OT: Falcon heavy rocket launch

Currently this is rescheduled for 20:45 tonight. Launch window closed at 21:00
Could be well worth a look.
https://arstechnica.com/science/2018/02/watch-live-spacexs-colossal-falcon-heavy-may-finally-fly-today/
Tim
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Battery powered? How much CO2 will it emit? :-)
Seriously though, I'll not miss it.
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Chris

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Truly remarkable! Whatever you might think of Musk, his batteries and his cars, that deserves a huge amount of praise.
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On 06/02/2018 20:58, Chris Hogg wrote:

There is nothing special about his batteries. he has identified a niche market for his cars.
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dennis@home wrote:

Plus he's pretty adept at tapping federal and state subsidies, grants and tax-breaks ...
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On 07/02/2018 12:29, Andy Burns wrote:

So he's a great businessman; but he must be pretty smart about all sorts of technology to have identified and developed all the different opportunities. And good at spotting bullshit.
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On Wed, 7 Feb 2018 12:29:08 +0000

<stanard answer for this group>
Yeah, an immigrant sucking up all the benefits he can get.
</saftg>
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But the end result is bloody good.
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On 06/02/2018 19:14, Chris Hogg wrote:

Impressive to have it all work OK first time and simultaneous landings.
Not as potent in sheer power and lift terms as the good old Saturn V but with the three boosters properly reusable a real step forwards.
Long way to go to collect your free used Tesla car though. "Don't Panic" screen was a nice touch as was "Life on Mars"...
You have to admire Elon Musk for his vision and making it happen.
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I assume that is gmt. Is this the one with an old sports car on the top to make up the weight? Brian
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On Tue, 6 Feb 2018 19:40:14 -0000

Yes, it's Elon Musk's version of Back to the Future.
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On Tue, 06 Feb 2018 19:41:39 +0000, Davey wrote:

That side core landing was just showing off!
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Actually (and you may know this already) it's the whole point of the exercise. In order to get to Mars in a reasonable time and land a decent payload, it's necessary to re-ignite a rocket engine facing into a trans-sonic flow and land under thrust. That's what they're learning how to do.
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On 07/02/2018 10:52, Huge wrote:

True, but it also makes sense if you want to corner the lucrative launch market.
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On Thu, 08 Feb 2018 08:06:43 +0000, Martin Brown wrote:

I'd have thought focussing your eyes to infinity would be easy seeing as how it's the result of relaxing the eye's focussing muscles used to accommodate for close in vision. Indeed, deep thought about a problem gives you that "Far Away Look", hence the word "consider" which literally translates as "to be with the stars".

That's almost twice as bright as Earth's albedo (39% back in 1976 when Vangelis released his space physics inspired concept album, "Albedo 0.39). Since Venus is closer to the sun, its brightness will be even higher than that simple albedo comparison suggests.
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On 08/02/2018 13:59, Johnny B Good wrote:

The problem is that to see a faint white speck against a bright blue sky background you have to have an exact focus. Try it and see. It is also quite easy to lose the thing even after you find it the first time.
Looking at a nearby con trail and transferring your gaze to the right spot often works. Seeing a dot is much harder than you might think.
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On 08/02/2018 13:59, Johnny B Good wrote:

Not quite correct. With nothing specific to focus on, the eye tends to settle at a couple of metres. All pilots are taught that lookout requires an active action of focussing on the horizon (and then breaking the scan into a series of segments where the eye is stationary, interspersed with re-focussing on the horizon). In the dark there's also the problem of the blind spot.
Many aero-med books discuss these but there are good articles here: https://www.airproxboard.org.uk/uploadedFiles/Content/Standard_content/Topical_Issues_and_Themes/02_Lookout.pdf http://www.cee.org/tep-lab-bench/pdf/BlindSpotActivity.pdf
... snipped
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On Thu, 08 Feb 2018 15:20:31 +0000, nothanks wrote:

Topical_Issues_and_Themes/02_Lookout.pdf

All very interesting. I guess the real problem with 'focussing' on far away point sources of light is more to do with convergence than with focussing per se. In dim night sky viewing, you need the use of both eyes to mitigate the dark blind spot problem making use of both eyes correctly converged an important requirement.
Eye convergence on distant objects can't be guaranteed by relaxation alone, usually requiring some active trimming by muscular control. Generally, in a sort of learned "Pavlonian" styled response, the lens focussing muscle response takes its cue from the amount of convergence we consciously 'dial in'.
I know from my experience with atropine drops that, my eyes lose all accommodation powers leaving them relaxed into a state of focus at infinity so I'm pretty sure that that bit about the eyes being in an individually relaxed state when looking into the far distance is correct and the corresponding convergence whilst not trimmed to precisely fixate on a particular far and distant object when in deep thought, is sufficient to give the outside observer, of another in deep thought, the impression of "gazing at the stars" or the far away horizon.
However, when it comes to observing the "Morning" or "Evening" star, namely Venus, that generally doesn't present any great difficulty with naked eye observation since it is both very bright and discernible as a tiny crescent, unlike the dimensionless points of light we call stars.
I have to admit that 'focussing on distance objects' relies not so much on relaxed focussing muscles so much as on correct convergence which almost always is a matter of some active muscle control and less about total relaxation which usually only approximates the precise convergence required for viewing distant objects. As you pointed out, my throw away observation wasn't quite correct, merely just a small part of the whole story.
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On 08/02/2018 17:37, Johnny B Good wrote:

Well, the correct name for the effect is "empty field myopia", which implies it is down to focus or, possibly, cognition. Muscles can only contract and when relaxed the ciliary muscle pulls the lens to its thinnest (longest focal length) condition ... so I can only surmise that either the ciliary muscle isn't fully relaxed in this state or there's summat else goin' on. I looked around for an explanation and stumbled over this google book, it doesn't have the answer but is a great thing to scan through: https://books.google.co.uk/books?id=UUAEAAAAMBAJ&pg=PA71
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On 08/02/2018 17:37, Johnny B Good wrote:

[snip]

For the avoidance of doubt I was talking about seeing Venus with the naked eye at or around midday in a clear blue sky with the sun well above the horizon. You need a good clear day and to stand in shadow.

The eye's default focus is as someone else has said is a few metres away from you if you have normal vision. You have to make an effort to bring the distant horizon into sharp focus assuming normal vision.
If you want a serious test of visual acuity try splitting the star epsilon-Lyra naked eye soon after dark it is a 3' arc double star - actually a double double in a small telescope it looks like:
.. :
with much bigger gap between then.
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