These are some of my cosmology posts
-
June 21 2021 – the solstice
This year, the June solstice will fall on 21 June. In the northern hemisphere, it is the day when there is the most daylight and when the Sun is at its highest in the midday sky. The origin of the word solstice is from two Latin words: sol, which means Sun, and sistere, to stand still. On the…
-
Satellite Navigation
Satellite navigation systems have come to affect countless aspects of our daily lives, from directing our holiday aeroplanes to enabling us to drive round an unfamiliar city without any map other than the one on our mobile phone. Most new cars sold today have an inbuilt Sat Nav and you can buy trackers relatively cheaply…
-
The Observable Universe and Its Horizons
Updated 1 February 2026 Although the Universe may be infinite in extent, in the generally accepted Big Bang cosmology we are only able to see a small fraction of it. We call this small fraction we can see the observable universe. Outside the boundary of the observable universe lies the unobservable universe – a region…
-
Easter April 4 2021
This year, for the majority of the world’s Christians, 4 April is Easter Sunday, one of the most important dates in the calendar. Although because of the current restrictions due to the Covid pandemic, celebrations will be a little limited in many places. Although Easter is the festival celebrating the resurrection of Jesus Christ from the dead,…
-
Distances in Cosmology
This post has now been superseded by a more detailed post Measuring Distances in Cosmology ———————————————————————————————- I recently read an article on the popular astronomy website site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…
-
Advancing the Clocks
On the early hours of Sunday 14 March 2021, most of the United States will put their clocks forward an hour and Daylight Saving Time (DST) will commence. Two weeks later on 28 March most countries in Europe (including the UK) will follow, switching to summer time. In this post I’ll talk about the practice…
-
Solar Sails
Update 21 September 2025 As this is a changing area, I have replaced this post from 2021 with a revised and updated one. This is available at https://explainingscience.org/2025/09/21/solar-sails-fuel-free-space-travel/ I have also created a video which goes into solar sails in much more detail
-
Human spaceflight in 2021
2021 will be an interesting year for human space flight. Not only is it the sixtieth anniversary of Yuri Gagarin’s historic first manned spaceflight, but it will be the first time that a privately operated spacecraft will arrive at the International Space Station (ISS). This private spacecraft is not just a one-off but will be…
-
Chinese Moon samples
Like many of my readers I was pleased to see that the Chang’e 5 spacecraft returned to Earth on 16 December 2020 with around 2 kg of lunar rocks. This great achievement was the first lunar sample return mission for China and is indeed the first time any rocks have been brought from the Moon…
-
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…
Explaining Science 