Can humans travel through wormholes in space?
Two new studies examine ways we could engineer human wormhole travel.
Marcelo Gleiser is a professor of natural philosophy, physics, and astronomy at Dartmouth College. He is a Fellow of the American Physical Society, a recipient of the Presidential Faculty Fellows Award from the White House and NSF, and was awarded the 2019 Templeton Prize. Gleiser has authored five books and is the co-founder of 13.8, where he writes about science and culture with physicist Adam Frank.
- Sci-fi movies and books love wormholes—how else can we hope to travel through interstellar distances?
- But wormholes are notoriously unstable; it's hard to keep them open or make them big enough.
- Two new papers offer some hope in solving both of these issues, but at a high price.
Imagine if we could cut paths through the vastness of space to make a network of tunnels linking distant stars somewhat like subway stations here on Earth? The tunnels are what physicists call wormholes, strange funnel-like folds in the very fabric of spacetime that would be—if they exist—major shortcuts for interstellar travel. You can visualize it in two dimensions like this: Take a piece of paper and bend it in the middle so that it makes a U shape. If an imaginary flat little bug wants to go from one side to the other, it needs to slide along the paper. Or, if there were a bridge between the two sides of the paper the bug could go straight between them, a much shorter path. Since we live in three dimensions, the entrances to the wormholes would be more like spheres than holes, connected by a four-dimensional "tube." It's much easier to write the equations than to visualize this! Amazingly, because the theory of general relativity links space and time into a four-dimensional spacetime, wormholes could, in principle, connect distant points in space, or in time, or both.
A wormhole connecting two points in space.
Credit: TDHster via Adobe Stock
The idea of wormholes is not new. Its origins reach back to 1935 (and even earlier), when Albert Einstein and Nathan Rosen published a paper constructing what became known as an Einstein-Rosen bridge. (The name 'wormhole' came up later, in a 1957 paper by Charles Misner and John Wheeler, Wheeler also being the one who coined the term 'black hole.') Basically, an Einstein-Rosen bridge is a connection between two distant points of the universe or possibly even different universes through a tunnel that goes into a black hole. Exciting as the possibility is, the throats of such bridges are notoriously unstable and any object with mass that ventures through it would cause it to collapse upon itself almost immediately, closing the connection. To force the wormholes to stay open, one would need to add a kind of exotic matter that has both negative energy density and pressure—not something that is known in the universe. (Interestingly, negative pressure is not as crazy as it seems; dark energy, the fuel that is currently accelerating the cosmic expansion, does it exactly because it has negative pressure. But negative energy density is a whole other story.)
If wormholes exist, if they have wide mouths, and if they can be kept open (three big but not impossible ifs) then it's conceivable that we could travel through them to faraway spots in the universe. Arthur C. Clarke used them in "2001: A Space Odyssey", where the alien intelligences had constructed a network of intersecting tunnels they used as we use the subway. Carl Sagan used them in "Contact" so that humans could confirm the existence of intelligent ETs. "Interstellar" uses them so that we can try to find another home for our species.
If wormholes exist, if they have wide mouths, and if they can be kept open (three big but not impossible ifs) then it's conceivable that we could travel through them to faraway spots in the universe.
Two recent papers try to get around some of these issues. Jose Luis Blázquez-Salcedo, Christian Knoll, and Eugen Radu use normal matter with electric charge to stabilize the wormhole, but the resulting throat is still of submicroscopic width, so not useful for human travel. It is also hard to justify net electric charges in black hole solutions as they tend to get neutralized by surrounding matter, similar to how we get shocked with static electricity in dry weather. Juan Maldacena and Alexey Milekhin's paper is titled 'Humanly Traversable Wormholes', thus raising the stakes right off the bat. However, they are open to admitting that "in this paper, we revisit the question [of humanly traversable wormholes] and we engage in some 'science fiction.'" The first ingredient is the existence of some kind of matter (the "dark sector") that only interacts with normal matter (stars, us, frogs) through gravity. Another point is that to support the passage of human-size travelers, the model needs to exist in five dimensions, thus one extra space dimension. When all is set up, the wormhole connects two black holes with a magnetic field running through it. And the whole thing needs to spin to keep it stable, and completely isolated from particles that may fall into it compromising its design. Oh yes, and extremely low temperature as well, even better at absolute zero, an unattainable limit in practice.
Maldacena and Milekhins' paper is an amazing tour through the power of speculative theoretical physics. They are the first to admit that the object they construct is very implausible and have no idea how it could be formed in nature. In their defense, pushing the limits (or beyond the limits) of understanding is what we need to expand the frontiers of knowledge. For those who dream of humanly traversable wormholes, let's hope that more realistic solutions would become viable in the future, even if not the near future. Or maybe aliens that have built them will tell us how.
New research from the University of Granada found that stress could help determine sex.
Stress in the modern world is generally viewed as a hindrance to a healthy life.
Indeed, excess stress is associated with numerous problems, including cardiovascular disease, high blood pressure, insomnia, depression, obesity, and other conditions. While the physiological mechanisms associated with stress can be beneficial, as Kelly McGonigal points out in The Upside of Stress, the modern wellness industry is built on the foundation of stress relief.
The effects of stress on pregnant mothers is another longstanding area of research. For example, what potential negative effects do elevated levels of cortisol, epinephrine, and norepinephrine have on fetal development?
A new study, published in the Journal of Developmental Origins of Health and Disease, investigated a very specific aspect of stress on fetuses: does it affect sex? Their findings reveal that women with elevated stress are twice as likely to give birth to a girl.
For this research, the University of Granada scientists recorded the stress levels of 108 women before, during, and after conception. By testing cortisol concentration in their hair and subjecting the women to a variety of psychological tests, the researchers discovered that stress indeed influences sex. Specifically, stress made women twice as likely to deliver a baby girl.
The team points out that their research is consistent with other research that used saliva to show that stress resulted in a decreased likelihood of delivering a boy.
Maria Isabel Peralta RamírezPhoto courtesy of University of Granada
Lead author María Isabel Peralta Ramírez, a researcher at the UGR's Department of Personality, Evaluation and Psychological Treatment, says that prior research focused on stress levels leading up to and after birth. She was interested in stress's impact leading up to conception. She says:
"Specifically, our research group has shown in numerous publications how psychological stress in the mother generates a greater number of psychopathological symptoms during pregnancy: postpartum depression, a greater likelihood of assisted delivery, an increase in the time taken for lactation to commence (lactogenesis), or inferior neurodevelopment of the baby six months after birth."
While no conclusive evidence has been rendered, the research team believes that activation of the mother's endogenous stress system during conception sets the concentration of sex hormones that will be carried throughout development. As the team writes, "there is evidence that testosterone functions as a mechanism when determining the baby's sex, since the greater the prenatal stress levels, the higher the levels of female testosterone." Levels of paternal stress were not factored into this research.
Previous studies show that sperm carrying an X chromosome are better equipped to reach the egg under adverse conditions than sperm carrying the Y chromosome. Y fetuses also mature slowly and are more likely to produce complications than X fetuses. Peralta also noted that there might be more aborted male fetuses during times of early maternal stress, which would favor more girls being born under such circumstances.
In the future, Peralta and her team say an investigation into aborted fetuses should be undertaken. Right now, the research was limited to a small sample size that did not factor in a number of elements. Still, the team concludes, "the research presented here is pioneering to the extent that it links prenatal stress to the sex of newborns."
Stay in touch with Derek on Twitter and Facebook. His most recent book is "Hero's Dose: The Case For Psychedelics in Ritual and Therapy."
The world's 10 most affected countries are spending up to 59% of their GDP on the effects of violence.
- Conflict and violence cost the world more than $14 trillion a year.
- That's the equivalent of $5 a day for every person on the planet.
- Research shows that peace brings prosperity, lower inflation and more jobs.
- Just a 2% reduction in conflict would free up as much money as the global aid budget.
- Report urges governments to improve peacefulness, especially amid COVID-19.
What is the price of peace?
Or put another way, how much better off would we all be in a world where armed conflict was avoided?
To give some context, 689 million people - more than 9% of the world's population - live on less than $1.90 a day, according to World Bank figures, underscoring the potential impact peace-building activities could have.
Just over 10% of global GDP is being spent on containing, preventing and dealing with the consequences of violence. As well as the 1.4 million violent deaths each year, conflict holds back economic development, causes instability, widens inequality and erodes human capital.
Putting a price tag on peace and violence helps us see the disproportionately high amounts spent on creating and containing violent acts compared to what is spent on building resilient, productive, and peaceful societies.
—Steve Killelea, founder and executive chairman, Institute for Economics & Peace (IEP)
The cost of violence
In a report titled "The Economic Value of Peace 2021", the IEP says that for every death from violent conflict, 40 times as many people are injured. The world's 10 most affected countries are spending up to 59% of their GDP on the effects of violence.
Grounds for hope
But the picture is not all bleak. The economic impact of violence fell for the second year in a row in 2019, as parts of the world became more peaceful.
The global cost dropped by $64 billion between 2018 and 2019, even though it was still $1.2 trillion higher than in 2012.
In five regions of the world the costs increased in 2019. The biggest jump was in Central America and the Caribbean, where a rising homicide rate pushed the cost up 8.3%.
Syria, with its ongoing civil war, suffered the greatest economic impact with almost 60% of its GDP lost to conflict in 2019. That was followed by Afghanistan (50%) and South Sudan (46%).
The report makes a direct link between peace and prosperity. It says that, since 2000, countries that have become more peaceful have averaged higher GDP growth than those which have become more violent.
"This differential is significant and represents a GDP per capita that is 30% larger when compounded over a 20-year period," the report says adding that peaceful countries also have substantially lower inflation and unemployment.
"Small improvements in peace can have substantial economic benefits," it adds. "For example, a 2% reduction in the global impact of violence is roughly equivalent to all overseas development aid in 2019."
Equally, the total value of foreign direct investment globally only offsets 10% of the economic impact of violence. Authoritarian regimes lost on average 11% of GDP to the costs of violence while in democracies the cost was just 4% of GDP.
And the gap has widened over time, with democracies reducing the cost of violence by almost 16% since 2007 while in authoritarian countries it has risen by 27% over the same period.
The report uses 18 economic indicators to evaluate the cost of violence. The top three are military spending (which was $5.9 trillion globally in 2019), the cost of internal security which makes up over a third of the total at $4.9 trillion and homicide.
Peace brings prosperity
The formula also contains a multiplier effect because as peace increases, money spent containing violence can instead be used on more productive activities which drive growth and generate higher monetary and social returns.
"Substantial economic improvements are linked to improvements in peace," says the report. "Therefore, government policies should be directed to improving peacefulness, especially in a COVID-19 environment where economic activity has been subdued."
The IEP says what it terms "positive peace" is even more beneficial than "negative peace" which is simply the absence of violence or the fear of violence. Positive peace involves fostering the attitudes, institutions & structures that create and sustain peaceful societies.
The foundations of a positively peaceful society, it says, are: a well functioning government, sound business environment, acceptance of the rights of others, good relations with neighbours, free flow of information, high levels of human capital, low levels of corruption and equitable distribution of resources.
The World Economic Forum's report Mobilizing the Private Sector in Peace and Reconciliation urged companies large and small to recognise their potential to work for peace quoting the former Goldman Sachs chair, the late Peter Sutherland, who said: "Business thrives where society thrives."
The lush biodiversity of South America's rainforests is rooted in one of the most cataclysmic events that ever struck Earth.
- One especially mysterious thing about the asteroid impact, which killed the dinosaurs, is how it transformed Earth's tropical rainforests.
- A recent study analyzed ancient fossils collected in modern-day Colombia to determine how tropical rainforests changed after the bolide impact.
- The results highlight how nature is able to recover from cataclysmic events, though it may take millions of years.
About 66 million years ago, a massive asteroid slammed into present-day Chicxulub, Mexico, triggering the extinction of dinosaurs. Scientists estimate the impact killed 75 percent of life on Earth. But what's remained more mysterious is how the event shaped the future of plant life, specifically tropical rainforests.
A new study published in Science explores how the so-called bolide impact at the end of the Cretaceous period paved the way for the evolution of our modern rainforests, the most diverse terrestrial ecosystems on Earth.
For the study, researchers analyzed thousands of samples of fossil pollen, leaves, and spores collected from various sites across Colombia. The researchers analyzed the samples to determine which types of plants were dominant, the diversity of plant life, and how insects interacted with plants.
All samples dated back to the Cretaceous-Paleogene boundary, some 70 million to 56 million years ago. Back then, the region's climate was mostly humid and hot, as it is today. However, the composition and structure of forests were quite different before the impact, according to the study results.
Tropical jungle with river and sun beam and foggy in the gardenSASITHORN via Adobe Stock
For one, the region's rainforests used to have a roughly equal mix of angiosperms (shrubs and flowering trees) and plants like conifers and ferns. The rainforests also had a more open canopy structure, which allowed more light to reach the forest floor and meant that plants faced less competition for light.
What changed after the asteroid hit? The results suggest the impact and its aftermath led to a 45 percent decrease in plant diversity, a loss from which the region took about 6 million years to recover. But different plants came to replace the old ones, with an increasing proportion of flowering plants sprouting up over the millennia.
"A single historical accident changed the ecological and evolutionary trajectory of tropical rainforests," Carlos Jaramillo, study author and paleopalynologist at the Smithsonian Tropical Research Institute in Panama City, told Science News. "The forests that we have today are really the by-product of what happened 66 million years ago."
Today's rainforests are significantly more biodiverse than they were 66 million years ago. One potential reason is that the more densely packed canopy structure of the post-impact era increased competition among plants, "leading to the vertical complexity seen in modern rainforests," the researchers wrote.
The extinction of long-necked, leaf-eating dinosaurs probably helped maintain this closed-canopy structure. Also boosting biodiversity was ash from the impact, which effectively fertilized the soil by adding more phosphorus. This likely benefited flowering plants over the conifers and ferns of the pre-impact era.
In addition to unraveling some of the mysteries about the origins of South America's lush biodiversity, the findings highlight how, even though life finds a way to recover from catastrophe, it can take a long time.
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