The Fermi Paradox - Ashford Astronomical Society

The Fermi ParadoxThe Fermi Paradox

““what alienswhat aliens””

By David J Styles By David J Styles BA CSci FIBMS SSGBA CSci FIBMS SSG

Educated GuessworkEducated Guesswork







Educated GuessworkEducated Guessworkin action…in action…


Fermi ProblemsFermi Problems


Fermi was known for his ability to make good approximate calculations with little

or no actual data

http://en.wikipedia.org/wiki/Fermi_problem


For example:

How many piano tuners are there in Chicago?



•There are approximately 5,000,000 people living in Chicago. •On average, there are two persons in each household in Chicago. •Roughly one household in twenty has a piano that is tuned regularly. •Pianos that are tuned regularly are tuned on average about once per year. •It takes a piano tuner about two hours to tune a piano, including travel time. •A piano tuner works eight hours a day, five days in a week, and 48 weeks in a year.



From these assumptions we can compute that the number of piano tunings in a single year in Chicago is

(5,000,000 persons in Chicago) / (2 persons/household) × (1 piano/20 households) × (1 piano tuning per piano per year) = 125,000 piano tunings per year in Chicago.

And we can similarly calculate that the average piano tuner performs•(50 weeks/year)×(5 days/week)×(8 hours/day)×(1 piano tuning per 2 hours per piano tuner) = 1000 piano tunings per year per piano tuner.

•Dividing gives (125,000 piano tuning per year in Chicago) / (1000 piano tunings per year per piano tuner) = 125 piano tuners in Chicago.



The size and age of the universe suggest that many technologically

advanced extraterrestrial civilizations ought to exist.

However, this hypothesis seems inconsistent with the lack of

observational evidence to support it.

Observational EvidenceObservational Evidence



The Drake EquationThe Drake Equation

Dr. Frank Donald Drake (born May 28 1930)

http://upload.wikimedia.org/wikipedia/en/f/f9/Frankdrake.jpg


N = R* x fp x ne x fl x fi x fc x fL

• N - how many planetfuls of aliens there are• R* - the rate of star formation in our galaxy (Stars per year)• fp - the fraction of stars that have planets around them• ne - the fraction of stars with planets that are capable of sustaining life• fl - the fraction of planets in ne where life evolves• fi - the fraction of fl where intelligent life evolves• fc - the fraction of fi that try to communicate with other planets• fL - the expected lifetime of such a civilization in years



• N - how many planetfuls of aliens there are with whom we could communicate



• N - Dunno• R* - Measureable• fp – Measureable (to a degree)• ne - Guessable• fl - Guessable• fi - Arguable• fc - Arguable• fL - !



• R* - the rate of star formation in our galaxy (Stars per year)

Seven

http://www.physorg.com/news9595.html Other sources quote 5 – 10

Drake said 10

The ESA say 6


N = 7 x fp x ne x fl x fi x fc x fL

• fp - the fraction of stars that have planets around them

1

Says Me !!! Everything we’ve found in space has something spinning round it.

Drake said 0.5


N = 7 x 1 x ne x fl x fi x fc x fL

• ne - the fraction of stars with planets that are capable of sustaining life

0.09

Assume all G class stars like our sun have such planets

http://www.peripatus.gen.nz/Astronomy/Sun.html

Including class F & K as well as G class stars might knock this up to 0.27

Assuming NOT all G class stars like our sun have such planets would reduce this number

http://www.peripatus.gen.nz/Astronomy/Sun.html


N = 7 x 1 x 0.09 x fl x fi x fc x fL

• fl - the fraction of planets in ne where life evolves

0.1

http://www.newscientist.com/article.ns?id=dn4525

“10% of star systems in the Galaxy are hospitable to life, by having heavy elements,

being far from supernovae and being stable themselves for sufficient time”

Drake said 1

http://www.newscientist.com/article.ns?id=dn4525


N = 7 x 1 x 0.09 x 0.1 x fi x fc x fL

• fi - the fraction of fl where intelligent life evolves

1

Says Me !!! Define intelligence !!

Drake said 0.01


N = 7 x 1 x 0.09 x 0.1 x 1 x fc x fL

• fc - the fraction of fi that try to communicate with other planets

0.3

Says Me !!! Neanderthals & dolphins never made radio waves.

I can find no other examples (!)

Drake said 0.01 – where did he get this figure ?


N = 7 x 1 x 0.09 x 0.1 x 1 x 0.3 x fL

• fL - the expected lifetime of such a civilization in years

This is the biggie !!!


N = 7 x 1 x 0.09 x 0.1 x 1 x 0.3 x fL

• fL - the expected lifetime of such a civilization in years

420 years (lower estimate)

Michael Shermer, Why ET Hasn't Called, Scientific American, August 2002, page 21

Drake said 10 000 years

Me – is there an upper limit ? Let’s try 100 000 years (reasonable figure?)


N = 7 x 1 x 0.09 x 0.1 x 1 x 0.3 x 420

N = 8


N = 7 x 1 x 0.09 x 0.1 x 1 x 0.3 x 420

N = 8

Well, we ain’t alone.

More generous figures give us:


N = 10 x 1 x 0.27 x 0.1 x 1 x 0.3 x 100 000

N = 8100

That’s a lot of aliens!

The Drake EquationThe Drake EquationTo recap:

Using science, wit, guesswork and idiot enthusiasm we have shown there are between 7 and 8099 alien civilisations in our galaxy with which we could communicate.

Hold those thoughts…….

The Milky WayThe Milky Way

Educated Guesswork

The Milky WayThe Milky WayThe Milky Way

Guesswork


Guesswork

Galactic Radius:Galactic Radius:40 000 – 100 000 ly40 000 – 100 000 ly

Central thickness:Central thickness:16 000 – 35 000 ly16 000 – 35 000 ly

Total stars:Total stars:1000 000 000 – 4000 000 0001000 000 000 – 4000 000 000


Quite smallQuite small

Astrophysical Journal 662, p. 322,Astrophysical Journal 662, p. 322,http://arxiv.org/abs/astro-ph/0702585http://arxiv.org/abs/astro-ph/0702585

http://arxiv.org/abs/astro-ph/0702585

The Milky WayThe Milky WayThe Milky WayTwo short conesTwo short cones

The Milky WayThe Milky WayThe Milky WayVolume of a cone:Volume of a cone:

The volume of a cone = 1/3(Area of Base)(height) The volume of a cone = 1/3(Area of Base)(height) = 1/3 π r2 h= 1/3 π r2 h

So galactic volume = 2* 1/3(Area of Base)(height)So galactic volume = 2* 1/3(Area of Base)(height)

= 13404128640000 ly= 13404128640000 ly33 (lower estimate) (lower estimate) = 183259571250000 ly= 183259571250000 ly33 (upper estimate) (upper estimate)

The Milky Way

To recap:

Using science, wit, guesswork and idiot enthusiasm we have come up with upper and lower plausible values for:

5. The numbers of alien civilisations in our galaxy with which we could communicate

7. The volume of space containing these alien civilisations

Finding the AliensFinding the Aliens

Best-Case Scenario:

3. Lots of aliens

5. Small galaxy


Best-Case Scenario: Some assumptions

• Stars are equally spaced throughout the galaxy

(not an unfair assumption where we are)

• Aliens are equally spaced throughout the galaxy

(Absolutely no idea!)


Best-Case Scenario:

• Lots of aliens (8100 civilisations)

• Small galaxy 13404128640000 ly13404128640000 ly33


Best-Case Scenario:

• Each alien civilisation is at the centre of a sphere of volume

1340412864000013404128640000 =165483070 ly =165483070 ly33

81008100


Best-Case Scenario:

• Volume of a sphere is Volume of a sphere is

• A sphere of volume 165483070 ly165483070 ly33 has radius 412.6 ly has radius 412.6 ly

• trust me on the sums…..trust me on the sums…..


Best-Case Scenario:

So civilizations are 2* 412.6 =about 800 ly apart 412.6 =about 800 ly apart


Best-Case Scenario:

So civilizations are 2* 412.6 =about 800 ly apart 412.6 =about 800 ly apart

At closestAt closest

To recap:

Using science, wit, guesswork and idiot enthusiasm we have shown that the closest alien civilisation to Earth is probably no closer than 800 ly away.


800 Light Years800 Light Years

800 Light Years800 Light Years46 days at warp 9.975

http://www.ussdragonstar.com/utilitycore/warpspeeds.asp


800 Light Years800 Light Years46 days at warp 9.975


Two problems:

3. Warp drive is theoretically impossible4. Warp drive is theoretically impossible


800 Light Years800 Light Years

http://www.guinnessworldrecords.com/content_pages/record.asp?recordid=46995

Helios 1 reached 1.4% of light speed

57 000 years at that rate

http://www.guinnessworldrecords.com/content_pages/record.asp?recordid=46995

Which I believe explains the Fermi Paradox

Which I believe explains the Fermi Paradox

(but I could be wrong)

Please don’t clap

Please don’t clap

Just throw money !

Date post:	03-Feb-2022
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The Fermi Paradox - Ashford Astronomical Society

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