- Some of the most innovative and unique art in the past twenty years has been the proliferation of new optical illusions. So go hallucinate.
- I’m more surprised that this isn’t in Japan; robot waiters: because they have a better service attitude than humans.
- The first time lightning has been captured by an x-ray camera. Lightning has a cool (but expected) beam rising to the heavens.
- An awesome collection of japanese graphic design.
- For you math nerds: Terry Tao has come across an interesting problem in control theory.
The Browser has a great interview with Brent Landau on the biblical origins of the christmas story. Landau just released a book translating a text from Syriac that has been lying about in the Vatican archives. It is the story of the Wise Men from their perspective, only now there are twelve of them, they come from China, and the star that they see is a starchild named Jesus. From the interview:
Yes, in the infancy narratives of Matthew and Luke, it says he is born in Bethlehem. You would think, since these two infancy narratives agree on it, that that would speak favourably to historical credibility. The problem is that Matthew and Luke have very different ways of explaining why Jesus is born in Bethlehem. In Luke you have the census. The family lives in Nazareth and they only go down to Bethlehem because everybody is required to go back to their home town. Jesus is born while they’re there and then they go back to Nazareth, because that’s where they live. In Matthew, on the other hand, it seems as if Jesus is born in Bethlehem because that’s where his parents live. So when the Magi come and visit Jesus, it says that the star shone over the place where the child was. It doesn’t say it was a manger like in Luke; it says it stood over the house where the child was. Presumably they just lived in Bethlehem and they only left because Herod was trying to kill Jesus and resettled in Nazareth because of that. So Matthew and Luke disagree and Mark never says anything about Jesus being born in Bethlehem. John, interestingly enough, has a scene in chapter 7 where some people are debating whether or not Jesus is the Messiah. And somebody essentially says, ‘He can’t be the Messiah, the Messiah is supposed to come from Bethlehem.’
…Dell deChant, the author of the book, says that, actually, the modern celebration of Christmas is profoundly religious – it’s just not a religion in the way that most of us are used to looking at one, or conceiving of a religion. It’s got its rituals, it’s got its god, and that god is Santa Claus. One of the most interesting points that the book makes is just how angry and upset people get if anybody is so foolish as to say in public, ‘Well, Santa Claus doesn’t exist!’
Sadly, it was cloudy where I was during the lunar eclipse so I didn’t get to see it. But a webvideo is basically as good as seeing it in real life, isn’t it? I’m sad that I didn’t get to see the red moon (it turns red because that is the color that primarily gets refracted around the earth and hits the moon). But the best part is learning new moon-related facts! For instance: you know how in every cheesy time-travel movie, future-man knows exactly when the eclipse will happen and uses that to his advantage? Well that kinda really happened (except for the time travel part):
According to legend, Columbus, looking at an astronomical almanac compiled by a German mathematician, realized that a total eclipse of the moon would occur on Feb. 29, 1504.
He called the native leaders and warned them if they did not help, he would make the moon disappear the following night.
The warning, of course, came true, prompting the terrified people to beg Columbus to restore the moon — which he did, in return for as much food as his men needed. He and the crew were rescued on June 29, 1504.
There is a great comment from a higher-frequency trader that was left on a post on Marginal Revolution. It’s a few comments down on that page. Here’s the background that he gives:
I work as a quant at one of the major high frequency trading firms, this paper is definitely one of the better academic works I’ve seen on the subject. I’ll add a little more. Generally the way that HFT works is by looking for a set of predictive signals in the market. Those signals are combined with liquidity and execution constraints to try to find the most profitable set of parameters after transactions costs are taken into account.
90% of these signals are fall into two major categories: 1) Looking at the price movements of related securities. A good example is SP500 versus Nasdaq. The correlation between the two is around 85% on a daily horizon, but over a horizon of 10 secs or so correlation is virtually zero. So when one moves a certain you bet that the other one will either follow or the first mover will fall back. 2) The other one is by looking at the state of the limit order book and it’s evolution through time. As a very simple example if say you have 20,000 size quantity on the bid and it’s been monotonically increasing and 5,000 size quantity on the ask and it’s monotonically decreasing then it’s very likely that the level on the ask will get wiped out first and the price will go up.
In general what these two add up to is trying to distinguish noisy trades versus signal trades. Speculators/investors/hedgers/etc. are the primary players in the market. Some of those trades contain high information (e.g. maybe a person with access to insider information buying up stock before some announcement), some of them contain virtually no information and are pure noise (e.g. granny liquidating some of her portfolio for monthly expenses). In a naive market with no HFT signals we have no way of assessing the informational content of individual trades, we only have an estimated aggregate or average informational content of trade. Market makers will set their spread and sizes according to this aggregated informational content.
But over any sample the estimated average informational content of trades will not be the same as the realized, for example one week might more than usual insider trading, one month it might make up a small fraction. There’s also a ton of path dependency when you work out the math, that amounts to pure randomness. Because of this securities will not perfectly track their “true price.” The deviation is still stationary, because the more out of line the prices get with the fundamentals the more speculators will step in and push it back. No one is smarter than the market 100% of the time so every time a fundamental speculator sees a price that’s too low/high there’s some chance that the market is right and his valuation is missing something and some chance he’s right. Speculators that aren’t very good are probably only going to be “beating the market” when the valuation on securities looks insanely out of whack or by distributing his portfolio over a wide range of perceived mis-valuations to reduce his volatility. Only the very best speculators are going to be able to get their fundamental valuations consistently right within a small margin of error. So without HFT/Stat Arb./technical trading/whatever you want to call it/etc. the thing that keeps securities from randomly drifting too far are fundamental speculators.
Basically what HFT is doing, instead of fundamentally valuing securites, determining the informational content of individual trades or small time frames, using the signals I mentioned earlier. A segment of the price evolution with high information content tend to look very different from noisy trades on the small scale, but when aggregated up lose this distinguishability. It’s almost symmetrical when you think about it. Fundamental speculators estimate a price for the security and trust in the reliability of the price evolution process in brining the market price to their estimated “true price”. HFT trusts in the reliability of the initial price as being the best estimate of the value of the security and tries to identify errors and miscalculations in the price evolution process.
There is a lot more to that comment there, and plenty of other worthwhile comments as well. Go give them a read!
This article about cyborg plants is full of all sorts of potential scifi goodness.
Cyborg Plant consists of a simple avocado plant (Persea americana) which is nurtured by an attached robotic prosthesis. The prosthesis measures the avocado’s drought stress — indicated by “the position of the leaves and the electrical potential within the trunk” — and irrigates the plant as required. This attachment, which is essentially a spacesuit for plants, enables the avocado to live indoors without human attention for much longer periods of time than would otherwise be possible (the interior of a built space being nearly as hostile for plants as land is for fish).
Or how about:
This might sound like a far-fetched idea, but, as Next Nature notes, a Filipino scientist produced a bio-luminescent Christmas tree by covering it in bio-luminescent bacteria harvested from local squid in 2007, and other researchers have proposed applications for (truly) bio-luminescent plants ranging from lighting highways (which, assuming that the bioluminescent trees would at some point begin to naturalize, might produce the most strikingly beautiful displays of exotic plant invasion imaginable) to crops which glow when they need water. Mushrooms make forests glow; why shouldn’t trees make cities glow?
It also talks about networking plants. As we continue to mechanize food production, cyborg plants are going to become part of our understanding of ‘nature’. What surprises me more, however, is how little this appears in scifi. The concept seems so obvious once you start thinking about it; mammals are made cyborg all the time. Why not plants as well? It often seems that our networked future is entirely too anthro- and mammalian-centric.