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Ashish Joshi
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This is awesome! Can spend hours on it!
Caution: This can seriously bring down your productivity!

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My Own Moment

This is really me, alone with the shuttle Endeavour and the Shuttle Carrier Aircraft, Thursday afternoon at NASA Dryden.

I almost never want to be in photos.  Throughout our #nasasocial  event, everyone else would get their pictures taken, alone and in groups, still and jumping, with every aircraft, logo or souvenir, but I haven't even looked at the group photos (most are on Twitter).  But this moment made me hand someone my camera (bad of me, but I was too excited to even remember exactly to whom), and run to be alone for a final moment with the Endeavour.

We had just come away from visiting inside the SCA, and when we came out, the media were all gone, families all gone, and they had taken away the ropes and barriers.  I've scoured this photo, and there is definitely one other person and perhaps at most hints of two more, but they certainly didn't disturb my solitude.  I've followed the space program all my life, and the shuttle was the centerpiece of human exploration of space for two thirds of my life.  I believe that to move beyond this lone planet must be in the future of humankind; I'm excited about that future, but this also feels to me like the loss of a close friend.

This visit was absolutely a dream for me, and I'm so grateful to +NASA and their Social Media team led for this event by +john yembrick and Lisa Mattox (on G+?) for somehow picking and graciously hosting me; to +Sergey Brin (I try not to bug you here, but one time) for inviting me to try G+ originally when I'd otherwise have stayed a hermit; and to the whole photography community here for inspiring, teaching and supporting my work and my growth over the past year and change.

And because it's what I do, I'll tag a couple of themes as well: #photostorysaturday  with +Dave Beckerman, and #sentimentalsunday  with +Louisa Catharine Forsyth (+Sentimental Sunday Theme).

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It's not often I include a proof in a post here, but Geoffrey Pullum's version of Turing's famous result on the unsolvability of the halting problem is hard to resist:

Scooping the Loop Snooper

No program can say what another will do.
Now, I won’t just assert that, I’ll prove it to you:
I will prove that although you might work til you drop,
You can’t predict whether a program will stop.

Imagine we have a procedure called P
That will snoop in the source code of programs to see
There aren’t infinite loops that go round and around;
And P prints the word “Fine!” if no looping is found.

You feed in your code, and the input it needs,
And then P takes them both and it studies and reads
And computes whether things will all end as they should
(As opposed to going loopy the way that they could).

Well, the truth is that P cannot possibly be,
Because if you wrote it and gave it to me,
I could use it to set up a logical bind
That would shatter your reason and scramble your mind.

Here’s the trick I would use — and it’s simple to do.
I’d define a procedure — we’ll name the thing Q –
That would take any program and call P (of course!)
To tell if it looped, by reading the source;

And if so, Q would simply print “Loop!” and then stop;
But if no, Q would go right back to the top,
And start off again, looping endlessly back,
Til the universe dies and is frozen and black.

And this program called Q wouldn’t stay on the shelf;
I would run it, and (fiendishly) feed it itself.
What behaviour results when I do this with Q?
When it reads its own source, just what will it do?

If P warns of loops, Q will print “Loop!” and quit;
Yet P is supposed to speak truly of it.
So if Q’s going to quit, then P should say, “Fine!” –
Which will make Q go back to its very first line!

No matter what P would have done, Q will scoop it:
Q uses P’s output to make P look stupid.
If P gets things right then it lies in its tooth;
And if it speaks falsely, it’s telling the truth!

I’ve created a paradox, neat as can be –
And simply by using your putative P.
When you assumed P you stepped into a snare;
Your assumptions have led you right into my lair.

So, how to escape from this logical mess?
I don’t have to tell you; I’m sure you can guess.
By reductio, there cannot possibly be
A procedure that acts like the mythical P.

You can never discover mechanical means
For predicting the acts of computing machines.
It’s something that cannot be done. So we users
Must find our own bugs; our computers are losers!

Thanks to +Jane Shevtsov for pointing this out!

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An interesting ad!


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Google's done it again! The best place to work in the US!

Super Scientists

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Say NO to PIPA and SOPA.
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