Back from LA with Honorverse move news

[continuing the physics calculations]

The limit of detection with the naked eye is an apparent magnitude of 6, but I don't believe you could detect a momentary flash that faint. So let us suppose a detection limit of apparent magnitude 5. That means the explosion would have to be 20 magnitudes brighter, or 1.0e10 times brighter. To do that, we move the explosion 1.0e5 times closer. Absolute magnitude is the apparent magnitude at a distance of 10 parsecs, or 32.6 light-years. Dividing by 1.0e5, we see that the explosion will very briefly be apparent magnitude 5 at a distance of 2.8 light-hours. 10 times closer will be 5 magnitudes brighter (i.e. magnitude 0, as bright as Sirius).

Conclusion: a nuclear explosion 17 light-minutes away might be (very briefly) as bright as Sirius, and potentially visible much further. Very interesting!

Mitigating factors: I'm not sure how long a flash has to be before it is actually detected by the eye. The flash lasts longer than 100 microseconds, of course, but it decays rapidly. I'm not sure exactly how rapidly, and I'm not sure how to model the light-integration of the eye. So this is a big guesstimate here--I easily could be off by several magnitudes brightness.

The only reference I've seen to fireball expansion in deep space was 10,000 km/sec. Can't remember where that came from either.

OK, so apologies are in order for not remembering they were Idahoans (and that the US Midwest lies mostly to the east, obviously I should have written West).

Jerenswen's numbers aren't that far off what I wrote (and 27% of all births in 2011 were minorities, so the trend is towards racial diversity acct. the wiki), the exception is that the dominant minority isn't black.

Sidebar on the 3-D vs 2-D debate: I have no particular use for 3-D either, I will probably go catch this one in 3-D for my third showning, but the first couple of times I will not want that particular distraction.

... All of this presupposing the movie makes it to a theater in a country near me ... but a 3-D budget makes that more likely than a 2-D production would, these days, so I see 3-D as a good thing; not for the 3-D malarkey itself, but for the increased commitment to reach a larger audience (to wit: my countrymen and I) to make good the larger production cost.

Jeroswen wrote:

drothgery wrote:
hvb wrote: Grayson and Masada are US midwest, which would mean a large minority of blacks (~80% caucasian now, but by the time they form the colony effort that may well have declined somewhat), plus of course a bit of everything else.

Grayson is out of Idaho, which isn't US Midwest by any definition I've ever seen (and which is... umm... very, very white), though the only thing we know for sure is there are almost no ethnic east Asians ala Honor's Chou relatives.

I am from Idaho and the population is largely white. However we also have a very large hispanic population and a smaller representation of oriental and black populations. According to the last census we are 83.5% white, 11.5% hispanic, and then a sprinkling of the rest. The similarities I see between the Graysons and the people of this state are that both are very stubbornly self-reliant and conservative. Anyway we've kicked out the Neo-Nazi groups decades ago but its a scar we'll bare for a long time I'm afraid.

I just wanted to throw in my two cents since not many people know of this state.

Another important mitigator would be the level of light pollution at the location she is observing from.

If she is watching from somewhere close to the center of the Steading, her ability to see the flare of the detonations is likely to be significant impaired by skyglow.

For Bottle Scale class 1 conditions, defined as an "Excellent dark-sky site", the threshold for a continuous source goes as low as absolute magnitude of 8, if you have good eyes.

In classes 3 and 5, "rural sky" and "suburban sky" M goes down by one order of magnitude to 7 and then 6. A full moon (well, Luna anyway) reduces naked-eye visible M to 5, and inner city lights all the way down to M 4.0.

For a brief flash, as you write, M will be even lower.

SWM wrote:[continuing the physics calculations]

The limit of detection with the naked eye is an apparent magnitude of 6, but I don't believe you could detect a momentary flash that faint. So let us suppose a detection limit of apparent magnitude 5. That means the explosion would have to be 20 magnitudes brighter, or 1.0e10 times brighter. To do that, we move the explosion 1.0e5 times closer. Absolute magnitude is the apparent magnitude at a distance of 10 parsecs, or 32.6 light-years. Dividing by 1.0e5, we see that the explosion will very briefly be apparent magnitude 5 at a distance of 2.8 light-hours. 10 times closer will be 5 magnitudes brighter (i.e. magnitude 0, as bright as Sirius).

Conclusion: a nuclear explosion 17 light-minutes away might be (very briefly) as bright as Sirius, and potentially visible much further. Very interesting!

Mitigating factors: I'm not sure how long a flash has to be before it is actually detected by the eye. The flash lasts longer than 100 microseconds, of course, but it decays rapidly. I'm not sure exactly how rapidly, and I'm not sure how to model the light-integration of the eye. So this is a big guesstimate here--I easily could be off by several magnitudes brightness.

If I was running Grayson at the point I'd be going to a global blackout and getting people away from the major urban areas.

kzt wrote:If I was running Grayson at the point I'd be going to a global blackout and getting people away from the major urban areas.

Probably a bad idea on a planet like Grayson...

kzt wrote:The only reference I've seen to fireball expansion in deep space was 10,000 km/sec. Can't remember where that came from either.

The maximum gas expansion velocity is limited by the Yield Energy to Mass ratio of the nuclear device. The theoretical maximum for a fusion warhead is about 1/10 Megaton per Kg of bomb. This would yield a maximum gas expansion velocity of about 30,000 Km/s. The practical energy density is about 1/100 MT per Kg which would yield a gas expansion velocity of about 10,000 Km/ s.

Of course these calcs of gas expansion velocities are predicated on the premis that 100% of the energy goes into KE rather than radiation. Which definitely is not true.

Our local Astronomers offerred interesting approximations, but they presume that 100% of the energy is visible light. Depending on the mass to energy ratio of the weapon, most of the energy will go into Neutrons which aren't visible to the naked eye. Most of the thermal radiation
from the expanding plasma will be radiated as X-rays and UV which is also not visible to the naked eye.

runsforcelery wrote:
To the best of my knowledge, Evergreen has no connection with Cameron. Nor --- having seen samples of their work --- does Evergreen need the connection to do some incredible work.

Oh, okay.

I just read this part about a partnership with the Cameron Pace Group on their website and thought this may be a connection. ^^;

http://www.evergreenfilms.com/news/1109 ... ership.php

SWM wrote:[continuing the physics calculations]

The limit of detection with the naked eye is an apparent magnitude of 6, but I don't believe you could detect a momentary flash that faint. So let us suppose a detection limit of apparent magnitude 5. That means the explosion would have to be 20 magnitudes brighter, or 1.0e10 times brighter. To do that, we move the explosion 1.0e5 times closer. Absolute magnitude is the apparent magnitude at a distance of 10 parsecs, or 32.6 light-years. Dividing by 1.0e5, we see that the explosion will very briefly be apparent magnitude 5 at a distance of 2.8 light-hours. 10 times closer will be 5 magnitudes brighter (i.e. magnitude 0, as bright as Sirius).

Conclusion: a nuclear explosion 17 light-minutes away might be (very briefly) as bright as Sirius, and potentially visible much further. Very interesting!

Mitigating factors: I'm not sure how long a flash has to be before it is actually detected by the eye. The flash lasts longer than 100 microseconds, of course, but it decays rapidly. I'm not sure exactly how rapidly, and I'm not sure how to model the light-integration of the eye. So this is a big guesstimate here--I easily could be off by several magnitudes brightness.

In this case, the eye can be modeled by a camera. IIRC, the way it works is that the eye fixates on one point for a number of milliseconds, then it shifts to another point in a motion called a saccade, which lasts for a number of milliseconds. Effectively, the brain integrates a number of still pictures. This is why movies work - the brain is simply doing what it does naturally in integrating a series of stills. The fact that we see things moving smoothly is an illusion constructed by the brain's visual processing.

So if the flash occurs while the eye is fixated, it'll appear as a flash, while if it occurs during a saccade it'll be effectively invisible.

Psychologists that study vision exploit this in all kinds of amusing ways, using eye tracking gizmos and ultra-fast refresh screens that they can repaint while the eye is in motion and hence not recording what's happening. Fun.

Abigail is a rich princess in a future where even Grayson tech is in advance of our own.

There is a program for my iPad that tells me where to point it to find a planet or star or the ISS. And, when I point it in a particular direction, it identifies the objects in the field of view for me.

I imagine that Abigail might have access to a decent set of star gazing binoculars with similar technology.

Indeed. A Steadholder so inclined could probably afford a dedicated balcony with virtual displays that worked the same way. An interesting way to show the primitive Graysons in comparison to us.