Aug. 31st, 2006

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Gamma ray bursts were first detected by the American Vela satellites, deployed in Earth orbit in the 1960s to detect nuclear weapons explosions on Earth. Bursts astonished astronomers of the time by their sheer power: the most powerful bursts manage to convert nearly a Solar mass into gamma rays in the space of a few seconds. Current astronomical theories suggest that gamma-ray bursts are product either of the collapse of supermassive Wolf-Rayet stars into black holes or of the collisions of two neutron stars orbiting in a binary.

Gamma-ray bursts are relevant to people on Earth because of their exceptional power. The brightest gamma-ray bursts, GRB 990123, was briefly as bright as Neptune despite being roughly twenty trillion times as far away from Earth. That gamma-ray burst took place 9.6 billion light years away. A less powerful burst has been proposed several years ago as the cause of the Ordovician mass exintction 443 million years ago. If, for whatever reason, that gamma ray burster had been stronger, Earth almost certainly would have been sterilized. Might bursts, some wonder, explain the apparent and mysterious lack of extraterrestrial civilizations? (And what about us in the future?)

Fortunately it seems that we don't have to worry about death coming from the stars in that way. Via [ profile] alexpgp, Space Daily reports that we in the Milky Way Galaxy seem to be safe. Maturity counts for much.

Reporting in the May 10 online issue of Nature, a team of astronomers said they analyzed 42 long-duration GRBs - those lasting more than two seconds – using the Hubble Space Telescope. They discovered that the galaxies in which the bursts originated tended to be small, faint and misshapen. Only one burst occurred in a large spiral galaxy similar to the Milky Way.

In contrast, supernovae - also the result of collapsing massive stars - were found in Milky Way-sized spiral galaxies roughly half of the time.

The results indicate GRBs form only in very specific environments, which tend to be different from those found in the Milky Way.

"Their occurrence in small irregulars implies that only stars that lack heavy chemical elements (elements heavier than hydrogen and helium) tend to produce long-duration GRBs," said lead author Andrew Fruchter of the Space Telescope Science Institute.

This means long bursts occurred more often in the past when galaxies did not have a large supply of heavy elements.

Galaxies build up a stockpile of heavier chemical elements through the ongoing evolution of successive generations of stars. Early generation stars formed before heavier elements were abundant in the universe.

The astronomers also found the locations of GRBs differed from the locations of supernovae - which occur much more frequently. The GRBs were far more concentrated in the brightest regions of their host galaxies, where the most massive stars reside. Supernovae, on the other hand, seem to occur throughout galaxies.

"The discovery that long-duration GRBs lie in the brightest regions of their host galaxies suggests that they come from the most massive stars - perhaps 20 or more times as massive as our Sun," said co-author Andrew Levan of the University of Hertfordshire, in the United Kingdom.

Massive stars abundant in heavy elements are unlikely to trigger GRBs, because they may lose too much material through stellar winds emanating from their surfaces before they collapse and explode. When this happens, the stars retain too little mass to produce a black hole, a necessary condition to trigger a GRB.

I'd much prefer for there not to be any anomalous Wolf-Rayet stars or neutron stars on collision course hidden in the centre of our Galaxy. There aren't any, of course. Right?
rfmcdonald: (Default)
The problem with Dr. Paul LaViolette's recent book Decoding the Message of the Pulsars: Intelligent Communication from the Galaxy is that it's so compelling. Might pulsars in fact be actively manipulated extraterrestral communications beacons? This might be so.

While scientists continue to work on the complex and perplexing mechanics of pulsars, most of them are not inclined to view them as potential alien transmission devices. The broader scientific community does however support the Search for Extraterrestrial Intelligence (SETI) initiative. The support that SETI enjoys is likely due to the fact that it represents something of an agnostic view of ET. Its primary goal is to detect signs of intelligent alien life, scanning the skies for electromagnetic waves in the hope that we can pick-up the signals of an alien civilization within our giant galaxy. But this method is riddled with difficulties and assumptions about the aliens themselves. For instance, there are the impracticalities of transmitting radio signals due to the power required to send a signal over vast distances, as well as determining what frequency to use. And just what are we supposed to be listening for exactly? And as for the aliens, assumptions abound! Their technologies would need to be relatively comparable to our own. They would also need to be living in a time period coinciding with our own civilization's existence - a big ask, considering the age of the universe compared with the age of humanity. And these aren't the only assumptions and limitations associated with the SETI project, but they're enough to give you an idea of the difficulties involved.

The idea that pulsars are an alien engineered form of galactic communication isn't greeted with much enthusiasm by the scientific mainstream. But scientific uber-maverick Paul LaViolette, author of The Talk Of The Galaxy, who has a background in astronomy, climatology, and systems theory, claims that the more we learn about pulsar signals, the more mystifying they become. Some of this strange behavior includes the intricacies of pulse sequencing observed by researchers that cannot yet be accounted for. Part of the problem may lie in the fact that observations of pulsars do not coincide with the models we've created. Astrophysicist Gerry Zeitlin, an advocate of LaViolette's work and firm believer in the status of pulsars as communication beacons, states that: "Out of some twenty different proposed theoretical models of possible sources of these pulsing signals, astronomers settled on the 'neutron star lighthouse' put forward by Thomas Gold in 1968." If LaViolette is correct in his idea that pulsars are galactic markers created by an alien civilization, then this analogy of pulsars as lighthouses, at least functionally, may not have been far off the mark.

I altogether lack the scientific training to be able to independently evaluate LaViolette's claims. I was skeptical of the sorts of people and publishers praising the book, but that was unfair. My internal alarms were turned on definitely only when he began talking about the structural similarities between pulsar distribution and crop circles, and about the "Mylar mirrors" that famous French ufologist Jacques Vallée was reputedly kept from talking about. Um, yes.

The merits of LaViolette's arguments have been widely questioned, with a seeming consensus that LaViolette is a classic example of a pseudoscientist. This, the considered evaluation and dismissal of a certain set of arguments made badly, is a good thing.

Well, mostly. LaViolette seems to be the most visible person making claims about pulsars and SETI, and I worry whether LaViolette's lack of credibility will unfairly colour people's judgements as to the overall plausibility of possible SETI-pulsar connections. I'd be rather surprised if there were actual connections between extraterrestrial civilizations and pulsars, but it seems at least superficially possible that one might exist elsewhere without having to throw in galactic civilizations of unmatched power sending secret messages to Earth that get intercepted by shadowy government agencies. Perhaps I'm being premature, but these vast networks never sounded plausible even when I liked watching The X-Files.

Why is it that these possibilities attract the same sorts of people as these conspiracies?
rfmcdonald: (Default)
Last night, I went with the boyfrend on an enjoyable walk about Bay Street, Toronto's financial district, heading at least as far as the famous intersection of Bay and King that's the effective capital of Canada's banking industry. Many enjoyable things were done, including catching elephants visiting their watering hole and racing chairs down the platform of King subway station.

Spontaneity works quite nicely, I've discovered.
rfmcdonald: (Default)
Well. This explains that [ profile] toronto posting.

A section of downtown Toronto shut down amid a bomb scare this afternoon will reopen around 4:45 p.m., police said.

The incident occurred when a man enetered a cab and said he had a bomb.

The Emergency Task Force, bomb disposal unit and trained negotiators attended the scene at Bloor and St. George Sts., where the man remained in the cab from about 1:40 p.m., said Staff Sgt. Kevin Suddes.

"We have a report form a cab driver that picked up a fare (that) a male adult in the taxi said to him that he had a type of bomb," said Suddes. "The taxi driver parked the taxi cab and then called 911."

The taxi driver was no longer in the cab, Suddes said. The type of bomb the man said he has was unknown.

Bloor St. was evacuated and blocked off to traffic in all directions at St. George as trained negotiators talk with the man in the cab, Suddes said.
The man was eventually taken to hospital and there was no bomb, police said.

When I passed by at 4:30, the taxi cab in question was still hitched to a police tow truck, and yellow police tape and onlookers abounded.
rfmcdonald: (Default)
Kensington Market's Minsker Synagogue has suffered, on top of a long-term trend for Jews to move north along the Bathurst Corridor, the after-effects of a disastrous 2002 fire. Today's Toronto Star paints a hopeful picture for the synagogue's revival under the tenure of Cleveland-born rabbi Shmuel Spero.

Inside the synagogue, with its creaking floors, wooden pews and stained glass windows, Spero has gathered an eclectic bunch. Young and old. Orthodox and non-Orthodox. Rich and poor. They're all a part of this congregation.

Spero wanted to work at Anshei Minsk for one reason. "I liked the idea of involvement in Jewish outreach in a downtown setting."

Outreach means helping urban Jews become more connected to their religion. More than 100 Jews have started observing the Sabbath since Spero joined Anshei Minsk.

But that's only part of what outreach means to Spero. He offers counselling "for life problems," he says.

He encourages students and out-of-town visitors to eat a meal with the congregation on Friday nights. "We had people from the AIDS conference here," he says.

He also welcomes homeless Jews to participate in synagogue life. "These gentlemen come and they sit with everybody else during (prayers), during classes, during meals. And they're as much a part of the shul as anyone else," he says, using the Yiddish word for synagogue. "It affects them. It enables them to grow as people.

"A synagogue like this has to really be a synagogue centre. A centre is a place where people feel comfortable to come for ... prayer, education, and ... to socialize," he says.
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