Ask a physicist anything.

[Cabal]

What do you Physies want for Christmas, assuming anything and everything is possible?

A nice fluorescent or radioactive rock to add to my collection.

 

[Wiccan_Child]

Say what?

But absolute zero is when the molecules just stop moving completely, right? How can you have less movement than standing still?

Temperature is more than just a measure of molecular movement (a fast moving particle isn't necessarily hot, for instance). A more complete and general definition is that the temperature of a system is equal to the inverse of the rate of change of entropy with respect to internal energy:

In other words, temperature is defined in terms of entropy, then kinetic energy.

To briefly illustrate this, consider a collection of non-interacting charged particles in a magnetic field, which can have a spin of 'up' (thus pointing with the field) or 'down' (pointing against it). By adding more energy to the system, more and more are able to point down (because it's harder to point against the field). Eventually, you add so much energy that most are pointing down.
Now, because adding more energy will lower the entropy (the more than point in the same direction, the lower the entropy), and because temperature is defined as the rate of change of entropy with internal energy, this rate is actually negative: dS/dE < 0. Thus, temperature itself is also negative.

Does that make sense?

What do you Physies want for Christmas, assuming anything and everything is possible?

Anything & Everything ?
I'd like a TARDIS please.

I was going to say something witty, but pgp_protector took the words right out of mouth.

Now, do I want the Doctor's TARDIS, complete with David Tennant (not Matt Smith, thank you very much), or my own brand spanking new one? The Doctor's is an old fart of a machine, so I suppose it'd be like getting a landline instead of an iPhone...

A nice fluorescent or radioactive rock to add to my collection.

This might be of interest...

 

[Cabal]

Stop, you'll give me ideas!

I still have yet to get a UV fishtank and a big lead box and fill them with fluorescent and radioactive mineral samples respectively!

*twitch*

 

[TerranceL]

I've always wondered.... why is the top portion of that pic always empty?

 

[Chesterton]

I've always wondered.... why is the top portion of that pic always empty?

Because they wanted to leave room for the components of dark matter, dark energy and dark time.

(Oh sorry, you weren't supposed to hear about dark time yet. )

 

[Wiccan_Child]

Stop, you'll give me ideas!

I still have yet to get a UV fishtank and a big lead box and fill them with fluorescent and radioactive mineral samples respectively!

*twitch*

I've got it: genetically modified, chemiluminescent fish!

Not bio, but chemo!

 

[Wiccan_Child]

I've always wondered.... why is the top portion of that pic always empty?

Because the number of elements in row X is determined by how many electrons can fit into the Xth shell.

There are a maximum of two electrons in the first shell, so there are two elements in the first row. The one-electron element, Hydrogen, sits opposite the two-electron element, Helium.

The next few row contain eight elements, because shells #2 and #3 both contain eight electrons.

So the top part of the table is empty because the elements are organised by their electron configuration (the number of electrons in your highest shell determines your column number, and the number of occupied shells determines your row number).

There are precise rules for determining how many electrons can go in any particular shell, and the order in which new electrons fill up atomic shells (it's not a simple case of filling up the bottommost shell, then moving one up), but that's basically why.

There are other chemical tables that organise things differently. This one is the chemical galaxy:

I like the isotope table, which is basically a massive grid with atoms organised by proton and neutron numbers:

Because they wanted to leave room for the components of dark matter, dark energy and dark time.

(Oh sorry, you weren't supposed to hear about dark time yet. )

Shh! Doveaman will have a fit!

 

[Chesterton]

I've got it: genetically modified, chemiluminescent fish!

Would you pair that with a genetically modified, chemiluminescent Sauvignon blanc?

 

[Wiccan_Child]

Would you pair that with a genetically modified, chemiluminescent Sauvignon blanc?

I would, till I drank it like the alcoholic I am .

 

[pgp_protector]

Because they wanted to leave room for the components of dark matter, dark energy and dark time.

(Oh sorry, you weren't supposed to hear about dark time yet. )

Shh! Doveaman will have a fit!

What about Imaginary{sqr(-1)} time

 

[Wiccan_Child]

What about Imaginary{sqr(-1)} time

Just because I enjoying blowing people's minds... the imaginary unit isn't actually equal to the square root of minus one.

EDIT: it's also not equal to the negative square root of minus one. In case you get clever haha

 

[IzzyPop]

Just because I enjoying blowing people's minds... the imaginary unit isn't actually equal to the square root of minus one.

EDIT: it's also not equal to the negative square root of minus one. In case you get clever haha

Then what is i?

 

[Wiccan_Child]

Then what is i?

The imaginary unit. It's defined as:

i[sup]2[/sup] = -1

We can't say i = root(-1) because the square root function isn't defined for negative numbers. It's a technicality really, but I'll be damned if my mathematics gets sloppy!

 

[IzzyPop]

The imaginary unit. It's defined as:

i[sup]2[/sup] = -1

We can't say i = root(-1) because the square root function isn't defined for negative numbers. It's a technicality really, but I'll be damned if my mathematics gets sloppy!

I get it. Surprising really, since my calculus class was first thing in the morning. Trying to wrap my mind around such subjects while still trying to purge the remaining alcohol out of my system made for some stellar headaches.

 

[Wiccan_Child]

I get it. Surprising really, since my calculus class was first thing in the morning. Trying to wrap my mind around such subjects while still trying to purge the remaining alcohol out of my system made for some stellar headaches.

Ah, those where the days. Going through the virial theorem whilst fearing what abominable pictures will appear on Facebook when I get home...

 

[pgp_protector]

The imaginary unit. It's defined as:

i[sup]2[/sup] = -1

We can't say i = root(-1) because the square root function isn't defined for negative numbers. It's a technicality really, but I'll be damned if my mathematics gets sloppy!

I'm a coder, I can handle sloppy

 

[Wiccan_Child]

I'm a coder, I can handle sloppy

Several scientists were asked to prove that all odd integers higher than 2 are prime.

• Mathematician: "3 is a prime, 5 is a prime, 7 is a prime, and by induction - every odd integer higher than 2 is a prime."
• Physicist: "3 is a prime, 5 is a prime, 7 is a prime, 9 is an experimental error, 11 is a prime..."
• Engineer: "3 is a prime, 5 is a prime, 7 is a prime, 9 is an approximation to a prime, 11 is a prime,... "
• Programmer (reading the output on the screen): "3 is a prime, 3 is a prime, 3 a is prime, 3 is a prime.... "
• Second programmer: "Wait a minute, I think I have an algorithm from Knuth on finding prime numbers... just a little bit longer, I've found the last bug... no, that's not it... ya know, I think there may be a compiler bug here - oh, did you want IEEE-998.0334 rounding or not? - was that in the spec? - hold on, I've almost got it - I was up all night working on this program, ya know... now if management would just get me that new workstation that just came out, I'd be done by now..."

 

[pgp_protector]

Question.
Why do I get more coding done when working from home then when working at work?

 

[Wiccan_Child]

Question.
Why do I get more coding done when working from home then when working at work?

Relaxing, safe, and comforting environment, many distractions to stop your brain from melting, and no boss to stress you out! Plus you can do it for pleasure's sake, not for work's sake.

 

[Doveaman]

Because they wanted to leave room for the components of dark matter, dark energy and dark time.

(Oh sorry, you weren't supposed to hear about dark time yet. )

Shh! Doveaman will have a fit!