Gilded

Fantastic. I have a hotplate+stirrer combination but if I didn't I'd probably build something like that as I have some Nd-magnets and suitable fans. I wonder if you could fit a heating element in between the surface (glass in that case) and the fan and magnets.

"Nothingness" isn't exactly as much of a physical concept as it is a very abstract, human concept. I wouldn't say a "perfect" vacuum is nothing, as it has various characteristics that we can observe.

Due to their body structure ants are capable of taking a surprising amount of punishment. But the main factor is their terminal velocity, the maximum velocity they reach when falling. It's very low compared to humans for example, meaning that they reach it in a very short time. Thus, an ant falling 600 meters from the top of a radio mast isn't going to get any more hurt than an ant falling 10 meters from a tree.

Seeing how well Wikipedia has done in the comparisons with other encyclopedias I'd say it's viable in that sense. For academic research I prefer to think of Wikipedia articles as mostly excellent summaries. The viable sources are often found as reference links at the bottom of the page.

Sam Barros of PowerLabs got his hands on a CO2 tube a few years back and as a result some interesting stuff about optics, power supplies and cooling can be found here:

http://www.powerlabs.org/laser.htm

1) Buy tube on eBay

2) Build power supply

3) Build cooling system

4) Get a (ZnSe) lens for metal cutting

As noted on the page, you can drive the tube with excess power for better results but it will kill the tube faster than normal use would.

sorry, i really don't get what you're saying

what do you mean mathematical way?

"meters/seconds/seconds" just seemed like something that might cause confusion if you're asked to describe acceleration mathematically.

and "the rate of change of velocity" is definition of acceleration so It's probably easier to just say acceleration. ?

Didn't you ask what you should answer if you're asked what acceleration is or what it means? "It's acceleration" isn't really sufficient in that case.

The three most abundant elements:

1.) Hydrogen

2.) Helium

3.) Lithium

(universe)

Did you read this thread at all? Lithium isn't the third most abundant element in the universe.

Same is happening in Scandinavia where people make routine visits to Estonia and Germany to buy cheap alcohol. Load up the car and go home to have a massive drinking party.

Yep. Estonia is very popular in Finland for that purpose. The legal drinking age here is 18, but upwards from 22% alcohol you have to be 20.

So if a question asks “what is acceleration of something” I should say “it’s X meters/second/second”

Yes, no ?

Don't say that in a mathematical way though, it would mean that "acceleration = velocity". One pretty straightforward and correct answer to a question like that is "the rate of change of velocity".

They're allowed to. It's the government that can't deprive you of this (in the US, at least).

Every employer works for the Man, man! Damn them, circumventing the First Amendment.

Manbearpig!

Half man, half bear and half pig! I'm serial!

Either way, during John Kanzius' research, he found out that he could burn salt water. Yep... You heard me correctly. Salt water. Enjoy:

 

http://www.youtube.com/watch?v=s_vjQgCvISU

Wow, he's separating water into hydrogen and oxygen, a gas mix which can be ignited! I think that was first done in the early 1800s. The cancer research is rather interesting though. And I suppose some industrial processes could benefit from decomposition of molecules without electrodes.

Seeing how well relativity has been doing for so many years I'd say that the physical concept of time cannot just be ignored.

To cut sheet metal (like steel etc.) properly you need a rather powerful laser. I'd say the "easiest" way to go about this is a CO2 laser..

The right lenses you can buy, making the power supply isn't probably too hard for someone who knows their electronics but making a good CO2 laser discharge tube out of scratch sounds pretty difficult even with the proper equipment. Of course, you can find these tubes on eBay so if you don't mind the engineering process being just the construction of the power supply then go ahead.

Low carb diets base on ketosis (at least the ones that start out with basically zero carbohydrate intake) but I recall it taking normally at least a couple of days before ketosis properly starts. Could be that not eating anything at all results in ketosis in under 24h.

I've remained at a fairly constant weight for a very long time even though I'm eating _lots_ of fatty foods (McDonald's, macaroni with cheese... or more like cheese with macaroni, sausage, pizza...) and don't really exercise at all. My calorie intake is sometimes a bit above what it should be and with the amount of fats I'm consuming I probably should be quite overweight by now.

My metabolism is rather fast but not extreme and definitely shouldn't overcome my diet and lack of exercise by itself. However, I normally eat a very large meal around 5h before I go to sleep. I tend to sleep quite long (more than 12h sometimes) and don't really like to eat until I've been awake for at least 3h. For example now I haven't eaten anything in the last 20h, and even though there was about 11h of sleep in between I'm wondering if this is enough for my body to go into "starvation ketosis"? If so, how unhealthy this kind of metabolic cycle is?

You need to figure out how long the force is applied. For example if a person with a mass of 100kg is subjected to an upwards force of 30kN the acceleration is 300m/s^3. Without gravity or air resistance this person would thus reach a respectable speed of 30m/s in 0.1 seconds. Someone else probably remembers how you calculate the apex point when air resitance and acceleration downwards (9.81m/s^3) are known.

I think the only site that was blocked in my high school was a Finnish equivalent of Facebook/MySpace/whatever. Which of course greatly amused me as I hate those kinds of sites. As for other possibly blocked sites I must admit that I never tried to browse for porn though.

Lol.

All publicity is good publicity; what better occasion for Microsoft to display their lack of technical prowess than when the whole world is watching?

Which annihilations are you talking about?

High (GeV range and upwards) energy electron-positron annihilations in general. I had read somewhere that particles like W bosons can be produced instead of photons when the amount of energy increases, I wasn't quite sure about exact figures.

At low energies, significantly below the W and Z mass you will not produce the W and Z mass much because you just don't have enough energy to make their mass (they have to be very off-shell).

Yes, that I had gathered.

However, if the annihilation happens at around the energy of the W or Z mass, then you have what is called resonant production. In essence you have hit the resonant frequency for creating the W or Z, so you make a lot of them.

Hmm I see. But photons can still be created at these energies, it's just very improbable compared to heavy (as in having non-zero proper mass) boson production, right?

The antimatter thread at Astronomy & Cosmology reminded me of something. Specifically, why is the creation of heavy particles like W bosons and such favored over photons in high energy annihilations? Is there some sort of energy limit after which all net energy can't just be "dumped" into photons?

That's one book I've been meaning to read. It caught my attention when it was featured on Wikipedia some time ago. Seems very interesting.

CNO!!!!

Yeah I got it, didn't refresh the page before I replied.

Oxygen is indeed the third most abundant element in the universe according to current observations, both by mass and by number. One of the physics experts can probably explain why the fusion tends so much toward oxygen so that lithium, beryllium and boron are essentially "skipped" (low fusion energies?).

What I'm especially wondering about are the applications, if any, where helium is quite necessary; where it would be very difficult to replace with any other gas.

(By the way does anyone have any info regarding the constancy of helium concentrations in the atmosphere? I suppose it's creeping out of the earth at a fairly constant rate (when discussing periods of even thousands years, considering the long half-lives of thorium and uranium) and is floating off into the higher layers of the atmopshere at a rather constant rate. It would be interesting to know whether even the mentioned 1ppm concentration is actually mostly uncaptured helium from tapped natural gas sources, rather than helium rising somewhat uniformly from the earth around the globe.)