Answer: About 20 meters. Th Hubble Space Telescope’s aperture is 2.4 meters. So, you really can’t do it at the present time.
This is one of a large, seemingly inestimable number of practical need-to-know and esoteric questions addressed in Lawrence Weinstein’s book Guesstimation 2.0: Solving Today’s Problems on the Back of a Napkin, a followup book on the earlier Guesstimation: Solving the World’s Problems on the Back of a Cocktail Napkin.
I should say that I personally have an uncanny ability to estimate things. This comes from being an archaeologist with a lot of experience in CRM. For years I had to estimate how much projects would cost and at the same time, how much dirt needed to be moved, how big patches of land were, how thick layer of dirt might be, and how many rusty nails were sitting in a big-ass pile of rusty nails. And so on. I am very rarely surprised at the number something turns out to be. Weinstein’s book is an attempt by an expert estimator to help you to learn to be almost as good as I am at this. Just as important, probably, is that he actually goes ahead and makes these estimates so you can see what the answer to interesting questions might be.
Having said that do remember that estimation is a sociopolitical act as well as a mathematical activity. One can produce estimates that are helpful to a particular cause. You may already be familiar with the question of “should we use cloth or disposable diapers” which became the hotbed of discussion several years ago between environmentalists and economists (who are almost always anti-environmentalist, given who tends to butter their bread, as it were). I would not want to guess at Weinstein’s politics, but he shows the bias we often see with number crunchers. In asking the question, how much of a car’s energy requirement would we obtain if we covered the car with solar panels, we seem to see an unfortunate anti-environmental slant. The answer is calculated with numbers that seem biased against getting a very large number and still end up being between 2 and 8%. This is written off as insignificant, but I’m pretty sure that if I came up with a version of gasoline that gave everyone 8% better mileage, I’d get rich.
Anyway, it is a fun book and if you are planning to give someone a present that will cost about 10.00, this is a good choice because they probably don’t already have it!
Stock up on napkins!