PBS NewsHour - Science

Among the millions of real people tweeting about the presidential race, there are also a lot accounts operated by fake people, or “bots.” Politicians and regular users alike use these accounts to increase their follower bases and push messages. Science correspondent Miles O’Brien reports on how computer scientists can analyze Twitter handles to determine whether or not they are bots.

To profitably produce corn in on Midwestern farms, nitrogen must be added to the soil. But the practice has an unwanted environmental impact: water contamination. A University of Nebraska professor thinks he may have a solution. Special correspondent Ariana Brocious of Harvest Public Media in Nebraska reports.

Portland, Oregon, prides itself on being very focused on the environment. So many people were shocked to discover that certain neighborhoods contain high levels of toxic metals. Scientists made the discovery when ordinary moss samples taken from all over town revealed the unexpected contamination. Special correspondent Cat Wise reports on how it led to some significant changes in the city.

A former banana plantation in Costa Rica is now a school -- but the curriculum still involves growing fruit. EARTH University, founded in 1992, trains students from developing nations in responsible, sustainable agriculture. Graduates then apply their knowledge in their own countries, hoping to improve both the economy and the environment. Special Correspondent Fred de Sam Lazaro reports.

The international climate agreement is set to take effect next month, after the European Parliament ratified it earlier this week. Hillary Clinton supports the Paris accord but Donald Trump says if elected, he would withdraw from it. Judy Woodruff speaks with climatologist Gavin Schmidt for more on what will take effect under the treaty and what climate science says about global warming.

Florida's battle against the outbreak of Zika is intensifying as the number of cases climbs. The state currently has 940 documented instances of the virus, with 230 in Miami-Dade County alone. Efforts to contain the spread of the disease focus on mosquito control and avoidance, but many details about Zika remain a mystery. For more on the outbreak, William Brangham reports from Miami.

A trio of scientists won the Nobel Prize in Chemistry for creating some of the world’s tiniest machines. Their nanorobots use extremely controlled movements to perform tasks that the creators hope will one day be useful in the world of medicine. Science correspondent Miles O'Brien joins Hari Sreenivasan to discuss these mini machines and the other science and medicine Nobels awarded this week.

Our love/hate relationship with lead is as old as history itself. The origin of "plumbing" comes from the Latin word for lead. But only in the 1970s did we realize the consequences of even low doses of the hazardous metal, and by then it was in our pipes, our paint and our fuel. Science correspondent Miles O’Brien examines the lasting health consequences.

In light of the recent bombings in New York and New Jersey, science correspondent Miles O'Brien takes a look at a new technology that is increasingly being used by law enforcement: bomb-disarming robots. Operated from a safe distance, these robots can blast through car windows and even kill, raising ethical issues about how they should be used.

In our NewsHour Shares moment of the day, we visit the rural pastures of Cle Elum, in Washington state, where seven former lab chimpanzees are honorary citizens. Known throughout the world as the “Cle Elum 7,” these chimps have been given a second chance to live out their lives in the wild. We visit these chimps in their new home.

Many see the beach as a quiet place for relaxation. But for the animals living under the water’s surface, motorized vehicles and other human-made technology can make life unbearably noisy. The problem is that many species rely on sound as communication and the noise levels are drowning them out. Special correspondent Cat Wise reports on one company aiming to solve the problem.

According to the National Audubon Society, climate change poses a serious threat to a large number of North America’s birds. But a street art project in New York City aims to call attention to their plight by creating large-scale murals of the birds. NewsHour Weekend Correspondent Megan Thompson reports.

There is probably no greater divergence between Hillary Clinton and Donald Trump’s views than on climate change. Clinton thinks it poses grave danger, while Trump thinks it’s a fantasy. William Brangham asks The New York Times’ Coral Davenport and The Washington Post’s Chris Mooney to predict what climate policy would look like under both administrations.

How do you deter people from being seduced by messages of extremism on social media? Science correspondent Miles O’Brien looks at some of the strategies, including videos that provide a counter-narrative to the Islamic State and a computer program that uses digital signatures to track the movement of images on the internet.

Take a look at the room 9/11 built: The operations center at the National Counterterrorism Center aggregates data in hopes that analysts will be able to predict the next terrorist attack. With the advent of “social media intelligence,” answers are everywhere, but the challenge is piecing them together. Science correspondent Miles O’Brien reports.