Universe Articles

Tag Archive for: universe

infinite universe

Is the Universe Finite, or Is It Infinite?

/
0 Comments
Standard cosmological models come in three flavors, open, flat, and closed,[Carroll] whose spatial curvatures are negative, zero, and positive. The open…
Evidence for Big Bang

Is there Evidence for the Big Bang?

/
0 Comments
Big Bang Key PointsHubble's law (redshift of galaxies) and the Doppler effect provide direct evidence for the universe expanding away from our reference…
Cosmic Web Connections

The Evolution of the Universe, Cosmic Web and Connections

/
1 Comment
The universe was not perfectly uniform when it started, some areas had a higher density than others. During the evolution of the universe, these areas…
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

/
4 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

Where Did the Big Bang Happen?

/
28 Comments
According to standard cosmological models, which are based on general relativity and are found to agree well with observations, time and space did not…
universeexpand

Learn about the Big Bang and the Expansion of the Universe

/
29 Comments
The "ordinary Big Bang and expansion" (no inflation, no dark energy) Einstein's General Relativity allows a solution (FLRW metric) where an empty Universe…
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

/
3 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

Radius of the Observable Universe in Light-years Is Greater than 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

Is the Universe a Black Hole?

/
7 Comments
In the early universe, the matter was gathered together at very high density, so why wasn't it a black hole?The first thing to understand is that the…
universespinning

Can We Tell Whether the Universe Is Rotating?

/
3 Comments
If you believe wholeheartedly in Mach's principle, then there is no way to test empirically for the rotation of the universe as a whole, since there is…
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

Learn Inflation Balloon Analogy Misconceptions

/
62 Comments
The Balloon Analogy is a simple-minded way to help describe (but not completely describe) two facts of cosmology that are difficult for many people to…
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

/
45 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…