In this 7-minute video astronomer Dr Meghan Gray explains the relationship of the Earth's rotation and its revolution around the Sun, resulting in the need to add an extra day to our calendar every four years. She describes additional adjustments required to keep our calendar aligned with the Earth's movements. Dr Gray explains the Julian date and its usefulness.

This NCTM resource presents a problem involving distance, rate and time. The challenge asks students to determine the number of days it would take a tern to migrate from the Arctic to the Antarctic given a constant rate of speed. Hints and prompts for students and additional "Try These" challenges about distance and speed are also included. Students may also check their answer and see steps to solve the problem. PDF files of the challenges are linked from the site for printing.

In this outdoor biology and math activity, learners estimate the size of a population of organisms too numerous to count. In a process similar to that used by real field biologists, learners count all the "organisms" (beans) scattered in a small, measured area known as a quadrat, then use that count as the basis for estimating the total population in the whole study site. Learners also examine sources of error while using this estimation technique.

This Cyberchase video segment features Bianca, who must figure out the fastest route to a movie premiere.

This brief article describes the historical methods of marking and measuring time. Among the instruments and methods discussed are sundials, water clocks, celestial motions, and mechanical clocks. Included are descriptions of the sources of inaccuracies of these methods. Links to related resources and a separate page of pedagogical notes are provided.

This activity (page 2 of the PDF) is a full inquiry investigation into decomposition. Groups of learners will carefully observe and record the appearance of items, such as an apple, that can decompose, taking weights, measurements, and noting other physical markings. The items are then buried in buckets of various earth materials for at least two weeks. Learners will then dig up the objects to inspect, record observations to compare with their previous notes, and graph changes over time. Relates to linked video, DragonflyTV GPS: Bogs.

In this Cyberchase video segment, the CyberSquad calculates the speed of each broom. ***Access to Teacher's Domain content now requires free login to PBS Learning Media.

This activity (on page 2 of the PDF) is a full inquiry investigation into dogs' ability (or inability) to see color. Learners conduct an experiment by first performing a control test and then experimenting to see if dogs are able to fetch colored balls amid a background of gray balls. Learners collect, record, and graph the data to draw conclusions about colorblindness in dogs. Relates to linked video, DragonflyTV: Colorblind Dogs.

In this outdoor activity/game, learners use thermometers to simulate how lizards survive in habitats with extreme temperatures. Learners are challenged to keep their thermometer-lizard "alive" by keeping its temperature within a five-degree safe range. While regulating their pretend lizards' temperatures, learners must move the lizards through a course of sun and shade, trying to reach the finish first. Through the game and followup discussion, learners come to understand different ways that exotherms, or "cold-blooded" animals, regulate their body temperatures and how they differ from endotherms, or "warm-blooded" animals, such as humans. Activity must be done on a warm, sunny day in a site with areas of deep shade, bright sun, and broken or partial shade.

In this activity, learners measure and calculate the amount of cubic feet various containers contain. Next, learners investigate cubic feet per second (cps), by carrying jugs in one second. This activity introduces learners to the units scientists use to measure stream flows and rivers in the United States.

Students explore their prior knowledge of rate and extend it to create tables of values coordinating time and distance. They learn how to examine distance-time graphs and how to calculate unit rates.

Students learn about and practice calculating rates (positive, negative and zero) using data from graphs.

The CyberSquad tracks Digital position in time and then studies graphs to figure out what Hacker is scheming in this video from Cyberchase.

This tutorial provides students with experience using three types of distance scales on regional maps of North America. An introduction shows how to make use of the bar scale, the statement of equivalence, and the representative fraction (ratio) to determine distance between two locations. Printable instructions and two sets of interactive exercises are provided.

This activity (page 2 of the PDF) is a full inquiry investigation into whether hearing or seeing has a bigger effect on jump rope performance. Groups of learners will plan a Double Dutch jump routine and count the number of moves before the jumper trips. Then, learners test the routine while the jumper listens to slow music and again while listening to fast music. Learners collect data, produce a table comparing average performance per auditory stimulus, and consider the validity of their results. An optional extension activity asks learners to investigate how a strobe light affects jump rope performance. Relates to linked video, DragonflyTV: Double Dutch.

In this health activity, learners create a device so that they not only feel their heartbeat, but also see it, using a straw and some clay. Learners calculate their pulse rate (beats per minute) while at rest and after exercise.

Students learn to estimate the time it takes to travel different distances based on an estimation of the time it takes to travel a part of the whole route. This reinforces basic fractional/ratio thinking, as well as early multiplication as repeated addition.

In this Cyberchase video segment, the CyberSquad estimates how much air supply they will need to complete an underwater mission. ***Access to Teacher's Domain content now requires free login to PBS Learning Media.

Harry estimates how long it will take him to get to the front of a long ticket line in this Cyberchase video segment.

Students practice their estimation skills by estimating time and numbers of objects in situations in which counting is not feasible or necessary.