Catch up on stories from the past week (and beyond) at the Slashdot story archive


Forgot your password?
DEAL: For $25 - Add A Second Phone Number To Your Smartphone for life! Use promo code SLASHDOT25. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. Check out the new SourceForge HTML5 Internet speed test! ×

Comment Re:It's really a moot question (Score 1) 1027

GGP is correct that you could describe the motion of the planets (and sun) in terms of complicated orbits about the earth. However, as others have pointed out in the thread, there is a preferred (inertial) frame -- that of the fixed stars (cf. the Mach principle). The sun moves with respect to that frame, carrying the solar system with it. So the frame of the sun (or, more correctly, that of the center of mass of the solar system, which happens to pretty much be the sun) is objectively closer to being inertial than that of the earth. So to suggest that the reasons for favoring the sun as the origin of the system are purely technical (as opposed to physical) is perhaps a little disingenuous.

Comment Re:It seems off... (Score 4, Informative) 47

Well, at the time they came up with 0-k, they thought so as well, as that is the point that atomic motion stopped. Then they went and discovered that while atomic motion stopped at that temp, sub atomic motion did not. They went on further to discover that they could 'cool' things further and reduce/stop some of the sub-atomic motion. I think they have given up on a true absolute-zero at this point, and simply use it as an arbitrary point where one is needed.

This is really wrong. Temperature has a precise mathematical definition (relation between system energy and entropy), which is universal. Applied to most systems, this yields the concept of temperature familiar from everyday life. Indeed, some systems are such that they can be manipulated to a state of `negative temperature', in the formal mathematical sense. However it is definitely not the case that the concept of absolute zero is tied to the motion of atoms in particular, or that it is merely 'a reference point' that has later been surpassed.

(I kinda hope you're just trolling, otherwise please just STFU when you don't know WTF you're talking about. )

Comment Re:Lets just hope (Score 1) 47

Thinking about those lasers which are used to cool small particles to near zero temperatures. Can the photons from those lasers be considered to have a negative temperature, because of the energy they remove from the particles being cooled?

Not really... negative temperature can be a 'meaningful' concept in some scenarios, but it's not necessary to invoke it here. Temperature is a property of an object such that two objects in contact (or exchanging radiation, etc) with different temperatures will exchange energy (heat) so as to try and 'meet each other in the middle', i.e., hot one loses energy to the colder one until the the temperatures become equal. Basically the character of laser beams is that they are not-very-thermal-at-all, so you can think of the incident beam as having some temperature very close to absolute zero, much less than the particles they're being shone on. Statistically speaking, the temperature of the particles will lower towards that of the incident laser beam, and the scattered laser photons will be 'heated', and carry away some of the original thermal energy of the cooled particles.

Comment Re:Again? (Score 1) 145

No, it shows that bloggers and reporters (and slashdot editors) need to sensationalize preliminary results or possible explanations to get readers.

Of course they need to sensationalize. Otherwise these reports are just, well, preprints! And preprints that aren't in your field probably won't be of interest to you.

The arXiv blog is cool, and it's nice to see some interesting preprints from outside my field pointed out, but I only take this to mean that this could possibly be a bit more interesting to me than the other ten-thousand-odd astro-ph preprints I won't be reading this year.

Slashdot Top Deals

The amount of time between slipping on the peel and landing on the pavement is precisely 1 bananosecond.