## Search found 2200 matches

Thu May 31, 2018 5:39 pm UTC
Forum: Science
Topic: Cooling gas by expansion
Replies: 6
Views: 480

### Re: Cooling gas by expansion

That's a very interesting post by somebody who has a lot of knowledge on the subject (likely more than me). I didn't check the details, but overall it seems like it could work as described. Describing all black-body emissions as "IR" is confusing, but it's a common enough mistake. It's eno...
Thu May 31, 2018 3:54 pm UTC
Forum: Science
Topic: Cooling gas by expansion
Replies: 6
Views: 480

### Re: Cooling gas by expansion

Temperature as a concept doesn't work too well in a gas with zero pressure. You should be able to cool the ship though. Aerosol cans will lose heat while spraying into open air, and I don't think the ambient pressure is making a strong contribution. Can't make a strong argument/reference for that of...
Wed May 30, 2018 7:25 pm UTC
Forum: Science
Topic: Deep Drill Industry
Replies: 16
Views: 972

### Re: Deep Drill Industry

What do you suppose the concentration of osmium in seawater is? How many tons of water would you need to process? A good question. Tons don't seem like the right unit to me, though. I went with cubic km of seawater per kg of Osmium. I got the concentration from here . There's a big uncertainty in t...
Sat May 26, 2018 4:20 pm UTC
Forum: Science
Topic: Particles as sets?
Replies: 7
Views: 1239

### Re: Particles as sets?

You're right. Whitehead and Russell were attempting to unify all of mathematics (or at least point in a direction they believed would work), but not using Set Theory, which I was mistaken about. Later mathematicians projected Set Theory onto their work. Gödel did come along and crash the party, thou...
Sat May 26, 2018 9:39 am UTC
Forum: Science
Topic: Particles as sets?
Replies: 7
Views: 1239

### Re: Particles as sets?

It's worth pointing out that the quest to ground all mathematics in Set Theory ultimately failed.
Sat May 26, 2018 8:10 am UTC
Forum: Science
Topic: Deep Drill Industry
Replies: 16
Views: 972

### Re: Deep Drill Industry

If the main argument is an exhaustion of bulk "stuff" digging is going to beat drilling in all but specialized cases. The mining industry already does lots of open-pit extraction, because it is a lot safer and presumably cheaper. Not pretty, but obligatory remediation afterwards mitigates ...
Fri May 25, 2018 1:11 pm UTC
Forum: Coding
Topic: What language should I learn?
Replies: 14
Views: 2844

### Re: What language should I learn?

I've been having a lot of fun learning Kotlin . It's a staticly-typed language mainly for the Java Virtual Machine, with support for compiling to Javascript and native support via LLVM is on the way . It has much better support for Javascript and Java interopability than Scala , generally compiles f...
Wed Feb 14, 2018 3:23 pm UTC
Forum: Science
Topic: Explosives As A Reflective Wall
Replies: 12
Views: 2011

### Re: Explosives As A Reflective Wall

Shaped charges?
Go nuclear or go home!
Mon Dec 11, 2017 4:18 pm UTC
Forum: Coding
Topic: code for melting computer
Replies: 7
Views: 4477

### Re: code for melting computer

This will only work on obsolete hardware, but it used to not be that difficult (in theory, at least).
http://www.tldp.org/HOWTO/html_single/X ... WTO/#overd
Thu Feb 16, 2017 2:20 pm UTC
Forum: Science
Topic: Walking on a neutronium Dyson Sphere
Replies: 15
Views: 4581

### Re: Walking on a neutronium Dyson Sphere

It doesn't involve a Dyson Sphere, but another SciFi reference is Dragon's Egg by Robert L. Forward, a physicist whose SciFi is fairly hard. Humans orbit a neutron star and send a robot to the surface to interact with a technological civilization there.
Thu Feb 16, 2017 3:06 am UTC
Forum: Science
Topic: Coincidence in Tycho's Model of the Solar System
Replies: 6
Views: 2495

### Re: Coincidence in Tycho's Model of the Solar System

Tycho's system is actually consistent with observations, IIRC. It is just a matter of where you put the origin. A fully geocentric model gets objective stuff wrong, like the phases of Venus.
Tue Jan 03, 2017 1:51 am UTC
Forum: Science
Topic: What to Do With a Nearby Black Hole
Replies: 11
Views: 3795

### Re: What to Do With a Nearby Black Hole

Sorry about being late to the thread. You magically solve the instability problem, park it at a safe distance, and turn matter into energy at a rather nice efficiency. I seem to recall that Lunar-massed is a convenient size. Has anyone else dealt with one of these?" Very old thread Yeah, it's a...
Mon Dec 05, 2016 1:57 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2863
Views: 620963

### Re: RELATIVITY QUESTIONS! (and other common queries)

The energy of a photon can vary depending on the relative motion of the origin/destination (remember, no observations of light unless you are in its path or on the set of Starr Wars!). This is reflected in the wavelength/frequency, however.
Wed Nov 30, 2016 10:09 pm UTC
Forum: Science
Topic: Weakening evidence for dark energy
Replies: 12
Views: 3607

### Re: Weakening evidence for dark energy

I'm not sure if another citation is needed, but Sean Carroll at Caltech writes an awesome blog and this is his field (cosmology)
https://www.preposterousuniverse.com/bl ... rk-energy/
Wed Nov 30, 2016 12:51 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2863
Views: 620963

### Re: RELATIVITY QUESTIONS! (and other common queries)

Can I derail for a second to ask?: thoughtfully mentioned Feynman's QED - how accessible is the text/what level of knowledge does it assume, and how much ground does it cover? I have a very superficial grasp of QFT which I would like to expand on, is all. It's intended for a general audience. There...
Wed Nov 30, 2016 4:20 am UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2863
Views: 620963

### Re: RELATIVITY QUESTIONS! (and other common queries)

It's probably worth pointing out that in quantum field theories, the fields aren't actual physical fields like the electric field or magnetic fields but an underlying abstraction from which observables are derived. The matter particles such as electrons and muons are fields as well as the photons pe...
Tue Nov 29, 2016 1:57 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2863
Views: 620963

### Re: RELATIVITY QUESTIONS! (and other common queries)

jewish_scientist wrote:
Xanthir wrote:Light is literally an EM wave.

I thought of EM waves as the sum of many photons, and that light refers to photons and/or EM waves.

Okay, what is the minimum number of photons that makes a wave?
The whole point of early QM and the double-slit experiments is that it's wave-like down to individuals.
Mon Nov 28, 2016 2:28 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2863
Views: 620963

### Re: RELATIVITY QUESTIONS! (and other common queries)

This should be a bannable offense.
Thu Nov 24, 2016 11:45 pm UTC
Forum: Science
Topic: Is entanglement that surprising?
Replies: 27
Views: 6353

### Re: Is entanglement that surprising?

I have a pretty straightforward take on this, and it isn't really too unorthodox. Newtonian Physics is a model, and isn't "real". Intuitions based on reality and evolution (also based, more indirectly, on reality) have no expectations of correspondence. No surprises here.
Thu Nov 24, 2016 11:28 pm UTC
Forum: Science
Topic: Classifing Organism by Mechanical Structure
Replies: 18
Views: 4035

### Re: Classifing Organism by Mechanical Structure

There is a super book on the mechanics of living things titled Cat's Paws and Catapults . You should find it entertaining and edifying, even if it doesn't help with this question. Fun Fact: some clams have muscles that are relaxed in the shortened state, to expend less energy holding their shells cl...
Thu Nov 24, 2016 11:19 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2863
Views: 620963

### Re: RELATIVITY QUESTIONS! (and other common queries)

As usual, QM seems to be crashing the party . But at least it fixes those awful singularities and other problems. EDIT Did Maxwell's Equations come from observations that e.g. light didn't travel instantaneously? Maxwell's Equations are a synthesis of relationships (Gauss, Ampere, and Faraday) that ...
Mon Sep 05, 2016 2:51 am UTC
Forum: Science
Topic: In 1Billion Years, Earth will become a second Venus.
Replies: 7
Views: 2424

### Re: In 1Billion Years, Earth will become a second Venus.

There's a lot of space between uninhabitable and "burning away all traces". The surface of Earth in a billion years will probably be in a condition that doesn't support life "as we know it", but if anyone bothered to come by and have a look, they would probably find some remnants.
Sat Jul 23, 2016 4:02 pm UTC
Forum: Coding
Topic: How do you manage Python dependencies?
Replies: 8
Views: 4599

### Re: How do you manage Python dependencies?

BeautifulSoup also overloads a lot of operators for its functionality, which can lead to the usual confusions and difficult-to-maintain code. Kinda nice for quick one-offs or interactive interpreter sessions, but beyond that, I would try to stick to html5lib nowadaze.
Sun Jun 12, 2016 4:04 pm UTC
Forum: Science
Topic: Alkaline Food
Replies: 26
Views: 6014

### Re: Alkaline Food

To be fair, colas are quite acidic, with both carbonic and phosphoric acids. A quick google put the pH around 2.5.
Mon May 02, 2016 3:20 pm UTC
Forum: Coding
Topic: How do I become a hardcore/professional software engineer?
Replies: 6
Views: 6658

### Re: How do I become a hardcore/professional software engineer?

This is a useful guide to becoming a programmer, but it sounds like you may have some of that covered. http://www.catb.org/esr/faqs/hacker-howto.html I am also something of a "research programmer". I don't get involved in the research or academics of what I'm coding, but I do most of my co...
Tue Apr 19, 2016 5:34 pm UTC
Forum: Science
Topic: square base cups
Replies: 24
Views: 5144

### Re: square base cups

Even worse are cans that bulge out! They are cool in their transparency, though. The sloshing liquid was visible. Some sort of stiff plastic with an aluminum top.
Sat Apr 02, 2016 7:37 pm UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 22572

### Re: Can you (passively) heat an object hotter than your source?

I am pretty sure that Thermodynamics requires a perfect absorber to also be a perfect emitter. This looks like a good link, but Hyperphysics isn't coming up for me right now. Ahh, here's a cached page: http://webcache.googleusercontent.com/search?q=cache:tO7d88MAVX0J:hyperphysics.phy-astr.gsu.edu/hb...
Fri Mar 18, 2016 8:00 pm UTC
Forum: Coding
Topic: The "IT DOESN'T WORK!" thread
Replies: 1958
Views: 505413

### Re: The "IT DOESN'T WORK!" wool

I'm not a database expert, but the advice I usually see is to not put too much logic into the SQL (unless there's a good reason not to, which usually implies you Know What You're Doing and wouldn't be asking), leave that in your programming language. Just stick to SELECT and UPDATE as far as the SQL...
Thu Mar 17, 2016 2:26 am UTC
Forum: Science
Topic: Does potential energy have mass?
Replies: 78
Views: 13950

### Re: Does potential energy have mass?

In bulk matter, which is what most folk are familiar with, mass is potential energy. Ninety-six to ninety-seven percent comes from the binding forces inside protons and neutrons. The rest mass of elementary particles comes from interactions with the Higgs field, in straightforward ways with the weak...
Sun Mar 13, 2016 3:12 am UTC
Forum: Science
Topic: square base cups
Replies: 24
Views: 5144

### Re: square base cups

Obviously, triangles are optimal then.

Step two (?)

Profit!
Thu Mar 10, 2016 10:57 am UTC
Forum: General
Topic: It has Endginned. (Mod Madness 2016)
Replies: 220
Views: 62889

### Re: It Begends. (Mod Madness 2016)

I just want to know how I get assistance from the moderation staff with taking the week off. Will I still receive my usual compensation?
Wed Mar 09, 2016 12:10 pm UTC
Forum: Science
Topic: Refraction of different wavelengths in atmosphere
Replies: 5
Views: 2736

### Re: Refraction of different wavelengths in atmosphere

Most of the time the sun is more or less overhead. When it's close to the horizon, you notice the refraction.

But yeah, the ionosphere is going to make this problem about more than just refraction.
Sun Mar 06, 2016 2:16 pm UTC
Forum: Coding
Topic: IDEs and the death of the command line interface
Replies: 25
Views: 7913

### Re: IDEs and the death of the command line interface

I have migrated from Kate to Geany , give it a try. I have been doing a bit of Java/Scala/Android-related stuff, and it's hard to give up the IDE there, but for anything else, a text editor+REPL+browser (for javascript, web apps, etc) and maybe a terminal tab for mathomatic when I need to do a littl...
Sat Feb 27, 2016 11:57 pm UTC
Forum: Science
Topic: Quantum Fluctuations questions
Replies: 21
Views: 5806

### Re: Quantum Fluctuations questions

This may be a weird notion but could the virtual particles be (a part of) dark matter? The density is extremely low but space is extremely big. Not Dark Matter, but Dark Energy, yes (could be). The predicted energy density and what's observed is off by some hundred orders of magnitude, however. htt...
Fri Feb 26, 2016 9:04 pm UTC
Forum: Science
Topic: Quantum Fluctuations questions
Replies: 21
Views: 5806

### Re: Quantum Fluctuations questions

Sean Carroll at Caltech posted recently on his blog on this. http://www.preposterousuniverse.com/blog/2016/01/16/quantum-fluctuations/ 1) Empty is not special. Virtual particles happen everywhere. 2) The basic idea behind fluctuations is the Uncertainty Principle. You can't have a unit of space with...
Fri Feb 26, 2016 1:07 am UTC
Forum: Science
Topic: How do nutrients and pharmaceuticals decompose?
Replies: 3
Views: 2393

### Re: How do nutrients and pharmaceuticals decompose?

There's also volatile compounds that simply evaporate, say with fresh herbs and the like.
Fri Feb 19, 2016 7:37 pm UTC
Forum: Science
Topic: is Chicago ever the "front" of the planet?
Replies: 30
Views: 5609

### Re: is Chicago ever the "front" of the planet?

The trouble is, space is big. And mostly space. You can draw a line out from the center of the Earth to the point on its surface that intersects with its orbit on the leading side, but that line will pretty much go on forever without hitting anything, except pretty rarely. It does help that the othe...
Fri Feb 19, 2016 4:51 am UTC
Forum: Science
Topic: is Chicago ever the "front" of the planet?
Replies: 30
Views: 5609

### Re: is Chicago ever the "front" of the planet?

If you want the cold, hard, data, the US Naval Observatory has a software library for calculating positions of celestial bodies.
http://aa.usno.navy.mil/software/novas/novas_info.php
Thu Feb 18, 2016 8:54 pm UTC
Forum: Science
Topic: If spin really did represent particles actual spin...
Replies: 18
Views: 3911

### Re: If spin really did represent particles actual spin...

It's really difficult to represent fundamental particles as little spheres with a definite radius. Composite particles like protons and neutrons are a bit easier, but not by much. There just isn't a well defined surface to work with.
Tue Feb 16, 2016 9:42 pm UTC
Forum: Science
Topic: LIGO Gravity Waves: Questions and Answers
Replies: 49
Views: 7768

### Re: LIGO Gravity Waves: Questions and Answers

Another way to look at this is simply as a consequence of the Big Bang happening everywhere, without a preferred location. You look out into the sky, in any direction, and if there's nothing in the way, you can see all the way to the Big Bang. In EM, there's the hot plasma from in early Universe blo...

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