Is the Big Bang in the Bible?

[Buster's Uncle]

The one who writes about the people, not the machines.

[Buster's Uncle]

NASA's Dark Energy Hunt Combines Powerful New Tools and 2 Missions
SPACE.com
by Nola Taylor Redd, SPACE.com Contributor  6 hours ago



An artist's rendition of the proposed WFIRST-AFTA mission, which will study dark energy, extrasolar planets and objects in the near-infrared.



Dark energy makes up nearly three-fourths of the universe, driving its accelerating expansion, but the substance is still mysterious to scientists that study it.

In upcoming years, NASA has plans to investigate this powerful force with the new WFIRST-AFTA mission and a strong role in the European Space Agency's Euclid mission.

"NASA has plans for a robust dark energy portfolio over the next decade," Jason Rhodes of the NASA Jet Propulsion Laboratory said during a news conference at the April meeting of the American Physics Society in Savannah, Georgia.


'A tripod of science'

NASA's proposed Wide-Field Infrared Survey Telescope-Astrophysics Focused Telescope Assets, or WFIRST-AFTA, will use five probes to perform three complimentary surveys in its search to clarify the nature of dark energy.

"WFIRST-AFTA is a survey mission to make the most precise measurements on the influence of dark energy and dark matter on the universe," Neil Gehrels, WFIRST project scientist of NASA's Goddard Space Flight Center, told Space.com by email.

Type Ia supernovas are thought to form from the explosion of a white dwarf star. Because these powerful detonations all share similar brightness that can be viewed in distant galaxies, they are regarded as "standard candles" of cosmology. Recording how dim a supernova appears provides an indication of their distance.



An artist's view shows three different potential methods of forming Type 1a supernovae, the 'standard candles' used to measure the expansion of the universe. The first two panels show a white dwarf in a binary system accumulating matter


WFIRST-AFTA will survey nearly 3,000 Type Ia supernovas to determine how rapidly they are moving away from the Milky Way due to the expansion of the universe. Scientists think dark energy drives this expansion.

"We can trace out how the universe is expanding more rapidly in the current epoch than earlier in the history of the universe and use that to constrain models of dark energy," Gehrels said.

The telescope will also perform a High Latitude Imaging Survey to determine the effects of dark matter structures on the light from distant galaxies. Einstein predicted — and scientists have subsequently confirmed—that massive structures bend the light coming from objects behind them, serving as a gravitational lens. Astronomers have used such natural telescopes formed by features such as massive galaxies to study objects throughout the universe.

Dark matter works the same way, bending the light from galaxies that sit behind it. By searching for small distortions of galactic shapes, WFIRST-AFTA will allow scientists to determine the dark matter distribution along the lines of sight.

The third dark energy survey planned for WFIRST-AFTA will study baryonic acoustic oscillations, or BAOs. Ripples of sound waves left over from the early universe grew into the larger structures of the universe over time. Accurately measuring the position and distance of a hundred million galaxies will map these disturbances to determine the evolution of dark energy over time.

The three complimentary surveys combine to provide a broad portrait of dark energy.



An artist's concept of the ESA's Euclid misssion to study dark energy.


"The combined power of all these probes will give the best understanding of dark energy in the current universe and how it evolved with time as the universe expanded," Gehrels said. "WFIRST-AFTA is the only observatory, space or ground based, that combines all of these probes."

Proposed to launch in the mid-2020s, WFIRST-AFTA is not searching solely for information about dark energy. Instead, it combines what Gehrels calls "a tripod of science." The telescope will also image planets outside the solar system and perform near-infrared surveys.


Euclid

In addition to its own mission, NASA will participate in the European Space Agency's Euclid mission. Last year, NASA nominated 40 American scientists to join the 14 American scientists already part of the international Euclid Consortium, the team responsible for the science, data production and instruments for the mission. NASA will also provide 16 infrared detectors for the telescope.

Euclid's goal is to understand the nature of dark energy and its role in the expansion of the universe. To do so, it plans to use two complimentary probes to study the phenomenon. The first probe will study weak gravitational lensing, while the second will examine BAOs.

Orbiting at the second Lagrangian point, Euclid will use two instruments to study a wide region of the sky free from the contaminating light from the solar system and the galaxy. It will also observe two "Euclid Deep Fields" of the early universe.

Of the approximately 10 billion sources Euclid intends to observe, more than 1 billion will be studied for weak lensing, while tens of millions of galaxies will be measured for clustering caused by BAOs.

"WFIRST-AFTA and Euclid will make complimentary observations, with WFIRST-AFTA observing fainter galaxies and Euclid observing more sky," Gehrels said.

"The combined data set will be much larger and more accurate than any other BAO measurement."

When combined with ground-based observations over a variety of wavelengths, the new observations that WFIRST-AFTA and Euclid will obtain should provide significant insights into dark energy and the expansion of the universe.

"The best constraints on dark energy in the 2020s will come from a combination of Euclid, WFIRST and ground-based data," Rhodes said.

http://news.yahoo.com/nasas-dark-energy-hunt-combines-powerful-tools-2-110751699.html

---

Siiigh.

[Lorizael]

You shouldn't have any problem with this. The best way to show dark energy isn't real (if you happen to believe that) is to test its predictions against reality.

[Buster's Uncle]

I have a problem with people being stupid, is all - it's not one of my better personality traits.  Bugs me that so much has been hung on a ludicrous fudge factor.

But you're right of course.  Kill all the dark crap dead so we can move onto some real science.

[Rusty Edge]

Well, I can say that it's not energy because you can't light anything with it, and a believer will insist that I merely proved it's dark.

Or maybe they'll say it's like dark humor, and that the very act of study and analysis will destroy it.

[Lorizael]

Dark energy is a bad name and probably goes a long way toward explaining people's resistance to the concept.

I contend that dark energy is not the new aether, however, because it doesn't fall prey to the usual errors we tend to see in historical scientific mistakes. Most of the errors that led to people believing strongly in the wrong thing were the result of assumptions about how the universe must be.

For example, with the aether, physicists were certain that light must travel through a medium, even though there was no reason beyond analogy to believe this was the case. When vitalism ruled the day, biologists believed that life must have some essence to it that separated it from non-life. There are countless examples of theories relying on assumptions about how the universe must be.

This is not the case with dark energy. Dark energy is real if general relativity holds. Yet general relativity is universally understood to be a provisional theory. It is wrong, because it is incompatible with quantum mechanics (which is also wrong, for the same reason). So there aren't scientists who believe general relativity must be true. Rather, scientists think that we should give general relativity the benefit of the doubt for now because it is an enormously accurate and precise theory that has been confirmed over and over again for the last century. If you accept the provisional validity of general relativity, accepting dark energy follows naturally.

[Buster's Uncle]

No, if I accept GR, dark energy is a possible explanation for observed anomalies, absent a better one, which is what I'm waiting for.   -Also, you're right that the name is a bad one.

[Rusty Edge]

Let's rename it. I'm assuming "Invisible" isn't a great alternative, either.


String energy?

[Buster's Uncle]

Something to do with spatial expansion - if I understand right, it's nothing to do with energy anyway.

[Lorizael]

It does have something to do with energy. In fact, energy-wise, dark energy comprises the majority of the universe. This is a big part of why dark energy is thought to exist. All observations to date show that we are currently in the epoch of dark energy, just as we were once in an epoch of matter and before that of radiation.

The hang-up here is that thinking of energy as something that turns the lights on--or does work of some kind--is kind of a limited view. Since general relativity, energy is also what causes the curvature (or, more generally, distortion) of space (which eventually leads to doing work on stuff). So because cosmologists have tremendous observational evidence that space is being perturbed in a particular way, they can say with a great deal of confidence that there is some amount of energy causing this disturbance.

[Buster's Uncle]

You do realize how circular the logic of the first two sentences reads?

[Lorizael]

It may seem circular, but not if you read the second paragraph. The point is that, if you accept GR and you accept modern astronomical observations, there is some amount of space-curving energy that exists in the universe. It was the initial observation of the accelerating expansion of the universe that showed this energy exists, but subsequent observations of a wide variety of different phenomena confirmed the amount of energy that is out there which cannot be accounted for by matter and radiation.

[Rusty Edge]

More than heat, light, electricity and magnetism?

Is gravity energy, too?

[Lorizael]

Electricity, magnetism, and gravity are not energy, no; they're forces. Forces, by definition, are changes in momentum. And when you change the momentum of something, you move energy around. That's where heat and light come from.

But I'm not sure what you're asking with your first question.

[Buster's Uncle]

It may seem circular, but not if you read the second paragraph. The point is that, if you accept GR and you accept modern astronomical observations, there is some amount of space-curving energy that exists in the universe. It was the initial observation of the accelerating expansion of the universe that showed this energy exists, but subsequent observations of a wide variety of different phenomena confirmed the amount of energy that is out there which cannot be accounted for by matter and radiation.

You're telling me popular conclusions I'm already familiar with, not why this explanation works where no other does, or even why I should trust that the observations in question out to be considered complete enough.