## Profile

David Schneider-Joseph
Works at SpaceX
Attended Greenwood Sudbury School
925 followers|71,929 views

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### David Schneider-Joseph

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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 ...
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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

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

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This is apparently real?﻿
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### David Schneider-Joseph

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The use of body cameras by San Diego police has led to fewer complaints by residents and less use of force by officers, according to a city report ;released Wednesday.
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Really glad to see this happening after decades of work from lots of people, including myself years ago as a teenager. In the last couple of years two towns in Maryland were the first to lower their voting age, and -- surprise! -- the sky didn't fall. Now we have a major U.S. city potentially soon to follow.﻿
San Francisco is poised to become the first major U.S. city to consider a policy that would reduce the voting age to 16. Today, Supervisor...
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Perspectives on society's treatment of genders from people who have been both.﻿
We all know that there are differences in the way men and women are generally treated in society. Transpeople, however, are in the rare potition...
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"Take a little trip back with father Tiresias,
Listen to the old one speak of all he has lived through.
I have crossed between the poles, for me there's no mystery.
Once a man, like the sea I raged,
Once a woman, like the earth I gave.
But there is in fact more earth than sea."﻿
In his circles
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925 people

### David Schneider-Joseph

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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”
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Plot twist: the federal agents that infiltrated Silk Road now stand accused by the Justice Department of taking a cut.﻿
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That'll be a season cliffhanger.﻿

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TIL Mexican states have border disputes with each other﻿
Right now theres a major tussle over borders involving three states in southeastern Mexico. Its been festering for decades in the jungle lowlands of the Yucatan Peninsula.
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One of the only industries in which the supposed beneficiaries have essentially zero say in their service. (Care of the disabled may be the other notable case.)

"Students are the most valuable and least consulted education-policy experts in America. Before they graduate, they spend roughly 2,300 days contemplating their situation ... If you ask students intelligent questions about their classrooms, as it turns out, their answers are more reliable than any other known measure—including expert observations and student test-score growth."﻿
A group of Kentucky teens is struggling to get a modest bill passed, revealing just how difficult it is to convince adults that kids' opinions matter.
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The Great Red Spot is shrinking, but all is not lost: here comes Red Spot Jr!﻿
The Great Red Spot is arguably Jupiter's most iconic feature. Mention the giant planet and most of us conjure up an image of striped gas ball with a big red beauty mark. While the spot has been obs...
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People
In his circles
258 people
Have him in circles
925 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