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Festina Lente |
Just in case you needed to set your watch... Cosmic clocks: A Tight Radius - Velocity Relationship for HI-Selected Galaxies HI-Selected galaxies obey a linear relationship between their maximum detected radius Rmax and rotational velocity. This result covers measurements in the optical, ultraviolet, and HI emission in galaxies spanning a factor of 30 in size and velocity, from small dwarf irregulars to the largest spirals. Hence, galaxies behave as clocks, rotating once a Gyr at the very outskirts of their discs. Observations of a large optically-selected sample are consistent, implying this relationship is generic to disc galaxies in the low redshift Universe. A linear RV relationship is expected from simple models of galaxy formation and evolution. The total mass within Rmax has collapsed by a factor of 37 compared to the present mean density of the Universe. Adopting standard assumptions we find a mean halo spin parameter λ in the range 0.020 to 0.035. The dispersion in λ, 0.16 dex, is smaller than expected from simulations. This may be due to the biases in our selection of disc galaxies rather than all halos. The estimated mass densities of stars and atomic gas at Rmax are similar (∼ 0.5 M pc−2) indicating outer discs are highly evolved. The gas consumption and stellar population build time-scales are hundreds of Gyr, hence star formation is not driving the current evolution of outer discs. The estimated ratio between Rmax and disc scale length is consistent with long-standing predictions from monolithic collapse models. Hence, it remains unclear whether disc extent results from continual accretion, a rapid initial collapse, secular evolution or a combination thereof. http://s3-ap-southeast-2.amazo...mic-Clocks-Paper.pdf NRA Life Member - "Fear God and Dreadnaught" | ||
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The 2nd guarantees the 1st |
Does this finally explain why we switched to daylight saving time? *s* "Even if the world were perfect it wouldn't be." ... Yogi Berra | |||
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Tinker Sailor Soldier Pie |
Well duh. ~Alan Acta Non Verba NRA Life Member (Patron) God, Family, Guns, Country Men will fight and die to protect women... because women protect everything else. ~Andrew Klavan | |||
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| No ethanol! |
Wow, that is a... er... well over my head. Or does this explain slow Amazon shipping? ------------------ The plural of anecdote is not data. -Frank Kotsonis | |||
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A Grateful American |
It has something to do with the Toyota Corolla FX. "the meaning of life, is to give life meaning" ✡ Ani Yehudi אני יהודי Le'olam lo shuv לעולם לא שוב! | |||
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| Peace through superior firepower  |
Look up 'The Anthropic Principle' | |||
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| half-genius, half-wit |
See you around.... tac | |||
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| No double standards |
 I hadn't seen that before, it makes sense.A noted scientist once asked me "how much science was true 50 years ago that today we know is false -- and, how much science is considered true today that in 50 years we will know is false?" After the 1994 Northridge (CA) earthquake, the USGS acknowleded their seismic models re CA were wrong, the earth didn't do what it was supposed to do. A couple of years ago a science article noted that three deep space observation telescopes detected/recorded the same highly unexpected phenomenon out in the galaxy. They compared data and analysis, got the same results. The outcome was that if the speed of light can exceed the speed of light, everything fits, "but we are not going to go there". "Liberty lies in the hearts of men and women. When it dies there, no constitution, no law, no court can save it....While it lies there, it needs no constitution, no law, no court to save it" - Judge Learned Hand, May 1944 | |||
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Political Cynic |
I believe that Brian May did his PhD on radial velocities found in zodiacal dust in his spare time, he plays a bit of guitar [B] Against ALL enemies, foreign and DOMESTIC | |||
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E Plebmnista; Norcom, Forcom, Perfectumum. |
Now I know why I sometimes feel dizzy. ================================================ Ultron: "You're unbearably naive." Vision: "Well, I was born yesterday." | |||
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Member |
I had a 1963 Galaxy that would spin that fast, especially in the winter on the ice.  God's mercy: NOT getting what we deserve! God's grace: Getting what we DON'T deserve! "If the enemy is in range, so are you." - Infantry Journal Bob P239 40 S&W Endowment NRA Viet Nam '69-'70 | |||
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