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How to facilitate contact? Recall the dilemma: direct physical contact with ET or more indirect radio communication. People or Photons? People have mass and that requires enormous amounts of energy to accelerate.

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how to facilitate contact
How to facilitate contact?
  • Recall the dilemma: direct physical contact with ET or more indirect radio communication.
people or photons
People or Photons?
  • People have mass and that requires enormous amounts of energy to accelerate.
  • People have needs (food, water, air, etc) which means more mass to transport! How much mass per person to take?
  • Space ships travel very slowly
  • Photons are mass-less and travel at the speed of light!
current spaceship technology
Current spaceship technology
  • Spacecraft travel at speeds much less than 100,000 km per hour
  • At this speed, travel to the nearest star would take 46,500 years!
photons
Photons
  • Sending a signal has its own energy challenges
  • Signal strength drops off as the square of distance.
photons5
Photons …
  • Thus for any given signal strength, sending it say one million times further requires (one million)2 times as much energy … that is, one trillion.
  • This is technically possible (bigger transmitters, shorter messages, etc) but is not cheap. It is cheaper than sending people in spacecraft though.
space travel
Space Travel
  • (12) Humans have gone to the Moon
  • Machines have traveled in our Solar System out to Neptune and en route as we speak to Pluto
  • As a species we have the urge to explore and colonize.
challenges to travel to the stars
Challenges to travel to the stars
  • Distances involved are enormous and will take us time to traverse
  • The energy requirements are equally immense and very difficult to satisfy (even if we are willing to pay the price).
power for the trip
Power for the trip
  • Chemical combustion is our current form of energy in rockets … very inefficient.
  • Solar power works well near stars but is also inefficient
  • Nuclear power for both on-board power (to live, etc) as well as thrust is possible with our technology.
  • Matter and anti-matter … more efficient certainly but also beyond our means at present.
exotic power
Exotic power
  • Interstellar Ramjets …
  • Ion propulsion … prototypes already tested.
  • Warp drive … dilithiunm crystals anyone?
time dilation
Time Dilation
  • As you travel faster, your own clock (in your frame of reference) slows down from an outside perspective.
  • Traveling at a significant fraction of the speed of light means you experience a smaller passage of time compared to an Earth based observer
relativity
Relativity
  • T = T0 / Sqrt (1 –v2/c2)
  • where T0 is the time elapsed in the moving frame of reference
  • where T is the time elapsed in the stationary frame of reference
  • where v is the speed you are moving relative to the stationary observer.
a solution perhaps traveling at high speed will allow people to survive interstellar treks
A solution? Perhaps traveling at high speed will allow people to survive interstellar treks.
time dilation example
Time dilation example
  • You and your friend synchronize your watches.
  • You remain on Earth and your fired ‘flies off’ at 99% the speed of light.
  • Your friend returns when 1 hour of time has elapsed according to their watch.
  • You have waited approximately 7 hours for your friend to have returned!
one more danger
One more danger ..
  • At higher speeds for our spacecraft, the particles in the ISM are now moving at enormous velocities relative to you.
  • If your spaceship is moving at 99% the speed of light, the kinetic energy of a particle in the ISM will seem like a very energetic bullet and could do serious damage to the spacecraft … shields anyone?!
automated messengers
Automated Messengers
  • Instead of people in spaceships, send automated messengers.
  • Pioneer and Voyager spacecraft already carry messages from Humanity
von neuman machines
Von Neuman machines
  • Build an automated robotic spacecraft and send it to a distant star/planet.
  • When there, let it mine resources and replicate itself, sending copies of itself to other stars/planets.
  • In short order, such robots could be everywhere!
  • So where are they? … the Fermi Paradox (later)