Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 26: Problem 18

Imagine an astronomer living in a galaxy a billion light-years away. Is the observable universe for that astronomer the same as for an astronomer on Earth? Why or why not?

Short Answer

Expert verified
No, the observable universe for an astronomer living a billion light-years away would not be the same as for an astronomer on Earth. This is because the observable universe for any observer is limited to the parts of the universe from which light has had time to reach them. Therefore, since the observer is a billion light-years away, their observable universe would be shifted by a billion light-years compared to ours.

Step by step solution

01

Understanding the concept of a light-year

A light-year is a unit of distance. It is the distance that light can travel in one year. Considering that light travels at a speed of approximately \(299,792\) kilometers per second, in one year, it can cover about \(9.46\) trillion kilometers.
02

Considering the observable universe

The observable universe is the part of the universe that we can technically observe from Earth. The observable universe is not the entire universe, but only the part of it from which light has had time to reach us. As we know, the universe is about \(13.8\) billion years old, so light from objects further away than about \(13.8\) billion light-years has not had time to reach us yet, limiting the extent of our observations.
03

Applying the concept to the astronomer a billion light-years away

If the astronomer is a billion light years away from Earth, then their observable universe would not be identical to ours. This is because the farthest objects they would be able to see would be different from the farthest objects an astronomer on Earth could see. They would also be able to see certain objects that for an Earth astronomer might be beyond the observable universe. Therefore, their observable universe would be shifted by a billion light-years compared to ours.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Estimate the age of the universe for a Hubble constant of (a) \(50 \mathrm{~km} / \mathrm{s} / \mathrm{Mpc}\), (b) \(75 \mathrm{~km} / \mathrm{s} / \mathrm{Mpc}\), and (c) \(100 \mathrm{~km} / \mathrm{s} / \mathrm{Mpc}\). On the basis of your answers, explain how the ages of globular clusters could be used to place a limit on the maximum value of the Hubble constant.

The host galaxy of the supernova HST04Sas (see the image that opens this chapter) has a redshift \(z=1.390\). The light from this galaxy includes the Lyman-alpha \(\left(\mathrm{L}_{\alpha}\right)\) spectral line of hydrogen, with an unshifted wavelength of \(121.6 \mathrm{~nm}\). Calculate the wavelength at which we detect the Lyman-alpha photons from this galaxy. In what part of the electromagnetic spectrum does this wavelength lie?

Describe how astronomers use the cosmic background radiation to determine the geometry of the universe.

Why did Isaac Newton conclude that the universe was static? Was he correct?

Describe how the expansion of the universe explains Hubble's law.
See all solutions

Recommended explanations on Physics Textbooks

Rotational Dynamics

Read Explanation

Engineering Physics

Read Explanation

Geometrical and Physical Optics

Read Explanation

Further Mechanics and Thermal Physics

Read Explanation

Kinematics Physics

Read Explanation

Physical Quantities And Units

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free