List and explain three ways to estimate the age of the universe since the Big Bang.?

Answer 1

All these estimates assume that the laws of physics have stayed the same since very early in the universe's history.

Note that ANY theory, not just the big bang, must be able to explain the results of these estimates:

1. Measure the background radiation. Currently it is the microwave region. Thermodynamics will predict how long it has taken for the universe to cool to a temperature consistent with this background.

2. measure the rate of expansion of the universe via the Hubble effect (redshifts basically) and extrapolate backwards.

3. measure the relative abundances of the radioactive nuclei and knowing their halflives and making assumptions about how much of it was left over from the original material of the universe, estimate how long these nuclei have been around for.

Here's some more for consideration.
* Study the overall distribution of matter in the universe and try to model how it came to be distributed the way that we observe it. The time needed to reach the observed distribution gives us an estimate of the time sing it all began.

* Look for the oldest stars and estimate their age. Obviously the oldest stars cannot be older than the universe.

The big bang theory is in good agreement with all these methods, that is why it is the most generally accepted theory.

Answer 2

There are many different methods that astronomers have used to estimate the age of the universe. I will explain three different ones.

First, astronomers can estimate the age of the universe by looking at white dwarfs’ cooling times. When a white dwarf begins to cool down, it is because it has just stopped having any “nuclear reactions” (3). Instead they slowly get rid of it by “electromagnetic radiation” (3). The reason that this method helps to estimate the age of the universe is because astronomers are “measuring the temperature and luminosity of any white dwarf (that is to say, its position on an H-R diagram)” and because of this we are able to determine how old it is “since it formed from the death of its parent star” (3). The uncertainties of this method are that not all white dwarfs have come from being a regular large star. Sometime there are “cooler, fainter white dwarfs” that have “formed from much shorter-lived main-sequence stars, and have spent almost their entire lifetime in their current degenerate state” (3). The estimated age of the universe from this method is about “12.8 +/- 1.1 Gyr” (3).

A second way that astronomers can estimate the age of the universe is because of radiometric dating. Due to the discovery of different isotopes we are able to determine the ages of different elements. Though sometime an isotope will “ ‘decay’ into isotopes of other elements” because the isotope is considered unstable (2). This decay is the only reason that radiometric dating has been made possible, because the decay occurs at the rate of a half-life. A half-life is the process over time that half of it turns into another element. One thing that can kind of be an uncertainty when it comes to this method, is that in order for radiometric dating to be understood, it “requires that one understand the initial ratio of the two elements in a given sample by some means” (2). Another uncertainty is that finding a substantial amount of rocks on Earth is that they usually all have been affected by erosion. In order to find out how old the universe is, most astronomers use meteorites because they usually “have the same radiometric age” (2). The age of the universe in this method is determined because of these meteorites, and so the universe, from this method, is thought to be about 4,560,000,000 years old (4.6 billion).

Finally, the last method that can help determine the estimated age of the universe is the Big Bang Theory. The Big Bang Theory, as defined by Bennett, et al., is “the scientific theory of the universe’s earliest moments” (473). We can use this theory to estimate the age of the universe because it has different eras that make up the early universe. These eras are the Planck, GUT, Electroweak, Particle, Nucleosynthesis, Nuclei, Atoms, and Galaxies. Due to all of these eras, astronomers are able to figure out approximately how long each one is and what happened in each one of them. In the text, Bennett, et al. mentions that “many of the key events that shaped today’s universe occurred within the first few minutes after the Big Bang” (474). Since the research of the Big Bang Theory, the age of the universe it determined to be about 14 billion years old. Though there are some uncertainties with this method. Since we cannot go beyond where space and time began, due to it being in the past, there are some limitations in exactly what the age of the universe is.