|
03/16/2005
More Hot Bubbles
Where else but here in Southwest Florida would the subject of
traffic on a particular local road (not the infamous I-75) warrant
almost four full pages in the Sunday paper? As Brian Trumbore
mentioned in his Week in Review column after a recent visit, this
area is overdeveloped and traffic can be horrendous. The same
March 13 Sunday edition of the Naples Daily News included an
AP report by David Royse that highlighted another issue that
could well warrant future multi-page coverage – toilet paper! A
Florida state legislator has proposed a bill that would levy a tax
of 2 cents a roll on that crucial item, with the money raised by
the tax to be spent on wastewater treatment and upgrading of
sewer systems.
The handling of wastewater and sewage is an environmental
issue of considerable importance anywhere, especially in Florida.
However, the toilet paper bill is given little chance of passage
and apparently would require Governor Jeb Bush’s approval to
become law. Bush doesn’t seem too sure about the bill, opining
that the tax might lead to people using less toilet paper and he
wasn’t sure that would be a good thing. Needless to say, Florida
is flush with bathroom humor concerning the bill but we
certainly don’t want to stoop that low. Besides, there are other
newsworthy subjects that are more universal in nature.
For example, a cover story by Dan Vergano in the March 8
edition of USA Today reminds us that this month marks the
centennial anniversary of the first of Einstein’s seminal
contributions in 1905, his “miracle year”. In March 1905
Einstein answered the question, “How could light, a mere wave,
hit a metal or other surface and knock electrons out of the
material, the so-called photoelectric effect?” Einstein’s answer
was that light travels in “quanta”, little packets of light we now
know as photons. These photons carry enough energy to knock
out the electrons. This won Einstein his only Nobel Prize and
jump-started quantum mechanics, with its weird conclusion that
light behaves as both a particle and a wave.
Later in 1905, Einstein concluded that matter and energy are
related by the simple equation E = mc^2. Destroy matter, as
happens in nuclear fusion (as in the hydrogen bomb) and you get
energy. The Star Ledger of March 8 (both clippings from the
Ledger and USA Today kindly supplied by Brian Trumbore)
contained a lengthy obituary of Hans Bethe, who died last week
at the age of 98. Born in Strasbourg in 1906, his life just missed
overlapping Einstein’s miracle year. However, Bethe was a giant
in the field of physics who understood Einstein’s equation quite
well. Bethe won his Nobel Prize by showing that hydrogen and
carbon are involved in a nuclear fusion reaction that supplies
most of the power in our Sun and other brilliant stars.
Both Einstein and Bethe fled Nazi Germany in 1933, Einstein
ending up at Princeton and Bethe at Cornell. Einstein’s letter to
FDR prompted the Manhattan Project and Bethe became the
head of the theoretical physics division at Los Alamos. He and
his colleagues turned Einstein’s equation into the atom bomb
(nuclear fission), later followed by the hydrogen bomb. Bethe
was the last survivor of that group of superstars of the physics
world that worked on the Manhattan Project. He continued to
work at Cornell into his 90s, reputedly never learned to program
the simplest computers and brought out his trusty 70-year-old
slide rule when needed.
This morning, as every morning, I whip up a mix of a banana and
orange juice in a blender. I rinse the blender by whizzing it with
hot water, watching those many bubbles doing their job.
Invariably, I think of the work we’ve discussed in previous
columns by Taleyarkhan and coworkers at Oak Ridge National
Lab. For those who missed those columns, these Oak Ridge
researchers claimed to have found evidence of nuclear fusion in
bubbles. When bubbles expand and contract, there can be a large
amount of energy released and local bubble temperatures can be
quite high. Essentially, the Oak Ridge workers were saying that
the temperature in their bubbles was high enough to fuse
deuterium, a heavy form of hydrogen. After the cold fusion
hullabaloo some years ago, scientists tend to be skeptical of any
reports of fusion in a beaker, so to speak.
However, the March 7 Chemical and Engineering News had an
article by Ron Dagani on work related to the possibility that this
“bubble fusion” might be real. At Oak Ridge, they used
“acoustic cavitation” to expand and collapse the bubbles. In
acoustic cavitation, the liquid is blasted with ultrasound; the
ultrasound waves cause the pressure to rise and fall rapidly,
leading to the desired expansion and contraction of the bubbles.
Dagani’s article refers to recent acoustic cavitation work by
Kenneth Suslick and graduate student David Flannigan at the
University of Illinois. The work, published in a recent issue of
Nature, does not confirm bubble fusion but holds out hope that
fusion in bubbles might be possible.
It has long been known that under certain conditions cavitating
bubbles give off light, so-called “sonoluminescence”. This light
is typically pretty weak in intensity. However, most studies were
done is water or some sort of water solution. A bubble in water
contains water vapor. We all know water is H2O and must have
bonds between hydrogen and oxygen. In a collapsing bubble,
most of the energy released is taken up by the water vapor
molecules. This energy goes into vibration and bending of
bonds, leaving little energy to be released in the form of light.
What Suslick and Flannigan have done is to study the
sonoluminescence in cavitating single bubbles in sulfuric acid.
The bubbles were filled with either argon or xenon. Sulfuric acid
has a low vapor pressure and the argon or xenon gas in the
bubbles is in the form of atoms, not molecules. There aren’t any
bonds to bend or vibrate. As a result, more energy is emitted as
light thousands of times more intense than the light from bubbles
in water. The Illinois researchers also found that, with more
intense light, they can detect and measure intensities of spectral
lines, something they couldn’t do with bubbles in water.
Suslick and Flannigan used these spectra and the intensities to
deduce two important results. First, the temperature inside the
bubble was found to be more than 15,000 degrees Kelvin. This
is 3 or 4 times the temperature on the surface of the sun! It’s
truly hot in those bubbles. Second, they found spectra
corresponding to an oxygen molecule with a positive charge,
O2+. This means an electron has been knocked out of the
molecule.
The finding of the charged oxygen molecules has an important
consequence. The high temperatures in the bubble would not
cause an electron to fly off; the heat would break the bond
between the two oxygen atoms in the molecule. The workers
conclude that the electron is knocked off in collisions with other
ions or electrons in the bubble. The existence of the charged
molecule indicates that the cavitation of the bubble creates a
plasma, a mix of charged ions and other charged particles.
Creation of a high energy plasma in a bubble is just the sort of
thing that you would hope for if you’re shooting for fusion.
Suslick is careful to point out that no nuclear fusion has been
detected. Their system differs from that employed by the Oak
Ridge workers, who used acetone in which the hydrogen was
replaced with deuterium, which fuses at a lower temperature than
ordinary hydrogen. The Illinois workers are now working on
sulfuric acid in which the hydrogen is replaced with deuterium.
Meanwhile, I’ll keep a sharp eye out for any nuclear fusion in my
banana-orange juice blend.
Allen F. Bortrum
|
