Wednesday, January 23, 2013

More Physics vs. UFOs

Let's continue the theme of two recent postings, the clash between what we know about physics, and UFO claims and beliefs.

In Is there a Warp Drive In your Future? (December 2), UCSD physics professor Tom Murphy examines the claim,  "If it can be imagined, it can be done." He reports, "It took me all of two seconds to violate this dictum as I imagined myself jumping straight up to the Moon... I wondered how pervasive this attitude was among physics students and faculty. So I put together a survey. The overriding theme: experts say don't count on a Star Trek future."

Then in Is Interstellar Travel 'Preposterous'? (December 29), we examine three "classic" papers written by physicists in the 1960s, discussing the feasibility of interstellar travel. Nobel laureate Edward M. Purcell examines the difficulties posed not by technological limitations, but by fundamental laws of physics, and pronounces the idea "preposterous."

E-Skeptic's illustration accompanying the Gainer article (by Nancy White)
Another article in this same vein recently appeared in E-Skeptic, the email newsletter from the Skeptics Society. It is titled The Physics of UFOs - How Realistic is it for spacecraft to travel interstellar distances to earth? Its author is Dr. Michael K. Gainer,  Emeritus Professor of Physics and former chair of the Department of Physics at St. Vincent College in Latrobe, PA.

Echoing the points made fifty years ago by Purcell, Von Hoerner, and Markowitz, Gainer reminds us
The basic principles of physics are applicable independently of where in the galaxy a stellar system is located and will not change over time. Newton’s three laws of motion and the conservation of energy are descriptions of the manner in which different parts of a physical system interact. Consequently, a model based on an exploratory expedition leaving Earth would apply equally to all planetary systems in our galaxy. Any culture, no matter how advanced in technology, would face the same constraints imposed by physics.
He starts with the assumption that a vessel to make such a trip would need to have a mass at least about 100 times that of America's late Space Shuttle, with its living quarters, life support, nuclear fusion reactor, etc. Assume we want to travel to a star system 10 light years away at 0.5c, a trip that would take about 20 years, "For propulsion of the hypothetical spacecraft the blast energy would have to be converted, with near 100% efficiency, to a constrained unidirectional particle beam with thrust pulses of 1.8 megatons per second for 174 days." But here is the rub (and here is what upsets the Star Trek Skeptics crowd): "There is no possible material construction that can constrain and direct the thermal and blast energy of the nuclear fusion rate required for interstellar travel. Consequently, I conclude that alien spacecraft cannot exist." This agrees exactly with what the physics Nobel Laureate Edward M. Purcell explained to us fifty years ago.

But some people who self-identify as skeptics don't want to hear anything like this. Immediately following Gainer's E-Skeptic article is a "rebuttal" to Gainer by Peter Huston, whose degree is not in the physical sciences, but in Asian Studies. Huston objects,
To a non-physicist such as myself, the obvious questions are “Why is such a material impossible?” and “Why is thermonuclear power the only feasible power source?”
To answer these questions, he turned to science fiction writer Carl Fredrick, who is also a retired physics professor. Summarizing Fredrick's response, Huston writes:
First, to assume that something is impossible because current technology, as opposed to the known laws of physics, doesn’t allow it is “silly.” Other points were that there is a great deal of research being done into controlled fusion and that might considerably change the way in which a thermonuclear spacecraft engine might work. Furthermore, as there are now indications that quantum physics might allow a spacecraft to draw energy from the vacuum as it travels, the thermonuclear engines might not be the only source of fuel. Additionally, Frederick said that the Gainer assumed that nuclear fusion is the best form of energy. He disagreed saying that particle / anti-particle annihilation was a better alternative. Finally, he said, there’s no reason one couldn’t go slower and use less fuel, if you, for instance, freeze the crew.
If Dr. Fredrick knows how to obtain antimatter to use as fuel, and how to control and constrain it, we would be very interested to know this. "Zero point" quantum energy from space is a common woo-physics claim (see, for example, Dr. Harold Puthoff), but is not accepted by mainstream physics.

Huston adds a few more lame suggestions, such as "Couldn’t it use solar sails catching photons and the gravitational forces of planets and other astronomical objects to help slow itself?" He obviously doesn't have a clue concerning the magnitude mass and the momentum of the craft. One could much more easily use solar sails to stop a speeding freight train than a massive spaceship traveling at half the speed of light. Huston concludes, "We [skeptics] are supposed to be the people who read, question and think—not the ones who blindly repeat assertions that fit our pre-conceived notions. I think we, as skeptics, need to be more careful of such statements and false conclusions. They only hurt us in the end." As if the need to obey the laws of physics were a 'pre-conceived notion.'


Gainer's response to Huston is in the following issue of E-Skeptic, and begins by noting the difference between "belief systems and science... A belief system need not concern itself with objective reality. This contrasts with science in which theories are subject to objective evaluation by repeated experiment and measurement. Science assumes a priori the existence of a measurable objective reality. Indeed, science is the delineation of this reality." He continues, "any spacecraft, whether from present or future technology, would have a significant inertial mass. Ten thousand years from now conservation of energy will apply anywhere in the galaxy as well as it does today." 

As for the objection that magical future technologies could somehow  build substances that can be used to constrain fusion reactions, "because of the maximum cohesive force that electrons can create between protons no substance will remain solid above 5000ÂșC. " The temperature of a nuclear fusion reaction is on the order of 10,000,000 degrees C. That has nothing to do with present-day, or future technologies. It is because the energy of the strong nuclear force released in the fusion reaction is overwhelmingly more powerful than the weak electromagnetic bonds that hold atoms and molecules together. But the Star Trek Skeptics don't want to hear this. They want to believe that some future technological wizard will invent a super-glue whose atomic binding is even stronger than the strong nuclear force. Gainer concludes, "It is not present or future technology that negates interstellar travel—it is the nature and structure of matter and the universe."

16 comments:

  1. Hey Robert, let me ask you something: Do you believe in the technology of the LASERs? You don't seem to be someone educated in the physical sciences, as I am, but someone rather parroting the opinions of other experts. Anyways, back to the LASER. The interesting thing about it is that under the classical wave theory of light, the entire concept of light amplification by the stimulated emission of radiation would have been considered a fantasy 100 years ago, the same as warp drives are today. The laws of classical physics simply forbade the construction of a laser.



    Now we know classical physics works in its domain, so how can the LASER exist? Simply because it is an approximation, just like its possible in the future quantum mechanics is also an approximation of a framework not yet conceived that reduces to quantum mechanics on the microscopic scale and general relativity on the larger scales of the universe. As seen endlessly throughout the history of science, such a new theory could lead to revolutionizing technologies that would be fantasies under the former theory.

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  2. I am a skeptic of modern physics and of interstellar space travel; I therefore agree with Robert's posts on improbability of easily going from star system to star system, as in Star Trek. As I've said, it is possible to go faster than the speed of light (contrary to the assertions of modern physics), but the velocity equation flips, and the motion is in time, rather than space. Material atoms would decay to inverse atoms, and poof--there goes the space ship. I think all those sightings of UFO's are military craft.

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  3. For those just joining, here's the summary of the discussion:

    "Is Interstellar Space Travel Possible?" In other words, can ET hop in his spaceship from a star system 2 million light-years away and visit Earth.

    The Skeptics say NO because of the unmerciful constraints of the Fundamental Laws of Physics. Even ET, no matter how smart (he/she/it?) may be, cannot violate the Laws of Physics.
    Building a spacecraft that could zip along at one-eight the speed of light would require 1.6 billions of tons of fuel for each spaceship ton. Also, stopping the spaceship and shielding itself from atoms are more big issues. White papers written by respected physicists mention these problems.

    The Believers says YES because ET is highly evolved and has these constraints figured out. Anything is possible, dude! There's so much physicists don't know yet but ET has it mastered. Speculative UFO propulsion ideas are presented such as fusion drives, anti-matter reaction drives, and my favorite the "Unknown Technique Drive". Or, ET could space travel, in theory, via worm-holes, whereas worm-holes actually existing is just a theory. ET have been visiting Earth, say the Believers, and this explains why folks are observing UFOs.
    What do you think?

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  4. It is foolish for any physicist to claim that interstellar travel is forever impossible. It is equally foolish to claim that ETs could never, in any circumstances, have visited earth in the past or in the future.

    We can only estimate the likelihood of such things based on our present day knowledge and on what evidence we have now.

    Arthur C. Clarke engaged in plenty of this kind of speculation and generally concluded that these things were possible at some future time. He may be wrong, but how can we be certain one way or the other?

    We do not know how long humanity will survive as a species, or how long our planet will survive. There may be interstellar races travelling to earth at this moment - who are we to say otherwise? By the time they reach here, we may have disappeared. Tough luck on our visitors!


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  5. cda:
    "It is foolish for any physicist to claim that interstellar travel is forever impossible."

    And if they said that, then you would be right.
    But they do not say that is is forever impossible.

    They are talking about how feasible and realistic it is.
    The "forever impossible" seem to be words somebody else put into their mouths.



    cda:
    "It is equally foolish to claim that ETs could never, in any circumstances, have visited earth in the past or in the future."

    It is equally foolish to claim that ET are visiting us via spacecrafts, in the complete absence of evidence that these spacecrafts or Ets actually exist.



    cda:
    "We can only estimate the likelihood of such things based on our present day knowledge and on what evidence we have now."

    The fundamental laws of physics put tight constraints on what is realistically possible.
    And the actual evidence is zero. We have only claims to work with.



    cda:
    "Arthur C. Clarke engaged in plenty of this kind of speculation and generally concluded that these things were possible at some future time. He may be wrong, but how can we be certain one way or the other?"

    Appealing to magic future technology is fruitless. It is no different from the creationist god-of-the-gaps and the quantum-mumble-mumble of alternative "medicine" supporters.


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    Meson:
    "As seen endlessly throughout the history of science, such a new theory could lead to revolutionizing technologies that would be fantasies under the former theory."

    Can you point us to a natural phenomenon that would allow a macroscopic object, like a spaceship, to travel interstellar distances over humanly sensible timescales?

    After all, quantum mechanics was developed because there were phenomena that could not be explained with classical theories.

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  6. At the current level of our understanding of physics and the nature of the universe and without entertaining exotic theories such as worm holes and warp drives, it does seem that the only feasible form or interstellar travel, as alluded to in the article, is to put the crew into cryostasis and bring them back when the ship reaches its destination. Time, after all, becomes irrelevant when we speak of traveling distances which are light years away. For instance, if we were to find a habitable planet 100 light years distant, what are our options in terms of sending a crew to the planet? Even if we ignore the article above and suggest that we can find a way to travel close to the speed of light, the effects of traveling at relativistic speeds means the occupants will experience time dilation and as such the journey for them would take perhaps 14 years but for those back on Earth it would take 101 years (not taking into consideration the need to accelerate at 1g and also decelerate to arrive at the destination). Now even if they turned around and went straight back they're going to get back to a very different world, one that is over 200 years more advanced and likely one where everybody they knew is now gone, a world that may very well have taken a turn for the worse (global nuclear wars, massive climate change etc) and everyone that has survived has forgotten the craft ever left! So effectively they're leaving their world behind, there is no going back.
    The other choice of course is to take advantage of known technology and physics to build a craft that could perhaps get up to 3 to 5 percent of the speed of light (nuclear pulse propulsion?) and put the entire crew into cryostasis. When the craft arrives at its destination 100 light years away, two millennia would have passed on Earth and again there's no going back.
    Either way, the amount of time it takes to get to the destination is so great that it becomes irrelevant.
    So why even bother trying to find a way to travel at near light speed if we're talking about getting out of our own galactic neighborhood, after all a 100 light year radius is a tiny fraction of the area that our 100,000 light year sized galaxy encompasses.

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    1. I think, its very possible that what we consider a human life-span may be considered very short by a civilization/intelligence that is older than our own, or even in the future by our own descendants. There isn't any strict evidence that this will be the case for us, and none at all for any putative ET, but the possibility that intelligent life can engineer itself successfully beyond it's initially evolved constraints is worth considering. Even if we discount direct travel, if time-scales are altered then (for instance) the dispatch of small probes that will not report back via radio for centuries, even or simple radio communication between stars light-years apart assumes a different perspective. I agree that interstellar travel is a feat at the extreme limit of conception, and considering all the dangers and caveats seems pointless for current human biology (and maybe anything biological). But for something that might be the advanced descendant of biological life, (as crude analogy: a small, light, very intelligent, very durable and self repairing robot/inorganic life form transported by large, powerful propulsion) where time is not such an issue, such a trip, though still risky, might have more meaning.

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  7. Just by probability considerations, there must be numerous advanced civilizations in the Milky Way and other galaxies. The civilizations closer to the galactic center would be more advanced than the ones on the periphery. If any of these civilizations have been able to develop faster than light speed in space, then why haven't we seen any visitors? The Ancient Aliens TV series on H2 is an entertaining mix of fact and speculation, but they never show any hard evidence--like actual spacecraft or alient artifacts. I therefore conclude that not only the physics prevents faster than light speeds in space, I think the evidence is lacking. Neutrinos (cosmic or inverse ones) can move faster than light through material atoms, but they cannot be used as a space ship.

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  8. Papageno: Yes, in fact, a physicist by the name of Richard Obousy published an interesting peer-reviewed paper and an article in discovery about using a well known quantum phenomena as the basis of a practical interstellar mission. The phenomena is known as the Schwinger Effect, which is predicted by quantum electrodynamics. If you have the required technical knowledge, then I highly recommend you look at his paper here: http://richardobousyconsulting.com/varies.pdf

    If not, then read this article on discovery that is more layman friendly: http://news.discovery.com/space/astronomy/varies-interstellar-antimatter-lasers-icarus-120716.htm

    To the classical physicist, such a concept would be dismissed as nonsense and would cite the laws of energy conservation and thermodynamics.

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    1. From the linked paper:
      "The goal of this research program is to construct a spacecraft architecture with the unique capability to create antiproton fuel from the vacuum of space itself, utilizing the phenomenon of Schwinger pair creation using intense electromagnetic fields. The mission architecture would be optimized for an interstellar rendezvous and return mission, which would lay the foundation for future manned missions by demonstrating the ability to return a spacecraft safely to our solar system after having visited a distant target solar system (Fig. 2)." (R. Obousy)

      He is talking about another way of producing the fuel for an interstellar spacecraft. The spacecraft is still a rocket.



      Meson:
      "To the classical physicist, such a concept would be dismissed as nonsense and would cite the laws of energy conservation and thermodynamics."

      The concept does not violate energy conservation and thermodynamics, because the system needs to produce the energy to supply to the laser, in order to produce the strong electric fields to induce pair production.
      You shifted the problem from carrying enough reaction mass to producing enough energy. The proposal is just a new form of "living off the land" by imagining to use solar panels to collect energy from the Sun and the star of the target system.

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    2. I never alluded to this not being a rocket, so I don't know where you got that from. You asked "Can you point us to a natural phenomenon that would allow a macroscopic object, like a spaceship, to travel interstellar distances over humanly sensible timescales?", to which I answered using the well established quantum phenomena known as the Schwinger Effect, which could be the basis of a future interstellar spacecraft once the engineering issues are resolved, if ever.

      "The concept does not violate energy conservation and thermodynamics, because the system needs to produce the energy to supply to the laser, in order to produce the strong electric fields to induce pair production."

      That is correct, but that is because of the definition of a vacuum in quantum field theory. In classical physics, the vacuum was thought to be completely empty and devoid of matter and energy, and thus this proposal would have easily been dismissed as it would have appeared to violate conservation of energy and thermodynamics.

      Furthermore, this doesn't shift the problem, it effectively solves it. The so-called "soda can" problem that has plagued aerospace engineering is no longer much of an issue for a spaceship that is propelled on the principle of matter-antimatter annihilation, as one would only need a few grams of antimatter to get the average sized probe to a significant fraction of the speed of light.

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    3. Meson:
      "I never alluded to this not being a rocket, so I don't know where you got that from."

      UFOlogists like to appeal to a magic future technology that does not use rocketry to make a spaceship move, like quantum-mumble-mumble.




      Meson:
      "You asked "Can you point us to a natural phenomenon that would allow a macroscopic object, like a spaceship, to travel interstellar distances over humanly sensible timescales?", to which I answered using the well established quantum phenomena known as the Schwinger Effect, which could be the basis of a future interstellar spacecraft once the engineering issues are resolved, if ever."

      Except that the effect is proposed to provide fuel, not propulsion. The antiprotons are produced before travelling, and the Schwinger effect does not take part in the propulsion.

      The only advantage of that proposal, is that the spaceship would not need to carry at the beginning the fuel for the return journey. It would simple "top up" its fuel in the target solar system before the return journey.

      And since the propulsion is still based on rocketry, it does not change the travel time.



      Meson:
      "That is correct, but that is because of the definition of a vacuum in quantum field theory. In classical physics, the vacuum was thought to be completely empty and devoid of matter and energy, and thus this proposal would have easily been dismissed as it would have appeared to violate conservation of energy and thermodynamics."

      Nope. It does not even appear to violate the conservation of energy and thermodynamics, because the Schwinger effect requires strong electric fields in a small space, which means that there is a large energy density in that space. It is not devoid of energy (classically).

      And is why they need a big honking laser and good power supply.



      Meson:
      "Furthermore, this doesn't shift the problem, it effectively solves it. The so-called "soda can" problem that has plagued aerospace engineering is no longer much of an issue for a spaceship that is propelled on the principle of matter-antimatter annihilation, as one would only need a few grams of antimatter to get the average sized probe to a significant fraction of the speed of light."

      How do you go from the energy produced in the annihilation process (mostly in the form of gamma radiation) to actual propulsion?

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  9. Oh, and the maximum speed of an antimatter-matter spaceship is anywhere upwards of 99% of the speed of light. Of course, for practical purposes and relativistic effects, 50% of c is clearly more feasible.

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  10. Ha, Ha--"creating anti-protons from the vacuum of space"--what nonsense. This is why most engineers just laugh at the nonsense of "modern physics."

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  11. "As for the objection that magical future technologies could somehow build substances that can be used to constrain fusion reactions,..."

    I just want to clear, constraining a fusion reaction is beyond our current technology, are you really saying that it is not possible? Why would governments and scientists continue to work on this problem then with the long term plan to build electricity generating plants using fusion reactions. Yes, scientists, government and industry all estimate it being decades away, they definitely are trying though, spending lots of money.

    Speculating that certain technologies like fusion drives or anti matter drives are beyond our current ability, but that's not the same as magic since there are theoretical and conceptual ways to achieve those technologies.

    Obviously 'can't be done' is not the same as 'hasn't been done before'

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    1. Mr. Shaefer, the question was "Is interstellar space travel impossible?" It was not "Can we do it with our current level of science and technoglogy." These are distinctly different parameters.

      Both I and Carl Frederick found flaws in the "rebuttal to my rebuttal" but we felt we both had better things to do than spend time arguing with people who weren't listening and were arguing from a pre-conceived position and denying evidence to the contrary.

      BTW, will someone please tell me why it is relevant that aside from teaching physics at Cornell for years and working for NASA, Carl Fredericks has also written published science fiction for Analog among other venues?

      Like I said, the whole experience reminded of why I got badly burnt out on the whole skeptics field years ago. Too many people engaging in.circle jerk intellectualism from a closed minded point of view.

      All the best,

      Peter Huston

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