Why do stars twinkle while the light from planets looks steady?  The first part of the question is easier to answer than the second. Here’s a hint – the stars do not twinkle when viewed from the space station or from anywhere above the earth’s atmosphere. You guessed it: the twinkle is caused by turbulence in the air as the light beam passes through.

Then why do not planets also twinkle? As an example, if you look at Jupiter (in the western sky in the early months of 2011 after sunset) and compare it to a bright star, like Sirius which is the brightest object high in the eastern sky at the same time, you can tell that Sirius has a beautiful sparkling, wavering appearance that you do not see with Jupiter.

One way to explain this is that Jupiter’s diameter is very large in our view compared to Sirius (in a telescope, you can see that Jupiter is a round ball with surface features, while Sirius stays as a single point of light – even in the most powerful earth-based telescopes). Because of the size of the planet, there are many paths of light between the planet and us on earth. So even though each path of light is wavering because of the atmosphere, the average between all the paths to reach the eye looks steady. The eye blends them together into a sight that looks unwavering; therefore a planet doesn’t appear to twinkle.

But, you might point out, surely Sirius, the brightest star in our night sky, is much, much larger than Jupiter. In fact, its diameter, estimated to be 90 billion miles is more than a million times Jupiter’s diameter of 83 thousand miles.  One the other hand, because Jupiter is so much closer, the apparent diameter (as it looks to an earth based observer) of Jupiter is about 8000 times that of SIrius.

This, in turn, means that the apparent size in area of Jupiter is about 64 million times as big. So if we think of Sirius as having only one path of light hitting our eye, then Jupiter would have about 64 million paths to send its light rays to our eye. And the result is an averaging of all those paths to our eye to give the appearance of a steady light from the planet.  In other words, the wavering is smoothed out.

Whew! That’s a lot of words to explain a simple idea, but I hope it helps you understand what is happening when you see the steady light of  Venus, Mars, Jupiter, or Saturn  compared to the surrounding stars. Note: you rarely see Mercury since it stays very close to the Sun, and the other planets, Uranus, Neptune, and Pluto are too faint to be seen easily.

The other lesson learned here is how very far away are even the nearest stars  (Sirius is in the family of  about a dozen nearest stars – those that are less than 10 light years away.   The closest, Proxima Centauri, is about 4 light years away). Most of space is empty of stars and planets.

The universe unimaginably immense, and yet our God who is its creator and sustainer is much greater.   The bible says that it was created through Jesus Christ, and that is sustained by the word of His power. (Hebrews 1:1-3)  God is incomprehensively powerful. majestic, and glorious, and yet He loves each one of His creatures.  Our names are written on His hand (Isaiah 49:16). Do you know that He loves you and me with His whole heart?

Then I will swish it around in the pan with the water, hoping it will attract iron particles strong enough so that when I remove the wrapped plastic from the water, those particles will adhere to the surface.

I will next, place the wrapped magnet into a shallow plate of water, carefully unfold the plastic wrap so I can lift the magnet away, and leave the particles, if any, behind in the plate.  Then I will remove the plastic wrap off of the water surface, hoping that the particles will fall off into the water.

[added later:]  Finally, I will place the plate of water under a clip-on light as a heat source to evaporate the water.  Using some “sticky notes” I will collect the particles left on the plate and examine them under a microscope.

I will let you know if this technique works.  I got the idea from one of the references in my original article.

[ Note:  the results were "null" - see my last comment below.]

P.S. We are busy getting our house ready to sell and find a new home in Richmond, VA.  So my writing has dwindled considerably.  I hope it will become regular again after this huge adjustment in life.  :-)

Boyd

If you have studied the problems of keeping a satellite in orbit around the earth, you know that there have to be periodic adjustments made to its speed and direction. Otherwise the orbit will degrade so that a satellite can no longer perform its function. The adjustments are usually made by commanding small jets to eject a precise amount of compressed gas that is stored on the satellite. The ground controllers call these adjustments “burns.”

And this problem is prevalent no matter where you would try to place a space object in the solar system except at some very special points in space called Lagrangian Points. They are labeled L1, L2, … L5. There are 5 L points for each pair of orbiting bodies, like the Sun-Earth system and the Sun-Mars system as well as for the Earth-Moon pair of bodies, as seen in the diagram that is in the Wikipedia: Lagrangian Point article.

Lagrange points for Earth-Moon

The two points, L4 and L5, are the best choices for a stable location because if the satellite drifts away from the point in any direction, the effects of gravity plus momentum will keep it close to the Lagrangian point. The blue arrows show the limits of the “safe region”.

On the other hand, L1, L2, and L3 only have temporary stability and a satellite at those positions has to have periodic adjustments to keep it there. Drifting any amount toward or away from the earth or moon will produce instability. Thus, though it takes less “fuel” to keep a satellite at those points, the “burns” are still required.

I just chatted on-line with my friend Chandra in India – he worked on a version of this problem in college. It was called the 3-body problem discussed by Newton in 1687 and by Euler in 1767, and then by Lagrange in 1772.( ref: Wikipedia article: Three-body_problem)

For only 2 bodies in space, the prediction of their orbits around each other is easily calculated. But add a 3rd body and their orbits become unpredictable except in restricted circumstances. Outside those restrictions, the motion is chaotic – in fact, the academic field of Chaos was established to deal with this kind of motion.

I find it amazing that our Lord Jesus, who was the one through whom the universe was created (Hebrews 1:2), is also the one that made the laws by which it behaves. He knows all about the chaos that it is all heading for, and provides for us a safe, stable resting place in Him.

Take my yoke upon you and learn of me; for I am meek and lowly in heart: and ye shall find rest unto your souls.
For my yoke is easy, and my burden is light.
(Matthew 6:29-30)

Since that time, I have probably attempted more than 10 times to find a magnetic micrometeorite in snow, rain, and dust, to no avail. [Actually, I just re-read the previous article and remember I did find one potential particle which I accidentally lost in the search.]

I have looked at 1000′s of potential particles under a microscope with a strong magnet moving under the slide in close proximity, and have yet seen one such micrometeorite. There have been 2-3 flat looking magnetic particles which I imagine came from industrial polution, but they did not at all look like photographs of micrometeorites.

On the other hand, I have found probably 100 non-magnetic particles that look like photographs of the micrometeorites – they are black, rounded, and shiny, and in the average diameter I would say was about 1/10 mm.

So, I am wanting to know if others have had better luck in finding them, and what techniques did they use? I am suspicious that some of the “how to’s” I have read were not performed by the writers of those documents.

If you have a reference or an experience to share with me, please respond below or write e-mail to BrightMysteries@verizon.net

Thank you very much.

Boyd

David and his bridge that underwent destructive testing in high school

The owl will nest there and lay eggs, she will hatch them, and care for her young under the shadow of her wings. (Isaiah 34:15)

Periodically our son and grandson come to search the stuff stored in our attic for toys and memories.  This past visit, they found a balsa-wood model bridge that my son had built in high school for a classroom contest.  I had suggested that the catenary shape might be the strongest shape to use for the weight-bearing parts of the bridge.  I left the rest to him.

During the contest, the bridges were subjected to increasing weight until they broke and dropped the weight.  He recalls that his bridge came in second, but in a way, was the best one because his design used the least amount of  balsa wood – it was light weight but very strong.

What is the catenary shape?  It is the shape of the St. Louis Arch and of many ancient and modern arches used in architecture;  the shape is most easily achieved by hanging a chain by its two ends. The natural shape it takes between the attachment points is the catenary shape.  It is also very close to the shape of the ends of an egg.

While teaching physics, my students showed how strong this shape is.  In a simple demonstration two students held a bed sheet between them to act as a catching net.  A raw egg (the free-roaming chicken, barnyard eggs are best for this) is thrown hard into the sheet by another student, and, unless the sheet is missed, the egg will not break.  At least I never saw it break from hitting the sheet, assuming the catchers did not let it roll off onto the ground.

The other impressive demonstration requires two straight-sided glass cylinders, such as drinking glasses, where one glass will fit closely inside the other.  The egg (raw)  is padded below and above with a sponge or folded paper towels, for example, and placed in the larger glass.

Important!  The egg is placed so the long axis of the egg is parallel to the sides of the glass; in other words, the egg is placed “on end” in the glass. The bottom of the inner glass is then slid into the outer glass until it is resting on top of the padded egg.

Using a chair to steady the person, and standing on a stool about the same height as the nested glasses, he or she gradually places all of his or her weight on the upper glass showing that the egg will support the weight without crushing.  Of course, there is a limit of how much it will support.  When I last did it, I probably weighed about 200 lbs, and did not break the egg.

Isn’t it amazing, that the law of gravity, as established by the creator, is what causes a chain to hang as it does, that this same shape is that of the eggs laid by various birds and reptiles, and that it forms the strongest type of free-standing arch?  Isaiah 34:15 says, “The owl will nest there and lay eggs, she will hatch them, and care for her young under the shadow of her wings.” God loves us and also invites us to abide in His strong shelter.

In the early days of science,  it was believed that there was no connection between electricity and magnetism.  The magnetic force was found in rocks with iron ore in them, and then magnets were made by rubbing these special rocks against iron or steel.  These were then used to make magnetic compasses, giving a wonderful advancement in navigation.

The early experiments with electricity included the investigation of lightning, made most famous with Benjamin Franklin’s dangerous flying of a kite during a thunderstorm (he and his assistant could have been easily killed by a direct hit).   It was also discovered that heat and light could be produced by passing the current from a battery through a thin wire.

However, to show there was no connection between electricity and magnetism, a magnetic compass was placed beneath a wire through which electric current was passed. The equipment was arranged so that the wire was at right angles to the compass needle, thinking that surely if there were a force between them, the needle would be deflected to become parallel to the wire.  But there was no deflection.

However, in 1820, Hans Oersted at the University of Copenhagen while preparing this demonstration, discovered that if the compass needle and the wire are parallel to start with, that the needle would swing to being perpendicular to the wire – just the opposite of that which had been predicted.  It was a serendipitous moment.  He had shown a connection between electricity and magnetism.

This led to the building of an electric catapult, hence the nickname given this force, which today is called the Lorentz Force, named after Hendrik Lorentz who formulated the mathematical equation in 1892 that describes it.

To picture the catapult, imagine a child’s swing scaled down to fit on top of a table.  You would use thin wires instead of chains to hold up the “seat” which is also made of wire. Everything would be connected to a battery so that electric current will flow down one “chain”, through the “seat”, and back up the other “chain.”

Directly below the “seat” you would hold a bar magnet with the north pole pointing upward. When the current was turned on through the “swing,”  the “seat” would be “catapulted” forward or backward, depending on the direction of the current.

You may have seen toys that swing back and forth tirelessly, run by a single AA battery that is based on this principle.  In fact the electrically powered baby swings operate by this catapult force. More importantly this Lorentz Force is what powers electric motors which have played such a large role in the twentieth and twenty-first centuries.

Proverbs says, “It is the glory of God to conceal a matter;  to search out a matter is the glory of kings” (Proverbs 25:2)  It is such a blessing that He also puts in our hearts and minds the desire to discover these hidden laws of His creation.

On our trip to the YMCA today, I asked my grandson why the sky is blue. He said, “Maybe it’s because of the water in the atmosphere.” I replied, “Well that could be part of the reason, but then why is the sky red around the sun at sunset?” He puzzled over that. After a little pause, I gave an explanation and his questions about it helped me clarify the description.

Light, as we described in some articles last year, is made up of small energy bundles called photons. There are red, green, blue photons, and all the other pure colors as well. And sunlight has a mixture of all these colored photons, giving an average to our eyes of white light, or at least it is white in outer space. But our atmosphere affects it in interesting ways.

As the collection of photons of white light passes through the air, the blue photons have about 10 times more chance of being scattered (bouncing off air molecules) than do the red photons. (Today in my research for writing this I found out that Einstein explained this scattering phenomena in 1911 – his contribution to science is amazing, isn’t it?)

Thus the red photons are more likely to pass through the air unimpeded while more of the blue ones bounce off in all directions. Thus when looking at the sky away from the sun, a person will see a mixture of light with more blue photons than red ones, and hence it looks blue – sometimes very blue depending on the sun’s position and the clearness of the air.

On the other hand, as people enjoy a sunrise or sunset, they are looking at the light passing through much more air than when the sun is overhead, so the effect of the blue photons being scattered out is greater, and hence, the direct light from the sun to their eyes or reflecting off the clouds looks red to them.

Why does the moon look larger on the horizon? In fact, it is not larger but is the so-called moon illusion. In fact the width of the moon is exactly the same as it is when it is overhead. On the other hand, the height of the moon on the horizon is actually a little reduced than when overhead, caused by the distortion of the light rays passing through the thicker atmosphere.

There are various theories for the cause of this illusion. The one I like best is that when the moon is near the horizon, our visual system is comparing it to the surrounding scenery, and knowing it is much further away, it seems larger. One article says to “trick your mind out of the moon illusion is to bend over at the waist and look at the moon upside down through your legs” (http://www.howstuffworks.com/question941.htm).

Both of the processes involve producing final products that are more stable than the initial ingredients. Fission happens when a heavy nucleus breaks up into two or more lighter nuclei, releasing lots of energy, because the lighter nuclei are more stable. Fusion goes the other way. Two very light nuclei are combined to give a heavier, more stable nucleus, releasing even more energy per gram, because the difference in stability between the “parents” and the “child” is even greater.

The most stable nuclei have 50-60 neutrons plus protons in them (iron and nickle, are typical in this range). So the final product at the end of the life of a star, for example, is a large chunk of this material. The lighter elements (nuclei) have fused together into these medium-heavy nuclei.

For comparison, nuclear fission starts with very heavy nuclei, Uranium, for example, with 238 neutrons and protons, and splits up into products frequently in this same range of medium-heavy nuclei.

So, to review, a star spends something like 99% of its life converting Hydrogen into Helium in the fusion process, then it changes character, spending the rest of its life (much shorter time scale) combining Helium into heavier nuclei, and those products into heavier ones still, until the stability maximum is reached, then it “dies”.

Since fusion is more efficient than fission, then why haven’t fusion reactors been made successfully for man’s use? The answer is, because it is very difficult to get the Hydrogen nuclei close enough to combine. They naturally repel each other because the protons are positively charged (remember, like charges repel).

Because a star is so massive, the strong gravitational force overcomes the repulsion between like charges, forcing them close enough to fuse. This kind of force has been very difficult to produce in the laboratories on earth. Only in the Hydrogen bomb has fusion been consistently possible. The atomic bomb is a fission process.

So that is a brief account of how a star “burns”. Another article will talk about the sequence of the life of a star including the time scale involved.

What are these stellar objects?  Well, astronomers think they all started out as regular stars and these are the results of their”deaths”.  But these are theories that may or may not be true.  (I think they are true, but I can’t prove them).

As in most all things created, we cannot do experiments in the present to see what really happened in the past. The best we can do is make up theories that seem to explain the evidence, and then compare other evidence as it is found against the theories.

So here is a brief summary of the theories as I understand them.

Red Giants = stars that are nearing death.  They have used up all the Hydrogen in the core, in the fusion process from Hydrogen to heavier elements, and there is a outer shell of hydrogen which continues the fusion process, but expands the diameter of the star greatly – typically 200 times its original size.  (Our sun would grow large enough to engulf the earth, it is predicted).

White Dwarfs = The white hot core of the star after it has “died” and blown off the outer shells.  It takes millions of years to finally cool off and become a cold, black dwarf, and no longer visible.

Black Holes = Many types, but one type is a star that had so much mass at the end of its life, that it collapsed under its own gravity to such a size where the density was so great that not even light could escape.  And this is the one I want to talk about more because a lot of the physics needs explaining.

The history line says “The original Galaxy Zoo was launched in July 2007, with a data set made up of a million galaxies imaged with the robotic telescope of the Sloan Digital Sky Survey. With so many galaxies, the team thought that it might take at least two years for visitors to the site to work through them all. Within 24 hours of launch, the site was receiving 70,000 classifications an hour, and more than 50 million classifications were received by the project during its first year, from almost 150,000 people.”

I just joined and hope to spend some time contributing. Anyone can do it. A tutorial is included. And your classification is checked against other observers to help prevent mistakes.