Radio waves require a larger device to focus them than light waves (or infrared) because they have a much longer wavelength. For example, to produce a beam of 1 degree width in the UHF band (about 400 megahertz) you need a radio dish 50 meters across.
The wireless "line of sight" links also require some space around the beam clear of obstructions.
This would not be a problem if the transmitter is several floors up. The window cleaners might need to wear glasses to protect them from the infrared radiation though. AFAIK infrared is quite safe unless the power level is high. It can be felt on the skin as heat - this is supposedly how Isaac Newton first observed it.
The discs will probably not be sold in rental stores but rather in supermarkets. So while you're shopping for your microwave dinner you can get a movie to go with it and just like the dinner, your movie has a use-by date on it once you open it.
And the supermarket knows you'll be back - after all you have to eat.
The gas giants are thought to have cores of heavier elements like iron and silicon which formed the seed towards which lighter elements gravitated towards during formation.
The problem is not solar wind. Solar wind is far too tenous to have much effect. The two important quantities are temperature and escape velocity. Escape velocity of a planet is the speed an object in orbit has to have to leave it. For Earth, the escape velocity from the surface is about 11 kilometres per second.
At any given temperature a gas has slow moving, medium and fast moving molecules. At a low temperature most molecules move slowly but there are still some fast moving ones. As the temperature goes up there will be more faster moving molecules. Once a significant fraction of molecules is moving faster than the escape velocity the atmosphere will be lost into space.
Also, molecules of lighter gases like helium or hydrogen on average move faster than heavy gases like carbon dioxide or oxygen so they escape into space easier. This is why there's not much helium in the Earth's atmosphere - it doesn't just float to the top, it actually escapes into space pretty quickly. On the other hand, Jupiter has an escape velocity of about 60km/s so it retains all of its helium.
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Radio waves require a larger device to focus them than light waves (or infrared) because they have a much longer wavelength. For example, to produce a beam of 1 degree width in the UHF band (about 400 megahertz) you need a radio dish 50 meters across. The wireless "line of sight" links also require some space around the beam clear of obstructions.
This would not be a problem if the transmitter is several floors up. The window cleaners might need to wear glasses to protect them from the infrared radiation though. AFAIK infrared is quite safe unless the power level is high. It can be felt on the skin as heat - this is supposedly how Isaac Newton first observed it.
The discs will probably not be sold in rental stores but rather in supermarkets. So while you're shopping for your microwave dinner you can get a movie to go with it and just like the dinner, your movie has a use-by date on it once you open it.
And the supermarket knows you'll be back - after all you have to eat.
The gas giants are thought to have cores of heavier elements like iron and silicon which formed the seed towards which lighter elements gravitated towards during formation.
The problem is not solar wind. Solar wind is far too tenous to have much effect. The two important quantities are temperature and escape velocity. Escape velocity of a planet is the speed an object in orbit has to have to leave it. For Earth, the escape velocity from the surface is about 11 kilometres per second.
At any given temperature a gas has slow moving, medium and fast moving molecules. At a low temperature most molecules move slowly but there are still some fast moving ones. As the temperature goes up there will be more faster moving molecules. Once a significant fraction of molecules is moving faster than the escape velocity the atmosphere will be lost into space.
Also, molecules of lighter gases like helium or hydrogen on average move faster than heavy gases like carbon dioxide or oxygen so they escape into space easier. This is why there's not much helium in the Earth's atmosphere - it doesn't just float to the top, it actually escapes into space pretty quickly. On the other hand, Jupiter has an escape velocity of about 60km/s so it retains all of its helium.