## Discovery Coincidence

Some 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

[Update: Over the months following the announcement, doubt was cast over exactly what BICEP2 saw, and now it seems that the signal announced by BICEP2 is consistent with polarisation produced by galactic dust. See here.]

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

Don’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:

## 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

You 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 I 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 theory 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

## Heretic…?

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

You 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!