Q: Does the Amazon produce 20% of the world’s oxygen?
A: No. Scientists estimate the percentage is closer to 6 to 9%, and the Amazon ultimately consumes nearly all of that oxygen itself.
Q: When is the human heart fully developed, and when are heartbeats audible during pregnancy?
A: A developing heart has all of its primary structures after about nine weeks of pregnancy. Some forms of ultrasound can detect cardiac activity in an embryo in the sixth week, but a heartbeat wouldn’t be audible until about 10 weeks on a Doppler fetal monitor.
Q: Does the National Institutes of Health fund research on human-animal chimeras, or organisms that are part-human, part-other animal?
A: With some exceptions, the NIH doesn’t fund research on human-animal chimeras. But the agency has proposed a rule to widen the scope of research it funds in this area.
Q: Have scientists confirmed that e-cigarettes cause an incurable respiratory disease called “popcorn lung”?
A: No. The vapor of some e-cigarettes contains a chemical associated with popcorn lung, and a case report suggests a possible link. But there’s not enough evidence to conclude the vapors cause the disease.