The Universe

The following sections are included:

• Table of Contents

• Preface

It is important to understand clearly what we mean by such terms as science and scientific theory. Many articles have been written on that subject. We could write a whole chapter on the definition of science and consequent ramifications of a philosophical nature, such as the meaning of our existence; but we will examine it in a very practical way. We may say that science is the human activity that attempts to understand by means of natural explanations how the world we live in functions and that uses that knowledge to improve our existence in that world. That is sufficient for the purposes of this book. Science as it is understood here is based on the observation of phenomena taking place in the Universe we know and the development of theoretical models to describe their behaviour. And the Universe includes a piece of chalk as well as a faraway galaxy. There is no such thing as a science that is based on beliefs or on imagination alone. They may play a role in the development of a scientific theory but experimental facts dictate finally if the imagined concepts and beliefs are correct: a theory must absolutely be in agreement with experimental observations to have scientific value. One might have a dream and develop a theory about the occurrence of a phenomenon but if it does not agree with experimental measurements made of the characteristics of the phenomenon, the theory is not useful to science. It may be logical and attractive, but it remains an exercise in the abstract. To be right a scientific theory must be in agreement with experimental observations either made in the laboratory or with observations made in the Universe at large. In the first case, the scientist has general control on the phenomenon he is observing and measurements can be repeated at will, at different times and in different locations. In the second case, when the scientist has no control over the object observed — such as with celestial phenomena Ȕ present behaviour and prediction of the characteristics of future observations and their confirmation by means of measurements, play a vital role in establishing the validity of the theory developed…

The following sections are included:

• Our Universe

• The Very Large Scale

• The Small and Ultra Small Landscape

• The Framework of Our Understanding
  • Force of gravity
  • Electromagnetic interaction
  • Weak interaction
  • Strong interaction

The following sections are included:

• Worlds and Dimensions

• How do We Alter the Speed of an Object?

• What is so Special about the Speed of Light?

• Who is Moving?

• Joe and Mary are Confused about Time Flow

• Joe and Mary do not see Things Happening at the Same Time

• Mary Questions the Dimension of the Travelling Clock

• So the Speed of Light is Independent of the Source Motion!

• The Space-Time World we Live in

• Speed Limit on the Space-Time World Highway

• Mary's Car had Effectively a Built in Cruise Control

• Shadows of our Four Dimensional Space-Time

• We Stick to the Ground and Things Fall on the Floor

• We Cheated A Little about the Concept of Mass

• Acceleration, Gravity and Space Curvature
  • Gravitational redshift
  • Deviation of a light ray by gravity
  • Space-time curvature

• Deeper Thoughts and Relativistic Laws of Motion

• The Speed at which Space Curvature Propagates

• Is this Whole Thing Right?

The following sections are included:

• Energy It Has and Energy It Wants to Keep

• Don't Get in the Way: I Move and I have Momentum

• Energy, Heat, Power, Perpetual Motion and all that Stuff

• We are all Guilty of Vandalism

• The Skater Physicist and Angular Momentum

• Other Conservation Laws: How about Electric Charges?

• Reflections on Conservation of Energy and Entropy

• Conservation Laws and Symmetry

The following sections are included:

• Electricity

• Magnetism

• Motion of Electrons and Radio Waves

• A Bit of Atomic Physics

• How about the Origin of Light?

• So, How Much Do We See?

The following sections are included:

• A Baffling Experiment

• A Question of Matter and Wave

• Wave and Particle, is it Compatible?

• Wave Mechanics

• Another Fascinating Property of the Electron: The Spin

• One of the Most Basic Principles of that Magic Quantum World

• Fermions and Bosons

• The Elements and Mendeleev's Table

• The Quantum World Probability Concept

• Some Revealing Experiments

• Photons and Electrons Interact

• Where is the Electromagnetic Force Coming From?

• The Quantum World Contains Some Real Mysteries

• Usefulness of Quantum Physics: Understanding of the World and Its Use in Our Day-to-Day Activities
  • The electron microscope
  • Magnetic resonance imaging
  • The transistor
  • Superconductivity
  • The atomic clock
  • Entanglement, computers and secure communications
  • The laser
  • Cooling of atoms
  • Macroscopic quantum effects
  • How to make our measurements really reliable in our macroscopic world
  • Natural units

The following sections are included:

• The proton

• The neutron

• Radioactivity: A Source of Information

• Nuclear Forces

• A Word about Nucleus Stability and the Neutrino

• A Global Model of the Nucleus, Fission and Fusion

• Elementary Particles: A Persistent Illusion

• A Zoo of Elementary Particles

• True Elementary Particles
  • Leptons
  • How about the hadrons?
    • Nucleons
    • Mesons
    • The strong force

• How about Beta Decay?

• The Force Carriers

• Are there more Fundamental Particles?

• How are Particle Properties Determined?

• Is This Whole Quark Story Right?

• Our World

The following sections are included:

• Interactions and Forces

• Acceleration and a Mysterious Force

• Mass in that Context

The following sections are included:

• Distance Measurements

• The Universe Canvas is Expanding

• Gravity in Einstein's Universe

• Einstein's Static World and Friedmann's Expanding Universe Models

• Evolving Ideas

• Our Present Large Scale Understanding

• A Solution to a Homogeneity Problem: The Inflation Scenario

• The Origin of the Elements on Earth and Elsewhere

• What Does the Cosmic Microwave Background Tell Us?

• Most of the Matter in the Universe is Not Visible

• We are in Trouble: The Expansion is Accelerating

Can we believe those models and theories that have been summarised in the previous chapters? They are what we think constitute at present the most credible description of the functioning of the Universe. The physical laws that we have enunciated, based on experimental observations, are used to make models and theories that are then used for a description of the evolution of the Universe we live in. To do that, we use logic and mathematics, rather efficient tools that have somehow been put at our disposal through our evolved brain. Some of the mathematics is described in the Annex as an illustration of the basis of the models that are assumed to represent as close as possible the reality of our world. The machinery that makes the laws of physics work is hidden to us. Then why does mathematics works? We don't know. Could there be some other tools that we don't know about? At present this is all we have. This mathematical basis is what makes the physics we know today so different from philosophy, which works logically but mainly in the abstract. The mathematics we use provides logic with numbers that are verifiable experimentally, directly, and quantitatively to several decimal places. I remember those years in college where we had to go through philosophy courses filled with assumptions, followed with logical reasoning, assembled in so-called thesis that appeared to satisfy the mind for the moment, but left us in a nebula afterwards, because we did not know what it really meant in practice and what to do with those theses. The conclusions could not be verified experimentally. They probably had some bearing on our way of thinking about life but they did not provide us with a real answer about how the world functions in practice. Religion is another approach to a description of the Universe from its creation to the arrival of man in its environment. The common belief is that what is written in the Bible was inspired from an ‘exo-being’ called God and is the absolute truth. This is one of the characteristics that make science different from religion. They are ‘orthogonal’. Science is based on experimental observations and proofs, not beliefs. It is not absolute and is always ready to be revised relative to its fundamental conclusions when confronted with new evidence, while religion stands by dogma and very reluctantly adapts to new reality, as is shown clearly by history, a situation still prevalent today. On the other hand, philosophy works in a parallel path to science claiming that its level of analysis is at a higher rung on the ladder of understanding than anything else. This claim is questionable…

The following sections are included:

• Annex: Mathematical Support

• Glossary

• Notes and References

• Suggested Reading

• Index

• About the Author