The Expert Physics and Math Blog

no tidal bulge

Beyond the Tidal Bulge

/8 Comments/in /by

Overview That there is no tidal bulge is the key premise of this article. Upper-level oceanography undergraduates and above know this. Yet the tidal bulge is still used to portray why the Moon is receding the Earth. If there is no tidal bulge, some other explanation is in order. That other explanation uses gravitation as…

Trending Articles

Recent Entries

inflation5

A Poor Man’s CMB Primer: Quantum Seeds

/
11 Comments
 The CMB establishes a record of ancient acoustic oscillations in the baryon-photon plasma. We've been studying how these primordial sound…
mathoperators

How to Tell Operations, Operators, Functionals, and Representations Apart

/
24 Comments
 All these concepts belong to the toolbox of physicists. I read them quite often on our forum and their usage is sometimes a bit confusing.…
epsresults

Find Out the Results Shown at 2017 CERN EPS Conference

/
7 Comments
The EPS conference was a week ago, and many new results and future plans were shown. A good general overview has been collected by Paris Sphicas in his…
m-theory

Super p-Brane Theory Emerging from Super Homotopy Theory

/
6 Comments
  A notorious open problem: What is the non-perturbative theory formerly known as Strings?We still have no fundamental formulation of “M-theory”…
Parsevalstheorem

Learn an Integral Result from Parseval’s Theorem

/
5 Comments
Introduction: In this Insight article,  Parseval's theorem will be applied to a sinusoidal signal that lasts a finite period of time.  It will be shown…
EdmondHamilton

Assessing the Physics in Edmond Hamilton’s “The Second Satellite”

/
2 Comments
This article won't contain much about physics that typical readers of this site don't already know. However,  deconstructing improper physics in literature…
entanglement_entropy2

Lesson on Entanglement Entropy in Quantum Field Theory

/
3 Comments
Part 1: Quantum Mechanics[This article expects the reader to have some experience with quantum field theory and path integrals][I should also…
whatisatensor

What Is a Tensor? The mathematical point of view.

/
58 Comments
Tensor Key pointsThe author begins by questioning the nature of numbers and their deeper significance. Numbers can represent various mathematical…
jimbiology

Interview with Biologist Jim McNamara

/
17 Comments
What got you interested in biology?I was an amateur naturalist as a kid. Had collections of all sorts, and a small menagerie -- much to my mother's…
dampedforces

Learn Damped Motion in Classical and Quantum Mechanics

/
21 Comments
This Insights article is about dissipative forces (friction, air resistance, viscosity...).Damping by friction forces is one of the concepts that is…
name_the_scientist

Name the Scientist Quiz and Trivia

/
27 Comments
Time to test your scientist photo recognition skills! As always please post your score in the comment thread at the end.Ready for your next quiz?…
pamelagay

Interview with Astronomer Pamela Gay

/
2 Comments
Please give us a bit of background into your educational and professional life. I'm a public school kid through and through. After going to the local…
SpectralParadox

Exploring the Spectral Paradox in Physics

/
17 Comments
In terms of wavelength, peak solar radiation occurs at about 500 nm.  Interestingly, this is well within the range of human vision.  When solar radiation…
undergradresearch

Finding Niches for Publishable Undergraduate Research

/
6 Comments
Undergraduate interest in research is a good thing; it's even better if they aspire to publish their work for review and consideration from a broader audience.…
coldquestioning

How to Ask Questions Effectively and Avoid Cold Questions

/
71 Comments
We frequently get questions such as these:"What is energy?""What are Cooper Pairs?""What is conservation of momentum?"etc...etc.And…
processing

The Joy of Processing

/
11 Comments
In the early days of the personal computer revolution, computers were small, simple, and easy to operate. It was always great fun to write BASIC games…
entanglement_entropy

Learn Entanglement Entropy in Quantum Mechanics

/
22 Comments
Quantum Mechanics(QM) is one of the greatest intellectual achievements in human history. Not only because it describes the world at the microscopic level…
BondiKcalculus

Learn Relativity Using the Bondi K-calculus

/
20 Comments
Although Special Relativity was formulated by Einstein (1905), and given a spacetime interpretation by Minkowski (1908) [which helped make special relativity…
physicslab

Revamping Undergraduate Introductory Physics Laboratory

/
19 Comments
This is a compilation of my blog entry on this singular "project" to change the way we conduct the introductory physics laboratory in most US universities.…
frasercain2

Q&A With Universe Today’s Astronomer Fraser Cain

/
4 Comments
Special thanks to Universe Today founder Fraser Cain for this fascinating video Q&A! All questions were provided by the members of Physics Forums.…
lensfocus

Lenses and Pinholes: What Does “In Focus” Mean?

/
11 Comments
In introductory physics, the optics unit often teaches about virtual and real images, focal lengths, indexes of refraction, etc. Some questions that are…
sabine1

Interview with Theoretical Physicist: Sabine Hossenfelder

/
18 Comments
We are pleased to introduce Sabine Hossenfelder. Sabine is a theoretical physicist from the Frankfurt Institute for Advanced Studies. Sabine also authors…
deriitive5

The Pantheon of Derivatives – Part V

/
2 Comments
  Important Theorems - biased, of course Implicit Function Theorem [1] Jacobi Matrix (Chain Rule). Let ## (x_0,y_0 ) ## be a point in$$U_1…
RelativityVariables

Relativity Variables: Velocity, Doppler-Bondi k, and Rapidity

/
8 Comments
Traditional presentations of special relativity place emphasis on "velocity", which of course has an important physical interpretation... carried over…
deriitive4

The Pantheon of Derivatives – Part IV

/
6 Comments
  Lie Derivatives A Lie derivative is in general the differentiation of a tensor field along a vector field. This allows several applications…
deriitive3

The Pantheon of Derivatives – Part III

/
3 Comments
  Some Topology Whereas the terminology of vector fields, trajectories, and flows almost by itself suggests its origins and physical relevance,…
cameralense

Learn About New High Performance Ultra-wide Angle Camera Lenses

/
7 Comments
Note, unless otherwise specified, all focal lengths are in terms of the 35mm image format.Recently, there has been a flurry of new high-performance…
deriitive2

The Pantheon of Derivatives – Part II

/
8 Comments
  Generalizations Beyond ##\mathbb{R}## and ##\mathbb{C}## As mentioned in the section on complex functions (The Pantheon of Derivatives - Part…
deriitive

The Pantheon of Derivatives – 5 Part Series

/
3 Comments
  Differentiation in a Nutshell I want to gather the various concepts in one place, to reveal the similarities between them, as they are often…
diffractiontheory

The Diffraction Limited Spot Size with Perfect Focusing

/
12 Comments
Purpose The purpose of this Insights article is to give the reader a brief introduction to the principles behind diffraction-limited focusing. The reader…
learned

What Is The Most Important Thing That You Learned?

/
10 Comments
I mentioned in an earlier Insight what I think are the most important things you can learn by being on Physics Forums. This time, I tackled the question…
integraltrick

Trick to Solving Integrals Involving Tangent and Secant

/
6 Comments
This little trick is used for some integration problems involving trigonometric functions is probably well-known, but I only learned it yesterday. So…
math

Interview with Mathematician Fresh_42

/
8 Comments
We are please to introduce our newest member of the mentor group, fresh_42!Can you give us a brief bio?I studied mathematics and economy and always…
linearacceleration

Frames of Reference: Linear Acceleration View

/
2 Comments
My previous Insight, Frames of Reference: A Skateboarder's View, explored mechanical energy conservation as seen from an inertial frame moving relative…
scavengerhunt2

PF Insight Scavenger Hunt 2

/
4 Comments
We have an amazing count of over 320 Insights published at Physics Forums. Now we test to see how much you remember from some of them. If you need a hint…
computerlanguages

An Introduction to Computer Programming Languages

/
67 Comments
In this Insights Guide, the focus is entirely on types of languages, how they relate to what computers do, and how they are used by people. It is a general…
cornuspiral

Learn Frenet Equations in 2-D Which Result in the Cornu Spiral

/
3 Comments
This Insights article is intended as an introduction to the Frenet-Serret equations by showing an interesting application that results from a case in two-dimensional…
experimenthistory

Learn About History’s First Science Experiments

/
11 Comments
In this Insight, I'm going to talk about two of the first science experiments in recorded history. One was allegedly performed by the Prophet Elijah in…
boatramps

Real Research in Unexpected Places; Boat Ramps

/
4 Comments
Read part 1 -Backyards, Barns, BayousWhen I was offered a job at the Air Force Academy, it seemed like an opportunity to exercise both my commitment…
geometrysimple

When Simple Geometry Unveils Deep Math

/
28 Comments
Introduction It is a remarkable fact that consideration of very elementary concepts in geometry often leads quickly into deep and unexpected mathematical…
quantumflux

Learn About Vacuum Fluctuations in Experimental Practice

/
41 Comments
This Insight Article is a sequel of the Insight Articles ”The Physics of Virtual Particles”, “Misconceptions about Virtual Particles“ , and ''The…
magnet

Permanent Magnets Explained by Magnetic Surface Currents

/
38 Comments
Introduction: The purpose of this Insight is to explain permanent magnets in a way that is in agreement with advanced textbooks on the subject, and that…
nasa

NASA Quiz and Trivia: Test Your NASA Knowledge

/
26 Comments
Since the mid 20th century NASA has been a force in aerospace research and programs. Let's find out just how much you know about it's history, programs…
jimhardy

Interview with Instrument Engineer Jim Hardy

/
9 Comments
Give us a little background on Jim HardyBorn and raised in Miami Florida of parents with roots in Springfield Missouri . So at heart i'm a small town…
highercategorytheory

Why Higher Category Theory in Physics?

/
30 Comments
 This here is my personal story. For an alternative introduction see my talk: Higher Structures in Mathematics and Physics.Initially,…
steven

Interview with Physics Mentor: Stevendaryl

/
5 Comments
Give us a brief history on stevendarylI was born and raised in the American South, mostly living in Georgia. It's a Southern tradition, for some reason,…
inferometer

Fabry-Perot and Michelson Interferometry: A Fundamental Approach

/
14 Comments
Fabry-Perot Effect: The Fabry-Perot effect is usually treated in most optics textbooks as the interference that results from multiple reflections of the…
FourierSeries

Using the Fourier Series To Find Some Interesting Sums

/
4 Comments
Preliminaries If f(x) is periodic with period 2p and f’(x) exists and is finite for -π<x<π, then f can be written as a Fourier series: [itex]f(x)=\sum_{n=-\infty}^{\infty}a_{n}e^{inx}…
SchwarzschildGeometry4

The Schwarzschild Geometry: Physically Reasonable?

/
33 Comments
 In the last article, we looked at various counterintuitive features of the Schwarzschild spacetime geometry, as illustrated in the Kruskal-Szekeres…
SchwarzschildGeometry3

The Schwarzschild Geometry: Spacetime Diagrams

/
12 Comments
 When we left off in part 2, we were looking at the metric for the Schwarzschild geometry in Kruskal-Szekeres coordinates:$$ ds^2 = \frac{32…
SchwarzschildGeometry2

The Schwarzschild Geometry: Coordinates

/
2 Comments
 At the end of part 1, we looked at the form the metric of the Schwarzschild geometry takes in Gullstrand-Painleve coordinates:$$ ds^2…
fakenews

The Problem of Fake News and Science Reporting

/
107 Comments
During and even after the recent US election campaign, numerous reports of fake news, made-up news, and other kinds of news were deemed either outright…
SchwarzschildGeometry1

The Schwarzschild Geometry: Key Properties

/
22 Comments
 Not long after Einstein published his Field Equation, the first exact solution was found by Karl Schwarzschild. This solution is one of the…
quantumapplitudes

Learn About Quantum Amplitudes, Probabilities and EPR

/
83 Comments
This is a little note about quantum amplitudes. Even though quantum probabilities seem very mysterious, with weird interference effects and seemingly nonlocal…
fishresearch

Real Research in Unexpected Places: Backyards, Barns, Bayous

/
2 Comments
21st-century science labors under the myth that good experimental science requires expensive lab facilities in a university or institutional setting.…
stephenhawkings

Stephen Hawking Quiz: Think You Know Stephen Hawking?

/
22 Comments
Stephen Hawking has been a giant in the science world for decades. He has been a accessible figure with his willingness to reach out to the public in various…
representations

Linear Representations and Why Precision is Important in Math

/
2 Comments
First of all: What is a representation? It is the description of a mathematical object like a Lie group or a Lie algebra by its actions on another space…
angledimensions

Can Angles be Assigned a Dimension?

/
106 Comments
1. Some Background on Dimensional Analysis ... if you are not already familiar with it. 1.1 Dimensions Dimensional Analysis is a way of analyzing…
whystudyphysics

Why Study Physics? A Bit Goes a Long Way!

/
6 Comments
If you don’t plan to become a scientist or an engineer, is there a good reason to study physics?  I say, “Yes,” because knowing just a little bit…
vaccummyth

Explore The Vacuum Fluctuation Myth in Quantum Theory

/
230 Comments
This Insight Article is a sequel of the Insight Articles ”The Physics of Virtual Particles” and “Misconceptions about Virtual Particles“ which…
anyon

Learn The Main Conceptual Ideas of Anyon Particles

/
55 Comments
Every quantum physicist knows that all particles are either bosons or fermions. And the standard textbook argues that this so does not depend on the number…
tripods

Digital Camera Buyer’s Guide: Tripods

/
1 Comment
 A tripod holds a camera still while the shutter is open, preventing motion blur.  The tripod must be able to maintain this stability in…
dslr

Digital Camera Buyer’s Guide: DSLR

/
15 Comments
  I'm ready for a DSLR! A: These cameras were originally designed for professionals.  Users of these cameras are expected to already understand…
partial-differentiation

Learn Partial Differentiation Without Tears

/
6 Comments
Differentiation is usually taught quite well. Perhaps that's because it is the first introduction to calculus, which is considered a big step in a student's…
frameofreference2

Frames of Reference: A Skateboarder’s View

/
22 Comments
My essay Explaining Rolling Motion raised some commentary about frames of reference and their equivalence when solving physics problems. I wish to pursue…
relativitygauge

Exploring General Relativity as a Gauge Theory

/
24 Comments
The fundamental interactions of the Standard Model are described by Yang-Mills theory. This is a gauge theory, which means the following: (1) Choose a…
astro_advanced

Learn Advanced Astrophotography Tips

/
2 Comments
 "I’ve tried astrophotography and want to know how to improve."Here’s where I assume you are contemplating the purchase of a tracking…
astro_inter

Learn Intermediate Astrophotography Tips

/
2 Comments
  Level 2: I know how to use a camera, what do I need to know for astrophotography? Image processing methods used to reduce background and noise…
astro_intro

Introduction to Astrophotography for Beginners

/
1 Comment
 For this Insight series (3 total), I assume that either you are using a camera (with an attached lens) or you already know how to attach…
davidhestenes

Interview with Physicist David Hestenes

/
14 Comments
For those who don't know the great David Hestenes, he is the inventor of the geometric algebra formalism of physics. Here we go! 1) What is the best application…

Interview with Science Advisor DrChinese

/
6 Comments
We are pleased to share with you an interview with PF Science Advisor and one of our founding members: DrChineseWho is DrChinese and share some early…
govandteachers

Blaming Government for Teacher and Scientist Failures in Integrity

/
46 Comments
The article, "Governmental policy is wrecking science," makes some interesting points but is fundamentally in error, because government policy is only…
cubicfunction

Learn How to Solve the Cubic Equation for Dummies

/
5 Comments
Everybody learns the "quadratic formula" for solving equations of the form [itex]A x^2 + B x + C = 0[/itex], even though you don't really need such a formula,…
digitalcamera3

Digital Camera Buyer’s Guide: Bridge Cameras

/
5 Comments
This article is geared towards:I've never owned a camera, but I want to get a 'real' camera (that doesn't cost too much). I've owned an entry-level…
rollingmotion

Learn The Basics of Rolling Motion

/
50 Comments
Although rolling wheels are everywhere, when most people are asked "what is the axis of rotation of a wheel that rolls without slipping?", they will answer…
davidgriffths

Interview with Physicist David J. Griffiths

/
35 Comments
We are pleased to introduce David J. Griffiths. Professor Griffiths is one of the most successful physics textbook writers.  Odds are if you studied…
quantumparticle

Spectral Standard Model and String Compactifications

/
28 Comments
 The Connes-Lott-Chamseddine-Barrett model is the observation that the standard model of particle physics -- as a classical action functional,…
digitalcamera2

Ultimate Digital Camera Buyer’s Guide: Compacts, DSLR and Tripods

/
2 Comments
Introduction First, congratulations! Camera technology has advanced to the point where a complete novice, using an entry-level camera right out of the…
cmbprimer4

A Poor Man’s CMB Primer: Cosmic Acoustics

/
1 Comment
 Before decoupling, photons and charged particles were in good thermal contact: though the primordial plasma might have varied in temperature…
digitalcamera1

Digital Camera Buyer’s Guide: Introduction

/
75 Comments
 First, congratulations! Camera technology has advanced to the point where a complete novice, using an entry-level camera right out of the…
spacetimecon

Struggles with the Continuum: Spacetime Conclusion

/
4 Comments
 We've been looking at how the continuum nature of spacetime poses problems for our favorite theories of physics --- problems with infinities.…
11dgravity

11d Gravity From Just the Torsion Constraint

/
17 Comments
 It is familiar that Einstein gravity may be formulated in terms of a vielbein field together with a "spin connection", subject to the constraint…
spacetime7

Struggles with the Continuum: General Relativity

/
2 Comments
 Combining electromagnetism with relativity and quantum mechanics led to QED. Last time we saw the immense struggles with the continuum this…
namethephoto

Name the Science Photo Quiz

/
16 Comments
Summer is almost over, but the fun doesn't have to stop! Take a look at the photos below and see if you can identify them.  Post your score in the comment…
ohmslaw

Learn Why Ohm’s Law Is Not a Law

/
41 Comments
At first, I wanted this title to say “Ohm’s law is not a Law.”  But someone else used that phrase in a recent PF thread, and a storm of protest…
carcapacity

Why Road Capacity Is Almost Independent of the Speed Limit

/
29 Comments
Let us start with a familiar situation. Take a familiar part of a road, for example, the one from your home to work. How long will it take you to drive…
quantumhard

Why Is Quantum Mechanics So Difficult?

/
254 Comments
Quantum Mechanics Key points:Quantum mechanics (QM) is often perceived as difficult, especially by non-physicists. The difficulty lies in the…
introphysics

So I Am Your Intro Physics Instructor

/
14 Comments
I posted this elsewhere (on my blog), and someone mentioned that maybe it might also be useful here on PF. So I'm reproducing the entire entry here in…
entropy

How to Determine the Change in Entropy

/
9 Comments
How do you determine the change in entropy for a closed system that is subjected to an irreversible process?Here are some typical questions we get…
Supersymmetry

Learn About Supersymmetry and Deligne’s Theorem

/
54 Comments
 In 2002, Pierre Deligne proved a remarkable theorem on what mathematically is called Tannakian reconstruction of tensor categories. Here…
Schwarzschild

Learn Orbital Precession in the Schwarzschild and Kerr Metrics

/
7 Comments
The Schwarzschild Metric A Lagrangian that can be used to describe geodesics is [itex]F = g_{\mu\nu}v^\mu v^\mu[/itex], where [itex]v^\mu = dx^\mu/ds[/itex]…
spacetimetetrad

Learn About Tetrad Fields and Spacetime

/
1 Comment
A spacetime is often described in terms of a tetrad field, that is, by giving a set of basis vectors at each point. Let the vectors of the tetrad be denoted…
LHC4

LHC Part 4: Searching for New Particles and Decays

/
17 Comments
 The LHC experiments are in full swing collecting data this year (more information in the forum), and a while ago the collaboration of the…
acusticbeats

Acoustic ‘beats’ from Mismatched Musical Frequencies

/
11 Comments
Introduction In late high school physics courses and first-year university courses, the phenomenon of acoustical 'beats' (digital audio) is often covered.…
omissionguage

Omissions in Mathematics Education: Gauge Integration

/
31 Comments
The current (pure) mathematics curriculum at the university is well-established. Most of the choices made are sensible. But still, some important topics…
polymer

Polymer Physics and Genetic Sequencing

/
4 Comments
Polymer Key PointsDNA is a good model system for polymer physics as it is small enough to observe single-molecule dynamics and large enough to be…

Learn About Relativity on Rotated Graph Paper

/
15 Comments
This Insight is a follow-up to my earlier tutorial Insight (Spacetime Diagrams of Light Clocks). I gave it a different name because I am placing more…
Brachistochrone

Explaining the General Brachistochrone Problem

/
3 Comments
Consider a problem about the curve of fastest descent in the following generalized statement. Suppose that we have a Lagrangian system $$L(x,\dot x)=\frac{1}{2}g_{ij}(x)\dot…
qualitycontrol

Reflections on Technology Product Quality

/
6 Comments
On Hardware Quality It is impossible to test quality into a product. Quality must be designed into the product.The hardware designer is always responsible…
integralmisconceptions

Some Misconceptions on Indefinite Integrals

/
40 Comments
Integration is an incredibly useful technique taught in all calculus classes. Nevertheless, there are certain paradoxes involved with integration that…