Surface area in the cactus house

This is the Cactus House on the Threave Estate. Notice the extra fins on the heating pipes. I think that the mode of heating is actually by conduction from the metal to the air molecules. This extra energy makes the molecules move further apart, becoming less dense. The less dense air floats up spreading thermal energy by convection. It helps for the pipes to be given an extra large surface area because the thermal energy leaves through the surface. The more surface there is touching the air, the more air can be heated at one go. The cacti employ a different approach. They would lose water through their leaves by evaporation. So the leaves are rolled up into spines to give them a much smaller surface area. Less water vapour is able to escape so they don't dry up. The leaves can't do photosynthesis because they have such a tiny surface area. Hence the stem has to be full of chlorophyll and green so that it can do the photosynthesis.

Olbers' Paradox

 The rain has finally stopped and the sky is clearing. I've just been outside and taken the above photograph of the stars shown on my planisphere below. So why is the sky so black?

Olbers was an 18th Century German astronomer who first hit on the idea that if the Universe was infinitely big and had existed for an infinite length of time, the sky at night should be white. That's because there would by logic be a star in every direction, given even distribution through space. In the infinite time available, light from every direction would have time to reach us. He concluded that the Universe was therefore finite. I had always taken that to mean that it had a limited size, but the stuff I read now seems to suggest that the Universe is infinite in size. But it is finite in TIME. So they now talk about the OBSERVABLE UNIVERSE, the bit from which light has had time to reach us.

Einstein again!

The quotation on the bench probably sums up this blog. I've had a lot of fun so far looking at things and trying to comprehend the Physics. I like the way the seat has been made to look like a wave. Einstein was famous for showing that the speed of light waves in a vacuum is the same no matter who is looking at them.

The spring constant of my knitting

 The blue square is my first completed project with help from Mrs B. Note the change in direction along the diagonal. This helps it to hold its shape better. I used a Newtonmeter to investigate.

 Here's my original knitting with no direction change. It took 3N to stretch it by 9cm. That's 0.33 Newtons per cm which is its spring constant.

Pulling the other way was 1N to stretch 9cm. That's 0.11 Newtons per cm. The spring constant used to be called the stiffness of the material when I studied Engineering. Stiffer materials are harder to stretch. So the knitting is 3 times harder to pull across the rows than along the rows. By having a clever square with rows in perpendicular directions, that difference will be removed and the knitting is equally strong in both directions.

The Butterfly Effect

I photographed this Red Admiral butterfly in our garden during the warm weather a month ago. It reminded of the famous idea that launched chaos theory on the world. In 1963, Edward Lorentz came up with some equations for atmospheric conduction. When plotted in phase space, they resembles the wings of a butterfly. https://en.wikipedia.org/wiki/Lorenz_system His work showed that the weather obeys non-linear relationships - in other words, doubling one thing doesn't often double the other. The response can be quite out of proportion. A small change can produce a big effect. They started saying that if a butterfly flaps its wings in Rio, it can cause a hurricane in the US. Small change in pressure, disproportionate effect. This study of non-linear Physics became known as Chaos Theory.

Subtractive colour mixing: an experiment with watercolours

I've always wanted to be a painter so I succumbed to an impulse purchase of cheap watercolors over the summer. A spot of Youtube tuition later and here are the results. It turned out that the trick was to mix the colours together. It was many years ago that I first found out that Art and Science have different primary colours. In Physics, we start with darkness and add in coloured LIGHT. This is additive colour mixing where extra energy at different wavelengths is added to the spectrum. You can add in red, green and blue and you add these frequencies to get white. In Art, it's about what reflects back when you shine on white light. Or more to the point, what gets absorbed. That's why paint mixing is called SUBTRACTIVE colour mixing. Each pigment absorbs different frequencies and what's left gets reflected back. Now I know the theory I just need to get some talent ...

Offspring 1 at Yorkshire Sculpture Park

 I liked this fountain at Yorkshire Sculpture Park. It is convex about one axis which means that I look thinner laterally but am the same height as normal.

 I was interested that the water wasn't an even flow but was coming down in blobs with gaps between. The pump was making a steady hum which means that it was probably vibrating the whole fountain so that the flow from the reservoir down was not even.