This is a link to a NY Times article pointing out that when people travel by air they put a lot of carbon in the air. This is fundamentally a result of burning aviation fuel so this is the same as having a high energy cost to air travel. One of the characteristics of our class members is that they don't fly a lot so the energy costs and potential carbon contributions are different in our community.
If we have time I will probably use the question of whether a bike is "more efficient" than a car to help us understand how really complex these questions can get and how important it is that we appreciate that complexity. You may decide it's too much work to figure out but laws and policy are often made based on fragmentary or incomplete understanding of a situation. We may sometimes make things worse when we think we are making them better because we don't understand the data or the analysis. Just scan this discussion and see if you can understand the big picture before we discuss in class.
As we seek to compare the numbers that David MacKay comes up with for Britain with equivalent numbers for the US we need data. This is a national data set for vehicle use we can use for reference. Yup, its confusing to figure out but that's pretty common for data. Part of what we are practicing is the figuring out of relevant data.
This is a great blog from a physics person, Tom Murphy, at UCSD. Like our class he is interested in looking at what the math tells us about many energy related questions.
It always seems remarkably hard to actually find the data you need to try and answer questions about energy. This is partly because the details change a lot (though the big picture is pretty consistent) and there is money involved (which makes people cagey). Here's an example from our own transit system that shows why it can be so hard to figure out what is happening.
The discussion of overall engine efficiency is long and complex but here is an attempt to put some rough numbers together to keep things in context.
