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Title
What is a CD's data track spacing?

**Problem Scenario**
When different genres of music are put into the computer some take longer to recognize than others, I'm wondering if the data track spacing has anything to do with that.

Broad Question
Is the data track spacing on CD's different?

Specific Question
Do different genres of music have different data track spacing?

Hypothesis
I think that the genres that have more rhythm will have data track spacing that is farther apart than the other genres, example: rock has a bigger spaces between the tracks than jazz.

Independent Variable:
Types of music

Dependent Variable:
Data track spacing

Variables That Need To Be Controlled:
Genre of music discs

Vocabulary List That Needs Explanation:
Genres: Types of Music CD: Compact Disc Screen: The wall opposite of the CD Length: The distance (cm) between the CD and the screen Arc 1 and Arc 2: The distance (cm) from the center dot on the screen to the arcs on the side Arc mean: (Arc1 + Arc2) / 2 Data track: The spiral of bumps that the data contained on the CD is stored in

General Plan:
I will set up the CD, books, and laser pointer. After that I will get all of my data and record it in my notebook.

Potential Problems And Solutions:
The CD could reflect the laser pointer's beam into my eye and I could go blind.

Safety Or Environmental Concerns:
I will be careful not to shine the laser beam directly into my eye.

Number Of Comparison Samples:
I tested this with 4 genres of music.

Number Of Observation In Each Sample:
I tested each genre with 2 CDs.

When data will be collected:
My data was collected as I was testing each CD.

Where will data be collected?:
My data was collected in my science journal.

Resources and Budget Table
Laser Cds Books Tape Measure

Data Table

 * Genres || Jazz || Rock || Pop || Classic ||
 * Arc Mean (cm) || 19.5 || 22.35 || 23.15 || 30.075 ||
 * Length (cm) || 57.25 || 68.25 || 66.6 || 63.85 ||
 * Laser Wave Length (mm) || 532 || 532 || 532 || 532 ||
 * Data track spacing || 1.395 || 1.65 || 1.53 || 1.405 ||

Background Research:
Light can be found in a couple of different ways: natural and man made. Some light is used to transmit data, while other types are made to light up a room. Light is also used in a CD player to read the data stored on the CD. Data is stored in bumps on a CD, these bumps are stored in a spiral pattern. This spiral is usually 3.5 miles long. The bumps themselves are very short and no more than 0.5 microns wide. A CD is made with layers: there is a polycarbonate layer and an aluminum layer. When the light is shown on the CD it goes through the polycarbonate layer and reflects off of the aluminum layer.

**Sources:**
"How CDs Work." Web. 02 May 2012. . //HowStuffWorks//. Web. 02 May 2012. . "How Does a CD Work?" //CD Duplication and DVD Replication : Professional Copy Services//. Web. 02 May 2012. .

Detailed Procedure:

 * 1) Put the CD in between book pages and stand the book up.
 * 2) Aim a laser at a 90 degree angle to the CD (Back of the CD) so it reflects a dot and two arcs on a wall opposite of the CD.
 * 3) Put tape over the button of the laser to keep it on and measure:
 * 4) Measure the length (cm) from the CD to the wall, call this length.
 * 5) Measure the distance (cm) from the dot to one arc, call this arc 1.
 * 6) Measure the distance (cm) from the dot to the other arc, call this arc 2.
 * 7) Then add arc 1 and arc 2 then divide the answer by 2, call this arc mean.
 * 8) Do this equation: //((Length / Arc mean) * wavelength) / 1000//
 * 9) The answer you will get is the distance between the data tracks in microns.

All Raw Data

 * Genre || Rock || Pop || Classic || Jazz ||
 * Arc mean (cm) || 22.35 || 23.15 || 30.075 || 19.5 ||
 * Length (cm) || 68.25 || 66.6 || 63.85 || 57.25 ||
 * Laser wave length (nm) || 532 || 532 || 532 || 532 ||
 * Data track spacing || 1.65 || 1.53 || 1.405 || 1.395 ||

Data Analysis
The genre of rock had a data track spacing of 1.65 microns. The genre with the second biggest data track spacing was pop which had 1.53 microns. The smallest two genres had data track spacing of very similar sizes: the classic had a spacing of 1.405 microns, and the smallest spacing of jazz had 1.395 microns.

Conclusion
The end result of my data was very close to my hypothesis. The genre rock had data track spacing of 1.65 microns, my hypothesis was 1.6 microns. Pop music had spacing of 1.53 microns, my hypothesis was1.5 microns. My hypothesis was that classic and jazz would both have a spacing of 1.3 microns, in my experiment the classic had 1.405 microns, and the jazz had 1.395 microns. This was very close to my guesses of each genre of music.

Discussion
This information is important because it tells that certain types of music need more space on the CD than others. Knowing this makes burning CDs more efficient. How this works, for example, is the larger the spacing, the less of the music that can fit into a Gigabyte. Most instruments in rock play on the same beat, or rhythm, making it less complex thus needing less tracks or bigger spaces. Jazz on the other hand has lots of instruments playing different tempos and rhythms at the same time making it necessary for more tracks of data, so they are spaced closer together.

Benefit to Community and/or Science
People might now understand that when burning a CD, some CDs may fit more of one genre than the other. For example, a CD would fit more jazz music than rock due to the amount of spacing needed between data tracks. The way this works is most instruments in rock play on the same beat making it need less tracks. Jazz on the other hand has lost of instruments in each second making it necessary for more tracks of data, but they are closer together.

Abstract
I wanted to burn a CD and have the most amount of music on it as possible without having too much. For example a CD will fit less rock because the data track spacing is larger and a CD is not an infinite length, so it can only fit a certain amount of rows of tracks. I did my experiment by shining a laser pointer at the CD and letting it reflect onto the wall opposite of the CD. I then took the measurements of length, arc 1, arc 2, and laser wavelength. I put all of the measurements into the formula of //((Length / Arc mean) * wavelength) / 1000.// I found out that the genre rock has the farthest spacing and the genre jazz has the closest spacing. Therefore, I can put more jazz music onto a CD than classical, pop, or rock.