🌌 Introduction to Physics
The Science That Explains How the Universe Works
Physics is the science that seeks to understand the fundamental laws of natureโthe forces, energies, and interactions that shape everything from the tiniest particles to the vastness of galaxies. It explores how objects move, why they move, and what rules govern their behavior.
At its heart, physics asks questions like:
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Why do things fall?
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How does light travel?
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What causes electricity and magnetism?
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What is time, space, energy, and matter?
Often called the “foundation of all sciences,” physics underpins everything from chemistry and biology to engineering and astronomy. Whether it’s explaining why the sky is blue, how bridges stay standing, or how smartphones work, physics provides the framework.
From Isaac Newtonโs laws of motion to Albert Einsteinโs theory of relativity, and from quantum mechanics to black holes, physics challenges us to think bigโand small. It combines deep curiosity with mathematical precision to uncover the rules of reality.
Studying physics not only helps us understand the universeโit equips us with problem-solving skills that drive innovation and technological progress.
Physics by Topic
Cepheid Variables
What are Cepheid Variables? Why are they useful? Measuring the Milky Way Hubble’s work with Cepheid Variables Existence of other galaxies The Expanding Universe Dark Energy Dating the Universe What are Cepheid Variables? Certain stars called Cepheid Variables have changes to their magnitude which increase and decrease at regular intervals (or periods). This image is from NASA’s Hubble telescope showing RS Puppis, as Cepheid Variable with a period of 40 days and a change in magnitude of around 5 factors. Why are they useful? In 1912 American astronomer, Henrietta Leavitt, came up with a way to use the characteristics of Cepheid Variables to calculate their distance. The periods of changes in magnitude from Cepheid Variables vary from star to star but, if the period is recorded, the variation in magnitude can be used to calculate the distance. Some of these Cepheid Variables were close enough to have their distance measured using the parallax method (see below). Henrietta Leavitt noticed a relationship between the absolute magnitude and the star’s period allowing modern astronomers to accurately calculate the distances of stars far beyond the parallax method. It is this technique that has allowed modern astronomers to calculate the size and shape of our galaxies, distant galaxies and even help calculate the age of our universe. The bright blue star is one of 50 cepheid variables used to measure the distance of galaxy NGC 4603 which they inhabit. It is one of the furthest galaxies measured using the method and is believed to reside 107,000,000 light years...
Atoms
It was believed for a thousand years that atoms were the smallest component of matter, but in the late 19th century, the first evidence that atoms were made up of smaller sub-atomic particles came to light. About Atoms Diagram of an atom Electrons Discovery of Electrons Properties of Electrons Protons Discovery of Protons Properties of Protons Neutrons Discovery of Neutrons Properties of Protons About Atoms It has been known for a thousand years that all matter is made up of small particles known as atoms, but for much of this time, it was believed that atoms were the smallest component of matter. It was not until the late 19th and early 20th century that the first evidence that atoms were made up of smaller sub-atomic particles came to light. A = The Nucleus of the atom contains the protons and neutrons. Despite accounting for the majority of an atomโs mass, the nucleus occupies a minute proportion of the total space. The Diameter of the nucleus is approximately 4 femtometres or 4 x 10-15 meters. It is very difficult to measure the diameter of the nucleus because, like our atmosphere, it has no defined edge but gradually fades away. B = This is mainly just empty space where the electrons orbit the nucleus. Its diameter (and that of the whole atom) is 0.1 nanometres or 0.1 x 10-9 meters. Here is the chemical symbol for helium as you might see it on a periodic table. The number at the top is known as...
