This chapter explores observations and properties of quasars, which were first observed in the 1960s as point-like sources that emit over a wide range of energies from the radio through the IR, visible, UV, and even extending to the X-ray and gamma-rays. They are now known to be a type of active galactic nucleus thought to be the result of matter accreting onto a supermassive black hole (SMBH) at the center of the host galaxy.

Congress is the centerpiece institution of Madison’s Republic. Article I of the Constitution starts with Congress, enumerating an impressive list of specific powers given to government because they are vested in the national legislature. And, if we have a republic, it is because the Congress somehow represents the national interest. It does this, as the above quote from Federalist 10 suggests, by bringing into government the range of interests in society. This is necessarily a messy business. The “necessary and ordinary operations of government” involve the range of factions in society? No wonder there is so much conflict, noise, frustration, posturing, and gridlock in Washington. Congressional politics, in other words, is untidy by design.

Earth’s Moon is quite distinct from other moons in the solar system, in being a comparable size to Earth. We explore the theory that a giant impact in the chaotic early solar system led to the Moon’s formation, and bombardment by ice-laden asteroids provided the abundant water we find on our planet. Further, we find that Earth’s magnetic field shields us from solar wind protons, that protect our atmosphere from being stripped away. The icy moons of Jupiter and Saturn are the best targets for exploring if life exists elsewhere in the solar system.

In our everyday experience, there is another way we sometimes infer distance, namely by the change in apparent brightness for objects that emit their own light, with some known power or luminosity. For example, a hundred watt light bulb at close distance appears a lot brighter than the same bulb from far away. Similarly, for a star, what we observe as apparent brightness is really a measure of the flux of light, i.e. energy emitted per unit time per unit area.

For James Madison, self-interest is the problem. It is the problem because it is an immutable part of human nature and because its consequences in politics are potentially devastating. People act for their own gain without thinking of the interests of others, or of the larger public good. Although everyone benefits in the long run from a stable social order, people may pursue their short-run interests in ways that harm or even destroy that order. This consequence of self-interest – social instability and chaos – is relatively easily managed. The problem is complicated because the governments created to protect against instability and disorder are themselves subject to self-interest. This problem is the possibility of tyranny. The people with power naturally use it to pursue their own interests, without concern for the interests of others or for the larger public good. Those with power often have a compelling interest in avoiding instability and chaos, but stability is not enough. Great care must be taken to avoid tyranny – by a majority over the minority, or by the government over the governed.

It turns out that stellar binary (and even triple and quadruple) systems are quite common. In Chapter 10 we show how we can infer the masses of stars, through the study of stellar binary systems. For some systems, where the inclination of orbits can be determined unambiguously, we can infer the masses of the stellar components, as well as the distance to the system. Together with the observed apparent magnitudes, this also gives the associated luminosities of their component stars.

In reality., stars are not perfect blackbodies, and so their emitted spectra don’t depend solely on temperature, but instead contain detailed signatures of key physical properties like elemental composition. For atoms in a gas, the ability to absorb, scatter, and emit light can likewise depend on the wavelength, sometimes quite sharply. We find that the discrete energies levels associated with atoms of different elements are quite distinct. We introduce the stellar spectral classes (OBAFGKM).

This book critically examines the following claim: Self-interest is the problem; it is also the only possible solution. The problem with what? The solution to what? This is a book about American government and politics, and both the problem and the solution are concerned with how best to conduct our politics. The title to this introduction states a paradox: The thing that causes the predicament – self-interest – also gets us out of it. To put it more precisely (and optimistically): All that is required in a well-ordered political system for the public good to be achieved is for everyone – politicians, citizens, leaders of special interest groups – to pursue their own selfish interests. The political system does not require anyone to set aside his or her interests in the name of the public good for that good to be achieved. We describe in detail the source of this claim in Chapter 2 and devote the rest of the book to some critical questions about whether the claim that self-interest is sufficient to resolve the problems it creates in politics fits with the reality of American politics today.