Universe Articles

Tag Archive for: universe

infinite universe

Spatial Curvature in Cosmological Models

/
0 Comments
Standard cosmological models are classified by spatial curvature into three broad types: open, flat, and closed universes. These correspond to negative,…
Evidence for Big Bang

Evidence for the Big Bang: CMB, Hubble’s Law, FAQ Guide

/
1 Comment
Big Bang: Key PointsHubble's law (redshift of galaxies) and the Doppler effect provide direct evidence that the universe is expanding away from our…
Cosmic Web Connections

Cosmic Web Connectivity: Galaxy Evolution and Quenching

/
1 Comment
The universe was not perfectly uniform at the beginning; some regions had higher density than others. Over time these higher-density regions attracted…
bb_infinity2

Intro to the Big Bang and Infinity Concepts

/
34 Comments
In the cosmology section of the Physics Forums, I encountered many Big Bang and related infinity problems. Hence, in this article, I want to explain the…
journeycosmos3

Learn About the FLRW Metric and The Friedmann Equation

/
1 Comment
Previous Chapter: A Journey Into the Cosmos – The Friedmann Equation                Chapter 2- FLRW Metric and The Friedmann Equation In…
expandinguniverse

Explore Coordinate Dependent Statements in an Expanding Universe

/
5 Comments
In this Insight, we will discuss the general Robertson-Walker (RW) universe, in which a set of co-moving observers with proper time ##t## observe the universe…
cosmosintro

Learn About the Friedmann Equation and the Cosmos

/
6 Comments
This is an introduction to cosmology for someone who has some knowledge of calculus and basic physics. In this tutorial, we will take a journey into the…
inflation5

A Poor Man’s CMB Primer: Quantum Seeds

/
11 Comments
 The CMB establishes a record of ancient acoustic oscillations in the baryon-photon plasma. We've been studying how these primordial sound…
universestart

Did the Big Bang Have a Center? Explaining Cosmology

/
28 Comments
Did the Big Bang Have a Center? What the standard models say According to standard cosmological models based on general relativity — and which agree…
universeexpand

Big Bang, Inflation & Dark Energy — FLRW Cosmology

/
29 Comments
Big Bang and expansion (no inflation, no dark energy) Einstein's General Relativity allows a solution (the FLRW metric) in which an effectively empty…
lightcone7_3

LightCone 8 Tutorial Part III – How Things are Computed

/
1 Comment
In Part I and Part II of this mini-series, we have briefly discussed the basic user interface and the use of charts to depict the LCDM cosmological model.…
lightcone72

LightCone8 Tutorial Part II – Charts

/
4 Comments
Part I dealt with the basic user interface of LightCone8. This part of the tutorial is about potentially useful cosmological insights to be gained from…
earlyuniverse

Was the Early Universe in a Disordered State?

No. The second law of thermodynamics says that entropy can only increase, so if the early universe had been in a state of maximum entropy, then the cosmos…
observableuniverse

Why the Observable Universe Radius Exceeds Its Age

The radius of the observable universe is about 46 billion light-years, which is considerably greater than its age of about 14 billion years. The radius…
steadystate

What Is the Steady-state Model and Why It’s No Longer Viable

Introduction to the Steady State Model Back in 2011, I wrote a FAQ entry for Physics Forums on the steady state model and why it is no longer viable.…
blackholesuniverse

Why the Early Big Bang Universe Didn’t Form a Black Hole

/
7 Comments
Why the Big Bang Is Not a Black Hole In the early universe, the matter was gathered together at very high density — so why wasn't it a black hole? Big…
universespinning

Is the Universe Rotating? Evidence, Tests & Limits

/
3 Comments
Can we tell whether the universe is rotating? If you believe wholeheartedly in Mach's principle, there is no way to test empirically for the rotation…
birthcmb

A Poor Man’s CMB Primer: The Birth of a Cosmic Background Radiation

/
3 Comments
 The early universe was hot. So hot that nuclei boiled. The great thermal energy of the universe overwhelmed the confining efforts of the…
balloonanalogy

Balloon Analogy Explained: Cosmology, Expansion & Limits

/
63 Comments
The Balloon Analogy is a straightforward way to illustrate — without being complete — two important points of modern cosmology that many people find…
cmb

A Poor Man’s CMB Primer: Orientation of the Universe

/
4 Comments
 This is a picture of the cosmic microwave background:Fig 1. The cosmic microwave background as seen by the European Space Agency's…
CosmologicalHorizons

Inflationary Misconceptions and the Basics of Cosmological Horizons

/
46 Comments
Introduction It is a common saying that during inflation "space expanded faster than the speed of light."  This statement is meant to articulate the…