Physics demonstrations: The Phantom Lightbulb

Some of the most spectacular physics demonstrations rely on surprisingly simple science.  Throughout history, for instance, very simple optics has been used to great effect to terrify and amaze audiences (see, for instance, Robertson’s Phantasmagoria).  I recently came across such a demonstration on YouTube, and decided to make my own version, as shown below.

I like to call this the “phantom lightbulb illusion” [1].  Its operation can be seen at the end of the video, and described as follows.  A functioning lightbulb is placed in a socket upside-down inside of a box, while an identical socket is empty directly above.  When the bulb is turned on and the box is in the proper place, the concave mirror in front of the box produces a real image that lies directly above it.  As long as one keeps the empty socket between the observer and the mirror, the image will remain in the proper place.


This is, in short, how the illusion works, but doesn’t explain why it works — that is, what is the underlying optics that creates the image in the proper place?

What a great opportunity for me to explain a little bit of geometrical optics!  By the end of this post, I will have described the basic theory of image formation in concave mirrors and, hopefully, we’ll really understand why the “phantom lightbulb illusion” works.

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How many quarks would a charm quark charm if a charm quark could charm quarks?

Fundamental physics is having quite a spectacular season.  In mid-March, the collaborators of the BICEP2 telescope announced the first direct evidence of cosmic inflation, answering a long-standing question about the beginnings of the universe.

Now, on the heels of that discovery, the LHCb (Large Hadron Collider beauty) collaboration at CERN has announced the discovery of a new particle — an exotic hadron that has four quarks in it, instead of the usual three quarks or quark-antiquark pair.  Such a beast lies outside our current understanding of particle physics, opening the door to even more revelations about our universe.  Matthew Francis has another nice summary of the discovery at Ars Technica.

The details of this discovery, and its long-term implications for physics, are out of my depth these days (I haven’t been a particle physicist for a while).  However, the press releases assumes a lot from the reader — do they know what quarks are, and why they only come in threes or quark-antiquark pairs?  With this in mind, I thought I could write a short post giving some background for those who aren’t familiar with the details — the “Cliff Notes” of quarks, so to speak! As I tend to do, I’ll approach this from a historical perspective, though this history will be simplified for the sake of brevity.

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The House of the Wolf, by Basil Copper

I haven’t been reading much fiction as of late, thanks to work and a desire to catch up on a lot of science reading.  This past week, however, I jumped back into the fiction, picking up Basil Copper‘s 1983 novel The House of the Wolf.


It is not difficult to deduce from the title that The House of the Wolf is about werewolves!  In fact, that realization made me reluctant to pick up the book, which has been sitting on my shelf for at least six months, simply because I (personally) find werewolf stories a little tedious. (One notable exception: Valancourt’s collection of very early werewolf stories that I’ve blogged about before.)

As I should have known, however, from my previous experiences with Copper’s writing, The House of the Wolf is quite fun!  A Gothic novel similar to his earlier Necropolis (1980) and his later The Black Death (1991), it is a mixture of horror and mystery that is slow to start but quite stunning by the end.

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My appearance on WCNC television!

Today I appeared on NBC Charlotte on “Larry’s Look” to promote our upcoming UNC Charlotte Science and Tech Expo and show off some science demos!  You can check out the video at this link.  Don’t ask me what I thought of it yet, as I usually wait a few days before watching my television appearances!

This makes my third appearance, I believe, after an appearance on WCCB TV last year to talk invisibility and cloaking and a short spot on News 14 Carolina (now Time Warner Cable News) that I can’t even find any more.

I love doing these appearances because it gives me an opportunity to see “behind the scenes” at how news crews work.  Larry Sprinkle was a lot of fun to work with and the cameraman was awesome — no problem with any of my crazy stuff! :)

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The Curse of “Asshole Ra”

Updated with even more assholeness of Ra!

Twitter is a great place to waste time, but it is also a great place to get inspired with really ridiculous ideas.  After I pointed out that a sequel to the movie Prometheus is in the works, PZ Myers of Pharyngula responded with this tweet:

My response was this:

And a new meme was born! Ra, for those unfamiliar, is the ancient Egyptian deity of the midday sun, a major god of Egypt from somewhere about 2500 BC onwards.  He was typically represented with a falcon head, and sun disk on top of it, as pictured below.

A lovely depiction of Ra, via Wikipedia.

A lovely depiction of Ra, via Wikipedia.

The ancient Egyptian god Ra is a powerful, benevolent deity, responsible for the creation of life and the one who protects and sustains it.  On the other hand, Asshole Ra is petty, annoying, and pretty much, well, an asshole.

Taking classic Egyptian artwork of Ra from around the web, I produced my own conception of Asshole Ra.  Go below to see his glory…

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Curves… in… spaaaace! (1890)

One of the tragedies of STEM education is the seemingly eternal perception by the general public that mathematics is boring and repetitive.  Most people, of course, end their math education with algebra at most, though some work their way through a calculus course before leaving for good.

This is a tragedy because mathematics is one of the best fields to find incredibly beautiful objects, experience mind-blowing concepts that challenge ones imagination — or sometimes both simultaneously.

A wonderful example of this is the geometric object constructed by the Italian mathematician Giuseppe Peano and described in his 1890 paper “Sur une courbe, qui remplit route une aire plane.”  This beautiful and mind-boggling object is illustrated below.


Uh… wait a minute…

*shuffling of papers as I check my notes*

No, that is correct!  The object above is obviously a square, which at first glance would seem to be the most boring geometric figure possible.  What Peano did, however, was demonstrate a new way to fill the square, inventing a mathematical construction that allows the square to be completely filled in with a single, continuous line!  This “Peano curve” was the first example of what is now known as a space-filling curve, which has surprising and insightful connections to modern mathematics.

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John Blackburn’s The Cyclops Goblet

Another new Valancourt Books edition of a classic John Blackburn book has been released, and it includes another masterful* introduction by me!  This time, the book is John Blackburn’s 1977 novel The Cyclops Goblet.


John Blackburn (1923-1993) was a prolific author of books containing a unique blend of thriller, science fiction and horror, producing some 25 novels over the course of his career (I talk about a number of them on this blog).  His work was also extremely popular in his time, but was sadly almost completely forgotten after his death — until Valancourt started reprinting his books over the past year.

The Cyclops Goblet marks an interesting departure from Blackburn’s usual fare.  It can be considered a classic “caper” story, in which a series of crooks attempt to pull off a spectacular heist — and try to double-cross each other in the process!

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