## Profile

David Schneider-Joseph
Works at SpaceX
Attended Greenwood Sudbury School
928 followers|74,955 views

## Stream

### David Schneider-Joseph

Shared publicly  -

Abstract: In response to Jaffe and Quinn [math.HO/9307227], the author discusses forms of progress in mathematics that are not captured by formal proofs of theorems, especially in his own work in the theory of foliations and geometrization of 3-manifolds and dynamical systems.
1

### David Schneider-Joseph

Shared publicly  -

U.S. states are now competing with other planets for immigrants.﻿
1

### David Schneider-Joseph

Shared publicly  -

Crew Dragon had its first "flight" this morning -- a spectacular (and successful) test of the launch abort mechanism, should anything go wrong on the launch pad or during the flight to orbit.﻿
9
Cuky
+
2
3
2

You could say this was first powered flight ;)﻿

### David Schneider-Joseph

Shared publicly  -

A few seconds prior to touchdown. This came from space!﻿
“Ok, looks like we got some killer footage from the chase plane. Big ocean, small ship. Posting vid shortly”
1

### David Schneider-Joseph

Shared publicly  -
2

### David Schneider-Joseph

Shared publicly  -

This is apparently real?﻿
1
In his circles
260 people
Have him in circles
928 people

### David Schneider-Joseph

Shared publicly  -

Summary: SSL as commonly implemented today is largely broken, and the NSA probably has an exploit.﻿
1

### David Schneider-Joseph

Shared publicly  -

Not The Onion.﻿
An overachieving bigot in Nebraska reached an impressive new level of intolerance this week, filing a lawsuit against “Homosexuals”—as in all of them, everywhere—in a U.S. District Court on Friday, NBC News reports.
1

Well, Gawker, so Almost The Onion.﻿

### David Schneider-Joseph

Shared publicly  -

People feel really strongly about their mechanical pencils. A sample of Amazon reviews for various pencils I'm investigating:

"It is one of those pencil that will always be in my memories."

"With this lead holder in my hand I feel like I'm a kid again and that anything is possible."

"THE BEST PENCIL EVER MADE ... I have been buying mechanical pencils since I was 12 years old (1977) and this is the best one I have ever found. I bought ten of them and gave two to my ex-wife (an accountant for a school) and she agrees ... And if you can get an ex-wife on board... need I say more?"

"The reviews and product description don't completely do this thing justice. I pulled it out of the pack, held it's considerable weight in my hand, and realized that this is the drawing pencil I will use for the rest of my life."

"I bought my first Draft/Matic when I was in the Army, back in 1986 or 1987 and I've never looked back."

"Through out all of my career changes, from a student to a draftsman, Machine assembler to a student, document control officer to a student again, freelance artist to a student once more, to a graphic designer, this has been a constant companion. When people ask me if they can borrow it, I now answer - 'Hell, no! Get your own!' and send them to the link here. It's outlasted computers, cars and trucks, trips cross country, girlfriends, apartments, houses, and in-laws. At this rate it'll be regarded as an heirloom and my grandchildren will be fighting over 'grandpa's pencil' after I'm dead and it's been lost and found a dozen more time in the decades to come."﻿
1

and no link to such an acclaimed pencils? what the hell dude?﻿

### David Schneider-Joseph

Shared publicly  -

The first extensive search for galactic-scale alien civilizations, looking for their expected waste heat signature in the middle infrared. Across 100,000 nearby galaxies, none were found.

"Our motivation is to use this catalog to perform the first extragalactic search for waste heat from galaxy-spanning alien supercivilizations. ... We find that there are no galaxies in our sample of 1x10^5 galaxies with fit values of γ > 0.85, meaning that no galaxies resolved by WISE contain galaxy-spanning supercivilizations with energy supplies greater than 85% of the starlight in the galaxy (unless this energy is not primarily expelled as light in the WISE bandpasses)."

My own hypothesis, which I haven't found anywhere else, is that once a civilization begins to settle surrounding stars, it does so at near light speed, so that there is only a tiny interval of time between evidence of their existence reaching some star, and their colony ships doing so, in the process precluding the possibility of another civilization emerging there (note: this assumes no malevolence, only the exploitation of unclaimed resources). Hence, the birth of a civilization is overwhelmingly likely to occur prior to this evidence arriving, and when it wakes up and looks at the sky for the first time (as we are now), it will see nothing, even if there are other civilizations out there, far away.

A corollary is that births of civilization are spatially sparse and occur nearly simultaneously throughout the universe, probably when the conditions begin to allow it (say, after several star generations have produced appropriate heavy element concentrations, and when gamma ray bursts become infrequent enough to allow the evolution of complex life to progress uninterrupted).

But if this hypothesis is wrong, and civilizations expand at a rate more like 1-10% of the speed of light, then that is still fast enough such that other galaxies should be fully colonized by now, yet not so fast that our own civilization couldn't exist, and see them. Hence, this study may have implications for the long-term survival prospects of any civilizations (including our own), and/or for the prevalence of complex life in the universe, per Great Filter theory: http://mason.gmu.edu/~rhanson/greatfilter.html﻿
Abstract: Nearby Type III (galaxy-spanning) Kardashev supercivilizations would have high mid-infrared (MIR) luminosities. We have used the Wide-field Infrared Survey Explorer (WISE) to survey ~$1 \times 10^5$ galaxies for extreme MIR emission, $10^3$ times more galaxies than the only previous ...
1

It's not necessary, but it's probably inevitable. That's because even a society predominantly resistant to expansion, if it has any cultural diversity at all, is bound to have some dissenters. Unless the society has a cultural uniformity or political centralization far greater than our own, and this status can persist for hundreds of millions of years, through changing political leadership, ideological philosophies, and so on, then invariably one of these dissenters will go forth and colonize. And once they do, it'll be hard to stop them from going as far as they want, especially since the energy resources they extract will put them at a competitive advantage over their homeworld.

And even if you think non-expansion plausible, it's a far stretch from there to assume that all civilizations are like that. Thus, if intelligent life is common in the universe and any of it significantly predates our own, some should be type III civilizations by now.﻿

### David Schneider-Joseph

Shared publicly  -

Video of the landing.﻿
Falcon 9 first stage landing burn and touchdown on Just Read the Instructions
3

It's usually very motivating and exciting, also often stressful. You can send me an ﻿email -- david@davidsj.com -- if you'd like to chat more.﻿

### David Schneider-Joseph

Shared publicly  -

Plot twist: the federal agents that infiltrated Silk Road now stand accused by the Justice Department of taking a cut.﻿
1

That'll be a season cliffhanger.﻿
People
In his circles
260 people
Have him in circles
928 people
Work
Employment
• SpaceX
Flight Software Development Engineer, 2012 - present
Ran the telemetry database for a while. Now working on GNC flight software.
Software Engineer / Site Reliability Engineer, 2010 - 2012
• Amazon.com
Software Development Engineer, EC2, 2009 - 2010
• Mountain Laurel Sudbury School
Staff Member, 2004 - 2009
• Going.com
Software Engineer, 2006 - 2008
Basic Information
Gender
Male
Story
Introduction
Interests: space colonization, Go (the board game), Lisp, AI, economics, non-coercive education, bitcoin, free speech.

Heroes: A.S. Neill, A.M. Turing, R.P. Feynman, S.P. Jobs.

I live near LA.
Education
• Greenwood Sudbury School
2002 - 2003
• Sudbury Valley School
1999 - 2000
• Commonwealth School
1998 - 1999