The ISW Mystery IV: Where does the evidence lead?

Where does the evidence lead? (Photograph: H Armstrong Roberts/Corbis)

In my last three major posts (I, II and III) I've been talking you through a mystery: the integrated Sachs-Wolfe mystery. This post will be able to be read on its own, but it you will appreciate it much more if you have also read them. In today's post I will be playing detective, examining the evidence, looking for leads and weighing up the various possible solutions to the mystery. Like any good mystery there are hints as to what the resolution might be, but like any good mystery story some of these hints might turn out to be just be red herrings, so we need to be careful.

At the beginning of my most recent post in this series I warned you that it would be my most technical post to date, but encouraged you to stick with it. With this post, the situation is the opposite. That post contained the details of the actual measurement that was made, which is necessarily going to be somewhat dry and technical. This post, however, speculates about what might have caused the effect. As you'll soon see, solving the mystery potentially requires modifications to our understanding of fundamental physics or the initial conditions of the universe. All very exciting stuff, so congratulations for making it to this point.

An overview of the case:

Before embarking on the detective work, let me recap the first three posts in this series. In the first post, I introduced what the integrated Sachs-Wolfe effect is. It is the very subtle heating and cooling of light as it passes through over and under dense regions of the universe. In the second post I explained that this effect is so small that it almost certainly will never be observed directly. The only hope we have to observe it is to look for statistical correlations between the temperature of light on the sky and the density of the matter that the light travelled through to reach us. Only the cosmic microwave background (CMB) is uniform enough that such a statistical correlation could ever be observed. In the last instalment, I told you of a particular measurement that intended to detect this ISW effect by looking at extreme over and under densities in the universe. The measurement appeared to be a success because it did measure a correlation. The only problem, and the source of the mystery, is that the size of the correlation is far too big to be from the ISW effect.

Something in those structures is heating/cooling the CMB, but what?

The human machine: biological batteries and motors

So far in my series of posts, I’ve tried to give you an appreciation for how war is fought on a microscopic level, which is to say: how invading pathogens try to consume our body’s resources, and how our immune system fights back. In my last post, I also tried to convey some of the contemporary research that is expanding our understanding of this system. While this is (to me at least!) a fascinating topic, I am going to put it to one side for the time being. The reason for this is that there are just so many enthralling topics to talk about when it comes to molecular biology! So, I have decided to concentrate a new series of posts on various interesting snippets of biology and biochemistry that I hope you will find intriguing and allow you to understand your own body a little better. In doing this, I don’t want to lose sight of the purpose of this blog – i.e. to convey a sense of the ongoing work taking place – and so will try to include cutting-edge research into each post whenever possible.

Preamble over, let’s get started...

Looking deeper and deeper

‘How does my body actually work?’ It’s a question that’s likely occurred to most of us at some point in our lives. Most people know how our skeleton is arranged and how our muscles tug at various parts of it to allow movement; similarly we all know how our hearts pump blood around this vast system, and what our various internal organs do. But science is all about finding something out and then saying ‘sure...but how does that work’ and then taking it down to the next level. When physicists discovered protons and neutrons, they weren’t content to leave it there; they took it to the next level and found out what those are made of, and then what the things they’re made of are made of, and so on to the present day. The same is true for biology – sure your muscles contract, but what are they made of, how do they contract and where do they get the energy from? It is this last point that we will deal with today: where does our body get energy from?

The simple answer to the above question is just: food. We all know we need to eat to have energy; if you’re a bit of an athlete or diet-enthusiast then you might know about the different components of food (carbs, fats, protein etc.) and how they affect the body. But have you ever wondered how all those varieties of different foods end up powering your body at the molecular level?

On the Road

Not a post this week so much as a note from the road. I'm in the final stretch of a month-long research trip, spread peripatetically across four cities. One of the central reasons for my travels has been an exhibition by Anthony McCall, Five Minutes of Pure Sculpture, which opened last week at the Hamburger Bahnhof in Berlin, Germany. The show runs until August. And it is extraordinary exhibition that I would highly recommend to anyone able to visit. I've travelled to this show because this art is, to my mind, deeply phenomenological. It needs to be experienced physically to be really understood. So it's been a joy to stand back and observe a broad range of different viewers interact with the pieces in all kinds of ways contemplative ways - from walking though and 'touching' the light sculptures, to lying flat on the ground to look up at them for long periods of time. More later from home, including some of the pictures and sounds currently locked away on my own camera...

(image credit: azurebumble)

The phenomenology of a fourth spatial dimension.

A hyperdimensional cube, known as a tesseract...

Part of the motivation for this blog was to open up a dialogue between working artists and working scientists. One of the conversations that is starting to develop relates to the (artistic) field of phenomenology and whether it does/doesn't have anything to say when it comes to the more abstruse sciences. Of course phenomenology is the study of the things humans experience (at least according to my rudimentary understanding of it) and scientists are human beings who experience abstruse science so phenomenology must have something to say about science, by definition. But what?

The discussions which began this conversation concerned two online applications that aid in the visualisation of the scales involved in time and space. See this post and this post and the comments in each for a discussion of the apps. In that discussion and in the comments to a later post I expressed a sense of disappointment in what these apps were managing to express. I should clarify that I think the apps are great and interesting, but if one is looking for a phenomenology of science I don't think this is where the most interesting phenomenology is (of course the app creators aren't looking for a phenomenology of science, so they are completely forgiven). The scale of space and time are very ordinary, everyday, Earthly things. The most interesting discoveries science has made, at least in the world of high energy physics, are not well described in such terms - this is almost precisely what makes them so interesting.

As Rhys pointed out in one of those comment threads a huge part of this problem is that many of these discoveries rely heavily on mathematics. And, to a very large degree, to understand the discoveries, you need to have a grasp of the maths. The fact that the very abstract structures and symmetries and patterns that lie hidden in the mathematics are then actually exhibited in the real universe is one of the more wonderful things experienced by a scientist. And that is not easily captured simply through pictures, videos and sounds (or even smells) of the universe.

However, I came across an app today that really does try to bridge this gap. If someone were to be looking for a true phenomenology of the more interesting and wonder inducing aspects of theoretical physics then this is the sort of thing one should be looking for. It is an app that simulates a hyper-dimensional cube. OK, so what on Earth does that mean?

Well, a dot exists in zero dimensions, it has no length, width, nothing. A line exists in one dimension, it has simply a length. A square exists in two dimensions, it has a length and a width. Next, a cube, exists in three dimensions, it has a length, a width and a depth. Now, just imagine there was a fourth spatial dimension. Mathematically this is an easy thing to write down. Then, just as one can form a cube by extending a square into a third dimension, one can form something known as a tesseract by extending a cube into a fourth spatial dimension.

Now, we creatures who exist in just three spatial dimension can't visualise a fourth spatial dimension (I certainly can't). But, just as we can look at a two dimensional surface (a TV screen) and see a projection of a three dimensional object, so can we do the same for an imagined four dimensional object projected onto three (or two) dimensions. And this is precisely what this app does for a four dimensional tesseract. [Edit: Or, as Rhys said in this comment "it shows what a 4D painter would paint on a 3D canvas..."]. And the brilliance is that the app even allows you to manipulate the tesseract, to move it, to spin it (in any of the four dimensions) and while manipulating it you see how that three dimensional projection changes on your two dimensional screen. Here's a video preview...

This app came to my attention as a consequence of minutephysics covering extra spatial dimensions in his latest video - which you should watch for a quick overview of higher dimension. There is even, apparently, a game in construction that requires you to move into and around a fourth spatial dimension to solve puzzles (for example using it to navigate one's way around obstacles and put keys into locks).

I actually think that a phenomenology of abstruse science can go even further and get even more interesting than this. A fourth spatial dimension is one of the simplest ideas I can think of that is not directly understandable from an Earthly perspective, but easily described by maths. It also has the unfortunate position of quite possibly not actually being reality and certainly not yet being testably true reality. However, it is here, with this sort of application/idea that I would think a phenomenology of the interesting bits of high energy physics should start.

Twitter: @just_shaun

Are you racist (even if you don't think you are)?

The video above describes something known in psychology as the Implicit Association Test (IAT). Keon, the dude in the video, does a good job of explaining what the test is and why it is interesting so watch and gain in understanding.

The reason why the IAT is interesting (for me at least) is that it can have quite startling results. The example Keon has chosen for his video is a racism test. Effectively, the test will determine whether the person taking the test has an implicit racism. This is not a conscious, directed, racism that might motivate someone to join a hate-group, or take some deliberate racist action, but instead a sub-conscious, implicit, racism that might direct behaviour that is more instinctive or reactive. In other words, the IAT detects racism that the person being tested won't necessarily even know they have.

The point is, you could be as tolerant and open minded as you want to be, but you live in a society that has racist undertones in it and this will have influenced you. Watch the video, take the test and see how much.

Be prepared to be surprised by the results though (whatever your own race or view on racism happens to be)...

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I happen to be friends with Keon and he posted this on Facebook a few weeks ago. I took the test in the video and had a couple of immediate objections. Firstly I found both of the final stages of the test difficult and, while I suspected I found the second one harder, I wasn't sure. But secondly, and what I thought was far more importantly I suspected strongly that the ordering of the tests conditioned me. In the process of the test I got used to associating good with white and left and bad with black and right. So I suspected that my difficulty in the final stage had more to do with the difficulty in changing than a genuine difficulty in associating good with black faces.

I mentioned this to Keon and he suggested I try either taking the test again, reversing the steps in the video, or even better, going here and taking a randomised version of the test. I chose the second option and took that test multiple times, with different orderings. I also took different versions of the test. Unfortunately, I repeatedly came out of the test having shown either a slight or a moderate preference for white faces, rather than as I would have hoped, no preference for either. This was entirely independent of the ordering of the test. If you have doubts as well then I strongly recommend that you check out the link above.

I don't rationally associate white with good and black with bad. But sub-consciously, I clearly find it easier to think white=good than I do black=good. I'm glad this test made me aware of this. Some people (especially around my realm of natural sciences) like to view the likes of psychology somewhat disparagingly because of its supposed lack of testability. Well, the people who came up with the IAT have done a stellar job of overcome this supposed boundary and have revealed very interesting things about human psychology.

Your thoughts, as always, are welcomed... (are you sub-consciously racist? were you surprised with the result? Do you doubt the effectiveness of the test?)

Keon has made lots of other videos on psychology. His YouTube channel can be found here.

[Edit: Sesh points out in this comment that even if the test does prove the existence of implicit preferences, it is not accurate to use the word "racism" to describe these associations. I have to admit that, despite my use of the word in this post, I do agree. Is this a far call?]

Follow @just_shaun

The ISW mystery III: How did the CMB get so hot?

An example map of what the ISW effect would look like on the sky if we could observe it directly (arxiv:1003.0974)

This is probably my most technical post to date. I don't want my contributions to this blog to be (all the time) popularised, ready to consume, pieces of quirky science. I want you to know what we, the cosmologists, are thinking and wondering about each day, beyond just vague explanations about accelerated expansion, dark energy and dark matter. I want you to understand how we're trying to explore the mysteries of cosmology. What are we measuring, how are we measuring it and what are we hoping it will tell us? Doing this has to be a two-way process. I invest time writing, doing my best to make things like the Integrated Sachs-Wolfe effect understandable and you invest time and concentration trying to understand.

The benefit for you of doing this is great. You will become engaged in the science in real time. When the mystery I'm about to reveal finally gets solved you will already be there waiting, expecting. You will be able to bask in the wonder of the discovery during the moments of discovery. Hence, it will also be your discovery.

You will only get this though, if you concentrate and think and read this post through. So, if you don't get it the first time, think about it and read it again. And, if you are left confused by anything, ask!

Recap of earlier posts

I'm going to describe in this post why there is an “ISW mystery”. I described in this post that the integrated Sachs-Wolfe (ISW) effect is the subtle heating and cooling of light as it passes through over and under-dense regions/structures in the universe. For most of the universe's history this effect was effectively non-existent. Any energy gained by light falling into a structure in the universe was perfectly balanced by the energy lost by the light climbing out of the structure. However, late in the universe's history something starts pushing the universe apart and as a result there is a net energy change. The gravitational well is smaller when the light leaves the structure than when it goes in.

Then, in this post, I explained that the ISW effect is incredibly small. This makes observing it very difficult. We can't observe it directly by looking at light from galaxies, quasars, supernovae, stars, etc. because we don't know the temperature of the light's source well enough. In fact, there is only one source of light that we do know well enough to use it to detect the ISW effect. This is the cosmic microwave background (CMB), which I introduce here. Unfortunately, even the tiny fluctuations in the temperature of the CMB are of the same size as the expected ISW temperature shifts. So, we still can't observe the ISW effect directly. What we can do though, is observe it on average. We know that the ISW effect occurs as light travels through over and under-dense regions in space. So what we can do is look for over and under-densities and ask whether the CMB is hotter on average when it has passed through an over-density and colder on average when it has passed through an under-density. How to find structures in space and what I mean by on average is covered in the post you are about to read...

Games as a collaborative art

[Note from Shaun: The following is a guest post from Alan Owen. Alan makes video games for a living at Plug-in Media. Amongst his claims to fame are working on two BAFTA award winning games (I and II), and making games specifically for the BBC and the Tate gallery. Alan and I happen to share the same Scottish grandparents and while I was in England recently we found time to catch up. One of the things we chatted about was Barnabas' earlier guest post on whether video games are art. Here are Alan's thoughts on where you can find the aesthetic in games...]
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The tactic of ‘logical defusal’: Denied.

In direct answer to the question ‘can video games be classed as art?’, my first draft of this post summarised a need to be rigorously clear in our definition of the terms ‘game’ and ‘art’. This is an important point to make, because it is very easy to concisely answer the question with an explicit and limited definition of each term, and an application of simple logic! The answer to the salient question is directly related to the individual asking it, and to their particular phrasal of definition: “does this ‘game’ (as I define the term) constitute ‘art’ (as I define the term)?”. Rigorously enforced definition empowers one to slice through that ‘unknown quantity’ of subjectivity, and simply get on with things...

This was, alas, seen to be a bit of a cop-out, and hence deeper thought stimulated by my diligent editor! I took such constructive criticism amicably, because Shaun hit me with a very valid point - in sidestepping the question, I’d cheated myself (and the reader) out of any enlightenment that might have been forthcoming from an appraisal of aesthetics, ‘the philosophy of the nature of art’, as it relates to the video game. So, without recourse to disarming logic: are games art?

Collaborative art

I’d like to entertain a more suitable classification for video games as a form of collaborative art, by which I mean ‘art’ executed by a number of individuals working cooperatively to create some coherent entity. In my day to day job I both participate in, and perceive other people around me, diligently working each within their own sphere of expertise to realise some greater goal: a creative digital entity that has (generally) the primary purpose of entertainment. Within my own company, the scale of such projects is relatively small (carrying a budget to match), but big games are big business, with an industry on a scale comparable to Hollywood moviemaking. What do such video games give to humanity that makes them worthwhile, beyond just a means to waste time?

Aesthetic value can be manifest in many ways within a video game, but this value can sometimes be rather hidden from the casual player or spectator. In the following paragraphs I’ll shine a light upon just some such ‘artistic’ modalities that I am conscious of when I play a video game - travelling through layers of progressively less visible aesthetics and into my own domain; the invisible.

The obviously visible: