On the Origin of Time: The instant Sunday Times bestseller

Product Information

In the first chapter, Hawking discusses the history of astronomical studies, particularly ancient Greek philosopher Aristotle's conclusions about spherical Earth and a circular geocentric model of the Universe, later elaborated upon by the second-century Greek astronomer Ptolemy. Hawking then depicts the rejection of the Aristotelian and Ptolemaic model and the gradual development of the currently accepted heliocentric model of the Solar System in the 16th, 17th, and 18th centuries, first proposed by the Polish priest Nicholas Copernicus in 1514, validated a century later by Italian scientist Galileo Galilei and German scientist Johannes Kepler (who proposed an elliptical orbit model instead of a circular one), and further supported mathematically by English scientist Isaac Newton in his 1687 book on gravity, Principia Mathematica. Our entire cosmic history is theoretically well-understood, but only qualitatively. It's by ... [+] observationally confirming and revealing various stages in our Universe's past that must have occurred, like when the first stars and galaxies formed, and how the Universe expanded over time, that we can truly come to understand our cosmos. The relic signatures imprinted on our Universe from an inflationary state before the hot Big Bang give us a unique way to test our cosmic history. Nicole Rager Fuller / National Science Foundation In particular, the patterns and magnitudes of the fluctuations that we've discovered in the modern radiation left over from that early, hot, dense state teach us a number of important properties about our Universe. They teach us how much matter was present in dark matter as well as normal matter: protons, neutrons and electrons. They give us a measurement of the Universe's spatial curvature, as well as the presence of dark energy and the effects of neutrinos. Whenever we think about anything, we apply our very human logic to it. If we want to know where the Big Bang came from, we describe it in the best terms we can, and then theorize about what could have caused it and set it up. We look for evidence to help us understand the Big Bang's beginnings. After all, that's where everything comes from: from the process that gave it its start. For a time, there were multiple competing ideas which were all consistent with the observations we had.

Mass and energy are related by the famous equation E = m c 2 {\displaystyle E=mc In this chapter, Hawking describes the development of scientific thought regarding the nature of space and time. He first describes the Aristotelian idea that the naturally preferred state of a body is to be at rest, and which can only be moved by force, implying that heavier objects will fall faster. However, Italian scientist Galileo Galilei experimentally proved Aristotle's theory wrong with by observing the motion of objects of different weights and concluding that all objects would fall at the same rate. This eventually led to English scientist Isaac Newton's laws of motion and gravity. However, Newton's laws implied that there is no such thing as absolute state of rest or absolute space as believed by Aristotle: whether an object is 'at rest' or 'in motion' depends on the inertial frame of reference of the observer. This section may be too long and excessively detailed. Please consider summarizing the material. ( January 2022)

Select a format:

An expanding Universe could have originated from a singular point— an event in spacetime— where all of space and time emerged from a singularity. Singularities are where the law of gravitation governing the Universe — Einstein’s General Relativity —yields nonsense for predictions. Relativity, remember, is the theory that describes space and time. But at singularities, both spatial and temporal dimensions cease to exist. Asking questions like “what came before this event where time began” is as nonsensical as asking “where am I” if space no longer exists. According to the Big Bang, the Universe was hotter, denser, more uniform and smaller in the past. It only has the properties we see today because it’s been expanding, cooling, and experiencing the influence of gravitation for so long. Because the wavelength of radiation stretches as the Universe expands, a smaller Universe should have had radiation with shorter wavelengths, meaning it had higher energies and greater temperatures. Yifang Wang, Kam-Biu Luk and the Daya Bay team, Atsuto Suzuki and the KamLAND team, Kōichirō Nishikawa and the K2K / T2K team, Arthur B. McDonald and the Sudbury Neutrino Observatory team, Takaaki Kajita and Yōichirō Suzuki and the Super-Kamiokande team (2016)

This radiation wasn't just the same magnitude everywhere, but also the same in all directions. At just a few degrees above absolute zero, it was consistent with the Universe emerging from an earlier, hot dense state, and cooling as it expanded. Like many great discoveries in science, this leads to a slew of delightful new questions, including: Jeffrey M. Friedman, Franz-Ulrich Hartl, Arthur L. Horwich, David Julius, Virginia Man-Yee Lee (2020) International Union for Conservation of Nature and Natural Resources and World Wide Fund for Nature

Success!

Special: Stephen Hawking, Peter Jenni, Fabiola Gianotti (ATLAS), Michel Della Negra, Tejinder Virdee, Guido Tonelli, Joseph Incandela (CMS) and Lyn Evans (LHC) (2013)