Forgot your password?
typodupeerror

Comment: Fly neurons? (Score 1) 39

by Doug Merritt (#47503921) Attached to: Method Rapidly Reconstructs Animal's Development Cell By Cell

Very interesting; is there a technical book (or chapter) or paper with a good overview of this comparative aspect of fly neurons?

I was just starting to look around to see what's available on comparative neuroscience in general, based on an interest in the most salient functional differences from human neurons, so anything related to that more general topic would also be welcome.

Comment: Re:What SETI can pick up (Score 2) 453

by Doug Merritt (#46960531) Attached to: Study: Earthlings Not Ready For Alien Encounters, Yet

In theory, if we can capture coherent pictures in the visible spectrum from many billions of light years away, we should be able to do the same with RF.

It's actually very easy to see why the opposite is true: stars famously broadcast a truly vast amount of power in the visible spectrum, which is what makes solar energy and photosynthesis effective.

Humans clearly do not have the power resources of the entire sun to use to power RF broadcasts. The total amount of power we have at our disposal from all sources is a tiny, tiny fraction of what the sun broadcasts.

And most of our power does not go into RF in the first place, it goes into transportation, manufacturing, etc.

So it's quite straightforward that there is no comparison between the brightness of stars in the visible spectrum versus the Earth in RF. Stars win hands down.

It isn't the technology, it's just the hardware.

Unfortunately, it is very much both. It's true that we can do better by building better listening arrays, and SETI has been continually doing that for many years, but there is also a problem of signal to noise ratio that gives a hard limit on sensitivity due to noise from terrestrial sources and from thermal and quantum noise in the receiving electronics.

Part of that could be improved by putting radio telescopes e.g. on the far side of the moon. The electronics issue simply needs better technology.

Comment: What SETI can pick up (Score 4, Interesting) 453

by Doug Merritt (#46955963) Attached to: Study: Earthlings Not Ready For Alien Encounters, Yet

Yet the sky is not saturated with their communications. So therefor those civilizations must be using some other technology.

That seems logical, but that turns out not to be the case. A SETI scientist said in a talk (and I've seen this in articles since) that our deployed SETI listening technology is still nowhere near sensitive enough to pick up signals even from as close as the nearest star (Proxima Centauri, 4 light years away), if a planet there was broadcasting RF at current Earth levels.

(That doesn't mean SETI to date is pointless, because there's always a chance of a highly directional signal beamed our way, or of just something unexpected, like signals far far brighter than Earth's.)

So no, we have no idea whether the sky is saturated with radio waves or not.

Comment: emphasis of GUI efforts (Score 4, Insightful) 52

by Doug Merritt (#46861935) Attached to: Book Review: Designing With the Mind In Mind

I think that you being modded down to -1 is a bit much, but there is a problem here. What you said is potentially well and good for contexts that are purely utilitarian to the degree that anything but pure pragmatic functionality is to be viewed as an active negative, such as industrial control, power plants, etc.

But for most people's desktops, people expect both functionality *and* some degree of modern aesthetics, and there is an extremely common rejection of interfaces that look 15 years old, even if they were considered close to ideally functional and aesthetic 15 years ago.

Since that is demonstrably what the market generally wants, that is therefore the general trend over time: "flashy graphics" are sometimes overdone, but the word "flashy" is in the eye of the beholder, and most improvements to GUIs over the decades have been about modernization to meet the moving target of whatever "modern" means in each era, with actual breakthroughs in usability being far less common.

Furthermore, the people who design and implement GUIs are (with the exception of 1-person development teams) rarely the same team members who would address software vulnerabilities, so maybe that's where your -1 came from.

Comment: Re:why does a decoder need execheap? (Score 1) 212

by Doug Merritt (#46470017) Attached to: <em>Portal 2</em> Incompatible With SELinux
There *is* such a thing as (write, execute), and this is what it is currently using, and people are complaining quite bitterly about it doing that, because it's a security weakness that is exploitable via buffer overflows etc.

Basically the fact that it allows for dynamic JIT compilation is exactly what people don't want the bad guys to be doing; potentially that turns a small bug into a complete take-over-the-machine exploit.

I'm afraid I was taking all that for granted in my original comment, which instead was about potential reasons why they might not have done something different as people are suggesting in hindsight.

Comment: Re:why does a decoder need execheap? (Score 1) 212

by Doug Merritt (#46456425) Attached to: <em>Portal 2</em> Incompatible With SELinux
I did mean that about time pressure, but I don't understand what you are suggesting.

The scenario is to suppose that they have some audio algorithm that is based on creating and executing a block of code a bunch of times, but for a very small fraction of a second, and then, critical assumption, it needs to create and execute a slightly different block of code, and so on, over and over.

Long ago I saw a demo of an Amiga video capture program that had precisely that sort of thing going on, where they could only get the throughput they needed by using self-modifying code, changing one instruction in an inner loop on a regular basis, and their approach held up under scrutiny of 100 developers critiquing them; it really was needed.

So I am sure that such things do arise in the real world; whether the current codebase truly has such a need, I don't know.

So *if* they have this need, then every time they create or modify a code block, they need it to be writable, but when they execute what they wrote, security issues insist that it it should go from (write,no-execute) to (no-write,execute), every single time.

Making that permissions change requires a system call every time, unavoidably.

Any scheme that allows avoiding that system call is inherently making different assumptions than I did above. Without knowledge of their algorithms, I don't see how we can be sure that assumptions like that are either right or wrong; I'm just pointing out that *if* they are correct, they explain why the codebase does what it does.

An alternative explanation that I tried to give a nod to is that they may have simply done a premature optimization that was not actually needed, but again, motivated as outlined above.

Comment: Re:why does a decoder need execheap? (Score 1) 212

by Doug Merritt (#46440667) Attached to: <em>Portal 2</em> Incompatible With SELinux
Whether it is noticeably expensive depends on endless details of their code, but if they did extremely fast JIT code generation on a very frequent basis (possibly just a single instruction change), then the reflagging syscall would be equally frequent, and the context switch overhead could dominate.

The scenario under which it truly hurts is possibly unlikely, I'll grant, but at the time of implementation it probably seemed like the simplest and fastest approach, and clearly they were thinking about speed, not security and Return Oriented Programming and such.

+ - The Real Story of Hacking Together the Commodore C128->

Submitted by szczys
szczys (3402149) writes "Bil Herd was the designer and hardware lead for the Commodore C128. He reminisces about the herculean effort his team took on in order to bring the hardware to market in just five months. At the time the company had the resources to roll their of silicon (that're right, custom chips!) but this also meant that for three of those five months they didn't actually have the integrated circuits the computer was based on."
Link to Original Source

Comment: Re:Wasn't that difficult when I went through it (Score 1) 279

by Doug Merritt (#45320443) Attached to: Why Organic Chemistry Is So Difficult For Pre-Med Students
You have been misinformed. Doctors are *not* "supposed to be the smartest people on the planet", not even close.

The average citizen in the street may think so, but that's not saying anything.

As for physics, it doesn't make people smart to study physics, it just tends to attract some of the smartest students. Having pre-meds major in physics wouldn't make them any smarter.

+ - Should more math and equations be used in the popular press?-> 1

Submitted by raque
raque (457836) writes "The NYTimes (standard disclaimers apply) published two OP-EDs in their Philosophy section (first here second here), The Stone, discussing how Heisenberg's Uncertainty principle is abused. The second is a followup to the first. The author struggled to make clear his point and left the impression he was creating a strawman argument. In his followup he said that he was avoiding equations due to his writing for a general audience. I replied to both articles as Rtbinc, in the second I put up the following comment:

One of the issues is that Dr Callendar has is a fear of Math and equations in popular reading. A lot of other people are afraid of these few very pretty symbols. Lets do an experiment and see if using some equations and symbols drives readers into fits of terror and prevents their understanding as they cower shivering under their chairs.

The below is from Heinz Pagels in the Cosmic Code (available on Kindle from Amazon and Nook from B&N for about 10 bucks). It shows up on Google books too. Go look, it's fun.

One part of the Uncertainty Principal is (p)x(q)h – where p and q (the is pronounced delta, e.g., delta-p) are the sums of all of the uncertainties — or differences — in a huge pile of measurements of the position and velocity of some particle we're measuring – and h is the tiny, but still not zero, number called the Plank constant. The mathematical symbols haven't changed meaning, so if h ain't zero, neither p or q can be either. We can be as precise as we like, until we hit the Plank Constant. This is not some mathematical oddity, it is how the universe operates. That is weird, and that is one example of quantum weirdness.

The question for the experiment is: Would Dr Callendar have done better to use the equation in the first article instead of metaphors from TV and Movies? Or, did they so frighten you that you need a good stiff brandy and a foot rub.

So I'm asking the same question to everyone on Slashdot. Would Dr Callendar been better off just diving in and dealing with Heisenberg and quantum mechanics using the tools that were developed for it."
Link to Original Source

+ - Monogamy May Have Evolved to Prevent Infanticide->

Submitted by sciencehabit
sciencehabit (1205606) writes "Human males and females have a strong tendency to live together in monogamous pairs, albeit for highly varied periods of time and degrees of fidelity. Just how such behavior arose has been the topic of much debate among researchers. A new study comes to a startling conclusion: Among primates, including perhaps humans, monogamy evolved because it protected infants from being killed by rival males."
Link to Original Source

+ - William Shatner Loses Bid to Name Pluto->

Submitted by sciencehabit
sciencehabit (1205606) writes "A few months ago, when William Shatner, the actor who played Star Trek's Captain Kirk, heard that scientists were asking people to vote on names for Pluto's fourth and fifth moons, he lobbied that one satellite be called Vulcan, the home planet of Mr. Spock—and the name came out on top, far surpassing all others in the voting. Today, however, scientists announced that the moons will instead bear names that better reflect Pluto's role in mythology as the god of the underworld. One satellite will be christened Kerberos, for Pluto's three-headed dog, and the other Styx, for the river dividing the world of the living from the underworld. Kerberos is the Greek name for Cerberus, which placed number two in the voting, while Styx came in third. Why not Vulcan? Astronomers once used that name for what turned out to be a nonexistent planet inside Mercury's orbit, and its connection to the mythological Pluto was tenuous; so rejecting the name was—as Mr. Spock might say—the logical thing to do.
 "

Link to Original Source

+ - Proof mooted for Heisenberg's uncertainty principle->

Submitted by ananyo
ananyo (2519492) writes "Encapsulating the strangeness of quantum mechanics is a single mathematical expression. According to every undergraduate physics textbook, the uncertainty principle states that it is impossible to simultaneously know the exact position and momentum of a subatomic particle — the more precisely one knows the particle’s position at a given moment, the less precisely one can know the value of its momentum. But the original version of the principle, put forward by physicist Werner Heisenberg in 1927, couches quantum indeterminism in a different way — as a fundamental limit to how well a detector can measure quantum properties. Heisenberg offered no direct proof for this version of his principle. Now researchers say they have such a proof. If they're right, it would put the measurement aspect of the uncertainty principle on solid ground — something that researchers had started to question — but it would also suggest that quantum-encrypted messages can be transmitted securely."
Link to Original Source

It seems that more and more mathematicians are using a new, high level language named "research student".

Working...