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Why people rebuild in Appalachia’s flood-ravaged areas despite the risks

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theconversation.com – Kristina P. Brant, Assistant Professor of Rural Sociology, Penn State – 2025-02-26 07:38:00

Why people rebuild in Appalachia’s flood-ravaged areas despite the risks

Parts of the North Fork of the Kentucky River flooded in July 2022, and again in February 2025.
Arden S. Barnes/For The Washington Post via Getty Images

Kristina P. Brant, Penn State

On Valentine’s Day 2025, heavy rains started to fall in parts of rural Appalachia. Over the course of a few days, residents in eastern Kentucky watched as river levels rose and surpassed flood levels. Emergency teams conducted over 1,000 water rescues. Hundreds, if not thousands of people were displaced from homes, and entire business districts filled with mud.

For some, it was the third time in just four years that their homes had flooded, and the process of disposing of destroyed furniture, cleaning out the muck and starting anew is beginning again.

Historic floods wiped out businesses and homes in eastern Kentucky in February 2021, July 2022 and now February 2025. An even greater scale of destruction hit eastern Tennessee and western North Carolina in September 2024, when Hurricane Helene’s rainfall and flooding decimated towns and washed out parts of major highways.

YouTube video
Scenes of flooding from several locations across Appalachia in February 2025.

Each of these events was considered to be a “thousand-year flood,” with a 1-in-1,000 chance of happening in a given year. Yet they’re happening more often.

The floods have highlighted the resilience of local people to work together for collective survival in rural Appalachia. But they have also exposed the deep vulnerability of communities, many of which are located along creeks at the base of hills and mountains with poor emergency warning systems. As short-term cleanup leads to long-term recovery efforts, residents can face daunting barriers that leave many facing the same flood risks over and over again.

Exposing a housing crisis

For the past nine years, I have been conducting research on rural health and poverty in Appalachia. It’s a complex region often painted in broad brushstrokes that miss the geographic, socioeconomic and ideological diversity it holds.

Appalachia is home to a vibrant culture, a fierce sense of pride and a strong sense of love. But it is also marked by the omnipresent backdrop of a declining coal industry.

There is considerable local inequality that is often overlooked in a region portrayed as one-dimensional. Poverty levels are indeed high. In Perry County, Kentucky, where one of eastern Kentucky’s larger cities, Hazard, is located, nearly 30% of the population lives under the federal poverty line. But the average income of the top 1% of workers in Perry County is nearly US$470,000 – 17 times more than the average income of the remaining 99%.

This income and wealth inequality translates to unequal land ownership – much of eastern Kentucky’s most desirable land remains in the hands of corporations and families with great generational wealth.

When I first moved to eastern Kentucky in 2016, I was struck by the grave lack of affordable, quality housing. I met families paying $200-$300 a month for a small plot to put a mobile home. Others lived in “found housing” – often-distressed properties owned by family members. They had no lease, no equity and no insurance. They had a place to lay one’s head but lacked long-term stability in the event of disagreement or disaster. This reality was rarely acknowledged by local and state governments.

Eastern Kentucky’s 2021 and 2022 floods turned this into a full-blown housing crisis, with 9,000 homes damaged or destroyed in the 2022 flood alone.

“There was no empty housing or empty places for housing,” one resident involved in local flood recovery efforts told me. “It just was complete disaster because people just didn’t have a place to go.”

Most homeowners did not have flood insurance to assist with rebuilding costs. While many applied to the Federal Emergency Management Agency for assistance, the amounts they received often did not go far. The maximum aid for temporary housing assistance and repairs is $42,500, plus up to an additional $42,500 for other needs related to the disaster.

The federal government often provides more aid for rebuilding through block grants directed to local and state governments, but that money requires congressional approval and can take months to years to arrive. Local community coalitions and organizations stepped in to fill these gaps, but they did not necessarily have sufficient donations or resources to help such large numbers of displaced people.

A man walks from a store with lighted rooms above it. In the background, homes are flooded.
Affordable rental housing is hard to find in much of Appalachia. When flooding wipes out homes, as Jackson, Ky., saw in July 2022 and again in February 2025, it becomes even more rare.
Michael Swensen/Getty Images

With a dearth of affordable rentals pre-flood, renters who lost their homes had no place to go. And those living in “found housing” that was destroyed were not eligible for federal support for rebuilding.

The sheer level of devastation also posed challenges. One health care professional told me: “In Appalachia, the way it usually works is if you lose your house or something happens, then you go stay with your brother or your mom or your cousin. … But everybody’s mom and brother and cousin also lost their house. There was nowhere to stay.” From her point of view, “our homelessness just skyrocketed.”

The cost of land – social and economic

After the 2022 flood, the Kentucky Department for Local Government earmarked almost $300 million of federal funding to build new, flood-resilient homes in eastern Kentucky. Yet the question of where to build remained. As another resident involved in local flood recovery efforts told me, “You can give us all the money you want; we don’t have any place to build the house.”

It has always been costly and time-intensive to develop land in Appalachia. Available higher ground tends to be located on former strip mines, and these reclaimed lands require careful geotechnical surveying and sometimes structural reinforcements.

If these areas are remote, the costs of running electric, water and other infrastructure services can also be prohibitive. For this reason, for-profit developers have largely avoided many counties in the region. The head of a nonprofit agency explained to me that, because of this, “The markets have broken. … We have no [housing] market.”

In an aerial view of Kentucky's mountains, now-flat areas where mountain top were mined for their coal are visible.
Eastern Kentucky’s mountains are beautiful, but there are few locations for building homes that aren’t near creeks or rivers. Strip-mined land, where mountaintops were flattened, often aren’t easily accessible and come with their own challenges.
Posnov/Moment via Getty Images

There is also some risk involved in attempting to build homes on new land that has not previously been developed. A local government could pay for undeveloped land to be surveyed and prepared for development, with the prospect of reimbursement by the U.S. Department of Housing and Urban Development if housing is successfully built. But if, after the work to prepare the land, it is still too cost-prohibitive to build a profitable house there, the local government would not receive any reimbursement.

Some counties have found success clearing land for large developments on former strip mine sites. But these former coal mining areas can be considerable distances from towns. Without robust public transportation systems, these distances are especially prohibitive for residents who lack reliable personal transportation.

Another barrier is the high prices that both individual and corporate landowners are asking for properties on higher ground.

The scarcity of desirable land available for sale, combined with increasingly urgent demand, has led to prices unaffordable for most. Another resident involved in local flood recovery efforts explained: “If you paid $5,000 for 30 acres 40 years ago, why won’t you sell that for $100,000? Nope, [they want] $1 million.” That makes it increasingly difficult for both individuals and housing developers to purchase land and build.

One reason for this scarcity is the amount of land that is still owned by outside corporate interests. For example, Kentucky River Properties, formerly Kentucky River Coal Corporation, owns over 270,000 acres across seven counties in the region. While this landholding company leases land to coal, timber and gas companies, it and others like it rarely permit residential development.

But not all unused land is owned by corporations. Some of this land is owned by families with deep roots in the region. People’s attachment to a place often makes them want to stay in their communities, even after disasters. But it can also limit the amount of land available for rebuilding. People are often hesitant to sell land that holds deep significance for their families, even if they are not living there themselves.

Two men dump buckets of ruined wallboard removed from a home. The yard they are walking through is filled with mud.
Rural communities are often tight-knit. Many residents want to stay despite the risks.
AP Photo/Timothy D. Easley

One health care professional expressed feeling torn between selling or keeping their own family property after the 2022 flood: “We have a significant amount of property on top of a mountain. I wouldn’t want to sell it because my papa came from nothing. … His generation thought owning land was the greatest thing. … And for him to provide his children and his grandchildren and their great-grandchildren a plot of land that he worked and sweat and ultimately died to give us – people want to hold onto that.”

She recognized that land was in great demand but couldn’t bring herself to sell what she owned. In cases like hers, higher grounds are owned locally but still remain unused.

Moving toward higher ground, slowly

Two years after the 2022 flood, major government funding for rebuilding still has not resulted in a significant number of homes. The state has planned seven communities on higher ground in eastern Kentucky that aim to house 665 new homes. As of early 2025, 14 houses had been completed.

Progress on providing housing on higher ground is slow, and the need is great.

In the meantime, when I conducted interviews during the summer and fall of 2024, many of the mobile home communities that were decimated in the 2022 flood had begun to fill back up. These were flood-risk areas, but there was simply no other place to go.

Last week, I watched on Facebook a friend’s live video footage showing the waters creeping up the sides of the mobile homes in one of those very communities that had flooded in 2022. Another of my friends mused: “I don’t know who constructed all this, but they did an unjustly favor by not thinking how close these towns was to the river. Can’t anyone in Frankfort help us, or has it gone too far?”

With hundreds more people now displaced by the most recent flood, the need for homes on higher grounds has only expanded, and the wait continues.The Conversation

Kristina P. Brant, Assistant Professor of Rural Sociology, Penn State

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Study shows surge of imagery and fakes can precede international and political violence

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theconversation.com – Tim Weninger, Collegiate Proessor of Engineering, University of Notre Dame – 2025-04-24 07:59:00

AI tools reveal how images have been manipulated.
William Theisen et al.

Tim Weninger, University of Notre Dame and Ernesto Verdeja, University of Notre Dame

Imagine a country with deep political divisions, where different groups don’t trust each other and violence seems likely. Now, imagine a flood of political images, hateful memes and mocking videos from domestic and foreign sources taking over social media. What is likely to happen next?

The widespread use of social media during times of political trouble and violence has made it harder to prevent conflict and build peace. Social media is changing, with new technologies and strategies available to influence what people think during political crises. These include new ways to promote beliefs and goals, gain support, dehumanize opponents, justify violence and create doubt or dismiss inconvenient facts.

At the same time, the technologies themselves are becoming more sophisticated. More and more, social media campaigns use images such as memes, videos and photos – whether edited or not – that have a bigger impact on people than just text.

It’s harder for AI systems to understand images compared with text. For example, it’s easier to track posts that say “Ukrainians are Nazis” than it is to find and understand fake images showing Ukrainian soldiers with Nazi symbols. But these kinds of images are becoming more common. Just as a picture is worth a thousand words, a meme is worth a thousand tweets.

Our team of computer and social scientists has tackled the challenge of interpreting image content by combining artificial intelligence methods with human subject matter experts to study how visual social media posts change in high-risk situations. Our research shows that these changes in social media posts, especially those with images, serve as strong indicators of coming mass violence.

Surge of memes

Our recent analysis found that in the two weeks leading up to Russia’s 2022 invasion of Ukraine there was a nearly 9,000% increase in the number of posts and a more than 5,000% increase in manipulated images from Russian milbloggers. Milbloggers are bloggers who focus on current military conflicts.

These huge increases show how intense Russia’s online propaganda campaign was and how it used social media to influence people’s opinions and justify the invasion.

This also shows the need to better monitor and analyze visual content on social media. To conduct our analysis, we collected the entire history of posts and images from the accounts of 989 Russian milbloggers on the messaging app Telegram. This includes nearly 6 million posts and over 3 million images. Each post and image was time-stamped and categorized to facilitate detailed analysis.

Media forensics

We had previously developed a suite of AI tools capable of detecting image alterations and manipulations. For instance, one detected image shows a pro-Russian meme mocking anti-Putin journalist and former Russian soldier Arkady Babchenko, whose death was faked by Ukrainian security services to expose an assassination plot against him.

The meme features the language “gamers don’t die, they respawn,” alluding to video game characters who return to life after dying. This makes light of Babchenko’s predicament and illustrates the use of manipulated images to convey political messages and influence public opinion.

This is just one example out of millions of images that were strategically manipulated to promote various narratives. Our statistical analysis revealed a massive increase in both the number of images and the extent of their manipulations prior to the invasion.

Political context is critical

Although these AI systems are very good at finding fakes, they are incapable of understanding the images’ political contexts. It is therefore critical that AI scientists work closely with social scientists in order to properly interpret these findings.

Our AI systems also categorized images by similarity, which then allowed subject experts to further analyze image clusters based on their narrative content and culturally and politically specific meanings. This is impossible to do at a large scale without AI support.

For example, a fake image of French president Emmanuel Macron with Ukrainian governor Vitalii Kim may be meaningless to an AI scientist. But to political scientists the image appears to laud Ukrainians’ outsize courage in contrast to foreign leaders who have appeared to be afraid of Russian nuclear threats. The goal was to reinforce Ukrainian doubts about their European allies.

image of of two men, one seated
This manipulated image combines French president Emmanuel Macron with Ukranian governor Vitalii Kim. It requires the expertise of political scientists to interpret the creator’s pro-Russian meaning.
William Theisen et al.

Meme warfare

The shift to visual media in recent years brings a new type of data that researchers haven’t yet studied much in detail.

Looking at images can help researchers understand how adversaries frame each other and how this can lead to political conflict. By studying visual content, researchers can see how stories and ideas are spread, which helps us understand the psychological and social factors involved.

This is especially important for finding more advanced and subtle ways people are influenced. Projects like this also can contribute to improving early warning efforts and reduce the risks of violence and instability.The Conversation

Tim Weninger, Collegiate Proessor of Engineering, University of Notre Dame and Ernesto Verdeja, Associate Professor of Peace Studies and Global Politics, University of Notre Dame

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Colors are objective, according to two philosophers − even though the blue you see doesn’t match what I see

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theconversation.com – Elay Shech, Professor of Philosophy, Auburn University – 2025-04-25 07:55:00

What appear to be blue and green spirals are actually the same color.
Akiyoshi Kitaoka

Elay Shech, Auburn University and Michael Watkins, Auburn University

Is your green my green? Probably not. What appears as pure green to me will likely look a bit yellowish or blueish to you. This is because visual systems vary from person to person. Moreover, an object’s color may appear differently against different backgrounds or under different lighting.

These facts might naturally lead you to think that colors are subjective. That, unlike features such as length and temperature, colors are not objective features. Either nothing has a true color, or colors are relative to observers and their viewing conditions.

But perceptual variation has misled you. We are philosophers who study colors, objectivity and science, and we argue in our book “The Metaphysics of Colors” that colors are as objective as length and temperature.

Perceptual variation

There is a surprising amount of variation in how people perceive the world. If you offer a group of people a spectrum of color chips ranging from chartreuse to purple and asked them to pick the unique green chip – the chip with no yellow or blue in it – their choices would vary considerably. Indeed, there wouldn’t be a single chip that most observers would agree is unique green.

Generally, an object’s background can result in dramatic changes in how you perceive its colors. If you place a gray object against a lighter background, it will appear darker than if you place it against a darker background. This variation in perception is perhaps most striking when viewing an object under different lighting, where a red apple could look green or blue.

Of course, that you experience something differently does not prove that what is experienced is not objective. Water that feels cold to one person may not feel cold to another. And although we do not know who is feeling the water “correctly,” or whether that question even makes sense, we can know the temperature of the water and presume that this temperature is independent of your experience.

Similarly, that you can change the appearance of something’s color is not the same as changing its color. You can make an apple look green or blue, but that is not evidence that the apple is not red.

Apple under a gradient of red to blue light
Under different lighting conditions, objects take on different colors.
Gyozo Vaczi/iStock via Getty Images Plus

For comparison, the Moon appears larger when it’s on the horizon than when it appears near its zenith. But the size of the Moon has not changed, only its appearance. Hence, that the appearance of an object’s color or size varies is, by itself, no reason to think that its color and size are not objective features of the object. In other words, the properties of an object are independent of how they appear to you.

That said, given that there is so much variation in how objects appear, how do you determine what color something actually is? Is there a way to determine the color of something despite the many different experiences you might have of it?

Matching colors

Perhaps determining the color of something is to determine whether it is red or blue. But we suggest a different approach. Notice that squares that appear to be the same shade of pink against different backgrounds look different against the same background.

Green, purple and orange squares with smaller squares in shades of pink placed at their centers and at the bottom of the image
The smaller squares may appear to be the same color, but if you compare them with the strip of squares at the bottom, they’re actually different shades.
Shobdohin/Wikimedia Commons, CC BY-SA

It’s easy to assume that to prove colors are objective would require knowing which observers, lighting conditions and backgrounds are the best, or “normal.” But determining the right observers and viewing conditions is not required for determining the very specific color of an object, regardless of its name. And it is not required to determine whether two objects have the same color.

To determine whether two objects have the same color, an observer would need to view the objects side by side against the same background and under various lighting conditions. If you painted part of a room and find that you don’t have enough paint, for instance, finding a match might be very tricky. A color match requires that no observer under any lighting condition will see a difference between the new paint and the old.

YouTube video
Is the dress yellow and white or black and blue?

That two people can determine whether two objects have the same color even if they don’t agree on exactly what that color is – just as a pool of water can have a particular temperature without feeling the same to me and you – seems like compelling evidence to us that colors are objective features of our world.

Colors, science and indispensability

Everyday interactions with colors – such as matching paint samples, determining whether your shirt and pants clash, and even your ability to interpret works of art – are hard to explain if colors are not objective features of objects. But if you turn to science and look at the many ways that researchers think about colors, it becomes harder still.

For example, in the field of color science, scientific laws are used to explain how objects and light affect perception and the colors of other objects. Such laws, for instance, predict what happens when you mix colored pigments, when you view contrasting colors simultaneously or successively, and when you look at colored objects in various lighting conditions.

The philosophers Hilary Putnam and Willard van Orman Quine made famous what is known as the indispensability argument. The basic idea is that if something is indispensable to science, then it must be real and objective – otherwise, science wouldn’t work as well as it does.

For example, you may wonder whether unobservable entities such as electrons and electromagnetic fields really exist. But, so the argument goes, the best scientific explanations assume the existence of such entities and so they must exist. Similarly, because mathematics is indispensable to contemporary science, some philosophers argue that this means mathematical objects are objective and exist independently of a person’s mind.

Blue damselfish, seeming iridescent against a black background
The color of an animal can exert evolutionary pressure.
Paul Starosta/Stone via Getty Images

Likewise, we suggest that color plays an indispensable role in evolutionary biology. For example, researchers have argued that aposematism – the use of colors to signal a warning for predators – also benefits an animal’s ability to gather resources. Here, an animal’s coloration works directly to expand its food-gathering niche insofar as it informs potential predators that the animal is poisonous or venomous.

In fact, animals can exploit the fact that the same color pattern can be perceived differently by different perceivers. For instance, some damselfish have ultraviolet face patterns that help them be recognized by other members of their species and communicate with potential mates while remaining largely hidden to predators unable to perceive ultraviolet colors.

In sum, our ability to determine whether objects are colored the same or differently and the indispensable roles they play in science suggest that colors are as real and objective as length and temperature.The Conversation

Elay Shech, Professor of Philosophy, Auburn University and Michael Watkins, Professor of Philosophy, Auburn University

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‘Extraordinary claims require extraordinary evidence’ − an astronomer explains how much evidence scientists need to claim discoveries like extraterrestrial life

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theconversation.com – Chris Impey, University Distinguished Professor of Astronomy, University of Arizona – 2025-04-25 07:54:00

The universe is filled with countless galaxies, stars and planets. Astronomers may find life one day, but they will need extraordinary proof.
ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi

Chris Impey, University of Arizona

The detection of life beyond Earth would be one of the most profound discoveries in the history of science. The Milky Way galaxy alone hosts hundreds of millions of potentially habitable planets. Astronomers are using powerful space telescopes to look for molecular indicators of biology in the atmospheres of the most Earth-like of these planets.

But so far, no solid evidence of life has ever been found beyond the Earth. A paper published in April 2025 claimed to detect a signature of life in the atmosphere of the planet K2-18b. And while this discovery is intriguing, most astronomers – including the paper’s authors – aren’t ready to claim that it means extraterrestrial life exists. A detection of life would be a remarkable development.

The astronomer Carl Sagan used the phrase, “Extraordinary claims require extraordinary evidence,” in regard to searching for alien life. It conveys the idea that there should be a high bar for evidence to support a remarkable claim.

I’m an astronomer who has written a book about astrobiology. Over my career, I’ve seen some compelling scientific discoveries. But to reach this threshold of finding life beyond Earth, a result needs to fit several important criteria.

When is a result important and reliable?

There are three criteria for a scientific result to represent a true discovery and not be subject to uncertainty and doubt. How does the claim of life on K2-18b measure up?

First, the experiment needs to measure a meaningful and important quantity. Researchers observed K2-18b’s atmosphere with the James Webb Space Telescope and saw a spectral feature that they identified as dimethyl sulfide.

On Earth, dimethyl sulfide is associated with biology, in particular bacteria and plankton in the oceans. However, it can also arise by other means, so this single molecule is not conclusive proof of life.

Second, the detection needs to be strong. Every detector has some noise from the random motion of electrons. The signal should be strong enough to have a low probability of arising by chance from this noise.

The K2-18b detection has a significance of 3-sigma, which means it has a 0.3% probability of arising by chance.

That sounds low, but most scientists would consider that a weak detection. There are many molecules that could create a feature in the same spectral range.

The “gold standard” for scientific detection is 5-sigma, which means the probability of the finding happening by chance is less than 0.00006%. For example, physicists at CERN gathered data patiently for two years until they had a 5-sigma detection of the Higgs boson particle, leading to a Nobel Prize one year later in 2013.

YouTube video
The announcement of the discovery of the Higgs boson took decades from the time Peter Higgs first predicted the existence of the particle. Scientists, such as Joe Incandela shown here, waited until they’d reached that 5-sigma level to say, ‘I think we have it.’

Third, a result needs to be repeatable. Results are considered reliable when they’ve been repeated – ideally corroborated by other investigators or confirmed using a different instrument. For K2-18b, this might mean detecting other molecules that indicate biology, such as oxygen in the planet’s atmosphere. Without more and better data, most researchers are viewing the claim of life on K2-18b with skepticism.

Claims of life on Mars

In the past, some scientists have claimed to have found life much closer to home, on the planet Mars.

Over a century ago, retired Boston merchant turned astronomer Percival Lowell claimed that linear features he saw on the surface of Mars were canals, constructed by a dying civilization to transport water from the poles to the equator. Artificial waterways on Mars would certainly have been a major discovery, but this example failed the other two criteria: strong evidence and repeatability.

Lowell was misled by his visual observations, and he was engaging in wishful thinking. No other astronomers could confirm his findings.

An image of Mars in space
Mars, as taken by the OSIRIS instrument on the ESA Rosetta spacecraft during its February 2007 flyby of the planet and adjusted to show color.
ESA & MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA, CC BY-SA

In 1996, NASA held a press conference where a team of scientists presented evidence for biology in the Martian meteorite ALH 84001. Their evidence included an evocative image that seemed to show microfossils in the meteorite.

However, scientists have come up with explanations for the meteorite’s unusual features that do not involve biology. That extraordinary claim has dissipated.

More recently, astronomers detected low levels of methane in the atmosphere of Mars. Like dimethyl sulfide and oxygen, methane on Earth is made primarily – but not exclusively – by life. Different spacecraft and rovers on the Martian surface have returned conflicting results, where a detection with one spacecraft was not confirmed by another.

The low level and variability of methane on Mars is still a mystery. And in the absence of definitive evidence that this very low level of methane has a biological origin, nobody is claiming definitive evidence of life on Mars.

Claims of advanced civilizations

Detecting microbial life on Mars or an exoplanet would be dramatic, but the discovery of extraterrestrial civilizations would be truly spectacular.

The search for extraterrestrial intelligence, or SETI, has been underway for 75 years. No messages have ever been received, but in 1977 a radio telescope in Ohio detected a strong signal that lasted only for a minute.

This signal was so unusual that an astronomer working at the telescope wrote “Wow!” on the printout, giving the signal its name. Unfortunately, nothing like it has since been detected from that region of the sky, so the Wow! Signal fails the test of repeatability.

An illustration of a long, thin rock flying through space.
‘Oumuamua is the first object passing through the solar system that astronomers have identified as having interstellar origins.
European Southern Observatory/M. Kornmesser

In 2017, a rocky, cigar-shaped object called ‘Oumuamua was the first known interstellar object to visit the solar system. ‘Oumuamua’s strange shape and trajectory led Harvard astronomer Avi Loeb to argue that it was an alien artifact. However, the object has already left the solar system, so there’s no chance for astronomers to observe it again. And some researchers have gathered evidence suggesting that it’s just a comet.

While many scientists think we aren’t alone, given the enormous amount of habitable real estate beyond Earth, no detection has cleared the threshold enunciated by Carl Sagan.

Claims about the universe

These same criteria apply to research about the entire universe. One particular concern in cosmology is the fact that, unlike the case of planets, there is only one universe to study.

A cautionary tale comes from attempts to show that the universe went through a period of extremely rapid expansion a fraction of a second after the Big Bang. Cosmologists call this event inflation, and it is invoked to explain why the universe is now smooth and flat.

In 2014, astronomers claimed to have found evidence for inflation in a subtle signal from microwaves left over after the Big Bang. Within a year, however, the team retracted the result because the signal had a mundane explanation: They had confused dust in our galaxy with a signature of inflation.

On the other hand, the discovery of the universe’s acceleration shows the success of the scientific method. In 1929, astronomer Edwin Hubble found that the universe was expanding. Then, in 1998, evidence emerged that this cosmic expansion is accelerating. Physicists were startled by this result.

Two research groups used supernovae to separately trace the expansion. In a friendly rivalry, they used different sets of supernovae but got the same result. Independent corroboration increased their confidence that the universe was accelerating. They called the force behind this accelerating expansion dark energy and received a Nobel Prize in 2011 for its discovery.

On scales large and small, astronomers try to set a high bar of evidence before claiming a discovery.The Conversation

Chris Impey, University Distinguished Professor of Astronomy, University of Arizona

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