Planetary conjunction

The sky was magnificent on Tuesday, maybe the best ever. Venus was west of the Moon and then Jupiter and Mars were on a clear arc through.

The conjunction has also included Saturn, Uranus and Neptune but just the three planets together was spectacular and too vast for my camera. All are on the same side of the Sun as us at the same time. I need to think some more about how to work out the next time it will happen from first principles.

Angel of the North wind protection

The Angel of the North must have a large wind load and the largest area for catching the wind is higher up, giving a big torque that could pull it over. According to this, the ribs direct wind flow downwards to push on the foundations. This would produce an opposite torque to keep it from falling.

Percussion installation

I tested out the hollow metal of this installation at Durham Botanical Gardens after accidentally knocking it and getting an impressive sound.

Knocking it in different places gave different notes. The highest note from the narrowest section.

This was a bit deeper.

This was a very low note. Since they are all part of the same space, it can't be the air that is vibrating. Maybe stationary waves are forming across the metal. Wider metal would be bigger wavelength and thus deeper note.

Low clouds in climate models

These low clouds over Longsleddale are the opposite in climate models to the high clouds. They are thicker and the cloud tops reflect more solar radiation back out into space. However, global warming models suggest that a warmer earth will push clouds higher on average which will then increase the warming. See January 2025 Physics World for the details.

High clouds in climate models

There's a lovely article in the January 2025 edition of Physics World explaining the differing effects of clouds in climate models. High clouds are cooler being higher up in the atmosphere and absorb more of the outgoing radiation from the Earth's surface, reradiating a lot of it back down in the classic greenhouse warming effect that makes our planet habitable. These high clouds - like the alto-cumulus in the picture of Skeggles Water - are thinner so they also let more sunlight through which is another warming effect.

Venus

Venus has been very prominent in the early evening these last couple of months. It was the subject of a feature in the last series by Brian Cox on the Solar System. I was interested in the apparent "snow line" effect on the mountains of Venus. It's a kind of metallic frost. It has to be something that melts and evaporates at 460 Celsius at the lowest levels on Venus but solidifies at cooler temperatures with altitude. Brian Cox names lead sulfide as a possible candidate. Looking that up, I see a melting point of over 1000 Celsius. This must be at Earth's standard atmospheric pressure and will be different on Venus. This article names bismuth sulfide and tellurium as other possible candidates.

Retrograde motion

Mars has been in retrograde motion recently as Earth has been overtaking it. Earth has a higher angular velocity. Mars is still going forward but looks like it is going backwards relative to a fixed reference point. OK, there are no fixed reference points in space but the background of stars are so far away that it doesn't make much difference. Here Mrs B was overtaking a lorry coming up to a bridge. Above, the cab lines up with a bridge in the distance. 

In the second view there is daylight between the cab and the bridge and below the cab is nowhere near lining up with the bridge. You could achieve the same effect if we were still and the lorry went backwards. But all the while it was moving forward at 50mph. This is what we mean by retrograde motion.