, they may have already heard from us. In short, we may have already “started a conversation” with an intelligent species and are just waiting for a response. Beyond this, said Siraj, they went with a number of parameters that were consistent with the Copernican Principle and the conditions under which life is known to flourish:
“[W]e considered ETIs able to communicate via electromagnetic radiation, located on Earth-like planets orbiting Sun-like stars (aka, “life as we know it”). Furthermore, we considered radio signals (which at the speed of light) as well as physical probes, which would travel slower. We used the Copernican principle, which is inherently optimistic about the prevalence of life in the Universe, to establish a lower limit on the expected response time from ETRIs.
In this illustration, NASA’s Hubble Space Telescope is looking along the paths of NASA’s Voyager 1 and 2 spacecraft as they journey through the solar system and into interstellar space. Credit: NASA/ESA/Z. Levy (STScI).
Transmission technologies can extend beyond radio waves to include other types of electromagnetic (EM) radiation, such as microwave lasers, X-rays, gamma-rays, and more. Since the only constraint is the speed of light – 299,792,458 m/s (1079 million km/h; 670.6 million mph) – it remains the fastest available option. It also means humans would only need to wait until the 22nd century for a transmission from a civilization located a hundred light-years away.
That being said, it is also possible that an ETC would choose to explore our planet more closely rather than send a transmitted reply. In this respect, Siraj and Loeb considered possibilities like theVoyager 1 and 2missions, New Horizons, and thePioneer 10 and 11 spacecraft. All of these robotic missions have or will enter interstellar space (or will in the near future) and could someday be intercepted by an ETC.
It was for this reason that the Pioneer Plaques and the Golden Records were created. However, it will take millions of years before any of these missions reach even the closest star systems to Earth. This means that if a civilization sent a probe to investigate Earth in response to radio signals from a hundred years ago, it wouldn’t arrive for hundreds of thousands of years. As Loeb explained:
“Although the latter response method results in physical contact with alien objects, it requires millions of years for the journey across a hundred light-years. This means that we still have a waiting time as long as the time that has elapsed since humans first appeared on Earth before we will witness chemically-propelled crafts in response to our radio broadcasts.”
This graphic shows the relative positions of NASA’s most distant spacecraft in early 2011, looking at the solar system from the side. Credit: NASA/JPL-Caltech
Other possible concepts, like directed-energy propulsion (a la Breakthrough Starshot), could make the transit in much less time – at 20% the speed of light, it would reach Alpha Centauri in just 20 years. However, such concepts are effective for reaching the nearest star systems, but not stars 1000 light-years away within a reasonable timeline. As a final parameter, they considered just how many planets out there are likely to host an ETC.
“The Copernican principle asserts that we are unlikely to live at a privileged time and so the likelihood of another habitable planet like Earth going right now through an analog of our first century of radio communication, given a few billion years of its history, is below one part in ten million,” said Loeb. Working from this, they determined that a response could only be expected within a large enough volume, containing more than ten million stars.
Assuming that our galaxy is relatively homogenous in terms of the distribution of stars in its disk, this results in a volume of 1 billion cubic light-years (ly3) or one thousand light-years in any direction. This, in turn, entails a two-way travel time of more than two thousand years. This essentially means that if an ETC is aware of us and wants to talk, we would not be hearing from them until 4000 CE at the earliest. Or as Siraj summarized:
“We found that the fact that we have only existed as a technological civilization for about a hundred years means that, right now, we should not expect to hear back from an extraterrestrial civilization in response to our own signals. In other words, it’s extraordinarily unlikely that we could start a cosmic conversation.”
An artist’s illustration of a light-sail powered by a radio beam (red) generated on the surface of a planet. Credit: M. Weiss/CfA
This conclusion is supported by previous research (conducted with the help of Dr. Frank Drake himself!) that indicated that within various parameters, a call-and-answer scenario would take longer than the average civilization’s lifespan. In other words, any signals we receive from an ETC (whether they are a response or an attempt to “start a conversation”) are likely to have been sent by a species that has since become extinct.
This, according to Siraj, is the most significant aspect of their study, which is that civilizations have a life expectancy (which they have a measure of control over). In essence, it underscores the importance of ensuring that humanity doesn’t succumb to self-destruction or a cataclysmic fate. “The big takeaway here is that we’d better get our act together and figure out how to survive long-term if we ever want to participate in a cosmic conversation!”
More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.
That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.
“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”
The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.
Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.
Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.
Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.
Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.
Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.
“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”
The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.
North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.
Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”
Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.
Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.
For Dello, the “fingerprints of climate change” were clear.
“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”
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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.
On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.
They call it “Big Sam.”
The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.
It didn’t die alone.
“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.
She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”
“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.
The head alone, she said, is about the size of a baby elephant.
The discovery was a long time coming.
The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.
“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.
When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”
“It contains about 100 to 300 bones per square metre,” she said.
Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.
About a year ago, they found the second adult: Big Sam.
Bamforth said both dinosaurs are believed to have been the elders in the herd.
“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.
“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”
The genders of the two adults are unknown.
Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.
The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.
She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.
“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.
“It’s pretty exciting.”
This report by The Canadian Press was first published Sept. 25, 2024.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
