Big Think's Top 25 +1 Videos

Mama, Don't Let Your Babies Grow Up To Deny Evolution

If adults want to deny evolution, sure. That’s fine. Whatever. But those adults better not make their kids follow in step because we as society need them to be better. Bill Nye, everyone's favorite Science Guy, explains the importance of promoting evolution education for America's future voters and lawmakers.

My Man, Sir Isaac Newton

Are you at least 26 years-old? If so, you are older than Isaac Newton was when he invented calculus... on a dare! (If you're younger than 26, better hurry up.) Big Think expert and overall cool guy Neil deGrasse Tyson explains why Newton is the greatest physicist who ever and likely will ever live.

Will Mankind Destroy Itself?

Theoretical physicist Michio Kaku sees two major trends today. One eventually leads to a multicultural, scientific, tolerant society that will expand beyond Earth in the name of human progress. The other trend leads to fundamentalism, monoculturalism, and -- eventually -- civilizational ruin. Whichever of these two trends wins out will determine the fate of mankind. No pressure, everyone.

Ricky Gervais on the Principles of Comedy

Comedy isn't just about making people laugh, says actor Ricky Gervais. It's about making people think. And while different forms of comedy require different approaches, the crux of any good performance will always be rhythm.

Reading the Bible (Or the Koran, Or the Torah) Will Make You an Atheist

Author and magician Penn Jillette was asked to leave his Christian youth group by a pastor who told his parents: "He's no longer learning about the Bible from me. He is now converting everyone in the class to atheism." The reason? Jillette did his homework and was turned off by the hostilities of the text. It can be intimidating to come out as an atheist, especially in a religious community. Jillette found that having "out" atheist role models helped him feel unalone.

Henry Rollins: The One Decision that Changed My Life Forever

Punk legend Henry Rollins describes the biggest turning point in his life: the moment he decided to leave his job as manager of a Häagen-Dazs store and eventually become the lead singer of Black Flag. It was the courage to take a risk, plus a whole lot of luck, that got Rollins to where he is today.

5 Programming Languages Everyone Should Know

Java is "heavyweight, verbose, and everyone loves to hate it," but programmer Larry Wall still thinks you should know it. In this video, he offers suggestions for people interested in learning languages, as well as suggestions for those significantly less invested in computer programming.

The Importance of Unbelief

If you assume there’s no afterlife, Stephen Fry says, you’ll likely have a fuller, more interesting "now" life. The actor and comedian details the positive influence philosophers have had on his life, as well as his journey of understanding both what he believes and why he believes it.

Why be happy when you could be interesting?

We don't really want what we think we desire, says philosopher Slavoj Žižek.

James Gleick on the Common Character Traits of Geniuses

This video is part of a series on female genius, in proud collaboration with 92Y's 7 Days of Genius Festival.

The personalities of Isaac Newton and Richard Feynman were, on one level, extremely different. Biographer and former New York Times reporter James Gleick says Newton was argumentative, had few friends, and likely died a virgin. Feynman, on the other hand, loved dancing and going to parties, and had many friends in the scientific community. But in regards to their working habits, both men were solitary and had the ability to concentrate with a sort of intensity that is hard for mortals to grasp. At bottom, Gleick says geniuses tend to have a yearning for solitude which, though fruitful for their professional work, made the task of daily living more burdensome.

The Importance of Doing Useless Things

From poetry and ballet to mathematics and being clever, life is laden with frivolous pursuits that hold no bearing on our ability to survive. Yet, insists Richard Dawkins, if it weren’t for the development of these impractical activities, we wouldn’t be here.

Why monogamy is ridiculous

Dan Savage: the idea that one instance of infidelity should ruin a relationship is a new—and misguided—notion.

Dan Harris: Hack Your Brain's Default Mode With Meditation

Dan Harris explains the neuroscience behind meditation, but reminds us that the ancient practice isn't magic and likely won't send one floating into the cosmic ooze. He predicts that the exercise will soon become regularly scheduled maintenance, as commonplace as brushing your teeth or eating your veggies. Harris, an ABC News correspondent, was turned on to mediation after a live, on-air panic attack. His latest book is 10% Happier: How I Tamed the Voice in My Head, Reduced Stress Without Losing My Edge, and Found Self-Help That Actually Works--A True Story.

How Intellectuals Betrayed the Poor

For 40 years academics were duped into idolizing the idea of unfettered markets, says Cornel West, and now our society is paying a terrible price.

Why Some Races Outperform Others

A psychologist explains the latest research into education disparity.

Why It's So Hard for Scientists to Believe in God

Some scientists see religion as a threat to the scientific method that should be resisted. But faith "is really asking a different set of questions," says Collins.

Why Facebook Isn't Free

Internet pioneer Jaron Lanier argues that free technologies like Facebook come with a hidden and heavy cost – the livelihoods of their consumers.

How to Tell if You’re a Writer

For John Irving, the need for a daily ration of solitude was his strongest "pre-writing" moment as a child.

Your Behavior Creates Your Gender

Nobody is born one gender or the other, says the philosopher. "We act and walk and speak and talk in ways that consolidate an impression of being a man or being a woman."

Are You a Liberal Snob? Take The Quiz

Charles Mrray designed this quiz to have a salutary effect on bringing to people’s attention the degree to which they live in a bubble that seals them off from an awful lot of their fellow American citizens.

Why You Should Watch Filth

John Waters defends the creation and consumption of obscene films, and recommends some of his personal favorites.

What Are You Worth? Getting Past Status Anxiety.

Writer Alain De Botton says that status anxiety is more pernicious and destructive than most of us can imagine, and recommends getting out of the game altogether.

Sheila Heen on the Psychology of Happiness and Feedback

Sheila Heen, a Partner at Triad Consulting Group and a lecturer on Law at Harvard Law School, explains the psychology behind feedback and criticism. Heen is co-author of "Thanks for the Feedback: The Science and Art of Receiving Feedback Well."

Are You a Psychopath? Take the Test.

Psychologist Kevin Dutton presents the classic psychological test known as "the trolley problem" with a variation. Take the test and measure you response on the psychopathic spectrum.

Here's How to Catch a Liar, If You Really Want To

It’s very complex as to whether or not we really want to catch a liar. We think we do. What if we find out that both of our presidential candidates are lying? Then what do we do? I’m not saying they are; I never comment on anyone in office or running for office. Only after they’re out that they’re fair game. . . . Clinton said, "I didn’t have sex with that woman" and then gave her name. "That woman" is putting her at a distance from himself.

Why I Came Out at Age 81

As a teenager in the '40s, James Randi "would have gotten stoned" for being gay. But when he outed himself to the world in 2010, the reaction was "wonderful."

More playlists
  • An Italian architecture firm has proposed a sustainable city for Mexico.
  • The plans call for a 100 percent self-sufficient metropolis, with renewable energy, Venetian canals, and endless green space.
  • This design is one of many "smart city" proposals as of late that point to a new form of urbanism.

Imagine a city that manages to combine nature and technology harmoniously, a self-sustaining metropolis where green space is punctuated by modern buildings and the bustle of city life.

Such a city is currently in works, as Milan-based architecture firm Stefano Boeri Architetti has just announced plans for a smart "forest city" near Cancun, Mexico that will be able to provide all of its food and energy.


An aerial view of the proposed city. Notice the surrounding green space and extensive canal system.

Image source: Stefano Boeri Architetti

According to the firm's press release, the city will cover 557 hectares, 400 of which will be green spaces containing 7,500,000 plants. Designed for 130,000 people to live and work there, it will feature a wide variety of housing types to accommodate the needs of its residents.

The economy of the city will be circular, with all of its food, water, and energy needs being self-generated. The designs also include a grand research center so that the city can host university departments, conferences, and curious scholars of all ages.

The city even has plans to improve the way we interact with our data. The architects told Dezeen that "Big data management is used to improve the governance of the city, hence, the life of its citizens. Sensors are distributed within the building fabric: they collect and share relevant information, which is then centrally analyzed and turned into suggestions in support of everyday life. For example, by mapping on an app the expected outdoor comfort experience within certain areas of the city."

This data will be handled with "full respect of the privacy of the citizens."

If all goes according to plan, the city will be built on an area currently used as a sand quarry for hotels that is tentatively scheduled to become a shopping center.

Can it really be self-sustaining?

Artist's impression of the fresh water canals.

Image source: Stefano Boeri Architetti

The city is designed to fully sustain itself through an ingenious system of energy production and water desalination. A ring of solar panels will surround the city, generating enough power for all of the inhabitants. Water will be pulled from the Caribbean and desalinized using a solar tower. This water would be used to irrigate crops through a system of navigable canals.

Transportation will be handled by an entirely electric public "Mobility in Chain" transit system. Cars will all be left outside of the city.

What carbon emissions there are will be captured by the endless plants. The firm notes, with evident pride, that "thanks to the new public parks and private gardens, thanks to the green roofs and to the green facades, the areas actually occupied will be given back by nature through a perfect balance between the amount of green areas and building footprint. The Smart Forest City will absorb 116.000 tons of carbon dioxide with 5.800 tons of CO2 stocked per year."

While it currently only exists on paper, the visionaries who have dreamed this plan into existence hope the city can be an example for the world and a testing place for ideas on sustainable urbanism. It will join the ranks of several other smart cities that have been proposed as ways to improve our existence, make the world more sustainable, and move beyond the limitations of our current urban planning paradigms.

  • Universities are places where there academic freedom thrives. Such open exchange of ideas creates an environments conducive to civil discourse — dialog with one another with the goal of reaching the truth.
  • Philanthropists should, ideally, provide resources to institutions that promote scholarly work. The reason for this is because such work benefits society at large.
  • When you engage with people who don't agree with you, you learn how to understand viewpoints from different angles. The learning that takes place at these moments is often transformative, mind-expanding.
  • Ayahuasca is a psychedelic brew that's been used by Amazonian tribes for centuries.
  • Recent research suggests that ayahuasca might help reduce depression. The new study examined whether those effects might extend to suicidality.
  • The results were mixed, but it seems ayahuasca shows some potential as a suicide intervention.

The psychedelic brew ayahuasca might show promise in the treatment of suicidality, the results of a new study suggest.

Ayahuasca — commonly made from the leaves of the Psychotria viridis shrub and stalks of the Banisteriopsis caapi vine — has been used for centuries by Amazonian tribes as a spiritual medicine. It can cause intense, hours-long psychedelic experiences that have been described in countless ways, from life-changing to psychologically-distressing. In recent years, "ayahuasca retreats" in countries such as Peru and Brazil have become popular among Westerners seeking spiritual healing.

More recently, scientists have begun exploring the potential therapeutic benefits of ayahuasca in the clinical setting, a development that comes as governments are relaxing regulations on experiments involving psychedelic drugs, like ketamine and psilocybin.

In 2018, for instance, a team of psychologists conducted the first randomized, placebo-controlled clinical trial of ayahuasca. The results, published in the journal Psychological Medicine, indicated that ayahuasca could, in fact, be effective in alleviating hard-to-treat depression.

In the new study, published in Frontiers in Pharmacology on November 19, the researchers wanted to test whether the drug had similar effects on reducing suicidality — one's tendency to think about, show risk of, or plan suicide.

"Suicide is one of the leading causes of death, accounting for nearly 1,000,000 deaths each year," study author Richard Zeifman, a Ph.D. student in Clinical Psychology at Ryerson University, told PsyPost. Zeifman added:

"Current interventions for suicidality have important limitations, which means there is a need for developing and identifying novel interventions for suicidality. Given this need, as well as research indicating that ayahuasca shows promise as an intervention for various mental health concerns (e.g., depression), we were interested in exploring whether the positive therapeutic effects of ayahuasca extended to suicidality."

The team recruited 29 participants — all of whom had major depressive disorder (MDD) and had never tried psychedelic drugs — to ingest either ayahuasca or a placebo in a dimly lit room as they listened to a predetermined playlist of music. Then, suicidality among the participants was measured by a psychiatrist for a week after the ayahuasca session.

The results were mixed. Compared to the placebo group, the participants who took ayahuasca showed less suicidality at all points during the week after the session. However, the differences weren't quite strong enough to be statistically significant. One explanation for the ambiguous results, besides the possibility that ayahuasca might not reduce suicidality, is that the team's statistical analysis wasn't able to detect significant effects — possibly because the sample size was too small.

In any case, the researchers said the findings suggest that ayahuasca shows "promise as a fast-acting and innovative intervention for suicidality."

"Furthermore, within the ayahuasca group, we found large effect sizes for decreases in suicidality at all time points," the researchers wrote. "These findings are in line with past research on the impact of psilocybin on suicidality and longitudinal research indicating that lifetime use of psychedelics is associated with reduced levels of suicidality and decreased risk of becoming suicidal."

The authors stressed that their results are preliminary, and that further research is needed before ayahuasca can be considered as a standardized suicide intervention.

It's worth noting the potential dangers of ayahuasca: Although anecdotal evidence suggests that ayahuasca might help people such as veterans reduce depression and symptoms of PTSD, there have also been cases of people committing suicide or experiencing mental health problems after taking ayahuasca.

A 'thirst for wholeness'

But it's possible these problems stem from people using the drug irresponsibly, as Rev. Dr. Jessica Rochester, founder of Céu do Montreal, a Canadian church that uses ayahuasca in spiritual ceremonies, told the Montreal Gazette.

"What has been happening is something called ayahuasca tourism. Unfortunately, with the world of the internet and people posting things saying, 'I went here once and healed my whole life,' (ayahuasca) has been sensationalized."

"On the other side, there have been tragic accidents where people either met death or caused harm. Our condolences go out to the individuals, families and friends for their losses, which would have been preventable if people would have taken simple precautions."

Rochester said ayahuasca improved her life.

"A lot of my experiences contributed to my understanding of myself, and of reality," she said. "I was simply following what my heart called me into. I can't say I was looking for anything in particular, but I like what Carl Jung wrote to Bill Wilson about a 'thirst for wholeness.'

"It's what's driving Western civilization, and is the cornerstone of a lot of my early academic work and my work as a health and wellness counsellor, which I have been for years."

  • In "Cautionary Tales," economist Tim Harford explores why humans are so susceptible to con artists.
  • In the podcast's first episode, Harford uses a famed oil tanker spill to highlight how important it is to admit mistakes.
  • Future episodes compare the Oracle at Delphi with computer algorithms and a famous awards show messing up the envelopes.

Humans are susceptible to cons. We're even more likely to fall for larger-than-life personalities. This isn't me writing about the vague "other humans" out there, the ones that you and I (wink, wink) know exist but would never fall victim to. As economist and journalist, Tim Harford — the author of the bestselling book, The Undercover Economist recently told me, the con is "baked into" human nature.

Yet, as he explores in his excellent new podcast, "Cautionary Tales," we can learn from past mistakes. Take a few deep breaths, count to 10, make better decisions — decisions, he points out on his podcast, that can save lives. We can better educate ourselves to learn about things we think we know about but actually do not.

Part of Pushkin Industries, the company co-founded by Malcolm Gladwell and Jacob Weisberg, Harford joins Gladwell and Michael Lewis for a series that explores the meaning behind both historical and modern-day events. In the debut episode, Harford discusses the tragic Torrey Canyon reef crash in 1967, which dumped 120,000 short tons of crude oil into the waters near Cornwall. The captain's inability to change course is, in itself, a lesson about the value of admitting mistakes and putting our new-found knowledge into action.

In episode two, we hear the story of Wilhelm Voigt, a Berlin native that isn't a captain but played one in society, an incredible story that shows us the depths of our beliefs in powerful con men. Harford discusses the political consequences of such cons during our interview. I'm sure you can guess where that conversation ends up.

As with Revisionist History and Against the Rules, "Cautionary Tales" is a welcome addition to podcasting. Humans might fall for cons and be unwilling to own up to mistakes, but we're also animals with a deep love for storytelling. Harford excels at that medium, both in writing and narration. The podcast is a pleasure to listen to and, bonus, you might just learn something along the way.

A powerful way to unleash your natural creativity | Tim Harford

Derek: Your new podcast is on Pushkin, which has this vibe of radio from a century ago. It's not just people talking; there's music, sound effects, and acting involved. Why did you go that route with "Cautionary Tales"?

Tim: One of the things that quickly became clear as I was looking at the stories that I wanted to tell is that very often these are stories where we don't have tape. We don't have a lot of archival footage. Very often there was nobody there when it happened. The journalist showed up afterwards; in some cases—there's one story that's two and a half thousand years old—we don't have tapes.

What do you do? Well, you can do the usual thing, which is to put an expert in an arm chair and ask him or her to explain what happened. We wanted to do something different. These little historical reenactments are like fresh herbs and spices throughout the podcast. These little scenes include a very different way to access a story that you wouldn't have another way to tell.

Derek: Your show is billed as "the science behind what happens." There has long been a replication problem in science. I know you mostly deal with the social sciences, but what was your training in science and why did you choose what you chose when approaching a topic?

Tim: It's a very good point because of the replication crisis—I think crisis is the right word. One of the issues is people looking for the perfectly counter-intuitive results, the thing that's just weird enough to be surprising and yet not so weird that you completely dismiss it. There's a lot of psychology published that has been filtered through that medium. I'm coming at it from a slightly different angle.

Rather than the coolest new study that might surprise you, I'm saying, "This thing happened, this oil tanker hit the rocks or this economist was the most famous economist in the world and he went bankrupt or they gave the Oscar to the wrong movie." Start with that story and then say, "What is it that social scientists can tell us about that story? What are the explanations?" Very often you find there's more than one explanation. There's usually no single cause. Then the question is: What explains it? What do the people who have thought hard about this sort of thing make of these accidents?

I talk about Milgram's experiments, but I try to remind people that a lot of the experiments that he did were not reported. These are very famous electric shock and obedience experiments. I'm trying to pick that apart and think about what modern psychologists now make of those experiments of what they think those experiments really tell us—to not to be uncritical in the way that I think about these studies.

Derek: I've read that study in many different contexts. The way you frame it about being an example not of obedience, but of a willingness to admit our mistakes, is really important. Why are we so unwilling to admit when we're wrong?

Tim: That's a big question. In some cases it's a social thing. In politics, for example, you don't want to admit that you're wrong because you're conceding ground to the other side and you don't want to lose faith socially. You don't want to lose political advantage. In other cases, you personally have committed so much to a particular viewpoint that it becomes extraordinarily painful to face up to the error.

This is the old idea of cognitive dissonance, which I explore in an episode about John Maynard Keynes and Irving Fisher, two great economists and their forecasting. Long story short, both are geniuses; both get really into stock market investing. One goes bankrupt; one dies a millionaire. What explains the differences?

One of them is willing to admit he made a mistake and one is not. Irving Fisher is more exposed. He's more publicly committed. He's going to lose face socially. But he's also too deep in debt to admit "I'm getting this wrong, I need to change direction." It's more painful to the sense of who he is, which the guy who doesn't make mistakes.

There's a third problem, which is something I emphasized in Adapt: We didn't know we made a mistake. No one ever tells you that you made a mistake; no one ever gives you the feedback. That's a very common problem.

Derek: Your podcast is supposed to help us learn from our mistakes. How do you help people actually learn what is in their best interest? Is that even possible?

Tim: This is something I explore in the final episode, which is about what happens when we just hand over our process to an authority figure or to a computer algorithm. What happens when we just let our GPS tell us where to go? One of the really interesting groups of studies that I talk about in that episode is what happens when you are forced to stop and think. These studies explore something called the illusion of explanatory depth.

In the initial study, they say, "How well do you reckon that you know how a flush laboratory works on a scale of zero to seven?" People will say, "Oh yeah, maybe six." Then the researchers say, "That's really interesting. Here's a pen and paper. Just explain to us in detail how it works." People get really stuck because they realize they don't know how it works. It was all a bit vague. They weren't lying to the researchers; they were lying to themselves. They felt that they understood this everyday object and they didn't.

The next study asked the same questions but about politics. It's by a different group of researchers. They said, "Tell us how a cap and trade system works. Tell us how the US will apply unilateral sanctions on Iran. How does that actually work?" People often feel they know pretty well what these policies are. Then again, when you ask them to explain, not to advocate, don't tell me whether it's a good idea, just tell me what it is. Again, people go, "Ah hmm. Uh hmm. I thought I knew but I don't know."

What's fascinating is that people's views about politics become more moderate. They think, quite reasonably, "Maybe my previous view that I was willing to die in a ditch to defend cap and trade or to prevent cap and trade, maybe that view that I thought was super important, maybe I shouldn't hold that view so strongly anymore given that I didn't really understand what it is that I'm talking about."

Not in every Cautionary Tale, but it comes up again and again, is that if you can calm down and slow down, whatever terrible thing happened wouldn't have happened if somebody had been able to count to 10 and think about what was going on.

Derek: When I was listening to episode two, I was reminded of a story growing up. There was a sporting goods chain called Herman's. Two men walked in, went to the back of the store, and grabbed a canoe. They put it over their heads and walked out of the store. It took 20 minutes for anyone to realize that they stole it.

Tim: Because they just walked right out as if they had bought it.

Derek: You say the judge, at the end of "The Captain of Köpenick," goes down and shakes Voigt's hand even though he admitted his crime and was a con man. What do we learn from that?

Tim: We're tremendously subjected to appearances. I wish I had a silver bullet for that one, some pill you could take that would cure us of that. I talk about the fact that just being tall is tremendously advantageous if you're running for political office.

Tim Harford: What Prison Camps Can Teach You About the Economy

Derek: I'm six-three, so I appreciated that.

Tim: Yeah, me too. As far as presidents go, that's not that tall. When you look at it, it's like they're picking a basketball team. It's a myth that the taller candidate always wins, but it definitely seems to be an advantage. The example of appearances matching the eye that I just can't get my head around is the adverts where the guy says, "I'm not a doctor, I just play one on TV," as though it's the most natural thing in the world. And it clearly works! That that advert ran for a long time is absolutely astonishing.

Even this particular con man, Wilhelm Voigt, would not have said, "I'm not actually a military captain. I'm just wearing the uniform." Of course, I can't help but think of a certain president who's most famous for playing a successful business man on TV. He's famous for acting as a businessman. It makes a huge difference to how we perceive the world.

Derek: Do we ever get over that? Is that something we can teach out of ourselves?

Tim: I have never seen a piece of research that says there is a cure for that. That is why, for example, blind recruitment processes and blind audition processes are so powerful. Claudia Goldin and Cecilia Rouse studied what happens when the great American orchestras switched to blind auditions. They thought they were doing it to prevent discrimination against particular students who have powerful teachers; they didn't only want the "in crowd" to be recruited. They put up screens so you wouldn't know who was playing. Surprise, surprise, suddenly a load of women who previously wouldn't thought to be good enough were being recruited.

It's not enough to just tell people, "You shouldn't discriminate against women. Hey, don't be too impressed by uniforms. Treat people who don't look attractive the same way as you treat attractive people." You can tell people that, but I'm not sure it makes a great deal of difference. We can, again, slow down, have a think, and ask ourselves, "Am I overweighting this person's appearance? Am I favoring this person for president because they they look presidential rather than this other person who doesn't seem to look like what I imagined the president to look like?"

I don't think there is an easy cure for that. That's heavily baked in human nature. It's simpler with con artists. If you can slow them down and slow yourself down enough, you can usually spot the con. With a more subtle influence, like who we want to run our companies and who we want to run our country, appearances are always going to matter.


Stay in touch with Derek on Twitter and Facebook.

  • A NASA study reveals new dangers to the human body in space.
  • The absence of gravity caused changes in people's blood flows.
  • Some had blood going in reverse while others developed clots.

Humanity's expansion into space is both a hopeful and risky endeavor. A new study from NASA identified a new danger – low gravity can make blood flow stop and actually go in reverse in some astronauts.

The condition particularly applied to people's upper bodies. What its implications are for long-term health is still being studied but it appears to join the other space afflictions that we already know about, which include loss of mass and increased brittleness of bones.

The study arrived at this conclusion by looking at data from 11 astronauts (nine men, two women) who spent an average of six months each on the International Space Station.

Ultrasound assessments revealed that by around the 50th day into the mission, seven members of the crew had blood in their internal jugular vein stop flowing or even start going in reverse. This vein is a major blood vessel going down the side of the neck. Its function is to collect blood from the brain, neck and face.

One of the astronauts also developed a clot in the vein while still in flight, while another was found to have a partial clot upon coming back to Earth.

Having your blood flow in reverse definitely doesn't sound appealing and the discovery raises additional alarms about the dangers of long-term space travel.

Michael Stenger, the study's senior author, also a manager of the Cardiovascular and Vision Laboratory at NASA's Johnson Space Center in Houston, called the finding "unexpected".

"We did not expect to see stasis and reverse flow," told Stenger to NBC News. "That is very abnormal. On Earth, you would immediately suspect a massive blockage or a tumor or something like that."

Stenger attributes the issue to the absence of gravity, pointing to years worth of observations of physiological changes in astronauts.

"This is why some astronauts get puffy faces, because there's no gravity to pull down those fluids circulating in the upper body," explained Stenger. "You'll sometimes also see veins popping out in the neck, or in the head — which you can see with bald astronauts, in particular."

He pointed to stopped blood flow as probably the most worrisome aspect of the discovery, saying that this results in dangerous blood clots.

99.99% of species go extinct. What is humanity’s future?

While the research is concerning, it can be seen more as an opportunity to anticipate the risks and develop new treatments, say the scientists.

Check out the study "Assessment of Jugular Venous Blood Flow Stasis and Thrombosis During Spaceflight" In the medical journal Jama Network Open (from the American Medical Association).