An internet poster recently floated the idea that friction with a recently denser interstellar medium causes global warming. Despite its superficially ridiculous nature, refuting this proposition is an interesting quantitative exercise.

We study the variation of the apparent weight of an object with height above the surface of a planet with a (buoyant) atmosphere. Interestingly, this variation depends on two competing factors--the reduced gravitational acceleration (which acts to reduce the weight with increasing height) and the reduced buoyancy force in the progressively less…

The tidal forces generated by a black hole can be so powerful that they cause unlimited stretching, known as spaghettification. A detailed analysis of this phenomenon requires the use of Einstein's theory of general relativity. The aim of this paper is to offer an up-to-date and accessible analysis of spaghettification, in which the complex…

Data from the Kepler satellite were analysed using the Mikulski Archive for Space Telescopes database. With the participation of 53 students, we determined the parameters of the HAT-P-7b (Kepler-2) exoplanet system (transit duration, planet-to-star radius ratio, orbital period, semi-major axis and star mass). We used approaches that are easy to…

The Promoting Radio Astronomy in Ghana through School visits and Astronomy Clubs (PRAGSAC) project was an intervention to promote astronomy education in schools in Ghana. It was initiated by a group of enthusiastic students who were trained in radio astronomy and astrophysics under a Royal Society/Newton Fund UK project termed Development in…

This paper has a didactic aim. Indeed, starting from the well-known principle of free fall discovered by Galileo Galilei, we want to make some reflections that we consider useful for secondary school students. Being the acceleration invariant with respect to Galilei's transformations, it is useful to underline that the free fall in a gravitational…

Astronomy is one of the few sciences where the data (star-light) can be seen by all. Yet, there is a disconnect between a typical undergraduate lecture and, for example, where a planet may be in the sky and how to observe it. With the advent of moderate cost, high-quality 'back-garden' astronomy, and standard computers powerful enough to produce…

The planet Mercury transited the face of the Sun in a rare spectacle on 11 November 2019. It was an awe-inspiring moment for 300 students from Kwabenya Community High School and Ghana Atomic Energy Commission Basic School in Ghana to see this wonder of the cosmos. Celestron Power Seeker 60 mm diameter telescopes were used to project the Sun's…

Given the great interest that black holes arouse among non-specialists, it is important to analyse misconceptions related to them. According to the author, the most common misconceptions are that: (1) black holes are formed from stellar collapse; (2) they are very massive; (3) they are very dense; (4) their gravity absorbs everything; and (5) they…

Advancements in mobile technologies have accelerated mobile Augmented Reality (AR), and many applications have been developed and presented in online stores. This study aims to evaluate the accuracy of the AR model of the Solar System simulated in mobile AR applications located in the Google Play Store. The applications were examined in the store…

Throughout the long history of astronomy, scientists have repeatedly written fictional stories, which often lend themselves to use in the classroom thanks to the authors' in-depth knowledge and an appealing storyline. This article uses the novel 'The Black Cloud', written by the well-known astronomer Fred Hoyle, to show which physical-astronomical…

In this study, the tilt of the Earth's axis was measured during a lunar eclipse using a telescope based on the angle between the lunar orbit and ecliptic planes being considered as approximately zero. The presented method not only offers a practical and reliable way of measuring the axial tilt of the Earth during a lunar eclipse but also helps in…

We propose an experimental analogy to verify Kepler's second law using a spherical pendulum. We made a movie of a closed elliptical orbit of the pendulum and extracted the data position using the Tracker software. Analyzing the data, we measured the areas that the position vector sweeps showing the validity of Kepler's second law.

In recent years, general relativity (GR) and gravitational-wave astronomy have emerged both as active fields of research and as popular topics in physics classrooms. Teachers can choose from an increasing number of modern instructional models to introduce students to relativistic ideas. However, the true potential of an instructional model can…

A practical experiment is described to estimate the distance to a star using simple equipment, suitable for secondary or undergraduate students. The brightness of the star is visually matched to a miniature filament lamp, and its distance inferred from the inverse square law. Students gain an appreciation of astronomical units and practice in…