The main aim of this lesson is to show students that distances may be determined without a meter stick—a concept fundamental to such measurements in astronomy. It introduces students to the main concepts behind the first rung of what astronomers call the distance ladder. The four main learning objectives are the following: 1) Explore, in practice, a means of measuring distances without what we most often consider the “direct” means: a meter stick; 2) Understand the limits of a method through the exploration of uncertainties; 3) Understand in the particular method used, the relationship between baseline and the accuracy of the measurement; and 4) Understand the astronomical applications and implications of the method and its limits. Students should be able to use trigonometry and know the relation between trigonometric functions and the triangle. A knowledge of derivatives is also needed to obtain the expression for the uncertainty on the distance measured. Students will need cardboard cut into disks. The number of disks is essentially equal to half the students in the class. Two straight drink straws and one pin per disk. Students will also need a protractor. The lesson should not take more than 50 minutes to complete if the students have the mathematical ability mentioned above. This lesson is complimentary to the BLOSSOMS lesson, "The Parallax Activity." The two lessons could be used sequentially - this one being more advanced - or they could be used separately.

In this Cyberchase video segment, the CyberSquad must measure the length of the rope that will lower Digit from the ceiling to remove the voice box from a statue of Hacker.

This art history video discussion examines Medea Sarcophagus, 140 - 150 C.E., marble (Altes Museum, Berlin).

In this lesson students will see the different types of evidence scientists use to understand evolutionary relationships among organisms. They will first practice by using shared physical characteristics to predict relationships among members of the cat family and then use this approach to predict primate relationships. They will compare their predictions to evidence provided by analyzing amino acid sequences and build a phylogenetic tree based on these sequences. Finally, they will look at the tree in the context of time in order to see divergence times.

This short video and interactive assessment activity is designed to teach fifth graders about converting meters to centimeters.

This short video and interactive assessment activity is designed to teach fifth graders about converting kilometers to meters.

This short video and interactive assessment activity is designed to teach fifth graders about converting meters to millimeters.

This short video and interactive assessment activity is designed to teach first graders about how big is a meter?.

This short video and interactive assessment activity is designed to teach fourth graders about introduction to metric measures: how big is a meter?.

This Protein Purification video lesson is intended to give students some insight into the process and tools that scientists and engineers use to explore proteins. It is designed to extend the knowledge of students who are already somewhat sophisticated and who have a good understanding of basic biology. The question that motivates this lesson is, ''what makes two cell types different?'' and this question is posed in several ways. Such scientific reasoning raises the experimental question: how could you study just a subset of specialized proteins that distinguish one cell type from another? Two techniques useful in this regard are considered in the lesson.

This short video and interactive assessment activity is designed to teach fourth graders about adding lengths in meters.

This short video and interactive assessment activity is designed to give fourth graders an overview of conversion of capacity units (metric units).

This short video and interactive assessment activity is designed to give fifth graders an overview of conversion of capacity units (metric units).

This short video and interactive assessment activity is designed to teach fifth graders about converting centimeters to millimeters with decimals.

This short video and interactive assessment activity is designed to teach fifth graders about comparing meters, centimeters, and millimeters.

This short video and interactive assessment activity is designed to teach fourth graders about multiplication of lengths (metric units).

This short video and interactive assessment activity is designed to teach fourth graders about subtracting lengths in meters.

In this art history video discussion Beth Harris and Steven Zucker consider Michael Pacher's "Saint Wolfgang Altarpiece," 1471-81, polychrome pine, linden, gilding, and oil (sculpture and painting). Parish Church, Sankt Wolfgang, Austria.

This art history video discussion examines Michelangelo's "Laurentian Library" (vestibule and reading room), begun 1524, opened 1571, San Lorenzo, Florence.

This art history video discussion looks at Michelangelo's Ceiling of the Sistine Chapel, 1508-12 (Vatican, Rome).