Cosmology@Home lets you volunteer your spare computer time (like when your screen saver is on) to help search for the model which best describes our Universe and to find the range of models that agree with available cosmological and particle physics data.

conceptFEATURED CONCEPT: Dark Matter
Unlike ordinary matter, dark matter does not emit or absorb light--or any other type of electromagnetic radiation. Consequently, dark matter cannot be observed directly using a telescope or any other astronomical instrument that has been developed by humans. If dark matter has these strange properties, how do we know that it exists in the first place?
Like ordinary matter, dark matter interacts gravitationally with ordinary matter and radiation. Astronomers study the distribution of dark matter through observing its gravitational effects on ordinary matter in its vicinity and through its gravitational lensing effects on background radiation. The background image shows the bullet cluster, a famous example where the visible matter does not follow the mass distribution.
Combining all the available evidence, dark matter represents about 83% of the matter content of the universe. Read more about dark matter on this web page. Let us know your questions and comments on the message board.

User of the Day

User profile Profile Kajunfisher
A bad day fishing is better than a good day at work. I am just a simple country guy crunching for a few distributed computing projects. I try to...


Downtime Explanation
Hi all, apologies for the extended downtime we had the past few days. We had a hard disk failure that, since it came over the weekend, took a bit longer to resolve than usual. We are back now and there was no data loss, however its possible some of your clients missed reporting deadlines (since we were unavailable). If you feel you lost significant credits because of this please don't hesitate to contact me. We're working on making sure similar errors in the future can be resolved quicker. For now, sorry again, and happy crunching! 13 Feb 2017, 11:53:22 UTC · Comment

Move Completed
And we're back! The server move to France appears to have gone well. We'll continue monitoring things closely to make sure the new machine is working well. Please let us know if you find any problems, and happy crunching! 15 Dec 2016, 9:11:33 UTC · Comment

C@H Move and Server Downtime
Tomorrow the C@H server is packing its bags and getting ready for a big move! After 10 great years of being hosted at the University of Illinois in Champaign-Urbana, we are moving overseas to Paris on a server at the Institut d'Astrophysique de Paris, where both myself and Ben are currently working. You can read more about this in an updated welcome letter from Ben.

At 2pm UTC on Wed Dec 14, we will take the server offline. The process may take up to 24hrs, during which your clients will still process pre-downloaded jobs, but will not be able to communicate with server. Upon finishing the move, you clients will reconnect automatically, and no actions from you are necessary. For the ultra-curious, I will try and post some live updates tomorrow on my twitter.
13 Dec 2016, 15:38:46 UTC · Comment

Server status
Hi guys, over the last several days the site has been suffering from what ultimately was a database error that caused several of the problems some of you have been posting / emailing about. Sorry for the slow response with the holidays here, but we should be fully back online at this point. Until everything is flushed out, there may be some workunits which will be screwed up as a result unfortunately. If you feel like you lost a significant amount of credit as a result of this, or if you notice anything still not working, please don't hesitate to PM me with more details. Happy crunching! 26 Nov 2016, 11:46:43 UTC · Comment

Some security and cosmetic upgades
We have added the option to access the C@H website more securely via "https", if you'd like to do so, you can update your bookmarks to use For now this remains purely optional (for example, if you don't know what https is, you can ignore this). At some point in the future, we will likely move to requiring this, but we'll give warning and post more details then.

Also, I've fixed a number of minor cosmic things about the site, most notably 1) the BBCode buttons when posting to the forums now work 2) a number of pages which were rendered too wide should now correctly fit the screen. If, as you're using the site, you find any other glitches, please don't hesitate to take a screenshot and post on the forums so we can fix things! Thanks all! (Edit: ha, oops meant to say *cosmetic* things above, although I'll leave in the somewhat appropriate typo)
22 Sep 2016, 15:19:08 UTC · Comment

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