Friday, April 9, 2010

Big telescopes; Bigger Questions; and Really Big Mistakes

Imagine its 1930, and you’re a veteran Harvard astronomer, talking to ordinary folk about your work.
It’s the most exciting time in your field since Isaac Newton, but its surely sort of embarrassing too.
Those folk might reasonably say to you: “Hey, just ten years ago, most of you people thought our Milky Way galaxy was the whole universe – and now this Hubble fellow tells us there are billions of galaxies just like ours out there.”
Or – referring to Cecilia Payne - they could say: “What’s more, you people all thought the stars were made of IRON, like my CAR, until just last year, when a LADY – someone’s assistant! – proved they’re made of hydrogen gas, which couldn’t be more different! Have you got ANYTHING right?”
Now – in 2010, after a decade of equally stunning new discoveries – Harvard’s astronomers face a remarkably similar time of excitement and embarrassment.
Embarrassment, because – until very recently - astronomers thought they at least knew the basics of what the universe was made of.

Alas, it now turns out they have no idea what 96% of the universe is made of. Dark matter? – there’s ten times more of this stuff than all the stars in all the galaxies, but no one’s identified even a gram of it yet. Dark Energy? – not a clue.
And it gets worse. Their best theoretical models for the strength of this “anti-gravity” force (the one that is accelerating the galaxies away from each other) turns our to be the most numerically incorrect answer OF ALL TIME! – the measured value of this force is 10 to the power of 120 times weaker than the scientists thought.
So – like I said: discoveries to make a rhino blush.
Luckily, Cambridge astronomers get most of it right, and bounce back fast when they don’t.
In 1920, Harlow Shapley – director of the Harvard Observatory – was the losing member of the “Great Debate”, in which he had insisted that the “spiral nebulae” seen through telescopes could not possibly be galaxies outside our own. (Hubble proved him wrong).
But he went on to found the National Science Foundation, and helped turn astronomy into one of the most popular of the pure sciences among the broader public.
In recent times, another famed local astronomer – Robert Kirshner – got it embarrassingly wrong when he declared that the brightest supernova in modern times – “Supernova 1987A” – was a dud, since the star that should have exploded was still there. (In fact, he later realized ruefully that this surviving star was one which had always been behind the exploded star, from earth’s point of view, and that the supernova had been the real thing).
But within 10 years, Kirshner would more than make up for it, as a key member of the team which found that the expanding universe was not slowing down - as it “should” under the influence of gravity - but was accelerating apart. Using a different type of supernova from the 1987A variety (which is powered by gravity) to measure huge distances, their team was able to determine the ultimate fate of the universe: one heck of a statement to tuck in your resume.

The point is: in this field, excitement, optimism and wonder always win over disappointment, and its infectious. So, in 1930, Shapley founded a monthly Observatory Night for the general public, who were invited to peer through its telescopes and learn from its scientists.
These interactive lectures for lay people virtually packed out the Phillips Auditorium on Gardiner Street, and they’ve been doing much the same every month for the past eight decades.
It was here that Carl Sagan briefed the public on the possibility of life on other worlds; that Margaret Geller spoke on her co-discovery of nothing less than the biggest object in the universe – the “Great Wall” of galaxy clusters, over 500 million light years across. (By comparison, our Milky Way galaxy is about 100 000 light years across.) More importantly, she found that this unimaginably large structure was also remarkably THIN – and that it appeared to form the shell around a vast void, like the skin of a bubble. This gave us our first accurate imagining of the whole of creation – a spidery cobweb of uneven threads of stuff and bubbles of nothing.
And the Cambridge Science Festival will commemorate the stellar history of the event with “80 Years of Astronomy” at the same venue, at 7:30pm on April 24.
Event Host David Aguilar says visitors will get to peer through the 9-inch telescope on the roof – just as they did in 1930 – and check out “The Great Refractor”: a 15 inch telescope which was once the best in the world. (Although he’ll likely contrast this once formiddable instrument with the monster 30 meter-wide reflector telescopes now planned.)
In addition to the rich history, Dr Charles Alcock – director of the Harvard-Smithsonian Center for Astrophysics - will reveal the biggest questions facing tomorrow’s astronomers – and the amazing new tools they’ll use to answer them.

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