Our video experts are weighing in on this one. Balloon or genuine unknown?
Plastic bag solar balloons are really easy to make.
Ah, genuine balloon. :)
Based on the above link from Mthood, I suppose this is a genuine known, now? :-)
Based on Mthood's link, it's obvious that this object is NOT a solar balloon, as they are required to be made of a dark colour so as to absorb as much solar radiation as possible. The object in the video is a very reflective silver, meaning it would absorb very little useful radiation.
I've seen silver balloons work also on Youtube. All shapes in "how to" instruction videos.
Yes, Frek You are correct as usual. Matt is confused as usual. The 'colour' means nothing compared to the absorption of light per material used. It's not as if this is a cotton black or white t-shirt that absorbs or reflects light. Depends on the material used and not the color.
LOL, good one EdMcL! Absurd notion, that darker-coloured objects don't absorb more light than reflective ones... And you actually ca,e across as insultive there at first, but then I realized that you must just be ribbing me. ;)
Anyhow, I did some digging and found that Frek is half-right: some solar balloon designs use a reflective backing on the shaded side of the balloon to help keep heat trapped inside from escaping. However, the balloon still needs to have it's sunlit side either transparent to trap solar radiation , like a greenhouse, or black, to trap the sunlight to begin with. The only drawback to this design is that it has to keep it's reflective side away from the sun, otherwise it isn't likely to trap enough heat to remain buoyant.
That said, I took a closer look at the video to see if it actually had a darkened side, but I realized that since we can't tell what direction the sun's coming from, it's hard to tell if we're seeing shadow or a side that's actually darker-coloured when the specularity disappears. We get a brief few frames of some leaves in a tree, but it's hard to make out the sun's direction from that. Or, it could be entirely black with a shiny surface, it's really hard to tell. As with virtually every video in the Out There section, youtube is the source, so we're definitely not getting the best quality evidence to begin with.