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."

Comments

Cosmic Microwaves

[Archangel Michael]

Will it heat my cosmic coffee?

Re:Cosmic Microwaves

[$$$$$exyGal]

Woo. That little pun just got me all hot. *takes off sweater, revealing 2 cosmic constants*

--sex

Hey...I need answers here dammit!

[GeneralEmergency]

Does Dark Energy suck or blow?

huh?

[dirvish]

Anyone care to let us non-space nerds know what baryons, dark matter and dark energy are? TIA.

Re:huh?

[JoeBuck]

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.

Re:huh?

[(void*)]

In astronomy, "baryons" can also include "leptons", simply because leptons are included in the mass that one measures using a galaxy rotation curve.

Re:huh?

[Peter T Ermit]

Nope. Baryons are the heavy particles made up of three quarks. Leptons are light particles that are themselves fundamental particles. In between are mesons, made of a quark and antiquark.

Re:huh?

[adminispheroid]

You missed the part where he said "in astronomy." In astronomy, a lot of wrong things are true. In this case, when astronomers say "baryons" they mean "baryonic matter" i.e. atoms, molecules, ions, etc. which includes the electrons. Of course, in baryonic matter the electrons make up something like 0.02% of the mass, so it's hardly worth quibbling about.

Re:huh?

[Captain Nitpick]

In astronomy, "baryons" can also include "leptons", simply because leptons are included in the mass that one measures using a galaxy rotation curve.

Nope. Baryons are the heavy particles made up of three quarks. Leptons are light particles that are themselves fundamental particles. In between are mesons, made of a quark and antiquark.

You've got to remember that the terminology astronomers use is a bit...different. This is much like how they call anything heavier than helium a "metal".

Re:huh?

[Peter T Ermit]

First, he said baryons, not baryonic matter -- you will never hear any astronomer call a lepton a baryon.

Second, technically, even in astronomy, baryonic matter is only the nuclei -- the leptons are counted separately, though they're unimportant masswise, as you mentioned. Here's why.

There are several ways of computing the amount of and types of matter in the universe. One of the most important is examining primordial gas clouds and looking at the relative abundances of hydrogen, helium, and lithium and their various isotopes. This tells us about the era of nucleosynthesis -- the time 3 seconds to 3 minutes after the big bang when the temperature and pressure of the universe was enough to induce nuclear fusion. After 3 minutes, this process ended and froze the ratios of primordial elements.

By looking at those ratios, scientists could figure out the abundance of those nuclei -- the nuclei, not the leptons, which don't affect the ratios at all. From this, they can figure out the density of nuclear matter in the universe, which is related to a quantity known as omega sub b. This number is thought to be about 4.5% from measurements of the elements in those gas clouds -- and MAP confirmed this by a different method. But this baryonic fraction does not have anything to do with the leptonic component of matter... including electrons and neutrinos.

So, when astronomers say that they have shown that 4.4% of the universe is made up of baryonic matter, they really mean baryons. It just so happens that there are pesky leptons hanging around the baryonic matter, too.

Re:huh?

[efuseekay]

nope.

Astronomy/astophysics pays my bills, and I can tell you that 4.4% of baryons from WMAP really means anything that is known in particle physics as quarks, leptons, blah blah blah.

A rule of thumb is that 'baryons' in astronomy/astrophysics is anything that is in the standard model (sans the higgs.)But that's not the whole story.

"baryons" (in the 4.4% of WMAP) is classified as matter that is not "dark". "Non-dark" means it interacts with other stuff and itself beyond just pure gravitation. That includes "radiation", which is stuff that behaves relativistically, and include things like photons, neutrinos,a nd perhaps other relics.

To summarize, there is no difference between "baryons" and "baryonic matter" in astronomy.

I will not call a lepton a baryon, but I will definetely lump leptons in when I say 4.4% of ther universe is made out of baryons. it's just a matter of context, and people in the field will udnerstand that.

Really, astrophysicists are sloppy when it comes to naming stuff. So you have to be careful not to read too much into nomenclature like this, even in the era of "precision cosmology".

Flat?

[captain_craptacular]

Tell that to Columbus.

Why do they call it "Dark Energy"?

[lingqi]

Really, now. That just makes the universe sounds sinister. I can just imagine Vader argue with Yoda in Ep.III (cutting out the huffing) "Ahh you see master yoda, the universe is mostly the dark side." Can't they go for a policitally correct / socially sensitive / thoughtful of the children phrase like "cannot-see energy" or "we have no fscking clue where it is energy"?

otoh, iirc the original background radiation measurements were done using a U2 (not the band, though it would be interesting) flying at some 70k ft, something about only a U2 can fly that steady (without resorting to satelites, anyway).

Re:Why do they call it "Dark Energy"?

[theCat]

[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]

courtesy of Wikipedia

[goatasaur]

Baryons

Dark Energy

Dark Matter

Hope this helps you out a little. :)

Re:courtesy of Wikipedia

[Scud_the_disposable_]

from the definition of dark energy:

This energy would act like a vacuum pressure, pushing things apart.

now I ask you... what is vacuum pressure, and how does it push things apart? I thought vacuums sucked things in...

Re:courtesy of Wikipedia

[jaoswald]

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.

Re:courtesy of Wikipedia

[Anonymous Coward]

Stephen Hawkin, in his book "A Brief History of Time", says (when talking about Black Holes) that there can't be "empty space" because of the Uncertainty Principle, and thus what is known as "empty space" is really particles and antiparticles creating and destroying each other all the time.

He then goes to say that for each pair of particle-antiparticle, one can be sucked into the Black Hole while the other, failing to be destroyed by it's counterpart, escapes and allows us to detect the black hole.

He then goes into saying that because an antiparticle would behave exactly the oposite than the particle, what would appear to be a pair being created and destroyed, would really be a particle going forward and backwards in time in a "circular " manner... and we would see it as a particle - antiparticle pair.

But I'm not and physicist, so I wouldn't know better than what Stephen Hawking wrote... anyone care to elaborate?

Cheers.
Me

Re:courtesy of Wikipedia

[WatertonMan]

What is funny is that "dark energy" is also termed "quintessence" or the fifth element. Quintessence was an other term for aether which, as you might recall, was the nebulous stuff in the cosmos prior to modern physics. Funny how things we thought we disproved pop back unexpectedly.

Of course aether was primarily brought up by Maxwell to explain certain phenomena. It was disproved by the "fact" that the speed of light was a constant in all inertial frames.

What's interesting is that there is a movement to suggest that perhaps, just perhaps, the speed of light wasn't a constant after all. While I rather doubt that, New Scientist has an interesting interview with the main proponent of that theory, Joao Magueijo. Interview with Joao Magueijo

He has a book partially about this coming out this month called Faster than the Speed of Light

I rather doubt Einstein is wrong on this matter, although some of Magueijo's criticisms of superstring theory are often made. Still quite a few people are discussing the issue. Landau, for instance, has a recent paper on the topic. "Charge Conservation and Time-Varying Speed of Light.

To tie all this together, here's an interesting paper that ties some of this all together, including "dark energy." "Perfect Fluid Cosmology with Varying Light Speed."

Re:courtesy of Wikipedia

[Zak3056]

What is funny is that "dark energy" is also termed "quintessence" or the fifth element

So, basically, it's Milla Jovovich?

correction

[zaqattack911]

13.7 billion years old, flat, 4.4% baryons,
95% We don't know.

Re:correction

[Old Wolf]

4.4% baryons, 95% we don't know, 0.6% people with no mathematical training

Re:correction

[Greedo]

13.7 billion years old, flat, 4.4% baryons ...

... and may contain traces of peanuts.

Re:0.6% regular stuff

[mph]

So only 0.6% of the universe is the "normal" matter and energy that we observe and of which we are composed?

I don't know about you, but I'm mostly made of baryons.

More information

[Anonymous Coward]

More information can be found at (including a cosmology tutorial):

http://www.astro.ucla.edu/~wright/cosmolog.htm#New s

This press release was mentioned in a post in the previous slashdot story yesterday.

Other links

[riptalon]

Mass media coverage can be found at CNN and the BBC. A list of all the MAP papers can be found here.

In this universe...

[MrByte420]

You only get 73% of you daily dose of dark matter. That would leave eating bowl after bowl after bowl. Try my new "Extra Dark Total Universe" and get 100% of your Dark Matter in just one bowl!

Isn't this

[Timesprout]

4.4% baryons, 22% dark matter and 73% dark energy.

The recipe for coke ?

Re:0.6% regular stuff

[DeepBlueDiver]

So only 0.6% of the universe is the "normal" matter and energy that we observe and of which we are composed?

The 4.4% baryons are the "normal" matter.

Sounds Familiar

[The_Rippa]

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!

Dark Energy/Dark Matter/Negative Energy

[monk]

Confused by "Dark Energy," "Vacuum Energy," "Dark Matter," and "Exotic Matter?" Here's a great collection of papers. (Mostly from the SNAP project)

Cheap Science vs. Expensive Pork

[Tackhead]

From the launch press release

"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.)

Re:0.6% regular stuff

[mph]

Remaining 0.6% probably antimatter but not 100% sure. Correct me if I'm wrong...

You're wrong. Antimatter is baryonic (well, at least to the same extent that normal matter is; some of it is leptons, but very little by mass).

I suspect that all of the percentages given have been rounded to two significant figures, and that you folks shouldn't be concluding that 0.4% has been unspecified.

There are contributions to Omega from electrons and neutrinos, for example, but this is a tiny amount compared even to the 4.4% from baryons.

Re: What's the remaining 0.6%

[Black Parrot]

> Subject says it all.

Apparently the universe is 0.6% rounding error.

Yeah, and their satellite is better too...

[TWX_the_Linux_Zealot]

"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!

So...

[CrazyDuke]

I would interpret this to mean the following:
(no profit recycling please)

1. 4.4 of the energy is stored in atomic nucleuses and some exotic particles.
2. 22% is stored in matter we can't directly observe, but can observe its effects on surrounding objects.
3. 0.6% is electrons and other small mass particles, measurable energy, etc.

Guess: Up to 73% of the original mechanical energy of the big bang is still in the form of mechanical energy (kenetic energy + potential energy).
Guess#2: Or 73% of the original ME of the big bang has been lost to entropy.

Aside Question: Given 2 objects of the same mass and potential energy at rest. Raise one of the objects to a higher potential. Does that not raise its mass relative to the first since the mass is its total energy/c^2? I remember NASA was puzzled by the Voyager probes not making it as far out as they expected them to be by now. Perhaps because they gained mass relative to us? Also, if 2 objects accelarate relative to each other and thier KE increases (relitively), does that not increase the mass, and their for the attraction between the two objects?

Bah, time to RTFA.

Re:Expansion rate?

[riptalon]

Mpc = Mega parsecs, i.e. millions of parsecs, where parsec stands for parallax arcsecond and equals about 3.26 light years.

Re:How pompous

[peculiarmethod]

Where do you get your information that the earth is "a mere speck in a speck of a galaxy in a far corner of the universe" from? Your analogy which seems to want to destroy any logic in using current models as a description for existance, however, it too relies on the very same information. What is to say that we aren't in a cave looking at a wall which is projected and changes the projections perspective as we try to "move". In which case, what leads you to believe anyone but yourself exists at all?

Sir, re-read the definition of science. It doesn't suppose itself to be an end all be all in the definition of the world. It is a method. So is palm reading.. and I have seen palm readers with a bucket load more logic than you show in your argument.

pm

Another question.

[CrazyDuke]

Would not a sphere of unimaginable size have a surface that would essentially flat?

For millenia, most of the world thought the earth was flat and people could fall off the edge. Could this just be an extension?

Re:Another question.

[Captain Nitpick]

Would not a sphere of unimaginable size have a surface that would essentially flat?

That's why the cosmologists have had such a hard time figuring out what the universe is shaped like. It's so flat and so big that it is very hard to tell.

However, a flat universe, and an unimaginably colossal (hyper-)spherical universe would cause slightly different phenomena to be observed. This new data has allowed the cosmologists to make their predictions with a better chance of being right.

Why is the probe at the L2 point?

[Ponderoid]

Can anyone tell me what's so special about the Sun-Earth L2 point that made it attractive to put the probe there? I couldn't find any reference on that site about why that spot was chosen.

At first I thought that it might need permanent shade from the sun, but I checked and found that the Earth's umbra doesn't extend that far out.

Unlike L4 or L5, the L2 position is a meta-stable point, requiring frequent correction to remain in place. There had to be a very good reason to choose it. The site has quite a bit of info about what exactly that spot is (nothing I didn't know already) and how the probe got there, but not a word why.

Re:Why is the probe at the L2 point?

[anubi]

Try Eddington's Site .

But, given this, let me add a little nota bene...

I found this by opening up a window to Google and typing the words +"L2" +"orbit" +"space". For me, it was the first entry returned.

"Give a man a fish and you have fed him for a day, but *teach* a man to fish and you have fed him forever". That is what makes sharing the 'tricks of the trade' so special.

Re:Why is the probe at the L2 point?

[djcinsb]

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!

Re:This "science" is FILTH

[theCat]

In Other News:

God, having recently been photographed in the microwave part of the spectrum, has held a press conference. Her spokesangel says "The Almighty resents this intrusion on Her privacy and just wishes some respite from the snapping of paparazzi hounding Her all day and night, never a moment's peace. She will now retire to a private part of the universe for some escape from the tabloids, thank you. But really, She is most upset about those faked pictures of Her wearing a beard. Have you no decency at all?"

God was last seen as a filmy blotch, one millionth of a degree warmer than the next blotch, in the general vicinity of the constellation Sagittarius. She was wearing a floral kimono and sandals from Gucci.

Answers here, dammit.

[Decimal]

Does Dark Energy suck or blow?

Blow... sort of. It acts the opposite of gravity, pushing everything apart.

http://www.lbl.gov/Science-Articles/Archive/dark-e nergy.html

Time is continuous, isn't it?

[MlBruehlly]

Since time has been proven to continue into infinity, why do we state that the universe 'started' 13.7 billion years ago? What was happening 13.8 billion years ago in the space we currently occupy? Surely the Big Bang was a result of some other cosmic event, since time could stretch infinitely into the past as well as the future. The universe couldn't have been born without being first conceived...

Re:Time is continuous, isn't it?

[ZigMonty]

Ah, no. According to current theory, asking what was happening before the big bang is like asking what is north of the north pole (Hawking quote IIRC). The big bang was the creation of time. How can anything exist before the big bang? The whole idea of "before the big bang" doesn't even make sense.

What arrogance! What outrageousness? Science?!

[Anonymous Coward]

This isn't science! Wait, oh shit, it is.

Let the naysayers be damned. I don't think there's a 'real' scientist out there who believes that this is the ultimate truth as to what the universe is composed of.

However, it's a good start at figuring out just what exactly is going on.

Where would we be now if some nutcase back in the day didn't say, "Hmm, well, what if the world was actually round?" and start working on craziness that would ensure.

Where would we be if some looney wouldn't have said, "You know, math would be a lot easier if zero exisisted."?

Giving random figures about things you aren't certain about isn't science. It's an important *part* of science. It's a launch vehicle for experimentation and theorizing.

Good agreement with COBE

[Dr. Mu]

When I first saw the COBE map awhile back, a little part of me said, "Well, that's nice, but such subtle data from a single platform isn't much to go on." But now, the new image certainly does seem to correlate well with it. The similarities are graphically obvious, and the fact that those data were obtained independently from COBE's is what makes this announcement most significant.

Re:Expansion rate?

[Gruturo]

What does the Mpc stand for?

Megaparsec (a parsec is 3.26 light years, or 3.08*10^16 meters).

Basically, it means that an object 1 megaparsec away from you is moving away by 71km/second (since the whole universe is expanding like a 4-dimensional balloon, all points are moving away from all other points, and this speed increases with their relative distances)

Nothing of the sort

[rufusdufus]

Time has not been proven to continue into infinity. Go read 'A Brief History of Time' for a good laymens introduction to cosmology.

Space and time are concepts deeply intertwined with energy and matter; they is not distinct from them. Thus, there is no 'before' the universe began, there is no time there, there is no there there either.

Re:How pompous

[Dirtside]

Who modded this clown up? Nobody claimed that we now understand "the entire universe." MAP is simply providing some data about fundamental characteristics of the universe. Its accuracy is arguable, but we're just getting some data here. Calm down before you blow out your last synapse.

Re:This "science" is FILTH

[Dirtside]

The Lord struck the shuttle down and burned it's occupants and they are still burning

Then it's odd that he only struck down 2 out of over a hundred shuttle flights. The Lord must have really bad aim! :)

Re:How pompous

[Captain Nitpick]

To think that the entire universe could be understood by standing atop a hill and looking at it!

Understood? Perhaps not fully, but one has to start looking somewhere. Why shouldn't we start looking from where we are now?

Umm....

[Anonymous Coward]

Do you have any idea about how NASA really operates?

NASA's budget and operations are firmly divided into unmanned and manned areas. Almost none of the unmanned science missions are launched by the Shuttle fleet... most are launched on corporate expendable launch vehicles.

Science in NASA is almost totally disengaged from launch vehicle & station planning & operations. This is a problem, not a cure.

No, but excellent question

[efuseekay]

No, unless your coffee has been artificially cooled below the temperature of the universe.

No naturally occuring cups of coffee in the universe will need any cooling from the CMB :).

Re:Universe Flat? Please explain...

[Bruce Losis]

Flatness/curvedness refers to whether parallel lines meet and by extension what sum of angles there are in a polygon:

In a flat space (or plane as an example of a 2D space) angles in a triangle sum to 180 degree, always. Parallel lines never meet. This is a falt desk in 2D.

In positively curved space (or plane) internal angles of a triangle sum to >= 180 degrees (sum approaches 180 as size of triangle side lengths approach 0). Parallel lines cross twice. This is the surface of a globe.

In negatively curved space (or plane) internal angles of a triangle sum to <= 180 degrees (again sum approaches 180 as size approaches 0). Parallel lines diverge. This is a saddle.

It's easy to see the way this are if you think of the space as a 2D object since the curvature requires (to visualise) an extra dimension, but the principles are the same in higher dimensionalities

Re:Expansion rate?

[efuseekay]

The further away the object is from us, the greater the velocity it seems to be expanding away from us. So H=71km/s /Mpc means that for every Mpc the objet is away from us, it is flying away from us at the velocity of 71 km/s.

Re:Universe Flat? Please explain...

[murky.waters]

A way to visualize what flat (and open & closed) mean is to think of a plot of how two dimensions are shaped at very large distances. That is, if you had some ordinary (flat, straight lines are straight lines) reference and observed the path of a bunch of photons sent of at right angles (only two directions) to form a grid and plot that in 3D. Then if there is no curvature (=flat), you'll get a plot that looks like a sheet of paper or the surface of a desk. If the universe was curved (open or closed) then you'll get a hyperpolic saddle or sphere respectively.

In short, flat means space like we ordinary envision it; it has absolutely nothing to do with the whole universe only expanding in 2 dimensions (like flat earth vs. round) as some of the earlier posters seem to think.

Mathematically, flat is the most unlikely result since even the slightest deviation would translate into one of the other two states. Physically, it means that the universe's geometry is euclidean, that its volume is infinite, and that it expands FOREVER (yes sure, the expansion rate approaches zero, but you know how asymptotes are supposed to work).

Incidentally, it means that we won't be able to eat at Milliway's. Shit.

Astronomy Picture of the Day

[msheppard]

The map (really big version too) is today's Astronomy Picture of the Day. Along with another good description of the findings with the typical excellent APOD links.

Go Apod!
M@

Just don't get your hopes up yet, children

[Pac]

Those 4% of normality are on the other side of the Universe, to the left and a bit bellow the oldest quasars. We are deep into the utter nonsense zone. But if you are smart you would have guessed that by now.

Re:speed of light constant?

[Mr. Slippery]

If the speed of light is constant, then why does it vary as it goes through different things? For example: when light goes through glass, it slows through the glass then speeds back up again.

You're correct. What's constant for all observers is the speed of light in a vacuum.

Executive summary

[jfmiller]

I'd just like to mention that I really appriceate it when the author of an article on science sums it if for us. I often have only 5 min to brouse the headlines and information like this is most welcome.

JFMILLER

Dark Energy Sucks.

[Ardias]

Dark Energy Sucks because it exerts a negative pressure on the universe. (There's a neat article about positive and negative pressure in the most recent Scientific American - including stuff about dark energy and the cosmos.)

Anything with a negative pressure sucks.
Anything with a positive pressure blows.