PhD in general relativity (1987), researching foundations of physics since 1994. Coauthor of “Beyond the Dynamical Universe” (Oxford UP, 2018) and "Einstein's Entanglement" (Oxford UP, 2024).
In her YouTube video Bell’s Theorem Experiments on Entangled Photons, Dr. Fugate shows how polarization-entangled photons violate Bell’s inequality. In this Insight, I will use quantum information theory to explain why such entangled photon-polarization qubits violate the version of Bell’s inequality due to John Clauser, Michael Horne, Abner Shimony, and Richard Holt known as the…
Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated: Before we end, let’s now briefly talk about the birth of quantum information science, a pivotal shift that began in the 1990s. This is the era when researchers…
Comment on PBS Space Time video PBS Space Time produces some very good videos on the foundations of quantum mechanics (QM), so let me comment on their video What If Physics IS NOT Describing Reality to provide (crucial) missing information. This comment pertains only to the first 9 min of the video, i.e., it has…
The concept of quantum superposition (or superposition for short) is very counterintuitive, as Schr##\ddot{\text{o}}##dinger noted in 1935 writing [1], “One can even set up quite ridiculous cases.” To make his point, he assumed a cat was closed out of sight in a box with a radioactive material that would decay with 50% probability within an…
In Chapter 37 of “The Feynman Lectures on Physics Volume 1,” Richard Feynman famously wrote that the mystery of wave-particle duality in the double-slit experiment is: a phenomenon which is impossible, absolutely impossible to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only…
Superdeterminism as a way to resolve the mystery of quantum entanglement is generally not taken seriously in the foundations community, as explained in this video by Sabine Hossenfelder (posted in Dec 2021). In her video, she argues that superdeterminism should be taken seriously, indeed it is what quantum mechanics (QM) is screaming for us to…
This Insight is a condensed version of No Preferred Reference Frame at the Foundation of Quantum Mechanics. Reference numbers here correspond to that paper. This Insight is an expanded version of Quantum information theorists produce new ‘understanding’ of quantum mechanics. Feynman famously said, “I think I can safely say that nobody understands quantum mechanics” [1]. Despite…
I have written many Insights (and coauthored an entire book) explaining how the puzzles, problems, and paradoxes of modern physics can be attributed to our dynamical bias and resolved by rising to Wilczek’s challenge [1]: A recurring theme in natural philosophy is the tension between the God’s-eye [4D] view of reality comprehended as a whole…
All undergraduate physics majors are shown how the counterintuitive aspects (“mysteries”) of time dilation and length contraction in special relativity (SR) follow from the light postulate, i.e., that everyone measures the same value for the speed of light c, regardless of their motion relative to the source (see this Insight, for example). And, we can…
In Part 1 of this 3-part series, I explained kinematics in Einstien-deSitter (EdS) cosmology and in Part 2, I explained kinematics in ##\Lambda##CDM cosmology (essentially EdS plus a cosmological constant ##\Lambda##). Now I will bring those models to bear on the Supernova Cosmology Project (SCP) Union2.1 type Ia supernova data. This will show clearly how…
This is Part 2 of a 3-part series explaining evidence for so-called “dark energy” leading to a current positive cosmological acceleration. The evidence comes from fitting the SCP Union2.1 type Ia supernova data which indicates the existence of a cosmological constant ##\Lambda## (read “Lambda”, thus ##\Lambda##CDM is sometimes written LCDM) in Einstein’s equations (EEs) of…
In this 3-part series, I want to motivate the (re)introduction of the cosmological constant ##\Lambda## into Einstein’s equations of general relativity (GR) per the Supernova Cosmology Project (SCP) Union2.1 type Ia supernova data. As you probably know, this discovery won Perlmutter, Schmitt, and Riess the 2011 Nobel Prize in Physics “for the discovery of the accelerating…
Note: This Insight was previously titled, “Answering Mermin’s Challenge with Wilczek’s Challenge.” While that version of this Insight did not involve any particular interpretation of quantum mechanics, it did involve the block universe interpretation of special relativity. I have updated this Insight to remove the block universe interpretation, so that it now answers Mermin’s challenge…
In a recent thread, I outlined how to compute the correlation function for the Bell basis states \begin{equation}\begin{split}|\psi_-\rangle &= \frac{|ud\rangle \,- |du\rangle}{\sqrt{2}}\\ |\psi_+\rangle &= \frac{|ud\rangle + |du\rangle}{\sqrt{2}}\\ |\phi_-\rangle &= \frac{|uu\rangle \,- |dd\rangle}{\sqrt{2}}\\ |\phi_+\rangle &= \frac{|uu\rangle + |dd\rangle}{\sqrt{2}} \end{split}\label{BellStates}\end{equation} when they represent spin states. The first state ##|\psi_-\rangle## is called the “spin singlet state” and it…
People often claim on Physics Forums and in the foundations community proper that quantum mechanics is “incomplete.” Indeed, Lee Smolin recently wrote [1, p. xvii]: I hope to convince you that the conceptual problems and raging disagreements that have bedeviled quantum mechanics since its inception are unsolved and unsolvable, for the simple reason that the…
In this Insight I will introduce the quantum mystery called “Wigner’s friend” using Healey’s version [1] of Frauchiger and Renner’s (FR’s) version [2] of Wigner’s version [3]. As with much of physics, the explication becomes more succinct and comprehensible with each successive rendering. I will show how this mystery results from treating classical information (behaving…
In this Insight, I will show how the Popescu-Rohrlich (superquantum) correlations provide an unreasonable advantage in a particular “quantum guessing game” using a pedagogical counterpart from the book “Totally Random: Why Nobody Understands Quantum Mechanics” by Tanya Bub and Jeffrey Bub (Princeton University Press, 2018). As I showed in my Insight Why the Quantum, the PR correlations violate…
Wheeler’s opening statement in his 1986 paper, “How Come the Quantum?” holds as true today as it did then [1] The necessity of the quantum in the construction of existence: out of what deeper requirement does it arise? Behind it all is surely an idea so simple, so beautiful, so compelling that when — in…
A Short Proof of Birkoff’s Theorem derived the Schwarzschild metric in units of ##G = c = 1##: \begin{equation} ds^2 = -\left(1 – \frac{2M}{r}\right)dt^2 + \left(1 – \frac{2M}{r}\right)^{-1}dr^2 + r^2d\theta^2 + r^2 \sin^2\theta d\phi^2 \label{metric} \end{equation} and I used that metric in The Schwarzschild Metric: Part 1, GPS Satellites to show that Global Positioning System (GPS) clocks…
A Short Proof of Birkoff’s Theorem derived the Schwarzschild metric in units of ##G = c = 1##: \begin{equation} ds^2 = -\left(1 – \frac{2M}{r}\right)dt^2 + \left(1 – \frac{2M}{r}\right)^{-1}dr^2 + r^2d\theta^2 + r^2 \sin^2\theta d\phi^2 \label{metric} \end{equation} and I used that metric in The Schwarzschild Metric: Part 1, GPS Satellites to show that Global Positioning System (GPS)…
A Global Positioning System (GPS) device gives your precise location by receiving light pulses from satellites with synchronized clocks then triangulating your location based on that information [1]. Since light travels at 300 million meters per second, your location will be off by about 1 meter if the clock times are off by only…
In an Insights series “Blockworld and its Foundational Implications,” I quoted Huw Price and Ken Wharton in several places advocating a blockworld approach to physics (called the Lagrangian Schema[1]). While Ken did sign off on my use of these quotes, I wasn’t entirely fair to the Price & Wharton program because I didn’t reveal their…
In parts 1 and 2 of this 5-part Insights series, I explained the blockworld (BW) implication of special relativity. In part 3, I introduced general relativity (GR) and brought BW to bear on general relativistic cosmology to ‘explain’ what puzzles so many people about big bang cosmology, i.e., the origin of the universe. The bottom…
In parts 1 and 2 of this 5-part Insights series, I explained the blockworld (BW) implication of special relativity (SR). In part 3, I introduced general relativity (GR) and brought BW to bear on general relativistic cosmology to ‘explain’ what puzzles so many people about big bang cosmology, i.e., the origin of the universe….
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 BW perspective nicely with this quote[1]: There is no dynamics within space-time itself: nothing ever moves therein; nothing happens; nothing changes. In particular, one does not think of particles as…
In part 1 of this 5-part Insights series, I introduced two consequences of the second postulate of special relativity (SR): time dilation (“moving clocks run slow”) and length contraction (“moving objects shrink”). Since moving clocks run slow, if you and observers at rest with respect to you (hereafter simply “you”) see me moving, you…
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 (origin of the universe), paradoxes[1] (of closed timelike curves), and conundrums[2] (of quantum nonlocality) that I have seen discussed on Physics Forums. Blockworld (BW) says the past, present and future are equally ‘real’, i.e.,…
In a previous Insight, Weak Values Part 1: “Asking Photons Where They Have Been,” I showed different methods for computing the relative intensities in the weak measurements done by Danan, Farfurnik, Bar-Ad, and Vaidman (DFBV)[1]. In that experiment, DFBV had a weak transverse signal, created by mirrors oscillating with small amplitudes transverse to the beam path through an interferometer, piggyback…
In a previous Insight on retrocausality, I explained an experiment by Danan, Farfurnik, Bar-Ad, and Vaidman (DFBV)[1], “Asking Photons Where They Have Been” using various retrocausal models. In this Insight, I will give a brief introduction to the formalism for computing the relative power spectra in that experiment. Specifically, I will show how the weak…
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 nontechnical arguments against “instruction sets” aka “counterfactual definiteness” for quantum mechanics (QM). In the case of the Mermin device, Elitzur & Dolev showed a particular experimental instantiation yielded a quantum counterpart to…
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] without requiring the formalism of quantum mechanics (QM). I will summarize that argument then show how the QM formalism fits his results and how his device is instantiated in Elitzur & Dolev’s quantum liar experiment (QLE)[3]. The quantum state…