Total Energy Of The Universe

What is the Universe Fabricated Of?

The cardinal questions that need to be answered by astrophysicists are: What is really out at that place? And of what is information technology all made? Without this agreement it is impossible to come to any firm conclusions near how the universe evolved.

Protons, Neutrons and Electrons: The Stuff of Life

You, this calculator, the air we exhale, and the afar stars are all made upwards of protons, neutrons and electrons. Protons and neutrons are bound together into nuclei and atoms are nuclei surrounded by a full complement of electrons. Hydrogen is composed of one proton and one electron. Helium is composed of two protons, ii neutrons and two electrons. Carbon is composed of vi protons, six neutrons and half-dozen electrons. Heavier elements, such every bit fe, pb and uranium, contain even larger numbers of protons, neutrons and electrons. Astronomers like to call all material made up of protons, neutrons and electrons "baryonic matter".

Until about thirty years ago, astronomers thought that the universe was composed almost entirely of this "baryonic matter", ordinary atoms. Still, in the by few decades, there has been ever more evidence accumulating that suggests there is something in the universe that we can not run into, possibly some new grade of thing.

WMAP and Dark Matter / Night energy

Pie Chart of the content of the Universe By making accurate measurements of the cosmic microwave background fluctuations, WMAP is able to measure the basic parameters of the Big Bang model including the density and limerick of the universe. WMAP measures the relative density of baryonic and non-baryonic affair to an accurateness of better than a few percent of the overall density. Information technology is as well able to determine some of the properties of the non-baryonic affair: the interactions of the non-baryonic matter with itself, its mass and its interactions with ordinary matter all bear upon the details of the catholic microwave background fluctuation spectrum.

WMAP determined that the universe is flat, from which information technology follows that the hateful energy density in the universe is equal to the critical density (inside a 0.5% margin of error). This is equivalent to a mass density of 9.nine 10 10^-30 g/cm³, which is equivalent to only v.9 protons per cubic meter. Of this full density, we now (as of Jan 2013) know the breakdown to be:

4.six% Atoms. More than 95% of the free energy density in the universe is in a form that has never been directly detected in the laboratory! The actual density of atoms is equivalent to roughly one proton per iv cubic meters.
24% Cold Night Matter. Dark thing is likely to be composed of one or more species of sub-atomic particles that interact very weakly with ordinary thing. Particle physicists have many plausible candidates for the nighttime matter, and new particle accelerator experiments are likely to bring new insight in the coming years.
71.4% Nighttime Energy. The first observational hints of night energy in the universe date back to the 1980'south when astronomers were trying to sympathise how clusters of galaxies were formed. Their attempts to explain the observed distribution of galaxies were improved if night energy were present, but the testify was highly uncertain. In the 1990's, observations of supernova were used to trace the expansion history of the universe (over relatively recent times) and the big surprise was that the expansion appeared to be speeding up, rather than slowing down! There was some concern that the supernova information were being misinterpreted, but the event has held up to this twenty-four hour period. In 2003, the first WMAP results came out indicating that the universe was flat (encounter above) and that the nighttime thing made up merely 24% of the density required to produce a flat universe. If 71.iv% of the free energy density in the universe is in the grade of nighttime energy, which has a gravitationally repulsive effect, it is merely the right amount to explain both the flatness of the universe and the observed accelerated expansion. Thus dark energy explains many cosmological observations at in one case.
Fast moving neutrinos practise not play a major role in the development of structure in the universe. They would have prevented the early clumping of gas in the universe, delaying the emergence of the first stars, in conflict with the WMAP data. Yet, with 5 years of data, WMAP is able to see evidence that a sea of cosmic neutrinos practice exist in numbers that are expected from other lines of reasoning. This is the start time that such evidence has come up from the cosmic microwave background.

Another Probe of Dark Affair

Past measuring the motions of stars and gas, astronomers tin "weigh" galaxies. In our own solar system, we can utilize the velocity of the World around the Sunday to measure the Sun's mass. The Earth moves around the Sun at 30 kilometers per second (roughly sixty yard miles per hour). If the Sun were four times more than massive, so the Earth would need to move around the Sun at threescore kilometers per second in order for it to stay on its orbit. The Dominicus moves around the Milky Way at 225 kilometers per 2nd. We can use this velocity (and the velocity of other stars) to measure the mass of our Galaxy. Similarly, radio and optical observations of gas and stars in distant galaxies enable astronomers to determine the distribution of mass in these systems.

The mass that astronomers infer for galaxies, including our ain, is roughly ten times larger than the mass that tin be associated with stars, gas and dust in a Galaxy. This mass discrepancy has been confirmed by observations of gravitational lensing, the bending of calorie-free predicted past Einstein's theory of general relativity.

HST Image of a gravitational lens

Text Link for an HST press release describing this prototype.

Past measuring how the groundwork galaxies are distorted past the foreground cluster, astronomers tin measure the mass in the cluster. The mass in the cluster is more 5 times larger than the inferred mass in visible stars, gas and grit.

Candidates for the Night Affair

What is the nature of the "dark matter", this mysterious material that exerts a gravitational pull, but does not emit nor absorb lite? Astronomers do not know.

There are a number of plausible speculations on the nature of the night matter:

Brown Dwarfs: if a star's mass is less than ane twentieth of our Sun, its core is not hot plenty to burn either hydrogen or deuterium, so it shines only past virtue of its gravitational contraction. These dim objects, intermediate between stars and planets, are not luminous plenty to be directly detectable by our telescopes. Brown Dwarfs and like objects take been nicknamed MACHOs (MAssive Compact Halo Objects) by astronomers. These MACHOs are potentially detectable past gravitational lensing experiments. If the dark matter is made by and large of MACHOs, then it is likely that baryonic thing does make up about of the mass of the universe.
Supermassive Black Holes: these are thought to power afar "K" type quasars. Some astronomers speculate that dark thing may be fabricated upward of copious numbers of black holes. These blackness holes are likewise potentially detectable through their lensing effects.
New forms of matter: particle physicists, scientists who work to empathise the fundamental forces of nature and the composition of matter, have speculated that there are new forces and new types of particles. 1 of the main motivations for building "supercolliders" is to try to produce this matter in the laboratory. Since the universe was very dense and hot in the early moments post-obit the Large Bang, the universe itself was a wonderful particle accelerator. Cosmologists speculate that the dark matter may be made of particles produced shortly after the Big Bang. These particles would be very different from ordinary "baryonic matter". Cosmologists telephone call these hypothetical particles WIMPs (for Weakly Interacting Massive Particles) or "non-baryonic matter".

Nighttime Energy: a Cosmological Constant?

Dark Energy makes up a large bulk ot the total content of the universe, but this was non ever known. Einstein first proposed the cosmological constant (non to exist confused with the Hubble Constant) ordinarily symbolized past the greek letter "lambda" (Λ), as a mathematical prepare to the theory of general relativity. In its simplest form, general relativity predicted that the universe must either expand or contract. Einstein thought the universe was static, so he added this new term to stop the expansion. Friedmann, a Russian mathematician, realized that this was an unstable fix, like balancing a pencil on its signal, and proposed an expanding universe model, now called the Large Blindside theory. When Hubble's study of nearby galaxies showed that the universe was in fact expanding, Einstein regretted modifying his elegant theory and viewed the cosmological constant term as his "greatest mistake".

Many cosmologists advocate reviving the cosmological constant term on theoretical grounds, equally a mode to explicate the charge per unit of expansion of the universe. Modernistic field theory associates this term with the energy density of the vacuum. For this energy density to be comparable to other forms of matter in the universe, it would require new physics theories. So the addition of a cosmological constant term has profound implications for particle physics and our understanding of the fundamental forces of nature.

The main allure of the cosmological constant term is that it significantly improves the understanding between theory and observation. The near spectacular case of this is the recent effort to measure how much the expansion of the universe has changed in the last few billion years. Generically, the gravitational pull exerted by the matter in the universe slows the expansion imparted by the Big Blindside. Very recently it has become practical for astronomers to observe very bright rare stars called supernova in an effort to measure how much the universal expansion has slowed over the last few billion years. Surprisingly, the results of these observations signal that the universal expansion is speeding up, or accelerating! While these results should exist considered preliminary, they raise the possibility that the universe contains a bizarre form of matter or free energy that is, in effect, gravitationally repulsive. The cosmological constant is an example of this type of energy. Much work remains to elucidate this mystery!

There are a number of other observations that are suggestive of the demand for a cosmological constant. For example, if the cosmological constant today comprises most of the energy density of the universe, then the extrapolated age of the universe is much larger than it would be without such a term, which helps avoid the dilemma that the extrapolated historic period of the universe is younger than some of the oldest stars we observe! A cosmological constant term added to the standard model Large Bang theory leads to a model that appears to be consistent with the observed big-scale distribution of galaxies and clusters, with WMAP's measurements of catholic microwave groundwork fluctuations, and with the observed backdrop of X-ray clusters.