are we alone?•the big bang (and it’s aftermath) produced no element heavier than lithium (atomic...

2-Oct-14 Phys 192 Lecture 5 1

Are We Alone?


Exercise

• Break into groups of 3 or 4

• Nominate a scribe

• Consider the following questions– What evidence would you require to be

convinced that alien life exists?

– What evidence would you require to be convinced that we have been visited by aliens?


A Face On MarsCredit: The Viking Project, NASA APOD: 1998 April 6


The Face on MarsCredit: NASA,Viking Project,

APOD: 1995 July 22


Mars Express Close-Up of the Face on MarsAPOD: 2006 September 25

http://antwrp.gsfc.nasa.gov/apod/image/0609/face2_marsexpress_big.jpg

http://antwrp.gsfc.nasa.gov/apod/image/0609/face2_marsexpress_big.jpg


Mars Express: Return to CydoniaCredit: G. Neukum (FU Berlin) et al., Mars Express, DLR APOD: 2006 September 26

http://antwrp.gsfc.nasa.gov/apod/image/0609/cydonia_marsexpress_big.jpg

http://antwrp.gsfc.nasa.gov/apod/image/0609/cydonia_marsexpress_big.jpg


Extraordinary claims require extraordinary evidence“Dr. Pitts,

I noticed that you will be presenting a lecture entitled ‘The Physics of UFOs.’

I am not attending the lecture, but would like to know if you have written an article on this topic and, if so, whether it is available for people to read.

On the basis of what I have read, there seems to be a fair amount of evidence based on (a) reports from highly reliable witnesses (including former military people, police officers, and pilots) (b) physical trace findings, and (c) radar recordings, which support the hypothesis that at least some reported UFOs are highly technologically advanced craft that may have an extraterrestrial origin. The ‘Extraterrestrial Hypothesis’ seems plausible for explaining at least some reported UFO sightings.

I have also discovered that there is much evidence supporting the hypotheses that our planet Earth is not flat and is not located at the centre of the universe.

No testimony is sufficient to establish a miracle, unless the testimony be of such a kind that its falsehood would be more miraculous than the fact which it endeavors to establish… -David Hume’s maxim


Exercise

• Break into groups of 3 or 4

• Nominate a scribe

• For this exercise, assume there is intelligent alien life elsewhere in the universe.

• Consider the following questions– What are the issues that you think would

make it unlikely for alien life to visit us?

– What are the issues that you think would make it likely for alien life to visit us?


Outline• Discussion of manned spaceflight.

– How does it relate to science/pseudoscience?

• Some universal background info– Size, scale of the galaxy

– Where did the elements come from?

• “Good” planets to support life.

• Development– Do good planets develop life?

– Does life naturally evolve towards intelligence?

– Does intelligence produce technology?

• Searching

• UFOs/Alien abuductions


National Research Council, 2008

“At the present time, given current knowledge, the level of radiation astronauts would encounter would not allow a human crew to undertake a Mars mission and might also seriously limit long-term Moon activity.”

International Space Station astronauts receive a radiation dose that is 27 times higher than we receive on Earth’s surface.The ISS is still protected by Earth’s magnetic field and upper atmosphere.


Galaxies• Our sun is a small star toward the outside of the galaxy, the

Milky Way (a spiral galaxy) containingapproximately 200,000,000,000 stars (2 x 1011)

• A few others (e.g. Andromeda) visible to naked eye

• Telescopes reveal many galaxies, each ~ 1011 stars

Andromeda Spiral Galaxy m100

2-Oct-14 Phys 192 Lecture 5 12from Atlasoftheuniverse.com

•You are here (approximately)

100,000 light years

The Milky Way Galaxy


Views from the Hubble Telescope

• Picture of an area of the sky (the size of a grain of sand held at arm’s length) in which there are no stars visible to the naked eye!

• Shows visible stars in the Milky Way and distant “fuzzy looking” galaxies

• Estimate: ~1011=100 billion galaxies in the universe


Material for Life• The earth is teeming with elements:

– Nitrogen, hydrogen, oxygen, carbon, gold, iron, manganese, uranium, silver, lithium…

• The big bang (and it’s aftermath) produced no element heavier than lithium (atomic number=3).– Hydrogen, helium and lithium only….nothing heavier.

Atomic # = # of protons

H


“Heavy” Elements

• Heavy elements are crucial for life.

– Carbon, oxygen, nitrogen, iron, potassium…

• Where did the heavy elements come from?

– Normal stars (our sun) typically produce helium from hydrogen, but also produce some lithium and beryllium (Be, atomic #=4)

• Elements heavier than beryllium require a higher energy process to produce them…a supernova.

• Supernovas occur at the end of a large star’s life cycle.

– The stuff you are made of: carbon, oxygen, silicon, iron, etc. are supernova remnants!


Supernova

• Expels matter - all heavy elements in the universe (in you!) are formed in supernovae

• Remnant is a neutron star or black hole

• Radiates more energy than an entire galaxy for a brief period (months):

– Famous supernovae:

•0 -- The Christmas Star ??

•1054 -- in Crab Nebula, Recorded in China, …..

•1572 -- in large Magellanic Cloud, seen by Kepler

•Pulsars (Neutron Stars) observed now as remnants of the 1054 and 1572 Supernovae!

•1987 -- in Magellanic Cloud - remnants still observed


Summary

• About 1011 stars per galaxy 2 to 4 x 1011 in the Milky Way

• About 1011 galaxies in the universe

• So we have about: 1011 x 1011 = 1022 = 100,000,000,000,000,000,000,000

stars in the universe.• More stars in the universe than grains of sand on Earth

• Universe is dominated by light elements (H, He, Li) but there are plenty of heavy elements that have been produced by supernovae.


• Question: How many “Earth-like” planets:

• Requirements:– Single star system (not binary)

– Star should be sunlike (similar to our sun)

– Must have planets

– Must have Earth-like planet

• Estimates (arguable, but you can change them!)– ~50% are single star systems (not binary)

– ~10% are sunlike (similar to our sun)

– ~10% have planets

– ~10% have an Earth-like planet

4x1011 x 0.5 x 0.1 x 0.1 x 0.1 = 2x108 =200,000,000 Earthlike planets in the Milky Way galaxy alone!!! [low estimate]

These two estimates are low, reality possibly much higher.

“Good” Places for Life

These two estimates are pretty solid.


Does Life Develop?• Experiments show that organic molecules form in

conditions similar to the earliest stages of Earth’s development.– Carbon dioxide, water, nitrogen + energy (heat or

lighting)

• Details of the mechanisms that bring single celled organisms (like amoeba) from the organic molecules are under study.– Let’s guess that there is only a 1% chance life will

develop on an Earthlike planet. [This is probably a low estimate. The likelihood to develop life on an Earthlike planet is probably very high.]

2 x 108 Earthlike planets x 0.01 chance of developing life

= 2 x 106 = 2,000,000 planets with life in the Milky Way.

[this is still a low estimate]


Does Intelligence Develop?

• Large uncertainty.

• See Hobson textbook for a discussion.– Art Hobson, “Physics Concepts and

Connections”

• The Drake Equation attempt to account for the likelihood of intelligent life to develop, as well as the lifetime “time scale”.– See Origins web site.


How Would We Make Contact?

• Einstein says we can’t travel faster than the speed of light.– Experiments say he’s right.

– This immediately limits the possibilities for space travel between solar systems that are light years apart.

• A light-year is a distance measure.– Recall: c=3x108m/s

– d=ct : 1 light-year = 3x108m/s x 3x107 s/year =1016 m

• Milky Way is about 30,000 light-years wide

• What can travel at the speed of light? – Electromagnetic waves! Light, x-rays, radio-waves.

• First contact with an intelligent life form would most certainly be through electromagnetic waves!


Electromagnetic spectrum

X-rays and gamma rays are also light!


SETI• Search for Extra Terrestrial Intelligence

– Scanning the sky for all electromagnetic frequencies

– Looking for non-random patterns indicating a deterministic source.

• Note: Humans have been broadcasting to the galaxy since the early 20th century.– Our electromagnetic waves now reach out some 80 light-

years away from us.

– Anyone farther than 80 light-years would not yet be able to “see” our broadcasts!

– About 14,000 stars within 100 light-years of us (=0.00000004% of the Milky Way)

• For signals originating elsewhere, our sensitivity depends upon location on time. – To “see” a civilization on the other side of the Milky Way,

they needed to begin broadcasting 30,000 years ago!


How Would We Make Contact?• First contact with an intelligent life form would most certainly be

through electromagnetic waves!

Allen Telescope array, part of

SETI = Search for Extraterrestrial Intelligence Project– Scanning the sky for all electromagnetic frequencies– Looking for non-random patterns indicating a deterministic source.

• You can participate in SETI at Home (link)

http://setiathome.berkeley.edu/


• Humans have been broadcasting to the galaxy since the early 20th century.– Our electromagnetic waves now reach out some 80 light-

years away from us.

– Anyone farther than 80 light-years would not yet be able to “see” our broadcasts!

– About 14,000 stars within 100 light-years of us (=0.00000004% of the Milky Way)

• For signals originating elsewhere, our sensitivity depends upon location on time. – To “see” a civilization near the center of the Milky Way,

they needed to begin broadcasting 25,000 years ago!

How Would They Know We’re Here?

2-Oct-14 Phys 192 Lecture 5 26from Atlasoftheuniverse.com

•

100,000 light years

The Milky Way Galaxy

Our electromagnetic footprint is smaller than this dot!

The rest of the galaxy has no idea that we are here!


UFOs?

• Have we been visited?


UFOs

• Question: Why are they always seen by untrained observers? Professional astronomers and astrophysicists observe the sky daily with sophisticated equipment have never observed an extraterrestrial spaceship.

• Question: Why hasn’t anyone observed the electromagnetic footprint (radio waves, gamma rays, light, etc.) of an alien? The electromagnetic footprint would be here before the aliens would.


UFOs: Natural Explanation

Some sources that might be misinterpreted:

• Approaching Aircraft (appear to hover)

• Unconventional Aircraft

• High Altitude Balloons

• Venus

• Artificial Satellites

• Reflections Off Clouds

• Optical Mirages

• Meteors

• Uncommon Atmospheric Phenomena (Aurora, Ball Lightning)

• Secret Military Objects

• Accidents


Roswell

• Claim of a flying saucer crash in 1947.

• Real explanation likely from Project Mogul, a balloon designed to detect Soviet nuclear testing.

http://www.csicop.org/articles/roswell_film.html

• Most recent version of the hoax was “Alien Autopsy” link– Films originator refuses to have its age verified.

– Lot’s of debunking, even the believers aren’t on board…

• See chapter 6 of “Why People Believe Weird Things” for an excellent discussion of UFOs and alien abductions.

http://www.csicop.org/articles/roswell_film.html

http://video.google.com/videoplay?docid=-5830866813023883728


Summary

• Is there life beyond Earth?– We don’t know.

• Has extraterrestrial life visited Earth?– There is no credible evidence that it has.

• If we make contact with another civilization, it will be by electromagnetic wave.

are we alone?•the big bang (and it’s aftermath) produced no element heavier than lithium (atomic...

Documents