Category: Science

The US decline in butterflies

The natural world is quite remarkable!

This article was published in The Conversation last Thursday, the 6th March, 2025.

Where we live in rural Southern Oregon is glorious and photos of our locale have been published before. However, I wanted to share this article with you all.

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Butterflies declined by 22% in just 2 decades across the US – there are ways you can help save them

The endangered Karner blue butterfly has struggled with habitat loss. U.S. Fish and Wildlife Service

Eliza Grames, Binghamton University, State University of New York

If the joy of seeing butterflies seems increasingly rare these days, it isn’t your imagination.

From 2000 to 2020, the number of butterflies fell by 22% across the continental United States. That’s 1 in 5 butterflies lost. The findings are from an analysis just published in the journal Science by the U.S. Geological Survey’s Powell Center Status of Butterflies of the United States Working Group, which I am involved in.

We found declines in just about every region of the continental U.S. and across almost all butterfly species.

Overall, nearly one-third of the 342 butterfly species we were able to study declined by more than half. Twenty-two species fell by more than 90%. Only nine actually increased in numbers.

An orange butterfly with black webbing and spots sits on a purple flower.
West Coast lady butterflies range across the western U.S., but their numbers have dropped by 80% in two decades. Renee Las Vegas/Wikimedia Commons, CC BY

Some species’ numbers are dropping faster than others. The West Coast lady, a fairly widespread species across the western U.S., dropped by 80% in 20 years. Given everything we know about its biology, it should be doing fine – it has a wide range and feeds on a variety of plants. Yet, its numbers are absolutely tanking across its range.

Why care about butterflies?

Butterflies are beautiful. They inspire people, from art to literature and poetry. They deserve to exist simply for the sake of existing. They are also important for ecosystem function.

Butterflies are pollinators, picking up pollen on their legs and bodies as they feed on nectar from one flower and carrying it to the next. In their caterpillar stage, they also play an important role as herbivores, keeping plant growth in check.

A closeup of a caterpillar eating a leaf.
A pipevine swallowtail caterpillar munches on leaves at Brookside Gardens in Wheaton, Md. Herbivores help keep plant growth in check. Judy Gallagher/Wikimedia Commons, CC BY

Butterflies can also serve as an indicator species that can warn of threats and trends in other insects. Because humans are fond of butterflies, it’s easy to get volunteers to participate in surveys to count them.

The annual North American Butterfly Association Fourth of July Count is an example and one we used in the analysis. The same kind of nationwide monitoring by amateur naturalists doesn’t exist for less charismatic insects such as walking sticks.

What’s causing butterflies to decline?

Butterfly populations can decline for a number of reasons. Habitat loss, insecticides, rising temperatures and drying landscapes can all harm these fragile insects.

A study published in 2024 found that a change in insecticide use was a major factor in driving butterfly declines in the Midwest over 17 years. The authors, many of whom were also part of the current study, noted that the drop coincided with a shift to using seeds with prophylactic insecticides, rather than only spraying crops after an infestation.

The Southwest saw the greatest drops in butterfly abundance of any region. As that region heats up and dries out, the changing climate may be driving some of the butterfly decline there. Butterflies have a high surface-to-volume ratio – they don’t hold much moisture – so they can easily become desiccated in dry conditions. Drought can also harm the plants that butterflies rely on.

Only the Pacific Northwest didn’t lose butterfly population on average. This trend was largely driven by an irruptive species, meaning one with extremely high abundance in some years – the California tortoiseshell. When this species was excluded from the analyses, trends in the Pacific Northwest were similar to other regions.

A butterfly on a leaf
The California tortoiseshell butterfly can look like wood when its wings are closed, but they’re a soft orange on the other side. Walter Siegmund/Wikimedia Commons, CC BY-SA

When we looked at each species by its historical range, we found something else interesting.

Many species suffered their highest losses at the southern ends of their ranges, while the northern losses generally weren’t as severe. While we could not link drivers to trends directly, the reason for this pattern might involve climate change, or greater exposure to agriculture with insecticides in southern areas, or it may be a combination of many stressors.

There is hope for populations to recover

Some butterfly species can have multiple generations per year, and depending on the environmental conditions, the number of generations can vary between years.

This gives me a bit of hope when it comes to butterfly conservation. Because they have such short generation times, even small conservation steps can make a big difference and we can see populations bounce back.

The Karner blue is an example. It’s a small, endangered butterfly that depends on oak savannas and pine barren ecosystems. These habitats are uncommon and require management, especially prescribed burning, to maintain. With restoration efforts, one Karner blue population in the Albany Pine Bush Preserve in New York rebounded from a few hundred individuals in the early 1990s to thousands of butterflies.

Similar management and restoration efforts could help other rare and declining butterflies to recover.

What you can do to help butterflies recover

The magnitude and rate of biodiversity loss in the world right now can make one feel helpless. But while national and international efforts are needed to address the crisis, you can also take small actions that can have quick benefits, starting in your own backyard.

Butterflies love wildflowers, and planting native wildflowers can benefit many butterfly species. The Xerces Society for Invertebrate Conservation has guides recommending which native species are best to plant in which parts of the country. Letting grass grow can help, even if it’s just a strip of grass and wildflowers a couple of feet wide at the back of the yard.

Butterflies on wildflowers in a small garden.
A patch of wildflowers and grasses can become a butterfly garden, like this one in Townsend, Tenn. Chris Light, CC BY-SA

Supporting policies that benefit conservation can also help. In some states, insects aren’t considered wildlife, so state wildlife agencies have their hands tied when it comes to working on butterfly conservation. But those laws could be changed.

The federal Endangered Species Act can also help. The law mandates that the government maintain habitat for listed species. The U.S. Fish and Wildlife Service in December 2024 recommended listing the monarch butterfly as a threatened species. With the new study, we now have population trends for more than half of all U.S. butterfly species, including many that likely should be considered for listing.

With so many species needing help, it can be difficult to know where to start. But the new data can help concentrate conservation efforts on those species at the highest risk.

I believe this study should be a wake-up call about the need to better protect butterflies and other insects – “the little things that run the world.”

Eliza Grames, Assistant Professor of Biological Sciences, Binghamton University, State University of New York

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

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Thank you, Eliza, for promoting this article.

If only one person is inspired to make the changes Eliza recommends then republishing this article has been a success.

Why do we love dogs?

A fifteen-minute programme from the BBC.

I recently listened to this episode. It is part of a series on the BBC (Radio 4) that is entitled Why Do We Do That?

Hopefully you can also listen to the programme by using this link: https://www.bbc.co.uk/sounds/play/m0027v43

The information about this episode is published below.

Ella Al-Shamahi asks why do we love dogs? Dogs evolved from wolves but why did they choose us humans to be their best friends? They say dogs are a man’s best friend but all dogs, even chihuahuas are descended from wolves, the grey wolf, a majestic, fierce and incredibly dangerous species. How did this happen but more importantly, why did we start trusting wolves? And when did wolves turn into dogs? Dogs have been a part of our story for a long time. They are depicted in cave and rock art and dogs are a part of our story because of how useful they are. From the mundane everyday hunting and guarding to the epic stories of life saving dogs . But how did we get here? Oxford Professor Greger Lawson studies ancient dog DNA and thinks the evolution from wolves into dogs began when we both realised we could help each other.

Enjoy!

An article on decluttering

And it isn’t all that one might expect!

Jeannie and I are at opposite ends of the scale, so to speak. The older I get the more I want everything in the same place, primarily because I cannot remember where I previously put something.

Jeannie loves putting stuff anywhere because she can recall where it is!

So an article in The Conversation was fascinating.

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Decluttering can be stressful − a clinical psychologist explains how personal values can make it easier

Asking how discarding an item fits with a person’s goals can help them decide whether to keep it. MoMo Productions via Getty Images

Mary E. Dozier, Mississippi State University

I recently helped my mom sort through boxes she inherited when my grandparents passed away. One box was labeled – either ironically or genuinely – “toothpick holders and other treasures.” Inside were many keepsakes from moments now lost to history – although we found no toothpick holders.

My favorite of the items we sorted through was a solitary puzzle piece, an artifact reflecting my late grandmother’s penchant for hiding the final piece to a jigsaw puzzle just to swoop in at the last moment and finish it.

After several hours of reminiscing, my mom and I threw away 90% of what we had sorted.

“Why did I keep this?” is a question I hear frequently, both from my family and friends and from patients. I am a licensed clinical psychologist whose research focuses on the characterization, assessment and treatment of hoarding disorder, particularly for adults 60 years of age or older. As such, I spend a great deal of my time thinking about this question.

What drives the need to keep stuff?

Hoarding disorder is a psychiatric condition defined by urges to save items and difficulty discarding current possessions. For adults with “clinically severe” hoarding disorder, this leads to a level of household clutter that impairs daily functioning and can even create a fire hazard. In my professional experience, however, many adults struggle with clutter even if they do not meet the clinical criteria for hoarding disorder.

Holding on to things that have sentimental value or could be useful in the future is a natural part of growing older. For some people, though, this tendency to hold on to objects grows over time, to the point that they eventually do meet criteria for hoarding disorder. Age-related changes in executive function may help explain the increase in prevalence of hoarding disorder as we get older; increasing difficulty with decision-making in general also affects decisions around household clutter.

The traditional model behind hoarding disorder suggests that difficulty with discarding comes from distress during decision-making. However, my research shows that this may be less true of older adults.

A room full of piles of papers, stacked shelves and a tricycle.
Time to declutter. Kurt Whitman/Education Images via Getty Images

When I was a graduate student, I conducted a study in which we asked adults with hoarding disorder to spend 15 minutes making decisions about whether to keep or discard various items brought from their home. Participants could sort whatever items they wanted. Most chose to sort paper items such as old mail, cards or notes.

We found that age was associated with lower levels of distress during the task, such that participants who were older tended to feel less stressed when making the decision about what to keep and what to discard. We also found that many participants, particularly those who were older, actually reported positive emotions while sorting their items.

In new research publishing soon, my current team replicated this finding using a home-based version of the task. This suggests that fear of making the wrong decision isn’t a universal driver of our urge to save items.

In fact, a study my team published in August 2024 with adults over 50 with hoarding disorder suggests that altruism, a personality trait of wanting to help others, may explain why some people keep items that others might discard. My colleagues and I compared our participants’ personality profiles with that of adults in the general population of the same gender and age group. Compared with the general population, participants with hoarding disorder scored almost universally high on altruism.

Altruism also comes up frequently in my clinical work with older adults who struggle with clutter. People in our studies often tell me that they have held onto something out of a sense of responsibility, either for the item itself or to the environment.

“I need it to go to a good home” and “my grandmother gave this to me” are sentiments we commonly hear. Thus, people may keep things not out of fear of losing them but because saving them is consistent with their values. https://www.youtube.com/embed/JNVjPM1cIbg?wmode=transparent&start=0 Your values can help guide which possessions should stay in your life and which ones should go.

Leaning into values

In a 2024 study, my team demonstrated that taking a values-based approach to decluttering helps older adults to decrease household clutter and increases their positive affect, a state of mind characterized by feelings such as joy and contentment. Clinicians visited the homes of older adults with hoarding disorder for one hour per week for six weeks. At each visit, the clinicians used a technique called motivational interviewing to help participants talk through their decisions while they sorted household clutter.

We found that having participants start with identifying their values allowed them to maintain focus on their long-term goals. Too often, people focus on the immediate ability of an object to “spark joy” and forget to consider whether an object has greater meaning and purpose. Values are the abstract beliefs that we humans use to create our goals. Values are whatever drives us and can include family, faith or frivolity.

Because values are subjective, what people identify as important to keep is also subjective. For example, the dress I wore to my sister’s wedding reminded me of a wonderful day. However, when it no longer fit I gave it away because doing so was more consistent with my values of utility and helpfulness: I wanted the dress to go to someone who needed it and would use it. Someone who more strongly valued family and beauty might have prioritized keeping the dress because of the aesthetics and its link to a family event.

Additionally, we found that instead of challenging the reasons a person might have for keeping an item, it is helpful to instead focus on eliciting their reasons for discarding it and the goals they have for their home and their life.

Tips for sweeping away the old

My research on using motivational interviewing for decluttering and my observations from a current clinical trial on the approach point to some practical steps people can take to declutter their home. Although my work has been primarily with older adults, these tips should be helpful for people of all ages.

Start with writing out your values. Every object in your home should feel value-consistent for you. For example, if tradition and faith are important values for you, you might be more inclined to hold onto a cookbook that was made by the elders at your church and more able to let go of a cookbook you picked up on a whim at a bookstore.

If, instead, health and creativity are your core values, it might be more important to hold onto a cookbook of novel ways to sneak more vegetables into your diet.

Defining value-consistent goals for using your space can help to maintain motivation as you declutter. Are you clearing off your desk so you can work more efficiently? Making space on kitchen counters to bake cookies with your grandchildren?

Remember that sometimes your values will conflict. At those moments, it may help to reflect on whether keeping or discarding an object will bring you closer to your goals for the space.

Similarly, remember that values are subjective. If you are helping a loved one declutter, maintain a curious, nonjudgmental attitude. Where you might see a box filled with junk, your grandmother might see something filled with “toothpick holders and other treasures.”

For additional resources and information on hoarding disorder, visit the International OCD Foundation website.

Mary E. Dozier, Assistant Professor of Psychology, Mississippi State University

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

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Prof. Mary Dozier makes some powerful, and cogent, statements in this article. Especially that one’s values are subjective. Nevertheless, I think I should write out my values and see what they tell me.

Venus and Valentine’s Day

The role of the planet today!

From that post: Venus, named for the Roman goddess of love, reaches its greatest brilliancy on Valentine’s Day, February 14. Venus is currently blazing, low in the west after sunset, with Saturn below.

Wherever you are, try spotting Venus.

Our human language!

Namely a universal law.

I was attracted to an article that I read in The Conversation last a week ago.

It also taught me that we humans speak according to Zipf’s Law. I had not previously heard of this law.

So let me republish the article with the full permission of The Conversation.

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Whalesong patterns follow a universal law of human language, new research finds

A humpback whale mother and calf on the New Caledonian breeding grounds. Mark Quintin

Jenny Allen, Griffith University; Ellen Garland, University of St Andrews; Inbal Arnon, Hebrew University of Jerusalem, and Simon Kirby, University of Edinburgh

All known human languages display a surprising pattern: the most frequent word in a language is twice as frequent as the second most frequent, three times as frequent as the third, and so on. This is known as Zipf’s law.

Researchers have hunted for evidence of this pattern in communication among other species, but until now no other examples have been found.

In new research published today in Science, our team of experts in whale song, linguistics and developmental psychology analysed eight years’ of song recordings from humpback whales in New Caledonia. Led by Inbal Arnon from the Hebrew University, Ellen Garland from the University of St Andrews, and Simon Kirby from the University of Edinburgh, We used techniques inspired by the way human infants learn language to analyse humpback whale song.

We discovered that the same Zipfian pattern universally found across human languages also occurs in whale song. This complex signalling system, like human language, is culturally learned by each individual from others.

Learning like an infant

When infant humans are learning, they have to somehow discover where words start and end. Speech is continuous and does not come with gaps between words that they can use. So how do they break into language?

Thirty years of research has revealed that they do this by listening for sounds that are surprising in context: sounds within words are relatively predictable, but between words are relatively unpredictable. We analysed the whale song data using the same procedure.

Photo of a humpback whale breaching from the water.
A breaching humpback whale in New Caledonia. Operation Cetaces

Unexpectedly, using this technique revealed in whale song the same statistical properties that are found in all languages. It turns out both human language and whale song have statistically coherent parts.

In other words, they both contain recurring parts where the transitions between elements are more predictable within the part. Moreover, these recurring sub-sequences we detected follow the Zipfian frequency distribution found across all human languages, and not found before in other species.

Whale song recording (2017) Operation Cetaces 916 KB (download)

A chart showing the different frequencies of sound in whale song.
Close analysis of whale song revealed statistical structures similar to those found in human language. Operation Cetaces

How do the same statistical properties arise in two evolutionarily distant species that differ from one another in so many ways? We suggest we found these similarities because humans and whales share a learning mechanism: culture.

A cultural origin

Our findings raise an exciting question: why would such different systems in such incredibly distant species have common structures? We suggest the reason behind this is that both are culturally learned.

Cultural evolution inevitably leads to the emergence of properties that make learning easier. If a system is hard to learn, it will not survive to the next generation of learners.

There is growing evidence from experiments with humans that having statistically coherent parts, and having them follow a Zipfian distribution, makes learning easier. This suggests that learning and transmission play an important role in how these properties emerged in both human language and whale song.

So can we talk to whales now?

Finding parallel structures between whale song and human language may also lead to another question: can we talk to whales now? The short answer is no, not at all.

Our study does not examine the meaning behind whale song sequences. We have no idea what these segments might mean to the whales, if they mean anything at all.

Photo of whale backs and tails visible above the surface of the sea.
A competitive pod of humpback whales on the New Caledonian breeding grounds. Operation Cetaces

It might help to think about it like instrumental music, as music also contains similar structures. A melody can be learned, repeated, and spread – but that doesn’t give meaning to the musical notes in the same way that individual words have meaning.

Next up: birdsong

Our work also makes a bold prediction: we should find this Zipfian distribution wherever complex communication is transmitted culturally. Humans and whales are not the only species that do this.

We find what is known as “vocal production learning” in an unusual range of species across the animal kingdom. Song birds in particular may provide the best place to look as many bird species culturally learn their songs, and unlike in whales, we know a lot about precisely how birds learn song.

Equally, we expect not to find these statistical properties in the communication of species that don’t transmit complex communication by learning. This will help to reveal whether cultural evolution is the common driver of these properties between humans and whales.

Jenny Allen, Postdoctoral research associate, Griffith University; Ellen Garland, Royal Society University Research Fellow, School of Biology, University of St Andrews; Inbal Arnon, Professor of Psychology, Hebrew University of Jerusalem, and Simon Kirby, Professor of Language Evolution, University of Edinburgh

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

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The research scientists have led to a prediction: … we should find this Zipfian distribution wherever complex communication is transmitted culturally. Humans and whales are not the only species that do this.

Fascinating!

Nutrition advice

An article on educating us on avoiding misinformation.

Many articles on nutrition are full of errors and for the lay person there’s no easy way to understand what is correct, or not.

That’s why a recent article appealed to me and I thought it worth sharing.

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Nutrition advice is rife with misinformation − a medical education specialist explains how to tell valid health information from pseudoscience

If a health claim about a dietary intervention sounds too good to be true, it probably is. Mizina/iStock via Getty Images Plus

Aimee Pugh Bernard, University of Colorado Anschutz Medical Campus

The COVID-19 pandemic illuminated a vast landscape of misinformation about many topics, science and health chief among them.

Since then, information overload continues unabated, and many people are rightfully confused by an onslaught of conflicting health information. Even expert advice is often contradictory.

On top of that, people sometimes deliberately distort research findings to promote a certain agenda. For example, trisodium phosphate is a common food additive in cakes and cookies that is used to improve texture and prevent spoilage, but wellness influencers exploit the fact that a similarly named substance is used in paint and cleaning products to suggest it’s dangerous to your health.

Such claims can proliferate quickly, creating widespread misconceptions and undermining trust in legitimate scientific research and medical advice. Social media’s rise as a news and information source further fuels the spread of pseudoscientific views.

Misinformation is rampant in the realm of health and nutrition. Findings from nutrition research is rarely clear-cut because diet is just one of many behaviors and lifestyle factors affecting health, but the simplicity of using food and supplements as a cure-all is especially seductive.

I am an assistant professor specializing in medical education and science communication. I also train scientists and future health care professionals how to communicate their science to the general public.

In my view, countering the voices of social media influencers and health activists promoting pseudoscientific health claims requires leaning into the science of disease prevention. Extensive research has produced a body of evidence-based practices and public health measures that have consistently been shown to improve the health of millions of people around the world. Evaluating popular health claims against the yardstick of this work can help distinguish which ones are based on sound science.

A white person's hands holding a smartphone with screen showing a health app, next to a cup of coffee.
To parse pseudoscientific claims from sound advice about health and nutrition, it’s crucial to evaluate the information’s source. tadamichi/Getty Images

Navigating the terrain of tangled information

Conflicting information can be found on just about everything we eat and drink.

That’s because a food or beverage is rarely just good or bad. Instead, its health effects can depend on everything from the quantity a person consumes to their genetic makeup. Hundreds of scientific studies describe coffee’s health benefits and, on the flip side, its health risks. A bird’s-eye view can point in one direction or another, but news articles and social media posts often make claims based on a single study.

Things can get even more confusing with dietary supplements because people who promote them often make big claims about their health benefits. Take apple cider vinegar, for example – or ACV, if you’re in the know.

Apple cider vinegar has been touted as an all-natural remedy for a variety of ailments, including digestive issues, urinary health and weight management. Indeed, some studies have shown that it might help lower cholesterol, in addition to having other health benefits, but overall those studies have small sample sizes and are inconclusive.

Advocates of this substance often claim that one particular component of it – the cloudy sediment at the bottom of the bottle termed “the mother” – is especially beneficial because of the bacteria and yeast it contains. But there is no research that backs the claim that it offers any health benefits.

One good rule of thumb is that health hacks that promise quick fixes are almost always too good to be true. And even when supplements do offer some health benefits under specific circumstances, it’s important to remember that they are largely exempt from Food and Drug Administration regulations. That means the ingredients on their labels might contain more or less of the ingredients promised or other ingredients not listed, which can potentially cause harms such as liver toxicity.

It’s also important to keep in mind that the global dietary supplements industry is worth more than US$150 billion per year, so companies – and wellness influencers – selling supplements have a financial stake in convincing the public of their value.

Misinformation about nutrition is nothing new, but that doesn’t make it any less confusing.

How nutrition science gets twisted

There’s no doubt that good nutrition is fundamental for your health. Studies consistently show that a balanced diet containing a variety of essential nutrients can help prevent chronic diseases and promote overall well-being.

For instance, minerals such as calcium and iron support bone health and oxygen circulation in the blood, respectively. Proteins are essential for muscle repair and growth, and healthy fats, like those found in avocados and nuts, are vital for brain health.

However, pseudoscientific claims often twist such basic facts to promote the idea that specific diets or supplements can prevent or treat illness. For example, vitamin C is known to play a role in supporting the immune system and can help reduce the duration and severity of colds.

But despite assertions to the contrary, consuming large quantities of vitamin C does not prevent colds. In fact, the body needs only a certain amount of vitamin C to function properly, and any excess is simply excreted.

Companies sometimes claim their supplement is “scientifically proven” to cure illness or boost brain function, with no credible research to back it up.

Some companies overstate the benefits while underplaying the hazards.

For example, wellness influencers have promoted raw milk over pasteurized milk as a more natural and nutritious choice, but consuming it is risky. Unpasteurized milk can contain harmful bacteria that leads to gastrointestinal illness and, in some cases, much more serious and potentially life-threatening diseases such as avian influenza, or bird flu.

Such dietary myths aren’t harmless. Reliance on nutrition alone can lead to neglecting other critical aspects of health, such as regular medical checkups and lifesaving vaccinations.

The lure of dietary myths has led people with cancer to replace proven science-backed treatments, such as chemotherapy or radiation, with unproven and misleading nutrition programs.

How to spot less-than-solid science

Pseudoscience exploits your insecurities and emotions, taking advantage of your desire to live the healthiest life possible.

While the world around you may be uncertain and out of your control, you want to believe that at the very least, you have control over your own health. This is where the wellness industry steps in.

What makes pseudoscientific claims so confusing is that they use just enough scientific jargon to sound believable. Supplements or powders that claim to “boost immunity” often list ingredients such as adaptogens and superfoods. While these words sound real and convincing, they actually don’t mean anything in science. They are terms created by the wellness industry to sell products.

I’ve researched and written about reliable ways to distinguish science facts from false health claims. To stay alert and find credible information, I’d suggest you follow a few key steps.

First, check your emotions – strong emotional reactions, such as fear and anger, can be a red flag.

Next, check that the author has experience or expertise in the field of the topic. If they’re not an expert, they might not know what they are talking about. It’s always a good idea to make sure the source is reputable – ask yourself, would this source be trusted by scientists?

Finally, search for references that back up the information. If very little or nothing else exists in the science world to back up the claims, you may want to put your trust in a different source.

Following these steps will separate the facts from fake news and empower you to make evidence-based decisions.

Aimee Pugh Bernard, Assistant Professor of Immunology and Microbiology, University of Colorado Anschutz Medical Campus

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

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Sound advice for the majority of us!

The Edwin Hubble Great Debate

The following is more than fascinating; it is an example of how far science has reached; both figuratively and literally.

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One large Milky Way galaxy or many galaxies? 100 years ago, a young Edwin Hubble settled astronomy’s ‘Great Debate’

The Andromeda galaxy helped Edwin Hubble settle a great debate in astronomy. Stocktrek Images via Getty Images

Chris Impey, University of Arizona

A hundred years ago, astronomer Edwin Hubble dramatically expanded the size of the known universe. At a meeting of the American Astronomical Society in January 1925, a paper read by one of his colleagues on his behalf reported that the Andromeda nebula, also called M31, was nearly a million light years away – too remote to be a part of the Milky Way.

Hubble’s work opened the door to the study of the universe beyond our galaxy. In the century since Hubble’s pioneering work, astronomers like me have learned that the universe is vast and contains trillions of galaxies.

Nature of the nebulae

In 1610, astronomer Galileo Galilei used the newly invented telescope to show that the Milky Way was composed of a huge number of faint stars. For the next 300 years, astronomers assumed that the Milky Way was the entire universe.

As astronomers scanned the night sky with larger telescopes, they were intrigued by fuzzy patches of light called nebulae. Toward the end of the 18th century, astronomer William Herschel used star counts to map out the Milky Way. He cataloged a thousand new nebulae and clusters of stars. He believed that the nebulae were objects within the Milky Way.

Charles Messier also produced a catalog of over 100 prominent nebulae in 1781. Messier was interested in comets, so his list was a set of fuzzy objects that might be mistaken for comets. He intended for comet hunters to avoid them since they did not move across the sky.

As more data piled up, 19th century astronomers started to see that the nebulae were a mixed bag. Some were gaseous, star-forming regions, such as the Orion nebula, or M42 – the 42nd object in Messier’s catalog – while others were star clusters such as the Pleiades, or M45.

A third category – nebulae with spiral structure – particularly intrigued astronomers. The Andromeda nebula, M31, was a prominent example. It’s visible to the naked eye from a dark site.

The Andromeda galaxy, then known as the Andromeda nebula, is a bright spot in the sky that intrigued early astronomers.

Astronomers as far back as the mid-18th century had speculated that some nebulae might be remote systems of stars or “island universes,” but there was no data to support this hypothesis. Island universes referred to the idea that there could be enormous stellar systems outside the Milky Way – but astronomers now just call these systems galaxies.

In 1920, astronomers Harlow Shapley and Heber Curtis held a Great Debate. Shapley argued that the spiral nebulae were small and in the Milky Way, while Curtis took a more radical position that they were independent galaxies, extremely large and distant.

At the time, the debate was inconclusive. Astronomers now know that galaxies are isolated systems of stars, much smaller than the space between them.

Hubble makes his mark

Edwin Hubble was young and ambitious. At the of age 30, he arrived at Mount Wilson Observatory in Southern California just in time to use the new Hooker 100-inch telescope, at the time the largest in the world.

A black and white photo of a man looking through the lens of a large telescope.
Edwin Hubble uses the telescope at the Mount Wilson Observatory. Hulton Archives via Getty Images

He began taking photographic plates of the spiral nebulae. These glass plates recorded images of the night sky using a light-sensitive emulsion covering their surface. The telescope’s size let it make images of very faint objects, and its high-quality mirror allowed it to distinguish individual stars in some of the nebulae.

Estimating distances in astronomy is challenging. Think of how hard it is to estimate the distance of someone pointing a flashlight at you on a dark night. Galaxies come in a very wide range of sizes and masses. Measuring a galaxy’s brightness or apparent size is not a good guide to its distance.

Hubble leveraged a discovery made by Henrietta Swan Leavitt 10 years earlier. She worked at the Harvard College Observatory as a “human computer,” laboriously measuring the positions and brightness of thousands of stars on photographic plates.

She was particularly interested in Cepheid variables, which are stars whose brightness pulses regularly, so they get brighter and dimmer with a particular period. She found a relationship between their variation period, or pulse, and their intrinsic brightness or luminosity.

Once you measure a Cepheid’s period, you can calculate its distance from how bright it appears using the inverse square law. The more distant the star is, the fainter it appears.

Hubble worked hard, taking images of spiral nebulae every clear night and looking for the telltale variations of Cepheid variables. By the end of 1924, he had found 12 Cepheids in M31. He calculated M31’s distance as a prodigious 900,000 light years away, though he underestimated its true distance – about 2.5 million light years – by not realizing there were two different types of Cepheid variables.

His measurements marked the end of the Great Debate about the Milky Way’s size and the nature of the nebulae. Hubble wrote about his discovery to Harlow Shapley, who had argued that the Milky Way encompassed the entire universe.

“Here is the letter that destroyed my universe,” Shapley remarked.

Always eager for publicity, Hubble leaked his discovery to The New York Times five weeks before a colleague presented his paper at the astronomers’ annual meeting in Washington, D.C.

An expanding universe of galaxies

But Hubble wasn’t done. His second major discovery also transformed astronomers’ understanding of the universe. As he dispersed the light from dozens of galaxies into a spectrum, which recorded the amount of light at each wavelength, he noticed that the light was always shifted to longer or redder wavelengths.

Light from the galaxy passes through a prism or reflects off a diffraction grating in a telescope, which captures the intensity of light from blue to red.

Astronomers call a shift to longer wavelengths a redshift.

It seemed that these redshifted galaxies were all moving away from the Milky Way.

Hubble’s results suggested the farther away a galaxy was, the faster it was moving away from Earth. Hubble got the lion’s share of the credit for this discovery, but Lowell Observatory astronomer Vesto Slipher, who noticed the same phenomenon but didn’t publish his data, also anticipated that result.

Hubble referred to galaxies having recession velocities, or speeds of moving away from the Earth, but he never figured out that they were moving away from Earth because the universe is getting bigger.

Belgian cosmologist and Catholic priest Georges Lemaitre made that connection by realizing that the theory of general relativity described an expanding universe. He recognized that space expanding in between the galaxies could cause the redshifts, making it seem like they were moving farther away from each other and from Earth.

Lemaitre was the first to argue that the expansion must have begun during the big bang.

The Hubble telescope, which looks like a metal cylinder, floating in space.
Edwin Hubble is the namesake for NASA’s Hubble Space Telescope, which has spent decades observing faraway galaxies. NASA via AP

NASA named its flagship space observatory after Hubble, and it has been used to study galaxies for 35 years. Astronomers routinely observe galaxies that are thousands of times fainter and more distant than galaxies observed in the 1920s. The James Webb Space Telescope has pushed the envelope even farther.

The current record holder is a galaxy a staggering 34 billion light years away, seen just 200 million years after the big bang, when the universe was 20 times smaller than it is now. Edwin Hubble would be amazed to see such progress.

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

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

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So wonderful that in this modern era we can read articles from distinguished scientists in the comfort of our own homes.

The Full Moon

The first one of 2025.

The following photograph was taken by yours truly on the 12th January at 17.19 Oregon time.

It was a stunning combination of the moon and the hills and the evening sky.

Picture Parade Four Hundred and Fifty-Nine

A few more photographs of the swollen Bummer Creek.

Firstly, the photo I shared on January 2nd.

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This last one shows how the water, which was up to the bottom of the tree, had the force to hollow out the ground beneath that fine tree!

It is a New Year!

And I want to return to publishing posts!

My last post was about an accident that I had on the 17th November, last.

Jean is now back home; she came home on Friday, 13th December. However, every day we have a caregiver at home for part of the time. Jean is getting slowly better. I would estimate that at about one percent a day.

I am unsure as to the pattern of my posts. Whether I should go back to scheduling posts three times a week or publish posts on an ad-hoc basis. That will become clearer over the next few weeks.

I am going to start with publishing posts on an ad-hoc basis.

Meanwhile here in Merlin we have had loads of rain.

Bummer Creek

This is the creek that flows across the lower part of the property.