August 16th 2026

Things from Today:

• Low Background Steel - A question was asked about steel being removed from pre-war ship wrecks. I didn't realise at the time that this was a question about Low Background Steel!
  Since the detonation of the first atomic bomb in 1945 (but mostly, since the peak of nuclear weapons testing in the 1960s) - the concentration of radioisotopes in the Earths atmosphere has increased. Our atmosphere has always contained some radioactive material, such as naturally occurring radon gas that comes from the Earth itself, and Carbon-14 produced by cosmic rays in the upper atmosphere.
  From what I can gather, the main culprits are Cobalt-60 and extra Carbon-14, created as byproducts of the detonation of nuclear weapons. Carbon-14 has a half life of about 5700 years (so, remains radioactive for a very long time indeed), whereas Cobalt-60 has a half life of a little over 5 years (meaning, after a few decades; it has almost all decayed).
  Part of the process of making steel involved blowing huge amounts of air over molten pig iron (iron that is rich in carbon impurities). So, if there are radioactive impurities in the air, those impurities will contaminate the steel as well.
  It's worth stressing here... that post-1945 steel is completely harmless (well... unless it is in the form of a sharp knife!...). It is far less radioactive than the natural radiation sources in the air we breathe (the radon and carbon-14 I mentioned before).
  Low Background Steel is so important to detector physicists, as some of the particle events their detectors are searching for are exceptionally rare. Meaning, even a tiny probability of a false positive, caused by the decay of a contaminant in the detector, could threaten the accuracy of the whole project! Here I am particularly thinking of experiments designed to detect neutrinos. Neutrinos are uncharged (electrically neutral) nearly massless particles, that stream through the Earth in huge numbers; very rarely undergoing any kind interaction (to put this in perspective, there are around 65 billion neutrinos passing through every 1cm by 1cm area on the Earths surface every single second). As their interactions are so rare, their detection is very susceptible to being scuppered by radioactive contaminants in the steel their detectors are made from.

• Pictures of the Solar Eclipse - We were very fortunate to be joined by local astrophotographer-extraordinaire, Dawid Glawdzin. Dawid shared many stunning pictures with us, including a compilation of pictures of the recent solar eclipse, as seen from Southend seafront. Dawid has kindly allowed me to show the photo below. To see more of Dawid's work, I highly recommend visiting his Instagram: @dawidgphotography.

• Anthropogenic Climate Change -  A question was asked about humanity's impact on the Earth's climate, and the evidence behind the scientific consensus that our planets climate is changing.
  The evidence is (unfortunately...) extremely compelling. The Earth is getting warmer, and this warming can only be explained by the increased concentrations of greenhouse gases in the Earth atmosphere, following the start of the industrial revolution.
  "How do we know there are more greenhouse gases in the atmosphere today?" - We know this by comparing the air today, with air trapped in ice cores under the surface of Greenland and Antarctica.
  "How do we know that greenhouse gases increase Earth's temperature?" - 'Greenhouse' gas is a generic term for gases that absorb infrared radiation of the same wavelength that is emitted by the Earth (all warm things emit infrared radiation). These gases absorb the infrared radiation coming from the Earths surface, trapping it, and therefore becoming warmer themselves, and bouncing these infrared waves back to the Earth surface (this is the 'greenhouse effect'). The greenhouse effect is not in itself a bad thing... without any greenhouse gases, the Earth would be too cold to support life - but a little greenhouse effect goes a long way. As humans have increased the concentration of greenhouse gases (such as carbon dioxide, methane, and even water vapour) in the Earth's atmosphere; we have amplified this warming effect.
  "Could this warming be due to other phenomena, like changes in the suns output?"  - The output energy from the sun certainly does have an impact on our climate; but fluctuations in the suns output are nowhere near large enough to account for the changes in temperature we have seen over recent decades. The headline figure in this NASA article shows that, actually, energy output from the sun has decreased over the last 35 years or so, while temperatures have skyrocketed.
  "Could it all be a massive hoax, designed to change our behaviour, and get us to buy electric cars?" - I suppose so... But you have to ask yourself who really benefits from this! Companies that drill, refine, and sell oil already hold enormous sway in the hallways of power around the world. If anybody was going to try and co-opt bad science for financial or political gain, the fossil fuel industry would be top of my list of suspects!...

• Proper Motion of Stars - A question was asked about the apparent motion of stars in the night sky (or rather, their apparent lack of motion!). Peter reminded us that this is something we discussed back in May, when he brought in two pictures of Wolf-359 (a faint red dwarf star in the constellation Leo) taken 17 years apart. I wrote a little bit about what Peter told us here, and included the photos he provided (one taken from his back garden in Southend!). You can also watch this 'short' I posted to YouTube some months ago, with my own musings on the history of the discovery of the 'proper motion' of the stars.

• Sunspots - Prompted by Dawid's spectacular images of the sun, we spoke a little about sunspots; what they are, and how they form (roughly). Rather than repeat this in writing, I am going to be a little bit lazy, and link a physics livestream I gave nearly six years ago, here. Only the first 12 minutes is about sun spots, and the rest gets a little technical!
  
  

Extra Reading:

• [Article] Astronomers spot Betelgeuse’s hidden companion - (Science Daily)

• [Article] In Hilbert Space, All Things Are Quantumly Possible - Charlie Wood (Quanta Magazine)

Extra Watching / Listening:

• [Video] Why are Slugs? Broadly speaking. - (Broadly Speaking)

• [Video] It’s A Bug’s Life, We’re Just Living In It - Jessica Ware (StarTalk)

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