Question

can anyone help me with this :
Explain to your teacher how the Doppler shift and Cosmic Background Radiation are used to understand the history of the development of earth.lp me with this ?

Answer 1

Edwin Hubble, a 1920s astrnmr, frst discovrd evidnce of an expndng univrse wen he noted dat all visible galaxies apear to b movng away frm each othr. Based on a proprty of light called the red shift, he noticed that the farther away a galaxy was, the faster it was receding. This relatnship, known as Hubble's Law, has been repeatedly verified (Dalrymple 2004:189). In 1927, Georges Lemaitre, a Belgian astronomer, noted that this observation is most easily explained if the Universe started at a definable time in the past with a violent expansion of matter and energy that was originally highly compressed and intensely hot (Dalrymple 2004:189). Thus, the idea of the Big Bang was born.

The most important confirmation of the Big Bang came from a discovery in 1965 by Arno Penzias and Robert Wilson, two engineers working for Bell Laboratories. They discovered radiation from space, called "the cosmic microwave background," that permeates the Universe. This background radiation has all the characteristics it was predicted to have if the Universe started with the Big Bang and has since been expanding (Dalrymple 2004:15).

As previously stated, both the expansion of the universe and the background radiation can be used as clocks to date the age of the universe. In the expansion of the Universe, Hubble's law relates velocity to distance, and distance divided by velocity equals time. Scientists can measure the velocity of distant objects as they move either toward or away from Earth using the Doppler Effect (Dalrymple 2004:189). This clock assumes that the Universe expands uniformly or by known changes in velocity, and that the distance to other galaxies has been accurately estimated (Dalrymple 2004:191-93). As any source of light moves toward or away from an observer, there is a velocity-dependent shift in both the wavelength and the frequency of the light. For objects moving away, the wavelength is lengthened and the frequency is decreased (Dalrymple 2004:189). Because wavelength defines color, a receding source of light has its spectral lines shifted toward the red end of the spectrum.redshift Using this red shift, the velocities at which galaxies are receding from the Milky Way and from each other can be measured, and the time required for the matter of the Universe to have expanded from a point of infinite density can be calculated. The most recent calculations, which take into account the non-uniform expansion caused by the mass of the Universe and by vacuum energy, give ages for the Universe in the range of 13-15 billion years (Dalrymple 2004:211).

The second clock, cosmic background radiation, involves the analysis of the warmer and cooler spots in the cosmic microwave background. This microwave radiation is thought to have originated in the Big Bang, and it is a measure of the average temperature of the Universe, which has been cooling as the Universe has expanded. To elaborate on this, sound waves in the forming Universe left their imprint on the microwave radiation in the form of slightly warmer and cooler spots, which correspond to regions where the radiation is being compressed and expanded (Dalrymple 2004:194). The size of these spots is uniform throughout the Universe. The older the Universe is, the farther apart these spots should be and the smaller they should appear. An analysis of these warmer and cooler spots of background radiation gives an age for the Universe of 14 plus or minus 0.5 billion years (Dalrymple 2004:194).

Although some aspects are still in the process of being understood, a basic overview of the early history of the Universe is as follows. At the very beginning, according to the Big Bang theory, the temperature and density of the Universe were infinite, and it was filled with tremendous energy. The Big Bang initiated expansion. This consisted of a decrease in density accompanied by cooling, both of which are continuing to this day. Within the first 10 seconds or so after the Big Bang, the principal subatomic particles were formed. About 300,000 years later the temperature decreased to 10,000 K and the first simple atoms formed. The subsequent history of the Universe involved continued cooling, continued expansion and a decrease in average density, and the condensation of dust and gas into galaxies, stars, and planets.

Heads up this is a copy and paste. So I would take this and re-do it some so that not to get in trouble.