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!

blackbody

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

/
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

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

Learn Time Dilation and Redshift for a Static Black Hole

/
76 Comments
The following is an overview of the time dilation and gravitational redshift effects of a static (Schwarzschild) black hole. In accordance with general…
prequantumgeometry

Higher Prequantum Geometry I: The Need for Prequantum Geometry

/
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?

/
12 Comments
In this article, I will discuss how these images of atoms are made, what exactly we are looking at, and what it really means to see an atom. Over the decades…
gravity3

Does Gravity Gravitate: The Wave

/
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

/
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

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

Understand the Acoustic Modulation vs. Beating Confusion

/
36 Comments
A long time ago I read a paper in the IEEEProceedings recounting the history of the superheterodyne receiver. Overall it was a very interesting and informative…
balloonanalogy

Learn Inflation Balloon Analogy Misconceptions

/
62 Comments
This article was written with considerable input from several senior members of the PF community.The Balloon Analogy is a simple-minded way to help…
spacetime4

Struggles With the Continuum: Point Particles and the Electromagnetic Field

/
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

/
5 Comments
Key PointsJérôme Duplat and Emmanuel Villermaux published a paper in Physical Review Letters (PRL) to generate centimeter-sized vacuum bubbles…
cmb

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

/
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

/
29 Comments
The Planck length is an extremely small distance constructed from physical constants. There are a lot of misconceptions that generally overstate its physical…
spacetime2

Struggles With The Continuum: Quantum Mechanics of Charged Particles

/
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

Exploring a Paper on Scaling Laws and the Speed of Animals

/
19 Comments
Key PointsScaling arguments are powerful tools in physics between vague descriptive arguments and rigorous formulae. Examples of scaling arguments…
infinity_faq

Learn the Top 5 Misconceptions About Infinity

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

The Last Man On The Moon | A Look Back at Previous Missions

/
0 Comments
On 11th December 1972, just over 45 years ago, man set foot on the moon for the last time.The Apollo 17 mission manned by Eugene Cernan and geologist…
spacetime

Struggles With the Continuum: Is Spacetime Really a Continuum?

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

“Violating” Einstein’s Photoelectric Effect Model

/
4 Comments
One of the most spectacular theoretical descriptions that Einstein had ever produced is the corpuscular nature of light that he used in his 1905 photoelectric…
CosmologicalHorizons

Inflationary Misconceptions and the Basics of Cosmological Horizons

/
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

/
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

/
20 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

/
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

/
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

/
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

/
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

/
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? The aim of this Insight…
LCDM4

Approximate LCDM Expansion in Simplified Math (Part 4)

/
14 Comments
  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)

/
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)

/
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

/
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

/
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

/
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

/
19 Comments
When I look over the most highly cited papers and my favorite accomplishments, I am struck by the fact that most of the projects were not funded by…
measuringentanglement

Can You Measure Quantum Entanglement?

/
23 Comments
Though any pair of particles, given their history, might happen to be entangled, some pairs are more entangled than others.Since at least the 1990s,…
garrett

Garrett Lisi’s Superparticle Bet With Frank Wilczek

/
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

/
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?

/
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

How to Initiate Research Work As a Physics Major

/
1 Comment
  It has been a while since the last installment of this series, so let’s recap on where you are right now. You should already…
gas compression

Reversible vs Irreversible Gas Compression and Expansion Work

/
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

/
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

/
0 Comments
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

What are Negative Absolute Temperatures

/
9 Comments
It's a famous result in thermodynamics that you can't reach absolute zero no matter how hard you try. Also, the definition of absolute zero makes it obvious…
What is Energy

What is Energy? A Definition and Controversy

/
44 Comments
SummaryThe article addresses the fundamental question, "What is energy?" and explores why discussions about energy can be challenging. It introduces…
LHC

LHC Part 3: Protons as Large as a Barn

/
8 Comments
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

/
75 Comments
SummaryThe article explores the measurement of the number of days in a year, considering various definitions of a "day" and a "year." It starts…
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…
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

/
203 Comments
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

/
23 Comments
Introduction Last month, I wrote a FAQ about working at the LHC, at the time the first beams were circulating in the machine after a stop of two years.…
supernova

What are the Fates of Massive Stars

/
0 Comments
Key PointsStars are born in primordial nebulae, gaseous molecular clouds on the spiral arms of galaxies Stars smaller than 1.4 suns will settle…
hand_to_hand_combat

Learn the Physics of Hand-to-Hand Combat

/
0 Comments
Key Points Martial arts effectively use principles of physics to achieve goals quickly and forcefully. Athletic intelligence enables humans to…