Data Structures Lecture

(c) copyright 1997 by Daniel Berleant Data Structures Lecture
Today:

Last day of MWF classes
No final; projects due at noon on Monday, Dec. 14
Today: discuss a general prediction technique and the Distant Future

The Distant Future

source: article by Richard Gott, astrophysicist at Princeton (Local mirror: Richard Gott
Reference: "Implications of the Copernican Principle for Our Future Prospects," Nature, Vol. 363, 27 May 1993
Copernicus: our place in space is most likely not special

Basic premise: *now* is a random point in the lifetime of X
(X is the human species, the United States, the PC, whatever . . .)
If you have no special information, you can use this technique
If you DO have special information, this technique does not apply
Hence: technique is highly general, but doesn't give precise dates
The idea --
Life span of SOMETHING: START (time=0) END | | V V ---------y---------x------------------------------------z--- p=0.25 | p=0.5 | p=0.25 p(random time point being in the "middle 50%") = 0.5 If random time point x=3 years . . . Then p=0.5 that . . . x+(1/3)x < END < x+3x Or...p=0.5 that . . . (4/3)x < END < 4x

Scientific data is typically considered "reliable" if it shows something with p>=0.95 . . .
Life span of SOMETHING: START (time=0) END | | V V ------------------------------------------------------------ *|******************p=0.95********************************|* \ / \_____ / \ / / / p=0.025 p=0.025 p(random time point being in the "middle 95%") = 0.95 If random time point x=3 years . . . Then p=0.95 that . . . x+(1/39)x < END < x+39x Or...p=0.95 that . . . (40/39)x < END < 40x

Applications

The human species has lasted about 200,000 years
95% chance that the total lifetime of humanity is:
(40/39)(200,000) < HUMANITY < 40*200,000
205128 < HUMANITY < 8,000,000
or . . . The human species will last
at least 5,000 years more but less than 7.8 million years more

Using population instead of years, we have a 95% chance of lasting at least 12 more years!

Chronological sequence of births of members of the human species: The first person You are here? The last person | \ | V \ V ------------------------------------------------------------ *|******************p=0.95********************************|* \ / \_____ / \ / / / p=0.025 p=0.025

Case in point: nuclear war, etc.
We have a 2.5% chance of lasting LESS than 12 years more...
(Given no special information)
Adding special information, my guess is:

we're probably doing better than that now

we were probably doing worse in the 70's & 80's?

Alas, the chance we will last 1 Billion years is extremely small...

Application: How much longer will we have "PC's"?
(Let's figure it out on the board...)
Application: How long will the term "United States of America" last?
Will the human race colonize a million stars in the galaxy?
chance = 1/1,000,000

Will the human race give rise to a million more advanced intelligent species?
chance = 1/1,000,000 ???

If (when?) the human race is over, what next?
Chance of us being the root of a huge subtree of intelligent follow-on species very low
Chance of us being the root of a few intelligent follow-on species not bad
These species could be part- or all-machine, no evidence either way
Gott: our best hope for our particular species is to colonize a few extraterrestrial bodies.
The probability of our doing that is reasonable, and we as a global society have free will(?)

. . . OTHER APPLICATIONS OF THE PRINCIPLE . . .
Will the human race become a Dyson sphere of O'Neill space colonies?

(Solar powered space colonies forming a sphere around the sun and using all the solar energy)
This implies a human population 10⁸ x the present or more
p(Dyson sphere)= 1/10⁸
Very low!

Will the human race become a Kardashev type III civilization?
(Colonize entire galaxy with a Dyson sphere around each start)
This implies a population 10¹⁷ x the present population
p(Kardashev Type III Civilization)= 1/10¹⁷
(about 1 in 100 quadrillion)

"civilization (with cities and writing) has only been around for 5,500 years"
How much longer will this hold?

We have had the "capacity and motivation" for space travel for about 35 years
How much longer will we have it?
Gott's conclusion: we should try to colonize Mars before it is too late!
(I would add the moon to that)