Explore an interactive representation of the process of science. Home Glossary Search Understanding Science 101 For teachers Resource library
Asteroids and dinosaurs
page 1 of 10
nextprevious
  Asteroids and dinosaurs: Unexpected twists and an unfinished story
Plate tectonics might seem like a routine topic from a 7th grade textbook, but in the 1970s, plate tectonics was cutting-edge science. The theory had only gained widespread acceptance over the previous ten years and subsequently attracted scads of scientists looking to open up new intellectual frontiers. Walter Alvarez was one of them, but his research into plate tectonics was destined to be sidelined. An intriguing observation would eventually lead him, his collaborators, and the rest of science on an intellectual journey across geology, chemistry, paleontology, and atmospheric science — towards solving one of the great mysteries in Earth's history: What happened to the dinosaurs?

At left, Luis and Walter Alvarez stand by the rock layers near Gubbio, Italy, where unusually high traces of iridium were found at the Cretaceous-Tertiary boundary. Was this evidence that of an ancient supernova or an ancient asteroid impact?  And what, if anything did it have to do with the dinosaur extinction?
At left, Luis and Walter Alvarez stand by the rock layers near Gubbio, Italy, where unusually high traces of iridium were found at the Cretaceous-Tertiary boundary. Was this evidence of an ancient supernova or an ancient asteroid impact? And what, if anything, did it have to do with the dinosaur extinction?

This case study highlights these aspects of the nature of science:

  • Science can test hypotheses about events that happened long ago.
  • Scientific ideas are tested with multiple lines of evidence.
  • Science relies on communication within a diverse scientific community.
  • The process of science is non-linear, unpredictable, and ongoing.
  • Science often investigates problems that require collaboration from those in many different disciplines.
This entire section is available as a PDF download.

Are dinosaurs really completely extinct?

Well, most dinosaurs are. But one lesser known lineage of dinosaurs survived the KT extinction and might be fluttering outside your window at this moment: birds! Many separate lines of evidence suggest that modern birds are a branch off the dinosaur family tree — they're closely related to T. rex — which technically makes them dinosaurs. So the "dinosaur extinction" really refers to the 65-million-year-old extinction event that killed off all dinosaurs except birds.

take a sidetrip
Throughout this story, we'll trace the path through the process of science that scientists took in their investigation. To review this process, visit The real process of science.

key points
Use this story to introduce your students to the Science Flowchart. Check out the middle school or high school version of the activity.




Luis and Walter Alvarez photo from Ernest Orlando Lawrence Berkeley National Laboratory; supernova image courtesy of NASA/Swift/S. Immler; asteroid impact image courtesy of NASA Ames

Home | About | Copyright | Credits and Collaborations | Contact | Subscribe | Translations