Dark Energy: Theory and Observations - Essay Example

It is equivalent to vacuum energy in reality since it is the energy density of an unfilled vacuum. The general relativity theory denotes that energy will affect gravity (Wang 76). A cosmological constant is characterized by negative pressure that is equivalent to its energy density. As such, it causes acceleration in the expansion of the universe.

Quintessence refers to the hypothetical form of energy that can be attractive or repulsive. It is a scalar field that has its equation defined by the ratio of pressure to its density. Attraction or repulsion of this energy is dependent on the kinetic to the potential-energy ratio (Morrey Bsc & Morrey 112). Quintessence serves to solve part of the problems accruing from the cosmological constants. Unlike the cosmological constant, quintessence is a dynamic equation that varies with time. In addition, it differs from the cosmological constants in the fact that it forecasts a slower increase in the rate of expansion of the universe.

The third alternative idea stems from the string theory. String theory stipulates that an atom’s elementary particles are dimensional swinging lines (Amendola and Tsujikawa 64). It is a quantum theory of gravity. The theory comprises configurations that define all observed basic forces and matter but have zero cosmological constants. The methods employed to determine the above ideas are the geometry of space, exploding stars, and the late-time integrated Sachs- Wolfe effect (Amendola and Fujikawa 340).

Exploding stars are ideally supernovae. Type la supernovae offer a standard candle for the measurement of the distance to galaxies that are much far away. It combines the information with redshift; a measure of the speed at which a galaxy recedes. Conclusively, astronomers have inference that there is a factor that is contributing to the increased velocity of the recession of galaxies. The geometry of space is ideally observations made that the space is flat. As such, astronomers imply a sum of energy density, which corresponds to the dark energy hypothesis.

The late-time integrated Sachs- Wolfe effect provides that an increased rate of cosmic expansion influences gravitational potential wells, as well as hills to become flat in the course of photons' passage. Resultantly, cold and hot spots are generated on the CMB associated with massive superclusters and voids (Morrey Bsc and Morrey 135). The ISW is thus a direct indicator of dark energy in a universe that is essentially flat. Hence, each of the above techniques presumes that dark energy is existent from the different gravitational fields that they cause.