Da li je Seljak u pravu ili nije?

70% kosmosa je misterija koja mi nazivamo tamnom energijom. Kao poredjenje setite se da je 70% povrsine zemlje prekriveno sa vodom. Zamislite da mi uopste ne znamo sta je voda! To je situacija koju mi imamo sa tamnom energijom.


The key is that, as we look at supernovae far away, we are seeing them as they were long ago. The fact that they were moving away from us more slowly than expected showed that the expansion of the universe, instead of slowing due to gravity, was actually accelerating. No known component of the Universe could have caused this acceleration. Suggestions for unknown components have included a new kind of fluid, called "quintessence," an unexpected property of the vacuum of empty space, or a fundamental modification of Einstein's theory of gravity.


http://science.nasa.gov/missions/jdem/

Teško da neko može reći da li je u pravu ili ne, sve je još uvek u domenu teorije

Da. Interesantne su alternativne teorije, kojih se ni Seljak ne odrice. Pratim tu utakmicu vec duze vreme, i sve je zanimljivija xD.


Pogotovo od kad je NASA odustala od JDEM-a, i prihvatila WFIRST. ;P

Ko se plasi mraka? Alternative tamnoj energiji


Last week, we asked whether astronomers could be wrong about dark matter, the invisible stuff that seems to help hold galaxies together. Is it possible that dark matter doesn’t really exist?

This week, we’ll investigate whether there are viable alternatives to the idea of dark energy, the mysterious stuff that astrophysicists believe is pushing our universe apart.

In every direction we look, galaxies are hurtling away from us. That isn’t surprising in itself—after all, the Big Bang sent space and everything in it flying apart. One would expect that the gravitational pull of all the “stuff” in the cosmos would gradually slow down this expansion, bringing it to a dead stop or even collapsing everything back together in a "Big Crunch." Yet instead, astronomers see that the galaxies in our universe are rushing apart faster and faster.

What could be causing this acceleration? Physicists call it dark energy, and it could make up more than 70 percent of the cosmos. But so much remains unknown about dark energy that some scientists are asking whether it exists at all.

What if, instead of a mysterious unseen energy, "there is something wrong with gravity?" asks Sean Carroll, a theoretical physicist at the California Institute of Technology.


http://www.pbs.org/wgbh/nova/p...k-alternatives-to-dark-energy/



Instead of relying on mystery particles, a small community of researchers suggests an intriguing alternative: What if the answer lies in changing what we know about the laws of gravity? The leading alternative to dark matter is known as Modified Newtonian Dynamics (MOND). The assumption is that at large scales, the laws of gravity are different from Einstein's theory of general relativity. "MOND merely tweaks the way a known force, gravity, works—we don't have to accept that the universe is filled with invisible mass," McGaugh said.


http://www.pbs.org/wgbh/nova/p...k-alternatives-to-dark-matter/

Alternative izgledaju još manje verovatne

Pa da. Vracamo Njutnovu dinamiku xD. Bice interesantno ovih dena. Cekam jedan "research paper" ;P.

Evo ti nesto interesantno od Sean Carrolla-a, koji je rekao: " Da mozda nesto nije u redu sa gravitacijom? " : D

Tu ima i spisak nekih od teorija kandidata.

Plasticno i slikovito je objasnjeno, i za ostale koji bi voleli da znaju o cemu se tu radi. : )

Dark Energy, or Worse:
Was Einstein Wrong?
Sean Carroll
Caltech


http://preposterousuniverse.com/talks/nsf07.pdf





_{[Ovu poruku je menjao boxxterr dana 27.12.2012. u 10:31 GMT+1]}

Čuvena je rečenica iz Šerloka Holmsa: “Data! Data! Data!” he cried impatiently. “I can’t make bricks without clay.” Mislim da isto važi i ovde, bez novih misija i novih/boljih teleskopa verovatno će se i dalje tapkati u mestu

Pa jeste, ali to vise nije prioritet. JDEM je povucen, i kolko god oni govorili da je to samo preimenovani WFIRST, prioritet su sad egzoplanete. Pitanje je zasto je to tako. Herlok Šolms bi bio koristan sada da otkrije o čemu se tu radi. ;P

Msm, sta traze na tim "exo-planetama"? Zasto je to sad prioritet? Da nece mozda da nas sele odavde? Ili sta vec. Nesto nam ne govore!


This data shows that of all the exoplanets which have been discovered, 0.5% have the potential to be habitable. Similarly, 1.8% of the planet candidates may be habitable.

Apart from the scenario of an advanced extraterrestrial civilization that is emitting immensely powerful signals intending to reach other intelligent life in the galaxy, the detection of life at interstellar distances is a tremendously challenging technical task that may not be feasible for many years, even if such life is commonplace.

http://en.wikipedia.org/wiki/Extrasolar_planet


Various estimates have been made as to how many planets might support simple or even intelligent life. For example, Dr. Alan Boss of the Carnegie Institution of Science estimates there may be a "hundred billion" terrestrial planets in our Milky Way Galaxy, many with simple life forms. He further believes there could be thousands of civilizations in our galaxy. Recent work by Duncan Forgan of Edinburgh University has also tried to estimate the number of intelligent civilizations in our galaxy. The research suggested there could be thousands of them.



The discovery of over 500 exoplanets in systems that are mostly quite different from our own planetary system is inspiring observers and theoreticians to understand how these exoplanets were formed, how they evolve, and ultimately whether there are any Earth-like planets on which we might someday search for signs of life.

http://wfirst.gsfc.nasa.gov/about/


The objective of the WFIRST dark energy survey is to determine the nature of dark energy in the Universe. Does the nature of the dark energy change with time? Does it require a modification to Einstein's laws of gravity (the General Theory of Relativity)?

Nije mi jasno zasto nije ubacio i teoriju hijerarhije zakona medju teorije kandidate. Mozda nije imao vremena ili tako nesto. Verovatno ce kasnije ispraviti to.

Ne sećam se da je neko izjavio da je to prioritet, osim ako nemaš neki uvid u ukupni budžet i koliko tačno % je otišlo na te projekte

Ovako je to izgledalo:

JDEM

The NASA and DOE Dark Energy Mission

Dark energy was discovered in 1998 by Department of Energy- and NASA-funded scientists working at the Lawrence Berkeley National Laboratory and other institutions. It was named by Science magazine that year as the scientific breakthrough of the year. Dark energy is the name given to the cause of the accelerating expansion of our Universe and comprises more than 70% of the total mass and energy of the Universe. Yet, what it is and how it behaves is a complete scientific mystery.

http://jdem.lbl.gov/

A sad izgleda ovako:

WFIRST

» Sky Surveys

large area near infrared surveys

Infrared maps unlock the secrets of star- and planet-formation.
» Exoplanets - Microlensing

photometry
(large area imaging survey)

Microlensing
» Dark Energy

large area spectroscopy and imaging surveys, supernova monitoring

Dark energy is speeding up the expansion of the Universe, but its nature is a mystery.
» Guest Investigator Program

observing time competitively selected GI programs


http://wfirst.gsfc.nasa.gov/


The Joint Dark Energy Mission (JDEM) was an Einstein probe that planned to focus on investigating dark energy. JDEM was a partnership between NASA and the U.S. Department of Energy.

In August 2010, the Board on Physics and Astronomy of the National Science Foundation recommended WFIRST mission, a renamed JDEM-Omega proposal which has superseded SNAP, Destiny, and ADEPT, as the highest priority for development in the decade around 2020.

Nesto nam ne govore! Traze planetu na kojoj ima zivota!