On Friday I was involved in an interesting conversation in an unusual format. It was a chat with cosmologist Anthony Aguirre at UCSD, and it was all about research in aspects of cosmology and of string theory, touching on issues such as the nature of quantum […] Click to continue reading this post
Tomorrow is the Big Day. For what? The launch of Planck and Herschel – Major new windows on our universe. Keep your fingers crossed for luck!
They’re on the launch pad right now. See here.
So, what are the missions and objectives of these fine spacecraft, I hear you ask.
Well, from the Planck site: […] Click to continue reading this post
I had a lot of fun at this year’s Jet Propulsion Laboratory (JPL) open house. I’m happy to report that there were, once again, lots of people wandering around looking at the displays and demonstrations, asking questions, hanging out, and so forth, and an impressive turnout of JPL staff answering questions and being very enthusiastic about the science (something which is easy to do because it’s such an excellent topic!). I’ve made a video for you that is coming up at the end of this post. (Click on stills for larger views.)
There was the usual huge emphasis on planetary exploration with rovers and robots and so forth – this seems to capture the imagination of everyone, so why not? – but I was more than a little surprised to find virtually no showing for the Planck mission. There was one poster somewhere, but no booth, no model, no description of the truly amazing science that it will do in unlocking more about the origins of the entire […] Click to continue reading this post
Take a cruise through the universe (a simulated one) over time:
Was using this video in a cosmology class the other day (given to a group of […] Click to continue reading this post
While most of the episodes of the History Channel’s The Universe series are firmly about scientific knowledge of the universe that has been tested and verified (from planetary science, to solar physics, to stellar evolution, and various topics in cosmology, and so forth), they also like to treat topics that have a higher component of more speculative material. This is of course fine, as long as it is made clear what is speculation, and what is established. Recall that I took part in a really fun episode called Cosmic Holes, which talked about white holes and wormholes -entirely speculative objects – right alongside the physics of black holes, objects that we know are physically realized in our universe. (See here, here, and here.) I think that Laura Verklan, the writer/director, did a really excellent job of separating out the speculative from the established. Similar things can be said for the episode Cosmic Apocalypse, done by writer/director Savas Georgalis (see here), which focused on scenarios about how the universe might end, given what we have already established about how it was in early times and how it is now.
I’m hoping that the upcoming (tonight!) episode entitled Parallel Universes will also be a nice and clear piece of work discussing the speculative ideas concerning the possibility of parallel universes – what the ideas are, why it is a fun idea, what it […] Click to continue reading this post
On campus yesterday, I ran into a colleague I had not seen in a long time. She was with her daughter. She introduced us, saying, among other things, that Professor Johnson is “Big in Cosmology”.
I’ll admit that I giggled like a naughty schoolgirl for a longish, unprofessorial moment. It was sort of hard to explain, and would have derailed the conversation, so I did not try. Why was I giggling? Well, it is just that the field of cosmology (which, for the record, […] Click to continue reading this post
Well, the new orbiting instrument, GLAST (Gamma-ray Large Area Space Telescope – launched June 11th this year) has passed all its tests with flying colours, apparently, and is working well. NASA has now renamed the craft the Fermi Gamma-ray Space Telescope, after Enrico Fermi. There’s a press release here.
The craft is a wonderful combination of the fields of particle physics, astrophysics and cosmology, and will teach us so much about the universe (such as the nature of dark matter), and so it is exciting to hear that it all on track.
Excitingly, they’ve also released images of the early results of the observations, and you can read more about them in the press release too. Here’s a sky map made from the observations.
Some words from the release: […] Click to continue reading this post
Good news everyone! GLAST has been launched successfully. GLAST stands for Gamma-ray Large Area Space Telescope, and it does exactly what it says on the packet. It is an instrument designed to look more closely at gamma rays from outer space. More here. It will help (alongside other instruments such as SWIFT) get better understanding of a wide range of gamma-ray emitting objects, that pertain to a wide range of issues, astrophysical to cosmological.
“Gamma ray bursters” are obvious super-powerful sources of gamma rays out there, largely due to macroscopic astrophysical objects (collapsed stars or stars in the process of doing so, or merging with each other – see earlier posts) doing violent things, or interacting violently with their surroundings. So are active galactic nuclei, powered by black holes. We’d like to better understand all of the processes that allow these objects to generate gamma rays.
Other sources could include particles and antiparticles annihilating each other and (by […] Click to continue reading this post
Well, you’ve probably guessed that I’ve been somewhat distracted for several days. In fact, my main focus for the past week has really been on computer issues, frustratingly. I’ll give you the blow by blow later, I hope, but the last couple of days have been the most frustrating of all, and so I’ve not been dealing with much else, including blogging. Part of that is actual logistics – some of the things I wanted to post are on the afflicted computer – and some just the sheer annoyance of not having solved the issues driving me to do something totally non-computer related like going for a hike or seeing a movie.
So tonight i think I have a new theory – well, hypothesis- of what’s wrong, after a good deal of the day spent on detective work. It is a conjecture that is supported only by […] Click to continue reading this post
Hey, guess who was at Griffith Observatory recently? Brian May! He’s that astrophysicist who took some time off to play (excellent) guitar and compose songs in the band called Queen. Ring any bells? (I found the nice photo here.) So why was he in town? Well, a slightly giggly (but always great) Madeline Brand (of the NPR program “Day To Day”) went along to interview him, and you can listen to the interview here, and read a transcript, as well as see extracts from him book (written with Patrick Moore and Chris Lintott), charmingly and blatantly (but knowingly?) unrealistically called “Bang! The Complete History of the Universe”. I actually looked through it in a bookstore the other day – looks rather nice. Wonderfully produced and I read some well-written passages, so might be worth picking up if you’re looking for a fresh read about the universe.
As a side note, I was a huge fan of his during my middle to late teenage years and early 20s, and […] Click to continue reading this post
That’s it. The class is over… I have to admit that I’m pretty sad to see the end of it, although I’m very very tired. It was such a great group. (I’ll be toasting the end of it all with some of the splendid stuff to the right.)
Recall that we stepped away from black holes. After a look at cosmology for some lectures, where we understood the role of four crucial components in determining a universe’s properties (curvature, matter, radiation, and vacuum energy) we dove back into formalism for a short while (one lecture) to develop a little more the tools we needed to properly under stand how to formulate Einstein’s field equations.
It did not take long… You need only the idea that it makes sense to formulate everything in terms of objects that allow you to express the full sense of an equation in any coordinate system you care to write. Once that is done (the objects are called tensors, and the idea and how they work is pretty simple to get to grips with) the key to formulating the field equations of gravity is to have a look at the structure of other familiar systems. The field equations of electromagnetism (Maxwell’s equations) and the field equations for Newton’s formulation of gravity give the required clues. A rummage around the geometry to find the appropriate object to express the physics in terms of uncovers the Riemann tensor and its cousins (“contractions” to get Ricci and so forth), and you’re almost there. A step back to learn how to package energy […] Click to continue reading this post
Wow, doesn’t time fly when you’re having a busy semester! I meant to tell you about this early March shoot a while back, but got swamped and it fell off the desk. I recalled that I’ve been neglectful because I learned that the show in which some of this will be used will air on Tuesday night (9:00pm I think – “The Universe” on the History Channel). The episode discusses the end of the universe, as far as I know. The point is to discuss the various speculations that have been made about how the universe might end, and what current knowledge (such as the famous 1998 supernova observations showing that the universe’s expansion is accelerating) seems to suggest about which of those scenarios might be more likely. Of course, for the discussions to make sense, you need someone to talk about some of the basics, such as what it means for the universe (indeed, the whole of spacetime) to expand and collapse. Who you gonna call? 
Ok. I’m one of many you can call. It was a new (to me) producer/writer, Savas Georgalis, who called this time, and we worked together on plans about how we might […] Click to continue reading this post
As you may recall from the post I did some time ago, the “Light Cone” is a rather important concept in physics, and keeping track of it in a given physical scenario is an extremely important tool and technique for understanding many physical situations. (I urge you to review that post before continuing reading this one.)
One way to understand a most important concept – the event horizon – is by keeping track of lightcones, and so let’s go ahead and explore that here. The outcome is that […] Click to continue reading this post
I don’t mean that in a bad way. It is what it is. Quite varied and wonderful, our universe is, with unexpected features I don’t think many would have guessed at not long ago (like the fact that we only understand what about 4% of it is!! Crazy, in a […] Click to continue reading this post
Not long ago David Morrison (UCSB) came to the mathematics department here at USC to give a colloquium.
This was a treat for me for many reasons. Here are three:
