Light Lens a Hand, to Help us Understand

I hate to see cool things go to landfill. Today’s Object at Hand is a compound lens that I pulled from the shattered remains of a rear-projection big-screen television that was discarded in the alley.

Compound Lens

Peering through a lens

Other scavengers had already smashed and gotten all the easy copper from the mangled cabinet. I reached into the pile and twisted out the three lens units. It took a few minutes for me to open the casing of one, so that I could see the four internal lenses. The second from the right is a heavy, asymmetric, double convex glass lens with which any child would be proud to burn, um, leaves. The others have much more subtle and intricate shapes, the better to focus the images of the three color projectors onto the screen.

I am a big fan of images, shadows, reflections, and projections. I mean this in both the literal, visual sense and in a metaphorical sense. A lens is actually a marvelous thing.

Einstein theorized, and a century of subsequent testing has confirmed, that the speed of light is absolute, in a vacuum. But light actually slows down passing through matter, or even gravitational fields. A lens can focus light because glass actually slows light down by 33%.  The first inventors of lenses didn’t know that. But we have much better lenses now because we now know how they work.

I like to see the world through a variety of lenses. As Galileo and Leeuwenhoek proved, a lens reveals a much wider world than that to which our own senses can testify. It is through the use of various lenses that we have expanded our understanding of nature so vastly in the last 400 years.

By “lenses”, I mean more than just lenticular pieces of glass (the word “lens” comes from the double-convex shape of the lentil). Any instrument or technique that improves our ability to apprehend things can be considered a lens. Newtonian telescopes use a concave mirror as the primary lens. Radio telescopes use arrays of huge dishes of lacy steel covering miles as a single lens. Electron microscopes use a beam of electrons, and the scanning-tunneling microscope uses a mechanical pointer to trace the outlines of individual atoms.

We also have tools to let us see events that happen too quickly or too slowly for our natural senses. Edgerton’s xenon flash first allowed us to clearly see things like a bullet passing though a card, or to stop the beat of hummingbird wings. During WWII, they built X-ray cameras that could watch the effects of high explosives slowly unfold as they compressed small spheres of heavy metals during a few microseconds. And to watch the mushroom cloud rise as a result.

On the other end, time lapse photography lets us watch with excitement as paint dries and plants grow and seasons change and glaciers flow. Careful record keeping and carefully tested theories gives us lenses that allow us to precisely monitor events that take place over centuries or even billions of years.

We can now see that the universe is much more complex and beautiful than was possible to conceive of a few centuries ago. And that’s the sort of thing that pulling a lens from the trash brings to mind.

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2 Responses to “Light Lens a Hand, to Help us Understand”


  1. 1 Phil G-E April 27, 2010 at 2:58 pm

    Here’s looking at you, kid. Nice perspective.


  1. 1 Another Musing on Our Evolving Ability to Perceive | Dangerous Intersection Trackback on April 27, 2010 at 11:54 am

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