June 14th 2026

Things from Today:

• Globular Clusters - Peter gave us an excellent overview of some of the properties and open questions in the study of Globular Clusters. These structures are collections of many many stars, much like a galaxy. One of the things that distinguishes them from galaxies like our own Milky Way, is their 'globular' morphology (their shape). Globular Clusters are spherical, rather than disk shaped. The stars that make them up are also far more closely packed than in our own galaxy.
  This has quite a striking consequence on the appearance of the night sky if you happened to live on a planet orbiting a star within a globular cluster. Peter explained that our own night sky has around 10,000 visible stars (across the entire celestial sphere, so realistically about 5000 at any one time). If you lived on a planet near to the middle of M13 (a particular Globular Cluster photographed below by Peter) you would see something like 100,000 visible stars, most with much greater individual brightness than those in our own night sky. This would be an astonishing sight to behold! I found references to an Article in a 2014 copy of Astronomy Magazine featuring simulations of what this might look like, however - it is sadly not available online. Some of the simulated images can be viewed here.
  The main mystery surrounding Globular Clusters, is the question of how they formed in the first place... 

• Quantum Mechanics: Particle VS Wave... - As we discussed in my Building a Universe from Scratch lecture on June 6th, one of the central oddities of quantum mechanics is the way it forces us to rethink our understanding of matter. At the subatomic scale, matter does not behave in the same way we observe matter on our own length scale to behave. Rather, subatomic matter exhibits properties that are analogous to the behaviour of waves: spreading out and interfering, only to be observed as particles when a measurement is made ("collapsing the wavefunction").
  In reality, these descriptions of 'particle' and 'wave' are approximations of something much deeper, and more complicated; the fundamentally quantum nature of matter - which can
  There is a great 1 minute reflection by Professor Ramamurti Shankar from Yale, before leading his students on their first steps in quantum mechanics. This is taken from part two of his excellent lecture course 'Fundamentals of Physics' (which is a serious course, for physics majors at one of the best physics departments in the US).
  For those interested, part 1, and part 2 of this year long lecture course are available for free on YouTube.

• Spinning Black Holes & Photon Orbits - We discussed one of the many interesting features of black holes, which is that they can capture light into orbit around them. These so called photon rings are very thin for stationary black holes, but elongate outwards for spinning black holes.
  There is a great talk (of quite a technical nature) by Alex Lupsasca I have linked in the extra watching / listening section. He also has an app (unfortunately, only available on IOS) which display light can bend right the way around a black hole's event horizon. I demonstrated a terrible selfie I took on Pier Hill using his Black Hole Vision app in my Black Holes: Monsters of the Cosmos lecture on June 20th.

Extra Reading:

• [Article] How Alex Lupsasca Learned to Trust AI for Real Physics - (OpenAI Academy)

• [Article] The Discovery of an Atmosphere on a Tiny Kuiper Belt World - E Siegel (Big Think)

Extra Watching / Listening:

• [Video] The Hardest Questions in Physics - Brian Greene & Leonard Susskind (World Science Festival)

• [Video] Black Hole Photon Rings and Gravitational Ringdown - Alex Lupsasca (Simons Foundation)
  [Note: This is a pretty technical talk!]

Homework

This 'homework' is recurring, and one I like to set my own students (and try to stick to myself!):

1. Learn something new everyday.

2. Share what you know with someone else.

3. Look at the world and "think like a Martian".

If you learn something interesting, I would love to hear about it! Tell me about it next time or drop me an email!

spacetime-sundays@science-on-sea.com