Cap'n Refsmmat

The very best microwave systems from geosynchronous orbit could get perhaps 85% efficiency in transfer. There would likely be more losses in transformers and transmission on the ground, of course -- this is just DC power in to DC power out on the ground. (I wrote a research proposal on this last semester)

Yes indeed. They suggest a sort of mesh antenna about 10km wide that you could even plant crops under. The microwave exposure around the edges would not be above any safety levels, and efficiency would be around 80% for transfer. But if you beam all the way from the moon, that antenna will have to be several times larger. (And the costs of a 10km diameter giant metal antenna are already substantial.)

There's a few ways to beam power. Microwaves work, but from geostationary orbit the beams diverge enough to require a 10km-wide antenna. From the Moon you'd be looking at one very large antenna. Lasers also work, but you'd still need a very large collection area and far better laser power technology. (Current lasers are not particularly efficient and would melt at the power needed for massive energy transfer.) So it'd be a challenge. Building a large enough antenna for microwaves and not frying half a continent may be a challenge.

Here's some reading for you: http://arstechnica.com/science/news/2009/08/arrow-of-time-no-longer-double-ended.ars

Although you can also say "my love is as big as an AU."

Now make it rhyme.

Interesting. I'd love to see how this plays out.

I'm staying out of either side. I don't think climate change can be falsified with a few simple objections, but then these objections seem to have significant merit. I'd rather wait for the dust to settle before deciding.

I've read The Fabric of the Cosmos, and I recall the bucket example. I think (but I do not have my book handy) that the water in the bucket was merely a metaphor for gravitation. That is, water going up the sides of a bucket is like frame dragging, not caused by it. But I'd have to go and get my book to see, and it's inconveniently several dozen miles away at the moment.

There is a very large difference between attacking an idea you believe to be wrong and attacking a person you believe to be wrong. Science successfully does the former all the time, as do most on SFN. You consistently choose the latter. You can make your points without insulting anyone. I will not tolerate your present tactics any longer.

Indeed it doesn't. But the tone still needs improvement. SFN should not be a hostile environment to anyone, even if they post something incorrect. In the science sections, we always attempt to correct and explain mistakes with tact, so that members will be encouraged to continue learning science. The politics section should be no different. When you make a post personal -- even if you are right -- you only make the person you are attacking defensive, and make them far less likely to accept your point. When someone has been attacked, they return fire instead of listening. This is not up for discussion.

Personal attacks are not welcome here. All you are doing is pissing people off, not convincing them of your position. If you can't be civil, don't post.

An interesting article in the Times today: http://www.timesonline.co.uk/tol/news/environment/article7026317.ece Now, of course I realize that this does not represent the majority opinion of scientists or any conclusive disproof of global climate change. There are other records, like sea surface temperature readings, that can be checked against. (Also, how do you disprove that various glaciers are melting?) What would unreliable weather station readings mean for climate change? Ordinarily I'd pose a "big" question at the end of this post, but I know how SFN responds to a climate change thread, so I'll just watch and wait.

When they consider whether to accept you they will consider the difficulty of the classes you took in high school, your grades, etc. Not taking physics isn't a problem, so long as you did take challenging classes and did well in them. Once you're in a program, your high school experience is moot.

BScs won't depend on anything you take in high school. You'll have to get the credit in college one way or the other, either through AP exams (or equivalent) or by taking the actual classes. AP exams are useful, and you'll be able to take more advanced classes sooner, but they are by no means required. Usually schools require some breadth in your studies. My degree program, for example, requires me to take physics, biology, and chemistry. Some only require you to choose a few classes from any science field. It all depends. Even though high school classes are not required, do consider what impression they may give on your college application.

Yeah. You can do arbitrary precision addition and such, but I can't find an option for plotting.

We see light that's taken billions of light years to get here. We see the object as it was billions of light years ago.

Yes, it takes sunlight about eight minutes to reach Earth, so what we see is "delayed" eight minutes.

The US doesn't really have "control." ICANN, which controls the assignment of top-level domains like .com and .net, is based in the US, and so the US government could hypothetically beat ICANN into doing its bidding. But the routers, switches, and servers that make up the core of the Internet are owned by independent businesses and corporations. You could cut off one piece and the others would patch themselves together and work around the hole. The other problem is that the Internet was never made with identity in mind. That is, there's no easy way to verify that information comes from one particular person, or even one particular computer. So stopping spam is a huge challenge.

Oh, sorry, I got totally confused there. Ignore me. I don't see how this could be easily integrated. You'll have to try another method besides separation of variables.

I think there's some element of randomization to their introductions to make them harder to catch by spam filters. We use Akismet and find that it catches most of it, but of course the spammers will try to get around that by changing up their spam text. We ban almost 100 spammers a week. I hardly remember any spam at all when I first became a moderator. Most of the spam now is flagged by Akismet before it's ever posted, but still... the sheer volume is becoming overwhelming. We need better anti-spam tools and systems. And less stupid people who let their computers get infected with malware that spams forums.

This should give you a good introduction to the various ways of making random numbers: http://en.wikipedia.org/wiki/Pseudorandom_number_generator

This shouldn't be too hard. Show us how you'd start it. You'll have to use the chain rule a few times.

Aha. Apparently Mathematica uses machine-precision integers by default on plots. I told it to use 60 digits of precision in its calculations and the plot is now a straight line.

We get a huge amount of spam, and there are many different tactics used to imitate a real human. Many spambots post new threads saying how amazing SFN is and how much they love it here... but if you take a look at their profiles, you'll find their homepage is set to a spam site. A tactic we stopped in its tracks had people posting semi-relevant posts in various threads -- the sort of posts that aren't very helpful but say something reasonably on-topic, in about two sentences -- and then, weeks later, changing their signatures to include spam links. The idea is that we'll no longer be looking at their posts, so nobody will notice the spam links. I disabled links in signatures for anyone under 30 posts. Other people join and send dozens of spam private messages, which is most annoying because they often send them to inactive members, who then have to get a "You have a new private message" email. They're reminded of SFN by getting spam. I put a limit on how many PMs can be sent in a fixed time to make this harder. Others make posts asking "does anyone know a good service to do ____?", so that in a few weeks someone else can come along and provide a convenient link. We do administer a sort of intelligence test. I have a set of stupid questions ("type science in this box", etc.) from which one random question is selected. Bots have to pass the test to register. Since I come up with the questions, they can't have answers pre-programmed. However, they can get human assistance to register, then spam robotically. It's frustrating. Some day I might write software that analyzes the vocabulary and grammar used by users to try to pick out duplicates and shills. Hmm...