> Decades ago, Sears sold magnesium stepladders. I've used one, and it's freakishly light, a 6-foot step ladder that you can walk around with balanced on one finger.

As a slight aside, magnesium is also a very interesting material. It might be we're on the cusp of a major expansion in magnesium usage due to recent advancements

- Mining from seawater (about 1 kg Mg in 1000L of seawater), or existing brine tailings from other extraction activities. With cheap solar electricity this might drive the cost down considerably (below the extremely dirty production methods being used today in China), providing carbon-emission free production of essentially unlimited amounts.

- thixomolding, a die-casting / injection molding-like process where the material isn't completely melted (thixotropic state), producing parts with much less porosity than traditional die casting.

- New alloys that are less prone to fires and corrosion.

For slightly more details, see https://www.youtube.com/watch?v=OIv_Rfl0L_A