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| Yousuf Khan... |
 Posted: Mon Nov 02, 2009 5:03 pm |
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Although it's not mentioned in the article, there's also been a lot of
buzz recently about whether or not gamma rays coming from the vicinity
of the Milky Way's central bulge is an indication of Dark Matter
annihilations or just more mundane supernova emissions. I guess this
would tend to support the non-Dark Matter hypothesis, at least for other
galaxies.
Yousuf Khan
Gamma-Ray Mystery Traced to Star-Birth Frenzy | Wired Science | Wired.com
"Astronomers have for the first time traced gamma rays, the most
energetic form of light, to galaxies undergoing a frenzy of star birth.
The finding, which has revealed a new class of galactic gamma-ray
sources, is not unexpected. But it provides new hints about the origin
of many cosmic rays, the high-speed protons and other charged particles
of extraordinarily high energies that bombard Earth."
http://www.wired.com/wiredscience/2009/11/gamma-ray-mystery-traced-to-star-birth-frenzy/ |
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| tadchem... |
| Posted: Mon Nov 02, 2009 5:03 pm |
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On Nov 2, 5:03 pm, Yousuf Khan <bbb... at (no spam) spammenot.yahoo.com> wrote:
[quote]Although it's not mentioned in the article, there's also been a lot of
buzz recently about whether or not gamma rays coming from the vicinity
of the Milky Way's central bulge is an indication of Dark Matter
annihilations or just more mundane supernova emissions. I guess this
would tend to support the non-Dark Matter hypothesis, at least for other
galaxies.
Yousuf Khan
Gamma-Ray Mystery Traced to Star-Birth Frenzy | Wired Science | Wired.com
"Astronomers have for the first time traced gamma rays, the most
energetic form of light, to galaxies undergoing a frenzy of star birth.
The finding, which has revealed a new class of galactic gamma-ray
sources, is not unexpected. But it provides new hints about the origin
of many cosmic rays, the high-speed protons and other charged particles
of extraordinarily high energies that bombard Earth."http://www.wired.com/wiredscience/2009/11/gamma-ray-mystery-traced-to...
[/quote]
Viscous interactions of particles in a plasma require dissipation of
thermal energy as high-energy electromagnetic radiation.
Tom Davidson
Richmond, VA |
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| dlzc... |
| Posted: Mon Nov 02, 2009 5:03 pm |
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Dear tadchem:
On Nov 2, 5:44 pm, tadchem <tadc... at (no spam) comcast.net> wrote:
[quote]On Nov 2, 5:03 pm, Yousuf Khan <bbb... at (no spam) spammenot.yahoo.com> wrote:
Although it's not mentioned in the article, there's
also been a lot of buzz recently about whether or
not gamma rays coming from the vicinity of the
Milky Way's central bulge is an indication of Dark
Matter annihilations or just more mundane
supernova emissions. I guess this would tend to
support the non-Dark Matter hypothesis, at least
for other galaxies.
Gamma-Ray Mystery Traced to Star-Birth Frenzy
| Wired Science | Wired.com "Astronomers have
for the first time traced gamma rays, the most
energetic form of light, to galaxies undergoing a
frenzy of star birth. The finding, which has
revealed a new class of galactic gamma-ray
sources, is not unexpected. But it provides new
hints about the origin of many cosmic rays, the
high-speed protons and other charged particles
of extraordinarily high energies that bombard Earth.
snip link now broken by Google.Groups[/quote]
[quote]Viscous interactions of particles in a plasma require
dissipation of thermal energy as high-energy
electromagnetic radiation.
[/quote]
Dissipation along these lines?
http://en.wikipedia.org/wiki/Z_machine
David A. Smith
PS: Are you ever going to get to move back where there are real
winters? |
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| Sam Wormley... |
| Posted: Tue Nov 03, 2009 12:43 am |
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| Y.Porat... |
| Posted: Tue Nov 03, 2009 3:34 am |
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On Nov 3, 7:43 am, Sam Wormley <sworml... at (no spam) mchsi.com> wrote:
[quote]More:
Cosmic rays traced to centers of star birthhttp://www.sciencenews.org/view/generic/id/49015/title/Cosmic_rays_tr...
By detecting gamma rays, a new generation of telescopes bolsters theory that supernovas
are origin of some cosmic rays
[/quote]
------------------
here is a quote from your quote:
''however, because galactic magnetic fields bend the direction of
travel of all charged particles, including cosmic rays, preventing
astronomers "
end of quote
did they say that
galactic magnetic fields bend the direction of travel of all
particles
**including cosmic rays **
???
cosmic rays are photons ??
TIA
Y.Porat
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| dlzc... |
| Posted: Tue Nov 03, 2009 4:14 am |
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Dear Y.Porat:
On Nov 3, 6:34 am, "Y.Porat" <y.y.po... at (no spam) gmail.com> wrote:
....
[quote]did they say that
galactic magnetic fields bend the direction of travel
of all particles
**including cosmic rays **
???
cosmic rays are photons ??
[/quote]
No, cosmic rays are massive particles. The most energetic photon is
still called a gamma ray photon. The definitions changed around the
early 60's (or so), from the way it was presented in SciFi (E.E. "Doc"
Smith), to the way it is presented now.
We needed a name for very energetic massive particles, and since they
seemd to originate from the cosmos at large...
The magnetic fields obviously won't divert neutrons... only protons,
ions, and electrons. Electrons would probably still be called beta
radiation, even though from a cosmic origin, and would not be
detectable on Earth's surface because our atmosphere would block them.
David A. Smith |
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| Y.Porat... |
| Posted: Tue Nov 03, 2009 6:07 am |
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On Nov 3, 4:14 pm, dlzc <dl... at (no spam) cox.net> wrote:
[quote]Dear Y.Porat:
On Nov 3, 6:34 am, "Y.Porat" <y.y.po... at (no spam) gmail.com> wrote:
...
did they say that
galactic magnetic fields bend the direction of travel
of all particles
**including cosmic rays **
???
cosmic rays are photons ??
No, cosmic rays are massive particles. The most energetic photon is
still called a gamma ray photon. The definitions changed around the
early 60's (or so), from the way it was presented in SciFi (E.E. "Doc"
Smith), to the way it is presented now.
We needed a name for very energetic massive particles, and since they
seemd to originate from the cosmos at large...
The magnetic fields obviously won't divert neutrons... only protons,
ions, and electrons. Electrons would probably still be called beta
radiation, even though from a cosmic origin, and would not be
detectable on Earth's surface because our atmosphere would block them.
David A. Smith
[/quote]
------------
thanks
Y.P
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| Steve Willner... |
| Posted: Tue Nov 03, 2009 11:14 am |
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In article <3c4899d0-7e83-4dfd-bfe2-352b340b04ea at (no spam) r24g2000prf.googlegroups.com>,
dlzc <dlzc1 at (no spam) cox.net> writes:
[quote]No, cosmic rays are massive particles.
[/quote]
Mostly protons but some heavy nuclei. I don't think the definition
used in science has ever changed, but SF writers could have
misunderstood or been wrong. Of course it took a few years after
cosmic rays were discovered to figure out what they are.
--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123 swillner at (no spam) cfa.harvard.edu
Cambridge, MA 02138 USA |
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| dlzc... |
| Posted: Tue Nov 03, 2009 3:08 pm |
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Dear Steve Willner:
On Nov 3, 2:14 pm, will... at (no spam) cfa.harvard.edu (Steve Willner) wrote:
[quote]In article <3c4899d0-7e83-4dfd-bfe2-352b340b0... at (no spam) r24g2000prf.googlegroups..com>,
dlzc<dl... at (no spam) cox.net> writes:
No, cosmic rays are massive particles.
Mostly protons but some heavy nuclei. I don't think
the definition used in science has ever changed, but
SF writers could have misunderstood or been wrong.
[/quote]
No, Robert Millikan defined them as photons and scattered electrons.
http://en.wikipedia.org/wiki/Cosmic_ray#History
.... third paragraph.
[quote] Of course it took a few years after cosmic rays were
discovered to figure out what they are.
[/quote]
The word "ray" tells you the history, and they were expected to be
photons as well as more.
For Sam Wormley:
Most of the "missing normal matter" was found:
http://news.softpedia.com/news/Hubble-Finds-More-Missing-Matter-86104.shtml
.... and it also was hydrogen, with enough O^-5 salted in for detection
of the hydrogen. (Now that Hubble is back up, maybe they can see
more?)
But still the name is inclusive of any charged massive nucleus / ion
of extrasolar origin.
David A. Smith |
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| Sam Wormley... |
| Posted: Tue Nov 03, 2009 5:21 pm |
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Steve Willner wrote:
[quote]In article <3c4899d0-7e83-4dfd-bfe2-352b340b04ea at (no spam) r24g2000prf.googlegroups.com>,
dlzc <dlzc1 at (no spam) cox.net> writes:
No, cosmic rays are massive particles.
Mostly protons but some heavy nuclei.
[/quote]
Since the universe is mostly hydrogen.....
I don't think the definition
[quote]used in science has ever changed, but SF writers could have
misunderstood or been wrong. Of course it took a few years after
cosmic rays were discovered to figure out what they are.
[/quote] |
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| Sam Wormley... |
| Posted: Tue Nov 03, 2009 10:49 pm |
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dlzc wrote:
[quote]Dear Steve Willner:
On Nov 3, 2:14 pm, will... at (no spam) cfa.harvard.edu (Steve Willner) wrote:
In article <3c4899d0-7e83-4dfd-bfe2-352b340b0... at (no spam) r24g2000prf.googlegroups.com>,
dlzc<dl... at (no spam) cox.net> writes:
No, cosmic rays are massive particles.
Mostly protons but some heavy nuclei. I don't think
the definition used in science has ever changed, but
SF writers could have misunderstood or been wrong.
No, Robert Millikan defined them as photons and scattered electrons.
http://en.wikipedia.org/wiki/Cosmic_ray#History
... third paragraph.
Of course it took a few years after cosmic rays were
discovered to figure out what they are.
The word "ray" tells you the history, and they were expected to be
photons as well as more.
For Sam Wormley:
Most of the "missing normal matter" was found:
http://news.softpedia.com/news/Hubble-Finds-More-Missing-Matter-86104.shtml
... and it also was hydrogen, with enough O^-5 salted in for detection
of the hydrogen. (Now that Hubble is back up, maybe they can see
more?)
But still the name is inclusive of any charged massive nucleus / ion
of extrasolar origin.
David A. Smith
[/quote]
Thanks David.
-Sam |
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| Steve Willner... |
| Posted: Wed Nov 04, 2009 12:12 pm |
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In article <32343891-615b-4cea-8176-3c56890a62b7 at (no spam) p8g2000yqb.googlegroups.com>,
dlzc <dlzc1 at (no spam) cox.net> writes:
[quote]No, Robert Millikan defined them as photons and scattered electrons.
http://en.wikipedia.org/wiki/Cosmic_ray#History
... third paragraph.
[/quote]
What the paragraph actually says is "The term "cosmic rays" was
coined by Robert Millikan who proved they were extraterrestrial in
origin, and not produced by atmospheric electricity as Hess had
thought. Millikan believed that cosmic rays were high-energy photons
with some secondary electrons produced by Compton scattering of gamma
rays." Of course somebody (not me!) could have edited the page since
you read it.
The page goes on to say it took about a decade to figure out what
cosmic rays really are.
[quote]The word "ray" tells you the history, and they were expected to be
photons as well as more.
[/quote]
It tells you what one influential person guessed the evidence would
eventually show. He was wrong, but so what? Other influential
people (such as Compton, as the next sentence of the article says)
had a different guess. I'd be astonished if any of them believed any
of the guesses before the evidence was collected.
[quote]Most of the "missing normal matter" was found:
http://news.softpedia.com/news/Hubble-Finds-More-Missing-Matter-86104.shtml
[/quote]
This refers to _baryonic_ dark matter. The claim in the paper (2008
ApJ, 679, 194) is that about 40% of the baryonic dark matter in the
local Universe is in hot interstellar gas.
--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123 swillner at (no spam) cfa.harvard.edu
Cambridge, MA 02138 USA |
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| Odysseus... |
| Posted: Thu Nov 05, 2009 1:35 am |
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In article <hcsu7j$rnt$1 at (no spam) news.eternal-september.org>,
willner at (no spam) cfa.harvard.edu (Steve Willner) wrote:
[quote]In article <32343891-615b-4cea-8176-3c56890a62b7 at (no spam) p8g2000yqb.googlegroups.com>,
dlzc <dlzc1 at (no spam) cox.net> writes:
[/quote]
<snip>
[quote]The word "ray" tells you the history, and they were expected to be
photons as well as more.
It tells you what one influential person guessed the evidence would
eventually show. He was wrong, but so what? Other influential
people (such as Compton, as the next sentence of the article says)
had a different guess. I'd be astonished if any of them believed any
of the guesses before the evidence was collected.
[/quote]
At any rate there are plenty of 'misnomers' among scientific terms:
atoms aren't indivisible, oxygen is not essential for acidity, planetary
nebulae have nothing to do with planets, and so on. Sometimes things are
renamed as our understanding changes, but often historical usage
prevails, the term's original motivation losing significance for all
purposes except the etymological.
--
Odysseus |
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| Yousuf Khan... |
| Posted: Tue Nov 10, 2009 9:37 am |
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Steve Willner wrote:
[quote]In article <32343891-615b-4cea-8176-3c56890a62b7 at (no spam) p8g2000yqb.googlegroups.com>,
dlzc <dlzc1 at (no spam) cox.net> writes:
No, Robert Millikan defined them as photons and scattered electrons.
http://en.wikipedia.org/wiki/Cosmic_ray#History
... third paragraph.
What the paragraph actually says is "The term "cosmic rays" was
coined by Robert Millikan who proved they were extraterrestrial in
origin, and not produced by atmospheric electricity as Hess had
thought. Millikan believed that cosmic rays were high-energy photons
with some secondary electrons produced by Compton scattering of gamma
rays." Of course somebody (not me!) could have edited the page since
you read it.
[/quote]
Looks like gamma rays are produced by atmospheric lightening too these
days; even anti-matter in the form of positrons are produced by it.
http://tinyurl.com/ybo7hny
Yousuf Khan |
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