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  • Cartesian Diver

    The "Cartesian Diver" is a classic science experiment that demonstrates the principle of buoyancy. Here's how you can try it at home!


    • Bottle with cap 
    • Water 
    • Eye dropper (or ketchup packet) 
    • Pitcher 


    • Fill the bottle nearly to the top with water.
    • Fill the pitcher with water.
    • Use the water in the pitcher to fill the eye-dropper. Slowly fill the eye dropper with water until there is enough for it to float just below the surface of the water.
    • Place the eye dropper in the bottle, and screw on its cap.
    • Squeeze the bottle, and observe what happens to the diver.

    The Science 

    So why does the eye dropper fall to the bottom of the bottle when it's squeezed? 

    This experiment demonstrates how density is related to buoyancy, which describes how a liquid will push an object upwards. If the object submerged in the liquid is light enough, the liquid will push that object up. If the object is too heavy for the liquid to push it upward, it will sink. 

    Can you think of anything that can float in water? These things are buoyant!  

    Can you think of anything that sinks in water? Those things are negatively buoyant! 

    As the bottle is squeezed, the pressure inside it increases. As the pressure goes up, the liquid in the bottle pushes harder against the walls of the bottle and all the other molecules in the bottle. 

    You might have noticed that the air bubble inside the eyedropper gets smaller as the bottle gets squeezed. This happens because the increase of pressure on the liquid inside the bottle is compresses the air in the diver.  

    As that air becomes compressed, it becomes denser and too heavy for the water to keep it at the top of the liquid! It becomes negatively buoyant and sinks to the bottom on the bottle.  

    When you stop squeezing on the bottle, the pressure decreases. The air bubble inside the eyedropper expands and becomes less dense. It becomes buoyant again and floats to the top! 

  • Today is World UFO Day!

    Have you ever seen something in the sky that you haven’t been able to identify? Then you've seen a UFO - or an Unidentified Flying Object!

    There could be any number of explanations for the different UFOs that people have seen around the world - ranging from strange biological phenomena like swarms of bugs to astronomical phenomena like meteors, satellites or even extraterrestrial life.

    What are the odds that those UFOs are aliens? What are the odds that aliens even exist? Scientists called astrobiologists are trying to figure that out right now!  

    Are there microbes that live in the Martian soil? Or perhaps strange space-fish that swim in the liquid water below the icy surface of Jupiter’s moon, Europa? Are the UFOs that are witnessed around Earth being controlled by hyper-intelligent aliens from distant worlds? 

    While it might be hard to confirm whether aliens have visited Earth using UFOs, researchers at the SETI (Search for Extraterrestrial Intelligence) Institute look to the stars to find evidence of intelligent alien life that might be trying to communicate with other distant intelligent life forms.

    To aid their search, they can use the Drake Equation. According to the equation, pointing your sensors toward more habitable areas of the universe (areas with stars systems that can host planetary suitable for life systems) can help improve the odds of finding these distant intelligent life forms.

    You can learn more about the Drake Equation here: https://www.seti.org/drake-equation-index

    UFO Activities & Info

    Check out this hands on activity our friends at NISE Net put together where you can “draw an extreme environment beyond Earth, then invent a living thing that could thrive in it” - as well as some information about NASA’s initiatives to search for life beyond Earth: https://www.nisenet.org/catalog/exploring-universe-imagining-life

    Extremophiles, animals that live in extreme environments: https://www.nisenet.org/sites/default/files/catalog/uploads/ExSci_Space_ImaginingLife_cards_2up.pdf

    Imagining life Drawing Sheet: https://www.nisenet.org/sites/default/files/catalog/uploads/ExSci_Space_ImaginingLife_drawingsheet_2up.pdf

    Searching for Life Info Sheet: https://www.nisenet.org/sites/default/files/catalog/uploads/ExSci_Space_ImaginingLife_SearchingforLife.pdf

    TRAPPIST1 Info Sheet: https://www.nisenet.org/sites/default/files/catalog/uploads/ExSci_Space_info_sheet_TRAPPIST1.pdf