Huh, well I guess there goes my theory about the incentive. What a bummer. I would have thought that at least with search engine scraping, they would stop expending the effort once the results dried up.
Well what I'm suggesting isn't about blocking the bots, it's about removing the incentive. So in this case, I think the more obvious it is the better. I would want them to realize as soon as possible that they are 100% wasting their time.
If anything, it might be best to return a page that explicitly states "Sorry, this search engine no longer supports SEO footprint search queries."
I'm not so sure about this. The spammers goal is to build up as big a list of link spam targets as possible. If one spammer chooses to only scrape minor engines and another only major engines, the one scraping the major engines will probably come out on top despite the higher cost. Whoever is abusing OP's search engine is likely doing it to supplement the data they are already scraping from the major engines.
For OP, I think simply not returning results at all is a more practical measure because it removes the reward completely. Captchas and bot detection keep the reward in play, while taking away the results entirely makes the entire pursuit futile.
That would probably help, but it's also a continuation of the cat and mouse game. There are plenty of captcha breaking services out there, it only cost about $1 to programmatically solve 1000 captchas.
So spammers have latched onto your search engine because they are getting useful results. They are able to systematically discover websites built on certain platforms that allow users to post content containing links, which they can target for link spam. It is very difficult to fight this on a technical level because there is an entire industry built around blackhat SEO, with all kinds of softwares and services dedicated to thwarting your defensive efforts. Even Google struggles to keep up with this.
However, they are also systematically feeding you their footprint lists. I imagine you could put together a footprint blacklist pretty quickly, and just stop returning results for any obvious spam queries like those containing "powered by wordpress".
It's not a very elegant solution I'll admit. It won't stop the bots from trying, and you may have to circle back periodically to add new footprints as they surface. But it's a potentially quick and easy way to stop rewarding their efforts, and the blackhat world is pretty used to burning out their resources so hopefully they will figure out it's a dead end and move on.
Been a while since I read up on this, but I think the problem is the energy cost of extracting CO2 from sea water makes it a wash at least in terms of CO2 reduction.
I don't see the bizarre part. Wikipedia says Barron was born in 1927 when we were still figuring out the basics of aviation, and just a few decades later he was making these plans in the midst of the space race. Considering the rate of progress he had witnessed in his time, it's not very surprising that he expected us to aggressively colonize space in his lifetime.
Maybe I have overly romanticized notions of what could have been, but I feel like humanity lost out big time when the space shuttle was chosen over a manned mission to Mars.