Entries by Jorrie

LightCone7Combo Tutorial Part II – Charts

Part I dealt with the basic user interface of LightCone7Combo. This part of the tutorial is about potentially useful cosmological insights to be gained from LightCone7 charts. As a first example, we will find the answer to a common question: when did cosmic expansion changed over from decelerating to accelerating? We could have jumped into…

LightCone7Combo Tutorial Part I

LightCone 7 Combo is a versatile tabulating/charting cosmological calculator, useful for understanding the expansion history of the universe (and even some future expansion), based upon the Lambda-Cold-Dark-Matter (LCDM) model. Part I of this mini-series gives a broad overview of the user interface and the main functions. Follow-on parts will highlight some specific uses and techniques….

Approximate LCDM Expansion in Simplified Math (Part 4)

  Part 4: Cosmic Recession Rates An astronomer, accompanied by his amateur relativist friend, aimed a telescope at a distant galaxy and measured its redshift. It came out at exactly z=2. The astronomer thought for a moment and then said: “The recession rate of this galaxy exceeds the speed of light by about 20%”. His…

The LCDM Cosmological Model in Simplified Math (Part 3)

  Part 3: Important Cosmological Horizons and Distances A question that often comes up is: “how big is the observable universe?” The question can have more than one answer, depending on the context, so cosmologists have given it a technical name and a precise definition. It is called the ‘particle horizon’, here indicated by Dpar,…

Approximate LCDM Expansion in Simplified Math

  If we restrict ourselves to a spatially flat LCDM universe model, the first Friedmann equation can be written in a very simple form. Marcus started several PF threads in a collaborative effort to develop this simplified approach.[1] It is still a work in process, but here I summarize the main insights so far, the…