[...]... variation in the brightness of different stars However, various tricks can be used that take advantage of observations of closer-in galaxies Spiral galaxies, so named because the stars trace out a distinctive spiral shape as they orbit a common center, are particularly important in this regard The more stars present, the more massive the galaxy, and the faster will be the rotation of stars around a. .. thousands of years, and the presence of the Moon in orbit about Earth apparently has prevented rather extreme swings in Earth s axial tilt, which could have led to very large climate instabilities in the past Far from being a quaint part of the traditional curriculum of science in schools, the arrangement of the Sun, Earth, Moon, and other planets is in fact critical to understanding the stability of, and... foci are coincident, and a circular orbit results immediately; the English mathematician and physicist Sir Isaac Newton decades later postulated the existence of an attractive force associated with the mass of an object, namely gravity Kepler formulated his laws solely to fit observations; this is an excellent example of an empirical model.) Given Kepler’s laws and knowledge of the distance of Earth. .. will interact to form atomic and molecular associations However, intuition has yet to catch up: one simply must imagine that, at smaller and smaller scales, the discrete nature of matter finally loses its meaning in a sea of wave packets interfering one with another Technology today is allowing us to see the wave–particle duality of nature Electrons can be manipulated to image individual atoms in a technique... travels in a single year, about 1013 km.) Beyond a few thousand light-years from Earth, parallax shifts are too small to be measured and other distance techniques must be used However, a satellite named Gaia to be launched in 2013 will measure distances so precisely that this scale may be extended out to tens of thousands of light years The parallax technique itself has led to common use of a unit of. .. material and varying amounts of gases; Jupiter and Saturn are mostly hydrogen and helium gas whereas Uranus and Neptune are predominantly icy and rocky material with lesser amounts of hydrogen and helium gas (Rocky and icy material is used here to mean atoms of silicon, magnesium, iron, oxygen, carbon, nitrogen, sulfur, and others that tend to form rocky and icy materials under conditions of normal... expansion of space itself has another important consequence, namely that while matter is constrained to move at a velocity less than that of light, the expansion of space is not The initial expansion of the cosmos must have included a very brief phase in which the scale of everything suddenly increased dramatically, called “inflation” (but not to be confused with the gradual inflation of our balloon analogous... into a planet because of the proximity of Jupiter, whose gravitational field prevented efficient growth of a large body from smaller ones Another collection of asteroids crosses the orbit of Earth – the socalled near -Earth asteroids, some of which may be old comets that have lost their mantles of ice after many passes by the Sun Finally, lanes and regions of dust released from comets or asteroids lace... bonding and sharing of electrons, the reader may be left with a significant degree of dissatisfaction How do electrons interact, and why do they preferentially move in certain patterns around atoms? To understand this requires that we free ourselves of the simple picture of elemental matter as particles The behavior of microscopic atomic and subatomic particles displays attributes that have no real analogue... the macroscopic world An electron is a wave pattern, partly localized in space and energy An electron around an atom will have a particular wave pattern or wavefunction, which is altered when another electron is introduced to complete the energy level Through the extraordinary insights that led to quantum mechanics, such wave patterns can be calculated mathematically to understand how electrons and . of what makes a planet capable of sustaining life, and whether inhabited planets exist in large numbers in the cosmos, was long a popular draw for courses in planetary science, geology, and astronomy that Earth must be spherical; in fact, another acceptable shape based on that one observation is a disk (Figure 1.1). Others, such as Plato, had much earlier endorsed a spherical shape on aesthetic. 12,700 km (Earth) . They occupy a small, inner region of the solar system, and are composed of a mixture of rocky and metallic materials. The four giant or Jovian planets Jupiter, Saturn, Uranus, and Neptune