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Archive for March, 2014

Today I thought I would share this great song by Scottish band Travis. I realise this is the second Friday in a row that I’ve blogged about a Glaswegian band, with last week’s blog about a Belle & Sebastian song. This is purely accidental I can assure you. “Why Does it Always Rain on me?” was released in August of 1999 and is one of my favourite songs by this band. It reached number 10 in the DUK singles charts, and was a hit in many other countries too. It is from their second studio album, “The Man Who”.



Travis' single "Why Does it Always Rain on me?" reached number 10 in the DUK singles charts in 1999.

Travis’ single “Why Does it Always Rain on me?” reached number 10 in the DUK singles charts in 1999.



The song was written by Fran Healey of the band whilst he was on holiday in Israel (strange, given how much wetter Scotland is!). Here are the lyrics


I can’t sleep tonight
Everybody saying everything’s alright
Still I can’t close my eyes
I’m seeing a tunnel at
The end of all these lights

Sunny days
Where have you gone?
I get the strangest feeling you belong
Why does it always rain on me?
Is it because I lied when I was seventeen?
Why does it always rain on me?
Even when the sun is shining
I can’t avoid the lightning

I can’t stand myself
I’m being held up by invisible men
Still life on a shelf when
I got my mind on something else

Sunny days
Oh Where have you gone?
I get the strangest feeling you belong.
Why does it always rain on me?
Is it because I lied when I was seventeen?
Why does it always rain on me?
Even when the sun is shining
I can’t avoid the lightning

Oh, where did the blue skies go?
And why is it raining so?
It’s so cold

I can’t sleep tonight
Everybody saying everything’s alright
Still I can’t close my eyes
I’m seeing a tunnel at the end of all these lights

Sunny days
Oh Where have you gone?
I get the strangest feeling you belong.
Why does it always rain on me?
Is it because I lied when I was seventeen?
Why does it always rain on me?
Even when the sun is shining
I can’t avoid the lightning

Oh, where did the blue sky go?
Oh, and why is it raining so?
It’s so cold
Why does it always rain on me?
Is it because I lied when I was seventeen?
Why does it always rain on me?
Even when the sun is shining
I can’t avoid the lightning
Why does it always rain on me?
Why does it always rain on… on…



And here is the official video. Enjoy!






Which is your favourite Travis song?

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A few weeks ago (the 18th of March), on a beautiful early spring afternoon, I went into Bute Park in the centre of Cardiff to take some photographs of spring flowers. Here are the results.

A backlit daffodil in Bute Park, Cardiff taken on the 18th of March 2014.

A backlit daffodil in Bute Park, Cardiff taken on the 18th of March 2014.

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For those of you interested, I took all the photographs using a Tamron 70-300mm macro lens on my Nikon D70 DSLR, which is now nearly ten years old but works fine and produces high quality images. I took all the photographs in RAW mode, using the aperture priority mode, allowing the camera to use its autofocus. Most photographs were taken with the aperture wide open (which is about f/4 to f/5.6 depending on the zoom of the lens), as it was late afternoon and the light was getting weak. But, for some of the photographs, I stopped down the aperture to increase the depth of field.

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At number 364 in Rolling Stone Magazine’s 500 greatest albums of all time is “LA Woman” by The Doors. The list from 370 to 361 is as follows:


  • 370 – “Mott” by Mott the Hoople (1973)
  • 369 – “Louder Than Bombs” by The Smiths (1987)
  • 368 – “The Eagles” by The Eagles (1972)
  • 367 – “Ray of Light” by Madonna (1998)
  • 366 – “American Recordings” by Johnny Cash (1994)
  • 365 – “Rage Against the Machine” by Rage Against the Machine (1992)
  • 364 – “LA Woman” by The Doors (1971)
  • 363 – “Substance” by New Order (1987)
  • 362 – “Siamese Dream” by The Smashing Pumpkins (1993)
  • 361 – “Stankonia” by OutKast (2000)


The only one of these albums which I own is “LA Woman” by The Doors, although I do own other albums by The Smiths, Madonna (yes, her greatest hits album “The Immaculate Collection”), Johnny Cash and The Eagles. I also own songs by New Order, Mott the Hoople (whom I blogged about here), and I have heard but do not own anything by The Smashing Pumpkins and Rage Against the Machine. I have no clue who OutKast are, have never heard their music nor am I likely to I feel.

So, clearly I will blog about “LA Woman”, but not just because it is the only one in this list which I own. It is a great album, as the caption to the album cover says, it was a real return to The Doors’ roots with bluesy music. Little did they know when they recorded it that Jim Morrison would be dead within 3 months of its release.



At number 364 in Rolling Stone Magazine's 500 greatest albums is "LA Woman" by The Doors.

At number 364 in Rolling Stone Magazine’s 500 greatest albums is “LA Woman” by The Doors.



The track listing for this album is
1. “The Changeling”
2. “Love Her Madly”
3. “Been Down So Long”
4. “Cars Hiss by My Window”
5. “L.A. Woman”
6. “L’America”
7. “Hyacinth House”
8. “Crawling King Snake”
9. “The WASP (Texas Radio and the Big Beat)”
10. “Riders on the Storm”


There are some really great songs on this album, my favourites are “Love Her Madly”, “L.A. Woman”, “The WASP (Texas Radio and the Big Beat)” and the track I am going to include here, “Riders on the Storm”. This last track on the album was one of the first Doors songs I ever heard, when I was about 16 or 17, and I was mesmerised by it. It was like no song I had ever heard before, and I still find it bewitching. The lyrics are

Riders on the storm
Riders on the storm
Into this house we’re born
Into this world we’re thrown
Like a dog without a bone
An actor out alone
Riders on the storm

There’s a killer on the road
His brain is squirmin’ like a toad
Take a long holiday
Let your children play
If ya give this man a ride
Sweet memory will die
Killer on the road, yeah

Girl ya gotta love your man
Girl ya gotta love your man
Take him by the hand
Make him understand
The world on you depends
Our life will never end
Gotta love your man, yeah

Yeah!

Riders on the storm
Riders on the storm
Into this house we’re born
Into this world we’re thrown
Like a dog without a bone
An actor out alone
Riders on the storm

Riders on the storm
Riders on the storm
Riders on the storm
Riders on the storm
Riders on the storm

Enjoy!




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The discovery of quasars in the 1960s played a crucial role in helping show that the Universe was different in the past. This had important implications for the testing of the two competing cosmological theories of the time – the “big bang theory” and the “steady state theory”. The steady state theory, whose main proponent was Fred Hoyle, argued that the Universe had always existed and did not change in time. The big bang theory, on the other hand, argued that the Universe had a finite beginning in time, and that since this beginning had expanded, cooled and evolved.

The discovery of quasars was made using radio astronomy, and in fact the word “quasar” stands for “quasi-stellar radio source”. Later similar objects would be found that did not emit strongly in the radio, and so the term “QSO” (quasi-stellar object) was suggested. Both acronyms are used today, pretty much interchangeably. The term “quasar” is often used incorrectly for QSOs which do not have strong radio emission.

The beginnings of radio astronomy

There was a little radio astronomy done before the 2nd World war. Karl Jansky accidentally discovered radio waves coming from space in 1931. After a little research he realised that the signal he was detecting with his radio receiver was coming from the centre of our Milky Way galaxy. However, Jansky was an engineer working for Bell Labs, and his request for funding to follow up this discovery and do a more complete survey of radio emissions from space was rejected, and Jansky re-assigned to another project and not given the freedom of following up on this discovery. The unit of flux in radio astronomy, the Jansky, is named after him.

In 1944 Dutch PhD student Hendrik van de Hulst predicted the existence of an emission line from neutral hydrogen, due to a hyperfine splitting in the ground state. I will explain in a separate blog the theory behind this, but basically the emission line comes about when an electron jumps between two very closely spaced energy levels in the ground state of neutral hydrogen. Because the energy difference is so small, the wavelength of the ensuing photon is extremely long – 21cm to be precise. This is in the radio part of the electromagnetic spectrum.

With a combination of this prediction, and the developments made in radar during the 2nd World war, the post-war years saw a boom in radio astronomy. One of the first groups to be established was at Cambridge University. The group was initially led by Martin Ryle, who had worked during the war with the Telecommunications Research Establishment on the design of antennae for airborne radar equipment. After the war, Ryle got a fellowship at the Cavendish Laboratories, and it was there that he established what became known as the Cambridge Radio Astronomy group.

The first Cambridge Radio catalogue (1C)

In 1950 he and his group published the first ever catalogue of radio sources. The paper, published in Monthly Notices of the Royal Astronomical Society (Ryle etal. 1950, MNRAS, 110, 508-523) was entitled “A preliminary survey of radio stars in the Northern Hemisphere”. In this paper they listed the positions of 50 discrete “radio stars”, along with the intensity of each source. The positions were not known very accurately, because the long wavelength used (3.7 metres) meant the resolution of their antenna array could not locate the sources’ exact positions to better than about 1 degree of arc. This was a major problem in identifying which astronomical objects the radio sources were.

The second Cambridge radio catalogue (2C)

The second catalogue by the Cambridge group was published in 1955. Entitled “A survey of radio sources between declinations -38 degrees and +83 degrees”, the lead author was John Shakeshaft of the group, with Ryle as second author. It was published in the Memoirs of the Royal Astronomical Society, (MmRAS 1955, 67, 106-154).

Just like the first catalogue, the second one was done at a wavelength of 3.7 metres. In this second catalogue, 1936 radio sources were found. Of these, 500 of the most intense could have their positions determined to an accuracy of about +/- 2 arc minutes in Right Ascension, and about +/- 12 arc minutes in declination. The team found most of the sources were of small angular diameter, and were distributed isotropically over the sky (that is to say not in any particular direction).

About 30 of the sources were of larger angular diameter, between 20 and 180 arc minutes, but the majority of these larger sources were close to the plane of the Mily Way galaxy and so the authors suggested that they represented a “rare class of galactic object”. They then went on to say that about 100 of the sources appeared to be related to objects which were in the New General Catalogue or the Index Catalogue; both optical catalogues of nebular objects which had been put together in the 1800s and the first decade of the 1900s.

The Third Cambridge radio survey (3C catalogue)

In 1959 the Radio Astronomy group at Cambridge produced their 3rd catalogue, using an upgraded antenna array. This time the observations were done at a frequency of 159 MHz (which corresponds to a wavelength of 1.9 metres). The paper, entitled “A survey of radio sources at a frequency of 159 Mc/s” was published in the Memoirs of the Royal Astronomical Society with D.O. Edge as lead author, and listed 471 sources (MmRAS 1959, 68, 37-60). It was revised in 1962 by Bennett, so the revised 3C catalogue had 470 sources (Bennet, 1962, MNRAS, 125, 75-86). Initially astronomers used the 3C catalogue to try to find optical counterparts to these radio sources. After 1962, with Bennet’s improved catalogue, the revised catalogue (3CR) was used.

The discovery of quasars

The first object in the 3C catalogue to which an optical counterpart was found was the object 3C 48, in 1960 by Thomas Matthews and Allan Sandage (both of Caltech). Using radio interferometry to narrow down its position, and then subsequent direct optical photographs, they found that 3C 48 corresponded to a faint blue star-like object. When its spectrum was taken, it looked unlike the spectrum of any star. First of all it contained emission lines (the spectra of stars usually show absorption lines), and these lines were broad not narrow as is usually the case with blue stars. But, most puzzlingly, the pattern of lines did not seem to fit any pattern that astronomers had seen before.

By 1963 Matthews and Sandage had found three starlike counterparts to three sources in the 3C catalogue, and published this in the Astrophysical Journal (“Optical Identification of 3c 48, 3c 196, and 3c 286 with Stellar Objects”, 1963, ApJ, 138, 30-56). The nature of the three sources was not known, but at least it seemed that they had been identified.

A breakthrough happened in 1962. One of the other 3C sources, 3C 273, was predicted to pass behind the Moon on several occasions. Using the Parkes Radio Telescope in Australia, Cyril Hazard and John Bolton were able to make measurements which allowed Caltech astronomer Maarten Schmidt to find its optical counterpart. Using the Mount Palomar 200-inch telescope, Schmidt obtained a spectrum of the star-like object. The spectrum was as confusing as that of 3C 48, he could see emission lines but was not able to identify them, the pattern just didn’t seem to make any sense.

After much head scratching, Schmidt realised that the lines corresponded to hydrogen emission lines, but they were redshifted to such an extent that he had failed to recognise them. The redshift he measured for 3C 273 was nearly 16% of the speed of light, an unheard of redshift at that time. Assuming Hubble’s law which relates redshift to distance, this put 3C 273 at a huge distance from Earth, much further away than any galaxy ever seen. This work was published in a one page letter in Nature in 1963 – “3C 273: a star-like object with large red-shift”. Nature 197, 1040-1040.



Caltech astronomer Marteen Schmidt, who in 1963 discovered quasars.

Caltech astronomer Maarten Schmidt, who in 1963 discovered quasars.



Very soon afterwards, Jesse Greenstein and Matthews at Caltech identified the redshift of 3C 48, and found it to be 37% of the speed of light, over twice as far away as 3C 273! (“Red-Shift of the Unusual Radio Source 3C48”, 1963, Nature 197, 1041–1042).

The acronym “quasar” was coined by astrophysicist Hong-Yee Chiu. In 1964, he said in an article in Physics Today magazine

So far, the clumsily long name ‘quasi-stellar radio sources’ is used to describe these objects. Because the nature of these objects is entirely unknown, it is hard to prepare a short, appropriate nomenclature for them so that their essential properties are obvious from their name. For convenience, the abbreviated form ‘quasar’ will be used throughout this paper.

As more research was conducted it was found that not all these quasi-stellar objects with extremely high redshifts had strong radio emission. some were “radio quiet”, so the name “QSO” was coined, but because the term “quasar” had been in use for quite a while by this time, many or most astronomers refer to these objects as quasars whether they are radio-loud or radio-quiet.

An evolving Universe

I will go into more detail in a future blog about what we think quasars are. It was in the early 1980s, using the Hubble Space Telescope, that their host galaxies were observed for the first time. They are the extremely active core of galaxies, but are only found in the distant universe. The lowest redshift quasar is at a redshift of 0.056. To put this into context, the redshift of the Norma Cluster is 0.01570, so the nearest quasar lies some 3 times further away. The further away one looks, the more common quasars are. As they are not found in the local Universe, and as looking far away means looking back in time, quasars are very clear evidence of the evolution of the Universe. They are one of the strongest pieces of observational evidence for an evolving Universe, and thus one of the pieces of evidence which helped show that the steady state theory of the Universe was wrong.

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It was Arsène Wenger’s 1000th game in charge of Arsenal, and one he will want to forget. In a goal fest at Stamford Bridge, Chelsea ran riot over an abject Arsenal, giving Chelsea their biggest ever win over their London rivals.



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The gulf between the two sides left one wondering how Arsenal are within just a few places of top-placed Chelsea. As Mourinho said after the game, the match was over within the first 7 minutes, with Chelsea already 2-0 up. By half time it was 4-0, and the second half was just a lap of honour for the dominant Chelsea side. The victory leaves Chelsea 4 points clear at the top of the Premiership, but the lead is a little misleading as all the teams immediately below them have games in hand, with Manchester City having three games in hand!



The English Premiership as of Saturday the 22nd of March.

The English Premiership as of Saturday the 22nd of March.



Chelsea have the easiest next two Premiership matches of the top three teams. They play Crystal Palace away next Saturday and the following Saturday play Stoke City at home. They are both games Chelsea would expect to win. Liverpool’s next two games are a home game against Sunderland this coming Wednesday and then next Sunday a potentially tough game against Tottenham Hotspur away. For Manchester City their next two games are both tough ones, the first is tomorrow (Tuesday) evening against Manchester United away and then next Saturday with an away game against Arsenal. Hopefully Chelsea’s lead will be even bigger in two weeks’ time!

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Today I thought I would share this great song by Scottish band Belle & Sebastian – “The State I am in”. It is the first track on their debut album Tigermilk, and was released in 1996.



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The words and music are by founding member of Belle & Sebastian, Stuart Murdoch. The “Mark’s and Spencer’s” referred to in the song is the same “marks and sparks” referred to by David Bowie in the Mott the Hoople song “All the Young Dudes” that I blogged about here.


I was surprised, I was happy for a day in 1975
I was puzzled by a dream, it stayed with me all day in 1995
My brother had confessed that he was gay, it took the heat off me for a while
He stood up with a sailor friend and made it known upon my sister’s wedding day

Got married in a rush to save a kid from being deported
Now she’s in love
Oh, I was so touched, I was moved to kick the crutches from my crippled friend
She was not impressed that I cured her on the sabbath
I went to confess
When she saw the funny side, we introduced my child bride to whiskey and gin
To whiskey and gin

The priest in the booth had a photographic memory for all he had heard
He took all of my sins and he wrote a pocket novel called “The State That I’m In”
And so I gave myself to God
There was a pregnant pause before he said okay
Now I spend my days turning tables around in Mark’s and Spencer’s
They don’t seem to mind

I gave myself to sin
I gave myself to providence
And I’ve been there and back again
The state that I am in

Oh, love of mine, would you condescend to help me
Because I’m stupid and blind
Oh, and desperation is the devil’s work
It is the folly of a boy’s empty mind
Oh, and now I’m feeling dangerous
Riding on city buses for a hobby is sad
Why don’t you lead me to a living end
I promise that I’ll entertain my crippled friend
My crippled friend

I gave myself to sin
I gave myself to providence
And I’ve been there and back again
The state that I am in



This is the second Belle & Sebastian song I have blogged about, the other one being their cover of “Poupée de Cire”, here. Enjoy!





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With the announcement earlier in the week of what appears to be direct evidence for cosmic inflation, I ended up getting involved in a discussion on one of John Gribbin‘s FaceBook posts with a gentleman who said “the Big Bang theory will be discredited in the next few years” (or words to that effect), and that the “Steady State theory” was the correct cosmological model.

I was a little surprised that there were even (presumably intelligent and informed) people who still felt that the steady state theory had any credence left. So, rather than answer this gentleman in private, I thought I would do a brief series of blogs on why we think that the big bang theory provides a more correct model of the Universe than the steady state theory.

I should remind readers (all two of you!), a theory is never complete. It is always a work in progress, and this is as true of the big bang theory as of any other theory. As Karl Popper said, it does not matter how many times a theory is confirmed, one robust refutation of that theory and it needs to be revised and/or abandoned. Cosmologists have been trying to test predictions of the big bang theory since Lemaître first proposed it in the 1920s, and they will continue to do so for the foreseeable future.

The expanding Universe

The expansion of the Universe was observationally discovered by Edwin Hubble and his observing assistant Milton Humason in 1929. What Hubble and Humason found was that more distant galaxies appeared to be moving away faster than nearer galaxies. The recession velocity was determined by the Doppler shift in the spectral lines of the galaxies and was a pretty robust result. The distances were a little less robust, as there was no reliable way to determine the distances to the galaxies Hubble included in his study. However, since then we have been able to use the reliable method of Cepheid variables to determine the distances to a large number of galaxies. For example, the Hubble Space Telescope (named, of course, after Edwin Hubble) was able to observe Cepheid variable stars out to large distances in the 1990s. This was a Hubble Key Project. The relationship between the distance of a galaxy and how quickly it is moving away from us, the so-called Hubble law, is now well established.



Edwin Hubble (left) and Milton Humason, who discovered the expansion of the Universe.

Edwin Hubble (left) and Milton Humason, who discovered the expansion of the Universe.



In the 1910s Vesto Slipher, working at the Lowell Observatory in Flagstaff Arizona had found that from a sample of 25 “spiral nebulae” (as they were then known), 22 appeared to be moving away from us with 3 moving towards us, based on the Doppler shift in their spectral lines. Slipher noted that there was something strange about this, but never made the connection to an expanding Universe.



The diagram of distance (x-axis) versus recession velocity (y-axis) from Hubble's original 1929 paper from the Proceedings of the National Academy of Sciences

The diagram of distance (x-axis) versus recession velocity (y-axis) from Hubble’s original 1929 paper from the Proceedings of the National Academy of Sciences



Although Hubble himself never actually said it, the most natural interpretation of the Hubble law is that the Universe is expanding. It is not that the galaxies are rushing through space, but rather that space itself is expanding. A galaxy which is twice as far away as a given galaxy will move away twice as quickly if space is uniformly expanding. Naturally, if space is getting bigger then it would have been smaller in the past – so Hubble’s discovery lent natural support to the emerging idea of a Universe which started out small and is getting bigger.



In an expanding Universe, more distant galaxies move away quicker than nearer ones because of the expansion of space. The galaxies themselves are not moving through space, it is space which is expanding.

In an expanding Universe, more distant galaxies move away quicker than nearer ones because of the expansion of space. The galaxies themselves are not moving through space, it is space itself which is expanding.



Einstein’s biggest blunder

Einstein developed his General Theory of Relativity, a radically different approach to understanding gravity, in 1916. This theory describes gravity as a bending of space and time, rather than the classical idea of gravity that Newton had developed in 1666. In 1917, when Einstein applied his new equations to the Universe, he found that it predicted a dynamic (expanding or contracting) Universe. But, at the time the general consensus was that the Universe was static, so Einstein introduced a fudge-factor, the “cosmological constant”, to give his equations a static solution. When the expansion of the Universe was later discovered by Hubble and Humason, Einstein purportedly said that the cosmological constant was “the biggest blunder of my life”, as he could have predicted the expansion of the Universe some 12 years before hand.

de Sitter, Friedmann and Lemaître

Two years after Einstein introduced his cosmological constant, in 1919, Dutch mathematician and physicist Willem de Sitter produced a solution to Einstein’s equations which had no matter but just the cosmological constant. This predicted an expanding Universe, but nobody took much notice as everyone knew the Universe contained matter.

In 1922, Russian cosmologist Alexander Friedmann produced the first solutions to Einstein’s equations which contained matter but which also predicted that the Universe might expand. Unfortunately for Friedmann, he died in 1925 and his work went largely unnoticed at the time, probably because he only published in Russian.

A few years later, in 1927, Belgian cosmologist and Catholic priest Georges Lemaître independently came up with the same idea as Friedmann. He was aware of Slipher’s work on the redshift of spiral nebulae, and conjectured that it might be a sign of the Universe expanding. He published his work in an obscure Belgian scientific journal, so it too was ignored. But then, renowned cosmologist Sir Arthur Eddington published a long commentary of Lemaître’s paper in the widely read Monthly Notices of the Royal Astronomical Society, propelling Lemaître’s work to prominence. Einstein became aware of Lemaître’s work, but was not convinced by it.

Then, in 1931, Lemaître published a letter in the most prestigious scientific journal, Nature, outlining his ideas on cosmic expansion in some detail. In this letter he suggested that the Universe had begun in what he called a primordial atom.



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Newspapers around the World picked up on the story, and the New York Times ran a front page story with the headline

Lemaître suggests one, single, great atom, embracing all energy, started the Universe.

Einstein was won over, and in 1932 he and de Sitter published a paper of a model we now call the Einstein-de Sitter model, in which they stated that the correct cosmological model was one which would just about keep on expanding to infinity, but would take an infinite amount of time to do so and would never re-collapse.

The Steady State Theory

In the 1940s a fierce opponent to Lemaître’s “primordial atom” theory would emerge, Sir Fred Hoyle. In part 2 of this blog next week I will talk about his competing theory, the “Steady State theory”, and Hoyle’s on-going battle in the 1940s and 1950s with George Gamow, who became the chief champion of the “primordial atom” theory.

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A few weeks ago my wife and I went to Liverpool for the weekend. On the Sunday the weather was superb, so after a trip to Anfield to visit the Liverpool FC museum (I will blog about that soon), we took a walk in the area near the Liver building. One of the most striking buildings in this part of Liverpool is this one – the George’s Dock Ventilation Station for the Mersey tunnel. It is a Grade II listed building. It is in an art deco style, built between 1931 and 1934. From what I have read, the architects were influenced by recent discoveries in Egypt. The two black onyx figures are meant to represent night and day, to illustrate the fact that the Mersey tunnel operated around the clock.



The art-deco George's Dock Ventilation Building in Liverpool

The art-deco George’s Dock Ventilation Building in Liverpool



For a building which is meant to be purely functional I am surprised that it was built in such an ornate style. Maybe the company were flush with money and wanted to show off a little, or maybe the architects were just good at persuading their clients to allow them to design such a stunning building. Either way, I am glad they did not build just some ugly rectangular covering to the ventilation shaft – this building is much better on the eye!





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To most of us, inflation is a nasty thing which sees the money in our pocket being worth less as prices go up. It’s a bad thing! But, in cosmology, a theory called cosmic inflation explains very neatly several key properties of the Universe. The theory of cosmic inflation was first suggested by Alan Guth in 1980, and yesterday (Monday the 17th of March 2014) a team led by John Kovak of Harvard University announced the first direct evidence that cosmic inflation did actually happen. There is also a Cardiff University involvement in this project.



The story on the confirmation of cosmic inflation as it appeared on the BBC science website.

The story on the confirmation of cosmic inflation as it appeared on the BBC science website.



What is cosmic inflation?

In 1980, particle physicist Alan Guth was pondering some of the observed properties of the Universe, and he came up with the idea of cosmic inflation. The observed properties he was hoping to explain with his theory were

  • the “Horizon problem”
  • the “Flatness problem”
  • the “Magnetic-monopole problem”

The Horizon problem

When the cosmic microwave background radiation (CMBR) (the prediction of which I blogged about here) was discovered in 1964 it was recognised that it was most probably the “echo” of the Big Bang. By 1967 Bruce Partridge and David Wilkinson of Princeton University showed that the CMBR was the same from all parts of the sky down to a level of 0.1% of its 3 Kelvin temperature.

It was realised soon after this that this presented a problem, the so called “horizon problem”. It is actually perplexing that different parts of the sky should have the same CMBR temperature because when we look in different parts of the sky we are looking at parts of space which have not had the time to be in contact with each other in any way; they are simply too far apart. Therefore, a patch of sky in one direction with a particular CMBR temperature should have no knowledge of the CMBR temperature of a patch of sky in a different direction.

This is a little bit like switching on a heater in the centre of a large room. Everyone knows that it will take time for the whole room to come to the same temperature, and if the room were really really big you would not expect the corners which are far away from the heater to have the same temperature as the centre of the room next to the heater after just a few minutes. The heat just hasn’t had enough time to spread throughout the room. So, if you found that the whole room was at the same temperature, even though the heat hadn’t had enough time to spread throughout the room, it would be a bit of a puzzle. That is, in essence, the “horizon problem”.

The flatness problem

Einstein showed in his theory of gravity, the General Theory of Relativity, that gravity causes space to bend. A Universe with lots of matter in it will have a different geometry (shape) to a Universe with less matter in it. The so-called “critical density” of the Universe would be a density that would give it a flat geometry. It was realised since the 1960s that the density of the Universe seemed to be very close to the critical density. Why should this be, when it could have any value. It could be much much more or much much less? If you do the mathematics, for the density to be within about a factor of two of the critical density today means it had to have been incredibly close to the critical density in the earliest moments of the Universe. Close to about one part in 10^{60}!! This is the “flatness problem”.

The magnetic monopole problem

In electricity, we are all familiar with positive and negative charges. James Clerk Maxwell showed in the mid 1800s that electricity and magnetism are part of the same force, electromagnetism. And yet, you never find a magnetic monopole, you always find magnetic poles come in pairs, they always have both a north and south pole. Theoretically there is no reason why one shouldn’t find just e.g. a north pole on its own, without a south pole. This is the “magnetic monopole problem”.

What is cosmic inflation?

Alan Guth’s idea of cosmic inflation suggested that when the Universe was incredibly young, some 10^{-36} seconds old, it went through a brief period of very rapid expansion. This period ended when the Universe was about 10^{-33} \text{ or } 10^{-32} seconds old, but in this incredibly brief period Guth argued that the Universe grew from being much smaller than a proton to something about the size of a marble. After this brief period of very rapid expansion (inflation), the expansion of the Universe settled down to the more sedate rate of expansion that we see today.

How does cosmic inflation solve these three problems?

The horizon problem is solved by inflation because the very rapid expansion which inflation proposes would allow parts of the Universe which are now too far apart to have ever communicated with each other to have been close enough together before inflation. So, going back to my analogy with the room being heated, it is as if the room started off really small, so small that all parts of it could come to the same temperature, then it suddenly expanded so that the room we are now looking at is much much bigger.

The flatness problem is solved by cosmic inflation by drawing the analogy between the geometry of the Universe and a curved surface. If a curved surface is large enough, then on a local scale it is always going to look flat. An easy analogy to understand this is the surface of our Earth. We all know it is spherical, but on a local scale it appears flat. If the Universe underwent a period of cosmic inflation, then we are seeing such a small part of it that the small part we see is always going to appear flat, no matter what the overall geometry.

The magnetic monopole problem is solved by cosmic inflation in the following manner. The idea is that magnetic monopoles were created in large quantities before the period of cosmic inflation. They should still exist today, but because the Universe expanded so rapidly during cosmic inflation, their number density (how many there are per unit volume) is so tiny that we haven’t found any in the part of the Universe which we are able to observe.

The discovery made by BICEP2

Until yesterday, there had been no direct evidence of anything that cosmic inflation predicted, only agreement between the theory and things which had already been observed. One prediction of the theory is that the CMBR should be polarised in a particular way with a particular amount of polarisation (you can think of polarisation as a particular twisting of radiation, instead of vibrating in all directions it only vibrates in particular directions). The BICEP2 experiment (“Background Imaging of Cosmic Extragalactic Polarization”, the “2” indicates it is the second generation of this experiment) has been using the South Pole Telescope which is, as the name implies, at the Earth’s south pole, and has been looking for a particular signature in the CMBR – the “B-mode polarisation” as it is called.

Yesterday the team announced that they had, for the first time, detected this B-mode polarisation, which is the most direct evidence yet that the theory of cosmic inflation is correct. This polarisation comes about due to gravitational waves in the very very early Universe, so the detection of the B-mode polarisation is also direct evidence of gravitational waves, which were predicted by Einstein but have never been directly detected before.

If you want to read the actual announcement paper you can find the pre-print by following this link here. Here is a screen capture of the first page of the paper.



The first page of the paper announcing the detection of evidence for cosmic inflation.

The first page of the paper announcing the detection of evidence for cosmic inflation. Notice that Cardiff University has an involvement with Peter Ade being the first author in the alphabetical list.



Superimposed on the variations in the temperature of the cosmic microwave background (red and blue blobs) is the evidence for the B-mode polarisation (the small swirls or black lines).

Superimposed on the variations in the temperature of the cosmic microwave background (red and blue blobs) is the evidence for the B-mode polarisation (the small black swirls).



This is very exciting news for cosmology and our understanding of the earliest moments of the Universe. It suggests that our model of the early Universe, including the theory of cosmic inflation, is correct (or at least is on the right tracks). Little by little, astronomers are unfolding the mysteries of the very earliest moments of creation!

If you want to read a more technical (but still non-specialist) explanation, then this story in Sky & Telescope is pretty good. Or, you may prefer this from Sean Carroll’s blog.

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BICEP2DAY

Breaking news on the apparent confirmation of Cosmic inflation

In the Dark

Well, it’s official that this afternoon’s announcement of a “major discovery” is going to be from the BICEP team, and it specifically concerns the BICEP2 CMB telescope experiment. I’ve just got back to Sussex (after a weekend in Cardiff) and will be following the events in among other things I have to do before going off to give a lecture at 5pm GMT.

The schedule of events is as follows: there will be a special webcast presenting the first results from the BICEP2 CMB telescope. The webcast will begin with a presentation for scientists 10:45-11:30 EDT, followed by a news conference 12:00-1:00 EDT.

You can join the webcast from the link at http://www.cfa.harvard.edu/news/news_conferences.html

Papers and data products will be available at 10:45 EDT from http://bicepkeck.org/

EDT is four hours behind Greenwich Mean Time so the webcast will begin at 14:45 GMT, i.e. in about half an hour.

In the mean…

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