×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Comments

top

How To Build a Quantum Telescope

dak664 Re:The image formation process is still the same (60 comments)

That's the infinite plane wave approximation for lattices of infinite extent. Scattered spherical waves from finite objects will result in some energy passing through the aperture for every spatial frequency. Although it could be difficult to sort out which frequencies are contributing (aliasing). Analysis of the through focal series can do that, also changing the convergence of incident illumination.

But if the source is known to be two points, accurate measurement of the spacing between the resulting PSFs is limited only by signal to noise.

about two weeks ago
top

How To Build a Quantum Telescope

dak664 Re:The image formation process is still the same (60 comments)

Yes, and what's more diffraction causes no fundamental limit to resolution, it just happens to be the distance between the first zeroes of an interference function. For two point sources of equal intensity that leads to an easily seen contrast difference of around 25% but trained observers can detect 5%. On electronic displays the contrast can be cranked up arbitrarily.

The fundamental limit to resolution is signal-to-nose.

about two weeks ago
top

Ask Slashdot: What Essays and Short Stories Should Be In a Course On Futurism?

dak664 Technocracy Study Guide (293 comments)

http://www.technocracy.org/stu...

Written mostly during the 1930s by M. King Hubbert of peak oil infamy. Describes a sustainable society directed by science instead of wishful thinking.

about 2 months ago
top

Mt. Gox Shuts Down: Collapse Should Come As No Surprise

dak664 Re:Can someone explain this theft? (232 comments)

Isn't the history of a bitcoin included in the block chain? And the stolen bitcoins identifiable?

If so whoever tries to use one risks being traced, moreover the recipient could be considered as knowingly accepting stolen goods..

Sort of like the haul from a bank robbery having an indelible "This money stolen from Bank X" printed on every bill.

about 2 months ago
top

Fixing Broken Links With the Internet Archive

dak664 Re:Please no? (79 comments)

Presumably the wayback redirect would tell you the page does not exist, but the he last time it could be loaded, this was the content. What's wrong with that?

about 3 months ago
top

Ask Slashdot: What's the Most Often-Run Piece of Code -- Ever?

dak664 Re:idle time (533 comments)

The idle loop is alive and well in embedded systems. In some cases energy use is minimized by using a slow clock chosen for some small fraction of idle time, in others by sleeping between bursts of fast processing.

x86 idle power reduction under unix started sometime in the late 1990s
https://blogs.oracle.com/bholler/entry/the_most_executed_code_in

Other OS starting using it around 2000
http://en.wikipedia.org/wiki/System_Idle_Process

Thus seti@home launched in 1999 could legitimately claim it made use of otherwise wasted CPU cycles on the Mac and Windows 95 clients.

about 3 months ago
top

Ask Slashdot: What's the Most Often-Run Piece of Code -- Ever?

dak664 Re:idle time (533 comments)

On modern operating systems the idle loop is never coded in a high level language. It is painstakingly optimized in assembly language, for maximum speed.

about 3 months ago
top

Windows 9 Already? Apparently, Yes.

dak664 Re:9.1 (1009 comments)

And a wireless mouse under the covers.

about 3 months ago
top

Why We Think There's a Multiverse, Not Just Our Universe

dak664 Re:Greeks had that (458 comments)

Another advantage not mentioned in the wiki article was that someone could hold an office only once. That meant when some crises occurred there were probably several people immediately at hand who had previous experience directing public policy.

about 3 months ago
top

How Asimov's Three Laws Ran Out of Steam

dak664 Re:ethics of killing and warfare (153 comments)

Moral killing may not be that hard to define. Convert the three laws of robotics into three laws of human morals by taking them in reverse order:

1) Self-preservation
2) Obey orders if no conflict with 1
3) Don't harm others if no conflict with 1 or 2

To be useful in war an AI would have to have to follow those laws, except that self-preservation would apply to whichever human overlords constructed them.

about 4 months ago
top

The Quietest Place On Earth Will Cause You To Hallucinate In 45 Minutes

dak664 Re:Vacuum (332 comments)

I confess to being stupid but endeavor to learn. Your blind spot seems to be the assumption that in equilibrium the radiation from an object must re-emit the same energy per Hz as acquired from the absorption spectrum. Classical thermodynamics, while powerful, leads to an incomplete picture. Statistical thermodynamics says the incoming energy is rapidly randomized among probable states (fortunately for life some of those may start the electron transport chain). The excess energy populates an increasing number of available states until enough of them dissipate (or in vacuum radiate) the excess energy away. Which has very little connection with some hypothetical temperature of the incoming radiation.

about 5 months ago
top

The Quietest Place On Earth Will Cause You To Hallucinate In 45 Minutes

dak664 Re:Vacuum (332 comments)

In thermal equilibrium with the environment, not with each other. An object absorbing more high frequency radiation has to get hotter to radiate that energy at the lower frequencies. Thus any measurable temperature is a property of the object, not the radiation field. You could define the temperature of vacuum as that of a gray body in equilibrium with the local radiation if that makes you happy. Not sure how useful such a definition would be.

about 5 months ago
top

The Quietest Place On Earth Will Cause You To Hallucinate In 45 Minutes

dak664 Re:Vacuum (332 comments)

A thermometer coating with high absorption for solar wavelengths and low emissivity at longer wavelengths would get hotter than one with the opposite characteristic when placed near the Sun. Indeed you could run a heat engine off this temperature difference and as you say it would ultimately be powered by the continuing incident radiation. But the vacuum environment has no inherent temperature of its own, rather a radiation flux which can heat different objects to different temperatures even when both are in thermal equilibrium.

If you enclose a vacuum in a black box with walls at 1 kelvin what is the temperature of the vacuum? If you heat one wall to 5000 kelvin what is the temperature of the vacuum? Is there a gradient? Does it become anisotropic and depend on the orientation of the thermometer?

about 5 months ago
top

The Quietest Place On Earth Will Cause You To Hallucinate In 45 Minutes

dak664 Re:Vacuum (332 comments)

But in that case the thermometer is measuring its own temperature, not "the temperature of the vacuum", whatever that means. And selective coatings with different absorption and emission spectra could change the reading of the thermometer. Does that change the "temperature of the vacuum"?

about 5 months ago
top

Tesla Model S Has Bizarre 'Vampire-Like' Thirst For Electricity At Night

dak664 Re:kWh/day is stupid. (424 comments)

Under SI convention units are always lower case and the abbreviation is capitalized only when the unit derives from a personal name.
So 1 watt = 1 joule/second or 1 W = 1 J/s

Metric prefixes mega and larger are abbreviated upper case, kilo and smaller lower case. MWh, kWh

about 5 months ago
top

Tesla Model S Catches Fire: Is This Tesla's 'Toyota' Moment?

dak664 Re:vs gasoline cars (388 comments)

Watch closely and you will discover they explode several times from multiple angles.

about 7 months ago
top

Pentagon Spent $5 Billion For Weapons On Day Before Shutdown

dak664 Re:Hey guys, seriously. (286 comments)

The 1930s technocracy movement outlined a society without money, thinking that it and "The Price System" inevitably lead to overconsumption and collapse. They suggested replacing it with energy chits equally distributed among the population, valid for one year to prevent debt accumulation.

http://www.technocracy.org/study-guide

about 7 months ago
top

Tech In the Hot Seat For Oct. 1st Obamacare Launch

dak664 Re:Let us opt out. (326 comments)

Lyndon Johnson started the shenanigans with his "unified budget" that included trust funds not subject to budgetary legislation, and over the years Congress used the concept for further obfuscation (such as pinning automatic budget cuts to the unified budget rather than the actual budget).

I have no idea what the current situation is, but the SS trust funds were officially off-budget as of 2005 according to http://www.ssa.gov/history/BudgetTreatment.html

"present law mandates that the two Social Security Trust Funds, and the operations of the Postal Service, are formally considered to be "off-budget" and no longer part of the unified federal budget."

about 7 months ago
top

Physicists Discover Geometry Underlying Particle Physics

dak664 Re:space & time as emergent properties (600 comments)

Much of that analysis might be applied to the photon, as a purely mathematical construct to explain the quantized transfer of action between two events having (by definition) no separation in space-time. However electrons are affected by the intervening space even when there is no interaction, e.g. http://en.wikipedia.org/wiki/Aharonov-Bohm_effect

about 7 months ago

Submissions

top

Duke professor, billionaire debate higher education's value on '60 Minutes'

dak664 dak664 writes  |  about a year ago

dak664 (1992350) writes "Vivek Wadhwa, a former high-tech entrepreneur in the Triangle who now teaches at Duke and Stanford universities, is matched against billionaire Peter Thiel Sunday night in a CBS "60 Minutes" segment exploring the value of a college degree.

Thiel is paying 20 young people $100,000 a year to drop out or not go to college in order to pursue new business ideas.

Wadhwa says Thiel is sending the wrong message."

Link to Original Source

Journals

top

Nothing happened today

dak664 dak664 writes  |  more than 2 years ago

So this is just random gibberish. Move along, nothing to see here.
gkEDdlgmEmDGEkLjVmwjov

Slashdot Account

Need an Account?

Forgot your password?

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>
Sign up for Slashdot Newsletters
Create a Slashdot Account

Loading...