You would be forgiven for thinking that real numbers are, in fact, real — the word is right there in the name. But physicist Nicolas Gisin doesn’t think so.

He’s not questioning the mathematical concept of a real number. The term refers to a number that isn’t imaginary: It has no factor of i, the square root of negative one. Instead, Gisin, of the University of Geneva, debates the physical reality of real numbers: Do they appropriately represent nature? Physicists regularly use real numbers to describe the world: velocities, positions, temperatures, energies. But is that description really correct?
Gisin — known for his work on the foundations and applications of quantum mechanics — takes issue with real numbers that consist of a never-ending string of digits with no discernable pattern and that can’t be calculated by a computer. Such numbers (for example, 1.9801545341073… and so on) contain an infinite amount of information: You could imagine encoding in those digits the answers to every fathomable question in the English language — and more.

But to represent the world, real numbers shouldn’t contain unlimited information, Gisin says, because, “in a finite volume of space you will never have an infinite amount of information.”

Instead, Gisin argues March 19 on arXiv.org, only a certain number of digits of real numbers have physical meaning. After some number of digits, for example, the thousandth digit, or maybe even the billionth digit, their values are essentially random.

Most physicists don’t give much thought to philosophical puzzles like this one, but Gisin’s argument has big implications for the seemingly unrelated concept of free will. Standard classical physics, the branch of physics that governs the everyday, human-sized world, leaves no room for free will. Given the appropriate equations and the conditions of the world, classical physics says, everything can, in principle, be calculated, and therefore, predetermined.
But if the world is described by numbers that have randomness baked into them, as Gisin suggests, that would knock classical physics from its deterministic perch. That would mean that the behavior of the universe — and everything in it — can’t be predetermined, Gisin says. “There really is room for creativity.”

Ebola has reemerged. The virus has killed at least 25 people since early April in an ongoing outbreak in Congo. And on May 18, the World Health Organization declared a “high” public health risk in Congo, as well as a “high risk” of the disease spreading to neighboring countries, but stopped short of declaring a global public health emergency.

Most of the 43 confirmed and suspected cases reported as of May 18 have been in a rural area called Bikoro, within the same northwest Congolese province struck by the virus in 2014. (A separate, unrelated outbreak in West Africa at the same time made headlines as the deadliest in history.) And in May 2017, eight cases were reported in the nearby province of Bas Uélé.
But this year is different — for a couple of reasons. As of May 18, four cases have been confirmed in Mbandaka, a riverside city of at least 1.2 million people, raising the risk of the disease spreading. Health officials are also trying out an experimental vaccine this year in hopes of containing the outbreak. “We’ve seen what Ebola can do, but we know what needs to be done,” says WHO spokesperson Tarik Jasarevic.

Here’s what we know so far:

How did this year’s outbreak start?
Details are spotty. A report by the International Red Cross identifies the first suspected case as a policeman in a Bikoro village called Ikoko Impenge. Another 11 family members later fell ill after the policeman’s funeral, and seven of those relatives have also since died. (Because the bodies of Ebola victims remain contagious after death, funerary rituals can be a source of transmission.)
However, the investigation is still in progress, and both the WHO and local health officials say the first case hasn’t been identified. “We still don’t know exactly what started this outbreak,” says Jasarevic.

What’s the biggest worry right now?
Now that the virus has been detected in a city, more people could come into contact with it. “That means we have to scale up the response,” Jasarevic says. Both the 2014 and 2017 outbreaks were largely confined to remote, rural areas, which made them easier to contain. On May 17, the WHO confirmed the first urban case in Mbandaka. A day later, the Congolese Department of Health confirmed three more.

How have health officials responded so far?
On May 9, epidemiological teams from the WHO and Doctors Without Borders arrived in Bikoro and set up a mobile lab and a treatment center. They began tracking the spread of the virus. Supplies are also en route — including the experimental vaccine.

Just how experimental is this vaccine?
Researchers began working on vaccines after the deadly 2014 outbreak killed some 11,000 in West Africa (SN: 12/26/15, p. 33). The first batch of one experimental vaccine called rVSV-ZEBOV, manufactured by Merck pharmaceutical company, reached the Congolese capital of Kinshasa on May 16.

The vaccine performed well in a 2016 field trial involving 5,837 people in Guinea (SN Online: 12/22/16). But the drug must be kept at a temperature between –60° Celsius and –80°C, making transportation and storage tricky.

The vaccine still lacks formal approval, but was cleared by both the WHO and Congolese officials for “compassionate use” in response to the most recent outbreak. Vaccination could begin in the next few days, and would mark the first time a vaccine has been used in response to an Ebola outbreak in the field.

In the trial, the WHO used a “ring vaccination” strategy, immunizing family and immediate contacts of victims immediately, to help stave off the virus’ spread. A similar approach will likely be used in Congo.

Is this a new strain of Ebola?
No. Test results show that Zaire ebolavirus, which caused the 2014 and 2017 illnesses, is also responsible for this year’s outbreak, Jasarevic says. There could be some small genetic differences between versions from different years; only further genetic testing could reveal if that’s the case here.

But the good news is that the rVSV-ZEBOV vaccine targets a protein on the surface of the Zaire strain of Ebola, so it should work against the virus in the current outbreak.

Editor’s note: The Chang’e-4 relay satellite successfully lifted off from the Xichang Satellite Launch center at 5:28 a.m. Beijing time on May 21 (5:28 p.m. EDT on May 20).

The Chinese space program is set to launch a satellite aimed at supporting future communications from a planned mission to the farside of the moon.

The Chang’e-4 mission, which will include a rover and a lander, would be the first to visit the moon’s farside. In the first of a two-launch plan to get all the pieces in place, the supporting relay satellite, named Queqiao, is scheduled to lift off from the Xichang Satellite Launch Center on May 21, Chinese media report. The three-day launch window opens at 5 a.m. Beijing time (5 p.m. EDT on May 20), according to the Chinese online news site GB Times.
Queqiao will go to an orbit beyond the moon that will allow it to communicate simultaneously with points on both the moon and Earth. It will also carry a Dutch-built radio telescope, which will be switched on in 2019 to search for long-wavelength signals from the universe’s first stars.

The Chang’e-4 rover and lander were originally built as backups for the Chang’e-3 mission, which landed two spacecraft on the moon in 2013. Another 2019 mission, Chang’e-5, aims to bring back the first rocks from the moon since Apollo 17 in 1972.

The Chang’e missions are named for the Chinese moon goddess. The satellite’s name comes from another Chinese myth about two lovers separated by the Silver River, also known as the Milky Way. According to the myth, a flock of magpies form a bridge called the Queqiao once a year so the lovers can meet.

Colorectal cancer screening should begin at age 45 rather than 50, according to new guidelines released May 30 by the American Cancer Society. The recommendation is a response to the steady rise over decades in the colorectal cancer rate in younger Americans (SN: 4/1/17, p. 5).

For people at average risk for colorectal cancer — those without a personal or family history of the disease and who haven’t had inflammatory bowel disease — the ACS suggests regular screening begin at 45 with either stool-based tests or visual exams, such as a colonoscopy. The new ACS guidelines, published in CA: A Cancer Journal for Clinicians, equally endorse six possible screening methods.
Colorectal cancer is the second-most common cause of cancer death in the United States. Lifestyle choices such as smoking cigarettes, drinking alcohol, not exercising, eating processed and red meats and forgoing fruits and vegetables can increase a person’s risk for the disease.

The ACS says that screening can catch precancerous polyps and early-stage cancers, when they may be more easily treated. Journalist Katie Couric, whose husband died of colorectal cancer, and comedian Jimmy Kimmel have televised their colonoscopies to encourage viewers to get screened.
“Overall rates of colorectal cancer have declined by more than 45 percent since the 1980s, owing in part to screening,” says gastroenterologist Andrew Chan at Massachusetts General Hospital in Boston who was not involved in the guidelines. “In sharp contrast, the rates of colorectal cancer have been increasing among all age groups between 20 and 49.” Those ages have experienced a 51 percent rise in the incidence of colorectal cancer since 1994.

Scientists aren’t sure why the disease is increasing among younger Americans. But Chan says it’s not just in relation to the older group; the absolute case numbers are going up in the younger group, too. “The increase we are seeing is not simply a reflection of the drop in cancer among older groups who are being screened.”

Pluto’s heart-shaped plains are striped with sand dunes, where the sand is made of solid methane ice, a new study finds.

Images from the New Horizons spacecraft’s July 2015 flyby of Pluto show 357 linear ridges that planetary scientist Matt Telfer of the University of Plymouth in England and colleagues interpret as dunes that have been shaped by a novel process, the team reports in the June 1 Science.

The ripples lie parallel to the Al-Idrisi Montes mountain range at the western edge of Sputnik Planitia, the wide plains of nitrogen and methane ice that form part of Pluto’s famous heart-shaped region. Relatively strong winds, between about 1 and 10 meters per second, should blow from those mountains across the plains.
Computer simulations suggest that despite Pluto’s thin atmosphere, these winds are strong enough to keep sand-sized methane ice particles moving once they become airborne. But the winds are probably too weak to lift the grains off the ground in the first place.

Instead, little puffs of air coming from Sputnik Planitia’s nitrogen ice as the sun heats it could boost the methane ice particles skyward and into the wind, the team suggests. That process by which solids turn directly into vapor is called sublimation.
“That’s a novel, interesting idea,” says planetary scientist Alexander Hayes of Cornell University who was not involved in the work, but wrote a commentary piece in the same issue of Science. But the notion raises a reason for caution: Sublimation alone could explain some of the features, without the need for wind, he says.
Dunes are found across the solar system, from Earth (SN: 12/26/15, p. 5) to Mars (SN Online: 2/10/10) to Saturn’s moon Titan (SN Online: 8/28/13). Each of these worlds has the ingredients for dunes: a supply of loose, grainy material and an atmosphere or fluid to carry grains around.

“When you look at dunes across the solar system, something that always strikes me is that they form the same patterns, regardless of the environment,” Hayes says. Finding dunes on Pluto, too, suggests that the features may be ubiquitous. “If you have the material and a way to move it, you form dunes. That’s what this is telling us.”

Suicide rates have increased across the United States — and in dozens of states by more than 30 percent, according to a new report from the U.S. Centers for Disease Control and Prevention based on public health data from 1999 to 2016.

Among suicide victims counted in 2015 in 27 states, 54 percent had no known mental health condition, researchers say in the June 8 report. For those who died, circumstances surrounding their suicide included relationship or job problems, the loss of a home, legal troubles and physical health issues. These factors played a role whether suicide victims had a diagnosed medical condition or not.
With suicide, “there’s no one cause. It’s a confluence of contributors at a particular stress point in time,” says clinical psychologist Jill Harkavy-Friedman, the vice president of research at the American Foundation for Suicide Prevention in New York City. “It’s very important to know that it’s not just mental illness; it’s many factors.”

Overall, close to 45,000 Americans died by suicide in 2016. Suicide is one of three top causes of death on the rise in the country, and has contributed to a drop in U.S. life expectancy (SN Online: 12/21/07).
By state or jurisdiction, the rates of suicide in the most recent period studied (2014 to 2016) ranged from 6.9 per 100,000 people in the District of Columbia to 29.2 per 100,000 for Montana.
“Suicide is a public health problem that can be prevented,” said Anne Schuchat, the CDC’s principal deputy director, in a news conference on June 7. “That’s why it’s so important to understand the range of factors and circumstances that contribute to suicide risk.”

Starting that prevention early by teaching elementary school kids problem-solving and coping skills and how to take care of their mental and physical health is key, Harkavy-Friedman says.

To reach the National Suicide Prevention Lifeline, call 1-800-273-TALK (8255).

The story of how some of the massive stone statues on Rapa Nui, also known as Easter Island, ended up wearing stone hats involves ramps, ropes and remarkably few workers, a contested new analysis suggests.

No more than 15 people were needed to manipulate ropes that rolled stone cylinders, or pukao, up ramps to the top of forward-leaning statues, say archaeologist Sean Hixon of Penn State and his colleagues. The hatlike cylinders were then tipped over to rest atop statues, the researchers propose online May 31 in the Journal of Archaeological Science.
After clearing the ramp away, workers then carved statues’ bases flat so that the figures assumed their iconic, upright positions.

Several possible ways in which Rapa Nui inhabitants put pukao on statues have previously been proposed, including sliding pukao up wooden ramps.

“Our group is the first to consider which pukao transport and placement scenario is most consistent with the archaeological record of these multi-ton objects,” Hixon says. The researchers accounted for possible ways in which stone cylinders with the physical features of pukao could have been leveraged onto statues’ heads.

Covering just 164 square kilometers, Rapa Nui sits in the Pacific Ocean about 3,700 kilometers west of Chile. Polynesian travelers first reached the island by the 1200s (SN Online: 1/5/15).
Those people made nearly 1,000 human statues from volcanic rock. Hundreds of them, measuring up to 10 meters tall and weighing up to 74 metric tons, were moved to stone platforms, many on the coast. A team led by study coauthor Carl Lipo of Binghamton University in New York concluded in 2013 that islanders used ropes to rock upright statues enough so that the huge stones waddled down prepared dirt roads to display sites. Some statues fell along the way and were left on the side of the road. Those left-behind rocks reveal bases carved on a slight diagonal rather than flat.
The pukao were carved from a distinctive, red-hued rock. Weighing up to nearly 12 metric tons, the cylinders were probably laid on their sides and rolled down dirt roads to statue sites, where they were carved into their final shapes, the researchers say. Rock chips are still scattered around the statue sites from that activity.

Ramps made of soil and stones provided access to the tops of statues, Hixon’s group proposes. A technique called parbuckling would have enabled a small group of people to roll cylinders up ramps. In that scenario, islanders would have wrapped a long, doubled-over rope made from a local shrub around a cylinder placed on its side. One of the rope’s ends would be anchored at or near the ramp’s top and held in place by several individuals. Another group would have pulled on the rope’s free end to roll the cylinder uphill.

At the top of the ramp, islanders would have tipped the pukao into place on a statue’s head, although it’s unclear precisely how the tipping was done. Shallow indentations on the bottoms of cylinders, identified on 3-D models of 10 pukao left at a quarry site, enabled a snug fit atop the statues, the researchers say.

Archaeologist Jo Anne Van Tilburg of UCLA regards the new scenario as dubious. Base angles on Rapa Nui statues varied considerably, making them difficult and dangerous to maneuver upright, Van Tilburg says. And parbuckling pukao up long ramps would not have reduced the total effort required to move the massive cylinders to where they needed to be, she contends.

A more plausible plan, in Van Tilburg’s view, involved transporting statues and pukao together. Van Tilburg directed a 1998 experiment in which a tree-trunk frame was used to transport a replica stone statue and pukao to an experimental platform. Ropes were used to pull the frame-encased replicas, lying prone, across the rungs of a wooden, ladderlike ramp up to the platform. Six to eight families could have completed this process, she estimates.

However Rapa Nui’s statues and pukao were moved and set up, they along with other impressive stone monuments, such as England’s Stonehenge (SN Online: 9/6/12), were built by small communities rather than states or kingdoms, Lipo says.

A new kind of artificial diamond is a cut above the rest for quantum memory.

Unlike other synthetic diamonds, which could either store quantum information for a long time or transmit it clearly, the new diamond can do both. This designer crystal, described in the July 6 Science, could be a key building block in a quantum internet. Such a futuristic communications network would allow people to send supersecure messages and connect quantum computers around the world (SN: 10/15/16, p. 13).
Synthetic diamond can serve as quantum storage thanks to a type of flaw in its carbon lattice, where two neighboring carbon atoms are replaced with one noncarbon atom and an empty space (SN: 4/5/08, p. 216). This pairing exhibits a quantum property known as spin, which can be in an “up” state, a “down” state or both at once. Each of those states reflects a bit of quantum data, or qubit, that may be 1, 0 or both at once. A diamond transmits qubits by encoding them in light particles, or photons, that travel through fiber-optic cables.

Qubit-storing diamond defects are typically made with nitrogen atoms, which can store quantum data for milliseconds — a relatively long time in the quantum realm (SN: 4/23/11, p. 14). But nitrogen defects can’t communicate that data clearly. They emit light particles at a broad range of frequencies, which muddles the quantum information written into the photons.

Defects made with silicon atoms emit light more precisely, but until now haven’t been able to store qubits for longer than several nanoseconds due to their electrical interactions with nearby particles, explains Nathalie de Leon, an electrical engineer at Princeton University.

De Leon and colleagues got around this problem by forging silicon defects in a diamond infused with boron. This extra chemical ingredient shielded the delicate silicon defects from electrical interactions with nearby particles, extending the defects’ quantum memory. The boron-infused crystal nearly rivaled the long-term quantum memory of nitrogen defects, storing qubits for about a millisecond. And it gave a clean photon readout, emitting about 90 percent of its photons at the exact same frequency — compared to just 3 percent of photons spat out by nitrogen defects.
Tweaking the environment of the silicon defects was “an extremely creative way” to help keep a better grip on qubits, says Evelyn Hu, an applied physicist and electrical engineer at Harvard University not involved in the work.

This new artificial diamond could be used to construct devices called quantum repeaters for long-distance quantum communications, says David Awschalom, a physicist and quantum engineer at the University of Chicago who wasn’t involved in the work. Qubit-carrying photons can travel only up to about 100 kilometers through optical fiber before their signal gets scrambled (SN: 9/30/17, p. 8). Quantum repeaters that catch, store and re-emit photons could serve as stepping stones between fiber-optic cables to extend the reach of future networks.

When you hear the word bee, the image that pops to mind is probably a honeybee. Maybe a bumblebee. But for conservation biologist Thor Hanson, author of the new book Buzz, the world is abuzz with thousands of kinds of bees, each as beautiful and intriguing as the flowers on which they land.

Speaking from his “raccoon shack” on San Juan Island in Washington — a backyard shed converted to an office and bee-watching space, and named for its previous inhabitants — Hanson shares what he’s learned about how bees helped drive human evolution, the amazing birds that lead people to honey, and what a Big Mac would look like without bees. The following conversation has been edited for length and clarity.
SN: This bee book is unusual — it isn’t mainly about honeybees. Why did you write about lesser-known bees?

Hanson: I made a deliberate decision because I thought the celebrity bees, the honeybees, would steal the show. It was high time to turn a stage light onto these 20,000 other species of bees, which have habits that are less familiar but just as fascinating. For example, most people think of hives when they think of bees, but actually most bees are solitary.

SN: You write that this book is an “exploration of how the very nature of bees makes them so utterly necessary.” So let’s cut to the chase: Why are bees necessary?
Hanson: First is the deep connection between bees and flowering plants. They’ve had a partnership from an early stage; each spurs the other in terms of diversity. It’s an incredible role that bees have played in shaping the natural world. They’re also important to our lifestyle, first for their role in the human diet. It’s often said that one of every three bites of food depends on bees.

But there are all these other connections that we don’t think about: Bees have provided light from beeswax candles and sweetness from honey. Early industrial uses of wax included making bronze sculptures with wax molds, batiks in Indonesia and wax tablets to write on.

You can trace our relationship with bees back not hundreds, but hundreds of thousands of years. The role of honey in the human diet goes back into prehistory. That source of sugar may have even helped fuel the expansion of our brain size. It may have helped us become who we are.
SN: One of the most astonishing examples of our relationship with bees has to do with a bird called the honeyguide. Tell me about that.

Hanson: Hunter-gatherers in Africa follow this bird to bees’ nests, and have for generations (SN: 8/20/16, p. 10). The honeyguide is very good at locating a hive. But on its own, it can’t access the nest. So once it locates one, the next thing it does is look for people. It hops around on branches and makes a piercing cry to get attention, then leads a person to the honey. People climb the tree or dig out the nest, and honeyguides feed on the remains.

What’s funny is how long it took biologists to figure out this relationship. The original explanation was that the honeyguide coevolved with the honey badger, which also raids nests for honey. Then a biologist pointed out that badgers are nocturnal, and the birds aren’t. Also, no one has ever seen a honeyguide leading a badger. It makes more sense that the relationship evolved on the savannah with people out looking for honey every day.

SN: One of the book’s most hilariously geeky moments is when you go to McDonald’s and pick apart a Big Mac. Why did you do that?

Hanson: I wanted to look for the significance of bees in an unexpected place. And you don’t think of bees when you go into McDonald’s — you just don’t! I didn’t care how much people stared. I sat there with my tweezers, pulling all the seeds off the bun. I ended up with one pile you could have without bees [meat and bun] and one you couldn’t [including not only the veggies, but also the cheese and special sauce]. We could still eat, but it would be pretty dull.

SN: You’re worried about bees. Why?

Hanson: It’s the four p’s: pesticides, pathogens, parasites and poor nutrition. Poor nutrition is one that people don’t think of. We ship honeybees all over the place, and they get force-fed almond blossoms for three weeks, then they’re packed onto trucks and shipped off to pollinate apples. It’s not a healthy lifestyle, and not a varied diet.

SN: You say that bees are one of the few insects that inspire fondness instead of fear. Why do you think that is?

Hanson: Bees have been with us from the beginning. Our primordial sweet tooth led us to follow these creatures, then we domesticated bees very early on, setting out hives and reusing good sites in baobab trees. I think we have a very deep connection to these creatures.

China’s Chang’e-4 lander and rover just became the first spacecraft to land on the farside of the moon.

The lander touched down at 9:26 p.m. Eastern time on January 2, according to an announcement from the China National Space Administration. The spacecraft is part of a series of Chinese space missions named Chang’e (pronounced CHONG-uh) for the Chinese goddess of the moon.

A small rover dubbed Yutu 2, or Jade Rabbit 2, rolled off the craft several hours after landing. The rover will explore the terrain around the 186-kilometer-wide Von Kármán crater located inside the 2,500-kilometer-wide South Pole–Aitken basin. The basin, one of the largest and oldest impact features in the solar system, could contain exposed parts of the moon’s interior that might reveal details of its formation and early history (SN: 11/24/18, p. 14).
Chang’e-4 will measure some of the region’s composition, use ground-penetrating radar to probe just below the surface, and take panoramic images of a landscape that has never been seen from the ground before. It will also make measurements of charged particles and radiation, which could help support future astronaut missions, and test whether plants and insects can grow together on the moon.
Because the moon always shows the same face to Earth, it is impossible to communicate directly with spacecraft on the farside. A relay satellite named Queqiao, or Magpie Bridge, that launched in May 2018 will beam signals between Chang’e-4 and Earth (SN Online: 5/20/18).
The landing marks China’s second lunar landing, and a step towards more ambitious moon missions. The Chinese space agency is planning another mission to collect moon rock samples later in 2019.