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Thread: Bad Astronomy's BAD Facts and Points made on his TV show are really BAD!

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    Bad Astronomy's BAD Facts and Points made on his TV show are really BAD!

    This guy doesn't know what he is talking about. He was trying to make a point that humans and Alien life will not likely be able to endure the harshness of space travel because of the G-forces having to be endured for months and years! How ridiculous is that! This guy is supposed to be a Phd of Astronomy! Didn't they teach him in school that space is an empty vacuum (mostly) and gravity wouldn't necessarily be present to the intensity of imposing a force that will be felt by the human body. Yes, this guy is really preaching BAD Astronomy. How sad!

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    Not having seen this episode, I may well be corrected, but I strongly suspect you missed the point.

    G forces don't just come from gravity - they come from acceleration in general.

    The G forces a fighter pilot experiences, for example, don't come from Earths gravity - they come from the manouvers made by the plane. e.g. the tighter and/or faster a turn (in any direction*) is made, the more force the pilot will feel.

    wiki link: http://en.wikipedia.org/wiki/G_force

    The issue with getting humans far out into space, is that the distances are very very large. To get anywhere interesting will take huge speeds. To get to those huge speeds will take very large acceleration applied over a very large time. That will likely do "bad things" to humans.


    (* Edit: to pre-nit-pick myself, Earths gravity will affect the g forces the pilot feels - depending on the direction of the turn. But that's beside the point - when a pilot blacks-out due to doing a 10 g turn - those 10 g's were clearly more than the pilot feels from Earths gravity alone, when standing still on the runway).
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    I'm watching it now, and I have to say I'm having a problem with his argument.

    He first talks about it taking a year or more to reach Mars at 2Gs? I think that's an editing mistake: I believe he's talking about reaching escape velocity then coasting for most of the flight to Mars, but that wasn't clear as said. If you could manage 2G constant acceleration, flight time to Mars would be measured in days.

    Then he talks about multiple Gs to go between the stars, apparently to reduce experienced crew time. However, if you could constantly accelerate at 1 G, you could reach the center of our galaxy, or the Andromeda galaxy, in a few decades ship time, so I don't see G forces being a major issue for a humanoid species (well, perhaps a problem if they somehow come from a very low G environment). The bigger issue is the energy requirement for constant acceleration - the energy requirements get insane. Also, high relativistic velocities are tough on spacecraft (even running into hydrogen atoms becomes a serious danger).

    I think you can make a bigger argument about the problems of long crew flight times, though there are ideas for physically possible solutions (robots, life extension, biological stasis, generation ships, or a few other ideas).

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    If anything, the lack of g forces will (and does!) cause problems.
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    Any accelerated frame of reference is indistinguishable from a gravitational field, and this is a basic feature of general relativity. So, any accelerating vehicle will produce G forces, and those might be significant, and the human body will be crushed at very high G's. I don't remember how many G's a human body can sustain before literally being turned into pulp, at least internally.

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    Quote Originally Posted by HowBadisBadAstronomy View Post
    This guy doesn't know....
    Quote Originally Posted by Van Rijn
    I'm watching it now....
    Do I even want to know who or what you guys are talking about?
    Everyone is entitled to his own opinion, but not his own facts.

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    [snide remark said in jest] Do you know what board you are on and who was the author of "Bad Astronomy" and what his latest project is?[/snide remark]

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    Quote Originally Posted by NEOWatcher View Post
    [snide remark said in jest] Do you know...
    Oh, how snide! Actually, I do know who authored Bad Astronomy. But he corrects bad astronomy, not contributes to it. So what is this upstart OP going on about?
    Everyone is entitled to his own opinion, but not his own facts.

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    I agree questioning the "what" (although it sounds like some preconceptions), but I was referring to the "who".

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    Space travel is not astronomy so obviously the OP is incorrect when he says the BA is doing b.a.

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    Months of one or more g is necessary to get to Centauri in 3 years or less, of ship time = about 6 years back on Earth time, but there is no need to experience more than one g if 5 years ship time is the plan, except for a few minutes at lift off from Earth, and minutes before arrival. The Centauri planet, if any, could have more than one g. There is at least a slight possibility that ET finds two or more g comfortable. Technology we will have soon will likely make most of the trip at 1/10 th g or less and take many centuries both ship time and back on Earth time = impractical.
    To a planet 20 light years away, over one g is necessary for minutes instead of years, unless you plan to get there in less than 5 years, ship time. Van Rijn explained excellently. Neil

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    As this post doesn't seem to be a question, I've moved the thread.

    By the way, welcome to BAUT HowBadisBadAstronomy. You must be passionate about this to have picked that as your user name.
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    Quote Originally Posted by Van Rijn View Post
    I don't see G forces being a major issue for a humanoid species...
    I agree, although it was a good "excuse" to fly on an F-15.

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    Quote Originally Posted by R.A.F. View Post
    I agree, although it was a good "excuse" to fly on an F-15.
    F-16.

    And I think it's inexcusable. As Van Rijn noted, 1 gee is enough to get to the Andromeda Galaxy within a few decades of ship time. Human beings are capable of somehow surviving exposure to 1 gee for decades at a time; aliens might be able survive it also. Acceleration isn't the limitation.

    Phil is guilty of bad astronomy--and yes, the physics of relativistic time dilation and the scales of time and distance in the universe are indeed astronomy.

    He also missed out on the opportunity to discuss the real challenges involved in interstellar travel--things like the speed of light, the mind-numbing distances involved, the rocket equation, the heroic amounts of kinetic energy involved at relativistic speeds...

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    Quote Originally Posted by IsaacKuo View Post
    F-16.
    Yeah, I knew it was either a 15 or 16...figured I had a 50/50 chance of getting it right.

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    This is a case where a link of some sort would be quite helpful...

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    Quote Originally Posted by Cougar View Post
    Oh, how snide! Actually, I do know who authored Bad Astronomy. But he corrects bad astronomy, not contributes to it. So what is this upstart OP going on about?
    Quote Originally Posted by mike alexander View Post
    This is a case where a link of some sort would be quite helpful...
    Oh, sorry, this is in reference to his second Bad Universe episode on Discovery channel, discussing aliens and alien attack ideas. I didn't notice that it hadn't been mentioned in thread.

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    I saw the episode last night and noted the same problems-- I suspect a lot of unjudicious editing took place behind the scenes (something Phil would probably have little control over) and that the parts that made scientific sense wound up on the cutting room floor because scientifically illiterate suits thought it was "too complicated" for viewers (meaning they didn't understand it so they didn't see how anyone else could. )
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    Short segment here.
    http://dsc.discovery.com/videos/bad-...et-jockey.html

    I'm a bit disappointed.

    I think that his point about the high acceleration is based on the idea that present-day spacecraft do most of their acceleration in rapid burns. The only types of spacecraft that are currently in use or on the drawing board which are capable of long, slow acceleration times are ion-driven craft and solar sails, and neither of those will get you to the Moon in 3 days. But fission, fusion, antimatter or beamed propulsion concepts could allow quite fast interplanetary journeys without any need for excessive acceleration.

    Phill really needs to read more speculative fiction or something.
    Last edited by eburacum45; 2010-Oct-07 at 09:36 PM.

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    Quote Originally Posted by eburacum45 View Post
    I think that his point about the high acceleration is based on the idea that present-day spacecraft do most of their acceleration in rapid burns.
    No, he goes on about how unthinkable it would be to live with such high accelerations for months or years.

    Sorry, there's just no way to excuse Phil here. What he says is just too wrong. There isn't any part which is even close to correct.

    His fundamental message is wrong. Phil claims that acceleration is the problem. Bluntly, it isn't. This is not just a matter of editing. He explicitly says it's acceleration rather than speed which is the problem.

    Also, we can nitpick all day (turnabout is fair play), and note that Phil's claims are riddled with bad astronomy.

    For example, it takes less than three hours to get from Earth to the Moon at 2 gees, not three days. It takes less than four days to get from Earth to Mars at 2 gees--even at maximum opposition--not a year.

    The basic idea that you need high accelerations sustained for long periods of time to get around in space is simply wrong. It's wrong on a big picture level. It's wrong on a small detail level. It's wrong all around.
    Quote Originally Posted by eburacum45 View Post
    Phill really needs to read more speculative fiction or something.
    What he really needed to do was apply some basic physics equations for a reality check.

    He should have applied d = 1/2 a t^2 to estimate how long it would take to get to the Moon and Mars at 2 gees (modified for switching from acceleration to deceleration at the halfway point). It would have taken maybe 5 minutes for a simple BOE calculation.

    Then, after his eyes returned to their sockets, he could have a nice little "bonk one's own forehead" moment before rewriting this large chunk of the show.

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    Unhappy Bad physics in Bad Universe: Alien Attack

    Shortly before Phil Plait went for his F-16 ride, he nattered on about how traveling longer distances in reasonable time would require uncomfortably high accelerations. This set my physics nerd teeth on edge; the need for high acceleration is limited to the time needed to get away from the surface of Earth. They are not required for the travel between planets -- hence the idea of ion propulsion and solar sails -- nor are these high accelerations required for travel between stars.
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    I agree with Isaac K and others (including the OP). Phil totally jumped the shark on this one. And Whoever said he needs to read some SF was on the mark. This wasn't a bad editing job, it was what Arthur Clarke called the Failure of Imagination (find a copy of the excellent Profiles of the Future). Along the lines of people who said Man would never fly, or ever send a rocket to the Moon. Really, really bad, no excuses.

    I think he just wanted to cage a free ride in an F16.

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    What would have been the point of Phil flying on the F16, if the idea of acceleration hadn't been mentioned first? Perhaps Phil was offered the F16 ride, and a reason to justify that ride was then "invented"...but I really hate to speculate...wish Phil would just post to the board and clarify this.

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    Quote Originally Posted by R.A.F. View Post
    What would have been the point of Phil flying on the F16, if the idea of acceleration hadn't been mentioned first?
    Well, there are the claims about alien spaceships instantly accelerating or making extreme turns at high speed in the atmosphere. I think you could work it in that way, showing the problem.

    As I mentioned in the other thread, there is discussion on BA's blog. Here's BA's comment:

    http://blogs.discovermagazine.com/ba...comment-315910

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  25. 2010-Oct-08, 01:11 AM
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    Van Rijn beat me to it

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    Quote Originally Posted by mike alexander View Post
    This wasn't a bad editing job, it was what Arthur Clarke called the Failure of Imagination (find a copy of the excellent Profiles of the Future).
    Just a ditto, but yes, read it, a great book. I first read it 40 years ago and still think about it.
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    Quote Originally Posted by mike alexander View Post
    This wasn't a bad editing job, it was what Arthur Clarke called the Failure of Imagination (find a copy of the excellent Profiles of the Future)
    I haven't read the book, but a failure of knowledge, surely. The calculations are simply kinematics. Anyone with basic arithmetic can multiply a large acceleration, say, 2g, by a long time, say a month, and get an enormous velocity.

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    The section on high-gees would have made more sense if coupled to a discussion of the impossible physics that some UFOs seem to display. No matter how advanced a civilisation is, it will still have to deal with inertia and conservation of momentum. But prolonged high-gee acceleration is not required for interstellar travel, or for rapid interplanetary travel (except, perhaps, when leaving the gravity well of a planet).

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    Quote Originally Posted by eburacum45 View Post
    The section on high-gees would have made more sense if coupled to a discussion of the impossible physics that some UFOs seem to display. No matter how advanced a civilisation is, it will still have to deal with inertia and conservation of momentum.
    If they have enough exotic matter in their craft, these may not be a problem. Not that I believe in exotic matter.

    Quote Originally Posted by eburacum45 View Post
    But prolonged high-gee acceleration is not required for interstellar travel, or for rapid interplanetary travel (except, perhaps, when leaving the gravity well of a planet).
    For aliens with a compact object in their system a brief period of high gees might be optimal, to get the most out of the Oberth effect.

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    Quote Originally Posted by whimsyfree View Post
    For aliens with a compact object in their system a brief period of high gees might be optimal, to get the most out of the Oberth effect.
    The Oberth effect would not have a significant effect for useful interstellar travel speeds, unless that compact object were a black hole, or maybe a neutron star. Even then, you would need accelerations on the order of 100 million gees to use the Oberth effect. Plausibly, alien biology isn't going to be able to deal with that sort of acceleration. Heck, alien robots plausibly couldn't handle it.

    So, if they want to use the Oberth effect it would be indirectly. They could use some sort of system to use the Oberth effect to accelerate dumb particles (like ions shooting out of a particle accelerator in tight orbit), and those dumb particles are deflected by a magsail for thrust. The starship doesn't ever get very near to the black hole, nor does it need to deal with very high accelerations.

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    The worst thing about the 'gs' bit (etc) is that it does immense damage to the BA's reputation ... it is exactly this sort of misrepresentation (and worse) that he so strongly criticised in the website he started (and which gave him his name). Even worse is his - to me, very lame - excuse for it (see Van Rijn's post for a link to it); when you're in a hole, stop digging.

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