Grade 7-9

AnyScience's questions? Ventures inReach Investigations out [email protected] What Time is it?

Campers will learn about the history of timekeeping, then make their own hourglass or water clock and experiment with different amounts of sand or water to make it as accurate as possible.

Materials Safety Considerations ● 1 or 2 empty 2L pop bottles ● Ensure there is appropriate ● Scissors supervision and use of scissors, ● Duct tape hot glue guns and other ● Cardboard potentially hazardous materials. ● Sand ● Water

Background Information

● The earliest form of timekeeping thousands of years ago was just using

the transition of night to day, tracking stars in the night sky, or seasonal changes ● Ancient Egyptians then started using sundials to tell the time, but one major drawback to this was that it did not work if it was cloudy outside ● Water clocks were also invented by the ancient Egyptians - the oldest water clock that has been found was buried with Amenhotep I from 1500 BC ● Around 325 BC the Greeks started using water clocks as well, which they called clepsydras ● The hourglass is a method of keeping time that was developed much later. The first sand hourglasses appeared in Europe in the eighth century ● The first mechanical clock was invented in Europe in the 14th century What Time is it?

Introduction

Think about some different ways of keeping time. What are some ways that you could keep track of time if you didn’t have a clock or watch? How do you think people kept track of time thousands of years ago?

Water clocks and hourglasses are two examples of ways that people kept track of time a long time ago. Today we’re going to build our own, and try to make them as accurate as possible! You can build either an hourglass or a water clock, or both!

Hourglass

Step 1: Cut the top off of both empty 2L pop bottles, just above the label (with parent help/supervision).

Step 2: Take the lid off of one of the bottles. Poke a small hole in the lid of the other bottle.

Step 3: Tape the two bottles together with the open ends facing away from each other (photo below).

Step 4: Tape some cardboard over one of the open ends of the bottles (hot glue would work better if you have a hot glue gun!). Make sure that it is taped tightly, so when you put sand in it, it won’t spill everywhere. What Time is it?

Step 5: Collect some sand to put in your hourglass. Make a hypothesis about how much sand you should add to make the hourglass timer to make it time one minute.

Step 6: Have a real timer ready for when you add the sand in, so you can see how close your hypothesis was. Add your amount of sand to the open end of the hourglass and start the timer!

Step 7: Stop the timer as soon as all of the sand from the first bottle has fallen down into the other bottle. How close was your hypothesis?

Step 8: Add more or less sand to make your timer as close to one minute as possible.

Step 9: Once you have the proper amount of sand in your timer, tape another piece of cardboard to the open end of your hourglass and it’ll be good to go!

Water Clock

Step 1: Cut the top off of an empty 2L pop bottles, just above the label (with parent help/supervision).

Step 2: Poke a very small hole in the lid of the pop bottle (best to use a very sharp needle or pin).

Step 3: Place the top of the bottle into the bottom part of the bottle, with the lid inside (photo below). What Time is it?

Step 4: First, experiment with how quickly the water takes to flow through. Make a hypothesis of the amount of water it would take for all of the water to flow through in exactly one minute.

Step 5: Start a timer as soon as you add the water to the open end, and stop it as soon as all the water flows through. How close was your hypothesis? Note: the water would be easier to see if you use a little bit of food coloring!

Step 6: Using the information from the test above, make a hypothesis about how much water it would take for the water clock to be able to keep track of five minutes, twenty minutes, or even an hour! (You may need a bigger collection container)

Step 7: Pour a large amount of water in the top of your water clock, and start a timer as soon as you do. Make lines on the side of the bottle when the time hits specific time increments (one minute, five minutes, twenty minutes, half an hour, an hour, etc.). Make sure that the water is flowing through evenly. If the water is flowing through evenly, then you have made a water clock that you can use to keep track of time!

Extension: You can try to make a water alarm clock! Brainstorm different ways that you could modify your water clock so that it makes a noise or does something when it reaches a certain time. If you’re looking for some inspiration, check out this video where they explore an example of how the first alarm clocks worked. #SVatHome

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