Fermi estimate: data throughput of a jumbo jet carrying CDs across the Atlantic

A Boeing 747 is packed with CD-ROMs and flown across the Atlantic. Treat the trip as a way of moving data and estimate the bandwidth it delivers, in bits per second. ```hint Find the binding limit A full cargo hold can run out of more than one thing. Work out which limit you would hit first before you count discs. ``` ### Clarifying Questions - Should I assume a freighter 747, or a passenger version with the cabin stuffed with discs? - Are the discs bare on spindles, or packed in jewel cases? - Which crossing should I use, for example New York to London, and does the clock run only for the flight or door to door, including burning the discs and reading them back? - Is an order-of-magnitude answer enough, or do you want a tighter range? ### What a Strong Answer Covers - A clear equation: data carried divided by transfer time, with bytes converted to bits exactly once - Labeled round-number assumptions for disc capacity, disc size and mass, aircraft payload and cargo volume, and flight time - A check of whether weight or volume caps the number of discs, using the other as a cross-check - Arithmetic carried through to bits per second, plus a sanity check against a familiar network link - The difference between throughput and latency, and how the figure drops once writing, loading and reading the discs are counted ### Follow-up Questions - How does your number change if the clock includes burning the discs before departure and reading them after landing? - What happens to the estimate if the cargo is modern hard drives instead of CDs, and what does that say about which property of the storage medium matters? - When would you advise a team to ship physical storage to move a large dataset instead of sending it over the network?