Your Guide to Physics

Friday, March 31, 2006

I Honestly Don't Know if This is Real...

or just "seasonal"

"You are deep underground in a lab that once housed some of the finest minds in chemistry. But robots directed by a crackbrained artificial intelligence have taken it over and plan to use its equipment to destroy the world! After freezing an evil robot with your handy wrist-mounted hot-and-cold gun, you reach the Haber-Bosch room. And now you must correctly synthesize ammonia or die."

Critical Mass: The Chemistry Video Game

I mean, it must be an april fool, right?

ESA - Space Science - Home - Cluster and Double Star witness a new facet of Earth’s magnetic behaviour

Cluster and Double Star witness a new facet of Earth’s magnetic behaviour

30 March 2006

Five spacecraft from two ESA missions unexpectedly found themselves engulfed by waves of electrical and magnetic energy as they travelled through Earth’s night-time shadow on 5 August 2004. The data collected by the spacecraft are giving scientists an important clue to the effects of 'space weather' on Earth’s magnetic field.

Conduct Your Experiment

First of all, gather together everything you need for your experiment before you get started. Doing this means you wont be interrupted, so that your momentum will be maintained and you will get through the experiment as efficiently as possible.

Follow the steps you designed earlier as closely as possible. If the results are very different to what you expected, you might need to modify your procedures on the fly. In that case, be sure to note down (in your notebook – where else?) any changes you make to your experiment, so that you can include them in your report. When you need to modify the experiment, you should consider why things are not going as expected – is your hypothesis wrong, or are there assumptions that need to be rethought? Does your new design still answer the question you are interested in? It's perfectly fine to move to a new question if something more interesting comes up in the moment.

As you go through the experiment, record notes on your materials used, your observations and any thoughts you have about the experiment – they might be useful when you come to writing your report. Obviously, you need to record all the results of your experiments – ideally in a table format, with dependent variable measurements cross-referenced with their corresponding independent variable settings.

You should take the mean of several identical trials for each set of independent variables. This is done to minimize the effects of the uncontrollable random events that affect most experiments. Virtually anything can happen once or twice, so single results do not form a very convincing argument for or against your hypothesis. The more trials, the better. Depending on your level, you might be required to perform more a complicated statistical analysis – in this case, it is especially important to record every result, so that you can take means and find standard deviations and errors as required. This sort of analysis will tell you how accurate or reliable your results are.

Thursday, March 30, 2006

An Hypothesis

An hypothesis is an educated guess about the answer to your question. You did educate yourself with all the research, right? Your experiment will either support or disprove your hypothesis.

Remember, your hypothesis need not be right – disproof is a result too! In fact, many of the greatest discoveries have come from the disproof of an hypothesis.

Generally your hypothesis should be stated clearly, with the lines of reasoning and supporting facts you used to generate it. It is very important that you generate some sort of hypothesis before you start your experiment proper – without some idea of what you are looking for, it is hard to design an experiment, and usually even harder to understand the results.

Designing an Experiment

Your experiment needs to be designed so that it tests your hypothesis. The key point to designing an experiment is to control your variables.

Variables are anything that can affect the outcome of your experiment. There are three important classes of variables to consider:

Independent variables are the few (or even better, one) quantities that you deliberately vary during your experiment, in order to asses their affects.
Dependent variables are the ones that change in response to your deliberate variations of the independent variable. At least, your hypothesis says they will.
The remaining variables are usually fixed at the same value from trial to trial, and are called controlled variables. Also variables that do change, but not in an important way between trials. For example, in many experiments the time of day, which changes as you conduct trial after trial, will not be important. However, bear in mind these variables that are incompletely controlled – if your hypothesis fails, these are often the first place you should look for an explanation.

You also need to bear in mind confounding variables. These are variables that change in an important way during your experiment, but you don't control, or at least account for. For example, if you were testing an hypothesis relating the amount of light in a room to the position of the dimmer switch, you would need to account for the differences in light coming in through the windows if some of your trials were conducted in the morning and some were late at night.

Be very careful if you do have more than one independent variable in your experiment. You need to know what variations are due to which changes. Only vary one independent variable at a time – this way you will be able to see the independent affects, then you can try varying them together to see if there are any interesting relationships.

You should draw a diagram of your experiment before you get started. Be sure to list everything you need, so you can have it on hand and just do the experiment. Nothing kills momentum like having to stop and find some more items you forgot you needed.

Wednesday, March 29, 2006

How to Pour Ketchup (Catsup, Tomato Sauce)

Are you one of those people who taps at the bottom of an inverted ketchup bottle, waiting in frustration for the sauce to pour? I am speaking of traditional ketchup bottles, not squeeze tubes, wide-mouth jars, or bottles designed to stand on their heads. Have you ever wondered if there is a right way to do it – a way that works, and makes scientific sense?

Yes, folks, there is a right way to do it, and it does make sense. Here is how, and why:

Tuesday, March 28, 2006

Extreme Thinking and Tough Learning

Michael Neilsen, a professor at my undergraduate school, UQ, wrote about "Tough Learning" - the special challenges to the way we think and learn posed by the natural sciences.

You will notice that this essay was written in 2003 - but it only recently came my way.