Saturday, 14 July 2007

Astrophysics directions

Recent years have been very fruitful for astrophysics. Sometimes even to the point of overeagerness in accepting new paradigms. For example I am somewhat surprised with the speed of acceptance of the Dark Energy (73%) / Dark Matter(22%) / Normal components (5%) model of the Universe.
Yes, I am impressed with the explaining powers of this model, especially with respect to the increasing speed of expansion, but the question is: how did it come about that the scientific community has accepted so fast the Dark Energy explanation (and the Dark Matter as well), without any inklings as to what this Dark Energy is?

More - with the 120 orders of magnitude difference between our possible explanations and the observed value! Yet so many astrophysicists behave in a way as if the problem does not exist.

When the ApPEC and ASPERA, which are consortia of national agencies that pay for astroparticle physics research in Europe, published the report on Status and Perspective of Astroparticle Physics in Europe the collaborators have identified six `basic questions that need to be addressed by the astroparticle community over the next decade:

1. What is the Universe made of?
2. Do protons have a finite life time?
3. What are the properties of neutrinos? What is their role in cosmic evolution?
4. What do neutrinos tell us about the interior of the Sun and the Earth, and about Supernova explosions?
5. What is the origin of cosmic rays ? What is the view of the sky at extreme energies ?
6. Can we detect gravitational waves ? What will they tell us about violent cosmic processes and about the nature of gravity?

As for the question 1, the particular focus is on Dark Matter, which is described as
`Dark Matter turns out to be the majority
component of cosmic matter. It holds the Universe together through the gravitational force but neither emits nor absorbs light. Dark Matter (including a small admixture of massive neutrinos) has likely played a central role in the formation of large scale structures in the Universe. Its exact nature has yet to be determined. The discovery of new types of particles which may comprise the dark matter would confirm a key element of the Universe as we understand it today.

But for the Dark Energy, the report states only that `The nature of dark energy remains a mystery, probably intimately connected with the fundamental question of the cosmological constant problem.'

The plans are - one should notice - made by astroparticle
rather than astrophysics organizations. So, perhaps it is not too surprising that in the list of planned and supported experiments the authors state:
`It is this part of the search for Dark Matter that we assign to the field of astroparticle physics. Dark Energy has a similar density to dark matter; unveiling of its nature would have profound impact on astroparticle physics. On the other hand, current projects exclusively rely on tools of astronomy; therefore we express strong support for dark energy projects but leave detailed recommendations to the strategic planning of astronomy roadmaps.'

Despite these remarks (perhaps written slightly tongue-in-cheek), the report is very clear and can be a good initial review on the current state of knowledge. Recommended reading!

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