Astrophysics / cosmology / Physics / etc.

Dark Energy, Numerical Relativity, and Astrophysics

binary neutron star merger

So I did an interview for the “Tilting at the Universe” podcast. In it, I describe: the history of dark energy and the expanding universe, how the mystery of dark energy may be solved once we reconcile quantum mechanics and general relativity, how the astrophysics of black holes and neutron stars may help us understand quantum gravity, and how my field of numerical relativity fits in to all of this. I think I did a pretty good job of explaining what excites me about the field. So check it out. The interview is here. In the interview, I mention

cosmology / Physics / Science And Math

The CMB Axis of Evil and the Nature of Randomness

axis of evil planck

This Halloween, Nature News released an article titled Zombie Physics: 6 Baffling Results that Just Won’t Die. It’s a fun article describing several mysteries in physics whose solution sits in a sort of limbo. For fun, I figured, I’d explain some of these mysteries, and give my opinion about possible solutions. And first, I’m going to discuss the CMB Axis of Evil, a strange pattern in the leftover radiation from the Big Bang. A Much-Too-Short Summary of Cosmic Inflation and the CMB About 13.8 billion years ago, the universe was extremely hot, so hot that matter couldn’t form at

Astrophysics / cosmology / Physics / etc.

The Universe Is an Inside-Out Star

the CMB on our sky

No, not really. But as we’ll see, it’s a useful analogy. Today we’ll learn about sound waves in the sun and how, if we imagine that the universe is the sun but inside-out, these are the same as the sound waves that filled the early universe. DISCLAIMER: This is a pedagogical exercise only! I am not claiming the universe is ACTUALLY an inside-out star or that scientists think of it as one. Sound Waves in the Sun I’m sure you won’t be surprised when I say that the sun is a complicated beast. A nuclear furnace burning at tens

Condensed Matter / cosmology / Physics / etc.

BICEP2, Primordial Gravity Waves, and Cosmic Inflation

“Like the microscopic strands of DNA that predetermine the identity of a macroscopic species and the unique properties of its members, the modern look and feel of the cosmos was writ in the fabric of its earliest moments, and carried relentlessly through time and space. We feel it when we look up. We feel it when we look down. We feel it when we look within.” ~Niel Degrasse Tyson There was some very big news today! If you haven’t already heard, the BICEP2 research group at Harvard has found evidence of ancient gravitational waves in the sky. A lot

cosmology / Discrete Math / Geometry / etc.

Quantum Geometry: Causal Dynamical Triangulations

An example causal triangulation

A “quantum gravity expert” is presumably someone well acquainted with the details of our immense ignorance of the subject. I suppose I count. ~John Baez I long ago promised that I would discuss some of my own research. Here’s the first post that makes good on that promise. Today I’ll discuss a theory of quantum gravity. Why Quantum Gravity? Without a doubt, the two greatest advances in physics in the last 120 years were the advent of general relativity and quantum mechanics. These two amazing theories have totally changed the way we see the world. Quantum mechanics describes the

cosmology / Physics / Relativity / etc.

Fixing the Early Universe: Cosmic Inflation

A brief history of time, as Hawking would say.

Expansion means complexity and complexity decay. ~Cyril Northcote Parkinson This is part three of a series on the early universe. In the first article, I described the history of the Big Bang theory and why we believe the universe started in a colossal explosion. In the second article, I described some inconsistencies in the Big Bang theory that need correcting. Now I’ll explain how the theory of cosmic inflation addresses these inconsistencies and why we might believe it in inflation. This explanation will use ideas from quantum mechanics and general relativity; you can find my articles on these subjects

cosmology / Geometry / Mathematics / etc.

A Mess of Cosmic Coincidences: Problems With the Big Bang Theory

Awe! She's so cute!

The furthest bodies To which man sends his Speculation, Beyond which God is; The cosmic motes Of yawning lenses. ~Robert Frost, I Will Sing You One-0 I apologize for the long time of silence! I graduated from the University of Colorado about a month ago and was immediately assaulted by a huge amount of family affairs… and then caught up in moving. Sorry about this, everyone! My regular Sunday update schedule should resume next week. Last time, I described the theory of the Big Bang. I gave some history of the theory, and some reasons for why we believe

cosmology / Physics / Relativity / etc.

Always Walk Away From An Explosion—The Story of the Big Bang


We were fortunate to be there a day or two before ‘the big bang’ and then we got the heck out of town. ~Scotty Moore A few weeks ago, +Matthew Villaneuva asked the following question on Google+: Does anybody else find the Big Bang (the scientific explanation on how the universe got created) weird? Actually, yes! Just a century ago, everyone believed that the universe was static—i.e., that it had always existed and that it would always continue to exist. Even Albert Einstein held this view. I previously explained why we know the universe is expanding, so I’m going

cosmology / Geometry / Mathematics / etc.

Receding Horizons: Dark Energy and the Expanding Universe

Einstein and Hubble

Astronomy compels the soul to look upwards and lead us from this world to another. ~Plato The history of astronomy is a history of receding horizons. ~Edwin Powell Hubble Last week, I discussed the possible shapes our universe could take. I offhandedly mentioned that not only is the universe expanding, but that that expansion is accelerating. We attribute this expansion to a mysterious phenomenon we call dark energy. This week, I want to explore the history of this idea and the beautiful experiments that tell us all is not as it seems. The Static Universe and Einstein’s Greatest Blunder

cosmology / Geometry / Mathematics / etc.

For There We Are Captured—The Geometry of Spacetime

All about me there are angles— strange angles that have no counterparts on the earth. I am desperately afraid. ~Frank Belknap Long, The Hounds of Tindalos Whoever…proves his point and demonstrates the prime truth geometrically should be believed by all the world, for there we are captured. ~Albrecht Durer I was recently asked: What does it mean when we say spacetime is “curved” or “flat?” The answer lies in the interface between differential geometry and physics. This is the latest in many articles I’ve written on Einstein’s relativity, so you might want to check out my series on faster-than-light