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(The Venera 11 and 12 analyses claim 30 ppm COS near the surface, and Earth-based infrared spectroscopy claims 0.25 ppm COS near 50 km altitude.) The H2S pressure can be calculated from the exchange reaction
$$COS + H_2O \rightarrow CO_2 + H_2S \qquad (X.81)$$
$$K_{81} = (p_{\text{H}_2\text{S}}/p_{\text{COS}})(p_{\... | {
"Header 1": "Venus: Atmosphere–Lithosphere Interactions",
"token_count": 1267,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
At the upper boundary of the troposphere an entirely different suite of reactions, driven by ultraviolet sunlight, comes into play. Sulfur dioxide and other sulfur gases can be chemically processed by reactions with strong oxidizing agents derived from photolysis of water vapor and carbon dioxide. The initial photochem... | {
"Header 1": "Venus: Photochemistry and Aeronomy",
"token_count": 2048,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The role of chlorine in destroying ozone, which was originally proposed in the context of Venus photochemistry, has been "brought home" to Earth and is the basis for our present understanding of the effects of Cl (produced by photolysis of anthropogenic chlorofluorocarbons, CFCs) on the ozone layer.
At altitudes abov... | {
"Header 1": "Venus: Photochemistry and Aeronomy",
"token_count": 2037,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Near present H abundances (arrow), both nightside charge exchange and impact of hot O atoms are important. Some authors, neglecting cometary and asteroidal infall, assume that Venus began with a high total H content (i.e., water rich) and has suffered unidirectional hydrogen loss over its history. They therefore interp... | {
"Header 1": "Venus: Photochemistry and Aeronomy",
"token_count": 783,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Physicist Robert O. Pepin of the University of Minnesota has proposed a complex model to explain the elemental and isotopic fractionations of the rare gases on the terrestrial planets. This model, based upon a theory of fractionation during hydrodynamic escape developed by Donald M. Hunten, envisions much larger abunda... | {
"Header 1": "Venus: Planetary Evolution",
"token_count": 1252,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The vast majority of all human knowledge of the planets is knowledge of Earth. To see Earth in a true planetary perspective, in proper relationship to the other planets, requires distilling and abstracting this vast body of terrestrial knowledge. It further requires setting aside the natural presumption that whatever i... | {
"Header 1": "Earth",
"token_count": 2021,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
This Gregorian calendar was immediately adopted by the Catholic nations, but was not accepted in England until 1752 (indeed, England regarded the first day of the year as March 25 up to that time!). The change was greeted by rioting mobs of English subjects who chanted, ''Give us back our fortnight!'' To this day Engla... | {
"Header 1": "Earth",
"token_count": 287,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The density of Earth (about 4 g cm-<sup>3</sup> uncompressed) is too high to be explained by plausible silicate minerals alone. Like primitive, ancient chondritic meteorites (Chapter VII), Earth must contain a significant percentage of metallic iron–nickel alloy. Indeed, the densest chondrites are about 4% less dense t... | {
"Header 1": "Earth: Internal Structure",
"token_count": 1510,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Direct evidence regarding the rate of heat generation in the core is lacking, but several relevant phenomena help constrain that rate. First, Earth has a rather strong planetary dipole field with a mean surface field strength of about 0.6 G that is roughly aligned with the spin axis (the north magnetic pole is in the N... | {
"Header 1": "Earth: Internal Structure",
"Header 2": "Earth: Magnetic Field and Magnetosphere",
"token_count": 587,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The visible surface of Earth is divided naturally into oceans and continents. However, a careful study of the distribution of altitudes on Earth show a somewhat more complex and more interesting dichotomy. As we saw in the Earth hypsogram in Fig. X.2, the distribution of surface topography on Earth is in fact bimodal. ... | {
"Header 1": "Earth: Internal Structure",
"Header 2": "Earth: Surface Geology",
"token_count": 2028,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
In areas where nearly continuous volcanic activity has occurred over the past few million years, such as Earth: Early Geological History 557
Hawaii, Iceland, and various sites in North America and Russia, it is possible to measure the gas-retention ages and paleomagnetic properties of numerous samples closely space... | {
"Header 1": "Earth: Internal Structure",
"Header 2": "Earth: Surface Geology",
"token_count": 595,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Reconstructions of the geological and biological history of Earth are closely connected because of the central role of fossils in assigning ages to rock units. Major discontinuities in the rock record and in the corresponding fossil record are used as the dividing lines between geographical ages. Within each age the pa... | {
"Header 1": "Earth: Early Geological History",
"token_count": 2040,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
First, the recent accretion of the planet had released enough heat to melt the interior thoroughly. Indeed, depending upon how and when volatiles were first released into the atmosphere and precisely how and how fast accretion occurred, the entire planetary surface may have been blanketed under a dense steam atmosphere... | {
"Header 1": "Earth: Early Geological History",
"token_count": 422,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The earliest evidence of life on Earth is the presence of biogenic organic matter in sedimentary rocks dating back to 3.8 Ga BP. The most distinctive molecules found in these rocks (Fig. X.45) include the normal alkanes, which are linear hydrocarbons of general formula (H3C–(CH2)x–CH3; porphyrins, which are complex pol... | {
"Header 1": "Earth: Biological History",
"token_count": 2039,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Crinoids (sea lilies; echinoderms related to starfish, sand dollars, sea urchins, and sea cucumbers) were common. The dominant life-forms of the time were large molluscs, including huge nautiloids with straight conical shells extending up to 4 m in length. The nautiloids and other cephalopods such as the squid and octo... | {
"Header 1": "Earth: Biological History",
"token_count": 2022,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Huge amounts of nitrates and organic matter from decaying plants fecundated the oceans, sparking an explosive proliferation and diversification of life. And the lowly mammals, at last given an opportunity, became masters of the world.
The total elapsed time since the Cretaceous, only 65 million years, is less than 1.... | {
"Header 1": "Earth: Biological History",
"token_count": 282,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The average elemental composition of the crust is compared with the bulk composition of Earth in Table X.5. We have already remarked on the enhancement of the abundances of Si, Al, Ca, and the alkali metals in the crust relative to the rest of the planet. Consideration of the abundances of all the elements in the crust... | {
"Header 1": "Earth: Geochemistry and Petrology",
"token_count": 2001,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
At about 1250 K hornblende would also crystallize, but hornblende is formed by
Figure X.47 Igneous rock types. The mineralogical composition of terrestrial crustal igneous rocks is shown as a function of silica (SiO2) content in the lower panel. The names of the corresponding rock types... | {
"Header 1": "Earth: Geochemistry and Petrology",
"token_count": 1888,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Many minerals, when exposed to water and air, are subject to chemical attack. Iron and aluminum oxides are very insoluble and unreactive in a wet, oxidizing environment in the absence of strong acids or bases. The acidity or alkalinity (basicity) of aqueous solutions is determined by the relative concentrations of hydr... | {
"Header 1": "Weathering in the Rock Cycle",
"token_count": 2048,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Nitrogen oxides, which react with oxygen and water vapor as discussed above to make nitric acid, suffer a very different fate; fixed nitrogen (compounds of nitrogen with other elements) is a limiting nutrient in the biosphere and is scavenged by biological processes to make amino acids and organic bases. The rare occur... | {
"Header 1": "Weathering in the Rock Cycle",
"token_count": 2045,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
These factors combine to lend these gases an importance far out of proportion to their seemingly minor abundance.
Several other gases in the troposphere are maintained by photochemical processes. Methane oxidation produces carbon monoxide, and hydrogen is produced during UV photolysis of water vapor. Hydrogen peroxid... | {
"Header 1": "Weathering in the Rock Cycle",
"token_count": 2027,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Nearly 40% of the sulfur dioxide in the present troposphere is anthropogenic, resulting mainly from combustion of fossil fuels. Smelters and volcanic eruptions are also extremely potent local sources of SO2. Both local and regional acid rain is strongly exacerbated by sulfuric acid produced by further oxidation of sulf... | {
"Header 1": "Weathering in the Rock Cycle",
"token_count": 2032,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The difference between the isotopic composition of the condensed phase and the vapor decreases at higher temperatures, where chaos reigns. The thermodynamic argument why there must be isotopic fractionation is simple and elegant: suppose a liquid solution of H<sub>2</sub> and HD is in equilibrium with its own vapor. Eq... | {
"Header 1": "Weathering in the Rock Cycle",
"token_count": 2027,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
With a total atmospheric pressure of $0.98 \times 10^6$ dyn cm<sup>-2</sup> at the surface, the column abundance of <sup>3</sup>He is then about $6.7 \times 10^{-10}$ g cm<sup>-2</sup>, or
$1.3 \times 10^{14}$ atoms cm<sup>-2</sup>. The characteristic escape time for $^3\text{He}$ is then about $3 \times 10^{... | {
"Header 1": "Weathering in the Rock Cycle",
"token_count": 1993,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Where is it? Alternatively, appeal to comet nuclei (60% water instead of 20% water) lowers the relative amount of ferric oxide from about 20% to 8%, an amount closely similar to the observed lithospheric inventory—but this would require that all of the vastly larger amount of oxygen liberated by water dissociation must... | {
"Header 1": "Weathering in the Rock Cycle",
"token_count": 1040,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
At least three times during the history of Earth there have been extended periods of glaciation. The first of these, the Huronian glaciation, occurred about 2.5 Ga BP. The second glacial era, at 0.8 Ga BP, occurred in the late Precambrian. The third great ice age is still in progress. In the present ice age, as many as... | {
"Header 1": "Climate History, Polar Ice, and Ice Ages",
"token_count": 2017,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Direct surface thermometer data from weather stations (which are concentrated in urban areas and airports, both major ''heat islands'') show an uneven warming trend. Balloon payloads in the middle atmosphere show very little warming. Weather satellites carrying infrared sensors have provided data since the 1960s that a... | {
"Header 1": "Climate History, Polar Ice, and Ice Ages",
"token_count": 1086,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Present understanding of the origin of life is based upon certain ideas related to the propagation of order and complexity by chemical mechanisms. Living organisms familiar to us all use the same basic genetic code and the same building blocks for the complex molecules that carry the genetic code and build the structur... | {
"Header 1": "Life: Origins",
"token_count": 1789,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Some proteins ''wrap up'' metal ions to make extremely
| Name | Abbreviation | Formula |
|-------------------------|---------------------|------------------------------------------------------... | {
"Header 1": "Life: Origins",
"token_count": 2027,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The uniformitarian view of Earth, which reflects the ''normal'' state of affairs, is a good approximation on short time scales. But over extended periods of time, rare events become unavoidable. Because some of these rare events are immensely powerful, they may impose catastrophic changes on environments and population... | {
"Header 1": "Life: Stability of the Biosphere",
"token_count": 867,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
#### Mars
- X.1 a. What is the acceleration of gravity on the equator of Mars? Remember to allow for the rotation of the planet.
- b. What is g at the Martian poles?
#### Motions of Mars
X.2 By what factor does the effective temperature of Mars change in going from perihelion to aphelion?
#### Geophysical Data ... | {
"Header 1": "Exercises",
"token_count": 1982,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
What minimum speed is needed to move $100 \,\mu\text{m}$ (0.01-cm) particles of density 2.4 at the following places?
- (i) Earth's subaerial surface
- (ii) The surface of Venus
- (iii) The surface of Mars
- (iv) The bottom of a lake or stream on Mars
- b. Would particles of this size be mobilized by the measured wind... | {
"Header 1": "Exercises",
"token_count": 1066,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Are we alone? Is there life elsewhere in our Solar System, or in our galactic neighborhood? Is there intelligent life elsewhere in space? Can we make contact with them or visit them, or they visit us? These are profound questions, ones that we cannot yet answer with confidence. Negative answers would be of as fundament... | {
"Header 1": "XI. Planets and Life around Other Stars",
"token_count": 225,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
An essential prerequisite to life is the availability of a chemical system that can store, read, and write very complex genetic information. Such a high level of complexity requires a chemistry within which stable molecules of intricate structure and high information content can be synthesized, read, and transcribed. F... | {
"Header 1": "Chemical and Physical Prerequisites of Life",
"token_count": 2033,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Their only known biological function on Earth is as a poison for killing slugs and snails. Equation (XI.10), with sugar molecules linking phosphate units into long chains, can encode information either by having different sugar molecules S, S<sup>0</sup> , S<sup>00</sup>, etc., in the chain, or by having a single essen... | {
"Header 1": "Chemical and Physical Prerequisites of Life",
"token_count": 2028,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
These difficulties may be ameliorated to some degree by postulating super-Jovian planets, which cool more slowly than Jovian planets, preserving liquid water clouds for billions of years. This apparent temporal advantage, however, is largely offset by the very long time required for the most massive super-Jovian plan... | {
"Header 1": "Chemical and Physical Prerequisites of Life",
"token_count": 2017,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Since the internal heat source of Earthissimo is 12 times that of Earth, spread over four times the surface area, the density or intensity of hydrothermal vent activity should be several times higher than experienced on Earth's abyssal plains.
Terrestrial-type planets containing sufficient carbon, hydrogen, oxygen, n... | {
"Header 1": "Chemical and Physical Prerequisites of Life",
"token_count": 2033,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
For an M9 star, teetering at the very threshold of the Main Sequence, with a luminosity of $10^{-4} L_{\odot}$ , Earthlike temperatures would be achieved at a distance of 0.01 AU ( $15 \times 10^5$ km), and the Roche limit would be near $4.8 \times 10^5$ km. Slightly less massive bodies, incapable of sustained fusi... | {
"Header 1": "Chemical and Physical Prerequisites of Life",
"token_count": 2003,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
It can be shown that this expression is equivalent to
$$F_{\rm conv} \propto (Q/\gamma)^{1/2} (1/H_{\rm P})^2 \rho C_{\rm V} c_{\rm s} T S^{3/2}$$
(XI.18)
where Q is the isobaric coefficient of thermal expansion, $-(d \ln \rho/d \ln T)_P$ , $\gamma$ is the ratio of specific heats, $H_P$ is the pressure scale h... | {
"Header 1": "Chemical and Physical Prerequisites of Life",
"token_count": 2030,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The theoretical complexities surrounding the origin of other planetary systems, the nature and evolution of the bodies in them, and the possible origin and evolution of life on their planets can be minimized by observing other planetary systems directly. It is important to realize that we are just now developing severa... | {
"Header 1": "The Search for Planets of Other Stars",
"token_count": 2047,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Inclination, either with respect to the line of sight from Earth or relative to the rotational equator of the parent star, is generally unknown.
temperature of only 103 K. Assuming a similar albedo for Jupiter and the planet, the effective temperature of $\tau$ Boo A would be roughly $103(1.1\times10^5)^{1/4}=1875... | {
"Header 1": "The Search for Planets of Other Stars",
"token_count": 2037,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
These planets may be either the surviving cores of extinct close Jovian planets, or postcataclysmic stellar debris condensed and accreted in a disk surrounding the dying star.
Detection of Earth by reflected solar radiation is very challenging over interstellar distances because of the nearly 10<sup>9</sup> :1 intens... | {
"Header 1": "The Search for Planets of Other Stars",
"token_count": 701,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
After decades of fiscal starvation and extraordinary technological progress, plans to search for radiofrequency emissions from other intelligent species in our galaxy have finally begun to bear fruit. Large radio telescopes are now being employed in a search for nonrandom radio emission from many nearby stars under the... | {
"Header 1": "The Search for Extraterrestrial Intelligence",
"token_count": 1487,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Now that we have surveyed the Solar System and explored a wide variety of theoretical explanations of the phenomena we have encountered, it is useful to look forward to the prospects for answering the great questions we now have about the origin, evolution, composition, and structure of planetary systems. The observati... | {
"Header 1": "XII. Future Prospects",
"token_count": 2042,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Mercury, having been visited by only a single flyby mission, poses a vast array of interesting questions. The composition of the surface and the bulk composition of the interior are potentially diagnostic clues to the mode of origin of the planet and the reason for its very high metal content. A highly refractory-rich ... | {
"Header 1": "Mercury",
"token_count": 807,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Many features of the atmospheric composition of Venus, such as the detailed elemental and isotopic composition of the noble gases, the reported dramatic variations in the sulfur dioxide abundance, and the hydrogen chemistry of the lower atmosphere, require further study. The implications of some (water-rich) atmospheri... | {
"Header 1": "Venus",
"token_count": 453,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
So much time has elapsed since the end of the Apollo era that it is hard to believe that we still have many fundamental unanswered questions about the Moon—and that many of these are the same questions we had in the mid-1970s. Indeed, since 1972 we have seen only four spacecraft investigations of the Moon: the launch o... | {
"Header 1": "Earth's Moon",
"token_count": 837,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The broad success of the Viking program provided us with many useful insights into Mars and has whetted our appetite for information about the early history of the planet. Study of the chemical weathering and volatiletransport processes at work today may help greatly in understanding the evolution of surface conditions... | {
"Header 1": "Mars",
"token_count": 1018,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Despite our vast wealth of data on meteorites, our ability to link these familiar objects to particular asteroids is still limited by the small number of spacecraft encounters with asteroids. Asteroids with especially distinctive reflection spectra can be confidently identified with particular meteorite classes, but ma... | {
"Header 1": "Asteroids",
"token_count": 946,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The Jovian system is nearly as complex as the Solar System itself. The meteorology of the giant planets, their atmospheric chemistry, the geological evolution of their satellites, the formation and evolution of their ring systems, their immense and dynamically complex magnetospheres, the dynamics of capture and loss of... | {
"Header 1": "Jupiter",
"token_count": 398,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Pluto, the planet with the greatest mean distance from the Sun, is the only planet in the Solar System not yet visited by a spacecraft from Earth. At the time of the planning of the Grand Tour missions to the outer Solar System in the early 1970s, it was originally proposed that a pair of spacecraft should be sent to f... | {
"Header 1": "Pluto",
"token_count": 420,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The United States, conspicuous by its absence among the armada of spacecraft launched from Earth to study Halley's Comet, consoled itself by renaming the alreadyold International Sun-Earth Explorer (ISEE; changed to International Cometary Explorer, ICE) and diverting it from its station near Earth's inner Lagrange poin... | {
"Header 1": "Comets",
"token_count": 741,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The search for planets about other stars has already been begun on the ground, as we saw in Chapter XI. Nonetheless, many contributions to this search program can and will be made by space-based interferometry and astrometry. High-precision photometry to search for planets via their partial eclipses of the disks of the... | {
"Header 1": "Beyond the Solar System",
"token_count": 2027,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
On this acceleration-vs-time plot, lines of constant speed have a slope of 1 and lines of constant distance have a slope of 2. Several realms of spatial exploration are indicated, including low Earth orbit, the Moon, the near-Earth asteroids, the planets, the comets, and the stars. The diagram is truncated at the top b... | {
"Header 1": "Beyond the Solar System",
"token_count": 723,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Energy, heat, and work are all aspects of energy. Let us begin by defining E as the total internal energy of a system, the sum of the system's kinetic and potential energies. We may choose any of a number of possible reference states for the zero of the energy scale: we will avoid this problem by dealing solely with en... | {
"Header 1": "Heat and Work",
"token_count": 1495,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
We define an adiabatic process as one in which no heat enters or leaves the system: q = 0. Therefore $w = -\Delta E$ and, if P - v work is done at the expense of the internal energy,
$$Pdv = -dE. (AI.20)$$
But we know that $(\partial E/\partial T)_v = C_v$ , and thus $dE = C_v$ dT = -Pdv. By the ideal gas law, ... | {
"Header 1": "Adiabatic Processes and Entropy",
"token_count": 2015,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
\tag{AI.43}$$
For any pure gaseous element in the reference state, $\Delta G = RT \ln P$ , or for any pure gas at 1 atm pressure, $\Delta G = \Delta G^{\circ}$ . We can now write any general gas-phase reaction as $aA + bB + cC + \cdots = mM + nN + \cdots$ , where a is the number of moles of substance A in the bala... | {
"Header 1": "Adiabatic Processes and Entropy",
"token_count": 820,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Let us suppose that a state function of form z = z(x, y) describes the behavior of a system. If the equations
$$dz = Mdx + Ndy (AI.48)$$
and
$$(\partial M/\partial y)_{x} = (\partial N/\partial x)_{y}$$
(AI.49)
are obeyed, where M = M(x, y) and N = N(x, y), then the expression (AI.48) is called an *exact* diffe... | {
"Header 1": "Adiabatic Processes and Entropy",
"Header 2": "**Exact and Complete Differentials**",
"token_count": 370,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
However, the energy E, the enthalpy H, and the Gibbs and Helmholtzfree energies (G and A, respectively) are state functions and can be expressed completely in terms of complementary intensive and extensive variables such as P, T, V, and S. The differentials of all four of these energy functions are exact differentials;... | {
"Header 1": "The Maxwell Relations",
"token_count": 296,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Consider an oscillator with quantized energy levels $E_n = nh\nu$ , where $n = 0, 1, 2, ..., \infty$ . The probability that the oscillator has an energy $E_n$ is proportional to $\exp(-E_n/kT)$ , the so-called Boltzmann factor. The average energy of the oscillator is the weighted sum of all the possible contributi... | {
"Header 1": "Appendix II Absorption and Emission of Radiation by Quantum Oscillators",
"token_count": 1975,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
\tag{AII.22}$$
The uncertainty in the lifetime of the state is of the same magnitude as the lifetime itself, and we can approximate the uncertainty in the energy of the state by
$$\Delta E \Delta t \ge h/2\pi$$
(AII.23)
$$\Delta E \ge (4\pi he^2 \nu^2)/(3m_e c^3).$$
(AII.24)
Thus we have derived a measure of th... | {
"Header 1": "Appendix II Absorption and Emission of Radiation by Quantum Oscillators",
"token_count": 260,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The first attempts to launch lunar and planetary probes date back to 1958, only a year after the launching of the first artificial Earth satellite, Sputnik 1, by the Soviet Union.At that time, the Soviet Union had a very large booster, known to them as the R-7 ''Semyorka,'' derived from their first-generation intercont... | {
"Header 1": "Appendix III Exploration of the Solar System",
"token_count": 995,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Table AIII.1 Exploration of the Solar System: Spacecraft Launchings
| Spacecraft1 | Source | Launch2 | Target | Mission | Vehicle3 | Remarks |
|-------------|--------|-----------|--------|---------|----------|----------------------------------------|
| Pioneer 1 | USA | 11 Oct ... | {
"Header 1": "Appendix III Exploration of the Solar System",
"token_count": 7277,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
<sup>2</sup>Launch Sites: All USA lunar and planetary probes are launched from Kennedy Space Center, Cape Canaveral, Florida.All Soviet lunar and planetary probes are launched from ''Baikonur Cosmodrome,'' which is near Tyuratam, Kazakhstan, not near Baikonur.Japanese deep space missions are launched from Kagoshima.T... | {
"Header 1": "Appendix III Exploration of the Solar System",
"token_count": 364,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
For a central inverse-square gravity field, the gravitational force is
$$F = GMm/r^2 (AV.1)$$
and the gravitational potential energy is
$$U = -GMm/r. (AV.2)$$
The potential energy per unit mass, V, also called the potential, is merely
$$V = -GM/r. (AV.3)$$
The surface of any reasonably fluid planet is isost... | {
"Header 1": "Appendix V Gravity Fields",
"token_count": 1418,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Dozens of descriptive introductory astronomy texts with little mathematical content are available to provide a general, qualitative overview of the astronomical context of the Solar System. Such books meet the needs of readers craving a rich descriptive overview and willing to get their mathematics elsewhere. Because t... | {
"Header 1": "Chapter II—Astronomical Perspective",
"token_count": 401,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
For a broad qualitative introduction to the Solar System, the general astronomy books listed above are all adequate, although I confess a preference for the book by Hartmann and Impey. There are several texts dealing exclusively with the Solar System, of which the most familiar are Exploration of the Solar System, by W... | {
"Header 1": "Chapter III—General Description of the Solar System",
"token_count": 367,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The nature of the Sun is thoroughly explored in Solar Interior andAtmosphere, edited by A. N. Cox, W. C. Livingston, and M. S. Matthews (University of Arizona, 1991). The origin, evolution, and fate of the solar nebula is discussed extensively in The Origin of the Solar System, edited by S. F. Dermott (Wiley, 1978). Fo... | {
"Header 1": "Chapter IV—The Sun and the Solar Nebula",
"token_count": 410,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The large University of Arizona Space Science Series volumes Jupiter (edited by Tom Gehrels, 1976), Saturn (edited by Tom Gehrels and Mildred S. Matthews, 1984), Uranus (edited by Jay T. Bergstralh, Ellis D. Miner, and Mildred S. Matthews, 1991) and Neptune andTristan (edited by D. P. Quickshank, 1996) are the best col... | {
"Header 1": "Chapter V—The Major Planets",
"token_count": 794,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The most important general background source is Comets, edited by Laurel L. Wilkening (University of Arizona, 1982). A special issue in Icarus, Vol. 47, No. 3 (1981), also provides a broad prespacecraft view of comets. The physics of evaporation, coma formation, photodissociation and ionization, and tail formation is s... | {
"Header 1": "Chapter VII—Comets and Meteors",
"token_count": 430,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The principal treatises on meteorites are Meteorites, by Brian Mason (Wiley, 1962); Meteorites, by John T. Wasson (Springer-Verlag, 1974); and Meteorites: A Petrologic–Chemical Synthesis, by Robert T. Dodd (Cambridge, 1981). Mason's treatment is very broad and balanced but seriously out of date. Wasson's book is especi... | {
"Header 1": "Chapter VIII—Meteorites and Asteroids",
"token_count": 717,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The most important sources dealing with the terrestrial planets are Venus, edited by Donald M. Hunten, Larry Colin, Thomas M. Donahue, and V. I. Moroz (University of Arizona, 1983), Venus II, edited by S. W. Bougher, D. M. Hunten, and R. J. Phillipps (University of Arizona, 1998); and Mars, edited by Hugh H. Kieffer, B... | {
"Header 1": "Chapter X—The Terrestrial Planets: Mars, Venus, and Earth",
"token_count": 1738,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Cosmology is the study of the universe, or cosmos, regarded as a whole. Attempting to cover the study of the entire universe in a single volume may seem like a megalomaniac's dream. The universe, after all, is richly textured, with structures on a vast range of scales; planets orbit stars, stars are collected into gala... | {
"Header 1": "Introduction",
"token_count": 1590,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
Combining the Newtonian gravitational constant, $G = 6.7 \times 10^{-11} \,\mathrm{m^3\,kg^{-1}\,s^{-2}}$ , the speed of light, $c = 3.0 \times 10^8 \,\mathrm{m\,s^{-1}}$ , and the reduced Planck constant, $\hbar = h/(2\pi) = 1.1 \times 10^{-34} \,\mathrm{J\,s} = 6.6 \times 10^{-16} \,\mathrm{eV\,s}$ , yields a uniq... | {
"Header 1": "Introduction",
"token_count": 1502,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
Step outside on a clear, moonless night, far from city lights, and look upward. You will see a dark sky, with roughly two thousand stars scattered across it. The fact that the night sky is dark at visible wavelengths, instead of being uniformly bright with starlight, is known as Olbers' Paradox, after the astronomer He... | {
"Header 1": "Fundamental Observations",
"Header 2": "2.1 The night sky is dark",
"token_count": 1854,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
What does it mean to state that the universe is isotropic and homogeneous? Saying that the universe is isotropic means that there are no preferred directions in the universe; it looks the same no matter which way you point your telescope. Saying that the universe is homogeneous means that there are no preferred locatio... | {
"Header 1": "Fundamental Observations",
"Header 2": "2.2 On large scales, the universe is isotropic and homogeneous",
"token_count": 1758,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
When we look at a galaxy at visible wavelengths, we are primarily detecting the light from the stars which the galaxy contains. Thus, when we take a galaxy's spectrum at visible wavelengths, it typically contains absorption lines created in the stars' relatively cool upper atmospheres.<sup>3</sup> Suppose we consider a... | {
"Header 1": "Fundamental Observations",
"Header 2": "2.3 Galaxies show a redshift proportional to their distance",
"token_count": 1981,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
For $H_0 = 70 \pm 7 \,\mathrm{km}\,\mathrm{s}^{-1}\,\mathrm{Mpc}^{-1}$ , the Hubble time is $H_0^{-1} = 14.0 \pm 1.4\,\mathrm{Gyr}$ . If the relative velocities of galaxies have been constant in the past, then one Hubble time ago, all the galaxies in the universe were crammed together into a small volume. Thus, the o... | {
"Header 1": "Fundamental Observations",
"Header 2": "2.3 Galaxies show a redshift proportional to their distance",
"token_count": 1933,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
It doesn't take a brilliant observer to confirm that the universe contains a large variety of different things: ships, shoes, sealing wax, cabbages, kings, galaxies, and what have you. From a cosmologist's viewpoint, though, cabbages and kings are nearly indistinguishable – the main difference between them is that the ... | {
"Header 1": "Fundamental Observations",
"Header 2": "2.4 The universe contains different types of particles",
"token_count": 2040,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
When a system is in thermal equilibrium, the density of photons in the system, as a function of photon energy, depends only on the temperature T. It doesn't matter whether the system is a tungsten filament, or an ingot of steel, or a sphere of ionized hydrogen and helium. The energy density of photons in the frequency ... | {
"Header 1": "Fundamental Observations",
"Header 2": "2.4 The universe contains different types of particles",
"token_count": 1268,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
The discovery of the Cosmic Microwave Background (CMB) by Arno Penzias and Robert Wilson in 1965 has entered cosmological folklore. Using a microwave antenna at Bell Labs, they found an isotropic background of microwave radiation. More recently, the Cosmic Background Explorer (COBE) satellite has revealed that the Cosm... | {
"Header 1": "Fundamental Observations",
"Header 2": "2.5 The universe is filled with a Cosmic Microwave Background",
"token_count": 1543,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
(2.1) Suppose that in Sherwood Forest, the average radius of a tree is R = 1 m and the average number of trees per unit area is Σ = 0.005 m<sup>−</sup><sup>2</sup> . If Robin Hood shoots an arrow in a random direction, how far, on average, will it travel before it strikes a tree?
or
- (2.2) Suppose you are in an in... | {
"Header 1": "Fundamental Observations",
"Header 2": "Problems",
"token_count": 847,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
On cosmological scales (that is, on scales greater than 100 Mpc or so), the dominant force determining the evolution of the universe is gravity. The weak and strong nuclear forces are short-range forces; the weak force is effective only on scales of `<sup>w</sup> <sup>∼</sup> <sup>10</sup><sup>−</sup><sup>18</sup> <sup... | {
"Header 1": "Newton Versus Einstein",
"token_count": 561,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
In Newton's view of the universe, space is unchanging and Euclidean. In Euclidean, or "flat", space, all the axioms and theorems of plane geometry (as codified by Euclid in the third century BC) hold true. In Euclidean space, the shortest distance between two points is a straight line, the angles at the vertices of a t... | {
"Header 1": "Newton Versus Einstein",
"Header 2": "3.1 Equivalence principle",
"token_count": 2026,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
The Way of Newton:
Mass tells gravity how to exert a force (F = −GMm/r<sup>2</sup> ), Force tells mass how to accelerate (F = ma).
The Way of Einstein:
Mass-energy tells space-time how to curve, Curved space-time tells mass-energy how to move. <sup>4</sup>
Einstein's description of gravity gives a natural exp... | {
"Header 1": "Newton Versus Einstein",
"Header 2": "3.1 Equivalence principle",
"token_count": 321,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
In developing a mathematical theory of general relativity, in which spacetime curvature is related to the mass-energy density, Einstein needed a way of mathematically describing curvature. Since picturing the curvature of a four-dimensional space-time is, to say the least, difficult, let's start by considering ways of ... | {
"Header 1": "Newton Versus Einstein",
"Header 2": "3.2 Describing curvature",
"token_count": 2044,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
By traveling a distance C = 2πR, it is possible to "circumnavigate" a space of uniform positive curvature.
<sup>8</sup>You can test this assertion, if you like, by drawing triangles on a bagel.
Finally, if a three-dimensional space has uniform negative curvature (κ = −1), its metric is
$$ds^{2} = dr^{2} + R^{2} \... | {
"Header 1": "Newton Versus Einstein",
"Header 2": "3.2 Describing curvature",
"token_count": 586,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
So far, we've only considered the metrics for simple two-dimensional and three-dimensional spaces. However, relativity teaches us that space and time together comprise a four-dimensional space-time. Just as we can compute the distance between two points in space using the appropriate metric for that space, so we can co... | {
"Header 1": "Newton Versus Einstein",
"Header 2": "3.3 The Robertson-Walker metric",
"token_count": 1468,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
Consider a galaxy which is far away from us – sufficiently far away that we may ignore the small scale perturbations of space-time and adopt the Robertson-Walker metric. One question we may ask is, "Exactly how far away is this galaxy?" In an expanding universe, the distance between two objects is increasing with time.... | {
"Header 1": "Newton Versus Einstein",
"Header 2": "3.4 Proper distance",
"token_count": 2045,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
\tag{3.43}$$
<sup>9</sup> In a homogeneous, isotropic universe there's no reason for the light to swerve to one side or the other.
That is, the integral of dt/a(t) between the emission of successive wave crests is equal to the integral of dt/a(t) between the observation of successive wave crests. This relation beco... | {
"Header 1": "Newton Versus Einstein",
"Header 2": "3.4 Proper distance",
"token_count": 726,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
- (3.1) What evidence can you provide to support the assertion that the universe is electrically neutral on large scales?
- (3.2) Suppose you are a two-dimensional being, living on the surface of a sphere with radius R. An object of width ds ¿ R is at a distance r from you (remember, all distances are measured on the s... | {
"Header 1": "Newton Versus Einstein",
"Header 2": "Problems",
"token_count": 419,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
In a universe which is homogeneous and isotropic, but which is allowed to expand or contract with time, everything you need to know about the curvature is given by κ, R0, and a(t). The curvature constant κ gives the sign of the curvature: positive (κ = +1), negative (κ = −1), or flat (κ = 0). If κ is non-zero, then R<s... | {
"Header 1": "Cosmic Dynamics",
"token_count": 990,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
Although 19th century mathematicians and physicists, such as Lobachevski, were able to conceive of curved space, it wasn't until Albert Einstein first published his theory of general relativity in 1915 that the curvature of spacetime was linked to its mass-energy content. The key equation of general relativity is Einst... | {
"Header 1": "Cosmic Dynamics",
"Header 2": "4.1 The Friedmann equation",
"token_count": 2026,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
We divide up the region outside the sphere into concentric shells, and thus conclude that the test mass m at R<sup>s</sup> experiences no net acceleration from matter at R > Rs. Unfortunately, a Newtonian argument of this sort assumes that space is Euclidean. A derivation of the correct Friedmann equation, including th... | {
"Header 1": "Cosmic Dynamics",
"Header 2": "4.1 The Friedmann equation",
"token_count": 1972,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
Since we know the current value of the Hubble parameter to within 10%, we can compute the current value of the critical density to within 20%:
$$\varepsilon_{c,0} = \frac{3c^2}{8\pi G} H_0^2 = (8.3 \pm 1.7) \times 10^{-10} \,\mathrm{J}\,\mathrm{m}^{-3} = 5200 \pm 1000 \,\mathrm{MeV}\,\mathrm{m}^{-3} \,.$$
(4.26)
Th... | {
"Header 1": "Cosmic Dynamics",
"Header 2": "4.1 The Friedmann equation",
"token_count": 1997,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
\tag{4.40}$$
Taking the time derivative yields
$$2\dot{a}\ddot{a} = \frac{8\pi G}{3c^2}(\dot{\varepsilon}a^2 + 2\varepsilon a\dot{a}) \ . \tag{4.41}$$
Dividing by 2aa˙ tells us
$$\frac{\ddot{a}}{a} = \frac{4\pi G}{3c^2} \left( \dot{\varepsilon} \frac{a}{\dot{a}} + 2\varepsilon \right) . \tag{4.42}$$
Using the... | {
"Header 1": "Cosmic Dynamics",
"Header 2": "4.1 The Friedmann equation",
"token_count": 2018,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
Sound waves cannot travel faster than the speed of light; if they did, you would be able to send a sound signal into the past, and violate causality. Thus, w is restricted to values $w \le 1$ .
$<sup>^8</sup>$ In a substance with w < 0, the sound speed is an imaginary number; this implies that small pressure perturb... | {
"Header 1": "Cosmic Dynamics",
"Header 2": "4.1 The Friedmann equation",
"token_count": 2019,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
If a˙ = 0, the Friedmann equation (4.62) reduces to
$$0 = \frac{8\pi G}{3}\rho - \frac{\kappa c^2}{R_0^2} + \frac{\Lambda}{3} = 4\pi G\rho - \frac{\kappa c^2}{R_0^2} . \tag{4.68}$$
Einstein's static model therefore had to be positively curved (κ = +1), with a radius of curvature
$$R_0 = \frac{c}{2(\pi G\rho)^{1/2... | {
"Header 1": "Cosmic Dynamics",
"Header 2": "4.1 The Friedmann equation",
"token_count": 1595,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
- (4.1) Suppose the energy density of the cosmological constant is equal to the present critical density ε<sup>Λ</sup> = εc,<sup>0</sup> = 5200 MeV m<sup>−</sup><sup>3</sup> . What is the total energy of the cosmological constant within a sphere 1 AU in radius? What is the rest energy of the Sun (E¯ = M¯c 2 )? Comparin... | {
"Header 1": "Cosmic Dynamics",
"Header 2": "Problems",
"token_count": 753,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
In a spatially homogeneous and isotropic universe, the relation among the energy density ε(t), the pressure P(t), and the scale factor a(t) is given by the Friedmann equation,
$$\left(\frac{\dot{a}}{a}\right)^2 = \frac{8\pi G}{3c^2}\varepsilon - \frac{\kappa c^2}{R_0^2 a^2} , \qquad (5.1)$$
the fluid equation,
$$... | {
"Header 1": "Single-Component Universes",
"token_count": 221,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Ryden_IntroCosmo.pdf"
} |
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