Welcome to Fermat's Reef. Click here to open a new window with the Fermat's Reef simulation. Note that Fermat's Reef is a big world and you may need to enlarge the new window to see the whole thing. Arrange these two windows on your desktop so you can move easily back-and-forth between them. One way to do this is arrange them so that they overlap and part of each one is visible even when the other one is active. That way you can make the inactive window active by clicking on its exposed part.
Notice the five icons sitting on the surface of the water. Move your mouse over each one. Each icon represents some equipment and when you mouse over the icon readings appear. The leftmost icon -- the red sphere -- represents a solid ball three feet in diameter made of metal. Notice as you mouse over this icon readings appear showing its depth (-1.5 feet since the center of the sphere is 1.5 feet above the water's surface), weight (3619 pounds) and the pressure it is experiencing (15 psi -- normal atmospheric pressure at the earth's surface). The term "weight" requires some further explanation. This is the weight as it would be measured if the sphere was hanging from a scale or sitting on a scale.
Next place your mouse over the same sphere and hold the mouse button down. By moving the mouse you can move the sphere. Lower it into the water. Notice as you lower it all three readings change. The depth reading reflects the depth of the center of the sphere. The weight reading reflects the "weight" as it would be measured by the same scale. Notice as the sphere is lowered into the water its measured "weight" decreases due to the buoyant force exerted by the water. Once the sphere is completely submerged its "weight" no longer changes as it is lowered further. Is this right? The pressure reading also changes. How far down do you have to go so that the pressure is twice what it was at the surface of the water?
As you work with one of these icons you can record its current reading by pressing the Record Data Point button. Each time you press the button it records the reading shown the last time you moused over a particular icon. You can clear the data in this window at any time by clicking the Clear Data button. The data shown in the data window can be copy-and-pasted into a spreadsheet for further analysis. To copy the data, first highlight the lines that you want to copy by clicking and dragging the mouse in the usual way and then press CTRL-c (Windows) or Command-c (Mac). Sometimes CTRL/COMMAND-c must be pressed several times. Next click on the cell that you want to be the upper left corner of the data in your spreadsheet and press CTRL-v (Windows) or COMMAND-v (Mac) to paste the data into the spreadsheet.
Next look at the icon showing a brown sphere. This represents a solid sphere whose diameter is three feet that is made of wood. Do the same experiments with this sphere that you did with the metal sphere. Notice that when the sphere is fully submerged in the water its "weight" is negative. What does this mean?"
The third icon -- the blue sphere -- represents a spherical balloon whose diameter is also three feet. Do the same experiments with this balloon that you did with the two solid spheres. Put a solid sphere and this balloon next to each other at a depth of 30 feet. What do you see? Why?
The fourth icon -- a white square -- represents a white square. We can use it to investigate how colors change underwater. Water absorbs different colors at different rates. Experiment by lowering the white square into the water to see what happens. Notice that there is an abrupt change when the white square first enters the water because the surface of the water reflects a portion of the light.
The fifth icon represents apparatus that measures temperature and the concentration of dissolved oxygen. The readings are based on actual readings from a lake rather than the ocean. Experiment a bit to see how temperature and dissolved oxygen vary with depth.