Gravity is weird. It is the oldest of the four fundamental forces that we have been able to describe and yet what it is remains mysterious. When Isaac Newton first introduced his theory of gravity and the idea that objects with mass attract each other, he was accused by some critics of introducing a form of mysticism into science by postulating non-contact forces that could act instantaneously over empty space.

Einstein’s theory of general relativity brought in more sophisticated ideas by replacing instantaneous action-at-a-distance between two masses by saying that one mass distorts that space around it and that the distortion spreads through space at the speed of light and that the second mass responds accordingly when that distortion reaches it, thus removing the instantaneous action-at-a-distance problem. His Principle of Equivalence also showed that we cannot distinguish between being in a uniform gravitational field and being subjected to a constant acceleration. When we are in free fall, we are effectively weightless. The catch is that at some point, very quickly, we hit the ground.

Gravity is a ubiquitous force. We cannot shield ourselves from it. All this makes it hard for Earthbound people like us to imagine what life might be like in the absence of gravity. Now with space travel, we see astronauts in space stations in gravity-free situations. It should be noted that that he Earth’s gravitational field at the orbital height of the space station is about 90% of what we feel on Earth. But because they are in free-fall as the station orbits the Earth, they are effectively in zero-gravity (or more accurately microgravity) fields for a long time as long as they are in orbit. This has given us some idea of what life might be like in such an environment but there are still surprises. Part of the surprise is due to the fact that many forces that on Earth are small compared to the Earth’s gravitational field and are swamped by it, become significant when in zero gravity but many people do not realize this.

Take for example, a recent story about a video of Chinese astronauts (they refer to them as taikonauts) that had a glass of water. Since many people expect that in zero gravity water must float in the air in the shape of a sphere, this raised suspicions that the video had not been shot in space. But they are wrong because they ignored how important adhesive forces become in the absence of gravity.
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Dark matter and dark energy have proven to be remarkably elusive, resisting all efforts so far to be directly detected. The best evidence we have for their existence is indirect, through gravitational effects that we have ascribed to their presence. The problem is that the gravitational force is both very weak (the weakest of the four fundamental forces) while at the same time, in the presence of huge masses like the Earth, stars, or galaxies, its effects are also large, dwarfing the effects of other forces. But such indirect evidence for the existence of fundamental particles is never satisfying because scientific history has examples where that has led us astray. So the search goes on, with the construction of evermore sensitive detectors that we hope will finally provide convincing direct evidence.

One of the latest efforts is to send detectors into space.
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Rowan Atkinson is well known as an actor and comedian. But his undergraduate education was in electrical and electronic engineering, with a subsequent master’s degree in control systems. He has written a thoughtful opinion piece on how his early infatuation with electric vehicles as a way to combat climate change has cooled as he learned more about the hidden environmental costs of this technology.

I bought my first electric hybrid 18 years ago and my first pure electric car nine years ago and (notwithstanding our poor electric charging infrastructure) have enjoyed my time with both very much. Electric vehicles may be a bit soulless, but they’re wonderful mechanisms: fast, quiet and, until recently, very cheap to run. But increasingly, I feel a little duped. When you start to drill into the facts, electric motoring doesn’t seem to be quite the environmental panacea it is claimed to be.

As you may know, the government has proposed a ban on the sale of new petrol and diesel cars from 2030. The problem with the initiative is that it seems to be based on conclusions drawn from only one part of a car’s operating life: what comes out of the exhaust pipe. Electric cars, of course, have zero exhaust emissions, which is a welcome development, particularly in respect of the air quality in city centres. But if you zoom out a bit and look at a bigger picture that includes the car’s manufacture, the situation is very different. In advance of the Cop26 climate conference in Glasgow in 2021, Volvo released figures claiming that greenhouse gas emissions during production of an electric car are 70% higher than when manufacturing a petrol one. How so? The problem lies with the lithium-ion batteries fitted currently to nearly all electric vehicles: they’re absurdly heavy, many rare earth metals and huge amounts of energy are required to make them, and they only last about 10 years. It seems a perverse choice of hardware with which to lead the automobile’s fight against the climate crisis.

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Back in 2015, there was this interesting phenomenon about people seeing a photograph of a dress and coming down sharply on two different sides of what colors the dress was, with some saying it was white and gold and others that it was blue and black.

This short video explains what is going on and this phenomenon shows dramatically that our perception of color is not due exclusively to the spectrum of light wavelengths that is reflected off the image and enters our eyes, and thus entirely objective, but also depends on the way that our brain processes sensory input which in turn depends on factors such as the context in which the image is embedded, and thus has a subjective element as well.

I posted recently about the idea of covering large parking lots of stores like Walmart with solar panels. This would provide two benefits. One is that it would provide shade for their customers’ cars, no small benefit in hot areas when going to a car that has been baking in the sun can result in the door handles being too hot to touch and the inside stiflingly hot. The second is that it provides quite a lot of energy that could be used to service their buildings, provide charging stations for electric vehicles, and even sell surplus energy to the grid. I noticed that the parking lot nearby that services the city hall and public library has installed solar panel coverings and has a charging station. It is small in size but the idea seems to be catching on.

Now comes along another idea that also seeks to cover large expanses with solar panels, and this is to put them on floating rafts over large bodies of calm water, like lakes.
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