Thursday, March 24, 2005

Vacuum density...

No I'm not referearing to the average number of vacuum per sqr km in Canada but instead to that little strange and interesting we weird astronomy people call dark energy. This post mark a new escalation in the blog war... the use of mass weapon of mass education, something my archnemesis can not compete against! (Beside ain't the best blog suppposed to be funny, edgy, ranty, smart, sexy, AND educational?)

For those not following scientific news (and frankly who out of the scientific communauty does that?) dark energy is a strange force which seems to be pushing everything in the unverse away from everybody else (kinda like what fast food does to one's waist...). It is called dark energy to "mirror" dark matter (if you're really out of it dark matter is the matter that existe but that for some reason we can't see) simply it not dark or evil or event shadowy it was simply unknow for a long time and it is hard to find (heince it fits with the "dark" background of space). Now you're probably all wondering what it is... well so are we (by we I mean astrophysicist). We know how it works in comological equations (it fits with Einstein so-calledgreatest mistack the cosmological constant Lambda) but it's nature as a sort of anti-gravity is puzzeling to say the least.

For the more scientificly minded here is how we found evidance of it existance. First you have to know that the universe is expanding. According to cosmological theorie in the absence of dark energy the universe can at most accelerate at a constant rate (if there is less matter and dark matter then the critical density) while if there are dark energy it is possible to have an universe that would forever accelerate (event in the presense of critical density of matter and dark matter). Now one has to measure the acceleration of the universe, not a small feat you can guess. So we know that all type I supernova (explaination in a later educational post) have the same base luminosity and we can measure there distance from their spectral redshift (something simillar to the doppler effect of receiding galaxies). Next from the luminosity observed and the base fixed luminosity we can determine the distance. Recently measurement have shown that far away supernovae speed away from us faster then they should according to models without dark energy... we must then conclude that the universe is expanding and accelerating which mean dark energy.

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