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Thursday, December 24, 2015

Check out how Climate Models are put together and tested in order to have any confidence in them

This is a wonderful TED talk by a climate modeler named Gavin Schmidt. He explains what goes into the million line code that is the modern climate model  in terms of the science, and, most importantly, how climate scientists go about checking to see if the models are working. The method: take real data and trends, run the model with the appropriate initial conditions, and simply see if the output of the model looks anything like the real-world. This is how any type of simulation experiment works. When the model begins to become statistically consistent with real data, the model is called 'skillful.' Climate models have become skillful, as shown in this presentation.

What is really cool about having any type of reliable, tested, skillful model and simulation is that one can then make predictions. In the case of climate models, the user can put in any conditions and tweak as many parameters as they want, run the model over time, and see what the world will look like under those conditions. He shows this, as well, for three cases: cutting back on carbon emissions a little, cutting back on carbon emissions a lot, or doing nothing at all with things happening at current rates. What the world looks like comparing those three scenarios is eye-opening.

And, keep in mind that as scientists have fine-tuned the models using past data (and they go back tens of thousands of years), and tweak parameters based on the measurements, the way they get a world that looks like today's is by adding in the carbon emissions over the past century.

Monday, December 14, 2015

Physics Olympians

Here are some links:

Old Olympiad'll want to check the F = ma exams and solutions. This is all about mechanics for the first round. This is the single best way of preparing for the types of questions and problems they put on this thing.

Mechanics videos on all sorts of topics, for review. They tend to put some rotations problems on, including parallel-axis theorem. Also simple harmonic motion, circular motion, and everything else that comes along with mechanics. There may also be a question or two about buoyancy. Check this out in the book, and an intro video.

Doc V's Olympiad page. Included on this are equation sheets to review (you do not get these on the test, though), mechanics objectives that may be worth reviewing over 10 minutes to remind yourself of all the possible topics, and an Olympiad syllabus, which is the packet given to physics Olympiad team members. This is a good review guide for mechanics.

Don't forget old AP exam problems, worked examples in the book, AP review books, and the chapter summaries in each chapter of our book. There is also the mechanics objectives, which is the point-by-point summary of everything we have had in mechanics. It is worth a 10 minute skim.

We can meet during 5th and 6th periods the week we return from break, and we can find a time during finals week. We will take the test on Monday, January 18, 9-10:30 am.

Sunday, December 13, 2015

Engineering-based Medicine

The University of Illinois at Urbana-Champaign has what is typically regarded as one of the top five engineering programs in the world, and next year the Carle College of Medicine will be the first medical school to be designed to fully incorporate engineering into its curriculum. Check out the site describing this new 21st century type of medical school, which will begin to contribute to medicine like UIUC contributed to the building of modern electronics in the 20th century.

If you are interested in medicine, engineering, or biomedical engineering, all aspects will be included in this new way of teaching, learning, administering, and doing medicine.

Saturday, December 12, 2015

Real life Rotational Physics!

Check out the article linked the ice caps at the poles melt, much of the melt water makes its way towards the equator (why do you this is?). This is changing the mass distribution of the earth to some small degree. Another name for the distribution of mass relative to an axis of rotation is the moment of inertia, or rotational inertia. This is causing changes in the earth's rotation. Think fast before reading the article: If the water moves towards the equator, what should happen to the period of the earth's rotation?

See if you are correct!

Wednesday, December 9, 2015

Python Activity for Today: Using Python code to fit data sets, and 'discover' Dark Energy!

Up to now, we have begun to learn some basics of Python using Codecademy, then we began to use Python to develop simulations of a bouncing ball (how to put equations of motion into a program) and a double pendulum (which we cannot do with pencil and paper, and included a focus on making graphs and animations in a program). Today, we will use a Python program to analyze data, which happens to be the data used to determine the acceleration of the universe and prediction of Dark Energy.

The activity for today is here. We will open Canopy to do this, as in the past.

If you are interested in the physics behind all this, dark matter and dark energy are not the same things. Dark matter is a term used for matter we cannot see. It could be a mix of several things, such as 'ordinary' matter and some new types of matter, that we cannot see directly but presume it is there due to its gravitational effects on things like galaxies. Dark energy is a term used for whatever it is that makes the expansion of the universe accelerate - we do not know what dark energy is. Of course, there is the scientific model for how the universe began and why it is expanding in the first place, the Big Bang.

Minute Physics video on Dark Matter.
Minute Physics video on Dark Energy.

Thursday, December 3, 2015

Classes for Period 3-4

Today, check out the first half of "Runaway Universe," which is about the strange acceleration of teh expansion of the universe we have mentioned in class.

Then, take notes on situations where BOTH linear and angular momentum are conserved. This would be like hitting a pencil on a table top off center - it will both move forward and rotate as it goes. The two problems for tonight involve these concepts. The video is here.

Wednesday, December 2, 2015

For Afternoon classes

Happy Wednesday! Who's got it today?!

Watch and take notes on a video about potential wells. These are represented by graphs of potential energy, U, as a function of position, x.

The way to interpret this is to imagine a particle stuck at the origin of the graph, and then a second particle is moving around at different distances. The graph plots out the energy between the two particles at those separations.

On a U-x graph, we can also identify two types of equilibria - stable and unstable. Stable would be at the bottoms of dips, and unstable would be on hilltops of these graphs. Remember, Nature seeks lowest energy states.

Mathematically, we will be using the new gradient concept, F = -dU/dx. Force graphs can be drawn based on what the slopes are doing on the potential energy graph. Remember, dU/dx = slope of the energy graph!

After the video, you can get working on the spring lab. We are interested in measuring the stretch caused by different masses. The main product of the lab will be the graphs of F vs. x, where x = the stretch distance, or displacement, of your springs.

For homework, complete any parts of the lab that remain, and also write up a short summary of an article you find interesting. Thanks!