5: Moving Through Time
- Page ID
- 30477
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Chapter 5 explores how objects in the Universe change over time. It examines how the ages of objects can be determined: first through radiometric dating and next through the lifetimes of stars. The evolution of stars, from their formation to their eventual “death,” is discussed. The evolution of the Universe as a whole, from its beginning through today, concludes the chapter.
- 5.0: Moving Through Time Introduction
- Stars and galaxies are born, evolve and die, but with lifetimes that are so long, we can only study snapshots that (in almost all cases) seem unchanging. In this chapter, we examine several techniques for determining the ages and lifetimes of stars and then see how the Universe and its constituents evolve through cosmic time.
- 5.1: Measuring the Ages of Objects - Radiometric Dating
- There are a variety of independent methods for measuring ages of different objects in the Universe, and these ages provide additional data to incorporate into our models of the Universe. Hopefully, this will give you an understanding of how we know the ages of various objects, so that they do not feel like random facts imposed from authority.
- 5.2: Measuring Ages - Lifetimes of Stars
- Advances in the understanding of radioactivity at the beginning of the 20th century enabled scientists to calculate the age of Earth accurately. However, the ages derived presented a problem to astronomers: they were not consistent with estimates of the age of the Sun.
- 5.3: Change Over Time - Evolution of Stars
- We would like to know if our Galaxy, the Milky Way, has changed or will be changing. And what about changes in the Universe itself? It turns out that we can learn a lot about how the Sun and the Milky Way have evolved and continue to evolve by comparing them to observations of other stars and galaxies. Similarly, we can learn about the Universe’s evolution through our observations of the objects—stars and galaxies—within it.
- 5.4: Evolution of Galaxies and the Universe Itself
- We previously introduced the idea of the light-minute, the light-hour, and the light-year as distance measurements. This method works because the speed of light is constant. We can use the constancy of the speed of light to measure distances this way for any time period we like. However, the constancy of light speed means that light is not only a useful tool for measuring distances; light can also be used as a sort of time machine.
- 5.5: Wrapping It Up 5 - Cosmic Timeline
- Have you ever wondered about the events that created the Universe we live in? Do you want to know when stars first appeared or when galaxies formed? Do you know how old the Universe is? Or when our Solar System formed? Perhaps you have wondered when humankind arrived on the scene.
Thumbnail: Artist's impression of a Type Ia supernova, as revealed by spectro-polarimetry observations (CC BY 4.0; ESO via Wikipedia)