Discovery Coincidence

chatter_sketch_arenaSome of you are wondering what I’m working on while on retreat. Well, actually there’s a nice coincidence here. I’m working on the graphic book that you may have heard me talk about a bit. “The Project” as I sometimes call it. I’ve been doing things on various aspects of it, such as reworking the description of it for various people to look at, writing new bits, and spending a bit of time pulling together various bits of the prototype story I used to start all of this back in 2010. The prototype bits have all of my experimentation and development of style and technique all over them, and so there are pages that needed a bit of rework (to say the least). So, on Monday, [...] Click to continue reading this post

Discovery Clarification

I’m actually in hiding and silence for a week. It is Spring Break and I have locked myself away in a seaside town to do some writing, as I did last year. But I must break my silence for a little while. Why? Well there’s been a really great announcement in physics today and while being very happy that it is getting a lot of press attention – and it should since the result is very important and exciting – I’ve been stunned by how confusingly it has been reported in several news reports. So I thought I’d say a few things that might help.

But first, let me acknowledge that there’s a ton of coverage out there and so I don’t need to point to any press articles. I will just point to the press release of the BICEP2 collaboration (yes, that’s what they’re called) here, and urge you once you’ve read that to follow the link within to the wealth of data (images, text, graphs, diagrams) that they provide. It’s fantastically comprehensive, so knock yourself out. The paper is here.

I keep hearing reports saying things like “Scientists have proved the Big Bang”. No. The Big Bang, while an exciting and important result for modern cosmology, is very old news. (You can tell since there’s even a TV comedy named after it.) This is not really about the Big Bang. This is about Inflation, the mechanism that made the universe expand rapidly from super-tiny scales to more macroscopic scales in fractions of a second. (I’ll say more about the super-tiny below).

I also hear (slightly more nuanced) reports about this being the first confirmation of Inflation. That’s a point we can argue about, but I’d say that’s not true either. We’ve had other strong clues that Inflation is correct. One of the key things that pops out of inflation is that it flattens out the curvature of universe a lot, and the various observations that have been made about the Cosmic Microwave Background over the years (the CMB is that radiation left over from when the universe was very young (about 380,000 years old – remember the universe is just under 14 million years old!)) have shown us that the universes is remarkably flat. Another previous exciting result in modern cosmology. Today’s result isn’t the first evidence.

So what is today’s exciting news about then? The clue to the correct [...] Click to continue reading this post

Collecting the Cosmos

i_2014_01_24_CollectCosmos_150x200Don’t forget that on the USC campus on Friday at 4:00pm, we’ll be kicking off the Collecting the Cosmos event! It will be in the Doheny library, and there’ll be a presentation and discussion first, and then a special opening reception for the exhibition. Be sure to get yourself on the waiting list since there’s some chance that you’ll get in even if you have not RSVPed yet. (The image is from the Visions and Voices event site, and includes parts of the artworks – by artists Victor Raphael and Clayton Spada – to be included in the exhibition, so come along and see.) The event description says, in part: [...] Click to continue reading this post

Big History is Coming!


You’ll recall that I was in New York a short while ago to film some promotional material for a new TV series. It is called Big History, and it will be on History Channel’s H2 channel (and eventually on various international channels, but I’ve no idea which – similar ones to where you find the other show I’ve mentioned a bit, The Universe, I expect).

Rather than be primarily about astronomical and cosmological things, the show will focus each week on one of a list specific items that have affected our history, and take the long view about that item. How long a view? The longest known possible! So take something like Salt, and examine its role in civilization and culture, bringing in historians, anthropologists, etc… and physical scientists to trace that object back to its roots in the early universe… (the big bang, the cores of stars, etc.) Update: For you Breaking Bad fans, note that it’ll be narrated by Bryan Cranston, by the way.

Here’s one of the promo videos:

[…] Click to continue reading this post

Weinberg on Physics Now

I just spotted (a bit late) that Steven Weinberg (one of the giants of my field) has written a piece in the New York Review ofBooks entitled “Physics: What We Do and Don’t Know”. I recommend it. He talks about astronomy, cosmology, particle physics, and by casting his eye over the arc of their recent (intertwined) histories of ideas, experiments and discoveries, tries to put the Standard Models of particle physics and of cosmology into perspective.

The article is […] Click to continue reading this post

TED Youth Talk – Hidden Structures of the Universe

cvj_TED_YouthYou might recall that last year I gave a talk at TED Youth, in their second year of short TED talks aimed at younger audiences. You’ll recall (see e.g. here and here) I made a special set of slides for it, composed from hundreds of my drawings to make it all in graphic novel style, and somehow trying to do (in 7 minutes!!) what the TED people wanted.

They wanted an explanation of string theory, but when I learned that telescopesI was the only person in the event talking about physics, I kind of insisted that (in a year when we’d discovered the Higgs boson especially!) I talk more broadly about the broader quest to understand what the world is made of, leaving a brief mention of string magnifytheory at the end as one of the possible next steps being worked on. Well, they’ve now edited it all together and made it into one of the lessons on the TED Ed site, and so you can look at it. Show it to friends, young and old, and remember that it is ok if you don’t get everything that is said… it is meant to invite you to find out more on your own. Also, as you see fit, use the pause button, scroll back, etc… to get the most out of the narrative.

I’m reasonably pleased with the outcome, except for one thing. WHY am I rocking [...] Click to continue reading this post

Known Unknowns Decreased a Bit

Well, the day is here. The Planck collaboration has announced a huge amount of results for the consumption of the scientific community and the media today. The Planck satellite looks with unprecedented precision at the very earliest radiation (“cosmic microwave background radiation”, CMB) from the universe when it was very young (a wee, cute 380,000 years old) and helps us deduce many things about what the universe was like then, and what it is like now. Here’s one of the representations of the universe using the new sky mapping Planck did (image courtesy ESA/Planck):

There’s a ton of data, and a raft of papers with analysis and conclusions. And there’s a very nice press release. I recommend looking at it. It is here, and the papers are here. The title of the press release is “Planck reveals an almost perfect Universe”, and some of the excitement is in the “almost” part. A number of anomalies that were hinted at by the previous explorer of the CMB, WMAP, seem to have been confirmed by Planck, and so there are some important things to be understood in order to figure out the origin of the anomalies (if they ultimately turn out to be real physics and not data artefacts). [Update: Andrew Jaffe has two nice posts I recommend. One on the science, and the other on the PR. Jester also has a nice post on the science from a particle physicist's perspective.]

What is the title of my post referring to? Well, the refined measurements have allowed us to update some of the vital statistics of the universe. First, it is a bit older than previous measurements have indicated. The age is now measured as 13.82 billion years. (I’m already updating pages in the draft of my book…) Second, the proportion of ingredients [...] Click to continue reading this post

Heaven’s Parameters

Oh… I forgot to get around to letting you know the result of designing the universe required in a previous post. The result is that it is a radiation (“light”) filled universe with positive cosmological constant \Lambda(and so space wants to expand due to negative pressure – much like ours seems to be doing). The radiation density wants the thing to collapse. There’s a balance between the two, and it turns out that it is when the two densities (radiation, and vacuum energy) are equal. This is only possible when there is positive curvature for the universe (so, not like ours), as you can see from the Friedman equation if you were that way inclined. So the universe is a 3-sphere, and if you work it out, the radius of this 3-sphere turns out to be a=\left(\frac{3}{2\Lambda}\right)^{1/2}. The temperature of the radiation is then computed using the usual Stefan-Boltzmann relation.

The equality of densities turns out to result from the fact that the effective potential of the equation is at a maximum, and so this universe turns out to be unstable… It is a radiation-filled version of Einstein’s matter-filled static universe, which is also unstable. It is larger than Einstein’s by a factor of \sqrt{3/2}.

Einstein was said to have arrived at his static universe on the grounds of what he thought was observationally clear – the universe was unchanging (on large scales). [...]
The equality of densities turns out to result from the fact that the effective potential of the equation is at a maximum, and so this universe turns out to be unstable… It is a radiation-filled version of Einstein’s matter-filled static universe, which is also unstable. It is larger than Einstein’s by a factor of \sqrt{3/2}.

Einstein was said to have arrived at his static universe on the grounds of what he thought was observationally clear – the universe was unchanging (on large scales). Hubble [...] Click to continue reading this post

Project Heaven

This is an extra homework that some students of the General Relativity class did to make up for one that did not count earlier in the semester. While writing it, I realized that this universe is in fact, Heaven! You know, we become beings of light, and live forever, etc…

I thought it would be fun to share its final form:

“You work in the design section of the company that manufactures universes. (This is [...] Click to continue reading this post

The 2011 Nobel Prize in Physics

Ok. So who was surprised by this one? My hand is not up… is yours? (That’s a screen shot from the Nobel Prize site to the left. More here. Cheeky of me, but it’s early in the morning and I’ve got to pack, shower, and cycle like mad to the subway to get to my train to Santa Barbara, so time is of the essence.)

I was pretty sure that this would be the prize sometime very soon, although I’ll not say that I knew it would be this year’s for sure. It is well deserved, since this was a genuinely major change in how everyone in the field thinks about the universe, and we’re still trying to get to grips with it today. The acceleration of the universe that they [...] Click to continue reading this post

Multiverse Musings

As you may know already there’ll be a new NOVA series on PBS in the Fall, based on one of Brian Greene’s books, The Fabric of the Cosmos. Last Fall I did some a shoot with them for my role in it (I’ve no idea how much they will use), and I learned a short while ago that they’ll be using some of it on the NOVA website too. They extracted some parts of the on-camera interview segments I did concerning the idea of multiple universes and transcribed them into something you can read online. Have a look here. I touch on the idea in a fragmented way, mostly being led by the questions I was asked, but it’s a fun topic to chat about, and may lead you in interesting directions should you wish to learn more, so have a look.

A word on the picture they are using (er…see above left). It seems to be one that the [...] Click to continue reading this post


We had a really interesting discussion of the quantum physics of de Sitter spacetime yesterday here in Aspen, starting with a review of the behaviour of scalar fields in such a background, led by Don Marolf, and then, after lunch, an open-ended discussion led by Steve Shenker. This is all quite difficult, and is of course quite relevant, since a piece of de Sitter is relevant to discussions of inflation, which seems (from cosmological observations) to have been a dominant phase of the very early universe. As the most symmetric space with positive cosmological constant, de Sitter may also be relevant to the universe today, since dark energy (first recognized after 1998′s observations of the universe’s accelerating expansion) may well accounted for by a positive cosmological constant.

So we need to understand this type of spacetime really well… and it seems that we don’t. Now there’ve been a lot of people looking at all this and doing really excellent work, and they understand various issues really well – I am not one of them, as I’ve not worked on this in any detail as yet. Do look at the papers of Marolf, and of Shenker, and collaborators, and references therein, and catch up with what’s been going on in your own way. For what it is worth, the sense that I get is that we’re trying to solve very difficult issues of how to interpret various quantum features of the spacetime and getting a lot of puzzles by trying to make it look a lot like things we’ve done before.

Now, we may solve all these puzzles…. but my current take on this all is that we’re [...] Click to continue reading this post

Passing Star People

John Williams in RehearsalYou might not know the name Maurice Murphy, but I am certain that you are likely to know – and maybe even be very familiar with – his work. His is the principal trumpet playing the lead themes in very many films with music by John Williams. I have for a long time been very impressed with how so many of those themes trip so easily off the tongue (physical or mental) and seem to fit together so well (just hum the Star Wars theme, and then follow it by the Superman theme, then the Indiana Jones theme, and so on). A lot of this is due to the fact that Williams (like most good composers) is a master at recycling and modifying, creating a cluster of much loved (deservedly) themes that accompany some of our favourite movie-going memories, but I now think that the other reason is that you’re hearing them all played by the same voice! That voice is the playing of Maurice Murphy, the truly wonderful trumpeter who Williams would specifically request to play the lead on recordings of his film music. Murphy died recently, and you can dig a bit more about him and explore what I’ve been telling you further by going to the London Symphony Orchestra’s site devoted to him [...] Click to continue reading this post

Minority Report

This is a quick update on the school. I’ve been trying to give the students some of the core concepts they need to help them understand what string theory is, how it works, and what you can do with it. Here’s the really odd thing about all this (and an explanation of the post title): While this is a school on Quantum Gravity, after talking with the students for a while one learns that in most cases the little they’ve heard about string theory is often essentially over 20 years out of date and almost always totally skewed to the negative, to the extent that many of them are under the impression that string theory has nothing to do with quantum gravity at all! It is totally bizarre, and I suspect it is largely a result of things that are said and passed around within their research community.. So there [...] Click to continue reading this post

Planck Matters

You can read a bit about the work of my colleague Elena Pierpaoli and her postdocs and students in this article in one of USC’s in-house publications. It focuses on the Planck observatory (image right from NASA/ESA), which we’ve discussed here before. (Recall the launch?) There’s a lot of exciting physics about the very young universe to be discovered as more data from the mission get gathered and analyzed.

Enjoy the article!

-cvj Click to continue reading this post

CDF Says No

Recall the excitement last week about the D0 result? I wrote a post called “An Exciting Asymmetry?”. Well, there’s a rule that says if you write a title as a yes/no question, the answer is often (usually?) “No”.

Sure enough. over at Resonances, Jester reports that the CDF experiment, also at the Tevatron, has looked for a confirmation of the CP violating result that D0 claimed to see, and did not find anything abnormal where it should have. Find further details (on the technical side for the experts) and links at that post, which, as is usual with material from that blog, is well-written and interesting.

This is one reason why we (the particle physics community) build multiple detector/experiments on the same accelerator machine, and this is a prime example [...] Click to continue reading this post

An Exciting Asymmetry?

A big mystery in physics is why there is more matter than anti-matter. (Of course, which we call the matter and which we call the “anti-matter” is a… matter of convention. Take your pick.) It is hoped that there is some mechanism in the laws of physics (at a very basic level concerning particle interactions) that will become apparent that explains it. It’s also hoped that the mechanism itself might have some understandable origin too. The mechanism would operate in the first tiny fractions of a second of the universe’s life when the primordial soup of particles and antiparticles (created from, roughly speaking, the energy of the big bang) began to cool down as the universe expanded. Rather than them annihilating all back into energy again, the mechanism would create an imbalance between the two, giving rise to a matter-filled universe, from which we emerged. So what could be the mechanism, can we isolate it in our theories and in our experiments? Build a good model of it? Explain it?

This is all very first and foremost in people’s minds when there’s a new experiment switched on that is probing the unknown – the Large Hadron Collider. Well, actually, it has been recently announced that a suitable mechanism (or, more precisely, its [...] Click to continue reading this post

Categorically Not! – Imagine

yossi_govrin_sculptureThe next in the Categorically Not! series the series of events is tomorrow, Sunday 18th April. It is, as usual, held at the Santa Monica Art Studios. It’s a series – started and run by science writer K. C. Cole – of fun and informative conversations deliberately ignoring the traditional boundaries between art, science, humanities, and other subjects. I strongly encourage you to come to them if you’re in the area. Here is the website that describes past ones, and upcoming ones. See also the links at the end of the post for some announcements and descriptions (and even video) of previous events. (At the right is an image of a beautiful sculpture by artist Yossi Govrin, who is on this week’s program.)

The theme this month is Imagine. Here’s the description from K. C. Cole: [...] Click to continue reading this post

Ask a Nobel Laureate

mather_youtubeHere’s a fun thing to get involved with. You can ask John Mather (2006 Physics Nobel Prize) a question on YouTube! Go and submit yours!

What might you ask him? Something about physics, or something else? Religion, art, politics? His favourite colour? If you consider asking a question, and whether you go ahead and ask it or not, feel free to mention in the comments what you might ask.

This is how to proceed (from NASA education)*: [...] Click to continue reading this post

More Book Fun!

bookfair_homeMark your calendar for Sunday! The West Hollywood Book Fair is on from 10 am to 6:00 pm that day, and there’s so much to see and do with readings, panels, discussions, authors, special celebrity guests, food, exhibitions, writing workshops, discount book offers, signings, swag (no doubt), and so forth. I’ve not been before, but as you know from reading here I’m a big fan of cities going gaga over books for a while, being a regular visitor to the LA Times Book Festival when it comes in the Spring. The calendar of events and much more about the event can be found at the website here.

Here’s another thing. Despite the fact there was no mention of a spankingly splendid [...] Click to continue reading this post

Ten Things That Go Boom!

the_universeWell, ok… Boom is not quite accurate, but the idea is that there will be ten kinds of blasts/explosions/major_energetic_events discussed tonight on the History Channel’s The Universe:

The Universe is full of explosions that both create and destroy. The Chicxulub impact on the Yucatan peninsula, which may have wiped out the dinosaurs 65 million years ago, was two million times more powerful than the largest nuclear bomb ever detonated on Earth. But guess what? That’s only good enough for the very bottom of the Biggest Blasts top ten list. This episode works its way up through supernova explosions and gamma ray bursts all the way to the blast that started it all–the Big Bang.

Sounds good doesn’t it? There’s a lot of good people contributing again, so I know it’ll have some good material and explanations.

In addition, I’m reasonably confident I play a role in this one…This one was a blast (sorry) to film. You saw some posts earlier reporting on some of the filming. Assuming they used the material I did with them, you’ll get to see why I was at the [...] Click to continue reading this post


Forgot to report on this email exchange from last semester:

From one of the staff in the physics office:

Subject: 499 Syllabus
Date: Thu, 09 Jul 2009 14:01:38 -0700
From: Beverly
To: Clifford V. Johnson

I was reading the syllabus you sent over for the 499 class. I am not sure if this is a type-o but in the Extra Books section it reads “/Black *_hoes_* and Time Warps: Einstein’s outrageous Legacy/” should it read
“/Black *_holes_* and Time Warps: Einstein’s outrageous Legacy/”.


My response: [...] Click to continue reading this post

Wish the Observatory Good Luck!

60 inch at mount wilson The fires are racing up the sides of Mount Wilson as I write (19:38). They expect the burn to get to the top sometime in the next few hours, and yes, I imagine it’ll affect the Mount Wilson Observatory in some way.

[Update (20:59): You can get regular updates from the director at this page*. Seems that fire crews will remain on site for when/if the fires sweep through the grounds. ]

All of the working scientific equipment, including the solar telescopes and of course the historic telescopes (the 60 inch is pictured to the right) with which astounding discoveries were made about our universe (such as the fact that it is expanding, and the fact that the universe is vastly more than just our Milky Way Galaxy) are presumably in some danger, as well as support buildings of various kinds. I’ve no idea how much since I do not know what fire-proofing measures are in place up there, although I am sure there are several – such as keeping brush away from the buildings themselves. Here’s a camera up there on one of the solar telescopes where you can see regularly updated pictures that it snaps. I grabbed this one just now (click for larger view):


So keep your fingers crossed for luck for the instruments, and of course for all [...] Click to continue reading this post

The Big Day!

Herschel & Planck Ariane 5 ECA V188 Launch CampaignTomorrow 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

Yesterday at JPL

jpl_open_house_2009_1I 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.)

jpl_open_house_2009_5 jpl_open_house_2009_6

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

Tales From The Industry XXV – Parallel Universes

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

GLAST, Fermi, and Early Results

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.


This all-sky view from GLAST reveals bright emission in the plane of the Milky Way (center), bright pulsars and super-massive black holes. Credit: NASA/DOE/International LAT Team.

Some words from the release: [...] Click to continue reading this post

At Last – GLAST!

GLAST launch in progressGood 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

Distractions in the Dark

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

Good Company

Brian May. Photo from:, 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

Sad Ending

sam smith’s oatmeal stoutThat’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

Tales From The Industry XX – Sporting Locations

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? history channel shoot - end of the universe
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

Tipping the Light Cone: Black Holes

Black Holes by Tamsin Van Essen:

Black Holes, by Tamsin Van Essen. Part of a series of lovely ceramics with a physics theme. For more, visit the websites here and here.

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

Beyond Einstein: Fixing Singularities in Spacetime

Not long ago David Morrison (UCSB) came to the mathematics department here at USC to give a colloquium.

David Morrison Colloquium at USC

This was a treat for me for many reasons. Here are three:

  1. It’s always good to see Dave. He’s one of the people I’ve known in the field was since my very first postdoc when I was learning to survive in the big bad world on my own after graduate school. I mostly could not understand a word he or anyone there else said in those days (IAS Princeton, right in the belly of the

[...] Click to continue reading this post

Two Rings

Now have a look at this object (and its enlargement on the right):

double einstein rings

What is it? It’s a double Einstein ring! An Einstein ring is formed by gravitational lensing – the bending of light from one object by the gravity of another object – and is typically formed when a distant galaxy lines up with another, closer galaxy. The result is a rather nice ring shape.

To find a double Einstein ring is rare! In fact, this is the first one that’s been announced. Not only is it novel, it can also use used to do a good deal of science, such [...] Click to continue reading this post

Categorically Not! – Beginnings

Bob Miller at Categorically Not!The next Categorically Not! is on Sunday December 16th (upcoming). The Categorically Not! series of events that are held at the Santa Monica Art Studios, (with occasional exceptions). It’s a series – started and run by science writer K. C. Cole – of fun and informative conversations deliberately ignoring the traditional boundaries between art, science, humanities, and other subjects. I strongly encourage you to come to them if you’re in the area.

Here is the website that describes past ones, and upcoming ones. See also the links at the end of the post for some announcements and descriptions (and even video) of previous events. (Above right: The artist Bob Miller speaking at the event entitled “Really?” on 23rd April, 2006. He died recently on Oct. 28th 2007, and this week’s event is dedicated to him.)

The theme this month is Beginnings. Here’s the description from K C Cole:

Every thing (and every body) began sometime. Even matter, space and time have a history. So do music, religion and galaxies (and along with them, musicians, religious scholars and astronomers.) Of course, how things begin determines to a large extent how they evolve and go on to influence both human culture and the universe at large. So for this month’s Categorically Not, we’ll look at beginnings from three widely (and somewhat wildly) diverse perspectives.

categorically not! Beginnings Speakers

[...] Click to continue reading this post