Hurricane models and the nature of science

Here I am, at my parents house. There is no power at my house and Louisiana in September with no power is really a whole bunch of no-fun. But maybe I can use this time to talk about science.

**The Nature of Science**

Here is a review. What is science all about? (I am pretty sure I talked about this before) Science is about making observations and from those observations creating models. If the model predicts other things that are confirmed, then that is good. If not, the model must be changed. Really, it’s that simple.

**Hurricane Models**

It is somewhat interesting that forecasting hurricanes is quite similar. To do this, they (hurricane people) start with a model of how a storm behaves. In this model they input the current weather conditions and run the model. Not everyone agrees on how a storm would behave given some initial conditions and not everyone agrees on what the initial conditions even are. The result is that there are several models (as shown below):
![hurricane models](http://blog.dotphys.net/wp-content/uploads/2008/09/hurricane-models.jpg)
(from [Weather Underground – a great weather site](http://www.wunderground.com))
Notice that the models do not agree. Everyone knows the models are not perfect, so multiple models are good. If the models are close in agreement, then there is more certainty in the track.

On a somewhat related note, I remember for a previous hurricane a weatherman said the following:
>The models say the hurricane will hit HERE. So, it’s NOT going to do that. It will either hit to the left or the right because the model is never correct.

I still find that quote to be quite funny. This would be the same as a person with a gun that is a bad shot. It is ok to aim at someone because the WILL miss.

How long do you wait for a question to be answered?

I teach classes. I ask questions in class. I wait for answers. All faculty do this, so who cares. If you are in a class or teaching a class, how long do you wait for someone to answer your question? Well, I asked two questions of my class this week.
1. Estimate how long I wait when I ask you questions.
2. How long should you (ideally) wait in a class for someone to answer?
Here is the data I gathered: (and I will tell you how long I actually wait)

Continue reading “How long do you wait for a question to be answered?”

How about a massive catapult to replace the space shuttle

I recently saw a comment on a blog somewhere about putting satellites into space (I think it was from a post about a rocket that blew up). The poster suggested using a giant catapult to put things in space instead of rockets. Maybe he or she was kidding, or maybe not. But I have heard this idea before. Would it work?

Continue reading “How about a massive catapult to replace the space shuttle”

Mythbusters Moon Stuff and Me

Clearly the MythBusters did this before I did (it’s just air tonight though). I just wanted to say that I posted some videos of the Apollo “jump salute” video analysis and also sped it up to “Earth-like” accelerations. I then made a video of my daughter doing the same thing on Earth and slowed it down. Yes, the MythBusters did it better, but I just wanted to say “me too”. My analysis is here:
[Undoing Fake Moon Landing Videos](http://www.dotphys.net/files/moon-time.html)

P.S. I also slowed down a video of Kobe Bryant Jumping so he has an acceleration of that on the moon.

Heat. It’s a four letter word

Heat. You have heard it before. You have used it. I have even used it. Do we need this word? No. Is this a useful word? No.

Let me start with the definition as usually stated in a physics type text: (this is from [dictionary.com](http://dictionary.reference.com/browse/heat))

*heat:* a nonmechanical energy transfer with reference to a temperature difference between a system and its surroundings or between two parts of the same system.
This definition is fine. It is not wrong, but is it needed? Not really. Couldn’t we just say energy transfer? Actually, I like to use this in the following equation:
![work energy](http://blog.dotphys.net/wp-content/uploads/2008/08/work-energy.jpg)
In this equation (the work-energy equation) W stands for the work, and Q is typically referred to as “heat”. This equation is used for systems of particles, if you just have one particle, then the fundamental equation is:
![work](http://blog.dotphys.net/wp-content/uploads/2008/08/work.jpg)
So, expanding to macroscopic systems, Q is still work. Work is the only way to change the energy of a system. I like to call Q (like some textbooks do) as micro-work. Q is the work done on the system due to particle collisions from another object.

The other non-sciencey definitions are clearly wrong. The common usage of the word heat is also clearly abused. This can be seen in phrases like “add heat” or “remove heat”. Another poor usage (which I have used) is “heat this thing up” which implies heat is a verb.

Ok, then if we do not use heat – what then? I think if you want to talk about transfer of energy, say transfer of energy. If you want to use Q, call it microwork. If you want to talk about the energy something has because it is hot, say thermal energy.

The Iron Cross – or: Why is Gymnastics so Darn Difficult?

I know the olympics are basically over. Really, I should have posted this earlier. Anyway, the gymnastics feat that always impresses me is the Iron Cross (I think that is what it is called). I know you have seen this, but here is a picture from wikipedia:

![Example 2ofironcross](http://blog.dotphys.net/wp-content/uploads/2008/08/example-2ofironcross.jpg)

(http://en.wikipedia.org/wiki/Rings_(gymnastics))

Why is this so impressive? Why is this so difficult? Let me start with something completely different that is exactly the same (in some ways).

Continue reading “The Iron Cross – or: Why is Gymnastics so Darn Difficult?”

ARRRGGGGG RapidWeaver, why do you hate me?

Dear RapidWeaver,

What did I do to you? I like you, I really do – but this is why we broke up. It’s not you, it’s me. No wait, it’s you. I am looking back through my old dotphys posts and most of my introductions are GONE. I was starting to think I was crazy when I wrote these. Take for instance [My analysis of Kobe Bryant’s Jump](http://dotphys.net/files/kobe.html). Isn’t it odd how this starts? That is because it is MISSING the first paragraph. The only reason I know I am not insane is because of Apple’s Time Machine. I went back and looked and the older file has an intro. RapidWeaver, see how you are!

Moving my blog

As you may or may not have noticed, I have been using RapidWeaver for my blogging posts. (if you don’t know what that is, it doesn’t matter) Anyway, I think my stuff was getting a little too big for that software. It was a great place to start, but it is time to move to something else (WordPress). My plan is to keep http://www.dotphys.net as it is so that if you linked to something there, it will still be linked. Also, I will use dotphys.net to post longer tutorial style things. I will likely move some of my favorite posts over to this, but that will take some time (but it will give me some material – I know it’s cheating)

[http://www.dotphys.net]: http://www.dotphys.net