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Ice is a very common solid here on Earth yet one of the most puzzling. Take the seemingly simple question, “Why is ice slippery?”, for example. Common wisdom says that when you step on an icy surface the pressure melts the ice a little bit to create a thin layer of water that acts as a lubricant. It’s due to the unique property of water: the solid form is less dense than the liquid form. We take it for granted that an ice cube will float in a glass of water, but for most material the solid form would sink to the bottom. And because ice has a lower density it is also true that the melting point of ice is depressed as pressure increases.

Ice has a hexagonal crystal structure, but what happens at the surface boundary to make ice slippery?

The theory goes that as you walk on ice the increase in pressure lowers the melting point of the top layer of the ice and it melts for a brief moment, then refreezes as you pass by. The problem with this explanation is that the effect is very small and would only reduce the melting point by a few hundredths of a degree at most. Yet ice is still slippery when its temperature is far below the melting point.

One possible explanation is that friction plays a part as well. The act of walking on ice creates friction which heats the ice to create a slippery surface. But the problem with this is that ice is still slippery regardless of whether or not you are moving. If you are standing still there is no friction, yet it’s still slippery.

A better theory is that ice has an intrinsic liquid layer. Water molecules at the surface remain unfrozen because there are no molecules above them to hold them in place. This was first proposed in 1859 by Michael Faraday who noticed that two ice cubes will fuse together if they are pressed against one another. Faraday’s explanation for this is that the liquid layers freeze when they are no longer at the surface. But even this theory is not quite correct.

In 1996, a team led by Gabor Somorjai, a professor of chemistry at Lawrence Berkeley Laboratory, bombarded the surface of ice with electrons. By observing how they bounced off they were able to make an amazing discovery: What actually makes the surface of ice slippery are rapidly vibrating water molecules. These “liquid-like” water molecules do not move from side to side—only up and down. This is an important distinction. If the atoms moved from side to side, the layer would actually become liquid, which is what happens when the temperature rises above 0° C. It turns out that it is this “liquid-like” layer that makes ice slippery.

1) True or false: Ice floats in water because it is more dense.

2) The best theory to explain why ice is slippery relies on _________.
a) friction b) pressure c) a liquid-like surface layer d) all of the above

3) True or false: An increase in pressure will reduce the melting point of ice.

4) Michael Faraday first demonstrated that ice has an intrinsic ____________.
a) liquid layer b) hexagonal structure c) chemical makeup d) cubic structure

5) Research at Berkeley reveals that ice has a surface layer that is _________.

Delicate Arch, the most famous of the over 2,000 arches in the park.

Arches National Park contains more than 2,000 natural stone arches—the greatest concentration in the world. But this pales in comparison to the grandeur of the landscape—contrasting colors, textures and landforms unlike anything else on the planet.

Located above the Colorado River in southern Utah’s high desert, the park is part of an extended area of canyon country, sculpted by millions of years of weathering and erosion. 300 million years ago, inland seas covered the region. The seas filled and evaporated—29 times in all—leaving behind salt beds up to about 4,000 m thick in places which is known as the “Paradox Formation” today. Later, sand and material carried down by streams from the surrounding uplands buried the salt beds beneath thick layers which later became cemented into rock. Most of the formations at Arches are made of this red Entrada sandstone and tan Navajo sandstone that was deposited 150 million years ago.

The salt beds, under tremendous pressure from the weight of the overlying sandstone, became unstable and began to flow. This movement caused the overlying rock to move and buckle. Some sections were thrusted upward into domes, while other sections dropped into the surrounding cavities. Vertical cracks developed which would later contribute to the creation of arches.

As the movement of salt deep underground shaped the surface, erosion carried away the younger layers of rock. Water seeped into the rock through cracks and washed away loose material and eroded weaker portions of the sandstone, leaving a series of free-standing vertical fins. Ice formed during colder periods would expand and put pressure on the rock, breaking off chunks and created openings. Many of the fins collapsed, but some that were harder and more resistant to the erosion survived to become the spectacular stone sculptures that we see today.

Landscape Arch, the longest arch in the park and the second-longest arch in the world.

Although the park has timeless beauty, it is not indestructible. The same powerful forces that nature harnessed to carve these extraordinary arches will eventually tear it down. Wall Arch, a photographer’s favorite that was ranked 12th in size, collapsed in August 2008. Landscape Arch, which at 88 m is the longest arch in the park and the second-longest in the world, is facing a grim future at the destructive hands of gravity and erosion. Since 1991, three slabs of sandstone have fallen from the thinnest portion of the arch and the park has had to close the trail which passes beneath it to protect visitors from its eventual demise.

1) True or false: Utah was covered by inland seas 300 million years ago.

2) The characteristic red sandstone at Arches National Park is called _______.
a) Navajo sandstone b) the Paradox Formation c) Colorado Formation d) Entrada sandstone

3) True or false: Landscape Arch collapsed in August 2008

4) The free-standing vertical slabs of stone that developed as a result of erosion are called ___________.

5) The Paradox Formation is thousands of meters thick and composed of ____________.

I was looking around on the internet last night, searching for ideas for my next column when I found an article titled “50 Interesting Science Facts”. One of the items it listed was “If our Sun were just [an] inch in diameter, the nearest star would be 445 miles away.” Wow, I thought, that really illustrates the vastness of space pretty well. Maybe I could use it somehow. But I was a bit suspicious because the comparison didn’t use the metric system, and we all know that any scientist worth their NaCl uses the metric system! Also, it had a typo—the word “an” was omitted before the word inch. In my day-job I do a lot of proofreading and copy editing so typos always make me suspicious. What the heck, I thought, lets run the numbers and see if it checks out.

According to NASA and Wikipedia, the diameter of the Sun is about 1,390,000 km, and the nearest star to us, Proxima Centauri, is 4.22 light years away, or 39,900,000,000,000 km (written as 3.99 x 1013 km in scientific notation). So if we divide the latter by the former, we find that the ratio of distance to diameter is 28,700,000 : 1, so if the Sun were one centimeter in diameter, the nearest star would be 287 km away. Sounds about right, but lets convert to American units to be sure. The number of inches in a mile = 12 in/ft x 5,280 ft/mi = 63,360 in/mi. So if we take our distance to diameter ratio, 28,700,000 and divide by 63,360 in/mi we find that, in fact, if the Sun were one inch in diameter the nearest star would be 453 miles away. Our “interesting fact” is off by eight miles, or about three percent! If they had just written that it would be about 450 miles away I would have no problem, but when you present information to three significant digits then it should be accurate to three significant digits.

But now things get even more fun, because on the internet an incorrect “fact” gets propagated far and wide rather quickly. Doing a Google search on “If our Sun were just inch in diameter, the nearest star would be 445 miles away.” it turns out that I wasn’t the only one that thought it was an interesting fact, just the only one to check it. There were over 3,000 results that had the same incorrect information, and all but nine of them had kept the typo as well. Even a monkey can copy and paste I guess!

Google returns 3,010 search results for “If our Sun were just inch in diameter, the nearest star would be 445 miles away.”

Good science requires attention to detail and willingness to question everything, and I want to encourage my readers to take the time to check details and ask tough questions. So instead of a quiz this week I have a challenge instead: find your own scientific “fact” that is incorrect and report it to me, either by e-mail (douglasclark@sbcglobal.net) or through my Facebook page (keyword weeklysciencequiz). If you find something I’ll give you credit on an upcoming article. Happy hunting!

Located in the foothills of the San Gabriel mountains in Pasadena, JPL is NASA’s research laboratory that is managed by Caltech. JPL’s primary mission is space exploration using robotic spacecraft. This past weekend I had the good fortune of being able to attend JPL’s annual open house event, and I was pleasantly surprised by how many people were there, with lines of people waiting patiently to get into one of the 20+ exhibits. We were able to view 3D stereo images of Mar’s surface as well as watch a short 3D movie about the Earth. We were able to see how NASA missions are using JPL’s infrared imaging technology to create incredible photos of distant stars and galaxies. We also saw how exoplanets are being discovered at an ever-increasing pace in an attempt to find other Earth-like planet in the cosmos capable of supporting life.

The Martian Science Laboratory rover (right) on display at JPL and in comparison with the Mars Exploration Rover (left) and Sojourner rover (center).

There were several rovers on display, the most-impressive being the full-scale next-generation Mars Science Laboratory (MSL) rover. Named Curiosity, the MSL is scheduled to launch this fall and make a precision landing on Mars in August, 2012. Curiosity, with its array of scientific instruments, will be able to help assess whether or not Mars either now or at some time in its past is able to support microbial life forms.

2011 is a very busy year for JPL. Besides Curiosity, in June JPL’s Aquarius satellite will be launched. Aquarius will map the salinity of the Earth’s ocean surfaces. This information will be used to improve our understanding of the oceans’ role in the water cycle by tracking how fresh water is exchanged between the atmosphere, sea ice and oceans. By measuring changes in ocean surface salinity, as well as melting ice and river runoff, Aquarius will provide new information about how freshwater moves around our planet which will help improve computer climate models as well as our understanding of worldwide ocean currents.

In August, NASA will launch JPL’s Juno explorer which will, by 2016, begin orbiting Jupiter to study the planet’s composition as well as gravitational and magnetic fields, and polar magnetosphere. Juno will look for clues about how Jupiter was formed: whether it has a rocky core, how much water is present deep within the atmosphere, and what the mass distribution is within the planet. Juno will also study Jupiter’s violent storms where winds can hit speeds of 600 km/h. With all the activity going on at JPL, we can be assured of many new discoveries in the near future which I look forward to covering in more detail as they occur.

An artistic conception of Juno orbiting Jupiter.

1) True or false: JPL is managed by NASA.

2) Curiosity is the name of JPL’s ____________.

a) Mars Science Laboratory b) Earth satellite. c) Mars Exploration Rover d) Jupiter satellite

3) True or false: JPL’s primary mission is to explore space with robotic-controlled spacecraft.

4) The Aquarius satellite will help us understand ___________.

a) exoplanets b) Earth’s climate c) the salinity deep under the ocean surface d) Jupiter’s atmosphere

5) Juno will explore __________.

Fusion’s Future

This week we will wrap up our series on nuclear fusion by taking a look at one possible scenario for the future of fusion and how it could eventually play a part in ending our reliance on oil and natural gas.

Even though nuclear fusion does not produce radioactive waste directly, it does produce neutron radiation which does require shielding. But some fusion reactions are aneutronic. One such reaction is a pure reaction of helium-3 where two He3 nuclei fuse to create one helium-4 nucleus and two protons. Since the protons are electrically charged, they can be contained by an electric or magnetic field. And it gets even better, because by containing these protons it would be possible to convert this energy directly into electricity, bypassing the need to heat water and create steam which runs through turbines which then powers electric generators.

The fusion reaction of two helium-3 atoms yields one helium-4 atom and two protons plus energy.

But there are some problems, the biggest of which is that helium-3 is virtually nonexistent here on Earth. Our closest source for helium-3 is on the Moon, which has sparked a new space race which may one day lead to mining on the Moon. China, Russia, India, Japan and Germany have all declared their intention to make it to the Moon with the intent of eventually mining helium-3 and bringing it back to use as fuel for fusion reactors here on Earth. NASA, too, is scheduled to be on the Moon by 2020 and to have a permanent base by 2024. And while NASA has not specifically came out and declared an intention to mine helium-3, it does have advocates of helium-3 mining in influential positions.

The other problem is the extreme temperature required in order to begin a fusion reaction of pure helium-3, which is estimated to be six time hotter than the interior of the Sun. The only research facility currently doing successful helium-3 fusion reactions is at the Fusion Technology Institute at the University of Wisconsin-Madison, where they have been able to confine the reaction with a technology known as inertial electrostatic confinement (IEC). The benefit of IEC is that it doesn’t need a massive confinement structure—their experiment is table-top sized. It is estimated that we are 50 years away from creating clean fusion energy, but the potential advantages are so great there is no doubt that research will continue and possibly one day in the not-to-distant future clean energy will be more than just a dream.

1) True or false: Helium-3 is abundant here on Earth.

2) Helium-3 has ____ neutrons in it nucleus.

a) 1  b) 2  c) 3  d) 4

3) True or false: In order to create a fusion reaction of pure helium-3, temperatures in excess of those at the interior of the Sun are needed.

4) The technology currently being used to contain helium-3 fusion reactions is called _________________ (IEC).

a) initial early consignment  b) inertial electrostatic confinement  c) inertial elementary confoundment  d) internal electrostatic confinement

5) The closest place to mine helium-3 is at __________.

Cold Fusion made the cover of
Time magazine’s May 1989 issue.

In the spring of 1989, Stanley Pons and Martin Fleishmann, in partnership with the University of Utah, claimed that they were able to create a fusion reaction in a test tube at room temperature. By the first week of May, 1989, the news had made the cover of Business Week, Time and Newsweek—the first time the same story had been on the cover of all three magazines since the Kennedy assassination. Clearly this was big news. There was a tremendous desire for this to be true: The Chernobyl disaster was still fresh in people’s minds having occurred a year previously, and the day after the press conference the Exxon Valdez oil spill occurred. People wanted to believe in the possibility of a cheap and abundant source of energy that didn’t create greenhouse gasses or radioactive waste.

But before we get into the specifics of what happened, lets review what nuclear fusion is and how it works. Fusion is when two smaller atoms fuse together to make a larger atom. The most common form is hydrogen fusion, where two hydrogen atoms combine to form a helium atom, releasing massive amounts of energy in the process. This is what occurs in our Sun and in most stars. The benefit of fusion compared to its nuclear cousin, fission, is that it does not create any radioactive waste products. The downside is that it is much more difficult to create and contain. Hydrogen fusion itself can happen in several different ways, depending on the various isotopes involved. 99.98% of hydrogen has a nucleus with only a single proton (1H). Deuterium (2H) is a stable isotope that contains one proton and one neutron in its nucleus and tritium (3H) is an unstable isotope that contains one proton and two neutrons. The process that fuels our sun combines deuterium and tritium to make helium.

Deuterium fusion: two deuterium atom fuse to create helium 4, releasing energy in the process, which then either ejects a proton to create tritium, or ejects a neutron to create helium 3, releasing more energy in either case. (Neutrons are shown in blue and protons are shown in red.)

The nuclear process that was put forth as the mechanism for cold fusion used deuterium only, produced by running an electric current through heavy water (D2O). This causes the water molecules to split, liberating deuterium. The electrode in their experiment was made of palladium, which would then absorb the deuterium gas. Palladium has the uncommon ability to absorb up to 900 times its own volume of hydrogen at room temperature. The claim was that as the palladium absorbed the heavy hydrogen, its temperature shot up, and according to Fleishmann and Pons, created a net surplus of energy. So much energy, in fact, that during one experiment the water burned a hole in the beaker, the lab table it was sitting on top of and the floor below it.

Sounds great, right? Energy so cheap it wouldn’t even be worth metering. But shortly after their press conference, problems began to develop. The first problem was that they were not able to propose a mechanism for how fusion could occur at room temperature. In order to fuse atoms, one must overcome the substantial electrostatic force when you try and bring two positively-charged nuclei close enough together so that the strong nuclear force will be able to act upon them. Normally it would require temperatures in excess of 120 million °C. To say that the deuterium gas is compressed 900 times by a palladium electrode isn’t going to even get you close. Consider, for example, the planet Jupiter which has a layer of hydrogen near its core that is believed to be in excess of 30,000 °C and pressure tens of thousands of times greater than normal atmospheric pressure on Earth, yet this is not enough to fuse hydrogen which is why the gas giant is a planet and not a star.

Another problem was that their experiment was set up to measure heat and not the by-products of nuclear fusion, specifically neutrons, gamma rays, helium and tritium. In the following weeks, several labs were announcing that they could reproduce parts of the experiment, but not all. The Department of Energy could not reproduce the results. And despite all the claims, in the end there was never any solid evidence for the production of helium, gamma rays or neutrons. A few labs found small amounts of tritium, but not enough to be more than what could be explained by contamination. These labs were in the business of measuring nuclear products and thus had plenty of sources of possible contamination—something very difficult to avoid when you are looking for such low levels in the first place.

It turns out that data had been altered before going to congress to appeal for funding. A graph had been fudged to match expected results. By May 1989, the gig was up. The American Physical Society held a session on cold fusion, at which many reports of failed experiments were heard. At the session’s end, eight of the nine leading speakers said they considered the initial Pons and Fleischmann claim dead. Steven Koonin of Caltech called the Utah report a result of “the incompetence and delusion of Pons and Fleischmann” which was met with applause. Physics Today, in a 2005 report, stated that new reports of cold fusion were still no more convincing than 15 years previous. Its a good reminder that we must always rely on the scientific method to arrive at the truth.

1) True or false: Palladium is able to absorb up to 800 times its own volume of hydrogen.

2) Which of the following is not a by-product of fusion?
a) heat  b) neutrons  c) helium  d) heavy water

3) _________ is a stable isotope of hydrogen.
a) protium  b) deuterium  c) tritium  d) helium

4) In order to fuse two positively-charged nuclei, you must overcome a substantial _______ force.
a) strong  b) electrostatic  c) gravitational  d) nuclear5) What does science rely on to arrive at the truth?

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