If you’ve ever observed the stars in a clear dark sky, you likely remember it. Most people don’t live in areas where the sky is very dark, so it isn’t something they experience often. But when they do, it seems to have an impact on their lives. Often people will talk about their first experience of a sky filled with stars in almost hushed tones. It is a view that seems to invoke a sense of awe and wonder in all of us.
Trust Me, I’m a Scientist
When I was in graduate school, a friend of mine asked about my research. I was studying aspects of black holes in the early universe, so I explained a bit about black holes, the big bang and such in broad terms. Afterwards she shook her head and responded: “Bull poopy.” Our conversation went for a bit longer, with her arguing that I couldn’t possibly know what I was claiming to be true, and me trying to explain how I knew these things, but it was clear that opinions wouldn’t change. The simple fact was that she didn’t trust me. I was either confused or lying, so nothing I said could possibly change her mind.
Copy Pasta
Something is amiss in the universe. There appears to be an enormous deficit of ultraviolet light in the cosmic budget. Or, so I’m told. I was asked by a few readers about a new study showing there is less light in the universe than expected. They heard of this from various articles showing up on the web. Like this one …
A Lack of Balance
Yesterday I wrote about the difficulty in understanding black holes. The heart of this difficulty lies in trying to understand how two radically different physical models (general relativity and quantum mechanics) might integrate into a single, unified model. Two major approaches to this problem are loop quantum gravity and string theory.
Down the Rabbit Hole
Black holes are interesting objects, because we know they exist but we don’t know what they are. That isn’t quite true. We know that they are formed from the gravitational collapse of matter, either as supermassive black holes in the centers of galaxies, or as stellar mass black holes from the collapse of a star. We know that they power quasars and radio galaxies, that they can form accretion disks of matter around their equators, and that they can produce powerful jets of matter when they are active. But buried within our understanding of black holes is a fundamental contradiction that we have yet to resolve.
Too Quiet
In the big bang model, the universe began about 13.8 billion years ago as a hot, dense state. There’s plenty of observational evidence to support this model. One strong bit of evidence is the cosmic microwave background (CMB). It is the thermal remnant of the primordial fireball, cooled now to a temperature of about 2.7 K. What’s amazing about the CMB is how perfectly it light matches that of a blackbody. It is exactly what you would expect to see from a primordial universe of uniform temperature. But that also raises a bit of a mystery, because the CMB is actually more uniform that it should be.
Still in the Dark
Dark matter has an interesting history. It was first proposed to account for the fact that stars in our galaxy move much faster than they should around the galactic core. Evidence of dark matter has been seen in galactic collisions like the Bullet Cluster, as well as through gravitational lensing by galaxies. On the other hand, we have yet to find any direct detection of dark matter particles. In fact, many of the likely candidates for dark matter have been all but eliminated. Then there is the puzzling aspect of dwarf galaxies.
Hot Topic
The structure of the Sun can be divided into three main parts: the interior, which consists of the core, radiative and convective regions; the photosphere, which is basically the surface of the Sun where light comes from; and the atmosphere, of which includes the corona. Since nuclear fusion occurs in the core of the Sun, it’s reasonable to assume that the core is the hottest part of the Sun. In fact we know the core is about 15 million K, and that as you move outward from the center the temperature drops, until you reach a temperature of about 5,800 K at the surface. One would expect that this cooling trend continues, so that the solar atmosphere is cooler than the surface. But what we observe is that the atmosphere, specifically the corona, gets hotter. Much hotter.
Achilles’ Heel
Achilles, so the story goes was a mighty Greek warrior. When he was born, his mother dipped him in the river Styx, rendering him invulnerable except for the heel by which he was held. It was that vulnerable heel that was Achilles’ undoing, when Paris killed Achilles by shooting an arrow through the vulnerable heel. It’s a story of how the mighty can be destroyed by a seemingly minor flaw. A cautionary tale, if you will.