While indeed lots of the buildings of many European cities were destroyed during WWII, most of them were rebuilt in place. That means the street layout of the cities was preserved. So the layout of many European cities usually goes back to the times before Columbus set off, sometimes even 2000 years back to Roman times.

The panels can only warm up by the amount the ground would do so anyway. If anything, they would mean that the area gets cooled down, as they tend to reflect more light back than e.g. sand. And of course the amount of energy converted into electricity won't end up as warmth. Of course, no one would set up a single panel of 50x50 km square in a single piece, but distribute it across the continent, both limiting the possible local impact and the power distribution problems. This example just shows that only a tiny part of the US would needed to be covered with solar cells.

I happen to live in Germany and there are no such things as exclusion zones. With the one large windmill close by, you can actually walk up to it till you can touch it with your hand. And why shouldn't you, there is no danger in doing so. What *does* exist are regulations which prohibit building windmills too close to residential areas. This is not because of "dangers" but to prevent people from being plagued by noise and moving shadows.

It is interesting to watch both companies run by Elon Musk: SpaceX and Tesla. Both companies step into fields which were so far not run by big businesses. What sets his ventures apart from others, is that they are executed along plans which not only span many years but most importantly on a clear path of technical evolution. When SpaceX went from Falcon1 to Falcon9 and soon to Falcon9 Heavy they followed a clear technical concept, where on each iteration main parts of the previous step were reused, keeping the technological and financial risks in control. What is so faszinating is, that that this progression was clearly planned from the start for a long time and range of products. Tesla is built on the same principle. They started with the roadster. No one expected it to generate multi-billion dollar revenue. But if you multiply its price with the sold number of cars, some nice revenue comes together. By price and concept it was targeted to a small group of wealthy enthusiasts. The roadster created a lot of awareness in the media. Now the technology and the price for batteries has improved vs. the time the roadster has been designed. Also now Tesla has many years of more experience with the technology and production of electrical cars. So the second step in the chain of products is a car which is targeted to a broader audience, by concept and price. The S will be the first model intended to reach higher production numbers. Consequently, in a few years we might expect another Tesla car, once again cheaper and more geared to the mass market, based on the revenue and experiences obtained with the model S.

It is the "shadow" of our own galaxy. This map plots objects which are far out of our own galaxy. If we look into directions where there are a lot of stars in our galaxy, the chance to detect outer-galaxy objects is small as they are behind our starts.

And what if behind the curve you take blind at 30 mph there is a stopped truck for whatever reason? Never drive so fast that you cannot stop in the amount of road you can see.

Having worked on storing data as holograms in crystals, I have to agree that they are the best long-term storage option available today. Even the most pessimistic estimates gives life-times in the hundreds of years, but it could be as well many-thousands of years.

If the data is stored as analog pages - much like in microfiches - the reading of the crystal is as simple as pointing some light at the crystal and the page is visible with the naked eye. The page selection is done by the angle in which the light hits the crystal.

So while holographic data storage does not compete with hard disks in the price/performance region, they are vastly better in the safety part . This technology has already been demonstrated, unfortunately there seems still not enough money around for safe data.