Astronomy

Is Earth the most inclined or not?

Is Earth the most inclined or not?


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I'm trying to understand orbital inclination by looking at the planetary orbit inclination table on https://en.wikipedia.org/wiki/Orbital_inclination (there are orbital inclinations for terrestrial and gas giant planets listed there).

By inclinations to ecliptic or Sun's equator, it looks like the Earth is the most (or least) inclined from all the listed objects having the smallest (or biggest) inclination value. However, the inclination to invariable plane seems to be bigger for some planets than for the Earth, and smaller for others.

At first, I thought that displaying the absolute value (dropping the minus sign) in case of a negative angle is the case. But if those three columns were just three different reference planes, the relative difference between planet inclinations should at least be the same in all cases. But it's not the case as, for example, Mercury's and Venus' orbital planes have 3.62° between themselves as per the inclination to ecliptic, but they have 0.48° as per the inclination to the Sun's equator.

So, how should one read those numbers?


The confusing thing is that inclination is not the only thing defining an orbital plane; it also matters where the ascending node is. Only if all ascending nodes would be in the same direction, you could do the trick with the absolute values you mentioned.

I can't draw a picture right now, but imagine you have a table before you now, and use it as a reference plane (the Sun's equator). Put a sheet of paper on the table, and lift the right end a bit so that it inclines 7.155° w.r.t. the table. This is Earth's orbit, and it looks a bit like the picture in the Wikipedia article.

Now take another sheet of paper, and lift the far end a bit so that it inclines 7.155° w.r.t. the table. This is supposed to be the orbital plane of a hypothetical planet with the same inclination to the Sun's equator, but it is also inclined to the ecliptic (i.e. Earth's orbital plane).


Earth Science is the study of the Earth and its neighbors in space. It is an exciting science with many interesting and practical applications. Some Earth scientists use their knowledge of the Earth to locate and develop energy and mineral resources. Others study the impact of human activity on Earth's environment, and design methods to protect the planet. Some use their knowledge about Earth processes such as volcanoes, earthquakes, and hurricanes to plan communities that will not expose people to these dangerous events.

Many different sciences are used to learn about the Earth however, the four basic areas of Earth science study are: geology, meteorology, oceanography, and astronomy. A brief explanation of these sciences is provided below.

Earth Scientists Study the Subsurface

Mapping the inside of a volcano: Dr. Catherine Snelson, Assistant Professor of Geophysics at New Mexico Tech, sets off small explosions on the flank of Mount Erebus (a volcano in Antarctica). Vibrations from the explosions travel into the Earth and reflect off of structures below. Her instruments record the vibrations. She uses the data to prepare maps of the volcano's interior. Photo courtesy of Martin Reed, the National Science Foundation and the United States Antarctic Program. Learn more about what Dr. Snelson and others are doing to learn about Mount Erebus.

Geology: Science of the Earth

Geology is the primary Earth science. The word means "study of the Earth." Geology deals with the composition of Earth materials, Earth structures, and Earth processes. It is also concerned with the organisms of the planet and how the planet has changed over time. Geologists search for fuels and minerals, study natural hazards, and work to protect Earth's environment.

Earth Scientists Map the Surface

Mapping lava flows: Charlie Bacon, a USGS volcanologist, draws the boundaries of prehistoric lava flows from Mount Veniaminof, Alaska, onto a map. This map will show the areas covered by past lava eruptions and can be used to estimate the potential impact of future eruptions. Scientists in Alaska often carry firearms (foreground) and pepper spray as protection against grizzly bears. The backpack contains food and survival gear, and a two-way radio to call his helicopter pilot. Charlie's orange overalls help the pilot find him on pick-up day. Image by Charlie Bacon, USGS / Alaska Volcano Observatory.

Meteorology: Science of the Atmosphere

Meteorology is the study of the atmosphere and how processes in the atmosphere determine Earth's weather and climate. Meteorology is a very practical science because everyone is concerned about the weather. How climate changes over time in response to the actions of people is a topic of urgent worldwide concern. The study of meteorology is of critical importance in protecting Earth's environment.

The Hydrologic Cycle - An Earth Science System

Hydrologic Cycle: Earth Science involves the study of systems such as the hydrologic cycle. This type of system can only be understood by using a knowledge of geology (groundwater), meteorology (weather and climate), oceanography (ocean systems) and astronomy (energy input from the sun). The hydrologic cycle is always in balance - inputs and withdrawals must be equal. Earth scientists would determine the impact of any human input or withdraw from the system. NOAA image created by Peter Corrigan.

Oceanography: Science of the Oceans

Oceanography is the study of Earth's oceans - their composition, movement, organisms and processes. The oceans cover most of our planet and are important resources for food and other commodities. They are increasingly being used as an energy source. The oceans also have a major influence on the weather, and changes in the oceans can drive or moderate climate change. Oceanographers work to develop the ocean as a resource and protect it from human impact. The goal is to utilize the oceans while minimizing the effects of our actions.

Astronomy: Science of the Universe

Astronomy is the study of the universe. Here are some examples of why studying space beyond Earth is important: the moon drives the ocean's tidal system, asteroid impacts have repeatedly devastated Earth's inhabitants, and energy from the sun drives our weather and climates. A knowledge of astronomy is essential to understanding the Earth. Astronomers can also use a knowledge of Earth materials, processes and history to understand other planets - even those outside of our own solar system.


Book excerpt: "Extraterrestrial: The First Sign of Intelligent Life Beyond Earth"

Avi Loeb's new book, "Extraterrestrial: The First Sign of Intelligent Life Beyond Earth" (Houghton Mifflin Harcourt), examines evidence of an object of interstellar origin that the Harvard astronomer suggests was manufactured.

Read an excerpt from the book's introduction below &ndash and don't miss David Pogue's interview with Avi Loeb on "CBS Sunday Morning" May 16!

Houghton Mifflin Harcourt

When you get a chance, step outside, admire the universe. This is best done at night, of course. But even when the only celestial object we can make out is the noontime Sun, the universe is always there, awaiting our attention. Just looking up, I find, helps change your perspective.

The view over our heads is most majestic at nighttime, but this is not a quality of the universe rather, it is a quality of humankind. In the welter of daytime concerns, most of us spend a majority of our hours attentive to what is a few feet or yards in front of us when we think of what is above us, most often it's because we're concerned about the weather. But at night, our terrestrial worries tend to ebb, and the grandeur of the moon, the stars, the Milky Way, and &mdash for the fortunate among us &mdash the trail of a passing comet or satellite become visible to backyard telescopes and even the naked eye.

What we see when we bother to look up has inspired humanity for as far back as recorded history. Indeed, it has recently been surmised that forty-thousand-year-old cave paintings throughout Europe show that our distant ancestors tracked the stars. From poets to philosophers, theologians to scientists, we have found in the universe provocations for awe, action, and the advancement of civilization. It was the nascent field of astronomy, after all, that was the impetus for the scientific revolution of Nicolaus Copernicus, Galileo Galilei, and Isaac Newton that removed the Earth from the center of the physical universe. These scientists were not the first to advocate for a more self-deprecating view of our world, but unlike the philosophers and theologians who preceded them, they relied on a method of evidence-backed hypotheses that ever since has been the touchstone of human civilization's advancement.

Space & Astronomy

I have spent most of my professional career being rigorously curious about the universe. Directly or indirectly, everything beyond the Earth's atmosphere falls within the scope of my day job. At the time of this writing, I serve as chair of Harvard University's Department of Astronomy, founding director of Harvard's Black Hole Initiative, director of the Institute for Theory and Computation within the Harvard-Smithsonian Center for Astrophysics, chair of the Breakthrough Starshot Initiative, chair of the Board on Physics and Astronomy of the National Academies, a member of the advisory board for the digital platform Einstein: Visualize the Impossible from the Hebrew University of Jerusalem, and a member of the President's Council of Advisors on Science and Technology in Washington, DC. It is my good fortune to work alongside many exceptionally talented scholars and students as we consider some of the universe's most profound questions.

This book confronts one of these profound questions, arguably the most consequential: Are we alone? Over time, this question has been framed in different ways. Is life here on Earth the only life in the universe? Are humans the only sentient intelligence in the vastness of space and time? A better, more precise framing of the question would be this: Throughout the expanse of space and over the lifetime of the universe, are there now or have there ever been other sentient civilizations that, like ours, explored the stars and left evidence of their efforts?

I believe that in 2017, evidence passed through our solar system that supports the hypothesis that the answer to the last question is yes. In this book, I look at that evidence, test that hypothesis, and ask what consequences might follow if scientists gave it the same credence they give to conjectures about supersymmetry, extra dimensions, the nature of dark matter, and the possibility of a multiverse.

But this book also asks another question, in some ways a more difficult one. Are we, both scientists and laypeople, ready? Is human civilization ready to confront what follows our accepting the plausible conclusion, arrived at through evidence-backed hypotheses, that terrestrial life isn't unique and perhaps not even particularly impressive? I fear the answer is no, and that prevailing prejudice is a cause for concern.

As is true for many professions, fashionable trends and conservatism when confronting the unfamiliar are evident throughout the scientific community. Some of that conservatism stems from a laudable instinct. The scientific method encourages reasonable caution. We make a hypothesis, gather evidence, test that hypothesis against the available evidence, and then refine the hypothesis or gather more evidence. But fashions can discourage the consideration of certain hypotheses, and careerism can direct attention and resources toward some subjects and away from others.

Popular culture hasn't helped. Science fiction books and films frequently depict extraterrestrial intelligence in a way that most serious scientists find laughable. Aliens lay waste to Earth's cities, snatch human bodies, or, through torturously oblique means, endeavor to communicate with us. Whether they are malevolent or benevolent, aliens often possess superhuman wisdom and have mastered physics in ways that permit them to manipulate time and space so they can crisscross the universe &mdash sometimes even a multiverse &mdash in a blink. With this technology, they frequent solar systems, planets, and even neighborhood bars that teem with sentient life. Over the years, I have come to believe that the laws of physics cease to apply in only two places: singularities and Hollywood.

Personally, I do not enjoy science fiction when it violates the laws of physics I like science and I like fiction but only when they are honest, without pretensions. Professionally, I worry that sensationalized depictions of aliens have led to a popular and scientific culture in which it is acceptable to laugh off many serious discussions of alien life even when the evidence clearly indicates that this is a topic worthy of discussion indeed, one that we ought to be discussing now more than ever.

Are we the only intelligent life in the universe? Science fiction narratives have prepared us to expect that the answer is no and that it will arrive with a bang scientific narratives tend to avoid the question entirely. The result is that humans are woefully ill prepared for an encounter with an extraterrestrial counterpart. After the credits roll and we leave the movie theater and look up at the night sky, the contrast is jarring. Above us we see mostly empty, seemingly lifeless space. But appearances can be deceiving, and for our own good, we cannot allow ourselves to be deceived any longer. &hellip

Most of the evidence this book wrestles with was collected over eleven days, starting on October 19, 2017. That was the length of time we had to observe the first known interstellar visitor. Analysis of this data in combination with additional observations establishes our inferences about this peculiar object. Eleven days doesn't sound like much, and there isn't a scientist who doesn't wish we had managed to collect more evidence, but the data we have is substantial and from it we can infer many things, all of which I detail in the pages of this book. But one inference is agreed to by everyone who has studied the data: this visitor, when compared to every other object that astronomers have ever studied, was exotic. And the hypotheses offered up to account for all of the object's observed peculiarities are likewise exotic.

I submit that the simplest explanation for these peculiarities is that the object was created by an intelligent civilization not of this Earth.

Pictured: Trajectory of object (named `Oumuamua) through the Solar System. Unlike all asteroids or comets observed before, this orbit is not bound by the Sun's gravity. `Oumuamua originated from interstellar space and will return there with a velocity boost as a result of its passage near the Sun. Its hyperbolic orbit was inclined relative to the ecliptic plane of the Solar System and did not pass close to any of the planets on the way in. ESO/K. Meech et al., from "Extraterrestrial"

This is a hypothesis, of course &mdash but it is a thoroughly scientific one. The conclusions we can draw from it, however, are not solely scientific, nor are the actions we might take in light of those conclusions. That is because my simple hypothesis opens out to some of the most profound questions humankind has ever sought to answer, questions that have been viewed through the lens of religion, philosophy, and the scientific method. They touch on everything of any importance to human civilization and life, any life, in the universe.

In the spirit of transparency, know that some scientists find my hypothesis unfashionable, outside of mainstream science, even dangerously ill conceived. But the most egregious error we can make, I believe, is not to take this possibility seriously enough. .


Excerpted from "Extraterrestrial: The First Sign of Intelligent Life Beyond Earth" by Avi Loeb. Copyright 2021 by Avi Loeb. Used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.


Astronomy Test 2

About a trillion comets are thought to be located far, far beyond Pluto in the ____________
The bright spherical part of a comet observed when it is close to the Sun is the ____________
A comet's plasma ____________ directly away from the Sun.
A comet's ____________ the frozen portion of a comet.
Particles ejected from a comet can cause a(n) _____________ on Earth.
The _____________ extends from about beyond the orbit of Neptune to about twice the distance of Neptune from the Sun.

Europa
surface features provide evidence of a subsurface liquid ocean
ice covered surface with few impact craters

The largest moon in the solar system is ______________.
The jovian moon with the most geologically active surface is ______________.
Strong evidence both from surface features and magnetic field data support the existence of a subsurface ocean on _________________.
______________ is responsible for the tremendous volcanic activity on Io.
_____________ is the most distant of Jupiter's four Galilean moons.
The fact that Europa orbits Jupiter twice for every one orbit of Ganymede is an example of a(n) _______________.


Is Earth the most inclined or not? - Astronomy


Zetetic Astronomy , by 'Parallax' (pseud. Samuel Birley Rowbotham), [1881], at sacred-texts.com

PRECESSION OF THE EQUINOXES.

THE Copernican or Newtonian theory of astronomy requires that the "axis of the earth is inclined 23° 28´ to that of the ecliptic."

"And from observation it is found that the sun does not every year cut the equator in the same point. If on a certain day he cuts the equator at a certain point, on the same day in the next year he cuts it at another point situated 50″.103 west of the former, and thus arrives at the equinox 20´ 23″ before having completed his revolution in the heavens, or passed from one fixed star to another. Thus the tropical year, or the true year of the seasons, is shorter than the sidereal year. . . . Retrograding every year 50″.103 to the west, the equinoxes

make a complete revolution in 25,868 years. Thus the first point of Aries which formerly corresponded to the vernal equinox, is now 30° more to the west, though by a convention amongst astronomers it always answers to the equinox. . . . This change in the obliquity of the equator to the ecliptic is confirmed by the observations of ancient astronomers, and by calculation. We can convince ourselves of it by comparing the actual situation of the stars with respect to the ecliptic to that which they occupied in the earliest times. Thus we find that those which, according to the testimony of the ancients, were situated north of the ecliptic, near the summer solstice, are now more advanced towards the north, and have receded from this plane that those which were south of the ecliptic, near the summer solstice, have approached this plane and that some have passed into it, and even beyond it, on their course northward. The contrary changes take place near the winter solstice." 1

That the sun does not "cut the equator" every year in the same point, and that "the stars which were, in earliest times, situated north of the summer solstice, are now, in relation to the sun's position, more advanced towards the north," cannot be doubted but because the earth is not a globe, and neither rotates on axes nor moves in an orbit round the sun, these changes cannot be attributed to what has been called the "precession of the equinoxes, It has been found, as stated at page 105-9 of this work, that the path of the sun is always over the earth, and concentric with the northern centre, and that the distance of the annual path has been gradually increasing ever since observations have been made--more than a quarter of a

century. And when we consider that in Great Britain, and countries still more to the north, evidences have been found of a more tropical condition having once existed, we are forced to the conclusion that this gradual enlargement of the sun's course has been going on for centuries and that at a former period the northern centre, and places such as Greenland, Iceland, Siberia, &c., at no great distance from it, have been tropical regions.

"People have dug down in the earth in Scotland, and in Canada--colder still--nay, even on the icy shores of Baffin's Bay and on Melville Island, the most northern region of the earth that has ever been reached by man, there have been found--what? magnificent buried forests, and gigantic trees, which could only live now in the warmest countries of our earth--palm trees, and immense ferns, which, in our day, have scarcely light and heat enough to grow, even in the torrid zone." 1

"It is well known, as a matter of history, that when Green-land was discovered, it possessed a much warmer climate than it does at present. The ice packs have been extending south from the polar regions for some centuries. The cause of this is not well understood, the fact only is known." 2

As a natural result of the same enlargement of the sun's path, the south must have been gradually changing--its frost and darkness diminishing and many have declared that such is really the fact.

"This climate appears to be in general much more temperate now (1822) than it was forty years ago. . . . Immense bodies of ice were then annually found in the latitude of 50° S.

[paragraph continues] During the three voyages which I have made in these seas, I have never seen southern ice drifting to the northward of South Georgia (54° S.) Great changes must therefore have taken place in the south polar ice." 1

When comparing the accounts of voyages, both to the north and south, made by the earliest navigators, with the statements made by those of recent periods, many incidental proofs are found of the increase of cold in the arctic regions, and corresponding decrease in the antarctic. Hence we find that the various changes which have been attributed to the "procession of the equinoxes," are really due to the sun's gradually increasing distance from the northern centre, and his advance towards the south. How long the sun's path has been moving southwards, or how near it was to the polar centre when the advance commenced, or whether it was once vertical there, are questions which cannot yet be answered. If ever the sun had a vertical position over the northern centre there could not, of course, be alternations of heat and cold, or day and night, but one perpetual day and tropical summer. It is evident then that ever since day and night commenced, the sun must have moved in a concentric path at some distance from the polar centre but because the path was much nearer than it is at the present day, the whole of the northern region must have been tropical, with long days, and scarcely darkness during the nights but long continued day, gently gliding into evening or twilight, and summer alternating with spring and autumn, but never with darkness and winter. Hence,

with so much day and so little night, such gentle alternations of temperature, and the sun-light almost continually playing at a considerable altitude, this region must have teemed with animal and vegetable life of the most beautiful character. Everything must have been developed with the most perfect structure, the most brilliant colours, the greatest physical powers, and the most intense moral and mental capacities. Such a region could not be less than a paradise, as beautiful and perfect as any ever recorded in the sacred books of ancient theologists, or of which it is possible for the human mind even now to conceive. There are frequent and singular references to be found in the sacred books, legends, and poems, of various nations, to the north as having been the abode of happy, powerful, and highly intelligent beings.


The surface of the Earth is not, rigorously speaking, an inertial frame of reference. Objects at rest relative to Earth's surface are actually subject to a series of inertial effects, like the ficticious forces (Coriolis, centrifugal etc.) because of Earth's rotation, precession and other kinds of acceleration.

When solving physics problems, however, we usually take the Earth frame as being inertial. This is because the inertial effects are minuscule for most of our day-to-day experiences and experiments. For example, objects in the Equator are the ones subject to the strongest centrifugal force and it is only about $3 imes10^<-3>$ or .3\%$ of their weight.

So for the most part, if an experiment is short enough and happens in a small enough region, the surface of Earth can indeed be approximated to an inertial frame of reference since the effects on the experiment's results are very, very tiny.

This of course has exceptions, as cited in njspeer's answer.

If however by "Earth" you mean the reference frame in Earth's center, it is an inertial frame according to General Relativity (GR), since observers in free fall are inertial in GR. The Earth actually does have some proper acceleration due to external forces such as radiation pressure, but these are also minuscule effects.


Do you like Earth’s solid surface and life-inclined climate? Thank your lucky (massive) star

ANN ARBOR—Earth's solid surface and moderate climate may be due, in part, to a massive star in the birth environment of the Sun, according to new computer simulations of planet formation.

Without the star's radioactive elements injected into the early solar system, our home planet could be a hostile ocean world covered in global ice sheets.

"The results of our simulations suggest that there are two qualitatively different types of planetary systems," said Tim Lichtenberg of the National Centre of Competence in Research PlanetS in Switzerland. "There are those similar to our solar system, whose planets have little water, and those in which primarily ocean worlds are created because no massive star was around when their host system formed."

Lichtenberg and colleagues, including University of Michigan astronomer Michael Meyer, were initially intrigued by the role the potential presence of a massive star played on the formation of a planet.

Meyer said the simulations help solve some questions, while raising others.

"It is great to know that radioactive elements can help make a wet system drier and to have an explanation as to why planets within the same system would share similar properties," Meyer said.

"But radioactive heating may not be enough. How can we explain our Earth, which is very dry, indeed, compared to planets formed in our models? Perhaps having Jupiter where it is was also important in keeping most icy bodies out of the inner solar system."

Researchers say while water covers more than two-thirds of the surface of Earth, in astronomical terms, the inner terrestrial planets of our solar system are very dry—fortunately, because too much of a good thing can do more harm than good.

All planets have a core, mantle (inside layer) and crust. If the water content of a rocky planet is significantly greater than on Earth, the mantle is covered by a deep, global ocean and an impenetrable layer of ice on the ocean floor. This prevents geochemical processes, such as the carbon cycle on Earth, that stabilize the climate and create surface conditions conducive to life as we know it.

The researchers developed computer models to simulate the formation of planets from their building blocks, the so-called planetesimals—rocky-icy bodies of probably dozens of kilometers in size. During the birth of a planetary system, the planetesimals form in a disk of dust and gas around the young star and grow into planetary embryos.

Radioactive heat engine

As these planetesimals are heated from the inside, part of the initial water ice content evaporates and escapes to space before it can be delivered to the planet itself.

This internal heating may have happened shortly after the birth of our solar system 4.6 billion years ago, as primeval traces in meteorites suggest, and may still be ongoing in numerous places.

Right when the proto-Sun formed, a supernova occurred in the cosmic neighborhood. Radioactive elements, including aluminium-26, were fused in this dying massive star and got injected into our young solar system, either from its excessive stellar winds or via the supernova ejecta after the explosion.

The researchers say the quantitative predictions from this work will help near-future space telescopes, dedicated to the hunt for extrasolar planets, to track potential traces and differences in planetary compositions, and refine the predicted implications of the Al-26 dehydration mechanism.

They are eagerly awaiting the launch of upcoming space missions with which Earth-sized exoplanets outside our solar system will be observable. These will bring humanity ever-closer to understanding whether our home planet is one of a kind, or if there are "an infinity of worlds of the same kind as our own."

Their study appears in Nature Astronomy. Other researchers include those from the Swiss Federal Institute of Technology, University of Bayreuth and University of Bern.


Summer solstice

Our editors will review what you’ve submitted and determine whether to revise the article.

Summer solstice, the two moments during the year when the path of the Sun in the sky is farthest north in the Northern Hemisphere (June 20 or 21) or farthest south in the Southern Hemisphere (December 21 or 22).

At the summer solstice, the Sun travels the longest path through the sky, and that day therefore has the most daylight. When the summer solstice happens in the Northern Hemisphere, the North Pole is tilted about 23.4° (23°27´) toward the Sun. Because the Sun’s rays are shifted northward from the Equator by the same amount, the vertical noon rays are directly overhead at the Tropic of Cancer (23°27´ N). Six months later, the South Pole is inclined about 23.4° toward the Sun. On this day of the summer solstice in the Southern Hemisphere, the Sun’s vertical overhead rays progress to their southernmost position, the Tropic of Capricorn (23°27´ S).

According to the astronomical definition of the seasons, the summer solstice also marks the beginning of summer, which lasts until the autumnal equinox (September 22 or 23 in the Northern Hemisphere, or March 20 or 21 in the Southern Hemisphere). The day has also been celebrated in many cultures. For example, in Scandinavia, the holiday of Midsummer’s Eve is observed on a weekend near the time of the solstice.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Adam Augustyn, Managing Editor, Reference Content.


CHAPTER III.

IF a ball is allowed to drop from the mast-head of a ship at rest, it will strike the deck at the foot of the mast. If the same experiment is tried with a ship in motion, the same result will follow because, in the latter case, the ball is acted upon simultaneously by two forces at right angles to each other--one, the momentum given to it by the moving ship in the direction of its own motion and the other, the force of gravity, the direction of which is at right angles to that of the momentum. The ball being acted upon by the two forces together, will not go in the direction of either, but will take a diagonal course, as shown in the following diagram, fig. 46.

The ball passing from A to C, by the force of gravity, and having, at the moment of its liberation, received a momentum . from the moving ship in the direction A, B, will, by the conjoint action of the two forces A, B, and A, C, take the direction A, D, falling at D, just as it would have fallen at C, had the vessel remained at rest.

It is argued by those who hold that the earth is a revolving globe, that if a ball is dropped from the mouth of a deep mine, it reaches the bottom in an apparently vertical direction, the same as it would if the earth were motionless. In the same way, and from the same cause, it is said that a ball allowed to drop from the top of a tower, will fall at the base. Admitting the fact that a ball dropped down a mine, or let fall from a high tower, reaches the bottom in a direction parallel to the side of either, it does not follow therefrom that the earth moves. It only follows that the earth might move, and yet allow of such a result. It is certain that such a result would occur on a stationary earth and it is mathematically demonstrable that it would also occur on a revolving earth but the question of motion or non-motion--of which is the fact it does not decide. It gives no proof that the ball falls in a vertical or in a diagonal direction. Hence, it is logically valueless. We must begin the enquiry with an experiment which does not involve a supposition or an ambiguity, but which will decide whether motion does actually or actually does not exist. It is certain, then, that the path of a ball, dropped from the mast-head of a stationary ship will be vertical. It is also certain that, dropped down a deep mine, or from the top of a high

tower, upon a stationary earth, it would be vertical. It is equally certain that, dropped from the mast-head of a moving ship, it would be diagonal so also upon a moving earth it would be diagonal. And as a matter of necessity, that which follows in one case would follow in every other case, if, in each, the conditions were the same. Now let the experiment shown in fig. 46 be modified in the following way:--

Let the ball be thrown upwards from the mast-head of a stationary ship, and it will fall back to the mast-head, and pass downwards to the foot of the mast. The same result would follow if the ball were thrown upwards from the mouth of a mine, or the top of a tower, on a stationary earth. Now put the ship in motion, and let the ball be thrown upwards. It will, as in the first instance, partake of the two motions--the upward or vertical, A, C, and the horizontal, A, B, as shown in fig. 47 but

because the two motions act conjointly, the ball will take the diagonal direction, A, D. By the time the ball has arrived at

[paragraph continues] D, the ship will have reached the position, 13 and now, as the two forces will have been expended, the ball will begin to fall, by the force of gravity alone, in the vertical direction, D, B, H but during its fall towards H, the ship will have passed on to the position S, leaving the ball at H, a given distance behind it.

The same result will be observed on throwing a ball upwards from a railway carriage, when in rapid motion, as shown in the following diagram, fig. 48. While the carriage or tender passes

from A to B, the ball thrown upwards, from A towards (2, will reach the position D but during the time of its fall from D to B, the carriage will have advanced to S, leaving the ball behind at B, as in the case of the ship in the last experiment.

The same phenomenon would be observed in a circus, during the performance of a juggler on horseback, were it not that the balls employed are thrown more or less forward, according to the rapidity of the horse's motion. The juggler standing in the ring, on the solid ground, throws his balls as vertically as he can, and they return to his hand but when on the back of a rapidly-moving horse, he should throw the balls vertically, before they fell

back to his hands, the horse would have taken him in advance, and the whole would drop to the ground behind him. It is the same in leaping from the back of a horse in motion. The performer must throw himself to a certain degree forward. If he jumps directly upwards, the horse will go from under him, and he would fall behind.

Thus it is demonstrable that, in all cases where a ball is thrown upwards from an object moving at right angles to its path, that ball will come down to a place behind the point from which it was thrown and the distance at which it falls behind depends upon the time the ball has been in the air. As this is the result in every instance where the experiment is carefully and specially performed, the same would follow if a ball were discharged from any point upon a revolving earth. The causes or conditions operating being the same, the same effect would necessarily follow.

The experiment shown in fig. 49, demonstrates, however, that

these causes, or conditions, or motion in the earth, do not exist.

[paragraph continues] A strong cast-iron cannon was placed with the muzzle upwards. The barrel was carefully tested with a plumb line, so that its true vertical direction was secured and the breech of the gun was firmly embedded in sand up to the touch-hole, against which a piece of slow match was placed. The cannon had been loaded with powder and ball, previous to its position being secured. At a given moment the slow match at D was fired, and the operator retired to a shed. The explosion took place, and the ball was discharged in the direction A, B. In thirty seconds the ball fell back to the earth, from B to C the point of contact, C, was only 8 inches from the gun, A. This experiment has been many times tried, and several times the ball fell back upon the mouth of the cannon but the greatest deviation was less than 2 feet, and the average time of absence was 28 seconds from which it is concluded that the earth on which the gun was placed did not move from its position during the 28 seconds the ball was in the atmosphere. Had there been motion in the direction from west to east, and at the rate of 600 miles per hour (the supposed velocity in the latitude of England), the result would have been as shown in fig. 49. The ball, thrown by the powder in the direction A, C, and acted on at the same moment by the earth's motion in the direction A, B, would take the direction A, D meanwhile the earth and the cannon would have reached the position B, opposite to D. On the ball beginning to descend, and during the time of its descent, the gun would have passed on to the position S, and the ball would have dropped at B, a consider-able distance behind the point S. As the average time of the ball's absence in the atmosphere was 28 seconds--14 going upwards, and 14 in falling--we have only to multiply the time by the supposed velocity of the earth, and we find that instead of the ball coming down to within a few inches of the

muzzle of the gun, it should have fallen behind it a distance of 8400 feet, or more than a mile and a half! Such a result is utterly destructive of the idea of the earth's possible rotation.

The reader is advised not to deceive himself by imagining that the ball would take a parabolic course, like the balls and shells from cannon during a siege or battle. The parabolic curve could only be taken by a ball fired from a cannon inclined more or less from the vertical when, of course, gravity acting in an angular direction against the force of the gunpowder, the ball would be forced to describe a parabola. But in the experiment just detailed, the gun was fixed in a perfectly vertical direction, so that the ball would be fired in a line the very contrary to the direction of gravity. The force of the powder would drive it directly upwards, and the force of gravity would pull it directly downwards. Hence it could only go up in a right line, and down or back to its starting point it could not possibly take a path having the slightest degree of curvature. It is therefore demanded that, if the earth has a motion from west to east, a ball, instead of being dropped down a mine, or allowed to fall from the top of a tower, shall be shot upwards into the air, and from the moment of its beginning to descend, the surface of the earth shall turn from under its direction, and it would fall behind, or to the west of its line of descent. On making the most exact experiments, however, no such effect is observed and, therefore, the conclusion is in every sense unavoidable, that THE EARTH HAS NO MOTION OF ROTATION.

EXPERIMENT 3.

When sitting in a rapidly-moving railway carriage, let a spring-gun 1 be fired forward, or in the direction in which the train is moving. Again, let the same gun be fired, but in the opposite direction and it will be found that the ball or other projectile will always go farther in the first case than in the latter.

If a person leaps backwards from a horse in full gallop, he cannot jump so great a distance as he can by jumping forward. Leaping from a moving sledge, coach, or other object, backwards or forwards, the same results are experienced.

Many other practical cases could be cited to show that any body projected from another body in motion, does not exhibit the same behaviour as it does when projected from a body at rest. Nor are the results the same when projected in the same direction as that in which the body moves, as when projected in the opposite direction because, in the former case, the projected body receives its momentum from the projectile force, plus that given to it by the moving body and in the latter case, this momentum, minus that of the moving body. Hence it would be found that if the earth is a globe, and moving rapidly from west to east, a cannon fired in a due easterly direction would send a ball to a greater distance than it would if fired in a due westerly direction. But the most experienced artillerymen--many of whom have had great practice, both at home and abroad, in almost every latitude--have declared that no difference whatever is

observable. That in charging and pointing their guns, no, difference in the working is ever required, notwithstanding that the firing is at every point of the compass. Gunners in war ships have noticed a considerable difference in the results of their firing from guns at the bow, when sailing rapidly towards the object fired at, and when firing from guns placed at the stern while sailing away from the object: and in both cases the results are different to those observed when firing from a ship at perfect rest. These details of practical experience are utterly incompatible with the supposition of a revolving earth.

During the period of the Crimean War, the subject of gunnery, in connection with the earth's rotation, was one which occupied the attention of many philosophers, as well as artillery officers and statesmen. About this time, Lord Palmerston, as Prime Minister, wrote the following letter to Lord Panmure, the Secretary for War:--

"There is an investigation which it would be important and at the same time easy to make, and that is, whether the rotation of the earth on its axis has any effect on the curve of a cannon-ball in its flight. One should suppose that it has, and that while the cannon-ball is flying in the air, impelled by the gunpowder in a straight line from the cannon's mouth, the ball would not follow the rotation of the earth in the same manner which it would do if lying at rest on the earth's surface. If this be so, a ball fired in the meridional direction--that is to say, due south or due north--ought to deviate to the west of the object at which it was.

aimed, because during the time of flight, that object will have gone to the east somewhat faster than the cannon-ball will have done. In like manner, a ball fired due east, ought to fly less far upon the earth's surface than a ball fired due west, the charges being equal, the elevation the same, and the atmosphere perfectly still. It must be remembered, however, that the ball, even after it has left the cannon's mouth, will retain the motion from west to east which it had before received by the rotation of the earth on whose surface it was and it is possible, therefore, that, except at very long ranges, the deviations above mentioned may in practice turn out to be very small, and not deserving the attention of an artilleryman. The trial might be easily made in any place in which a free circle of a mile or more radius could be obtained and a cannon placed in the centre of that circle, and fired alternately north, south, east, and west, with equal charges, would afford the means of ascertaining whether each shot flew the same distance or not.

The above letter was published, by Lord Dalhousie's permission, in the "Proceedings of the Royal Artillery Institution for 1867."

It will be observed that Lord Palmerston thought that firing eastwards, or in the direction of the earth's supposed rotation, the ball would "fly less far upon the earth's surface than a ball fired due west." It is evident that his Lordship did not allow for the extra impulse given to the ball by the earth's motion. But the answer given by the advocates of the theory of the earth's motion is the following: Admitting that a ball fired from the

earth at rest would go, say two miles, the same ball, fired from the earth in motion, would go, say three miles but during the time the ball is passing through the air, the earth will advance one mile in the same direction. This one mile deducted from the three miles which the ball actually passes through the air, leaves the two miles which the ball has passed in advance of the cannon so that practically the distance to which a ball is projected is precisely the same upon a moving earth as it is upon the earth at rest. The following diagram, fig. 50, will illustrate the path of a ball under the conditions above described.

Let the curved line A, B, represent the distance a ball would fly from a cannon placed at A, upon the earth, at rest. Let A, C, represent the distance the same ball would fly from the conjoint action of the powder in the cannon, A, and the earth's rotation in the direction A, C. During the time the ball would require to traverse the line A, C, the earth and the cannon would arrive at the point D hence the distance D, C, would be the same as the distance A, B.

The above explanation is very ingenious, and would be perfectly satisfactory if other considerations were not involved in it. For instance, the above explanation does not prove the earth's motion--it merely supposes it but

as in all other cases where the result of supposition is explained, it creates a dilemma. It demands that during the time the ball is in the air, the cannon is advancing in the direction of the supposed motion of the earth. But -this is granting the conditions required in the experiments represented by figs. 47, 48, and 49. If the cannon can advance in the one case, it must in the other and as the result in the experiment represented at fig. 49, was that the ball, when fired vertically, essentially returned to the vertical cannon that cannon could not have advanced, and therefore the earth could not have moved.

EXPERIMENT 4.

Take a large grinding stone, and let the whole surface of the rim be well rubbed over with a saturated solution of phosphorus in olive oil or cover the stone with several folds of coarse woollen cloth or flannel, which saturate with boiling water. If it be now turned rapidly round, by means of a multiplying wheel, the phosphoric vapour, or the steam from the flannel, which surrounds it and which may be called its atmosphere--analogous to the atmosphere of the earth--will be seen to follow the direction of the revolving surface. Now the surface of the earth is very irregular in its outline, mountains rising several miles above the sea, and ranging for hundreds of miles in every possible direction rocks, capes, cliffs, gorges, defiles, caverns, immense forests, and every other form of ruggedness and irregularity calculated to adhere to and drag along whatever medium may exist upon it: and if it is a globe revolving on its axis, with

the immense velocity at the equator of more than a thousand miles an hour, it is exceedingly difficult if not altogether impossible to conceive of such a mass moving at such a rate, and yet not taking the atmosphere along with it. When it is considered, too, that the medium which it is said surrounds the earth and all the heavenly bodies, and filling all the vast spaces between them, is almost too ethereal and subtle to offer any sensible resistance, it is still more difficult to understand how the atmosphere can be prevented being carried forward with the earth's rapidly revolving surface. Study the details of pneumatics or hydraulics as we may, we cannot suggest an experiment which will show the possibility of such a thing. Hence we are compelled to conclude that if the earth revolves, the atmosphere revolves also, and in the same direction. If the atmosphere rushes forward from west to east continually, we are again obliged to conclude that whatever floats or is suspended in it, at any altitude, must of necessity partake of its eastward motion. A piece of cork, or any other body floating in still water, will be motionless, but let the water be put in motion, in any direction whatever, and the floating bodies will move with it, in the same direction and with the same velocity. Let the experiment be tried in every possible way, and these results will invariable follow. Hence if the earth's atmosphere is in constant motion from west to east, all the different strata which are known to exist in it, and all the various kinds of clouds and vapours which float in it must of mechanical necessity move rapidly eastwards. But what is the fact? If we fix upon any star as a standard or datum outside the visible atmosphere, we may sometimes observe a stratum of clouds going for hours together in a direction the very opposite to that in which the earth is supposed to be moving. See fig. 51, which represents a section of a

globe, surrounded with an atmosphere, moving at the rate of 1042 miles an hour at the equator, and in the direction of the arrows 1, 2, 3, while a stream of clouds are moving in the opposite direction, as indicated by the arrows, 4, 5, 6. Not only may a stratum of clouds be seen moving rapidly from east to west, but at the same moment other strata may often be seen moving from north to south, and from south to north. It is a fact well known to aeronauts, that several strata of atmospheric air are often moving in as many different directions at the same time. It is a knowledge of this fact which leads an experienced aeronaut, when desiring to rise in a balloon, and to go in a certain direction, not to regard the manner in which the wind is blowing on the immediate surface of the earth, because he knows that at a greater altitude, it may be going at right angles, or even in opposite and in various ways simultaneously. To ascertain whether and at what altitude a current is blowing in the desired direction, small, and so-called "pilot-balloons" are often sent up and carefully observed in their ascent. If during the passage of one of these through the variously moving

strata, it is seen to enter a current which is going in the direction desired by the aëronaut, the large balloon is then ballasted in such a manner that it may ascend at once to the altitude of such current, and thus to proceed on its journey.

On almost any moonlight and cloudy night, different strata may be seen not only moving in different directions but, at the same time, moving with different velocities some floating past the face of the moon rapidly and uniformly, and others passing gently along, sometimes becoming stationary, then starting fitfully into motion, and often standing still for minutes together. Some of those who have ascended in balloons for scientific purposes have recorded that as they have rapidly passed through the atmosphere, they have gone though strata differing in temperature, in density, and in hygrometric, magnetic, electric, and other conditions. These changes have been noticed both in ascending and descending, and in going for miles together at the same altitude.

"On the 27th November, 1839, the sky being very clear, the planet Venus was seen near the zenith, notwithstanding the brightness of the meridian sun. It enabled us to observe the higher stratum of clouds to be moving in an exactly opposite direction to that of the wind--a circumstance which is frequently recorded in our meteorological journal both in the north-east and south-east trades, and has also often been observed by former voyagers. Captain Basil Hall witnessed it from the summit of the Peak of Teneriffe and Count Strzelechi, on ascending the volcanic mountain of Kiranea, in Owhyhee, reached at 4000 feet an elevation above that of the trade wind, and experienced the influence of an opposite current of air of a

different hygrometric and thermometric condition. . . . Count Strzelechi further informed me of the following seemingly anomalous circumstance--that at the height of 6000 feet he found the current of air blowing at right angles to both the lower strata, also of a different hygrometric and thermometric condition, but warmer than the inter-stratum." 1

Such a state of the atmosphere is compatible only with the fact which other evidence has demonstrated, that the earth is at rest. Were it otherwise-if a spherical mass of eight thousand miles in diameter, with an atmosphere of only fifty miles in depth, or relatively only as a sheet of note paper pasted upon a globe of one yard in diameter, and lying upon a rugged, adhesive, rapidly revolving surface, there is nothing to prevent such an atmosphere becoming a mingled homogeneous mass of vapour.

Notwithstanding that all practical experience, and all specially instituted experiments are against the possibility of a moving earth, and an independent moving and non-moving atmosphere, many mathematicians have endeavoured to "demonstrate" that with regard to this earth, such was actually the case. The celebrated philosophic divine, Bishop Wilkins, was reasoned by the theorists of his day into this belief and, in consequence, very naturally suggested a new and easy way of travelling. He proposed that large balloons should be provided with apparatus to work against the varying currents of the air. On ascending to a proper altitude, the balloon was to be kept practically in a state of rest, while the earth revolved underneath it and when the desired locality came into view, to stop the working of

the fans, &c., to let out the gas, and drop down at once to the earth's surface. In this simple way New York would be reached in a few hours, or rather New York would reach the balloon, at the rate, in the latitude of England, of more than 600 miles an hour.

The argument involved in the preceding remarks against the earth's rotation has often been met by the following, at first sight, plausible statement. A ship with a number of passengers going rapidly in one continued direction, like the earth's atmosphere, could nevertheless have upon its deck a number of distinctly and variously moving objects, like the clouds in the atmosphere. The clouds in the atmosphere are compared to the passengers on the deck of a ship so far the cases are sufficiently parallel, but the passengers are sentient beings, having within themselves the power of distinct and independent motions: the clouds are the reverse and here the parallelism fails. One case is not illustrative of the other, and the supposition of rotation in the earth remains without a single fact or argument in its favour. Birds in the air, or fish and reptiles in the water, would have offered a parallel and illustrative case, but these, like the passengers on the ship's deck, are sentient and independent beings clouds and vapours are dependent and non-sentient, and must therefore of necessity move with, and in the direction of, the medium in which they float.

Everything actually observable in Nature every argument furnished by experiment every legitimate process of reasoning and, as it would seem, everything which it is possible for the human mind practically to conceive, combine

in evidence against the doctrine of the earth's motion upon axes.

ORBITAL MOTION.--The preceding experiments and remarks, logically and mathematically suffice as evidence against the assumed motion of the earth in an orbit round the sun. It is difficult, if not impossible, to understand how the behaviour of the ball thrown from a vertical gun should be other in relation to the earth's forward motion in space, than it is in regard to its motion upon axes. Besides, it is demonstrable that it does not move upon axes, and therefore, the assumption that it moves in an orbit, is utterly useless for theoretical purposes. The explanation of phenomena, for which the theory of orbital and diurnal motion was framed, is no longer possible with a globular world rushing through space in a vast elliptical orbit, but without diurnal rotation. Hence the earth's supposed orbital motion is logically void, and non-available, and there is really no necessity for either formally denying it, or in any way giving it further consideration. But that no point may be taken without direct and practical evidence, let the following experiment be tried.

Take two carefully-bored metallic tubes, not less than six feet in length, and place them one yard asunder, on the opposite sides of a wooden frame, or a solid block of wood or stone: so adjust them that their centres or axes of vision shall be perfectly parallel to each other. The following diagram will show the arrangement.

Now, direct them to the plane of some notable fixed star, a few seconds previous to its meridian time. Let an observer be stationed at each tube, as at A, B and the moment the star appears in the tube A, T, let a loud knock or other signal be given, to be repeated by the observer at the tube B, T, when he first sees the same star. A distinct period of time will elapse between the signals given. The signals will follow each other in very rapid succession, but still, the time between is sufficient to show that the same star, S, is not visible at the same moment by two parallel lines of sight A, S, and B, C, when only one yard asunder. A slight inclination of the tube, B, C, towards the first tube A, S, would be required for the star, S, to be seen through both tubes at the same instant. Let the tubes remain in their position for six months at the end of which time the same observation or experiment will produce the same results--the star, S, will be visible at the same meridian time, without the slightest alteration being required in the direction of the tubes: from which it is concluded that if the earth had moved one single yard in an orbit through space, there would at least be observed the slight inclination of the tube, B, C, which the difference in position of one yard had previously required.

[paragraph continues] But as no such difference in the direction of the tube B, C, is required, the conclusion is unavoidable, that in six months a given meridian upon the earth's surface does not move a single yard, and therefore, that the earth has not the slightest degree of orbital motion.

Copernicus required, in his theory of terrestrial motions, that the earth moved in an extensive elliptical path round the sun, as represented in the following diagram, fig 53, where S is the

sun, A, the earth in its place in June, and B, its position in December when desired to offer some proof of this orbital motion he suggested that a given star should be selected for observation on a given date and in six months afterwards a second observation of the same star should be made. The first observation A, D, fig. 53, was recorded and on observing again at the end of six months, when the earth was supposed to have passed to B, the other side of its orbit, to the astonishment of the assembled astronomers, the star was observed in exactly the

same position, B, C, as it had been six months previously! It was expected that it would be seen in the direction B, D, and that this difference in the direction of observation would demonstrate the earth's motion from A to B, and also furnish, with the distance A, S, B, the elements necessary for calculating the actual distance of the star D.

The above experiment has many times been tried, and always with the same general result. No difference whatever has been observed in the direction of the lines of sight A, D, and B, C, whereas every known principle of optics and geometry would require, that if the earth had really moved from A to B, the fixed star D, should be seen in the direction B, D. The advocates of this hypothesis of orbital motion, instead of being satisfied, from the failure to detect a difference in the angle of observation, that the earth could not possibly have changed its position in the six months, were so regardless of all logical consistency, that instead of admitting, and accepting the consequences, they, or some of them, most unworthily declared that they could not yield up the theory, on account of its apparent value in explaining certain phenomena, but demanded that the star D, was so vastly distant, that, notwithstanding that the earth must have moved from A to B, this great change of position would not give a readable difference in the angle of observation at B, or in other words the amount of parallax (" annual parallax," it was called) was inappreciable!

Since the period of the above experiments, many have declared that a very small amount of "annual parallax" has been detected. But the proportion given by different observers has been so various, that nothing definite and satisfactory can yet be decided upon. Tycho Brahe, Kepler, and others, rejected the Copernican theory, principally

eon account of the failure to detect displacement or parallax of the fixed stars. Dr. Bradley declared that what many had called "parallax," was merely "aberration." But "Dr. Brinkley, in 1810, from his observations with a very fine circle in the Royal Observatory of Dublin, thought he had detected a parallax of 1″ in the bright star Lyra (corresponding to an annual displacement of 2″). This, however, proved to be illusory and it was not till the year 1839, that Mr. Henderson, having returned from filling the situation of astronomer royal to the Cape of Good Hope, and discussing as series of observations made there with a large "mural circle," of the bright star, α Centauri, was enabled to announce as a positive fact the existence of a measurable parallax for that star, a result since fully confirmed with a very trifling correction by the observations of his successor, Sir T. Maclear. The parallax thus assigned α Centauri, is so very nearly a whole second in amount (0″.98), that we may speak of it as such. It corresponds to a distance from the sun of 18,918,000,000,000 British statute miles.

"Professor Bessel made the parallax of a star in the constellation Cygnus to be 0″.35. Later astronomers, going over the same ground, with more perfect instruments, and improved practice in this very delicate process 'of observation, have found a somewhat larger result, stated by one at 0″.57, and by another at 0″.51, so that we may take it at 0″.54, corresponding to somewhat less than twice the distance of a Centauri" 1 or to nearly 38 billions of miles.

It might seem to a non-scientific mind that the differences

above referred to of only a few fractions of a second in the parallax of a star, constitute a very slight amount but in reality such differences involve differences in the distance of such stars of millions of miles, as will be seen by the following quotation from the Edinburgh Review for June, 1850:--

"The rod used in measuring a base line is commonly ten feet long and the astronomer may be said only to apply this very rod to measure the distance of the fixed stars! An error in, placing a fine dot, which fixes the length of the rod, amounting to one five-thousandth part of an inch, will amount to an excess, of 70 feet in the earth's diameter of 316 miles in the sun's distance, and to 65,200,000 miles in that of the nearest fixed star!

"The second point to which we would advert is, that as the astronomer in his observatory has nothing to do with ascertaining length as distances, except by calculation, his whole skill and artifice are exhausted in the measurement of angles. For it is by these alone that spaces inaccessible can be compared. Happily a ray of light is straight. Were it not so (in celestial spaces at least) there were an end of our astronomy. It is as inflexible as adamant, which our instruments unfortunately are not. Now an angle of a second (3600 to a degree), is a subtle thing, it is an apparent breadth, utterly invisible to the unassisted eye, unless accompanied by so intense a splendour (as in the case of the fixed stars) as actually to raise by its effect on the nerve of sight a spurious image, having a sensible breadth. A silkworm's fibre subtends an angle of one second at 3½ feet distance. A ball 2½ inches in diameter must be removed in order to subtend an angle of one second, to 43,000 feet, or about 8 miles while it would be utterly invisible to the sharpest sight aided even by a telescope of some power. Yet it is on the

measurement of one single second that the ascertainment of a sensible parallax in any fixed star depends and an error of one-thousandth of that amount (a quantity still immeasurable by the most perfect of our instruments) would place a fixed star too far or too near by 200,000,000,000 of miles."

"The observations require to be made with the very best instruments, with the minutest attention to everything which can affect their precision, and with the most rigorous application of an innumerable host of 'corrections,' some large, some small, but of which the smallest, neglected or erroneously applied, would be quite sufficient to overlay and conceal from view the minute quantity we are in search of. To give some idea of the delicacies which have to be attended to in this inquiry, it will suffice to mention that the stability not only of the instruments used and the masonry which supports them, but of the very rock itself on which it is founded, is found to be subject to annual fluctuations capable of seriously affecting the result."

Dr. Lardner, in his "Museum of Science," page 179, makes use of the following words

"Nothing in the whole range of astronomical research has more baffled the efforts of observers than this question of the parallax. * * * Now, since, in the determination of the exact uranographical position of a star, there are a multitude of disturbing effects to be taken into account and eliminated, such as precession, nutation, aberration, refraction, and others, besides the proper motion of the star and since, besides the errors of observation, the quantities of these are subject to more or less uncertainty, it will astonish no one to be told that they may en-tail upon the final result of the calculation, an error of 1″ and

if they do, it is vain to expect to discover such a residual phenomenon as parallax, the entire amount of which is less than one second."

The complication, uncertainty, and unsatisfactory state of the question of annual parallax, and therefore of the earth's motion in an orbit round the sun, as indicated by the several paragraphs above quoted, are at once and for ever annihilated by the simple fact, experimentally demonstrable, that upon a base line of only a single yard, there may be found a parallax, as certain and as great, if not greater, than that which astronomers pretend to find with the diameter of the earth's supposed orbit of many millions of miles as a base line. To place the whole matter, complicated, uncertain, and unsatisfactory as it is, in a concentrated form, it is only necessary to state as an absolute truth the result of actual experiment, that, a given fixed star will, when observed from the two ends of a base line of not more than three feet, give a parallax equal to that which it is said is observed only from the two extremities of the earth's orbit, a distance or base line, of one hundred and eighty millions of miles! So far, then, from the earth having passed in six months over the vast space of nearly two hundred millions of miles, the combined observations of all the astronomers of the whole civilized world have only resulted in the discovery of such elements, or such an amount of annual parallax, or sidereal displacement, as an actual change of position of a few feet will produce. It is useless to say, in explanation, that this very minute displacement, is owing to the almost infinite distance of

the fixed stars because the very same stars show an equal degree of parallax from a very minute base line and, secondly, it will be proved from practical data, in a subsequent chapter, that all the luminaries in the firmament are only a few thousand miles from the surface of the earth.

Footnotes

69:1 The barrel containing a spiral spring, so that the projecting force will always be the same, which might not be so with gunpowder.


Astrology vs Astronomy

Astrology continued to be part of mainstream science until the late 1600s, when Isaac Newton demonstrated some of the physical processes by which celestial bodies affect each other. In doing so, he showed that the same laws that make, say, an apple fall from a tree, also apply to the motions of the celestial sphere. Since then, astronomy has evolved into a completely separate field, where predictions about celestial phenomena are made and tested using the scientific method.

In contrast, astrology is now regarded as a pastime and a pseudoscience — though thousands of people around the world still invoke advice from astrologers and astrology publications in making important professional, medical, and personal experiences. (This, despite the fact that current horoscopes rely on outdated information!)

Why Astrology "Works"

Yet there's a reason people continue to rely on horoscopes, and Senior Editor Alan MacRobert explains in Sky & Telescope's Focal Point column just why astrology is still so popular.

Planets have nothing to do with it. But that's not the point. If you want to get through to your believing sister-in-law or your uncle in Cincinatti, the way to do it is not to argue physics or astronomy, but to explain why astrology works.

I tell this with my own story. When I was in elementary school, I practiced a form of divination that you could call bazookamancy. Back then, Bazooka Joe bubble gum was popular. It came wrapped in a little comic strip about Bazooka Joe and his gang. The wrappers were on the ground wherever kids littered. As everyone knew, when you saw one, you stopped and asked it a question. Then you picked it up and read it. The comic was a parable that answered your question. Often you had to look mighty hard to find your answer. But if you looked hard enough, it was always there.

. . . I've described my practice of bazookamancy to two of my astrologer friends. Each of them lit up and say, "You've got it!" So at some level, they know it isn't about the planets, not if one form of divination is as good as another. Any reading or fluke or chance — any metaphor looking for its referent — will serve your uncle in Cincinnati just as well.