Fundamental Physics Book

[Amatista Sheeley]

Formillennia we believed that Earth and the heavens were subject to different laws, a view still implicit in our distinction between physics (describing the world around us) and astronomy (describing the rest of the Universe). The Newtonian revolution showed that a broad range of phenomena in both terrestrial and celestial realms can be described by a single and unchanging set of laws. Modern astrophysics has turned this into a question that can be answered experimentally.

Our current definition of a fundamental constant of nature is any quantity whose value cannot be calculated using a given physical theory but can only be determined experimentally. Examples include the fine-structure constant (a measure of the behaviour of the electromagnetic interaction) and the proton-to-electron mass ratio (a measure of the interplay between the strong and electroweak forces). If we assume that the laws of nature have always been the same everywhere in the Universe, then these fundamental constants must really be constants. But if this assumption does not hold, then they may vary with the epoch and location of any specific measurement.

The ELT will build upon and improve ongoing searches for possible variations in the fundamental physical constants across space and time. An unambiguous detection of such variations would show that the laws of nature cannot be universal. These variations could also have a profound impact on the physical properties of the Universe and its ability to host life; for example, if the value of the fine-structure constant was just 4% larger in the early Universe, the existence of carbon-based life would be impossible.

Astronomical observations can probe much longer timescales than Earth-based laboratory experiments and are therefore much more sensitive to possible variations in the fundamental constants. By exploring the spectra of extremely bright distant quasars, for example, the variability can be probed over a large fraction of the history of the Universe. However, making these observations is very challenging. It involves measuring the relative wavelength shifts of pairs of absorption lines whose wavelengths have different sensitivity to the fundamental constants. These sensitivities are often subtle, meaning that the wavelength calibration must be extremely accurate.

The ANDES ultra-stable high-resolution spectrograph proposed for the ELT will essentially remove the wavelength calibration uncertainties that plague current measurements and will vastly improve the constraints on the stability of fundamental constants. Astronomers will therefore be able to use the ELT to confirm or disprove claims that fundamental constants might vary and that we could simply be living in a fine-tuned location of spacetime where the constants are conveniently suitable for life.

The most natural theoretical explanation for the variability of fundamental constants is due to a scalar field that is coupled to the electromagnetic field. The Higgs boson discovered at CERN in 2012 is the first known example of a scalar field in nature, but it is not believed to play any direct role in cosmology. Nevertheless, further scalar fields are ubiquitous in fundamental physics scenarios. For example, the variability of fundamental constants is unavoidable in string theory, due to the changing size of hidden spacetime dimensions. Unfortunately, string theory cannot accurately predict the amount of this variation, which makes the ELT tests all the more compelling.

Any improved test of the stability of these fundamental constants (whether it's a detection of a variation or a null result) will shed additional light on the allowed unified theories of the fundamental interactions, on the existence of extra dimensions of spacetime, and on the possible roles of large-scale scalar fields acting in the late Universe. One of these roles is the source of the dark energy, which is currently causing the expansion of the Universe to accelerate.

Insights from fundamental physics have overturned our assumptions about the world around us. Last century, general relativity reshaped our picture of space and time, and quantum mechanics replaced the march of cause and effect with a dance of probabilities. Just in the last few decades, we have detected the Higgs boson and gravitational waves, and discovered that the expansion of the Universe is accelerating.

Physicists believe that everything in the universe is made from a few basic building blocks called fundamental particles, whose interactions are governed by four fundamental forces. The Standard Model captures our present understanding of how these particles and the electromagnetic, weak nuclear, and strong nuclear forces are related. The Standard Model is the best current description of the subatomic world, but it remains an incomplete picture of the universe. It does not include the force of gravity and offers no explanation for dark matter or dark energy, among other phenomena.

Recently, advances in the high precision measurement of wave interference, electromagnetic properties, and quantum mechanical effects have enabled additional innovative concepts in the search for new physics. These ideas include experiments to search for new forces, tests of general relativity, gravitational wave detection, and searches for violations of symmetry.

The Center presently consists of 12 full-time faculty members in the Department of Physics, working on the wide range of theoretical problems related to the fundamental aspects of physics. Other members include Professor Emeriti, postdocs, graduate students, and visitors.

The Fundamental Physics Directorate brings together scientists and technologies that support national priorities in particle physics, astrophysics and cosmology to explore the basic particles and forces that knit the cosmos together.

The current version is a revised version of the original 1960 textbook Physics for Students of Science and Engineering by Halliday and Resnick, which was published in two parts (Part I containing Chapters 1-25 and covering mechanics and thermodynamics; Part II containing Chapters 26-48 and covering electromagnetism, optics, and introducing quantum physics). A 1966 revision of the first edition of Part I changed the title of the textbook to Physics.[1]

It is widely used in colleges as part of the undergraduate physics courses, and has been well known to science and engineering students for decades as "the gold standard" of freshman-level physics texts. In 2002, the American Physical Society named the work the most outstanding introductory physics text of the 20th century.

The first edition of the book to bear the title Fundamentals of Physics, first published in 1970, was revised from the original text by Farrell Edwards and John J. Merrill.[2] (Editions for sale outside the USA have the title Principles of Physics.) Walker has been the revising author since 1990.[3]In the more recent editions of the textbook, beginning with the fifth edition,[4] Walker has included "checkpoint" questions. These are conceptual ranking-task questions that help the student before embarking on numerical calculations.

The extended edition also contains introductions to topics such as quantum mechanics, atomic theory, solid-state physics, nuclear physics and cosmology. A solutions manual and a study guide are also available.[5]

The present article is sincere, though it might come across as absurd depending on one's perspective. I write it in the spirit of exploring new ideas rather than because I'm committed to the line of reasoning I advance.

In order to reduce suffering, we have to decide which things can suffer and how much. Suffering by humans and animals tugs our heartstrings and is morally urgent, but we also have an obligation to make sure that we're not overlooking negative subjective experiences in other places. I've written elsewhere about suffering in insects and digital minds. This piece explores what is arguably the most extreme possibility: seeing at least traces of suffering in fundamental physics.

I've defended a kind of computational panpsychism in which every physical system can be thought of as having its own kind of consciousness, even if it's too simple or too alien for us to possibly imagine. Another essay on whether video-game characters have moral significance elaborates on more particular ways in which we can see sentience-like operations in very simple systems. It mentions that we could potentially apply Daniel Dennett's intentional stance to some "dumb" physical systems like electrons orbiting atoms or a washer tied to a string. It further notes how we can see some empathy-inducing similarities between us and all of physics.

Operations by fundamental physics are the most numerous things in the universe. (Of course, this claim depends on how we define "things".) Hence, even if we value them only an extremely tiny bit, they may collectively dominate in our valuations.

The observable universe contains roughly 1080 hydrogen atoms. Contrast this with 1030 bacteria, 1019 insects, and 1010 humans on Earth. If a hydrogen atom has even 10-70 times as much sentience as a person, then there's more total hydrogen suffering in the observable universe than human suffering. (This comparison might need some adjustment depending on the specific computational state of the humans and protons. For instance, a human in great pain would count orders of magnitude more than a human with just an itch.)

And each hydrogen atom contains its own little world. A hydrogen atom has a diameter on the order of 10-10 meters, while the Planck length, "the limit below which the very notions of space and length cease to exist", is on the order of 10-35 meters. This is really small:

Superstring theory proposes that the fundamental particles of physics, vibrating strings, are on the order of the Planck length in size. Some suggest that spacetime may be discrete, with "pixels" roughly the size of the Planck length.

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