Sam Kelly

[Sam Kelly @S_A_Kelly]

@PhysInHistory Simply beautiful

[Physics In History @PhysInHistory]

In 1928, the famously taciturn Paul Dirac was trying to write a version of the Schrödinger equation that respected special relativity. The equation he produced, now just called the Dirac equation, did something unsettling: for every solution with positive energy describing a normal electron, there existed a corresponding solution with negative energy.

In classical physics you'd just throw away the negative-energy solutions as unphysical. But quantum mechanics doesn't let you, particles would inevitably cascade down into them, releasing infinite energy. So Dirac made an audacious move. He proposed that the vacuum is actually an infinite sea of negative-energy electrons, completely filled, so that by the Pauli exclusion principle no other electron can fall in. Knock one out, and you leave behind a "hole" — which, viewed from the outside, looks like a particle with positive charge and the same mass as an electron.

This was the first prediction of antimatter, derived from nothing but the demand that the equations be consistent. Initially Dirac thought this hole was the proton, but Hermann Weyl pointed out that it would have to have the same mass as the electron. The existence of this particle, the positron, was confirmed experimentally in 1932 by Carl D. Anderson.

The mind-blowing part: a young man writing down what he considered the most beautiful equation he could think of was effectively told by the mathematics, "You forgot to mention that half the universe exists." And then it turned out to be true.

📷 Niels Bohr Archive, courtesy AIP Emilio Segrè Visual Archives

[Sam Kelly @S_A_Kelly]

Come on folks, we can do better!!
#highvalue #patientsfirst #Cardiology
https://t.co/HffPJ61uuL

[Journal of Cardiac Failure @JCardFail]

ICYMI - JCF Sim Pub from #HFSA2021 - "Subclinical myocardial injury and the phenotype of clinical congestion in patients with HFrEF"
By @MarkDrazner @JTThibs @JLGrodin et al
@robmentz @dranulala
https://t.co/ALLMK31Sdn

[JAMA Internal Medicine @JAMAInternalMed]

ICDs are integral in cardiac care, however, defibrillation at the #endoflife may not accurately reflect the patient's goal of care. This Teachable Moment highlights the necessity of evaluation of the ICD when having an end-of-life discussion https://t.co/JdFu6Ud0qF

[Sam Kelly @S_A_Kelly]

Sounds like the folks at #UTSW are doing some interesting work!

Need to check patient's jugular venous pressure? There's an app for that : Newsroom - UT Southwestern, Dallas, Texas https://t.co/HqieyZxguK via @utswnews #Cardiology #Telemedicine