Posted by simoniker (30% noise) View heyitsme writes “Fermilab, a U.S. Department of Energy research lab, is part of a collaboration on an experiment to measure the properties of dark energy. The Dark Energy Survey would measure the history of the expansion rate of the universe more precisely than ever before, using the largest camera ever built with Charge Coupled Devices (CCD). The 500 megapixel Dark Energy Camera (DECam) would be placed on an existing 4-meter telescope located in north-central Chile at the National Optical Astronomy Observatory’s Cerro Tololo Inter-American Observatory. The DECam together with the CTIO 4-meter telescope will allow for a survey of 15 percent of the sky to light levels faint enough to measure the colors of galaxies at redshift one.”
why you need 500 Mpx - by sdedeo (Score: 5, Informative) Thread
(Not an expert, they’re all fast asleep right now.)
One of the things Fermilab is trying to do is get a measurement of the so called weak lensing effect. Matter distorts spacetime, and light is thus bent as it passes nearby a big cluster. This is gravitational lensing.
Famously, it is seen as “strong” lensing — when the source is very close on the sky to the cluster, and the light gets bent enough that there are multiple images. Nobody really believed it could happen, but then in the last decade or so it’s become an accepted and popular thing to play with and observe.
Weak lensing is when there are no multiple images, and instead only a slight distortion. Much harder to see and measure — you basically look for a whole bunch of galaxies that are slightly distorted.
That means you need a very wide field of view — to get enough galaxies quickly enough — but also a very good resolution — to be able to measure the slight distortions. Hence the need for such an insane[ly cool] device.
Why go through all this trouble? Well, weak lensing is one of the view ways to measure all the matter in the universe on very large scales. Because nearly all the matter is supposed to be invisible, in the past people have used various “tracers” that we can see. But there’s a huge amount of debate as to how good the various tracers are, and, of course, you need a direct measurement to be sure you’re not off in la-la land.
Weak lensing measures it all because all matter, regardless of how bright it is, bends spacetime in the same fashion. So, if you can get a good weak lensing measurement, you can theoretically create an unbiased map of the matter distribution. No need to cross your fingers and hope that some tracer is behaving properly.
It all fits into dark energy because dark energy is supposed to alter the extent to which matter can cluster (roughly speaking, dark energy behaves like antigravity, and pushes things apart, stopping them from falling together.)
Of course, weak lensing is just one of the things this guy is meant to do — there are lots of other neat things that hopefully someone more awake than I can describe.
500 megapixel?? - by fodi (Score: 3, Funny) Thread
I dont EVER want to be photographed in that much detail !!
I’m glad - by toddhunter (Score: 3, Funny) Thread
That they were able to save money by using an existing telescope.
Because the compact flash cards for this thing cannot be cheap.
Filesize? - by FSWKU (Score: 4, Interesting) Thread
I would hate to see how much space one frame from this thing takes up…
Re:Filesize? - by BWJones (Score: 4, Informative) Thread
Although the article does say 500 megapixel, a simple calculation could answer your question. The CCD is composed of elements giving it a pixel array of 180k X 240k pixels giving us 28800000000 pixels! (Assuming each pixel holds one grey value in a 16 bit image ) Working from 16 bits/pixel and 8 bits/byte, we are looking at 2 bytes per pixel. So 2 bytes * 28800000000 pixels gives us 57600000000 bytes or almost 54 GB/image!
If you were to take multispectral or even RGB images, one would multiply the file size by the appropriate dimension…
Posted by CowboyNeal (36% noise) View
Nephilium writes “Reason magazine has dedicated their latest issue to a discussion of privacy and data collection. They sent subscribers a customized cover of the magazine [as previously covered on Slashdot]. Some good points as to the benefits and drawbacks of who is sharing your information.” The sample targeted advertisements are for non-profit organizations, but it may not be long until someone figures out how much companies will pay to utilize this sort of targeting.
Simple way around all this - by MajorDick (Score: 5, Insightful) Thread
PAY FRIGGN CASH, GREEN, Dead Presidents,
Im serious, between paying cash where possible, that includes nearly EVERY local purchase, trade you key tags for grocery stores with your friends (as long as they arent valid for cashing checks)
No tinfoil here I just cant stand direct marketing, why in the hell should I give Radio Shack my phone number, I actually had a clerk say they HAD to ge one, 555-1212 or 867-5309 (867 is a local extension here) is my answer most of the time they dont even blink although some chuckle
Lay as low as possible, p[ay cash where possible and lie like hell when anyone asks any questions that could be used in targeted marketing.
Dont forget they found one of the 911 conspirators by his grocery store key thingy
Cold and unbiased… - by LostCluster (Score: 5, Interesting) Thread
One thing the whole FICO-based credit system has working in its favor is that it is very truely blind. The decision maker doesn’t get to look at you physically at all, it’s not even a person anymore. Simply put, if the prediction formula gives you enough points you’re accepted, and if it doesn’t you’re declined. Race, age, gender, religion, sexuality… who cares.
Of course, the system isn’t perfect, it’s subject to GIGO just like any other computer system. However, compared to human decision making, it’s a whole lot of a more fair process on the whole.
Regaining Privacy in the US - by pholower (Score: 5, Interesting) Thread
I agree, there is almost no privacy in the US for this sort of thing. But if you have already given your information to be hoarded in databases, and cross linked with other databases, then there is little one can do to regain their privacy.
Wired Magazine a year or so ago, I remember, had a page on how to regain privacy. Some of those tips included:
- Gaining access to a fake SSN
- Not using a Cell phone
- Never using a credit card
- Do not have a mortgage
Something most Americans are incapable of doing without moving to the woods and living off the land.
Targeted Content - by ePhil_One (Score: 5, Interesting) Thread
I’m more concerned about when publications will start publishing customized content, So that Rush Limbaugh thinks MagA is a conservative read, and Ralph Nader thinks its a left wing read.
Double your readership ;)
Re:Targeted Content - by PsychoFurryEwok (Score: 5, Interesting) Thread
That’s actually a really interesting concept. With us being able to use computers to print out something different on each page, they could just set it up to run through their list of subscribers…use feedback to customize the magazine for them. Brings up another issue though…now you’re forcing everyone to see something as only one sided. :)
It is scarry what the integration of databases can do. It can be done for good, like credit rating, or for bad like almost any governmental usage. Scott McNealy said that we should get over our lost of privacy. I disagree: We should fight to get it back!
