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A Lesson on Doubling

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Exponential growth is characterized by a rate that is increasing with time. One can use a doubling time to describe such growth. For example, now that it is spring time, one can observe how fast weeds grow. If the doubling time in the area that weeds cover is 3 days, one can imagine that starting with a square foot of weed coverage, in the next three days, the weed will cover 2 square feet. In six days, it will be 4, and in nine days, it will be 8 square feet. And in just 3 weeks, that is, 21 days, the weed area would have doubled 7 times. By that time, 128 square feet will be covered by weeds. That will be a lot of work on my weed whacker. The death rate from COVID-19 behaves similarly. And right now, the doubling time for the number of COVID-19 deaths in the US is 3 days.


Currently, the number of deaths in the US due to the novel corona virus is just a little under 6,000. If we assume that the doubling time remains constant for the next three weeks, on April 24, the number of the de…

A Lecture on Greenhouse Gases: Part 2

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Greenhouse Gases: Lecture II
Chem 002
Angel C. de Dios
Chemistry of the Environment (Greenhouse Effect)"The Earth system follows laws which scientists strive to understand," 
said Dr. F. Sherwood Rowland, a Nobel laureate in chemistry.
"The public deserves rational decisionmaking based on the best scientific advice about what is likely to happen, not what political entities might wish to happen."
From: Preeminent Scientists Protest Bush Administration's Misuse of Science
Table copied from  http://academic.reed.edu/chemistry/courses/chem101/Handouts/IntrotoGreenhouseEffect.pdf
The Solar Constantis the amount of energy that falls on a planet, on a plane perpendicular to the rays of the sun.  This constant is a function of the distance of the planet from the sun.  Since a planet cannot have all of its surface perpendicular to the sun, the average Solar Constant for any planet is actually smaller.  For Earth, it is 340 W m-2 (Watt is a unit of power = Joules /second, and …

A Lecture on Greenhouse Gases

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Greenhouse Gases: Lecture I
Chem 002
Angel C. de Dios
Chemistry of the Environment (Greenhouse Effect)"The Earth system follows laws which scientists strive to understand," 
said Dr. F. Sherwood Rowland, a Nobel laureate in chemistry.
"The public deserves rational decisionmaking based on the best scientific advice about what is likely to happen, not what political entities might wish to happen."
From: Preeminent Scientists Protest Bush Administration's Misuse of Science



When I first added "Greenhouse Gases" as a topic in my General Chemistry, I shared with another Filipino American scientist the slides I prepared for that first lecture. This was back in 2008 and the following was his response.
My son, Alexander, was two years old then. I took the following photos when he was just several months old.
Yes, there are 13 questions in the next homework on Sapling. These are due a week from now, but I would like you to work on the first 13 questions before this w…