Most physicists presume the universe began as a ?Big Bang? after which all matter and energy resided in an unimaginably hot ball of plasma. This ball expanded, and after about 4-hundred-thousand years cooled sufficiently to allow the photons to escape. These photons we now detect and call the ?cosmic microwave background? (CMB). No matter what part of the sky we look at, we see almost the same CMB brightness (intensity). This means that the universe appears to be flat. By flat, I mean that if one were to draw a very large triangle of cosmic proportions, the internal angles would add up to 180 degrees. If the universe were curved, the angles would not sum to 180, but to a greater or lesser number. Hubbell was one of the first to notice that the further a galaxy was away from us, the greater the spectrum of emitted light was shifted to a lower energy. This is due to the fact that a photon emitted from an object moving away at a great velocity is seen by us as having less energy, or a change in color. In other words a blue photon might be seen as being red. This phenomenon was termed ?red shift?. By analyzing the light from stars in distant galaxies, and comparing their spectrum with similar, nearby stars, we can determine their relative velocity; the speed they are moving away from us. This method fails when viewing the most distant galaxies, as it is not possible to view individual stars. Astronomers have turned to studying super novas with known properties to extract data indicating the expansion velocity of the universe.
The amazing result was, not only is the universe expanding, it is expanding at an accelerated rate. The properties of a curved universe could be used to indicate the expansion only seemed to accelerate. A flat universe implies the acceleration is real!
There is no known form of energy that can cause the acceleration, so ?Dark Energy ? is the term used to describe this unknown force. One of the properties of dark energy is that it must act in opposition to the gravitational force. Since matter and energy are interchangeable terms, the density of the universe could be called ?energy density?, useful since it?s more descriptive of the conditions of the primordial fireball. Briefly, the history of our universe might be:
The expansion of the early universe resulted in the same amount of energy distributed more or less equally throughout a greater volume of space. The energy density decrease means the universe was cooling and eventually matter was condensed from its constituents. As it continued to expand, local gravitational anomalies allowed the formation of gas clouds that eventually formed the early stars of the most distant galaxies. Continued expansion further decreased the energy density until about 4 billion years ago the energy density dropped below that of dark energy. The previous rate of expansion then changed to an accelerated rate. Some physicists believe this will eventually lead to the ?Big Rip?. The Big Rip may occur when the universe is about 20 billion years old. The stars will separate from the galaxies as their gravitational attraction is overwhelmed by dark energy. In the last 30 seconds, atoms will be torn apart with the process continuing until there is only dark energy.
The amazing result was, not only is the universe expanding, it is expanding at an accelerated rate. The properties of a curved universe could be used to indicate the expansion only seemed to accelerate. A flat universe implies the acceleration is real!
There is no known form of energy that can cause the acceleration, so ?Dark Energy ? is the term used to describe this unknown force. One of the properties of dark energy is that it must act in opposition to the gravitational force. Since matter and energy are interchangeable terms, the density of the universe could be called ?energy density?, useful since it?s more descriptive of the conditions of the primordial fireball. Briefly, the history of our universe might be:
The expansion of the early universe resulted in the same amount of energy distributed more or less equally throughout a greater volume of space. The energy density decrease means the universe was cooling and eventually matter was condensed from its constituents. As it continued to expand, local gravitational anomalies allowed the formation of gas clouds that eventually formed the early stars of the most distant galaxies. Continued expansion further decreased the energy density until about 4 billion years ago the energy density dropped below that of dark energy. The previous rate of expansion then changed to an accelerated rate. Some physicists believe this will eventually lead to the ?Big Rip?. The Big Rip may occur when the universe is about 20 billion years old. The stars will separate from the galaxies as their gravitational attraction is overwhelmed by dark energy. In the last 30 seconds, atoms will be torn apart with the process continuing until there is only dark energy.
Facebook
Twitter