NOVA

Can forests help cool the planet? Follow scientists working in spectacular forest landscapes in Costa Rica, Brazil, Australia, and beyond as they try to untangle complex networks of trees, fungi, and creatures large and small – all in a quest to tackle the twin threats of climate change and species extinction.

Black Americans are nearly twice as likely to have high blood pressure, diabetes, and heart disease than White Americans, and their life expectancy is about five years shorter. Why? In this special feature-length documentary, Oscar-nominated filmmaker Stanley Nelson investigates the dramatic health disparities in the U.S., even as scientists confirm that there are no meaningful genetic differences between races. From the deep history of pseudoscientific beliefs about race that still permeate modern medicine, to the latest research on how experiencing discrimination can directly damage the body's DNA and biology, "Critical Condition" reveals the factors behind the health crisis facing Black Americans.

Surprisingly little is known about the behavior of cars and drivers in uncontrolled, real-world accidents, despite rigorous testing in laboratory-controlled crashes. Now, a first-of-its-kind experiment aims to discover what really happens in a multi-vehicle pileup and how cars and driving could be made safer.

In the first episode of this two-part special, go behind the scenes as scientists make a series of high-stakes decisions to ensure the ambitious experiment goes off without a hitch. They only have one shot. The plan is for 8 drivers to drive 8 different cars by remote control at 70 mph down a hazardous straightaway. But how can they best represent real-world conditions to create a crash, especially when the drivers have no idea what's about to happen? How do they ensure that the remote drivers feel natural behind the wheel? And what is needed to fully capture every data-point possible? The intense preparation for the most ambitious crash test ever conducted culminates in the moment of truth as the cars barrel down an airport tarmac and collide in a massive, multi-vehicle pile-up.

Surprisingly little is known about the behavior of cars and drivers in uncontrolled, real-world accidents, despite rigorous testing in laboratory-controlled crashes. Now, a first-of-its-kind experiment aims to discover what really happens in a multi-vehicle pileup and how cars and driving could be made safer.

In the second episode of this two-part special, forensic analysis is put to the test. Real-life crash scene investigations have very little data to work with, so are they accurate? And what can we learn about car safety when there is actual data to show exactly what happened? Follow scientists, engineers, and accident investigators as they analyze a treasure trove of data – more than they've ever been able to work with before. Interviews with drivers offer valuable clues into what they saw and how they reacted, and a LIDAR scan of the scene is stitched together into a digital version of the entire event that can be analyzed millisecond by millisecond. In this unprecedented look at a major multi-vehicle accident, discover insights about driver behavior and vehicle design that could save lives.