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The "Exposing PseudoAstronomy" Podcast

Started by astroguy, January 04, 2013, 12:51:45 AM

Quote from: astroguy on April 23, 2017, 09:04:49 PM
I have not heard anything about this.

i think a glancing blow was predicted from late last weeks cme. it seems to have been a bit more direct with brilliant, very active aurora seen from the upper states in the USA and the same in NZ. the density of the cme seemed much higher than what was predicted when it impacted the earth, crossing well with in satellite orbital paths. i don't know of any communication breakdowns.
just noticed nothing had been mentioned on the bellgab and thought i'd ask.

Quote from: Evil Twin Of Zen on April 23, 2017, 09:13:43 PM
it's right above this post. really it is and you can still read it without it being in a neat and tidy quote box here. right?

actually more interesting than world ending. the sun has been rather boring for several years.

April 22, 2017 @ 08:40 UTC - Geomagnetic Storm Warning (UPDATED)
QuoteA moderate (G2) geomagnetic storm is currently in progress thanks to a high speed solar wind stream above 700 km/s. More storming is expected over the next several days as a coronal hole stream rattles our geomagnetic field. Sky watchers at middle to high latitudes should be alert for visible aurora during the next several nights.ALERT: Geomagnetic K-index of 6
Threshold Reached: 2017 Apr 22 0559 UTC
Synoptic Period: 0300-0600 UTC
Active Warning: Yes
NOAA Scale: G2 â€" Moderate



edit-- i am unaware of the strength of the earth's magnetic field at the present time.

http://www.youtube.com/watch?v=rO1Fr3SQ7Mw

GravitySucks

Astroguy,

Seems me like I have read an article or two in the past, but I was wondering if you have a podcast on this subect:

Why do most impact craters appear to be circular, when probability would seem to dictate that many impacts occur at an angle to the surface instead of perpendicular.

Probably seems intuitive to you, based on all of the impacts you have analyzed, but it is something that always makes me wonder. Why don't we see more elongated "trenches" dug out by impacts that of an anyle other than 90 degrees?

Are there any planets/moons/asteroids that you have studied that differed significantly from the norm? If so, what is the difference attributed to?

astroguy

Quote from: GravitySucks on April 29, 2017, 01:52:54 PM
Astroguy,

Seems me like I have read an article or two in the past, but I was wondering if you have a podcast on this subect:

Why do most impact craters appear to be circular, when probability would seem to dictate that many impacts occur at an angle to the surface instead of perpendicular.

Probably seems intuitive to you, based on all of the impacts you have analyzed, but it is something that always makes me wonder. Why don't we see more elongated "trenches" dug out by impacts that of an anyle other than 90 degrees?

Are there any planets/moons/asteroids that you have studied that differed significantly from the norm? If so, what is the difference attributed to?
Impact craters form from hypervelocity impacts, where when the impactor strikes, it's moving faster than it and the ground can react: Sound speed.  Sound speed isn't just how fast sound travels, it's how fast each adjacent molecule in a material can move to let the ones next to it that something has happened.  That means that your intuition about what "should" happen goes away.  In a hypervelocity impact, almost nothing matters except for the total kinetic energy of the impactor.  Direction doesn't matter -- it would in a non-hypervelocity impact.

You start to see elliptical craters when the impactor hits a <5-10° relative to the surface.  Everything else being equal, that's only about 5-10% of the time (rounding).  And observations roughly match this.

GravitySucks

Quote from: astroguy on April 29, 2017, 03:26:01 PM
Impact craters form from hypervelocity impacts, where when the impactor strikes, it's moving faster than it and the ground can react: Sound speed.  Sound speed isn't just how fast sound travels, it's how fast each adjacent molecule in a material can move to let the ones next to it that something has happened.  That means that your intuition about what "should" happen goes away.  In a hypervelocity impact, almost nothing matters except for the total kinetic energy of the impactor.  Direction doesn't matter -- it would in a non-hypervelocity impact.

You start to see elliptical craters when the impactor hits a <5-10° relative to the surface.  Everything else being equal, that's only about 5-10% of the time (rounding).  And observations roughly match this.

That's what sucks about physics. As soon as you think you figured something out, it doesn't apply because it is not applicable to things that really small, really big, really cold or really fast.

So I guess what you are saying about s that the impactor "explodes" upon making contact leaving a circular crater.

It would be really cool to see som high speed film of an actual impact on the moon. Do you want to u know if any exist? It have seen one photo if I remember correctly of a plume coming off the surface but never a video.

Robert

Quote from: astroguy on April 29, 2017, 03:26:01 PMImpact craters form from hypervelocity impacts, where when the impactor strikes, it's moving faster than it and the ground can react: Sound speed.  Sound speed isn't just how fast sound travels, it's how fast each adjacent molecule in a material can move to let the ones next to it that something has happened.  That means that your intuition about what "should" happen goes away.  In a hypervelocity impact, almost nothing matters except for the total kinetic energy of the impactor.  Direction doesn't matter -- it would in a non-hypervelocity impact.
It's like when people see JFK's head on film jerk backward from an ostensible gunshot, they think it must've been from a shot in front, to conserve momentum, when actually the chief effect of the bullet is to pressurize the skull contents, which pressure is relieved mostly thru the biggest opening, the exit wound.  So the main thing here is the pressure xmitted to the ground by the impact, which tries to relieve itself isotropically.

astroguy

Quote from: GravitySucks on April 29, 2017, 03:38:25 PM
It would be really cool to see som high speed film of an actual impact on the moon. Do you want to u know if any exist? It have seen one photo if I remember correctly of a plume coming off the surface but never a video.
Only a planned experiment.  There've been two: Deep Impact (on a comet) and LCROSS (Moon).

GravitySucks

Quote from: astroguy on April 29, 2017, 04:42:26 PM
Only a planned experiment.  There've been two: Deep Impact (on a comet) and LCROSS (Moon).

Thanks. I have seen those two when they occurred. Deep Impact was cool. Like shooting a 30.06 bullet with a pellet gun.

Neither of those two were hypervelocity though were they? 

I bet somewhere there are some cool videos locked away from testing kinetic weapons in the SDI days.

astroguy

Quote from: GravitySucks on April 29, 2017, 04:47:34 PM
Thanks. I have seen those two when they occurred. Deep Impact was cool. Like shooting a 30.06 bullet with a pellet gun.

Neither of those two were hypervelocity though were they? 

I bet somewhere there are some cool videos locked away from testing kinetic weapons in the SDI days.
I don't know what the speeds of those were, other than "fast."  There are plenty of videos of hypervelocity experiments on Earth, though, from the Ames Vertical Research Gun. For example, first link on Google:

yousetubes


Ciardelo

Hey there asto. Are you about to resume some shows?

astroguy

Quote from: Ciardelo on August 19, 2017, 02:02:01 AM
Hey there asto. Are you about to resume some shows?
Hoping for September 01.  I have been out of town pretty much literally one out of every 4 days this summer, and my usual busy with work.


I recently discovered your most excellent shows and really enjoy them. I love how you scientifically shine a bright 'ol spotlight into the dark world of the paranormal hucksters. Bravo sir!

astroguy

Quote from: Radio Activity on September 01, 2017, 04:23:16 PM
I recently discovered your most excellent shows and really enjoy them. I love how you scientifically shine a bright 'ol spotlight into the dark world of the paranormal hucksters. Bravo sir!
Thanks!

Ciardelo

Quote from: astroguy on September 01, 2017, 04:17:05 PM
Solar Eclipses:
Even in the modern day,
Lunacy exists.

Episode 163, "Modern Eclipse Lunacy, Part 1," has been posted.
Quote...you should never under-estimate humans' capacity to be stupid...
Thanks! Welcome back!



Jackstar

QuoteI think this is a case where David is right in his latest article that he never said what people are claiming he claimed, and that he really did just say that September 23, 2017, was going to be a sign of what was to come.

I'm surprised. [...] This isn't the wrap-up I thought it would be, I even had a zinger prepared to end on,


Just wait until you find out who killed JFK.


Swishypants

Quote from: Evil Twin Of Zen on April 23, 2017, 09:28:07 PM


http://www.youtube.com/watch?v=rO1Fr3SQ7Mw

Sounds like Rusted Root got a Gig again! "I queefed Corn Beef! Livin' in a wold of Ex-Stasi! Where're you?"

I finally made it to the episode 100 parodies. Hilarious! Well done, Stan.  8)


astroguy

Quote from: Radio Activity on October 15, 2017, 12:05:27 PM
I finally made it to the episode 100 parodies. Hilarious! Well done, Stan.  8)
Thank you, I try.





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