Astrophysics / Physics / Relativity

The Curvature of Spacetime

Abell 2218

Spacetime is curved. We’ve all heard the line. But what does it mean? Well on the largest scales, the curvature of spacetime is abundantly clear as the warped fabric of the universe distorts images of distant objects. The image below is of the Abell 2218 galaxy cluster, taken by the Hubble Space Telescope. The cluster is very massive so it warps the spacetime around it. This warped spacetime acts as a lens so that light light coming from galaxies behind Abell 2218 is spread out much more than it should be. The result is that images of galaxies behind

Astrophysics / Physics / Relativity / etc.

Simulating Gamma Ray Bursts

It was the mid 1960s. The United States and the Soviet Union had recently signed the Partial Nuclear Test Ban Treaty, which forbid the detonation of nuclear weapons except underground. Since neither nation trusted the other, each was carefully monitoring the other for non-compliance. In particular, the United States feared that the soviets might be, I kid you not, testing bombs behind the moon. Vela The United States solved this problem with the Vela satellites. When a nuclear bomb goes off, it emits a short burst of gamma rays, which are rays of extremely high energy light. The Vela

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

Astrophysics / Physics / Science And Math

Pope Francis says Evolution and the Big Bang are Compatible with Catholicism

You’ve probably heard, the news. Pope Francis has announced that Big Bang cosmology and evolutionary theory are compatible with Catholicism and “may even be required.” This is, of course, wonderful news. It’s evidence that science and religion are not necessarily incompatible and that people of faith can modify their beliefs based on the evidence around them. But it should have been this way all along. Indeed, it originally _was_ this way. One of the people who developed Big Bang cosmology, Monseigneur Georges Henri Joseph Édouard Lemaître was a catholic priest who believed that his studies of physics brought him

Astrophysics / Physics / Science And Math

How Planets Form

The Heavenly Spheres make music for us, The Holy Twelve dance with us, All things join in the dance! Ye who dance not, know not what we are knowing ~Gustav Holst By the sweat of your brow you will eat your food until you return to the ground, since from it you were taken; for dust you are and to dust you will return. ~Genesis 3:19 Many months ago, Richard Green posted an article on Google+ that described how life on a toroidal planet would work. The discussion in the comments eventually led to speculation as to whether or

Astrophysics / Physics / Science And Math

Why Black Holes Glow: Accretion Disks

The patient accretion of knowledge, the focusing of all one’s energies on some problem in history or science, the dogged pursuit of excellence of whatever kind these are right and proper ideals for life. ~Michael Dirda Nothing can escape from a black hole, not even light. This is why we call them “black.” One would imagine, then, that black holes are black invisible menaces, lurking out in the depths of space. Surprisingly, though, black holes glow. The cover image shows a radio photograph of the center of the Milky Way. The center glow, Sagittarius A, is partly due to