Estimating the size of a nucleus using electrostatic repulsion can be traced back to the invention of an ultra-sensitive apparatus, which measured forces in terms of the twisting of a fine wire, dating from the 18th Century. This device, known as a torsion balance, is often attributed to the French engineer and physicist Charles Augustin … Continue reading Coulomb’s Law and Nuclear Radii
Required Practicals, Part 1: Planning
This is the first instalment in a short series looking at the qualities that characterise a high-quality report for an A-level Physics required practical. First up is planning, which has to be conducted in advance to ensure that the most appropriate apparatus and methods are used. Proper planning documentation must identify the variables and the … Continue reading Required Practicals, Part 1: Planning
Solar Eclipse, 12th August 2026
Next Wednesday, 12th August 2026, a full solar eclipse will be visible from Iceland and Greenland in the north, together with Spain and the very north-eastern tip of Portugal in the south. In Jersey, the eclipse will cover more than 90 percent of the Sun’s surface at around 7:15pm. Weather permitting, it should be quite … Continue reading Solar Eclipse, 12th August 2026
Hubble Tension Part 2: Baryon Acoustic Oscillations
There is an introduction to the nature of the “Hubble tension” in the first part of this article, which covers measurements based on the distance ladder (see https://physbang.com/2026/07/28/hubble-tension-part-1-the-distance-ladder/). This article looks at how the Cosmic Microwave Background (CMB) can be used to calculate the expansion of the Universe – and therefore the Hubble constant. But … Continue reading Hubble Tension Part 2: Baryon Acoustic Oscillations
Hubble Tension Part 1: The Distance Ladder
The term “Hubble tension” refers to discrepancies in the value of the Hubble constant, which in turn indicates the rate of expansion of the Universe. In particular, the “tension” arises because two different techniques for calculating the constant give significantly different values. For a brief introduction to the Hubble constant, see https://physbang.com/2026/04/26/red-shift-and-the-age-of-the-universe/ or NASA’s summary … Continue reading Hubble Tension Part 1: The Distance Ladder
Exponential changes
Imagine an empty tube train (metro, if you prefer) pulling into a crowded station. When the doors open, people surge forward and the carriage starts to fill very quickly. As the number of people in the carriage increases, the number of remaining spaces decreases and the rate at which further people can board also decreases. … Continue reading Exponential changes
How do electric cells generate a current?
We take for granted the fact that an electric cell (or battery) will cause a current to flow through an external circuit. The current is often discussed in terms of a flow of electrons (like water through a pipe) or energy transferred between adjacent electrons (like a row of dominoes falling onto each other). It … Continue reading How do electric cells generate a current?
Answers to some of physics’ biggest mysteries
Exam season is over so this seems like a good time to admit that physicists don’t know all the answers – and don’t even always agree on which of the available answers is best. The two biggest areas of disagreement are cosmology and quantum mechanics. For example; What do we mean by the “Big Bang”? … Continue reading Answers to some of physics’ biggest mysteries
Instrument resolution and experimental accuracy
Uncertainties in measurements arise from the equipment used and the method employed. As the final paper for this year’s A-level Physics examination is imminent, and tests knowledge of uncertainties, it is worth taking a moment to examine the causes of uncertainty in more detail. We will do this by thinking about two example measurements; one … Continue reading Instrument resolution and experimental accuracy
Know your calculator!
When answering examination questions, it is important that your excellent knowledge of physics isn’t undermined by your calculator behaving in an unexpected way. You MUST be able to trust the answer given. But the situation is potentially complicated, not only because calculators don’t all behave the same way but also because they may not even … Continue reading Know your calculator!
