The engineer from roughly half a century ago might consider you to be less crazy if you started by thinking of the number of atoms in a mole, and the number of

The engineer from roughly half a century ago might consider you to be less crazy if you started by thinking of the number of atoms in a mole, and the number of atoms thus required to produce a sheet of metal. Then you could transition in to the incredible density that a wound up roll of magnetic tape must surely have, and postulate that if you could instead index it from the side like a record player's needle you'd end up with a rather massive storage density. Then you could explain that, more or less, such a thing had been done in this bespoke black box of highly advanced technology; and just look at these little bits on the circuits, electronic components of a tiny nature like you might see in some scifi film if you took apart a ray gun. Then you could say something about it either being alien, or more plausibly, time travel from the future being involved. I don't think you'd quite convince a scientist of the day that post-war research had continued at /such/ a remarkable pace of research as to allow that to be something produced by period technology.