Physics Articles

Here contains the collection of expert physics articles that deal with physics topics. These span all skill ranges and may include astronomy and cosmology topics. Learn something new today by professionals in the fields you are interested in!

blockuniverse3

Blockworld and its Foundational Implications: General Relativity and the Big Bang

 In parts 1 and 2 of this 5-part Insights series, I explained the blockworld (BW) implication of special relativity (SR). Geroch sums up the…
blockuniverse2

Blockworld and Its Foundational Implications: The Relativity of Simultaneity and Blockworld

 In part 1 of this 5-part Insights series, I introduced two consequences of the second postulate of special relativity (SR): time dilation…
blockuniverse1

Blockworld and Its Foundational Implications: Time Dilation and Length Contraction

 This is the first in a 5-part series of Insights that will introduce blockworld (aka "block universe”) and use it to address a puzzle…
prequantum4

Examples of Prequantum Field Theories IV: Wess-Zumino-Witten-type Theories

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4 Comments
  At the end of this page, we will have come full circle back to the first article in the series 20 years ago -- The M-Theory Conjecture.We…
prequantum3

Examples of Prequantum Field Theories III: Chern-Simons-type Theories

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  After having constructed gauge fields and higher gauge fields in the previous article by systems of ##L_\infty##-algebroid-valued…
guagetheory

Examples of Prequantum Field Theories II: Higher Gauge Fields

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   After having recalled ordinary gauge fields from a dg-algebraic perspective in the previous article, here I discuss…
prequantumft

Examples of Prequantum Field Theories I: Gauge Fields

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  After having motivated the need for prequantum field theory and having laid out its principles (i. extremal action, ii. global…
animationwalk

Fun with Self-Avoiding Walks Simulations

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16 Comments
This post is about some simulations I did of self-avoiding random walks. These are what they sound like with each step, the position of the walk moves…
prequantumgeometry5

Higher Prequantum Geometry V: The Local Observables – Lie Theoretically

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1 Comment
 This article discusses how the previous considerations naturally follow the concepts of local observables of local field theories and of…
prequantumgeometry4

Higher Prequantum Geometry IV: The Covariant Phase Space – Transgressively

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  The Euler-Lagrange ##p##-gerbes discussed in the previous article are singled out as being exactly the right coherent refinement…
prequantumgeometry3

Higher Prequantum Geometry III: The Global Action Functional – Cohomologically

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9 Comments
  The previous article ended with the concept of classical locally variational field theories, of which a class of examples are…
blackbody

A Poor Man’s CMB Primer: Bumps on a Blackbody

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15 Comments
 Astronomers Arno Penzias and Robert Wilson discovered the cosmic microwave background in 1965. They were not looking for it.They were…
prequantumgeometry2

Higher Prequantum Geometry II: The Principle of Extremal Action – Comonadically

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1 Comment
  The previous article motivated the importance of considering "pre-quantum field theory" in-between classical and quantum field…
redshiftblackholes

Time Dilation & Redshift of Schwarzschild Black Holes

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Time dilation near a Schwarzschild black hole The following is an overview of the time-dilation and gravitational-redshift effects of a static (Schwarzschild)…
prequantumgeometry

Higher Prequantum Geometry I: The Need for Prequantum Geometry

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18 Comments
 Before proceeding with a discussion of the super p-brane sigma models, whose emergence from the superpoint I discussed in the previous article,…
atoms

Can We See an Atom?

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Introduction In this article I discuss how images of atoms are made, what exactly we are looking at, and what it means to "see" an atom. Over the decades…
gravity3

Does Gravity Gravitate: The Wave

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17 Comments
 In the first two posts in this series, we looked at different ways of interpreting the question "does gravity gravitate?" We left off at…
gravitate2

Does Gravity Gravitate? Part 2

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30 Comments
 In the first post of this series, I talked about two ways to answer the title question, one leading to the answer "no" and the other leading…
birthcmb

A Poor Man’s CMB Primer: The Birth of a Cosmic Background Radiation

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3 Comments
 The early universe was hot. So hot that nuclei boiled. The great thermal energy of the universe overwhelmed the confining efforts of the…
modulation

Mixing vs Beating: Superheterodyne & Beat Frequency

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36 Comments
Mixing vs. Beating: a brief history A long time ago I read a paper in the IEEE Proceedings recounting the history of the superheterodyne receiver. Overall…
balloonanalogy

Balloon Analogy Explained: Cosmology, Expansion & Limits

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62 Comments
The Balloon Analogy is a straightforward way to illustrate — without being complete — two important points of modern cosmology that many people find…
spacetime4

Struggles With the Continuum: Point Particles and the Electromagnetic Field

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20 Comments
 In these posts, we're seeing how our favorite theories of physics deal with the idea that space and time are a continuum, with points described…
bubbles

Explosion-Generated Collapsing Vacuum Bubbles Reach 20,000 Kelvin

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5 Comments
Experiment overview In a recent paper published in Physical Review Letters (PRL), one of the top physics journals, Jérôme Duplat and Emmanuel Villermaux…
cmb

A Poor Man’s CMB Primer: Orientation of the Universe

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4 Comments
 This is a picture of the cosmic microwave background:Fig 1. The cosmic microwave background as seen by the European Space Agency's…
planck

What Planck Length Is and It’s Common Misconceptions

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30 Comments
The Planck length is an extremely small distance constructed from physical constants. Many misconceptions overstate its physical significance, claiming…
spacetime2

Struggles With The Continuum: Quantum Mechanics of Charged Particles

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39 Comments
 Last time we saw that nobody yet knows if Newtonian gravity, applied to point particles, truly succeeds in predicting the future. To be precise:…
animal speeds

Animal Speed Scaling: Body-Lengths per Second Across Sizes

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19 Comments
Introduction In a recent American Journal of Physics issue, I read an interesting paper by Nicole Meyer-Vernet and Jean-Pierre Rospars examining the top…
infinity_faq

Infinity in Mathematics: Limits and Cardinality FAQ

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17 Comments
Introduction Understanding the behavior of infinity is one of the major accomplishments of mathematics. However, the infinite is often misunderstood and…
man_on_moon

Apollo Program: Moon Missions & Last Moonwalk 1972

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Eugene Cernan: Last to Walk on the Moon On December 11, 1972, astronaut Eugene Cernan became the last person to walk on the lunar surface, marking the…
spacetime

Is Spacetime Really a Continuum?

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29 Comments
  Introduction Is spacetime really a continuum?  That is, can points of spacetime really be described---at least locally---by lists of four…
photoelectric

“Violating” Einstein’s Photoelectric Effect Model

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4 Comments
Einstein's Photoelectric Insight One of the most spectacular theoretical descriptions that Einstein had ever produced is the corpuscular nature of light…
CosmologicalHorizons

Inflationary Misconceptions and the Basics of Cosmological Horizons

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45 Comments
Introduction It is a common saying that during inflation "space expanded faster than the speed of light."  This statement is meant to articulate the…
lightswitch

What Happens When You Flip the Light Switch: From Zero Seconds to 20 Years

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47 Comments
Introduction Few people know what happens when a customer does something like flipping a light switch. The full explanation requires descriptions of topics…
relativitytherorm

Learn the Relativistic Work-Kinetic Energy Theorem

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19 Comments
I was bothered for a long time by the reasons for the relativistic validity of the work-kinetic energy relation ##\Delta E=Fd##, which holds without any…
supergravity

Emergence From the Superpoint

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6 Comments
 In the previous article we saw that the generalization of super-Lie algebras to homotopy super-Lie n-algebras (super L-infinity algebras)…
liealgebra

Homotopy Lie-n Algebras in Supergravity

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1 Comment
 The previous article in this series claimed that the mathematics of the 21st century that had fallen into the 1970s in the form of string…
string theory

It Was 20 Years Ago Today — the M-theory Conjecture

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2 Comments
  While the world didn't end, after all, 15 years back at the turn of the millennium, in hindsight it is curious that, almost unnoticed,…
hupmisconceptions1

Learn a Misconception of the Heisenberg Uncertainty Principle

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26 Comments
One of the common misconceptions about the Heisenberg Uncertainty Principle (HUP) is that it is the fault of our measurement accuracy.A description…
errorbars

Plus/minus What? How to Interpret Error Bars

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20 Comments
People sometimes find themselves staring at a number with a ± in it when a new physics result is presented. But what does it mean? This Insight aims to…
LCDM4

Approximate LCDM Expansion in Simplified Math (Part 4)

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  Part 4: Cosmic Recession Rates An astronomer, accompanied by his amateur relativist friend, aimed a telescope at a distant galaxy and measured…
LCDM3

The LCDM Cosmological Model in Simplified Math (Part 3)

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5 Comments
  Part 3: Important Cosmological Horizons and Distances A question that often comes up is: "how big is the observable universe?"The question…
lcdmjorrie

Approximate LCDM Expansion in Simplified Math (Part 2)

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14 Comments
  Part 2: Time and Distance In Part 1 we have seen how one of the simplest ways of expressing the fractional expansion rate of the universe,…
neutrino

Learn About Neutrino Masses and Speed

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28 Comments
It was hard to miss the 2011 OPERA neutrino speed measurement that indicated superluminal neutrino speeds (and turned out to be a measurement error), but…
gravity

Understanding the General Relativity View of Gravity on Earth

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102 Comments
Often students have difficulty reconciling the General Relativity (GR) view of gravity versus their own experience with gravity on the surface of Earth.…
cosmo

Approximate LCDM Expansion in Simplified Math

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11 Comments
 If we restrict ourselves to a spatially flat LCDM universe model (and ignore the early radiation energy density), the first Friedmann equation…
physics love

Should You Do Science for Love or for Money

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19 Comments
While I served on the math faculty of the US Air Force Academy, we invited numerous cadets to participate in self-funded research…
measuringentanglement

Can You Measure Quantum Entanglement?

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23 Comments
What is Quantum Entanglement? Though any pair of particles, given their history, might happen to be entangled, some pairs are more entangled than others. …
garrett

Garrett Lisi’s Superparticle Bet With Frank Wilczek

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52 Comments
There is an interesting story unfolding in particle physics. The main motivation for building the Large Hadron Collider was to search for new particles.…
qftintegrals

Some Useful Integrals In Quantum Field Theory

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2 Comments
In my paper on renormalisation I mentioned what most who have studied calculations in Quantum Field Theory find, it's rather complicated and mind-numbing.…
arrowoftime

Retrocausality: How Fundamental is the Arrow of Time?

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26 Comments
In this Insight, I'll discuss a recent experiment ([1]  [2] [3]) by some Australian physicists that has brought a thought experiment into the real world…
research work

Initiating Physics PhD Research: Getting Started Effectively

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Full Chapter List - So You Want To Be A Physicist... Series Part I: Early Physics Education in High schools Part II: Surviving the First Year…
gas compression

Reversible vs Irreversible Gas Compression and Expansion Work

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26 Comments
Introduction In learning Thermodynamics, one of the difficult concepts that many students struggle with is the difference between reversible and irreversible…
perbation theory

Introduction to Causal Perturbation Theory

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30 Comments
Relativistic quantum field theory is notorious for the occurrence of divergent expressions that must be renormalized by recipes that on first sight sound…
cheshirecat

Weak Values Part 2: The Quantum Cheshire Cat Experiment

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In a previous Insight, Weak Values Part 1: "Asking Photons Where They Have Been," I showed different methods for computing the relative intensities in…
askingphotons

Weak Values Part 1: Asking Photons Where They Have Been

In a previous Insight on retrocausality, I explained an experiment by Danan, Farfurnik, Bar-Ad, and Vaidman (DFBV)[1], “Asking Photons Where They Have…
negative temperature

Negative Absolute Temperatures: Explanation & Examples

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9 Comments
It's a famous result in thermodynamics that you cannot reach absolute zero no matter how hard you try. Given the definition of absolute zero, it is also…
What is Energy

A Definition and Controversy of Energy

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[CONTENT] What is energy? Energy is a fundamental concept that refers to the capacity of a system to do work. It is a scalar quantity, meaning it has magnitude…
LHC

LHC Part 3: Protons as Large as a Barn

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Introduction See also part 1 and part 2 of the series.The LHC commissioning phase is coming to and end. On Wednesday May 20th 2015, the first collisions…
earth year

How to Scientifically Measure How Many Days Are in a Year

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75 Comments
How many days are there in a year? Ask pretty much anyone and they will tell you 365, except for leaps years which have 366. In addition,…
redlights

Learn About the Greenberger-Horne-Zeilinger Experiment

In two previous Insights, I shared Mermin's explanation of the Hardy experiment[1] and the Mermin device[2]. Both of his corresponding AJP papers presented…
mermin

The Quantum Liar Experiment: An Instantiation of the Mermin Device

In 1981, Mermin published a paper[1], "Bringing home the atomic world: Quantum mysteries for anybody" in which he explained the mystery of quantum nonlocality[2]…
classroom

Explore Some Sins in Physics Didactics

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Introduction There are many sins in physics didactics. Usually, they occur, because teachers, professors, textbook or popular-science-book writers, etc.…

LHC Part 2: Commissioning

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23 Comments
View All PartsPart 1: LHC about to restart - some FAQs Part 2: Commissioning Part 3: Protons as Large as a Barn Part 4: Searching for New Particles…
supernova

Star Fate: From Nebulae to White Dwarfs and Black Holes

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Star Fate: From Birth to Black Holes Stars form in vast clouds of gas and dust called nebulae. Over time gravity pulls material together until the core…
hand_to_hand_combat

Hand-to-Hand Combat Physics — Force, Momentum, Speed

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Physics of Hand-to-Hand Combat Hand-to-hand combat (often abbreviated H2H or HTH) refers to fighting at very close range, usually without weapons. It includes…