The central valley of California.

APh 150 / Bi270 C : The Great Human Experiment by the Numbers


The greatest experiment of the last 10,000 years is the presence and action of modern human beings on planet Earth. At this point, the consequences of this experiment are being felt on many fronts. Yet, many people still hold the view that because the world is so “huge”, humans cannot really make a substantial impact. One way to organize our thinking about what these impacts might be, with tongue in cheek, is to focus on Empedocles’s classic elements, earth, air, water and fire, with the idea being to explore how humans have altered the land and its inhabitants, the atmosphere, the oceans and how our quest for cheaper and cheaper energy (fire) from the world around us has altered that world. In this course, we will explore and establish a definitive series of resources on Human Impacts by the Numbers and make quantitative, back-of-the-envelope estimations of our impact.


We will meet once as a week on Wednesdays from 4pm to 6pm PST for a lecture and discussion about various topics. Due to the current SARS-CoV-2 pandemic and the California Shelter-In-Place order, the meetings will occur via the Zoom video conferencing service. Auditors are welcome to join the class. Email Griffin (gchure [at] caltech [dot] edu) for the Zoom meeting link. You may NOT share the link outside the course without instructor permission.

Course Policies

This course will meet once a week with mandatory attendance (or by listening the lectures after class). The course grade will be based upon two activities: every student will construct a single “by the numbers” vignette that features a key questions about human impacts (needs to be approved by instructors), an estimate of what sets the scale of the human impact of interest, a dimensionless ratio that characterizes the magnitude of the effect, a well curated spreadsheet providing the data on the topic of interest and a written several page “vignette” that tells the story of that human impact. In addition, every student will give a presentation to the rest of the class during the last week of the class. Collaboration is strongly encouraged. As a class, we will also develop a one page “key numbers on human impacts” that captures 25 of the most important human impact numbers we can think of. However, for the individual human impact numbers, every student needs to turn in their own original contribution. There will also be several homeworks that will be graded by students within the class.

Course GitHub

During the course, you will scour the internet for reputable sources of key numbers necessary to either perform or sanity-check our estimates. It is important that we keep a detailed ledger of our data sets, sources, and potential biases they may have. To that end, we will be using a repository hosted by GitHub. Please set up an account on GitHub (if you don’t have one already) and send your username information to Griffin (gchure [at] caltech [dot] edu) and we will grant you access to the repository.