Cosmic Horizons

Although the Universe may be infinite in extent, in the generally accepted Big Bang cosmology we can only see a small fraction of it. This is known as the observable universe. Field of distant galaxies - Image Credit NASA  There are three widely used definitions of cosmological horizons, which are limits imposed by cosmology to… Continue reading Cosmic Horizons

Distances in Cosmology

I recently read an article on the popular astronomy website site Universe Today.   It stated that ‘…the CMB [cosmic microwave background radiation]  is visible at a distance of 13.8 billion light years in all directions from Earth, leading scientists to determine that this is the true age of the Universe. ' This statement isn't… Continue reading Distances in Cosmology

Dark energy an unexpected finding

I offered recently to write an article for my local astronomy society on the discovery of dark energy.  It is  an expanded version of the blog post I wrote  on the topic last year and, at over 3000 words, it is longer  than my usual posts. I thought it would be of interest to many… Continue reading Dark energy an unexpected finding

Surveying the Cosmos – Part II

In a previous post  I talked about the Large Synoptic Survey Telescope (LSST), a large telescope being built in Chile which will spend 90% of its time surveying most of the sky a total of  1000 times over a 10 year period (in the remaining 10% it will revisit areas of specific interest).  In this… Continue reading Surveying the Cosmos – Part II

The discovery of dark energy

The is a now an expanded and updated version of this post available at: https://explainingscience.org/2020/12/10/dark-energy-an-unexpected-finding/   The Expansion of the Universe Astronomers have known since the late 1920’s that the Universe is expanding. By this we mean that distances between objects which are not bound together by another force, such as gravity, increase over time.… Continue reading The discovery of dark energy