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Category: Computing  |  Career: Physicist

Rock on! Music, Magnets and the Art of recording

Objectives:  Students will learn how MP3 music is recorded onto a disc. Students will learn what a typical Seagate Physicist does in her daily work. Students will have the opportunity to experiment with magnets in order to better understand how data is written onto a CD. By the end of the workshop the students will understand what Seagate physicists are doing to record information.

Supplies: I. Introduction (6 minutes):

Welcome to the EYH workshop. First, let me take a few minutes to introduce myself. My name is Jane Doe and I am a Physicist at Seagate. I work in the X division. Let me begin by telling you a little about what Seagate does and who we are. (please use this time to describe yourself and your educational background and what you do at Seagate).  You may also tell the girls something personal about yourself.

First, what do you think the definition of a physicist is? (wait for a response)

That’s right, a physicist does many of the things you described. Physicists also do X and Y.

I am a special kind of physicist called a  Magnetic Physicist. From my title can you guess what I do?  (Wait for response)

That’s right, I work with X. I also do X and Y.

Now that you have learned a bit about me, it’s time to begin. Today we’re going to learn about how and why information is digitized.  Does anyone know what digitized means? 

(wait for a response).

Some of those definitions are correct. Digitized means…

Let’s spend a few minutes talking about how and why information is digitized.

First, does anyone know how computers are programmed? (wait for response)

Good. Computers need to be programmed in languages. But computers can only understand numbers. They can’t understand language like you and I understand language. When you program computers, you have to program them by using numbers. This is the reason why any information stored on a computer/disc drive needs to be digitized.

Does anyone know how computers are digitized?  (wait for answers)

One language used to program computers is called ASCII (American Standard Code for Information Interchange) This computer code translates any character into one specific number and it converts it.  Let me give you an example of this (give example and explain conversions:  – decimal, hexadecimal, octal, html).

When computers are programmed using numbers, the numbers are simplified into a string of 1 and 0. The one and the 0 can be represented by magnetism, since magnetic materials are used in disc drives for information storage.

Are there any questions so far?

II. Hands-on activity (30 to 45 minutes):

Let’s do a small exercise to try to demonstrate how this happens. First I want you to pick a favorite song or a name of your favorite band. This should be a song or band found on your MP3 player. If you don’t have an MP3 player, use a song or a band from a friends MP3 player. If you don’t know one, pick your favorite sentence or favorite word, or a favorite name.

Now everyone write down their song name, band, sentence or name now. (wait a few minutes).

Now we are going to translate what you wrote down into hex code using 1’s and 0’, this will form binary digits.  To help make this easier for you, we’ve supplied a translation sheet that uses 26 symbols for the alphabet. You can also buy programs that will translate things into code for you.

Now that you have written down your own code, you need to understand how every string of binary digits can be represented by an arrangement of magnets.  Does anyone know what kind of magnet this is?  (wait for a response). 

This is called a horseshoe magnet.  It’s now time to take out your horseshoe magnet so we can begin to understand N/S interactions between them. When we use magnets, there are two additional terms we must know. Attraction and repulsion. Does anyone know what these mean?  (wait for a response, students probably won’t know).

Let me give you a simple explanation of these two terms and then you can give me an example.

Often big magnets are used to rotate smaller bar magnets. Bar magnets attract little metal objects.  Let’s see what happens if we don’t restrict these magnets to their own compartments. What do you think might happen to them? (wait for a response) That’s right, if you do not restrict these magnets to their own compartments; they will interact with each other, and stick together one way or the other. This is called magnetic force.

Now let’s imagine each little magnet represents one bit;

First arrange the magnets to represent one character – pick one string of 7-8 digits of 1 or 0 from the names that you just translated earlier.

(The part below was totally confusing and I didn’t know how to translate it)

There are two options to do this translation:

Two options: 1 is represented by a transition – change of magnetic direction between two bits (magnets), and 0 is a non-transition, meaning same alignment of two neighboring magnets. This will require magnet number = 1 plus the number of digits you’d like to translate.

(A simpler way is to use the alignment of each magnet for each digit, so one direction represents 1, and the opposite direction represents 0. Any opinion?)

Now in your tray with many compartments, please start to arrange the magnets to represent one string of binary code. That means this string (7 or 8) of magnets represents one character. Look at my example, and then you can make your own. (share your example).

Congratulations!  Now you’ve successfully recorded 8 bits of information!

So now that you’ve learned a little bit about magnets and how data is written to a CD, I want to ask you why you think that my job here is so exciting and challenging.  I’ll give you a hint. It’s not because of the people I work with, even though I love the people.  This has to do more with a challenge I face everyday in my work. This challenge is closely related to the activity we just did together.

Wait for a response

You guessed it!  The biggest challenge of my job is trying to figure out how to put more and more information onto these discs.  Today if you open your computer, or IPOD, the storage information is at a rate of 100Gbpsi, that’s 100,000,000,000 bits on a tiny area of one square inch! But yet, the consumer wants more and more storage. You can see what a challenge this is for me as a physicist.  My job is to find the magnetic materials and explore new and better ways to squeeze even more grains into that little space.

What do you think might happen if we store too much information on a disc?

Wait for a response

That’s right, there is a chance the information won’t interact properly and will eventually collapse, like the ones you observed on the tray.  People trust us to keep their information safe, so it’s important that we don’t have storage errors and failures.

Before we conclude this workshop, I’d like to do a short demonstration. Here I have a caddy of 1 inch medium samples. Will someone volunteer to please pick a disc?  Can everyone see this disc?  You can see that this is a thin disk having magnetic materials on both sides of its surface, and each one of these has enough of tiny magnetic grains to store 5GB of information – that’s enough for storing 1000 of your favorite songs, or all the books in your school library.

Now I am going to show you a 500 G bytes drive – Does anyone know how much information this might be able to store?  Take a guess at how many songs or images it might be able to keep.

Thank you for being a part of this workshop today. Before we conclude are there any questions?  I thought that you might want to learn a bit more about magnets and digital recording so I’ve prepared a hand out for you to take with you.  Don’t hesitate to contact me if you have any questions. (provide contact info if comfortable)

Thanks for attending!