Posts Tagged ‘Solar System’

Wheels within Wheels

June 1, 2015

In the previous post, I left off the history of astronomy with Claudius Ptolemy, the last and greatest of the astronomers of ancient times. It was Ptolemy who brought the science of astronomy to its apex in classical times. In his treatise, the Almagest, as the Arabs came to call it, Ptolemy worked out the geocentric model with the complex system of epicycles that the ancients believed described the universe, along with a catalog of stars and constellations and tables of information on the motions of the planets and eclipses of the Sun and Moon. So well did Ptolemy do his work that the Almagest was the accepted text on astronomy for over twelve hundred years.

The science of astronomy did not stand still after the time of Ptolemy. The Western Europeans were a little distracted by the fall of the Roman Empire in the West and contributed little to the progress of learning for some centuries. Fortunately the ancient learning was preserved in the Greek East and when the Arabs conquered much of the Middle East in the century after the death of Mohammed, they were able to learn much from the peoples they ruled and soon began to make contributions of their own in science and philosophy. The Arabs translated many Greek texts into Arabic which Western scholars discovered and translated into Latin. The contributions made by the Arabs can be seen by the fact that Ptolemy’s standard text is known by its Arabic title and that many stars still retain names derived from  Arabic

Throughout the Early Middle Ages, the Muslims translated Greek texts into Arabic and so helped to preserve them until Western scholars could translate them into Latin once things had settled down in the West. The importance of the Arabic contribution can be seen by the fact that Ptolemy’s book is known by its Arabic title, not to mention that many stars are known by names derived from Arabic; Betelgeuse, Algol, Aldebaran, Deneb, Vega, and many others.

Over time, the Arabs, and later the Europeans, developed better instruments for observing the positions of the stars and planets in the sky and to predict the motions of the planets. As their techniques improved, astronomers were able to revise and update the information on planetary motions collected by Ptolemy, and they also found that more epicycles were needed to explain and predict planetary motions. The Ptolemaic model began to seem increasingly over complicated. The last major revision of the tables of planetary motions was commissioned by King Alfonso X of Castile in the thirteenth century. Alfonso, called “the Wise” was known as a patron of many branches of learning and was himself conversant in the science of astronomy. He is supposed to have remarked that if God had consulted him during the creation, he might have suggested a simpler system than the complicated bicycles of Ptolemy. The king almost certainly did not say this, but the sentiment was shared by many who began to believe the universe shouldn’t be so complicated.

Among these was a Polish priest who lived some two hundred years after Alfonso. This priest was named Mikolaj Kopernik, better known by the Latinized version of his name, Nicolaus Copernicus. Copernicus was a true renaissance man who was learned in such diverse fields as mathematics, canon law, medicine, economics, classical languages, diplomacy, politics, and astronomy. It is in that last subject that he is remembered today. Copernicus came to realize that understanding the motions of the planets would be much easier if he simply assumed that the planets revolved around the Sun rather than the Earth.

Copernicus

Copernicus

The retrograde motions of the planets could simply be explained by their overtaking the Earth as they orbit the Sun. Copernicus seems to have developed his heliocentric theory by 1514 and spent much of the rest of his life working on his book “De revolutionibus orbium coelestium” or “On the Revolutions of the Heavenly Spheres”. Although Copernicus showed the manuscript to his friends and interested scholars, he was reluctant to actually publish his masterpiece for fear of the public ridicule such a radical theory might bring him. It was only after his friends assured him that the book would be favorably received and he was dying that Copernicus agreed to publish De revolutionibus in 1543.

De revolutionibus was favorably received by the few people who actually read it. The fact was that Copernicus’s book was so abstruse and technical that only astronomers and mathematicians could really appreciate and understand it.

It was in Latin and the script was hard to read too.

It was in Latin and the script was hard to read too.

Copernicus’s heliocentric model was not generally accepted for some time. The fact that the assumption that the Sun was at the center of the Solar System made calculating the motions of the planets less complicated did not necessarily made that assumption true and there was good reason not to believe the Earth moved. In fact, the Copernican model did not make the calculations that much less complicated. Like Aristotle and Ptolemy, Copernicus believed that the planets moved in perfect circles and his theory still required some epicycles to agree with observations. It was not until 1610 when Johannes Kepler proposed his first law of planetary motion, that the planets orbit the Sun not in circles that the need for epicycles was finally done away with. The heliocentric model then clearly provided a simpler means of understanding the motions of the planets and so was quickly adopted by most astronomers even though there was not yet clear proof that it was actually true.

Which brings us back to Galileo and the Church. In 1632, the year Galileo was tried by the Inquisition, the heliocentric model was rapidly gaining acceptance, yet from a strictly scientific viewpoint, the Church was quite correct in regarding the model with skepticism, even if it was not correct from any viewpoint to put Galileo on trial, although as I said Galileo himself was mostly to blame for his troubles. And, here I have to ask again, why was the heliocentric theory adopted a century before it could be proven beyond a reasonable doubt?

Scientists like to portray themselves cool, logical, unbiased observers interested only in the facts, that is the results of their observations and experiments. Any hypothesis, no matter how attractive, must be put aside if the observations do not agree with it. In fact, scientists are subject to the same sorts of biases as everyone else and a candid view of the history of science will show many instances when scientists have clung to a hypothesis even when the facts seem to show otherwise. This is not always a bad thing. I would even go further and state that this is often a good thing. Sometimes intuition serves as a better guide to discovering the truth than logic and sometimes finding the truth requires ignoring the facts that seem to point in a certain direction while pursuing an underlying truth.

One of the biases that has proven to be most useful in understanding the nature of the universe we live in is the idea that the universe is, as bottom, a simple place that we can understand. If things get to be overly complicated, it is usually taken as a sign we are moving in the wrong direction and should seek a simpler explanation. This is no scientific reason for believing this is the case, yet this bias has proven to be useful over and over again. Ptolemy’s epicycles became more and more complicated, so astronomers switched to the simpler heliocentric system, and were proven right. Physicists and chemists in the nineteenth century were dismayed to discover more and more chemical elements with no clear pattern, until they discovered that all these elements could be explained by the three particles, electrons, neutrons, and protons found in the atoms of every element. Physicist were then confused by the many sub atomic particles they kept discovered, until they learned that these particles were composed of a handful of still smaller particles called quarks. This is really the essence of science, to find simple patterns to explain complex phenomena and this process requires intuition and imagination as much as it requires logical thinking and careful observation. So, Galileo was right, even when he was wrong.

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The Rolling Stones

May 5, 2015

The Rolling Stones Robert A Heinlein‘s story of the great American road trip updated for the space age. Like Heinlein’s other juvenile science fiction novels written in the 1950’s, The Rolling Stones is great fun to read and teaches the lessons in self-reliance, courage and rational thinking found in all of Heinlein’s books for young adults.

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The plot of the Rolling Stones is simple enough. Castor and Pollux Stone, two fifteen year old twins who are Loonies, lunar colonists, want to buy a used space ship so they can begin a career in interplanetary trade. They ask their father, former mayor Roger Stone, for their inheritance in advance, but he outright refuses, insisting that they need to complete their education. The other members of the family, his wife Dr. Edith Stone, older daughter Meade, younger son Lowell, or Buster, and Roger’s mother Hazel Meade Stone, a founding mother of the Lunar Free State, convince him to buy a larger space ship for the use of the whole family. Soon, the Stones are on a trip to Mars and then the Asteroid Belt. They encounter some problems, but are able to resolve them with careful thinking and ingenuity. At the end, the Stones are on their way to Saturn to see the rings.

This book was published in 1952, before any human being had gone to space and even before Sputnik, yet Heinlein was amazingly accurate in his descriptions of how space travel would actually work. Heinlein was an engineer and he clearly put a lot of thought and research into writing this book, perhaps more thought than many might bother with for a story aimed at young adults. The Stones do not just push a few buttons and head for Mars. They must  go through a take off procedure much like that of real space craft. They must carefully calculate the proper course and account for the orbits of the planets in order to get to their destination.

With all of that being said, it is interesting to note where Heinlein and other science fiction writers of his time got things wrong. In general it has proven far more expensive and difficult to establish a human presence beyond low earth orbit than anyone anticipated. Space is a more hostile environment than thought and the extended period of weightlessness experienced by the Stones on their trip would probably leave them crippled by the time they reached Mars, unless they managed to provide some sort of artificial gravity, perhaps by rotating their ship. The depictions of the planets in Heinlein’s juveniles is far out of date. Neither Mars nor Venus is habitable without extensive terraforming and there are no natives, alas. What is most remarkable for an engineer like Heinlein is the inability to predict the electronic and computer revolutions. The computers in Heinlein’s juveniles are still huge, room sized contraptions and the characters use slide rules to perform calculations. I imagine that when the time comes when families are able to take trips to other planets, there will be an app to calculate trajectories.

I said that The Rolling Stones was the story of a road trip, but it is also the story of the ever expanding frontier. Heinlein’s political and social views were often described as libertarian, but perhaps a more accurate label would be frontier. On the frontier, whether in the Old West or in space, people cannot wait for a distant government to solve their problems or take care of their needs. By the time the government even learns of their problems, they may be dead. The people on the frontier must learn to take care of themselves and once they have become used to taking care of themselves, it is hard for them to accept the idea that their betters in a distant capital are more capable of solving problems that they are. The frontier creates a political climate that emphasizes equality over hierarchy and individual freedom over regimentation. It may be that many of the problems America is currently facing, not least an ever more intrusive and lawless government and a ever shrinking personal sphere of individual freedoms, is precisely because we no longer have a frontier. If this is the case than the sooner we get up into space, the better.

Political musings aside, The Rolling Stones is an enjoyable story that can appeal to youngsters of any age.

Water Before Earth

September 26, 2014

I spotted this science story in the Los Angeles Times. I don’t suppose we think very much about water. Its just there. But some astronomers suspect that much of the water we drink  has been around before the Earth was formed.

Some of the water molecules in your drinking glass were created more than 4.5 billion years ago, according to new research.

That makes them older than the Earth, older than the solar system — even older than the sun itself.

In a study published Thursday in Science, researchers say the distinct chemical signature of the water on Earth and throughout the solar system could occur only if some of that water formed before the swirling disk of dust and gas gave birth to the planets, moons, comets and asteroids.

This primordial water makes up 30% to 50% of the water on Earth, the researchers estimate.

“It’s pretty amazing that a significant fraction of water on Earth predates the sun and the solar system,” said study leader Ilse Cleeves, an astronomer at the University of Michigan.

This finding suggests that water, a key ingredient of life, may be common in young planetary systems across the universe, Cleeves and her colleagues say.

I would think that water, in some form, would be rather common throughout the universe. It is made out of hydrogen and oxygen, two of the more common elements. There is more information about how the astronomers have come to their conclusions in the article.

I do not usually try to reconcile the text of the first chapters of Genesis with the findings of modern science. That is best left to those more learned in science and theology than I am. I am simply content to read Genesis to find out who created the universe and I turn to science to learn how He did it. Still, I am occasionally struck by how the writer of Genesis seems to have a better understanding of creation than any Bronze Age shepherd has any business having. Consider the very first verses.

In the beginning God created the heavens and the earth. Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters.

And God said, “Let there be light,” and there was light. God saw that the light was good, and he separated the light from the darkness. God called the light “day,” and the darkness he called “night.” And there was evening, and there was morning—the first day. 

The first thing God created was light. The earliest event in the universe we can have any knowledge of would be the Big Bang. If you have the right instruments you can still see the light of creation. But it is the second and third days that this story reminds me of.

And God said, “Let there be a vault between the waters to separate water from water.”So God made the vault and separated the water under the vault from the water above it. And it was so. God called the vault “sky.” And there was evening, and there was morning—the second day.

And God said, “Let the water under the sky be gathered to one place, and let dry ground appear.” And it was so. 10 God called the dry ground “land,” and the gathered waters he called “seas.” And God saw that it was good.

11 Then God said, “Let the land produce vegetation: seed-bearing plants and trees on the land that bear fruit with seed in it, according to their various kinds.” And it was so. 12 The land produced vegetation: plants bearing seed according to their kinds and trees bearing fruit with seed in it according to their kinds. And God saw that it was good. 13 And there was evening, and there was morning—the third day.

God created water before the dry land. Evidently water predates the planets. Now, plants are shown to be created before the Sun and Moon. This presents a problem since plants cannot survive without the Sun. But instead of plants, think the most primitive forms of life, perhaps bacteria, or even life simpler than bacteria. Some scientists believe that life may have arisen in space and traveled throughout the universe before landing on Earth. If this panspermia hypothesis is correct, then it is possible that life might also predate the formation of the solar system. There is no evidence in favor of this hypothesis. No actual life has been detected in interstellar space, though organic molecules, such as amino acids, have been.

But this is all speculation on my part and I really should leave this to wiser minds.

Ion Propulsion

March 9, 2013

Improved designs in ion engines may be the ticket for making trips to the outer solar system quicker and more feasible both for unmanned probes and (I hope) manned spacecraft. I haven’t been keeping up with space exploration as much as I used to, so I am glad to find this article in Gizmag which explains a little about ion engines and how scientists have been making them better.

The phrase “engage the ion drive” still has the ring of a line from Star Wars, but these engines have been used in space missions for more than four decades and remain the subject of ongoing research. Ion engines have incredible fuel efficiency, but their low thrust requires very long operating times … and therein lies the rub. To date, erosion within such an engine seriously limits its operational lifetime. Now a group of researchers at NASA’s Jet Propulsion Laboratory (JPL) has developed a new design that largely eliminates this erosion, opening the gates for higher thrust and more efficient drives for manned and unmanned missions to the reaches of the Solar System.

There are many varieties and more proposals (the VASMIR engine comes to mind), but the operating principle is quite simple. There are two basic styles of ion engines, electrostatic and electromagnetic.

An electrostatic ion engine works by ionizing a fuel (often xenon or argon gas) by knocking off an electron to make a positive ion. The positive ions then diffuse into a region between two charged grids that contain an electrostatic field. This accelerates the positive ions out of the engine and away from the spacecraft, thereby generating thrust. Finally, an neutralizer sprays electrons into the exhaust plume at a rate that keeps the spacecraft electrically neutral.

An electromagnetic ion engine also works by ionizing a fuel. In this case a plasma is created that carries current between the ionizing anode and a cathode. The current in turn generates a magnetic field at right angles to the electric field, and thereby accelerates the positive ions out of the engine via the Lorentz force – basically the same effect on which railguns are based. Again a neutralizer keeps the spacecraft electrically neutral.

There are many varieties and more proposals (the VASMIR engine comes to mind), but the operating principle is quite simple. There are two basic styles of ion engines, electrostatic and electromagnetic.

 

There is a lot more in the article.

Even Scotty would be impressed by this.

Though, what we really need is warp drive. Anyone doing research on that?

 

Planet at Alpha Centauri

October 23, 2012

I have been meaning to write about the planet astronomers have discovered orbiting Alpha Centauri. I think this is quite exciting since Alpha Centauri is the nearest star, except the the Sun of course, only about four light years away. Here is some information from the International Business Times.

A planet with a mass similar to Earth has been discovered in Alpha Centauri System, just right outside our Solar System. What makes this planet stand out among hundreds of exoplanets previously discovered?

Here are 10 Things You Need to Know about Alpha Centauri and this Neighboring Planet:

10. Alpha Centauri is composed of three stars: Alpha Centauri A, Alpha Centauri B and Proxima Centauri, which is shining close to the Sun, the star at the center of the Solar System.

9. Alpha Centauri is a complicated system because its stars orbit one another. Further studies were made to confirm whether the orbiting body is indeed a planet.

8. Alpha Centauri is only 4.3 light years away from Earth.

7. The recently discovered unnamed planet in the Alpha Centauri System has the same mass as Earth. It is the nearest planet to Earth compared to other planets – 840 so far – discovered in the past.

6. In contrast to Mercury’s distance to the sun during orbit, the newly-discovered planet is closer to the star it orbits, suggesting extreme temperature on the surface — about 1,500C, according to scientists.

5. The neighbor planet was found near Alpha Centauri B, six million kilometers away.

4. The Harps instrument spotted the planet from the European Southern Observatory’s La Silla facility in Chile.

3. Four years of observation revealed the planet orbits Alpha Centauri B in just 3.2 to 3.6 days, a far contrast to earth’s 365 days.

2. Normally, more planets are discovered once a planet and its star have been properly identified. “The prospects are excellent for finding further planets in this system. Everything we know indicates that when you find one planet like this you’re very likely to find additional planets further out, so it’s very exciting in terms of looking forward to further detection,” Greg Laughlin of the University of California at Santa Cruz told The Guardian.

1. The Alpha Centauri planet discovery is ordinary-but-promising in space exploration. “Even if the discovery just stands perfectly normal in the discoveries we have had up to now, it’s a landmark discovery, because it’s very low-mass and it’s our closest neighbor,” Stéphane Udry of Switzerland’s Geneva Observatory told BBC.

With a surface temperature of 1500 degrees Celsius, we won’t be colonizing that planet any time soon, and of course, with our present technology, it would still take thousands of years to get there. Well, if they ever invent warp drive, that that will be our first stop.

 


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