Jean-Luc Margot, University of California, Los Angeles

On Nov. 9, 2024, the world will mark Carl Sagan’s 90th birthday – but sadly without Sagan, who died in 1996 at the age of 62.

Most people remember him as the co-creator and host of the 1980 “Cosmos” television series, watched worldwide by hundreds of millions of people. Others read “Contact,” his best-selling science fiction novel, or “The Dragons of Eden,” his Pulitzer Prize-winning nonfiction book. Millions more saw him popularize astronomy on “The Tonight Show.”

What most people don’t know about Sagan, and what has been somewhat obscured by his fame, is the far-reaching impact of his science, which resonates to this day. Sagan was an unequaled science communicator, astute advocate and prolific writer. But he was also an outstanding scientist.

Sagan propelled science forward in at least three important ways. He produced notable results and insights described in over 600 scientific papers. He enabled new scientific disciplines to flourish. And he inspired multiple generations of scientists. As a planetary astronomer, I believe such a combination of talents and accomplishments is rare and may occur only once in my lifetime.

Scientific accomplishments

Very little was known in the 1960s about Venus. Sagan investigated how the greenhouse effect in its carbon dioxide atmosphere might explain the unbearably high temperature on Venus – approximately 870 degrees Fahrenheit (465 degrees Celsius). His research remains a cautionary tale about the dangers of fossil fuel emissions here on Earth.

Sagan proposed a compelling explanation for seasonal changes in the brightness of Mars, which had been incorrectly attributed to vegetation or volcanic activity. Wind-blown dust was responsible for the mysterious variations, he explained.

Sagan and his students studied how changes to the reflectivity of Earth’s surface and atmosphere affect our climate. They considered how the detonation of nuclear bombs could inject so much soot into the atmosphere that it would lead to a yearslong period of substantial cooling, a phenomenon known as nuclear winter.

With unusual breadth in astronomy, physics, chemistry and biology, Sagan pushed forward the nascent discipline of astrobiology – the study of life in the universe.
Together with the research scientist Bishun Khare at Cornell University, Sagan conducted pioneering laboratory experiments and showed that certain ingredients of prebiotic chemistry, called tholins, and certain building blocks of life, known as amino acids, form naturally in laboratory environments that mimic planetary settings.

He also modeled the delivery of prebiotic molecules to the early Earth by asteroids and comets, and he was deeply engaged in the biological experiments onboard the Mars Viking landers. Sagan also speculated about the possibility of balloon-shaped organisms floating in the atmospheres of Venus and Jupiter.

His passion for finding life elsewhere extended far beyond the solar system. He was a champion of the search for extraterrestrial intelligence, also known as SETI. He helped fund and participated in a systematic search for extraterrestrial radio beacons by scanning 70% of the sky with the physicist and electrical engineer Paul Horowitz.

He proposed and co-designed the plaques and the “Golden Records” now affixed to humanity’s most distant ambassadors, the Pioneer and Voyager spacecrafts. It is unlikely that extraterrestrials will ever find these artifacts, but Sagan wanted people to contemplate the possibility of communication with other civilizations.

Advocacy

Sagan’s scientific output repeatedly led him to become an eloquent advocate on issues of societal and scientific significance. He testified before Congress about the dangers of climate change. He was an antinuclear activist and spoke out against the Strategic Defense Initiative, also known as “Star Wars.” He urged collaborations and a joint space mission with the Soviet Union, in an attempt to improve U.S.-Soviet relations. He spoke directly with members of Congress about the search for extraterrestrial intelligence and organized a petition signed by dozens of prominent scientists urging support for the search.

But perhaps his most important gift to society was his promotion of truth-seeking and critical thinking. He encouraged people to muster the humility and discipline to confront their most cherished beliefs – and to rely on evidence to obtain a more accurate view of the world. His most cited book, “The Demon-Haunted World: Science as a Candle in the Dark,” is a precious resource for anyone trying to navigate this age of disinformation.

Impact

A scientist’s impact can sometimes be gauged by the number of times their scholarly work is cited by other scientists. According to Sagan’s Google Scholar page, his work continues to accumulate more than 1,000 citations per year.

Indeed, his current citation rate exceeds that of many members of the National Academy of Sciences, who are “elected by their peers for outstanding contributions to research,” according to the academy’s website, and is “one of the highest honors a scientist can receive.”

Sagan was nominated for election into the academy during the 1991-1992 cycle, but his nomination was challenged at the annual meeting; more than one-third of the members voted to keep him out, which doomed his admission. An observer at that meeting wrote to Sagan, “It is the worst of human frailties that keeps you out: jealousy.” This belief was affirmed by others in attendance. In my opinion, the academy’s failure to admit Sagan remains an enduring stain on the organization.

No amount of jealousy can diminish Sagan’s profound and wide-ranging legacy. In addition to his scientific accomplishments, Sagan has inspired generations of scientists and brought an appreciation of science to countless nonscientists. He has demonstrated what is possible in the realms of science, communication and advocacy. Those accomplishments required truth-seeking, hard work and self-improvement. On the 90th anniversary of Sagan’s birth, a renewed commitment to these values would honor his memory.

Jean-Luc Margot, Professor of Earth, Planetary, and Space Sciences, University of California, Los Angeles

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

Zackary Okun Dunivin, University of California, Davis

There’s a certain allure to the notion that some of the world’s brightest stars burn out at the age of 27. The so-called 27 Club has captivated the public imagination for half a century. Its members include legendary musicians Jimi Hendrix, Janis Joplin, Jim Morrison, Kurt Cobain and Amy Winehouse. The idea is as seductive as it is tragic: a convergence of talent, fame and untimely death at a singular age.

But is there any truth to this phenomenon, or is it merely a story we tell ourselves and each other about fame and youth?

In our newly published research, my colleague Patrick Kaminski and I explore why the 27 Club persists in culture. We didn’t set out to debunk the myth. After all, there is no reason to think that 27 is an especially dangerous age beyond superstition.

Rather, we wanted to explore the 27 Club to understand how such a myth gains traction and affects people’s perception of reality.

Is the 27 Club real?

The origin of the 27 Club dates back to the early 1970s, following the deaths of Brian Jones, Jimi Hendrix, Janis Joplin and Jim Morrison – all at age 27, within a span of two years.

This uncanny coincidence left its mark on collective memory. It wasn’t just their age. It was the common thread of musical genius, countercultural influence and the tragic allure of lives cut short by a cocktail of fame, drug use and the struggle of being human. The narrative is not just compelling but almost mystical in its synchronicity.

Analyzing data from 344,156 notable deceased individuals listed on Wikipedia, we found that while there’s no increased risk of dying at 27, those who do die at that age receive significantly more public attention. Using Wikipedia page views as a proxy for fame, our study revealed that the legacies of these 27-year-olds are amplified, garnering more visibility than those who die at adjacent ages.

This increased visibility has a strange effect: People are more likely to encounter those who died at 27 than other young ages, even if they are not aware of the myth. This in turn creates the appearance of greater risk of mortality at 27. The myth of the 27 Club is a self-fulfilling prophecy: It became “real” because we believed it.

Why is the 27 Club a thing?

We believe this phenomenon can be understood through three interrelated concepts: path dependence, stigmergy and memetic reification.

Path dependence refers to how random events can set a precedent that influences future outcomes. The initial cluster of high-profile deaths at age 27 was statistically improbable – we estimate that one in 100,000 timelines would have four such famous deaths at age 27 – but it established a narrative pathway that has persisted and shaped collective reality.

Stigmergy describes how traces of an event or action left in the environment can indirectly coordinate future events or actions. In the digital age, platforms such as Wikipedia serve as repositories of collective memory. The existence of a dedicated 27 Club page, with links to its members’ pages, increases the visibility of those who die at 27. This creates a feedback loop: The more we click, the more prominent these figures become, and the more the myth is reinforced.

Finally, what we call memetic reification captures how beliefs can shape reality. We draw from a sociological concept called the Thomas theorem, which states that if you “define a situation as real, they are real in their consequences.” The 27 Club myth has tangible effects on cultural memory and fame. By imbuing significance into the age of 27, society elevates the legacies of those who die at that age, making the myth materially consequential.

Why do myths endure?

Why do such myths endure? At their core, myths are not about factual accuracy but about narratives that resonate with people. They thrive on mystery, tragedy and the human penchant for finding patterns even in randomness. The story of the 27 Club is poetic, encapsulating the fleeting nature of genius and the fragility of life. It’s a story that begs to be told and retold, regardless of its veracity.

This isn’t an isolated phenomenon. Cultural patterns often arise from chance events that, through collective commitment and storytelling, become embedded in our understanding of the world.

Consider the evolution of language – why do we call a dog a “dog”? There is nothing doggy about the word. Philosopher Ludwig Wittgenstein observed that nearly all symbols are arbitrary. Some countries drive on the left side of the road while others on the right. While the choice to adopt left- or right-side traffic is influenced by neighboring countries or car producers, ultimately these followed from an arbitrary resolution to the need to pick one side or the other. These conventions began as random occurrences that, over time, became standardized and meaningful through social reinforcement.

The 27 Club serves as a lens through which you can examine the power of mythmaking in shaping perceptions of history and reality. It highlights how collective beliefs can have real-world consequences, influencing who becomes immortalized in cultural memory. It’s a testament to the complex interplay between chance events, storytelling and the mechanisms by which myths are perpetuated.

Though we may appear to dispel the myth of the 27 Club, let’s not abandon the story. We’re myth trusters, not myth busters. In unraveling the myth, we’re acknowledging the profound ways in which narratives influence our collective consciousness. By understanding the processes behind myth formation, we can better appreciate the richness of culture and the stories people choose to tell.

Zackary Okun Dunivin, Postdoctoral Fellow in Communication, University of California, Davis

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

Benjamin Roulston, Clarkson University

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.

Why does Jupiter look like it has a surface – even though it doesn’t have one? – Sejal, age 7, Bangalore, India

The planet Jupiter has no solid ground – no surface, like the grass or dirt you tread here on Earth. There’s nothing to walk on, and no place to land a spaceship.

But how can that be? If Jupiter doesn’t have a surface, what does it have? How can it hold together?

Even as a professor of physics who studies all kinds of unusual phenomena, I realize the concept of a world without a surface is difficult to fathom. Yet much about Jupiter remains a mystery, even as NASA’s robotic probe Juno begins its ninth year orbiting this strange planet.

First, some facts

Jupiter, the fifth planet from the Sun, is between Mars and Saturn. It’s the largest planet in the solar system, big enough for more than 1,000 Earths to fit inside, with room to spare.

While the four inner planets of the solar system – Mercury, Venus, Earth and Mars – are all made of solid, rocky material, Jupiter is a gas giant with a composition similar to the Sun; it’s a roiling, stormy, wildly turbulent ball of gas. Some places on Jupiter have winds of more than 400 mph (about 640 kilometers per hour), about three times faster than a Category 5 hurricane on Earth.

Searching for solid ground

Start from the top of Earth’s atmosphere, go down about 60 miles (roughly 100 kilometers), and the air pressure continuously increases. Ultimately you hit Earth’s surface, either land or water.

Compare that with Jupiter: Start near the top of its mostly hydrogen and helium atmosphere, and like on Earth, the pressure increases the deeper you go. But on Jupiter, the pressure is immense.

As the layers of gas above you push down more and more, it’s like being at the bottom of the ocean – but instead of water, you’re surrounded by gas. The pressure becomes so intense that the human body would implode; you would be squashed.

Go down 1,000 miles (1,600 kilometers), and the hot, dense gas begins to behave strangely. Eventually, the gas turns into a form of liquid hydrogen, creating what can be thought of as the largest ocean in the solar system, albeit an ocean without water.

Go down another 20,000 miles (about 32,000 kilometers), and the hydrogen becomes more like flowing liquid metal, a material so exotic that only recently, and with great difficulty, have scientists reproduced it in the laboratory. The atoms in this liquid metallic hydrogen are squeezed so tightly that its electrons are free to roam.

Keep in mind that these layer transitions are gradual, not abrupt; the transition from normal hydrogen gas to liquid hydrogen and then to metallic hydrogen happens slowly and smoothly. At no point is there a sharp boundary, solid material or surface.

Scary to the core

Ultimately, you’d reach the core of Jupiter. This is the central region of Jupiter’s interior, and not to be confused with a surface.

Scientists are still debating the exact nature of the core’s material. The most favored model: It’s not solid, like rock, but more like a hot, dense and possibly metallic mixture of liquid and solid.

The pressure at Jupiter’s core is so immense that it would be like 100 million Earth atmospheres pressing down on you – or two Empire State buildings on top of each square inch of your body.

But pressure wouldn’t be your only problem. A spacecraft trying to reach Jupiter’s core would be melted by the extreme heat – 35,000 degrees Fahrenheit (20,000 degrees Celsius). That’s three times hotter than the surface of the Sun.

Jupiter helps Earth

Jupiter is a weird and forbidding place. But if Jupiter weren’t around, it’s possible human beings might not exist.

That’s because Jupiter acts as a shield for the inner planets of the solar system, including Earth. With its massive gravitational pull, Jupiter has altered the orbit of asteroids and comets for billions of years.

Without Jupiter’s intervention, some of that space debris could have crashed into Earth; if one had been a cataclysmic collision, it could have caused an extinction-level event. Just look at what happened to the dinosaurs.

Maybe Jupiter gave an assist to our existence, but the planet itself is extraordinarily inhospitable to life – at least, life as we know it.

The same is not the case with a Jupiter moon, Europa, perhaps our best chance to find life elsewhere in the solar system.

NASA’s Europa Clipper, a robotic probe launching in October 2024, is scheduled to do about 50 fly-bys over that moon to study its enormous underground ocean.

Could something be living in Europa’s water? Scientists won’t know for a while. Because of Jupiter’s distance from Earth, the probe won’t arrive until April 2030.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Benjamin Roulston, Assistant Professor of Physics, Clarkson University

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