Asteroidboy wrote:Why is the Top Quark (172,000 MeV) "smaller" than an Up Quark (2.4 MeV)? Is there any such thing as 'density' at these scales?
spatrick wrote:Asteroidboy wrote:
Why is the Top Quark (172,000 MeV) "smaller" than an Up Quark (2.4 MeV)? Is there any such thing as 'density' at these scales?
Yeah, I'm a bit confused by what the authors' intention might be there, as well. In fact, I'm suspicious of everything below the scale 10^-16m, where they say "Lengths shorter that this this are not confirmed". Unless my quick math is wrong, that's only about 12 GeV, and we've been making precision measurements well past that for decades. They describe the Weak interaction as "unmeasurable" and give its length scale as something close to the Higgs's Compton wavelength. (Incidentally, that's the real current limit on measured scales.) Again, the Weak length scale has been measured for decades, and its scale (the W/Z Compton wavelength) is about 10 times larger than what's given. And, what are they trying to express by giving a "size" to the quarks and neutrinos? In the models describing these objects that are best tested by experiment, quarks and neutrinos interact as structureless point (sizeless) objects. The neutrinos are described as being "larger" at high energy than on average, which makes me think maybe they are taking the square root of the total scattering cross section as somehow being the size of the object. Those numbers actually work out roughly correctly to what the authors have given. But the quark sizes? They seem to scale inversely as the quark mass, again suggesting a Compton wavelength. But, if so, then the quarks are being shown as 10^4 or 10^5 "smaller" than they ought to be. Quark total cross sections are a little tricky to pin down, but trying to interpret the lengths here as square roots of cross sections doesn't get anywhere near the right order of magnitude. Maybe they are observational upper bounds on quark sizes? Nope, that's back at the "limit of measured scales". So... the subnuclear world in this presentation seems like a bit of a mess. Well, the Planck length stuff is OK.
One element of this presentation puzzles me. At the one nanometer scale, a single hydrogen atom is shown side-by-side with a water molecule, but the hydrogen atoms in the molecule are clearly smaller than the isolated atom. Is this a design oversight in the presentation, or is there some physical phenomenon of which I'm not aware that causes the electron shells in the hydrogen atom to compress when they're shared with the adjacent oxygen atom?
Amazin wrote:There is a proposal that remote galaxy clusters - retreating in their space at many times faster than the speed of light - can be detected by searching for their greatly blue-shifted light, as "the amplitude is not degraded", a scientist explained.
Right, but - wrote:- space extends with distance, but there is no clean break anywhere in it. It simply extends, so the light is conveyed smoothly from one extending phase of distance to the next, which duly conducts it 'at the speed of light'. For the receiving observer said light is progressively 'red-shifted'. But go far enough, and the red-shift will become null and then reverse to become progressively more and more blue-shifted. Well, that was how a scientst explained it to me...
... and that 'the signal's amplitude is not degraded'.
Mike Tilley wrote:At 10^10.1 what is the strangely named "Total Human Height" marker supposed to represent? It's about the same size as the star Pollux.
It represents what would be the total distance if you took every human alive (approximate average height times number of living humans) and layed them, end to end, in a single straight line.Mike Tilley wrote:At 10^10.1 what is the strangely named "Total Human Height" marker supposed to represent? It's about the same size as the star Pollux.
BMAONE23 wrote:. . . you could take all the people currently alive and stand them on the big island of Hawaii with room to spare
BMAONE23 wrote:you could take all the people currently alive and stand them on the big island of Hawaii with room to spare
geckzilla wrote:BMAONE23 wrote:. . . you could take all the people currently alive and stand them on the big island of Hawaii with room to spare
Using what measurements?
I'd just volunteer for one of the 4 foot squares above the caldera on that day...
<<[Volcano Nebula] galactic dust cloud over the Milk Way Galaxy; seen because of the star shine of most red and blue stars giving it color. Taken with Epsilon 160 F/3.3 astrograph using the SBIG STL-6303 XE CCD Camera; 6-hour exposure; taken in the dark skies over New Mexico. (Image published in Astronomy Magazine, September 2007 Issue.)>>
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