Monumental Quirks

August 04, 2008

Mankind does love its monuments -- even physics has its chosen landmarks. Case in point: Washington, DC, boasts a famous bronze sculpture of Albert Einstein on the southwest corner of the National Academy of Sciences building. Sculptor Robert Berks placed his larger-than-life physicist inside a circular granite dais embedded with some 2700 metal studs. Those studs aren't just arbitrary: their placement represents the locations of various astronomical objects at the exact date and time when the great Einstein was born.

The inscriptions on the "pages" the bronzed Einstein holds in his left hand aren't arbitrary either: they are the equations for the photoelectric effect (for which he won the Nobel Prize in Physics); general relativity; and his most famous contribution to physics, the equivalence of energy and mass (E=mc<2>).

It all started when scientists noticed something strange about the periodic table of elements. The atomic number of an atom shows how many protons it has (and therefore which element it is), while its atomic weight includes both protons and neutrons.

[UPDATE: In the interests of brevity, I elided over some critical technical points in my original post. A couple of scientists (including my own spouse) were nice enough to email and alert me to this misleading error. Below is my revised version of the problematic paragraphs, because this makes for an excellent "teaching moment," not just for me, but for my readers. And I encourage those who want to learn more to (a) follow the links included in posts, and (b) explore the wonders of Google on their own.]

The problem of the missing mass had to do with the fact that the atomic nucleus always weighs less than the total mass of the protons and neutrons -- which violates energy conservation. So where did the missing mass go? Physicists really don't like to see their laws violated in this way (and they really don't like to see over-simplified explanations of nuclear decay on blogs!). But they had to wait until 1905 for a satisfactory solution, when Einstein showed that mass can be converted into energy and vice versa. The two are equivalent, and interchangeable.

So, the atomic weight of an atom is the masses of the protons and neutrons plus the binding energy (because mass and energy are equivalent). Fair enough. The catch is, the binding energy is always negative, so you always get a slightly smaller number than when you started. Problem solved, and in the process, scientists realized they had a nifty source of energy. When an atom loses protons or neutrons, this changes its atomic weight, and the lost mass is radiated as energy, causing the atom to get lighter and disintegrate into an isotope of the same element, with the same number of protons but fewer neutrons. Or it could decay into a different element of lesser weight if it loses protons. Iron is the most stable element so it serves as a sort of boundary between the lighter and heavier elements. You can fuse lighter nuclei, which then release energy, or you can split heavier atomic nuclei (fission)  to release energy.

I've veered off into nuclear decay for a reason. There's an even stranger monument of sorts to Einstein in the Netherlands: a large orange building called the Haborg Facility, which is covered with physics equations by Einstein and Max Planck. It's a monument to nuclear decay, specifically. The building is chock-full of nuclear waste from two nuclear reactors in the Netherlands, and recently made the list of "10 Most Bizarre Monuments" over at Oddee. [WARNING: two of the other nine featured monuments are NSFW.]

See, they needed a place to store this pile of nuclear waste materials for 100 years or so, at which point the waste would no longer be radioactive. Artist William Verstraeten came up with the idea of turning the problem into an art installation. Every 20 years, the building will be repainted in a lighter color to symbolize the slowing decaying radioactivity in the waste materials. Apparently, it's even open for tours, and won an award earlier this year for "most beautiful waste facility." I have to wonder how stiff the competition was in this particular category, but clearly, one man's radioactive trash can become another man's treasure.

Photos: (top) Albert Einstein Memorial in Washington, DC. Source: Wikimedia Commons. (bottom) Habog Facility, the Netherlands.

Comments

[Phil S. Ioannou]

Hi,

'scuse my density but if Einstein was born on Talk Like a Physicist Day, March 14 per the Wikipedia link in your main Blog on that date, then how was he also born at noon on April 22 as stated above ? Did I miss some kind of historical correction news somewhere along the way ?

Luv all your work.
By any ( Quantity x Quality ) Blog Rating index, your rating would be astronomically large IMO and I don't even see the stuff you write for income purposes.

Tout en esperant que ca ne changera jamais ... merci !

Warmest Regards from Montreal.

[Jennifer Ouellette]

Doh! This blog post is cursed... cursed, I tell you! I totally should have caught that... Just goes to prove that Wikipedia has its inaccuracies. Anyway, I've edited the post yet again to correct it.