This image was generated for this article by AI © 2026 Kieron Conway - All rights reserved. This article will look at Einstein's alternative view of gravity and follows on from “ Part 1 of What is Gravity?” in which we looked at Newton's theory. Phase 1 - Development of Special Relativity Two hundred years after Newton, Albert Einstein (1879 to 1955) embarked on the development of special relativity , which shows how particles behave traveling at velocities close to the spe

This is an image generated for this article by AI © 2026 Kieron Conway - All rights reserved. This is the first of a two part article that asks the question, what is gravity? The first part will look at Newton's version of gravity and the second will delve into Einstein's alternative theory. The Facts Gravity is the force that keeps you glued to the ground. Without it, we would all just drift away into space. Gravity is what keeps the international space station going round t

A Journey into Modern Physics website Our web-site's pages and frames are rendered to device screens as intended using a CHROME browser on computers and mobile devices. We are aware that other browsers have been failing to render some pages correctly , usually resulting in text strings being wrapped inappropriately and messing up carefully formatted layouts. The problem is that different browsers render fonts slightly differently to CHROME, which can affect spacing between l

Graph showing how relativistic mass increases with speed © 2026 Kieron Conway - All rights reserved. Mass and Light-speed How often have you heard someone say that as an object approaches the speed of light, its mass increases? Historically, physicists used a quantity called relativistic mass , which does increase with speed and would approach infinity as the speed of light is approached. However, modern physics has largely abandoned this idea because it causes so much confus

This image is reproduced under licence. See details at end of article. © 2026 Kieron Conway - All rights reserved. What is the physics of water? In part 1 of this article, we looked at how water molecules have six unique properties that make it very special and vital to the evolution of life. In this article, we're going to look at how water molecules interact with other water molecules to create a dynamic and chaotic structure when in liquid form to a highly organised and st

© 2026 Kieron Conway - All rights reserved. The Development of Quantum Physics & Relativity Modern physics developed in response to phenomena that classical physics could not explain. Through necessity, the evolution of modern physics started to explain the unexplainable and in so doing led to a fascinating picture of reality that has endured decades of testing. Predictions have been made from the theories of quantum physics and Einstein's relativity that have been proved rig

© 2026 Kieron Conway - All rights reserved. Water - The Astonishing Liquid Water is something we all take for granted, but in fact it is the most astonishing liquid. Without it, none of us would be here, for reasons far beyond simply needing to drink it, as you'll see. Its physical properties make it quite unique and totally fascinating. Many of the things it can do, chemistry tells us it shouldn’t be able to do! To understand what it does, you have to delve into the physics

Even more new features this month, designed to help you continue your journey after reading the series A Journey into Modern Physics . Alternatively, if you haven't read any of the series, the video links, images and external references, all taken from the book series, might encourage you to down-load one or more of the E-books, or even buy a paperback version! These new features act as extensions to the book series, making it easier to access videos and external reading refe

Electron population of atomic orbital lobes In Part 1 of A Journey into Modern Physics,  chapter 4 describes how electrons populate atoms in terms of a sequential order. Diagrams were used, like the one above, to indicate how atoms are made up with a maximum of 2 electrons (one spin-UP and one spin-DOWN) in orbital lobes that are full. Only outermost orbitals exist in an empty state or a partially populated state (one electron). There may even be empty orbitals in between pop

© 2026 Kieron Conway In Part 2 of A Journey into Modern Physics,  chapter 7 has a flow diagram that shows the birth and death of stars of all sizes. This was figure 7.8 in Part 2 of the main series but was not included in the LIGHT adaptation of Part 2 for size reasons. To compensate for the omission, we have included the diagram on the web site. If you want to see how all stars enter the main sequence and what happens to them after the red-giant phase , then go to...

© 2026 Kieron Conway - All rights reserved. Inside hadrons As discussed in Part 1 of a Journey into Modern Physics, the strong-nuclear interaction is the force that keeps the quarks of protons confined to the tiny volume of the proton. The same applies to the neutron: in fact, it applies to the quarks in all hadrons, the proton being the only stable hadron when on its own. Outside hadrons – the nucleus of an atom So, how do all the protons and neutrons stay locked inside an a

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We've now published over a dozen articles on physics topics on this blog, so that you can continue your Journey into Modern Physics, even when you've read all three parts of the main series, or the LIGHT adaptations. We've built an index of the titles of the published articles in date order, for you to scan and go directly to an article of interest, rather than you having to sequentially search the list of articles on the blog. The index is accessed from the web site of the b

© 2026 Kieron Conway - All rights reserved. By accelerating charged particles (electrons, protons, or other ions), the LINAC (linear accelerator), invented in the 1930s, became one of the key machines that advanced nuclear physics well into the second half of the twentieth century. One of the main uses of LINACs today is as the primary source of particle beams at high-energy laboratories around the world. High-energy particle colliders are usually ring-based, such as the LHC

© 2025 Kieron Conway - All rights reserved. A Cosmic Mystery for the Next Generation of Scientists Recent research from South Korea (2025), has raised new questions about one of the biggest mysteries in modern physics: dark energy . Understanding what dark energy is, and what it might do in the future, could determine the ultimate fate of our universe and there may be new evidence that we might have got it wrong! The Expanding Universe: A Quick History Before the 1990s Modern

© 2025 Kieron Conway - All rights reserved. When writing about noble gases in a Journey into Modern Physics , the expression ' react with nothing, under normal conditions ' was always used. This article explores noble gas chemistry, which may come as a surprise. Under certain conditions, some of the noble gasses do react with other atoms, in particular the more massive gasses are more reactive than the lighter ones as their outermost orbitals are not as strongly attached to

© 2025 Kieron Conway - All rights reserved. There are two fundamental problems in modern physics, which are; Problem 1: Spiral galaxies don't have enough gravity to stop their arms from spinning off into space. Something is clearly producing the additional gravitational attraction that keeps spiral galaxies from spinning apart. Whatever it is, it can't be detected, so it's called 'dark-matter' . Problem 2: The expansion of the universe is not slowing down as expected, it's ac

© 2025 Kieron Conway - All rights reserved. In modern physics, we know that empty space isn’t really empty. Even in a perfect vacuum, tiny bursts of energy are constantly being created and disappearing. These are called quantum fluctuations , and they give space a kind of fizzy, restless background. Many scientists use the nickname “quantum foam” to describe this ever-changing activity. If you recall, there is energy at every point in the vacuum of space and Heisenberg's unc

© 2025 Kieron Conway - All rights reserved. There are two things that can help us answer this question, although you may not be happy about the outcome. But the conclusion might cheer you up! The ΛCDM Model The current theory describing the history of the universe from time = 0 to the present is known as the ΛCDM (Lambda–Cold Dark Matter) model . Λ (Lambda) refers to Einstein’s cosmological constant . It has had a checkered history (Einstein once called it his “biggest mist

© 2025 Kieron Conway - All rights reserved. Protons (the uud quark configuration of the lightest of all baryons) are the most stable of all the hadrons. Experiments show that the proton’s lifetime must be greater than 10 ^34 years, far exceeding the age of the universe. So if protons do decay, it happens so rarely that it is effectively invisible to us. So, how come they are so stable when hadrons in general, are not: even the neutron (ddu quark composition) is unstable when