Category: The Conversation

Source: The Conversation – USA – By Vikash V. Gayah, Associate Professor of Civil Engineering, Penn State

More than 60% of traffic collisions at intersections involve left turns. Some U.S. cities – including San Francisco, Salt Lake City and Birmingham, Alabama – are restricting left turns.

Dr. Vikash Gayah, a professor of civil engineering at Penn State University and the interim director of the Larson Transportation Institute, discusses how left turns at intersections cause accidents, make traffic worse and use more gas.

The Conversation has collaborated with SciLine to bring you highlights from the discussion, edited for brevity and clarity.

How dangerous are left turns at intersections?

Vikash Gayah: When you make a left turn, you have to cross oncoming traffic. When you have a green light, you need to wait for a gap in the oncoming traffic before turning left. If you misjudge when you decide to turn, you could hit the oncoming traffic, or be hit by it. That’s an angle crash, one of the most dangerous types of crashes.

Also, the driver of the left-turning vehicle is typically looking at oncoming traffic. But pedestrians may be crossing the street they’re turning on to. Often the driver doesn’t see the pedestrians, and that too can cause a serious accident.

On the other hand, right turns require merging into traffic, but they’re not conflicting directly with traffic. So right turns are much, much safer than left turns.

What are the statistics on the unique dangers of left turns?

Gayah: Approximately 40% of all crashes occur at intersections − 50% of those crashes involve a serious injury, and 20% involve a fatality.

About 61% of the crashes at intersections involve a left turn. Left-hand turns are generally the least frequent movement at an intersection, so that 61% is a lot.

Why are left turns inefficient for traffic flow?

Gayah: When left-turning vehicles are waiting for the gap, they can block other lanes from moving, particularly when several vehicles are waiting to turn left.

Instead of the solid green light, many intersections use the green arrow to let left-turning vehicles move. But to do that, all other movements at the intersection have to stop. Stopping all other traffic just to serve a few left turns makes the intersection less efficient.

Also, every time you move to another “phase” of traffic – like the green arrow – the intersection has a brief period of time when all the lights are red. Traffic engineers call that an all-red time, and that’s when the intersection is not serving any vehicles. All-red time is two to three seconds per phase change, and that wasted time adds up quickly to further make the intersection less efficient.

What restrictions have been tried in different cities?

Gayah: When a downtown is not very busy – in the off-peak periods – allowing left turns is fine because you don’t need that additional ability to move vehicles at each intersection.

Some cities are implementing signs that say no left turns at intersections from 7 to 9, which is the morning peak period, or 4 to 6, which is the afternoon peak period. In San Francisco, for example, Van Ness Avenue restricts left turns during peak periods.

But cities aren’t implementing these restrictions on a larger scale. Restrictions are more along individual corridors or isolated intersections instead of essentially the entire downtown, where possible. That would make the downtown street network more efficient.

Roundabouts are one approach to avoiding left turns.

Gayah: Roundabouts are safe because there’s no longer a need to cross opposing traffic. Everyone circulates in the same direction. You find where you need to go and then exit.

But restricting left turns, in general, is more efficient. Roundabouts aren’t as efficient when it’s busier. The roundabout gets full, which can cause a gridlock, and no vehicle can move. Traditional intersections are less prone to gridlock.

Roundabouts also take up more space. Installing a roundabout might mean expanding the intersection. In some downtowns, that means tearing down buildings or removing sidewalks. Restricting left turns only requires a sign that says “no left turns” or “no left turns during peak periods.” That’s it.

What are the benefits to banning left turns in urban areas?

Gayah: Any way you cut it, eliminating left turns will result in longer travel distances. I’ll have to travel a longer distance to get to where I need to go. The worst case is having to circle the block. I’m actually traveling four extra block lengths to get to where I need to go.

But not all trips require circling the block. In a typical downtown, each trip will be about one block length longer on average. That’s not a lot of extra distance. And that extra driving is more than offset by the fact that each intersection with banned left turns is now moving more vehicles. Which means every time you’re at an intersection, you wait less time, on average. So you travel a slightly longer distance but get to where you’re going more quickly.

Does avoiding left turns improve fuel efficiency?

Gayah: Our research found that even though vehicles travel longer distances on average with the restricted left turns, they spend less fuel – about 10% to 15% less per trip – because they don’t stop as much at intersections.

This is why UPS and other fleets route their vehicles to avoid left turns. There’s less idling and fewer stops.

Do you think banning left turns could become widely accepted?

Gayah: It’s a new strategy, so it’s uncomfortable for some people. But when they get to their destination faster, I think people will latch onto it.

Watch the full interview to hear more.

SciLine is a free service based at the American Association for the Advancement of Science, a nonprofit that helps journalists include scientific evidence and experts in their news stories.

Vikash V. Gayah’s research has been funded by various State Departments of Transportation (including Pennsylvania, Wisconsin, Washington State, Montana, South Dakota and North Carolina), US Department of Transportation (via the Mineta National Transit Research Consortium, the Mid-Atlantic Universities Transportation Center, and the Center for Integrated Asset Management for Multimodal Transportation Infrastructure Systems), Federal Highway Administration, National Cooperative Highway Research Program, and National Science Foundation..

– ref. Here’s a way to save lives, curb traffic jams and make commutes faster and easier − ban left turns at intersections – https://theconversation.com/heres-a-way-to-save-lives-curb-traffic-jams-and-make-commutes-faster-and-easier-ban-left-turns-at-intersections-257877

Source: The Conversation – USA – By Adi Foord, Assistant Professor of Astronomy and Astrophysics, University of Maryland, Baltimore County

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

How does the camera on the James Webb Space Telescope work and see so far out? – Kieran G., age 12, Minnesota

Imagine a camera so powerful it can see light from galaxies that formed more than 13 billion years ago. That’s exactly what NASA’s James Webb Space Telescope is built to do.

Since it launched in December 2021, Webb has been orbiting more than a million miles from Earth, capturing breathtaking images of deep space. But how does it actually work? And how can it see so far? The secret lies in its powerful cameras – especially ones that don’t see light the way our eyes do.

I’m an astrophysicist who studies galaxies and supermassive black holes, and the Webb telescope is an incredible tool for observing some of the earliest galaxies and black holes in the universe.

When Webb takes a picture of a distant galaxy, astronomers like me are actually seeing what that galaxy looked like billions of years ago. The light from that galaxy has been traveling across space for the billions of years it takes to reach the telescope’s mirror. It’s like having a time machine that takes snapshots of the early universe.

By using a giant mirror to collect ancient light, Webb has been discovering new secrets about the universe.

A telescope that sees heat

Unlike regular cameras or even the Hubble Space Telescope, which take images of visible light, Webb is designed to see a kind of light that’s invisible to your eyes: infrared light. Infrared light has longer wavelengths than visible light, which is why our eyes can’t detect it. But with the right instruments, Webb can capture infrared light to study some of the earliest and most distant objects in the universe.

Although the human eye cannot see it, people can detect infrared light as a form of heat using specialized technology, such as infrared cameras or thermal sensors. For example, night-vision goggles use infrared light to detect warm objects in the dark. Webb uses the same idea to study stars, galaxies and planets.

Why infrared? When visible light from faraway galaxies travels across the universe, it stretches out. This is because the universe is expanding. That stretching turns visible light into infrared light. So, the most distant galaxies in space don’t shine in visible light anymore – they glow in faint infrared. That’s the light Webb is built to detect.

A golden mirror to gather the faintest glow

Before the light reaches the cameras, it first has to be collected by the Webb telescope’s enormous golden mirror. This mirror is over 21 feet (6.5 meters) wide and made of 18 smaller mirror pieces that fit together like a honeycomb. It’s coated in a thin layer of real gold – not just to look fancy, but because gold reflects infrared light extremely well.

The mirror gathers light from deep space and reflects it into the telescope’s instruments. The bigger the mirror, the more light it can collect – and the farther it can see. Webb’s mirror is the largest ever launched into space.

Inside the cameras: NIRCam and MIRI

The most important “eyes” of the telescope are two science instruments that act like cameras: NIRCam and MIRI.

NIRCam stands for near-infrared camera. It’s the primary camera on Webb and takes stunning images of galaxies and stars. It also has a coronagraph – a device that blocks out starlight so it can photograph very faint objects near bright sources, such as planets orbiting bright stars.

NIRCam works by imaging near-infrared light, the type closest to what human eyes can almost see, and splitting it into different wavelengths. This helps scientists learn not just what something looks like but what it’s made of. Different materials in space absorb and emit infrared light at specific wavelengths, creating a kind of unique chemical fingerprint. By studying these fingerprints, scientists can uncover the properties of distant stars and galaxies.

MIRI, or the mid-infrared instrument, detects longer infrared wavelengths, which are especially useful for spotting cooler and dustier objects, such as stars that are still forming inside clouds of gas. MIRI can even help find clues about the types of molecules in the atmospheres of planets that might support life.

Both cameras are far more sensitive than the standard cameras used on Earth. NIRCam and MIRI can detect the tiniest amounts of heat from billions of light-years away. If you had Webb’s NIRCam as your eyes, you could see the heat from a bumblebee on the Moon. That’s how sensitive it is.

Because Webb is trying to detect faint heat from faraway objects, it needs to keep itself as cold as possible. That’s why it carries a giant sun shield about the size of a tennis court. This five-layer sun shield blocks heat from the Sun, Earth and even the Moon, helping Webb stay incredibly cold: around -370 degrees F (-223 degrees C).

MIRI needs to be even colder. It has its own special refrigerator, called a cryocooler, to keep it chilled to nearly -447 degrees F (-266 degrees C). If Webb were even a little warm, its own heat would drown out the distant signals it’s trying to detect.

Turning space light into pictures

Once light reaches the Webb telescope’s cameras, it hits sensors called detectors. These detectors don’t capture regular photos like a phone camera. Instead, they convert the incoming infrared light into digital data. That data is then sent back to Earth, where scientists process it into full-color images.

The colors we see in Webb’s pictures aren’t what the camera “sees” directly. Because infrared light is invisible, scientists assign colors to different wavelengths to help us understand what’s in the image. These processed images help show the structure, age and composition of galaxies, stars and more.

By using a giant mirror to collect invisible infrared light and sending it to super-cold cameras, Webb lets us see galaxies that formed just after the universe began.

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

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

Adi Foord does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. How can the James Webb Space Telescope see so far? – https://theconversation.com/how-can-the-james-webb-space-telescope-see-so-far-257421

Source: The Conversation – USA – By Marc Zimmer, Professor of Chemistry, Connecticut College

Despite representing only 4% of the world’s population, the United States accounts for over half of science Nobel Prizes awarded since 2000, hosts seven of The Times Higher Education Top 10 science universities, and incubates firms such as Alphabet (Google), Meta and Pfizer that turn federally funded discoveries into billion-dollar markets.

The domestic STEM talent pool alone cannot sustain this research output. The U.S. is reliant on a steady and strong influx of foreign scientists – a brain gain. In 2021, foreign-born people constituted 43% of doctorate-level scientists and engineers in the U.S. They make up a significant share of America’s elite researchers: Since 2000, 37 of the 104 U.S. Nobel laureates in the hard sciences, more than a third, were born outside the country.

China, the U.S.’s largest competitor in science, technology, engineering and math endeavors, has a population that is 4.1 times larger than that of the U.S. and so has a larger pool of homegrown talent. Each year, three times as many Chinese citizens (77,000) are awarded STEM Ph.D.s as American citizens (23,000).

To remain preeminent, the U.S. will need to keep attracting exceptional foreign graduate students, budding entrepreneurs and established scientific leaders.

Funding and visa policies could flip gain to drain

This scientific brain gain is being threatened by the Trump administration, which is using federal research funding, scholarships and fellowships as leverage against universities, freezing billions of dollars in grants and contracts to force compliance with its ideological agenda. Its ad hoc approach has been described by higher education leaders as “unprecedented and deeply disturbing,” and a Reagan-appointed judge ruled that 400 National Institutes of Health grants be reinstated because their terminations were “bereft of reasoning, virtually in their entirety.”

Experts caution that these moves not only risk immediate harm to scientific progress and academic freedom but also erode the public’s trust in science and education, with long-term implications for the nation’s prosperity and security.

Citing national security concerns, the White House has also targeted visas for Harvard University’s international students and instructed embassies worldwide to halt visa interviews for all international students, citing national security and alleged institutional misconduct. Against a backdrop of court injunctions and legal appeals, the government continues its heightened “national-security” vetting, so thousands of international scholars remain in limbo.

These measures, combined with travel bans, intensified scrutiny and revocations of existing visas, have disrupted research collaborations and threaten the nation’s continued status as a global leader in science and innovation.

What US misses with fewer foreign scientists

The U.S. research brain gain starts with the 281,000 foreign STEM graduate students and 38,000 foreign STEM postdoctoral scholars who annually come to the U.S. I am one of them. After earning my bachelor’s and master’s degrees in South Africa, I left in 1986 to avoid the apartheid‑era military service, completed my chemistry doctorate and postdoc in the U.S., and joined the United States’ brain gain. It’s an opportunity today’s visa climate might have denied me.

Incentives for the best and brightest foreign science students to come to the U.S. are diminishing at the same time its competitors are increasing their efforts to attract the strongest STEM researchers. For instance, the University of Hong Kong is courting stranded Harvard students with dedicated scholarships, housing and credit-transfer help. A French university program, Safe Place for Science, drew so many American job applicants that it had to shut the portal early. And a Portuguese institute reports a tenfold surge in inquiries from U.S.-based junior faculty.

Immigrants import new ways of thinking to their research labs. They come from other cultures and have learned their science in different educational systems, which place different emphases on rote learning, historical understanding and interdisciplinary research. They often bring an alternative perspective that a homogeneous scientific community cannot match.

Immigrants also help move discoveries from the lab to the marketplace. Foreign-born inventors file patents at a higher per‑capita rate than their domestic peers and are 80% more likely to launch a company. Such firms create roughly 50% more jobs than enterprises founded by native-born entrepreneurs and pay wages that are, on average, one percentage point higher.

The economic stakes are high. Growth models suggest that scientific advances now account for a majority of productivity gains in high‑income countries.

L. Rafael Reif, the former president of MIT, called international talent the “oxygen” of U.S. innovation; restricting visas chokes that supply. Ongoing cuts and uncertainties in federal funding and visa policy now jeopardize America’s scientific leadership and with it the nation’s long‑term economic growth.

Marc Zimmer received funding from NIH and NSF.

– ref. Turbulent research landscape imperils US brain gain − and ultimately American prosperity – https://theconversation.com/turbulent-research-landscape-imperils-us-brain-gain-and-ultimately-american-prosperity-258537

Source: The Conversation – USA – By Lisa Schirch, Professor of the Practice of Peace Studies, University of Notre Dame

Every design choice that social media platforms make nudges users toward certain actions, values and emotional states.

It is a design choice to offer a news feed that combines verified news sources with conspiracy blogs – interspersed with photos of a family picnic – with no distinction between these very different types of information. It is a design choice to use algorithms that find the most emotional or outrageous content to show users, hoping it keeps them online. And it is a design choice to send bright red notifications, keeping people in a state of expectation for the next photo or juicy piece of gossip.

Platform design is a silent pilot steering human behavior.

Social media platforms are bringing massive changes to how people get their news and how they communicate and behave. For example, the “endless scroll” is a design feature that aims to keep users scrolling and never reaching the bottom of a page where they might decide to pause.

I’m a political scientist who researches aspects of technology that support democracy and social cohesion, and I’ve observed how the design of social media platforms affects them.

Democracy is in crisis globally, and technology is playing a role. Most large platforms optimize their designs for profit, not community or democracy. Increasingly, Big Tech is siding with autocrats, and the platforms’ designs help keep society under control.

There are alternatives, however. Some companies design online platforms to defend democratic values.

Optimized for profit

A handful of tech billionaires dominate the global information ecosystem. Without public accountability or oversight, they determine what news shows up on your feed and what data they collect and share.

Social media companies say they are in the business of connecting people, but they make most of their money as data brokers and advertising firms. Time spent on platforms translates to profit. The more time you spend online, the more ads you see and the more data they can collect from you.

This ad-based business model demands designs that encourage endless scrolling, social comparison and emotional engagement. Platforms routinely claim they merely reflect user behavior, yet internal documents and whistleblower accounts have shown that toxic content often gets a boost because it captures people’s attention.

Tech companies design platforms based on extensive psychological research. Examples include flashing notifications that make your phone jump and squeak, colorful rewards when others like your posts, and algorithms that push out the most emotional content to stimulate your most base emotions of anger, shame or glee.

Optimizing designs for user engagement undermines mental health and society. Social media sites favor hype and scandal over factual accuracy, and public manipulation over designing for safety, privacy and user agency. The resulting prevalence of polarizing false and deceptive information is corrosive to democracy.

Many analysts identified these problems nearly a decade ago. But now there is a new threat: Some tech executives are looking to capture political power to advance a new era of techno-autocracy.

Optimized for political power

A techno-autocracy is a political system where an authoritarian government uses technology to control its population. Techno-autocrats spread disinformation and propaganda, using fear tactics to demonize others and distract from corruption. They leverage massive amounts of data, artificial intelligence and surveillance to censor opponents.

For example, China uses technology to monitor and surveil its population with public cameras. Chinese platforms like WeChat and Weibo automatically scan, block or delete messages and posts for sensitive words like “freedom of speech.” Russia promotes domestic platforms like VK that are closely monitored and partly owned by state-linked entities that use it to promote political propaganda.

Over a decade ago, tech billionaires like Elon Musk and Peter Thiel, and now Vice President JD Vance, began aligning with far-right political philosophers like Curtis Yarvin. They argue that democracy impedes innovation, favoring concentrated decision-making in corporate-controlled mini-states governed through surveillance. Embracing this philosophy of techno-autocracy, they moved from funding and designing the internet to reshaping government.

Techno-autocrats weaponize social media platforms as part of their plan to dismantle democratic institutions.

The political capture of both X and Meta also have consequences for global security. At Meta, Mark Zuckerberg removed barriers to right-wing propaganda and openly endorsed President Donald Trump’s agenda. Musk changed X’s algorithm to highlight right-wing content, including Russian propaganda.

Designing tech for democracy

Recognizing the power that platform design has on society, some companies are designing new civic participation platforms that support rather than undermine society’s access to verified information and places for public deliberation. These platforms offer design features that big tech companies could adopt for improving democratic engagement that can help counter techno-autocracy.

In 2014, a group of technologists founded Pol.is, an open-source technology for hosting public deliberation that leverages data science. Pol.is enables participants to propose and vote on policy ideas using what they call “computational democracy.” The Pol.is design avoids personal attacks by having no “reply” button. It offers no flashy newsfeed, and it uses algorithms that identify areas of agreement and disagreement to help people make sense of a diversity of opinions. A prompt question asks for people to offer ideas and vote up or down on other ideas. People participate anonymously, helping to keep the focus on the issues and not the people.

Taiwan used the Pol.is platform to enable mass civic engagement in the 2014 democracy movement. The U.K. government’s Collective Intelligence Lab used the platform to generate public discussion and generate new policy proposals on climate and health care policies. In Finland, a public foundation called Sitra uses Pol.is in its “What do you think, Finland?” public dialogues.

Barcelona, Spain, designed a new participatory democracy platform called Decidim in 2017. Now used throughout Spain and Europe, Decidim enables citizens to collaboratively propose, debate and decide on public policies and budgets through transparent digital processes.

Nobel Peace Laureate Maria Ressa founded Rappler Communities in 2023, a social network in the Philippines that combines journalism, community and technology. It aims to restore trust in institutions by providing safe spaces for exchanging ideas and connecting with neighbors, journalists and civil society groups. Rappler Communities offers the public data privacy and portability, meaning you can take your information – like photos, contacts or messages – from one app or platform and transfer it to another. These design features are not available on the major social media platforms.

Tech designed for improving public dialogue is possible – and can even work in the middle of a war zone. In 2024, the Alliance for Middle East Peace began using Remesh.ai, an AI-based platform, to find areas of common ground between Israelis and Palestinians in order to advance the idea of a public peace process and identify elements of a ceasefire agreement.

Platform designs are a form of social engineering to achieve some sort of goal – because they shape how people behave, think and interact – often invisibly. Designing more and better platforms to support democracy can be an antidote to the wave of global autocracy that is increasingly bolstered by tech platforms that tighten public control.

Lisa Schirch receives funding from the Ford Foundation. I know the founder of Pol.is and Remesh platforms, mentioned in this article, as well as Maria Ressa of Rappler Communities.

I will not benefit in any way from describing their work.

– ref. Social media can support or undermine democracy – it comes down to how it’s designed – https://theconversation.com/social-media-can-support-or-undermine-democracy-it-comes-down-to-how-its-designed-257103