Cloud Atlas

Atoms are made of electrons, protons and neutrons. Protons and neutrons are in turn made up of quarks. These are just some of the elementary particles that make up the foundation of modern particle physics. But how do we know about these particles when we can’t see atoms directly, much less their constituents? One of the early methods was through a device known as a cloud chamber, and it is quite a clever invention.

The basic idea of a cloud chamber is a seal container filled with alcohol vapor. The vapor is cooled to the point that it is supersaturated. Because of this, small disturbances can trigger the formation of small alcohol droplets, which appear as a streak of mist or “cloud” (hence the name). When the container is made with transparent sides, then the cloud trails can be easily seen, and even photographed.

What makes this device useful for particle physics is that droplets can be triggered by charged particles passing through the chamber. A trail of droplets forms along the path of the particle, and by observing these trails we know that a charge particle has passed by. Cloud chambers provided the first observation of cosmic rays, appearing as random streaks in an isolated chamber. They also demonstrated that radioactive materials emit charged particles, since trails appeared when radioactive materials were placed near a chamber.

By itself, a cloud chamber can only show that a charged particle has passed by. It can’t distinguish the type of charged particle, or even the sign of its charge. Thus it can’t distinguish between protons and electrons, for example. To distinguish particles you also need a magnetic field.

When a charged particle moves through a uniform magnetic field, it experiences a force perpendicular to its motion. This means the magnetic field doesn’t affect the speed of the particle, but instead changes its direction. As a result, the charged particle will move in a circular path. The direction the particle circles depends upon the sign of its charge, and the size of the circle depends upon the particle’s mass. By placing a magnetic field through a cloud chamber, one determine the charge and mass of particles by their circular trails. This is how the first positron (anti-electron) was discovered. It produced a circular path that was the same size as an electron’s, but in the opposite direction.

While cloud chambers gathered the first crucial evidence for particle physics, they had the downside of having fuzzy cloud trails. This meant that getting precise observations was often difficult. The trails also diffused quickly, making them hard to study. In 1952 a similar device known as a bubble chamber was invented. This used critically heated liquid rather than vapor, and charged particles would produce a trail of vapor bubbles. This was particularly useful for early high-energy particle physics. Since then a range of other particle detectors were developed, and now particle physics is typically done with sensitive detector arrays.

As our understanding of particle physics increased, so did our understanding of the universe. Black holes, neutron stars, supernovae and the big bang are just a few of the phenomena we now understand thanks to particle physics. And the cloud chamber is what allowed us to make crucial breakthroughs in the early 1900s.

My favorite material for lapidary

The picture does a poor job of conveying the color and depth.
From a distance they look like bright turquoise, but up close you see it is glowing opal.

I cut these from a single stone that was so consistent in color I was transfixed by it. When you are grinding the shape you are lapping through the "fire" of the stone, so the final character of the stone is unknown until you get close, in the final smoothing - then the polish brings it to life.
A surprise every time.
Being a softer stone, opal is not best suited for a ring where it is subjected to abuse as opposed to a necklace, but it is beautiful on her hand.

I alloy my own gold to a favorite formula for a dark yellow 14k. Rolling out small ingots for sheet and pulling my own wire through draw plates.
These pieces are constructed, I usually cast using lost wax and investment.
I also make rubber molds for wax injecting when I wished to reproduce a design, but not much in the way of production anymore. 50 of the same pieces took the thrill away, too much like a job.
Now my bench sits and waits for my inspiration to strike.


My favorite material for lapidary

The picture does a poor job of conveying the color and depth.
From a distance they look like bright turquoise, but up close you see it is glowing opal.

I cut these from a single stone that was so consistent in color I was transfixed by it. When you are grinding the shape you are lapping through the "fire" of the stone, so the final character of the stone is unknown until you get close, in the final smoothing - then the polish brings it to life.
A surprise every time.
Being a softer stone, opal is not best suited for a ring where it is subjected to abuse as opposed to a necklace, but it is beautiful on her hand.

I alloy my own gold to a favorite formula for a dark yellow 14k. Rolling out small ingots for sheet and pulling my own wire through draw plates.
These pieces are constructed, I usually cast using lost wax and investment.
I also make rubber molds for wax injecting when I wished to reproduce a design, but not much in the way of production anymore. 50 of the same pieces took the thrill away, too much like a job.
Now my bench sits and waits for my inspiration to strike.


Our Soil Moisture Active Passive (SMAP) mission will focus on soil moisture and freeze/thaw measurements. Watch a live talk at 10 p.m. EDT tonight: http://www.nasa.gov/nasatv Question? #askNASA

NEW VIDEO!! What’s the world’s DEADLIEST animal? 

(…besides humans, that is)

Biologists estimate that this animal has killed half of all humans that have ever lived, and today is responsible for more than 45 million years of lost human life annually. Chances are, you’ve been attacked by one.

Meet mankind’s most pesky foe in this week’s It’s Okay To Be Smart, and find out why they prefer some prey over others, what makes them so deadly, and how today’s bioengineers are trying to stop them… if such a thing is even possible.

Watch the video and share! What's The Deadliest Animal In The World?

My favorite material for lapidary

The picture does a poor job of conveying the color and depth.
From a distance they look like bright turquoise, but up close you see it is glowing opal.

I cut these from a single stone that was so consistent in color I was transfixed by it. When you are grinding the shape you are lapping through the "fire" of the stone, so the final character of the stone is unknown until you get close, in the final smoothing - then the polish brings it to life.
A surprise every time.
Being a softer stone, opal is not best suited for a ring where it is subjected to abuse as opposed to a necklace, but it is beautiful on her hand.

I alloy my own gold to a favorite formula for a dark yellow 14k. Rolling out small ingots for sheet and pulling my own wire through draw plates.
These pieces are constructed, I usually cast using lost wax and investment.
I also make rubber molds for wax injecting when I wished to reproduce a design, but not much in the way of production anymore. 50 of the same pieces took the thrill away, too much like a job.
Now my bench sits and waits for my inspiration to strike.


Emberglow

The original color of my '66 Mustang, newly restored this summer.
GT suspension /Iski cam /forged pistons /roller rockers / new ported heads, 2.02 valves / JBA headers / electronic ignition / new transmission / new interior / new paint.

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Ups and Downs

The Sun orbits the center of the Milky way at a speed of about 230 km/s, taking about 250 million years to go around the galaxy once. It is a period of times sometimes referred to as a galactic year. But the Sun does not move in a simple circle or ellipse as the planets move around the Sun. This is due to the fact that the mass of the galaxy is not concentrated at a single point, but is instead spread across a plane with spiral arms and such. As a result, while the Sun orbits the galaxy it also moves up and down across the galactic plane. While the Sun is above the plane, the mass of the galaxy works to move it downward, and when below the plane the mass pulls it upward.  As a result the Sun oscillates through the galaxy, crossing the galactic plane once every 30 million years or so.

There has been a great deal of speculation that this oscillatory motion could have implications for life on Earth, such as triggering cometary bombardments and causing mass extinctions. There is little evidence to support this idea, since mass extinctions don’t strongly follow a 30 million year cycle, and studies of impacts on the Moon show no correlation either. But now a new study in Scientific Reports shows what seems to be a relation between galactic motion and Earth’s temperature.

The paper looked at temperature measurements of the Phanerozoic, which is the geologic period covering the last 540 million years. It covers everything from the Cambrian up to the present, which is most of the period in which complex life has been on Earth. Specifically, they looked at what is known as delta-O-18 measurements, which is a measurement of the oxygen 18 isotope relative to oxygen 16 within calcium carbonate deposits. These deposits were made by shelled organisms. Since the evaporation of water prefers O16 over O18 due to its smaller mass, delta-O-18 provides an indicator for geologic temperatures.

The team looked at 24,000 delta-O-18 measurements covering the Phanerozoic, and looked for a correlation between O18 levels and the position of the Sun relative to the galactic plane. What they found was a correlation with a confidence of 99.9%. So it seems fairly clear that our galactic position has had an effect on geologic temperatures. What isn’t clear is what could cause such a variation. The authors suggest that the motion may result in a variation of gamma rays striking the upper atmosphere, which could lead to changes in atmospheric temperature. At this point that it still pretty speculative.

Just to be clear, this paper looked at variations over long geologic scales. The motion of the Sun through the galaxy and any resulting temperature variation has no effect on the current warming trend we observe due to rising CO2 levels. Global warming, as it is often called, is not a galactic effect.

Image: Nature/C. Carreau-ESA.

Paper: Nir J. Shaviv, et al. Is the Solar System’s Galactic Motion Imprinted in the Phanerozoic Climate? Scientific Reports 4, Article number: 6150 (2014)