The Weight of Data

Introduction

If all the files stored on a computer were represented physically using common media formats (pdf print outs for text, CDs for music etc.), how much space would they take up?

As a by-product of dematerialising everything, we are losing the sense that data represents weight and size. In fact, if all the data in our computers were represented physically in a space the size of the Sahara Desert, that space would be as dense as Manhattan.

Facilitation tips :

This activity will require you to make visualisations of data. You should then be prepared to write simple mathematical formulas.

Beginning

Once the group is settled, take a 16gb USB key and read the introduction. Mess with the key by throwing it and catching it. Once the introduction is complete, choose a participant and throw the key to them, saying ‘how does it feel to hold ten tonnes in your hand?’ This key is filled with huge numbers of PDFs, books, documents etc. It contains approximately 2 million pages.

For fun, if you have an electronic scale available, weigh one 16gb USB key filled with data and another that is empty. No weight change OBVIOUSLY. 🙂

This is a reference to the persistent idea that the weights change. We are in fact dealing with a flash memory system involving two states – 0 or 1 – which change according to electronic impulses. The weight then does not change.

Give an example of a PDF file of 60 pages. This is 500 kilobytes (kb). So one page makes 8 kbs. 1 gigabyte (gb) = 1000000 kilobytes. So your USB key really contains 16000000 kb.
Therefore: 2 million pages at a rate of 5g per page = 10 tonnes. Nice one.
…

Today the 128gb USB keys are common and cost around €20. Let the participants find the number of books that could be stored in one of these and try to find an equivalent ‘real world’ physical storage method to store all of these. Their living rooms? Maybe they could line the floor of a stadium? Here might be a good point to revise the maths.

 

More examples online

Invite participants to search online for extra information – then in the ensuing conversation, make their head spin referring to the sheer amounts of data available.

For example:

• A book of 13x20cm = 260cm²
• 38 of these will make 1m²
• A soccer pitch is 7000cm²

How many books would be required to cover a football field and could there be enough on a 16gb USB key?

Try the same exercise but in terms of height: how high would be the pile of books that could be stored on your 16gb USB key?
Are your audience blown away yet? If not, try explaining that the New York Public Library has over 1 pb of data in work available for consultation.

Pb = Petabyte. Let’s back up a little. We spoke earlier about the kb (kilobyte) which is a unit of storage. A byte is a unit too small to be used or referred to in a practical or commercial sense. Imagine ‘10000000000 byte USB key for sale’. We will therefore think of it like this: byte -> kilobyte -> megabyte -> gigabyte -> terabyte -> petabyte. These days, we speak in terms of gigabytes and terabytes in regards to hard drives.

Thus, the amount of data in a pb is quite staggering – it’s 1000 terabytes, which is 1000000 gb. (Try this conversion link: https://www.gbmb.org/pb-to-gb)

 

A progression in 3 photos

 

1. In 1956, the US army commissioned IMB to deliver a device for storing data. This would become the Ramac 305, the first hard drive capable of storing 5 million characters – 5 mb. Weighing more than a tonne and taking up as much space as two fridges equipped with ice machines.

2. 2018, a 5 terabyte hard drive that fits in the hand – available everywhere.

3. The worker pictured here is standing in front a rack containing 15 hard drives of 8 tb each. There are 8 racks per cabinet at this data centre there are 15 cabinets. Welcome to Facebook! Welcome indeed to your personal data (which by the way does not belong to you!)

 

Even more calculation

Take again the 16gb USB key which we have established contains 2 million pages. We would need 63 keys to make 1 tb ( 1000/16 gb)
Therefore, with 63 keys, we go from 2 million pages to 126 million pages  (315,000). This is only 1 tb – the 8tb drive would be nowhere near full!

Can we build the Eiffel Tower with this?

• A stack of 126 million sheets of paper! 500 sheets – 1 ream – of A4 paper measures 5cm high. 126 million divided by 500 gives the number of reams – 252000, each 5cm thick, so 12600000cm in total.

Go to https://www.wolframalpha.com/ This is a search engine that answers queries directly using curated external research and data. Type 126000cm and it will convert it to 12,600m or 12.6km.

The Eiffel tower is 324 metres. This means our paper pile is 38 times this height.

We have actually reached the limits of the troposphere.

 

 

 

 

 

 

Before the end the of the workshop, should 15 minutes remain, two questions can be asked:

1. How much music – in mp3 format – can you put on your 16gb key? This taking into account that a song makes up around 7 mb and lasts around 4 minutes on average.
2. Filling an 8 terabyte hard drive, how many hours of music could we have (Round to the nearest tenth)? To help participants, refer to this byte converter: http://byteconvert.org/

 

Answer for facilitator:

1. One 16gb USB key = 16384 gb. 16384/7 mb (1 mp3) = 2340 songs x 4 minutes = 9360 minutes = 156 hours or 6 days.
2. 1 tb = 1000 / 16 gb = 62 keys. 62 keys (representing 1 tb) x 8 = 496 16gb keys fill of music to make 8 terabytes. The 8tb disk contains thus 6 days of music multiplied by 496 usb keys = 2976 days or 8 years of non stop of 1,160,640 different songs. The ultimate playlist.