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First Cosmological Results From MAP
riptalon writes "The Wilkinson Microwave Anisotropy Probe, a NASA Explorer mission has announced the first results based on a year of observations from the L2 Lagrangian point. MAP carries two
back-to-back microwave telescopes to study variations in the cosmic microwave background, to
much greater accuracy than the COBE satellite. The excruciating details of the results
on the age, geometry and composition of the universe can be found in this paper. Executive summary: 13.7 billion years old, flat, 4.4% baryons, 22% dark matter and 73% dark energy."
13.7 billion years old, flat, 4.4% baryons,
95% We don't know.
More information can be found at (including a cosmology tutorial):
w s
http://www.astro.ucla.edu/~wright/cosmolog.htm#Ne
This press release was mentioned in a post in the previous slashdot story yesterday.
Mass media coverage can be found at CNN and the BBC. A list of all the MAP papers can be found here.
A baryon is a particle such as a neutron or proton. It's one of the two main classes of ordinary matter particles, the other is the lepton (e.g. an electron or neutrino). Baryons "feel" the strong nuclear force, leptons do not.
Dark matter refers to exotic forms of matter that are "ordinary" from a gravitational point of view, that isn't made up of baryons or leptons. This stuff either interacts weakly with ordinary matter, or doesn't interact at all (other than via gravity).
Dark energy has positive energy but negative pressure, so it causes a gravitational repulsion. Einstein's "cosmological constant" one possible example of dark energy. It can be thought of as a property of space.
13.7 billion years old, flat, 4.4% baryons, 22% dark matter and 73% dark energy
Except for the age part, that sounds a lot like my ex-girlfriend.
Happy Valentines Day everybody!
Confused by "Dark Energy," "Vacuum Energy," "Dark Matter," and "Exotic Matter?" Here's a great collection of papers. (Mostly from the SNAP project)
[-- Trust the Monkey --]
"MAP, an Explorer mission, cost about $145 million."
If I understand correctly...
Measuring the age of universe, calculating initial proportions of baryonic matter vs. energy, and deriving shape of universe: $145M.
Shuttle flight to install ISS module: $500M.
Shuttle flight to watch ants float in zero-G: 7 deaths, $500M for launch, $2.0B for new shuttle.
Your Congressional District's seat at the trough of Shuttle/ISS pork: "Priceless."
Now that I've bashed, some constructive criticism - cut NASA in half.
One half - NAA - I'll call the National Aeronautics Administration. Its job will be pure Aeronautics. Launch vehicles. Rockets. Engines. From pricy Shuttles to half-decent Shuttle-C heavy-lift modifications, to cheap expendables, to funky crewed vehicles like X-33, VentureStar, or DC-X.
The other half - N(whoops!) let's call it the NSSA - National Space Science Administration - will do science. Build probes. Stick 'em on rockets built by the NAA, or LockMart, Boeing, or Armadillo, and do some frickin' science.
Under such a scenario, we could have avoided the Shuttle/ISS debacle completely; NAA might have had concerns about losing funding once the last Shuttle was built, and probably would have had a significant incentive to keep asking Congress for funding to build newer, better, cheaper-per-pound launch vehicles.
Why? Because they'd be under competitive pressure from every other contractor under the sun building launch vehicles to launch NSSA's space probes. Perhaps NSSA would have come to the same mistake NASA did - and decided that we Really Needed a Space Station - but even if that were the case, the design requirements of ISS would have immediately mandated a heavy lift vehicle, wholly unlike the Shuttle.
In such a scenario, NSSA would have had the choice between building ISS with three FooCorp Big Dumb Booster flights, or 30-40 NAA Shuttle flights.
Unlike the current NASA monolith, in which both halves exist to feed each other, a separate NSSA would have been loathe to spend its hard-begged budgetbucks to use another government department's (i.e. "NAA's") Shuttle, particularly in the face of cheaper alternatives. (And likewise, NAA, seeing that it had no Shuttle customers, would have been forced to spend its hard-begged budgetbucks building the Shuttle's successor, or find itself on the Congressional chopping block.)
"MAP ... to study variations in the cosmic microwave background, to much greater accuracy than the COBE satellite"
And their web page is better too. My satellite can beat up your satellite!
IBM had PL/1, with syntax worse than JOSS,
And everywhere the language went, it was a total loss...
In this case "vacuum" is physicists' name for "empty space," meaning "as empty as possible." On earth, "empty" means "much less matter than in the atmosphere."
When that empty space is surrounded by the earth's atmosphere, the atmosphere presses on the container that encloses the empty space. Open a hole in the container, and the atmosphere rushes in---that's the sucking part. (Indirectly, it is Earth's gravity that creates the pressure, but you could also imagine the Earth is in a big closed box.)
Intergalactic space is presumably much emptier than any vacuum that we can achieve on earth. When the "empty space" in question is simply surrounded by more empty space, there isn't any sucking of matter. (Pressure is practically zero.)
It turns out that space itself can contain energy; that is, "empty" is not the same as "nothing." General relativity predicts that there is energy in the curvature of space, which is roughly equivalent to the energy in Newton's gravitational fields. (Not exactly equivalent for strong fields, however.) Also, quantum mechanically, there is always the possibility of a particle or field being present in the empty space. That possibility provides a "zero-point" energy, even when the matter or fields are not there. If we really knew all the possible particles and fields, we could calculate what this would be. There might be particles and fields that we haven't discovered yet, or other additions to quantum mechanics that we haven't discovered yet, which is why we have to look to astronomers to determine the properties of empty space.
The energy in otherwise empty space is the dark energy. That energy can cause dynamic behavior in the framework of space, causing it to expand and contract.
[darkhumor style=kurtvonnegut]
It turns out some researchers called it God at first but that doesn't look as well in print outside of sacred texts. You know, "God is everywhere, but unevenly distributed and is repulsive, not that anyone would notice or at least they have not. Only we did notice so we're L337 and we're forming our own religion. We hereby declare all other religions apostate and anathema on the strength of our observations."
We pagans know all about Dark Energy. Heck, we're obsessed with it. Only I'm a little surprised that it's not more than 75% of the known universe. I bet a lot of the Cold dark Matter will turn out to be wanna-be Dark Energy too, just tettering on the edge of going over for the last few billion years.
The idea that only 4% of the Universe is "normal" really lines up with the notion many witches and Zen masters subscribe to, where 96% of Everything is utter nonsense. But you can still have loads of fun with the other 4% if you lay your hands on a good spell book. Just don't forget to close your sacred circle, and properly call the gates, and sanctify your athame first. Bless us but you don't want to upset the balance of entropy and cause any of that loitering Cold Dark Matter to get any fancy ideas.
[/darkhumor]
=^..^= all your rodent are belong to us
L2 is nice for several reasons. The instrument on MAP needs to be kept cold. Sitting at L2, the spacecraft can keep the instrument pointing away from the Sun, and still measuring data, without ever needing to worry about interference from the Earth or Moon, and there is this nice big dish (the solar array) shielding the instrumentation from direct sunlight. In addition, NASA has lots of experience with spacecraft at the collinear Lagrange points (L1 and L2), so the orbits and communications are very well understood there. And L2 is far enough away from the Earth-Moon system to avoid complicated orbit perturbations, but close enough for relatively easy communications (that is, the radio doesn't have to be too big).
Hope that helps!
A signature always reveals a man's character - and sometimes even his name. -- Evan Esar