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Comment "Curved" space (Score 1) 96

Yes. Einstein theorized that spacetime is curved around objects...

More accurately, if you chose to define a geodesic as being the path taken by a light ray, then the space-time coordinate system defined by light rays in the presence of gravity obeys a non-Euclidean metric that is described by the metaphor "curved"-- by which we mean, it has the same geometry as a (Euclidean) curved surface in a higher-dimensional embedding space.

Comment Gravity is not instantaneous (Score 1) 96

Are gravitational waves different from gravity? Because this article would have you believe that the speed at which they propagate is speed of light, where as gravity has instant effect AFAIK.

Gravity does not have instantaneous effect.

Nothing physical has instantaneous effect.

In any case, if you're talking about the gravity of something just sitting unmoving, it doesn't really mean anything to say that the gravitational effect is instant, or delayed. It only makes sense to ask the question when something is accelerated away from sitting stationary, and in that case, the effect isn't instantaneous; the change in effect at an observer is at the speed of light.

Comment Compare prediction to reality [Re:Cool!] (Score 2) 96

> Nobody actually ever thought that gravity waves wouldn't exist

Which is precisely why this is such a non-important result. You don't learn much about the universe by demonstrating something everyone already knew is true. It would be much, MUCH more interesting if it didn't work.

To the contrary. Now that we have detected gravitational waves, we can start comparing the predictions to the measured data. Until we had detected them, we couldn't compare theory to data. Now we we have a possibility to do so.

That's why the MMX is cool, and this isn't.
>But it's amazing that we can actually detect it.
From a technology point of view, yes. From a theoretical perspective, not so much.

Comment If you don't like it, don't go there (Score 2) 648

Wired is a site that actually pays their writers. The internet has become a place where everybody wants stuff for free, and expects writers to be unpaid; the internet has been flailing around trying to find a model where writers can actually get paid for their work-- but having trouble finding one.

So, give them a little credit-- if you are neither willing to look at ads nor willing to pay-- basically, you want stuff for free--well, ok, don't go there: you can get plenty of free content elsewhere on the internet. It's a race for the bottom. But they are at least trying to find a way to survive and keep paying their writers.

(Hufflepuff Post is probably about the worst of the lot-- their business model is "we get millions of dollars, people who write for us get nothing.")

Comment Re:The stuff is just too expensive (Score 2) 87

I think what will kill iot is that it's just frankly too expensive.

No, that's just the way technology goes: they sell to the people willing to pay premium prices first, then the cheap bottom of the barrel manufacturers get into the action, and the price drops asymptotically toward zero.

The first hand-held calculators used to cost hundreds of dollars; now you get them free in cereal boxes.

Comment Musk considering what NASA has been researching (Score 4, Informative) 345

NASA has been researching electric aircraft for quite a while. They do have some advantages, although they're not ready to commercialize yet.






Comment An unknown number of flips (Score 1) 634

What a crock. Only one calls the toss. Have you ever actually done a coin-toss?

If you want to be pedantic, neither of them call the toss-- neither candidate was even present. The county clerk of elections both flips the coin (or designates the person who does so), and calls which result goes to which candidate (or designates the person who does so). If the clerk calls heads for one candidate, they are calling tails for the other.

That's the way coin tosses work: calling heads one way also means calling tails the other.

What I find more puzzling, and probably more worthy of attention, is that the media almost instantly put out the story "Hillary won six out of six coin flips"-- but the best reported actual data is that, of the coin flips that were officially recorded, Sanders won five out of six against Clinton, and one out of one against O’Malley. (e.g., this report).
So, was it just coincidence that the media happened to get 6 out of 6 data points about Hillary winning coin flips against Bernie, but zero out of six data points about Bernie winning coin flips against Hillary? What are the odds of that? Well, the same calculation.

The original six out of six number apparently came from the The Des Moines Register, who based their reporting on what had been posted to Facebook (!). In a later story, they stated that the actual found of coin flips was "unknown".

Comment Re:Two-tailed probability distribution (Score 1) 634

No, you're making false assumption. I never said anything about the probability of heads (or tails) coming up 6 times in a row.

Let me explain this again. If you ever have the question of "should I use one-tailed or two-tailed probability distribution in this statistical analysis," here is a clue: always use two-tailed unless there is a very compelling argument not to.

The question is, what are the probabilities of calling a coin toss correctly 6 times in a row.

And two people called the coin toss: Sanders and Clinton. The odds of one of the two of them calling it correctly 6 times in a row is one in 32, not one in 62.


Comment Random or bias? (Score 1) 634

Hahaha no.

The odds of EITHER Bernie OR Hillary getting 6 for 6 would be 1/32. But we are specifically talking about HILLARY, who is the candidate with all the shenanigans.

What you just did here is to insert your own a-priori personal bias into the statistics.

Your personal bias is fine. Just don't confuse it with statistics.

If Bernie won all the coins, it's not because he knows a guy, it's because 1/64 can happen.

Your statement "result X would show shenanigans if it favors candidate Y, but would be explained by random chance if it favors candidate Z" is a statement of personal bias, not a calculation of statistics.

Anyway, other posts say the 6 for 6 wasn't a the whole story anyway.

Yes, exactly. In fact, the best-documented results are from the counties that did their reporting using the election software (about half the counties reported using the software, and half reported by hand). In these counties, Sanders won six coin flips, and Clinton won one.
So, a more interesting question might be this: given that there were about a dozen coin flips, and Clinton and Sanders won roughly equal numbers, what are the chances that the six that Clinton won would be commented on by the news media, while the six that Sanders won would be ignored? Is this random, or is this bias?

Comment Two-tailed probability distribution (Score 1) 634


People make that statistical error all the time. The question is whether to use one-tailed or two-tailed statistical tests. You are proposing using a one-tailed statistical test, but two-tailed is correct here.

The thing that seems anomalous is getting the same result six ties in a row. Whether that's six heads in a row, or six tails in a row, is irrelevant. What you should be testing for is the probability of getting the same result n times in a row, whether that is heads or tails.

http://www.ats.ucla.edu/stat/m... tells more.

But, wait: what if you are about to say "Well, if it had been Bernie that won six times in a row, I'd accept it as chance, but since it's Hillary, I am suspicious"? Wouldn't that be a reason to use one-tailed probabilities?

No. What you just did there was to insert your own bias. The whole point of statistics is to avoid bias.
A good rule is, if you can't decide if you should use two-tailed probability or one-tailed, always use two-tailed.

--in any case, though, if the Washington Post is accurate, there were over a dozen coin flips, and Sanders also won some of the tosses.

Comment update - there were other tosses which Sanders won (Score 5, Informative) 634

Actually, one in 32 odds. The chance that a coin tossed one time lands with the same face up is 1 in 1. The chance that a coin tossed two times lands with the same face up is 1 in 2, etc.

A little over two standard deviations.

However, as Washington Post notes, "see the update below: there were other tosses which Sanders won."

The update states:
Update: The initial 6-for-6 report, from the Des Moines Register missed a few Sanders coin-toss wins. (There were a lot of coin tosses!) The ratio of Clinton to Sanders wins was closer to 50-50, which is what we'd expect.


Comment Dystopia or Utopia: you decide [Re:Target shooting (Score 1) 555

Well, of course that's also the problem with non-smart guns. The difference is that with non-smart guns, the failures are mostly Type I (gun fires when it's not supposed to), while with smart guns, Type I failures are decreased at the expense of an increase in Type II failures (gun doesn't fire when it's supposed to.)

Not necessarily. A gun programmed to scan its video feed, recognize the face of a particular Geoffrey Landis, and shoot - will be called a very smart gun indeed. Such a gun can easily be imagined to have more type-I failures than a 50 year old reliable gun.

Wow, and I'd thought I was the science fiction writer here.

Comment Re:Land Grab (Score 1) 256

Because global warming is something that happens on a very long time scale, and real estate investment is something that happens on a relatively short time scale.

By the middle of the 2100s, the sea level will, if present trends continue, rise enough to flood Miami. But real estate investors look for profits in ten years or less, and sea levels will rise by no more than millimeters over that time scale.

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