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| Watsisname | Date: Sunday, 30.10.2016, 21:38 | Message # 1051 |
 Galaxy Architect
Group: Global Moderators
United States
Messages: 2613
Status: Offline
| I found the edge of the world.
What's beyond that? Nobody knows.
Slowly I drift, into the void.
Swallowed by the endless mist.
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| powermoneywomen | Date: Saturday, 05.11.2016, 14:52 | Message # 1052 |
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Observer
Group: Newbies
Pirate
Messages: 1
Status: Offline
| http://www.powermoneywomen.com/sitephotos.html
See the second photo of the link i provided.....it was so weird that i had to share.....mars....is that another crab?
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| Alek | Date: Sunday, 06.11.2016, 08:08 | Message # 1054 |
 Pioneer
Group: Users
United States
Messages: 326
Status: Offline
| Quote Watsisname (  ) And how's this for counter-intuitive? The gap is horizontal!
Wait what? That is really weird...it shouldn't be possible for the light to re-arrange itself like that...
Living among the stars, I find my way. I grow in strength through knowledge of the space I occupy, until I become the ruler of my own interstellar empire of sorts. Though The world was made for the day, I was made for the night, and thus, the universe itself is within my destiny.
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| Watsisname | Date: Sunday, 06.11.2016, 13:00 | Message # 1055 |
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Galaxy Architect
Group: Global Moderators
United States
Messages: 2613
Status: Offline
| It is probably the least intuitive thing I know in all of physics.  It's like that because we're so used to light behaving like rays, going in straight lines, not canceling out with itself...
But here we are seeing the wave-like properties of light. Water waves actually provide a very good visual analogue for it:
Notice that with water waves as with light, the waves spread out more when the aperture is similar in size to the wavelength. It's useful to think of each point on the wave front as a source for a new spherical wave. Then the question is how do those new waves interfere with each other as they travel? Peaks meeting with with peaks make brightness. Peaks with troughs make darkness. Once we work through the geometry of it, it begins to make a bit more sense how the diffraction pattern forms. And yet, even with that understanding, to actually see it still strikes me as totally odd. Water waves are one thing, but it's hard to imagine light being like that.
We can also find the diffraction pattern produced by an aperture by taking the Fourier Transform of the aperture. The Fourier Transform is well known in signal analysis, but it also applies in 2D and even higher dimensions, and it has use in optics. Here's the transform of three rough-edged circles in a triangle pattern:
Pretty close to the diffraction pattern photographed.
And the transform for a horizontal slit:
Crudely drawn smiley face?
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| spacer | Date: Friday, 11.11.2016, 12:49 | Message # 1057 |
 Star Engineer
Group: Users
Israel
Messages: 1258
Status: Offline
| Watsisname, beautiful images. i like the mountains in the back too!
"we began as wanderers, and we are wanderers still"
-carl sagan
-space engine photographer
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| LookAtDatDakka | Date: Sunday, 13.11.2016, 00:13 | Message # 1058 |
 Explorer
Group: Users
United States
Messages: 156
Status: Offline
| Here what I would imagine Space Engine in the future:
Rendered in Blender 2.78 with noise addition
In other words, Watsisname, nice flocks of birds.
NVIDIA 960 GTX 2048MB
Edited by LookAtDatDakka - Sunday, 13.11.2016, 03:57 |
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| Hornblower | Date: Sunday, 13.11.2016, 00:40 | Message # 1059 |
 World Builder
Group: Users
United States
Messages: 714
Status: Offline
| LookAtDatDakka, That's what it looks like now! (actually looks better than it does in your picture, but nice render)
Edited by Hornblower - Sunday, 13.11.2016, 00:49 |
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| Alek | Date: Sunday, 13.11.2016, 03:29 | Message # 1060 |
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Pioneer
Group: Users
United States
Messages: 326
Status: Offline
| Quote LookAtDatDakka ( ) Rendered in Blender 2.78
Hm...could've mistaken it for a Grand Designer image with some after editing
Living among the stars, I find my way. I grow in strength through knowledge of the space I occupy, until I become the ruler of my own interstellar empire of sorts. Though The world was made for the day, I was made for the night, and thus, the universe itself is within my destiny.
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| midtskogen | Date: Sunday, 13.11.2016, 14:41 | Message # 1061 |
 Star Engineer
Group: Users
Norway
Messages: 1674
Status: Offline
| Today's NZ earthquake as recorded by my seismometer in Oslo 160 degrees (nearly 18000 km) away:
NIL DIFFICILE VOLENTI
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| Watsisname | Date: Sunday, 13.11.2016, 23:10 | Message # 1062 |
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Galaxy Architect
Group: Global Moderators
United States
Messages: 2613
Status: Offline
| Wow. 
For being 160° away from epicenter, I was curious what information about the Earth's inner structure are apparent in the recording. Here's an interesting graphic which lays it all out.
Your recording looks very consistent with it, showing a ~20 minute delay between the quake and the wave arrival. The first to arrive are pressure waves that passed through both the outer and inner core. Then there are waves that were refracted through the outer core, and then the pressure wave which was reflected once off the surface. I think that may be the spike you see at around 11:28. The rest are surface waves and further reflections. And there are no direct shear waves, since they can't pass through the liquid outer core.
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| midtskogen | Date: Sunday, 13.11.2016, 23:47 | Message # 1063 |
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Star Engineer
Group: Users
Norway
Messages: 1674
Status: Offline
| Yes, the striking feature of this plot is the lack of an S wave arrival. It would be interesting to convert this data to audio. Usually one hears two crashes followed by a rumble: P wave arrival, S wave arrival and surface waves. But this should be different. I'm in Korea right now, and accessing my usual tools for doing these kind of things is a bit trickier.
NIL DIFFICILE VOLENTI
Edited by midtskogen - Monday, 14.11.2016, 00:21 |
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| midtskogen | Date: Monday, 14.11.2016, 00:05 | Message # 1064 |
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Star Engineer
Group: Users
Norway
Messages: 1674
Status: Offline
| An attempt to convert to audio. One hour compressed to 5 seconds. The sound appears very soft to me, and no doubt the distance causes that. But I can barely hear the sound, which may be because my $200 laptop has lousy speakers.
Edit: My phone's speaker is better. There are two crashing sounds right in the beginning. The second could be an echo of some kind, since there will be no S wave (and the delay between them is two small for an S wave anyway). It's not one of the aftershocks either, as the first one large enough for clear detection occurred half an hour later. I can't really hear the surface waves, but the frequencies might be too low for my speakers, even when one hour is compressed to 5 seconds. My seismometer peak sensitivity is around 0.06 Hz, which gets turned to audio around 43 Hz and that is way too low for most speakers.
NIL DIFFICILE VOLENTI
Edited by midtskogen - Monday, 14.11.2016, 00:21 |
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| Watsisname | Date: Monday, 14.11.2016, 04:48 | Message # 1065 |
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Galaxy Architect
Group: Global Moderators
United States
Messages: 2613
Status: Offline
| That second crash seems to be the spike I was mentioning at about 11:28, which based on the graphic is probably the part of the P wave which moved through the mantle and reflected once off the surface before reaching you. At first I thought it surprising that it arrives so soon after the direct wave despite following a longer path, but after going through the math it does make sense.
If we consider a point antipodal to the quake, then the straight line through the Earth is about 12740km. 100km through the crust (both sides), 3900km through mantle, 6200 through the outer core, and 2540 through the inner core. The P-wave velocity changes through all of these, averaging about 7km/s through crust, 10.5km/s through mantle, 9km/s through outer core, and 11km/s through inner core. Then the time it takes to pass through the whole Earth is about 22 minutes.
For the singly-reflected P wave through the mantle, we can imagine (not quite accurately but close enough) that it goes on a straight line to a point 90° away and reflects from there to the antipodal point. This path length is sqrt(2) times the radius of the Earth, times 2, or about 18000km. Then assuming 10.5km/s average speed, it takes about 28 minutes to make that trip. This roughly agrees with the observed waves.
The first surface waves should have arrived somewhere around 40 minutes after the quake. There does seem to be an increase in intensity there, but a lot of other complicated reflections are also reaching you by that point as well.
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