Tag Archive : SCIENCE

The Parker Solar Probe just earned the title of the fastest-moving manmade object. Launched by NASA this past August, this robotic spacecraft is currently very, very near the Sun, on its way to probe the outer corona of our local star.

OK, I know you have questions. Let me just jump right into it.

How fast is it going?

According to NASA, its current speed is 153,545 mph (or 68.6 kilometers per second). But really, that just means super fast. It's nearly impossible to imagine something that fast when the fastest man-made stuff on Earth is perhaps a rail gun projectile at about 2.52 km/s. That means the Parker Solar Probe is traveling at a speed that is 27 times faster that the fastest thing we've got down here. Zoom fast.

What does this have to do with the speed of light?

Of course, light is even faster. Light has a speed of about 3 x 10⁸ m/s (300,000 km/s). But why does that matter? You can't get an object up to (or greater than) the speed of light. Why? Let's start with an example. Suppose I have a force of 1 Newton and I push on an object at rest with a mass of 1 kg for 1 second (I'm using easy numbers). The momentum principle says that the momentum is the product of mass and velocity. Also, the force applied to an object tells us the rate of change of momentum. This means a 1 Newton force for 1 second gives a CHANGE in momentum of 1 kg*m/s (the change part is important).

This mostly works for super high speeds. The momentum principle still works as long as you use a better definition of momentum. It should look like this (in one dimension).

In this expression, the p is momentum (don't ask why) and the c represents the speed of light. Notice that as the velocity gets closer to the speed of light, you get a much smaller increase in speed for the same force. In fact, if the velocity was equal to the speed of light you would be dividing by zero—which is generally a bad thing.

Just to be clear, there aren't two models for momentum. You can always use the more complicated version of momentum. Try this: Calculate the momentum of a baseball with a mass of 0.142 kg and a speed of 35 m/s. First do this with the simple formula of mass times velocity and you get 497 kg*m/s. Now try it with the more complicated formula. Guess what? You get the same thing. I recommend using the simple formula whenever possible.

Just how fast is the Parker Solar Probe going compared to the speed of light? If you divide the probe's speed by the speed of light you get 0.00023. Actually, we can write this as 0.00023c (where c is the speed of light). It's fast, but it's not light-speed fast.

Why is this speed relative to the Sun?

You will probably see something about the speed of the Parker Solar Probe labeled as the heliocentric velocity. What's the deal with that?

On Earth, this is rarely an issue. If you are driving your car at 55 mph, everyone understands that we are measuring this velocity with respect to the stationary ground. In fact, velocities only really make sense when measured relative to some reference frame. On the Earth, the obvious reference frame is the ground.

What if you didn't want to use the Earth's surface as a reference frame? Imagine a police officer pulling you over in your car and saying "oh hello, I clocked you at 67,055 mph." That could indeed be true since the Earth isn't stationary. In order to orbit the Sun, it has to travel with a speed of 67,000 mph to make it all the way around the Sun in one year. Yes, that's fast (with respect to the Sun).

If you wanted to measure the speed of the Parker Solar Probe with respect to the Earth, you would have a tough time because you wouldn't just have one value. As the probe moves closer to the Sun, the probe and the Earth can be moving in different directions. So even though the speed relative to the Sun could stay constant, its speed relative to the Earth would change since the Earth is turning in its orbit around the Sun.

If you really want to get crazy, you could use some other reference frame—like the galactic center. But let's not get crazy.

How does the probe break its own speed record?

The probe will go even faster than it is already traveling. NASA projects a slightly faster speed as it gets closer to the Sun in 2024. But why does it get faster when it is closer to the Sun?

There are two key ideas here. The first is the gravitational force. This is an attractive force between the Sun and the probe. The magnitude of this force increases as the distance between them decreases. Oh, don't worry—you can't notice an increase in gravitational force as you move closer to the ground. Even if you moved a vertical distance of 1000 meters, this is insignificant compared to the size of the Earth with a radius of 6.37 million meters.

The other part of the problem is circular motion. Imagine the space probe traveling in a circular orbit (which isn't actually true). In order for an object to move in a circle, there needs to be a force pulling it towards the center of the circle. The magnitude of this sideways force is proportional to the square of the object's velocity, but inversely proportional to the radius of the circle. Putting the gravitational force and the required circular force together, I get the following expression for the orbital velocity.

In this expression, M_s is the mass of the Sun and G is the gravitational constant. But the main point is that the velocity increases as the radius decreases. It's just physics.

Homework

If you want some fun physics homework questions, I have you covered. Here you go.

• Calculate the kinetic energy of the Parker Solar Probe at its current velocity (with respect to the Sun). Yes, you need to look up or estimate the mass of the probe.
• Suppose you were going to get the probe up to speed by having a human on a stationary bike connected to a generator. The human can produce 50 Watts for as long as you like (maybe it's two humans who take turns). How long would it take to get the probe up to its current speed?
• The probe has been in space for about 3 months (let's go with 3 months). Suppose that the probe was traveling at a constant speed this whole time (use its current velocity). Create a plot of speed vs. time as measured relative to the Earth. Remember, in 3 months the Earth changes direction.
• How many candy bars would the probe need to "eat" to get to its current speed. Yes, I'm assuming the probe eats. This might be useful too.

This story originally appeared on Grist and is part of the Climate Desk collaboration.

When a blue-hulled cargo ship named Venta Maersk became the first container vessel to navigate a major Arctic sea route this month, it offered a glimpse of what the warming region might become: a maritime highway, with vessels lumbering between Asia and Europe through once-frozen seas.

Years of melting ice have made it easier for ships to ply these frigid waters. That’s a boon for the shipping industry but a threat to the fragile Arctic ecosystem. Nearly all ships run on fossil fuels, and many use heavy fuel oil, which spews black soot when burned and turns seas into a toxic goopy mess when spilled. Few international rules are in place to protect the Arctic’s environment from these ships, though a proposal to ban heavy fuel oil from the region is gaining support.

“For a long time, we weren’t looking at the Arctic as a viable option for a shortcut for Asia-to-Europe, or Asia-to-North America traffic, but that’s really changed, even over the last couple of years,” says Bryan Comer, a senior researcher with the International Council on Clean Transportation’s marine program. “It’s just increasingly concerning.”

Venta Maersk departed from South Korea in late August packed with frozen fish, chilled produce, and electronics. Days later, it sailed through the Bering Strait between Alaska and Russia, before cruising along Russia’s north coast. At one point, a nuclear icebreaker escorted Venta Maersk through a frozen Russian strait, then the container vessel continued to the Norwegian Sea. It’s expected to arrive in St. Petersburg later this month.

The trial voyage wouldn’t have been possible until recently. The Arctic region is warming twice as fast as the rest of the planet, with sea ice, snow cover, glaciers, and permafrost all diminishing dramatically over recent decades. In the past, only powerful nuclear-powered icebreakers could forge through Arctic seas; these days, even commercial ships can navigate the region from roughly July to October—albeit sometimes with the help of skilled pilots and icebreaker escorts.

Russian tankers already carry liquefied natural gas to Western Europe and Asia. General cargo vessels move Chinese wind turbine parts and Canadian coal. Cruise liners take tourists to see surreal ice formations and polar bears in the Arctic summer. Around 2,100 cargo ships operated in Arctic waters in 2015, according to Comer’s group.

“Because of climate change, because of the melting of sea ice, these ships can operate for longer periods of time in the Arctic,” says Scott Stephenson, an assistant geography professor at the University of Connecticut, “and the shipping season is already longer than it used to be.” A study he co-authored found that, by 2060, ships with reinforced hulls could operate in the Arctic for nine months in the year.

Stephenson says that the Venta Maersk’s voyage doesn’t mean that an onrush of container ships will soon be clogging the Arctic seas, given the remaining risks and costs needed to operate in the region. “It’s a new, proof-of-concept test case,” he says.

Maersk, based in Copenhagen, says the goal is to collect data and “gain operational experience in a new area and to test vessel systems,” representatives from the company wrote in an email. The ship didn’t burn standard heavy fuel oil, but a type of high-grade, ultra-low-sulfur fuel. “We are taking all measures to ensure that this trial is done with the highest considerations for the sensitive environment in the region.”

Sian Prior, lead advisor to the HFO-Free Arctic Campaign, says that the best way to avoid fouling the Arctic is to ditch fossil fuels entirely and install electric systems with, say, battery storage or hydrogen fuel cells. Since those technologies aren’t yet commercially viable for ocean-going ships, the next option is to run ships on liquefied natural gas. The easiest alternative, however, is to switch to a lighter “marine distillate oil,” which Maersk says is “on par with” the fuel it’s using.

But many ships still run on cheaper heavy fuel oil, made from the residues of petroleum refining. In 2015, the sludgy fuel accounted for 57 percent of total fuel consumption in the Arctic, and was responsible for 68 percent of ships’ black carbon emissions, according to the International Council on Clean Transportation.

Black carbon wreaks havoc on the climate, even though it usually makes up a small share of total emissions. The small dark particles absorb the sun’s heat and directly warm the atmosphere. Within a few days, the particles fall back down to earth, darkening the snow and hindering the snow’s ability to reflect the sun’s radiation—resulting in more warming.

When spilled, heavy fuel oil emulsifies on the water’s surface or sinks to the seafloor, unlike lighter fuels which disperse and evaporate. Clean-up can take decades in remote waters, as was the case when the Exxon Valdez crude oil tanker slammed into an Alaskan reef in 1989.

“It’s dirtier when you burn it, the options to clean it up are limited, and the length it’s likely to persist in the environment is longer,” Prior says.

In April, the International Maritime Organization, the U.N. body that regulates the shipping industry, began laying the groundwork to ban ships from using or carrying heavy fuel oil in the Arctic. Given the lengthy rulemaking process, any policy won’t likely take effect before 2021, Prior says.

One of the biggest hurdles will be securing Russia’s approval. Most ships operating in the Arctic fly Russian flags, and the country’s leaders plan to invest tens of billions of dollars in coming years to beef up polar shipping activity along the Northern Sea Route. China also wants to build a “Polar Silk Road” and redirect its cargo ships along the Russian route.

Such ambitions hinge on a melting Arctic and rising global temperatures. If the warming Arctic eventually does offer a cheaper highway for moving goods around the world, Comer says, “then we need to start making sure that policies are in place.”

Way, way out at the cold, dark edges of the solar system—past the rocky inner planets, beyond the gas giants, a billion miles more remote than Pluto—drifts a tiny frozen world so mysterious, scientists still aren't entirely sure if it's one world or two.

Astronomers call it Ultima Thule, an old cartography term meaning "beyond the known world." Its name is a reference to its location in the Kuiper Belt, the unexplored "third zone" of our solar system populated by millions of small, icy bodies.

Numerous though they are, no Kuiper Belt object has ever been seen up close. NASA's two Voyager probes—which traversed the third zone decades ago—might have spied a glimpse of one had they been equipped with the right instruments, except that the Kuiper Belt hadn't even been detected yet. On New Years Eve, for the first time, NASA will get a chance at some facetime with one of these enigmatic space rocks.

At 9:33 pm PST, 33 minutes past midnight on the East Coast, the agency's New Horizons probe will make a close pass of Ultima Thule, making it the most distant object ever to be visited by a spacecraft.

Astronomers have almost no idea what awaits them. “What’s it going to look like? No one knows. What’s it going to be made of? No one knows. Does it have rings? Moons? Does it have an atmosphere? Nobody knows. But in a few days we’re going to open that present, look in the box, and find out,” says Alan Stern, the mission's primary investigator.

New Horizons has traveled for 13 years and across 4 billion miles to reach this point, and the probe looks to be in fine shape: Mission planners confirmed earlier this month that it will pass within 2,200 miles of Ultima Thule after determining that large objects, like moons, and smaller ones, like dust, were unlikely to pose a threat to the spacecraft as it blazed past in excess of 31,000 miles per hour. ("When you're traveling that fast, hitting something even the size of a grain of rice could destroy the spacecraft," says Hal Weaver, the mission's project scientist.)

New Horizons' trajectory will carry it three times closer to Ultima Thule than it did Pluto, which it shot past in the summer of 2015. The photos New Horizons beamed back then were the most detailed ever captured not just of the former planet, but the outer solar system. Because of its proximity, the images the probe collects of Ultima Thule will be more detailed still, and from a billion miles deeper in space. "Pluto blew our doors off," Stern says, "but now we're heading for something much more wild and woolly."

Stern and his team discovered the object in 2014 using the Hubble Space Telescope, while searching the sky for places New Horizons could visit after its brief encounter with Pluto. In those first images, Ultima was just a glob of pixels that shifted every few minutes against a backdrop of unmoving stars.

In more recent images, captured by New Horizons' Long Range Reconnaissance Imager, the object still appears as little more than a speck in a sea of much brighter specks. "When you search for it, it looks like stars puked all over the imagery," says planetary scientist Amanda Zangari, who spent most of December collecting Ultima Thule's position and brightness measurements. "To even see the darn thing, you need to stack multiple images, account for the distortion between them, and subtract the stars." At 1/100th the diameter of Pluto, and 1/10,000th its brightness, Ultima Thule makes for a more elusive quarry than the erstwhile planet.

Through their observations, the team has determined that Thule (whose official designation is 2014 MU69) is either two separate objects orbiting one another at close range, or a pair of bodies that gravitated toward each other til they merged, forming the two lobes of something astronomers call a contact binary. Either way, the data suggests Ultima is no more than 20 miles in diameter, dark as reddish dirt, and well within range of New Horizons' fuel supply.

It is also, in all likelihood, very, very old. Which is precisely why astronomers are so excited to study it up close.

Kuiper Belt objects like Ultima Thule are thought to be remnants of the solar system's formation—the cosmic refuse that remained after the planets came into being some 4.6 billion years ago. That makes them an enticing destination for astronomers: Many of those objects aren't just ancient, they're also, astronomers think, perfectly preserved by temperatures approaching absolute zero. (So far removed is Ultima Thule from the sun's warming rays, that our parent star would appear to an observer on its surface about the size that Jupiter does from here on Earth). NASA's plan to visit one, map its features, study its makeup, detect its atmosphere (if one exists), and search it for satellites and rings is more than a flyby mission. It's an archaeological expedition of cosmic scale and consequence.

New Horizons will investigate Ultima with the same suite of instruments it used to study the Pluto system back in 2015. A trio of optical devices will capture images of the object in color and black-and-white, map its composition and topography, and search for gasses emanating from its surface. Two spectrometers will also search for charged particles in Ultima Thule's environs; a radio-science instrument will measure its surface temperature; and a dust counter will detect flecks of interplanetary debris. Fully loaded, the piano-sized probe weighs a hair over 1,000 pounds and requires less power than a pair of 100-watt light bulbs to operate its equipment.

After its New Years Eve flyby, New Horizons will continue on its path out of the Kuiper Belt. But the third zone is vast. Even traveling at nearly nine miles per second, it'll take the spacecraft a decade to traverse it and enter interstellar space. Stern and his colleagues will use that time to search for yet another target—one even further from the sun than Ultima Thule, and shrouded, perhaps, in still more mystery. It's a tantalizing prospect for the New Horizons team. "To visit a place you know nothing about," Weaver says. "That's exploration at its finest."

Learn More About the New Horizons Mission

• In 2015, New Horizons zipped past Pluto, giving astronomers their closest look yet at the erstwhile planet and its moons.
• NASA's probe traveled some 3 billion miles to reach Pluto. It's traveled another billion, still, to reach Ultima Thule.
• How does New Horizons beam all its observations back to Earth, when it's so far away? Very slowly.

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Mission to Pluto: The Story Behind the Historic Trip

It’s taken nine years to get there, but on July 14, 2015 the New Horizons spacecraft will finally fly by its destination: Pluto. Find out how the historic mission to Pluto happened from the people who helped launch it.

This story originally appeared on Grist and is part of the Climate Desk collaboration.

You probably didn’t give much thought to how exactly you loaded this webpage. Maybe you clicked a link from Twitter or Facebook and presto, this article popped up on your screen. The internet seems magical and intangible sometimes. But the reality is, you rely on physical, concrete objects—like giant data centers and miles of underground cables—to stay connected.

All that infrastructure is at risk of being submerged. In just 15 years, roughly 4,000 miles of fiber-optic cables in US coastal cities could go underwater, potentially causing internet outages.

That’s the big finding from a new, peer-reviewed study from the University of Wisconsin-Madison and the University of Oregon. To figure out how rising seas could affect the internet’s physical structures, researchers compared a map of internet infrastructure to the National Oceanic and Atmospheric Administration’s predictions for sea-level rise near US coasts.

In New York City, about 20 percent of fibers distributed throughout the city are predicted to flood within 15 years—along with 32 percent of the fibers that connect the metropolis to other cities and 43 data centers. The research suggests that Seattle and Miami are especially vulnerable, along with many coastal areas.

“All of this equipment is meant to be weather-resistant—but it’s not waterproof,” says Paul Barford, UW-Madison professor of computer science and a coauthor of the paper. Much of the system was put into place in the ’90s without much consideration of climate change, he says.

On top of that, much of the internet’s physical infrastructure is aging. Paul Barford says a lot of it was designed to last only a few decades and is now nearing the end of its lifespan.

That is, if the floods don’t get to it first. While 15 years may seem shockingly soon, we’re already seeing more high tide flooding, points out Carol Barford (married to the aforementioned Paul), a coauthor on the paper and director of UW-Madison’s Center for Sustainability and the Global Environment. We’re seeing outages related to extreme weather, too: Hurricane Irma, for example, left over a million people without internet access.

It’s hard to predict exactly what would happen inland when coastal infrastructure floods—but the internet is an interconnected system, so damage in one place could affect others. For those inland, it’s possible that coastal flooding could cause a total internet connection outage, or issues in connecting to particular web pages and services.

Still, there’s a lot of research to be done. “We need to better understand the scope of the problem to create good solutions,” says Ramakrishnan Durairajan, a University of Oregon assistant professor of computer and information sciences and the paper’s lead author. Further studies could examine the effects of increased extreme weather on the system, he says, as well as ways to better engineer web traffic in the face of floods or other climate-induced disasters.

The takeaway, Carol Barford says: “If we want to be able to function like we expect every day, we’re going to have to spend money and make allowances and plans to accommodate what’s coming.”

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King Tides Show Us How Climate Change Will Threaten Coastal Cities

Seawall-topping king tides occur when extra-high tides line up with other meteorological anomalies. In the past they were a novelty or a nuisance. Now they hint at the new normal, when sea level rise will render current coastlines obsolete.

Last week, scientists published the biggest-ever study of the genetic influence on educational attainment. By analyzing the DNA of 1.1 million people, the international team discovered more than a thousand genetic variants that accounted—in small part—for how far a person gets through school. It made a lot of people nervous, as they imagined how this new research could be applied in Gattaca-esque testing tools.

But those concerns aren’t new—and neither is the kind of research published last Monday. This sort of correlational work for educational attainment has been in progress since at least 2011. And there is already a consumer product on the market that draws from that early research.

Log onto the Helix DNA marketplace—it’s like the app store for consumer genetic products—and the candy-colored website invites you to “Get started with DNA.” Clicking through takes you to one of Helix’s featured products: the DNAPassport. It was developed by Denver-based HumanCode, which Helix acquired in June, and lets users explore where their ancestors come from, whether they might be sensitive to gluten or lactose, and more than 40 other genetically-influenced traits. One of them is something called “academic achievement.”

It’s based on a single genetic variant called rs11584700, near a gene called LRRN2 that codes for a protein involved in neuron signaling. And it was discovered by the same consortium that published the massive genetic analysis on Monday.

Social scientists’ first attempts at unearthing links between genes and people’s behaviors, in the mid-2000s, were plagued by small samples, weak methods, and unreproducible results. So to save the field from itself, a behavioral economist named Daniel Benjamin, at the University of Southern California, borrowed an idea from medical geneticists. He convinced research organizations from around the world to pool their data, giving them enough power to run something called a Genome-Wide Association Study, or GWAS. The first thing they looked at was how long people stay in school.

In 2011, Benjamin founded the Social Science Genetic Association Consortium, along with David Cesarini and Philipp Koellinger. Their goal was to find a reliable measure of heritable influence on education attainment so that other researchers could control for genetics in their experiments, the same way they’d control for socioeconomic status or zip code. Since then, the SSGAC has uncovered more than 1,000 genetic variations associated with years of schooling. Benjamin’s team has gone out of its way to make it clear that each one exerts only a teeny tiny bit of influence—three additional weeks of education, max—and that even collectively, the variants are not powerful enough to predict an individual’s academic achievement.

But that’s not stopping companies from using their research to sell people insights into their degree-seeking behavior. Based on one of the consortium’s earlier papers, and a second one using data from the UK’s National Child Development Study, HumanCode added the academic achievement feature to its DNAPassport app last December. Users who’ve got a pair of G’s or an A and a G at that location will learn that those genotypes are “associated with slightly higher educational attainment in Europeans.” If your spit turns up an AA, well, no higher ed association for you.

“I’m not afraid to share that my own academic achievement SNP is not the desirable one,” says Chris Glodé, formerly the CEO of HumanCode, now a chief product officer at Helix, as he sends over a screenshot of his “Normal,” aka AA genotype. He says HumanCode made the decision to add the feature after seeing educational attainment show up on a number of third-party sites like GenePlaza, Genome Link, and Promethease. These are websites where people can go to upload the genetic data files they get from spit testing kits like 23andMe, Ancestry, and Helix, to further explore their DNA. “A lot of people are using these third-party services, so the idea that we’re going to prevent people from finding out this information for themselves seems not only unlikely, but also misaligned with our mission,” says Glodé. “The question then became, can we present this information responsibly?”

HumanCode sold DNAPassport on Helix’s marketplace even before the company was acquired. So its product has been subject to Helix’s scientific evaluation process since late 2017: The company requires that any variants used in a product are based on studies with more than 2,000 people whose results have been replicated. In the case of academic achievement, Helix also required that HumanCode list it with a disclaimer of sorts, called a LAB designation. “The research supporting the genetics underlying this trait require more work,” reads the site’s language. “Traits with the LAB designation may have limited scientific support from studies that are small/preliminary or lacking independent replication. Additionally, some traits with LAB designations have valid and replicated associations, but we want to learn more about how genetics influences the trait.”

About a quarter of DNAPassport’s traits fall under LAB designation. They’re all grouped together in the “Just for Fun” category of traits, “to reinforce that this information shouldn’t be used for making lifestyle decisions,” says Glodé. Sometimes, when new and better research comes out, traits get upgraded. If he were still the CEO of HumanCode and it was still an independent company, his team would probably update the academic achievement trait with the latest variants. But he says Helix has no plans to do that. Instead, it’s focused on encouraging developers to bring new products to its platform, including tests that might include educational attainment.

“Provided the context was appropriate, that a product was intended to be informational and educational, I think Helix would be open to it,” says Glodé. “But they would likely still require the results to presented the way we did in DNAPassport, providing additional qualifications that the research isn’t as well established as for traits like height and eye color.” And that the results don’t apply beyond people of European descent. Like the vast majority of genetic population studies, the SSGAC’s research cohort is overwhelmingly European, and the variants identified have little predictive power for non-European populations.

Benjamin—the SSGAC co-founder—says relying on his study’s genetic score to predict educational attainment for an individual would be inaccurate. Using just a single variant, even more so. “If companies want to do this I would be concerned that they’re accurately communicating the information,” says Benjamin. “It’s not just a matter of disclosing the limitations of the predictive power.” Along with other members of the consortium and its advisory board, Benjamin spent hundreds of hours writing a 27-page FAQ to accompany their paper, explicitly because of the potential for misinterpretation. He credits companies like 23andMe that use a rating system to communicate how confident users can be in the results.

While 23andMe has played a significant role in supporting research into the genetics of educational attainment—the company contributed deidentified data on 365,536 of its research-consented customers to the SSGAC’s latest study—it does not at this time offer a report for academic achievement. Nor does it have any educational attainment reports in the product pipeline, according to a company spokesperson.

Remember, no one knows exactly how these genes create a tendency toward degree-seeking behavior. They could influence how fast neurons fire, or they could make sitting at a hard wooden desk for eight hours not feel like torture. Maybe they remove the stigma of asking for extra time on tests or assignment extensions. Researchers will need to do a lot more work to figure out the why. But when they do, you can be sure someone will try to sell it to you.

Front and center for this week’s jaunt into space is one of the most interesting—and possibly habitable—moons of our solar system. As the largest moon of Saturn, Titan measures about 3,200 miles in diameter, bigger than our own moon (which is a little over 2,000 miles wide). It’s covered in a thick atmosphere of clouds and haze that likely condenses onto the surface—and there might be organic compounds within.

So let us have a look at Titan like we’ve never seen before, thanks to the Cassini spacecraft’s Visual and Infrared Mapping Spectrometer. Earlier views were hampered by variations in resolution and lighting that reduced the surface clarity. (Blame tiny particles in the moon’s atmosphere called aerosols for scattering visible light.) But now astronomers are now able to peer below the clouds of Titan in the infrared spectrum, along with combining 13 years of image data—the entire length of time that NASA’s Cassini was in orbit.

It gets better. Titan has lakes and rivers, but unlike the lakes and rivers on Earth that are filled with actual water, Titan’s are made up of liquid methane and ethane. Scientists are still studying the provenance of these liquids and how they remain stable. Here’s a hint: Titan’s surface is a stone-cold -290 degrees Fahrenheit.

So put on a Mylar sweater, bring some oxygen, and enjoy pioneering to Titan!

Once you’re done dipping into a dwarf planet and beholding a nebula, peruse Wired’s full collection of space photos here.

This story was originally published by The Guardian and is reproduced here as part of the Climate Desk collaboration.

Greta Thunberg cut a frail and lonely figure when she started a school strike for the climate outside the Swedish parliament building last August. Her parents tried to dissuade her. Classmates declined to join. Passersby expressed pity and bemusement at the sight of the then unknown 15-year-old sitting on the cobblestones with a hand-painted banner.

Eight months on, the picture could not be more different. The pigtailed teenager is feted across the world as a model of determination, inspiration, and positive action. National presidents and corporate executives line up to be criticized by her, face to face. Her Skolstrejk för Klimatet (school strike for climate) banner has been translated into dozens of languages. And, most striking of all, the loner is now anything but alone.

On March 15, when she returns to the cobblestones (as she has done almost every Friday in rain, sun, ice and snow), it will be as a figurehead for a vast and growing movement. The global climate strike this Friday is gearing up to be one of the biggest environmental protests the world has ever seen. As it approaches, Thunberg is clearly excited.

“It’s amazing,” she says. “It’s more than 71 countries and more than 700 places, and counting. It’s increasing very much now, and that’s very, very fun.”

A year ago, this was unimaginable. Back then, Thunberg was a painfully introverted, slightly built nobody, waking at 6 am to prepare for school and heading back home at 3 pm. “Nothing really was happening in my life,” she recalls. “I have always been that girl in the back who doesn’t say anything. I thought I couldn’t make a difference because I was too small.”

She was never quite like the other kids. Her mother, Malena Ernman, is one of Sweden’s most celebrated opera singers. Her father, Svante Thunberg, is an actor and author (named after Svante Arrhenius, the Nobel Prize–winning scientist who in 1896 first calculated how carbon dioxide emissions could lead to the greenhouse effect). Greta was exceptionally bright. Four years ago, she was diagnosed with Asperger’s.

“I overthink. Some people can just let things go, but I can’t, especially if there’s something that worries me or makes me sad. I remember when I was younger, and in school, our teachers showed us films of plastic in the ocean, starving polar bears and so on. I cried through all the movies. My classmates were concerned when they watched the film, but when it stopped, they started thinking about other things. I couldn’t do that. Those pictures were stuck in my head.”

She has come to accept this as part of who she is—and made it a motivating force instead of a source of paralyzing depression, which it once was.

At about the age of 8, when she first learned about climate change, she was shocked that adults did not appear to be taking the issue seriously. It was not the only reason she became depressed a few years later, but it was a significant factor.

“I kept thinking about it, and I just wondered if I am going to have a future. And I kept that to myself because I’m not very much of a talker, and that wasn’t healthy. I became very depressed and stopped going to school. When I was home, my parents took care of me, and we started talking because we had nothing else to do. And then I told them about my worries and concerns about the climate crisis and the environment. And it felt good to just get that off my chest.

“They just told me everything will be all right. That didn’t help, of course, but it was good to talk. And then I kept on going, talking about this all the time and showing my parents pictures, graphs and films, articles and reports. And, after a while, they started listening to what I actually said. That’s when I kind of realized I could make a difference. And how I got out of that depression was that I thought: It is just a waste of time feeling this way because I can do so much good with my life. I am trying to do that still now.”

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The WIRED Guide to Climate Change

Her parents were the guinea pigs. She discovered she had remarkable powers of persuasion, and her mother gave up flying, which had a severe impact on her career. Her father became a vegetarian. As well as feeling relieved by the transformation of their formerly quiet and morose daughter, they say they were persuaded by her reasoning. “Over the years, I ran out of arguments,” says her father. “She kept showing us documentaries, and we read books together. Before that, I really didn’t have a clue. I thought we had the climate issue sorted,” he says. “She changed us and now she is changing a great many other people. There was no hint of this in her childhood. It’s unbelievable. If this can happen, anything can happen.”

The climate strike was inspired by students in Parkland, Florida, who walked out of classes in protest against the US gun laws that enabled the massacre on their campus. Greta was part of a group that wanted to do something similar to raise awareness about climate change, but they couldn’t agree what. Last summer, after a record heat wave in northern Europe and forest fires that ravaged swathes of Swedish land up to the Arctic, Thunberg decided to go it alone. Day one was August 20, 2018.

“I painted the sign on a piece of wood and, for the flyers, wrote down some facts I thought everyone should know. And then I took my bike to the Parliament and just sat there,” she recalls. “The first day, I sat alone from about 8:30 am to 3 pm—the regular school day. And then on the second day, people started joining me. After that, there were people there all the time.”

She kept her promise to strike every day until the Swedish national elections. Afterward, she agreed to make a speech in front of thousands at a People’s Climate March rally. Her parents were reluctant. Knowing Thunberg had been so reticent that she had previously been diagnosed with selective mutism, they tried to talk her out of it. But the teenager was determined. “In some cases where I am really passionate, I will not change my mind,” she says. Despite her family’s concerns, she delivered the address in nearly flawless English and invited the crowd to film her on their mobile phones and spread the message through social media. “I cried,” says her proud dad.

People with selective mutism have a tendency to worry more than others. Thunberg has since weaponized this in meetings with political leaders and with billionaire entrepreneurs in Davos. “I don’t want you to be hopeful. I want you to panic. I want you to feel the fear I feel every day. And then I want you to act,” she told them.

Such tongue-lashings have gone down well. Many politicians laud her candidness. In return, she listens to their claims that stronger climate policies are unrealistic unless the public make the issue more of a priority. She is unconvinced. “They are still not doing anything. So I don’t know really why they are supporting us, because we are criticizing them. It’s kind of weird.” She has also been withering about leaders in the US, UK, and Australia who either ignore the strikers or admonish them for skipping classes. “They are desperately trying to change the subject whenever the school strikes come up. They know they can’t win this fight because they haven’t done anything.”

Such blunt talk has found a broad audience among people jaded by empty promises and eager to find a climate leader willing to ramp up ambition. Thunberg’s rise coincides with growing scientific concern. A slew of recent reports has warned that oceans are heating and the poles melting faster than expected. Last year’s UN Intergovernmental Panel on Climate Change spelled out the dangers of surpassing 1.5 degrees Celsius of global warming. To have any chance of avoiding that outcome, it said, emissions must fall rapidly by 2030. That will require far more pressure on politicians—and nobody has proved more effective at that over the past eight months than Thunberg.

The girl who once slipped into despair is now a beacon of hope. One after another, veteran campaigners and grizzled scientists have described her as the best news for the climate movement in decades. She has been lauded at the UN, met French president Emmanuel Macron, shared a podium with the European Commission president Jean-Claude Juncker, and has been endorsed by the German chancellor, Angela Merkel.

You may think this would put the weight of the world on the 16-year-old’s shoulders, but she claims to feel no pressure. If “people are so desperate for hope,” she says, that is not her or the other strikers’ responsibility.

“I don’t care if what I’m doing—what we’re doing—is hopeful. We need to do it anyway. Even if there’s no hope left and everything is hopeless, we must do what we can.”

In this regard, her family sees her singular focus as a blessing. She is someone who strips away social distractions and focuses with black-and-white clarity on the issues. “It’s nothing that I want to change about me,” she says. “It’s just who I am. If I had been just like everyone else and been social, then I would have just tried to start an organization. But I couldn’t do that. I’m not very good with people, so I did something myself instead.”

While she has little time for chitchat, she gets satisfaction from speaking to a big audience about climate change. Regardless of the size of the crowd, she says she does not feel the least bit nervous.

She seems incapable of the cognitive dissonance that allows other people to lament what is happening to the climate one minute, then tuck into a steak, buy a car, or fly off for a weekend break the next. Although Thunberg believes political action far outweighs individual changes to consumer habits, she lives her values. She is a vegan and only travels abroad by train.

At its best, this sharpness can slice through the Gordian knot of the climate debate. It can also sting. There are no comfortable reassurances in her speech, just a steady frankness. Asked whether she has become more optimistic because the climate issue has risen up the political agenda and politicians in the US and Europe are considering green New Deals that would ramp up the transition to renewable energy, her reply is brutally honest. “No, I am not more hopeful than when I started. The emissions are increasing, and that is the only thing that matters. I think that needs to be our focus. We cannot talk about anything else.”

Some people consider this a threat. A handful of fossil fuel lobbyists, politicians, and journalists have argued Thunberg is not what she seems—that she was propelled into prominence by environmental groups and sustainable-business interests. They say the entrepreneur who first tweeted about the climate strike, Ingmar Rentzhog, used Thunberg’s name to raise investment for his company, but her father says the connection was overblown. Greta, he says, initiated the strike before anyone in the family had heard of Rentzhog. As soon as she found he had used her name without her permission, she cut all links with the company and has since vowed never to be associated with commercial interests. Her family says she has never been paid for her activities. In a recent interview, Rentzhog defended his actions, denied exploiting Greta, and said that climate change, not profit, was his motive.

On social media, there have been other crude attacks on Thunberg’s reputation and appearance. Already familiar with bullying from school, she appears unfazed. “I expected when I started that if this is going to become big, then there will be a lot of hate,” she says. “It’s a positive sign. I think that must be because they see us as a threat. That means that something has changed in the debate, and we are making a difference.”

She intends to strike outside parliament every Friday until the Swedish government’s policies are in line with the Paris climate agreement. This has led to what she calls “strange contrasts”: balancing her math homework with her fight to save the planet; listening attentively to teachers and decrying the immaturity of world leaders; weighing up the existential threat of climate change alongside the agonizing choice of what subjects to study in high school.

It can be grueling. She still rises at 6 am to get ready for school. Interviews and writing speeches can leave her working 12- to 15-hour days. “Of course, it takes a lot of energy. I don’t have much spare time. But I just keep reminding myself why I am doing this, and then I just try to do as much as I can.” So far, this does not appear to have affected her academic performance. She keeps up with homework and is in the top five in her class, according to her father.

And now that she is active on climate change, she is no longer lonely, no longer silent, no longer so depressed. She is too busy trying to make a difference. And enjoying herself.

This Friday, when she takes her usual spot outside the Swedish Parliament, she will be joined by classmates and students from other schools. “It’s going to be very, very big internationally, with hundreds of thousands of children going to strike from school to say that we aren’t going to accept this anymore,” she says. “I think we are only seeing the beginning. I think that change is on the horizon and the people will stand up for their future.”

And then the activist slips back into being a teenager. “I’m looking forward to it and to see all the pictures the day afterwards. It’s going to be fun.”

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Sean Parker, Napster cofounder

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Alex Marson, biologist and infectious disease doctor at UC San Francisco

When Sean Parker was young, he cofounded Napster and changed the way we listen to music. In his twenties, he helped jump-start Facebook and changed the way we interact with each other. Now, at age 38, he’s set on changing something else: the way we treat disease. The Parker Institute for Cancer Immunotherapy, which he founded in 2016, has dedicated $250 million toward using new technologies like Crispr to teach the human body to vanquish cancer. Alex Marson is a scientist building the tools to do just that. His research at UC San Francisco and the Parker Institute rejiggers the DNA of T cells—your immune system’s sentinels—to better recognize and attack malignant mutineers. Parker and Marson sat down to talk about Crispr, genome editing, and the most exciting coding language today: DNA. —Megan Molteni

Sean Parker: I first learned about the therapeutic potential of Crispr a few years ago, and back then it really only allowed us to remove a gene or prevent it from functioning. The ability to completely reprogram a cell’s functions seemed like an ambitious, distant possibility.

Alex Marson: Yeah, for the past few years we could only use Crispr to make cuts inside of cells and snip away portions of DNA. But now we have a paste function. We showed in a Nature paper in July that if we mix our Crispr components in just the right recipe, we can zap the T cells with a bit of electricity to send in the genome-editing machinery. Then we can make edits that are about 750 nucleotides long at multiple sites, which starts to give us enough flexibility and real estate to give cells dramatic new functions. We’re now able to paste in a new T cell receptor, which is designed to recognize an antigen found on some cancer cells, giving us T cells that attack only the cells that carry that signal.

Parker: This was total science fiction up until very recently! But because of your breakthrough, we can now get into the source code and fundamentally alter the capabilities of not just T cells but any cell type. When I first started reading wired in the 1990s, one of the big ideas was that nanotechnology was going to cure all diseases with little silicon-based robots circulating in our bloodstream. Twenty years later it turns out those tiny machines are actually cells taken from our own bodies, reprogrammed, and put back in.

Alex Marson

Path not taken:
Culinary school

Marson: You’re making me realize that what I’m really trying to do in the lab is create tools that make a more flexible programming system for the field more broadly. That’s what Crispr has the potential to offer: to make it easier to write new code in the language of genetics.

Parker: You know, the advice I would give young people today is not to go into computer science; a much more exciting place to be is the world of biology. It’s going through the same kind of transformation right now that occurred in information technology 20 years ago.

This article appears in the October issue. Subscribe now.

MORE FROM WIRED@25: 1998-2003

• Editor's Letter: Tech has turned the world upside down. Who will shake up the next 25 years?
• Opening essay by Kevin Kelly: How the internet gave all of us superpowers
• Melinda Gates and Shivani Siroya: Giving (micro)credit
• Peter Thiel and Palmer Luckey: Remaking reality
• Jill Tarter and Margaret Turnbull: The E.T. hunters
• Marc Benioff and Boyan Slat: Betting on a cleaner ocean

Join us for a four-day celebration of our anniversary in San Francisco, October 12–15. From a robot petting zoo to provocative onstage conversations, you won't want to miss it. More information at www.Wired.com/25.

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Not for the first time this year, Californians this week donned face masks to protect their lungs from the harmful airborne particles that have smothered the state in a sickly, sooty haze. The pollutants are products of three devastating infernos raging hundreds of miles apart, the largest of which, Butte County's Camp Fire, has swelled to become the deadliest and most destructive in state history. They join the more than 7,500 California wildfires that have this year consumed nearly 1.7-million acres of land—more than any fire season on record. The increasing intensity of California's blazes has many residents of the Golden State wondering: Is the smoke from wildfires also getting worse?

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The WIRED Guide to Climate Change

That's a complicated question. On one hand, data suggests California's fires are burning hotter and consuming more land than they did in the past. "If you use intensity as a proxy for pollution—that is, if you assume stronger fires will produce more emissions like smoke—then by dint of that, yes, there ought to be more smoke," says atmospheric composition scientist Mark Parrington.

A senior researcher at the Copernicus Atmosphere Monitoring Service, Parrington tracks wildfires around the world to better understand their effect on pollution and public health. Most mornings he's in his office by 8 am, downloading the previous 24 hours' worth of fire data from a supercomputer operated by the European Center for Medium-Range Weather Forecasts. The data—thermal infrared radiation measurements from NASA's MODIS instrument—allow him to estimate the intensity of fires burning around the world; how many emissions (like lung-aggravating aerosols and greenhouse gasses like carbon dioxide) they're pumping into the atmosphere; and how those emissions affect global air quality. From his office in Reading, just west of London, he's kept closer tabs on California's current wildfires than most. "You really don't expect to see emissions of this magnitude, this late in the year," Parrington says. "Even on a global scale, it really stood out."

Parrington also compares each day's emissions data to past measurements, which is how he knows that California's current wildfires have pumped more schmutz into the atmosphere than any November blazes on record. In fact, this year's California wildfires have produced more emissions than all but 13 of the past 16 years. "It's not just the Camp Fire, but the wildfires from this summer," Parrington says. "The Carr Fire, the Mendocino Complex Fire—they've been devastating." If the state sees any major wildfires in December (the way it did in 2017), 2018 could become the year with the highest emissions ever recorded for California.

And yet, the question of whether smoke is getting worse is more complicated than many people realize. That's because smoke itself is pretty complex. For starters, it contains well beyond the 40 different "pyrogenic species" Parrington says his analyses account for, which include various forms of carbon, and toxic aromatic compounds like benzene and toluene. The relative and absolute quantities of said species can vary considerably, based on the conditions of the burn—like whether it's wet, dry, or has burned in the past. "All of these factors contribute to how much of those fire emissions get turned into smoke and how the pollutants interact with each other," Parrington says.

Determining how much smoke is actually in the atmosphere, let alone entering people's lungs, is also challenging. Parrington says it requires understanding how smoke interacts with large scale weather conditions like wind, ground temperature, air temperature, and cloud cover. In the Bay Area, for instance, high pressure atmospheric systems tend to produce inversion layers that, like a lid on a shallow pan, keep smoky air close to the ground. Determining the region's air quality has to do not just with the absolute quantity of smoke, but how much of it is is trapped at ground level.

There's also fuel sources to consider, variations in which produce different kinds of smoke. "The fact that more fires are happening at the wildland urban interface means that fires are encountering new materials," says Jessica McCarty, a geographer at Miami University specializing in fire-related air pollution.

When it comes to fuel, McCarty says, fires are agnostic. If it's hot enough, it doesn't care if it's a tree, a house, or your car. But as a rule of thumb, the emissions emanating from a burning shrub are less caustic than those of a burning Subaru. "Wood is far from clean, but it's nothing compared to something like burning rubber, which is downright toxic," McCarty says. Which is why, as people build deeper and deeper into wildland areas, the relevant question isn't just how much pollution these fires producing, but what kind of pollution they're producing.

Answers to both questions, Parrington says, could be found in computational systems like the Copernicus Atmosphere Monitoring service, which is capable of taking many of these variables into account and synthesizing the data across multiples wildfire seasons. CAMs has only been operational for three years, but the data it collects is openly available to scientists around the world who are increasingly interested in nuanced questions about wildland smoke.

For residents of California, answers to those questions can't come soon enough. In the meantime, hang on to any extra air masks you have lying around—there's no telling when you might need them again.

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Today, cannabis continues its slow march toward nationwide decriminalization with voters deciding whether to allow recreational use in Michigan and North Dakota, and for medical purposes in Utah and Missouri. As states keep chipping away at federal prohibition, more consumers will gain access, sure—but so will more researchers who can more easily study this astonishingly complex and still mysterious plant.

At the top of the list of mysteries is how a galaxy of compounds in the plant combine to produce a galaxy of medical (and, of course, recreational) effects. For example, THC feels different when combined it with cannabidiol, or CBD, another naturally occurring compound in cannabis, but the reasons aren’t fully known. It’s called the entourage effect: THC, like a rock star, only reaches its full potential when it rolls with a crew, consisting of hundreds of other compounds in the plant that scientists know about so far.

But the problem with researching a schedule I drug is that the government doesn’t want you to do it. Yet as more states go legal, cannabis continues to climb out of the scientific dark ages. Because it’s not just about giving people a comfortable high, but about developing cannabis into drugs that could treat a massive range of ills.

First, some cannabis basics. THC and CBD are cannabinoids, which means they bind to receptors in the human body’s endocannabinoid system, specifically the CB1 and CB2 receptors. Researchers only discovered the endocannabinoid system in the early 1990s, but it appears to regulate things like mood and immune function.

You may have noticed that cannabis’ effects can differ wildly from experience to experience. Eat a weed brownie, for instance, and the THC goes straight to your liver, where it’s metabolized into 11-hydroxy-THC. That metabolite “has five times the activity at the CB1 receptor, the psychoactive one, as THC itself,” says Jeff Raber, CEO of the Werc Shop, a cannabis lab in California.

That’s why it’s so easy to overdo it with edibles. When you smoke cannabis, the THC at first skips the liver and goes straight to your bloodstream. It’s about five times less potent that way than if you eat cannabis, meaning that chowing down on 10 milligrams of THC is roughly equal to smoking 50 milligrams of the stuff.

Mode of ingestion, then, is a big consideration in the cannabis experience. But so too are factors beyond your control. “We're pretty aware that the endocannabinoid system is not a static picture throughout the day,” says Raber. “Why it changes, what causes those changes—those are other levels of complicated questions.” Cannabis might hit you differently during the day than at night, and can also depend on your mood or whether you’ve eaten.

But that’s not all. THC also interacts with other cannabinoids in your system, and it has a complicated relationship with CBD in particular. Anecdotally, cannabis users have reported that CBD can modulate the psychoactive effects of THC—think of it sort of like an antidote to the paranoia and anxiety that comes with being too high. That might be part of the reason edibles can feel so powerful: If you eat a brownie loaded with just THC, you aren’t getting the CBD you would if you smoked regular old flower. (Not that some manufacturers aren’t also adding CBD to their edibles. CBD is so hot right now, but it's hard to find flower with high CBD. Cultivators have over the decades bred highly intoxicating, THC-rich strains at the expense of CBD.)

With cannabis growing more legitimate as a medicine, researchers are finally putting hard data to these anecdotal reports. They’re beginning to understand how CBD might modulate the often unwelcome effects of THC.

Consider the drug Marinol, a synthetic form of THC available since the 1980s. It’s a good appetite stimulant, but it’s also good at getting patients high and paranoid. “When you just stimulate the CB1 receptor with this pure molecule, it's very intoxicating and patients don't tolerate it very well,” says Adie Wilson-Poe, who researches cannabis for pain management at Washington University in St. Louis.

However, give patients a drug like Sativex—which combines THC with CBD—or even pure cannabis flower or extracts, and they tolerate it much better. “We specifically see that CBD protects against the paranoia and anxiety and the racing heart that THC produces,” Wilson-Poe says.

It all comes back to the psychoactive CB1 receptor. THC is an agonist that fits nicely into CB1, activating it. “CBD can't do that at the CB1, but it does sort of sit in the pocket,” says Wilson-Poe. “It can compete with THC for the spot in the receptor.” Which means that if you take CBD with THC, there may be fewer receptors available for the THC to activate, thus modulating the psychoactive effects, like paranoia.

“But that's probably not the whole story,” Wilson-Poe says, “because CBD has at least 14 distinct mechanisms of action in the central nervous system. So it does a little bit of something at a whole bunch of places, and we probably can't attribute the anti-paranoia or anti-anxiety effects just to CB1 occupancy.”

Now let me add yet another complication to our growing list of complications: THC and CBD are far from alone in the cannabis plant when it comes to medicinal properties. Those two might be anti-inflammatory, for instance, “but if you were to vaporize a whole flower, you'd be consuming potentially a couple dozen anti-inflammatory molecules at once,” says Wilson-Poe. “In this sense I think of whole-plant cannabis as like a multivitamin for inflammation.” (Because there are so many important compounds at play, some researchers prefer the term ensemble effect over entourage effect. “Entourage” makes it sound like everything is supporting the rock star that is THC, when the reality might be more nuanced.)

There might also be medical applications when you don’t want the entourage effect at work. One of THC’s more famous treatments, for instance, is for lowering eye pressure to treat glaucoma. “We found that it works, and THC does a nice job,” says Indiana University, Bloomington researcher Alex Straiker, who studies cannabinoids. “But it's actually blocked by CBD. People often think, oh yeah, CBD and THC work together. But in terms of CB1 receptor signaling, they actually oppose each other, or at least CBD opposes THC.” That’s not to say, though, that CBD isn’t having some sort of beneficial effect on its own when it comes to treating glaucoma.

Plus, there are many other kinds of receptors in the endocannabinoid system that these compounds could be targeting. “It's messy,” Straiker says.

So while CBD seems to mitigate the unfun effects of THC, it also might get in the way of certain medical benefits that THC has to offer. But because there’s seemingly no end to the complexities of cannabis, CBD might also enhance THC’s anti-cancer properties. Research has found that if you apply THC and CBD to cancer cells in the lab, the combination is more effective than THC alone at both inhibiting the growth of those cells and outright killing them. The future of medical cannabis, then, depends in large part on teasing apart the entourage effect—leveraging it in some cases, and maybe breaking up the entourage (or ensemble) when THC or CBD alone is most beneficial.

“We need to understand which constellations of plant chemistry are best suited for which indications and which kinds of patients, and which form of the CB1 receptor you happen to carry, because there are lots of mutations in that gene,” says Wilson-Poe. “So understanding these mechanisms is absolutely crucial for providing these patients with personalized medicine that alleviates their symptoms without producing the unwanted side effects.”

Hate to do this, but we’ve got one last problem. For decades, cannabis users have claimed that different strains of cannabis produce different effects—maybe it makes them sleepy, maybe it gives them energy. And that’s been true even as CBD was largely bred out of cannabis in North America in favor of THC. “Well, if they're all high THC, it's got to be from something else,” says Ethan Russo, director of research and development at the International Cannabis and Cannabinoids Institute, who studies the entourage effect. “And that something else is terpenoids.”

Yes, another member of the entourage. Unlike THC and CBD, you can find terpenoids not just in cannabis, but across the plant kingdom. They’re handy little molecules that plants use to ward off insects, and they’re what give cannabis that characteristic smell (same for terpenoids in lemons and pine needles).

And science knows what some terpenoids found in cannabis do pharmacologically in the brain. For example, linalool is one that has sedating and anti-anxiety properties. “So it might make sense that when you combine its anti-anxiety effect with that of cannabidiol [CBD], then they boost each other,” says Russo.

The entourage effect, the ensemble effect—whatever you want to call it, the phenomenon might get more complicated before it gets clearer. But researchers continue to tease apart the chemistry of cannabis, unlocking its true potential as a medicine. Mystery … almost solved.