Slashdot is powered by your submissions, so send in your scoop


Forgot your password?

Comment: misnomer (Score 1) 2

by stoborrobots (#49581959) Attached to: 8 - Does Gnome depend on systemd, or just logind?

It makes a little more sense to me if I think of it as "whoisloggedind" rather than "letmelogind". (It gets used *AFTER* PAM has already logged the user in - it then tracks the login.)

As far as I can tell, the purpose of the various features is largely around being able to tell who is logged in where and what that implies about their hardware access. (Imagine a grown-up version of "/etc/shutdown.allow".)

As such, I don't see why it need to depend on systemd at all, and I've planned, but not got around to, writing a version that keeps the same state information, but doesn't use systemd. If I can get that working, I will be able to put policykit back on my machine, and get things like networkmanager running again without installing systemd.

Comment: Re:the 8 ball was right! (Score 2) 140

For sending, Ctrl+Enter is your friend.

I think they mean "check" as in "verify".

I'm guessing the guy typed "Michael", clicked on the name that came up, and hit send. He didn't notice that it autofilled the name "Michael Brown" from the Asian Football Cup organising committe rather than, say, "Michael Smith" the internal employee who was supposed to update the approved official visitor database.

Comment: Re:Don't know if what you say is true ... (Score 1) 136

by stoborrobots (#49178241) Attached to: Photo First: Light Captured As Both Particle and Wave

I don't think the term is quite that bad, but the way we talk about it is. That said, my choice to use the term "puff" was specifically to avoid any pre-conceived notions about the duality.

The term "wave-particle duality" was coined because we can imagine waves, and we can imagine particles, and when we realised that we couldn't force light and electrons to be one or the other, that they must be, in some sense "both".

The term is not wave particle alternation, conversion, collapse, or any thing which implies that it is sometimes one and sometimes the other. However, the elementary examples we give people learning about QM might mislead people to believe that.

The "duality" is expressed specifically to indicate that it has both aspects at all times.

Comment: Re:not the first time (Score 1) 136

by stoborrobots (#49177183) Attached to: Photo First: Light Captured As Both Particle and Wave

Close - you're mixing up the wavefunction of a puff of light with the wave-like nature of a puff of light.

The wavefunction gives you the probability distribution of any properties you want to measure.

The wave-like nature is what gives it colour and allows diffraction.

But the wave-like properties (wavelength, etc) are not the properties of it's position wavefunction.

You make reference to the electron double-slit experiment. It's tempting to think that electrons are particles - except that they're not. The fact that they exhibit the same "particle-wave duality" indicates that they too are "puffs" of matter, not particles, not waves, but something with properties of both.

There are no particles at quantum scale. Particles only exist at human scales. The struggle comes in accepting that the thing we are talking about is not analgous to any specific thing in our experience. It's convenient to talk about particles, and waves, because we can conceive of what they are. We imagine that particles are like incredibly small billiard balls, and waves are like ripples on a pond and that light is sometimes one and sometimes the other - because we can imagine these things. But puffs of light and puffs of matter don't behave like tiny billiard balls or tiny ripples - they behave like a combination of them. You can simultaneously measure both wave-like and particle-like behaviour.

Comment: Re:not the first time (Score 5, Informative) 136

by stoborrobots (#49167423) Attached to: Photo First: Light Captured As Both Particle and Wave

The wave-particle duality is not a quantum superposition like you're describing (which would break down under measurement), although the caricatured manner in which we teach it might lead you believe that. It's a little more simple than that.

In our world, we are used to two kinds of things: particles, and waves. We are used to this distinction, and describe most things in one of these manners. Sound is a wave, a billiard ball is a particle, vibrations are waves, bricks are particles. If something is a particle, it has certain properties, like position, size, and shape. If it is a wave, it has certain other properties like wavelength, frequency, and amplitude. In addition, there are some common properties like velocity and direction.

When it came to studying light (and many other quantum stuffs), we can't directly see what it's made of. But we can take measurements of each "puff" of light, and infer its properties that way. When we do this, we notice that puffs of light have some properties which are particle-like, and some which are wave-like. So the term "particle-wave duality" became popular to describe this new material that was behaving simultaneously like a particle and a wave. It doesn't make sense to ask which one it is - a "puff" of light is neither a particle, nor a wave, but a different kind of stuff which has some properties of each.

The greatest productive force is human selfishness. -- Robert Heinlein