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July 09, 2007

"42": Hitchhiker's Guide to the Galaxy Foreshadows Actual Weight of Universe!

42_2 I'll be damned! Douglas Adams nailed it! The mystical number in the Hitchhiker's Guide to the Galaxy, 42, is a key number in predicting the actual weight of the Universe.

As you may remember, the Answer to The Ultimate Question Of Life, the Universe and Everything is simply "42," the numeric produced using the hypercomputer, Deep Thought, after a very long computation time (7.5 million years).

But Deep Thought's abilities came up short when asked to provide the Ultimate Question to match the answer of 42. Thereafter, the answer given by Deep Thought prompts Arthur Dent and the Hitchhikers to embark on a quest to discover the Question to which this is the Answer.

Once again, art anticipates science: after pondering the weighty question of the mass of the Milky Way galaxy, astronomers have come up with an answer: 42! Our galaxy weighs three times 10 to the power of 42 kilograms - a number written as 3 followed by 42 zeroes.

It seems esoteric but knowing the weight of the galaxy - the amount of matter it contains - is key to solving the nature of so-called dark matter. Unlike the "ordinary matter" of stars and planets, scientists have only hunches about the nature of the invisible material that, along with "dark energy", they estimate makes up 90-99 per cent of the universe.

What is it? How is it distributed across the universe? Does it really even exist? "That's worth knowing," said Professor Freeman,an astrophysicist with Mount Stromlo Observatory and the Australian National University's Research School of Astronomy and Astrophysics in Canberra said  in an interview with The Australian. So along with colleagues in Australia, Europe, the US and Britain, he decided to "weigh" a galaxy.

The problem is there's no good way to quantify all the dark matter in distant galaxies, thus making it difficult to total all the matter, dark and ordinary. So Freeman and his colleagues focused on our home galaxy, the Milky Way, an average sized spiral galaxy, containing a few hundred billion stars (keep in mind that there are some 100 billion galaxies in the observable universe, each containing more or less the same number of stars).

It has been determined that there is a roughly spherical halo of dark material stretching out to distances of perhaps 10 times as far from the center of the galaxy as we are.

"Because we're inside our galaxy, we can get a more reliable measure of the dark matter content than we can for galaxies outside," he said.

To do so, the group first estimated the "escape velocity" of the galaxy - the speed stars passing near the sun needed to attain in order to escape its gravitational pull. It did so using the line-of-sight, or radial, velocity of stars crossing the central rotating disc of the galaxy.

The data was collected by the 1.2m Schmidt Telescope of the Anglo-Australian Observatory at Siding Spring, NSW. The escape velocity, calculated at between 544km/sec and 608km/sec, allowed the team to calculate the Milky Way's mass and weight, as well as the amount of dark matter: 94 per cent.

Wow...that's cool! We think Professor Freeman and team should be awarded the "Galactic Institute's Prize for Extreme Cleverness."

Posted by Casey Kazan.

Related Galaxy Posts:

1st 3-D Map of the Universe's Dark Matter

Cosmic Collision  Sheds Light on Mystery of Dark Matter

GAIA -Mapping the Family Tree of the Milky Way

New, Revised Hitchhiker's Guide to the Galaxy
 

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Comments

Great blog btw, fascinating stuff. Nice link to Douglas Adams too!

Holy crap, now I'm going to have to read those books again!

Oh well, with so many uncertainties I would've round it to 42 zeros, even if it were only 40 if I was them. Those scientist have read the book too!

O, and I think Earth would be useless now the answer is known. Wasn't the Earth created to calculate the answer?

Just kidding. This post put a smile on my face. I've read the books many times.

I really need to start checking my posts before clicking submit.
The Earth was created to calculate the *question*, not the *answer*; Duh

Roughly speaking, the amount of mass observable Does only have 40 zeros. It's the UNobservable mass that adds the 2 more zeros. While these guys round up and down like we all do, they understand the difference in going for a 3 mile jog and a 300 mile jog...

I hate to be picky, but the galaxy has no weight. Weight is a measure of how much the gravity of a planet is pulling on an object. Example, astronauts weigh less on the moon than the do on the Earth. The measure your looking for is Mass. The mass of the Milky Way is 10 to the power of 42.

If you take a gravitational source, add up the relative weights of an object from all positions on a sphere equidistant from the center, positive and negative, the total is 0. Add all gravitational sources, the total is 0.

Therefore the galaxy weighs 0, with a mass of 3 X 10^42, if you agree with deep thought and the people that came up with it, which I don't because I'm not ready to stop my program...

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