Red-Shift and the Age of the Universe
Stars can be characterised by their absorption lines, which reveal their temperature and composition. There is more detail about this in two recent posts about the HR diagram and stellar classification. A similar approach can also be used to characterise entire galaxies but in this case the aim is to determine how quickly they are receding (moving away) from the…
Read moreThe formation, life and death of stars
All stars are born through the same basic mechanism but their evolution depends on their size. In particular, all stars go through a hydrogen-fuel stage but the time spent fusing hydrogen is determined by the star’s initial mass. The final fate of a star is also predicted by its mass; some stars will simply fade away whereas others depart in…
Read moreClassification of Stars
The obvious way to classify stars is by their appearance; how bright they are and their colour. In both cases, we are referring to properties judged using the human eye from the location of planet Earth. Sadly, our eyes are not a good judge of colour (equal amounts of red and green light are perceived as the colour yellow) and…
Read moreElectricity: models and theories
Physics can get complicated at times and when it does, we use models to simplify things. The models aren’t wrong: in fact they work remarkably well, but they aren’t complete. Electricity provides probably the best examples of this state of affairs. Models normally start at the level of “electrons as buckets carrying energy” and include the idea that electricity flows…
Read moreA-level guide to astronomical telescopes
The first section of the Astrophysics module for AQA A-level Physics is all about telescopes. This post is a brief summary of that section’s key learning points. Telescopes aren’t used simply to make astronomical objects “bigger” or to get a “closer” view. It is true that nearby objects, such as our moon and other bodies inside the Solar System, do…
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