"That's nothing", retorted the second. "When I was young the universe was still opaque and if you weren't careful you could lose your outer regions and loose arms with the all rapid inflation that was going on".

They both looked at their friend, who was sitting quietly. "You haven't said much tonight, what's up?"

"Sorry boys", he drawled. "I don't hear too good since that Big Bang went off just behind me".

The galaxy replies "I'm not drunk, just a little dizzy."

Start the engine please driver.

"It's very simple", replied George. "We're galaxies, and each night we're Messier".

"Does he always talk like that?", the barman enquired of his friend. "Well yes, actually", ansewered the first galaxy. "After all, he is the barred of Avon".

There was a "battle of the bands" contest on that night, but they couldn't take part – they weren't members of their Local Group.

Taxi!!!!!

"If you're not going to order anything I'm going to have to ask you to leave." says the barman

"We do want a drink" says the first galaxy, "but there's too much choice. We just keep going around and around and around!"

…think about it…

…does this joke only work in the UK?

"Why can't I get in?" says the older galaxy.

The bouncer says, "Because you're a barred spiral, that's why!"

the first galaxy orders a glass of mogen david.

the rabbi looks at him and says, "that's funny, you don't look jewish."

To make clear and give an explain; There is strong implication that the evolution of the barred spirals are both sonewhat transitent for galaxies of this sort.

The quote of Brudce Elmegreen – a staunch investigator of galaxy formation and evolution is quoted only in saying; "The tiny elongations in the stars' orbits grow and they get locked into place, making a bar. The bar becomes even stronger as it locks more and more of these elongated orbits into place. Eventually a high fraction of the stars in the galaxy's inner region join the bar" explains how bars are forned, but it doesn't explain there dissolution and their general instabilities.

As for the evolution of galaxies, there is a view that there is during the formation of galaxies that there is significant transfer exchange (c.99%) of angular momentum between the central disk out to the spiral structure. [1] As they evolve, they reverse this exchange, and instead tend to form a single bar in the core of the galaxy

It has been known for sometime, that there has some strong evidence that the spiral arms are feeding gas into the central regions by sprial patterns. This seemingly explains the unexpectedly bright nuclei of some Sc or Sd sprials. I.e. NGC 1300 in Eridanus, NGC 1097 and NGC 1365 in Fornax.
One of the best recent papers explaining the phenomena (via simulations) was made by Bournaud et al. (2005), who found their lifetime as finite, and these may only exist of one to two billion years before disintergrating. He explains that the bars eventually; "weaken due to growing central mass concentrations, and due to the gravity torque and angular momentum transfer from the infalling gas to the stellar bar."
Bournaud et.al. (2005) [2], again explain this in a seperate paper, he says; "But another overlooked mechanism, the transfer of angular momentum from the in falling gas to the stellar bar, can also strongly weaken the bar. In addition, we show that gravity torques are correctly reproduced in simulations, and conclude that bars are transient features, with life-time of 1-2Gyr in typical Sb-Sc galaxies…"

Even more recently, Dabattista & Victor (2006) investigated the disk structure in barred spirals bt doing computer simulations and mesing with the parameters. Here they found other torque effects were placed on the bar, determining that; "We find that bars are robust structures that survive buckling and require a large (~20% of the total mass of the disk) central mass concentration to be destroyed."

An example of some of the computer simulations and investigations into barred sprils as made recently by Saigo et.al. [5]

"The bar mode changes the… disk into a fast-rotating bar. The angular momentum is transferred from the bar to the outer infalling envelope, and spiral density waves are emitted outward. The bar shrinks into a smaller round disk after the angular momentum transfer. This increases the accretion rate temporarily. The disk grows through accretion and becomes unstable against the bar mode again. Accretion is dynamical and that its rate is highly variable in the early disk."

Those interested in the dynamics and evolution of barred spirals should see Sellwood (1996) [6]

This better explains the last paragraph of Nancy's article, which states;
"The formation of a bar may be the final important act in the evolution of a spiral galaxy," [Kaitik] Sheth said. "Galaxies are thought to build themselves up through mergers with other galaxies. After settling down, the only other dramatic way for galaxies to evolve is through the action of bars."

There is also some recent work on barred spirals, in that they may form, dissolve, then form again over several billion years, whose process ramps up the star formation, then relaxes for a while, reorganises, then starts the process again. They may also do so in different periods, depending on the size of the galaxy and the way they were organised when they ere first formed.

Again, like most of the star formation regions, angular momentum. its conservation, and dissipation of its energy are the keys to the
final outcomes of the celestail object we observe. (Its a pity that we don't educate novices of its importance and fundemental importance in object formation and evolution. Were it so, ths Press Release may have had far more impact.

As a comment, I think the problem with the NASA Press Release from the Hubble SIte is that it it too slick for what it is trying to explain to the novice or advanced novice.

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As too the "joke", I think it is a terrible distraction from the gist of the article, and from the responses I figure that many have missed the point altogether.

Two galaxies walked into a bar and said; "let's go ballroom dancing" In barred spirals, at least, their mutual gravitational embrace is far more elegant. (Also the closer you move together, the faster you go – courtesy of the conservation of angular momentum.

References:
[1.] Jan Palous "The Evolution of Galaxies". (2007)

[2.]Bournaud, F.; Jog, C. J.; Combes, F. (2005) "Galaxy mergers with various mass ratios: Properties of remnants"

[3.]Bournaud, F., Combes, F., B. Semelin: MNRAS., 364, L18 (2005).
"The lifetime of galactic bars: central mass concentrations and gravity torques."

[4.] Debattista, Victor P., "The Secular Evolution of Disk Structural Parameters" ApJ., 645, 209 (2006)

(5.] Saigo, Kazuya; Hanawa, Tomoyuki; Matsumoto, Tomoaki; "Evolution of First Cores in Rotating Molecular Cores" ApJ., 645, 381 (2006)
[6.] Sellwood, J. A.; Bar Formation, Evolution and Destruction.

The old galaxy says "have you read Universe Today?"

The young galaxy replies "it's ghey."