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Note from micronesia: please read the thread before making comments about how we have just turned physics on its head. |
On January 06 2013 01:54 The_Masked_Shrimp wrote:
I am a grad physics student and even with that i found that article quite blur.
I really don't understand how some of you can debate about what's told in that article with statements as confidents and "clear" .
One has to be really cautious with signs and their interpretation in physics equations. In particle physics you can encounter something which looks like particles with negative energy going backward in time when it's antiparticles with positive energy going forward in time.
There are also a lot of understanding problems because people don't talk about the same things because they don't use the same definitions.
So just an advice when you read articles like these, don't take it for granted.
And Solarsail, speed of light and absolute zero are fixed in the framework of the THEORY we built to describe what we see. One could build a theory where these are not fixed even if it might take complicated tricks or "laws" to match the observations back.
Read the paper. It's much simpler than reading the attempt at explaining thermodynamics to the layman that is that article.
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But wouldn't this mean that the absolute zero (wich we thought it would be) isn't the absolute zero?
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God dammit, just waiting for Half Life to happen! xD
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Times like these when think back to when it was preposterous to think the earth was anything but flat. A year ago scientists would have clung on to the idea of absolute zero for dear life, now this. No Science is absolute!
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But wouldn't this mean that the absolute zero (wich we thought it would be) isn't the absolute zero?
Well as far as i understand the confusion comes from the different definitions of temperature that are going on here.
As far as most people understand temperature and what the term absolut zero refers to , is a state in which particles don't move at all. They have no kinetic energy left over, and you can't possibly go below that.
But the temperature definition of thermodynamics is a little bit different. It's not so much about kinetic energy, but about entropy and energy. If you raise the temperature of a a system, what it means is that energy and entropy increase
But in this special case, scientists actually lowered the entropy while rising the energy, by "trapping" the particles.
This changes the behaviour of such a system drastically, (which also by the way proves that is isn't just a redefinition of terms) and means that although you put energy into it, it still got colder, and even an object with a higher temperature will still get energy from the "below-zero" system.
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On January 06 2013 00:43 emythrel wrote:
a few billionths below aboluste zero? phew. For a second i thought we had again discovered that we were completely wrong about the universe. While a few billionths is a massive deal, its not like they managed to go a whole degree below or further, which would mean a complete re-write of some major components of modern physics.
It doesn't matter how much below absolute zero they achieved, more the fact that it was achieved with this artificial gas.
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Russian Federation748 Posts
There's an excellent example with magnetic dipoles in a magnetic field to explain negative temperatures. I don't remember it exactly now sadly.
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United States24666 Posts
On January 06 2013 02:59 Evangelist wrote:Show nested quote +On January 06 2013 01:13 micronesia wrote:
I want to point out that saying entropy is the disorder of a system is about as accurate as saying temperature is the speed of molecules in a system. Thermal physics is difficult to discuss without studying it. No, entropy is pretty much the disorder in a system when you define order as having structure. That's about all you really need to know at the quantum mechanical level, certainly enough to understand how this works.
You yourself had to say 'pretty much' which is the same thing as how temperature is 'pretty much' the average kinetic energy of the molecules.
There is nothing wrong with thinking of entropy has the disorder of a system if you are willing to acknowledge that it is not technically accurate.... but it will get you into trouble sometimes.
On January 06 2013 05:24 Kyrillion wrote:
There's an excellent example with magnetic dipoles in a magnetic field to explain negative temperatures. I don't remember it exactly now sadly.
I did mention this earlier in the thread, although it's tricky to explain fully for those who aren't already studying it...
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On January 06 2013 02:55 Reason wrote:
^Lol.
So.. to clarify this for the layman.
Supposing my finger was a perfect measure of how hot or cold something was and was capable of feeling any temperature without being permenantly damaged, and ignoring the changes caused by me sticking my fingers in there and any other sort of technical details:
If I touched something that was the coldest we've "achieved" previously, which I understand is slightly above absolute zero,
It would feel very cold.
If I touched something that was actually absolute zero,
It would feel slightly colder.
If I touched this new "negative temperature"...
It would feel even colder still?
I'm still unsure as to whether they've actually created something at a temperature colder than what we previously understood to be absolute zero or if due to technical definitions of what temperature actually means this has to be a "negative" temperature or a temperature "below" absolute zero.
No, it would feel extremely hot.
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So much misleading information about this finding. This is a much better explanation of what's going on, written by someone who actually understands it and isn't trying to mislead people for page views.
A TLDR summary by the scientists who did the experiment:
The gas is not colder than zero Kelvin, but hotter. It is even hotter than at any positive temperature – the temperature scale simply does not end at infinity, but jumps to negative values instead.
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I was completely wtf reading the article at first. But when some of you described it in terms of entropy it makes sense now.
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On January 06 2013 03:26 Soulstice wrote:
Times like these when think back to when it was preposterous to think the earth was anything but flat. A year ago scientists would have clung on to the idea of absolute zero for dear life, now this. No Science is absolute!
Was there really any time it was controversial to point out that the Earth is round, though?
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On January 06 2013 05:56 corpuscle wrote: So much misleading information about this finding. This is a much better explanation of what's going on, written by someone who actually understands it and isn't trying to mislead people for page views. A TLDR summary by the scientists who did the experiment: Show nested quote +The gas is not colder than zero Kelvin, but hotter. It is even hotter than at any positive temperature – the temperature scale simply does not end at infinity, but jumps to negative values instead.
So wait, we can think of the scale as a circle?
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What I'm curious is the effects of this reversal of entropy. Take for example a carnot engine, if we have applications like this won't we theoretically be able to increase the efficiency of said system?
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On January 06 2013 06:12 AXygnus wrote:Show nested quote +On January 06 2013 05:56 corpuscle wrote: So much misleading information about this finding. This is a much better explanation of what's going on, written by someone who actually understands it and isn't trying to mislead people for page views. A TLDR summary by the scientists who did the experiment: The gas is not colder than zero Kelvin, but hotter. It is even hotter than at any positive temperature – the temperature scale simply does not end at infinity, but jumps to negative values instead. So wait, we can think of the scale as a circle?
Sort of, yeah. It's mostly just some weirdness with physicists trying to make the traditional idea of temperature coincide with what we later learned is actually going on.
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Russian Federation748 Posts
The traditional idea of temperature is very vague and not well-defined though. It was expected someone would find better one at some point. Imagine we're Greek mathematicians encountering irrational numbers.
Also, it's making me realize Aquarius Camus was just a noob.
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On January 06 2013 00:10 TheAmazombie wrote:Yeah, I read this yesterday, so it is not that they actually got "colder" than absolute zero, but only when defining temps by the laws of thermodynamics and entropy...it is still a really cool and interesting feat, but it is a bit misleading the way they are saying it is "colder than absolute zero." They actually pumped more energy into this and created a state where entropy decreased with more energy, which is opposite of what is supposed to happen. http://en.wikipedia.org/wiki/EntropyI am still very curious on what kinds of things they will still find and discover by this.
This is what I was looking for. That's how I understood it.
Not sure about all the implications this has though.
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United States24666 Posts
On January 06 2013 06:30 JOJOsc2news wrote:Show nested quote +On January 06 2013 00:10 TheAmazombie wrote:Yeah, I read this yesterday, so it is not that they actually got "colder" than absolute zero, but only when defining temps by the laws of thermodynamics and entropy...it is still a really cool and interesting feat, but it is a bit misleading the way they are saying it is "colder than absolute zero." They actually pumped more energy into this and created a state where entropy decreased with more energy, which is opposite of what is supposed to happen. http://en.wikipedia.org/wiki/EntropyI am still very curious on what kinds of things they will still find and discover by this. This is what I was looking for. That's how I understood it. Not sure about all the implications this has though.
The only advantage I can think of is that we won't need to turn young female children into magical girls anymore.
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EPT
