New Mars Forums

I'm sorry, Dicktice, but I'm not sure I can go any further in answering your questions. As I mentioned, I've never really given much thought to the actual quantum mechanism whereby a photon imparts momentum to matter.

    Adding to my April 24th post in this thread, wherein I mentioned the solar sail project of The Planetary Society, here is some more good news from a recent TPS newsletter - and I quote:-

SOLAR SAIL NEWS
    Hardware is on the move. The engineering model of Cosmos 1, our solar sail project, has now traveled from Moscow to Miass, home to the Makeev Rocket Design Bureau, builder of the Volna launch vehicle. At Makeev, the the engineering model will be tested with the Volna's payload separation system, which will sever the spacecraft from the booster after launch. This is a critical milestone in the certification of flight readiness for our mission.

    I'm hopeful that The Planetary Society, of which I'm a proud member, will soon become the first organisation to demonstrate the principle of solar sailing!
    You too could become a member of this great enterprise for a modest annual subscription!
                                         

Any luck with those papers from Rex yet, Josh? I don't think NASA even has a 'mainstream' explanation for most of the 'briny lake' pictures I've seen. Or have they?
    And I'm curious to hear either their (NASA's) or your explanation for at least some of them.
    I reiterate, I do have an open mind about all this but I don't hold with Sagan's maxim that "extraordinary claims require extraordinary evidence". Mars is an alien world. All sorts of things may be equally possible - even though they don't fit into current paradigms. Just because lakes of brine haven't been part of NASA's view of the Martian landscape up to now, doesn't in any way mean they can't exist. In fact, the physics very definitely indicates that they can exist!
    I don't find the notion of briny lakes on Mars to be a particularly 'extraordinary claim', so there is no need to erect extraordinarily onerous 'barriers of proof' - unless you are actually biased against finding such features. But then, that wouldn't be scientific, would it?
    Science is duty-bound to treat all reasonable hypotheses alike. Standing bodies of briny water on Mars form part of a reasonable hypothesis and I, for one, tend to object quite strongly if people with their own personal agendas and axes to grind bring their own politics to bear on the situation by continually 'raising the bar' when it comes to evidence for such hypotheses!

    All that people like Rex Carnes and myself want is for the evidence to be examined dispassionately and for reasonable conclusions to be reached. What we wish to avoid is pompous adherence to some sort of self-congratulatory, holier-than-thou attitude based on an immutable 'Mars is dry and that's that' paradigm!
    Let's have a bit of scientific courage here, shall we?! And a bit less of the old 'It looks like a duck, waddles like a duck, and quacks like a duck ... but, because we don't believe in ducks, it must be a horse'!!!
                                          :angry:

Hi Robert (Dyck, that is.)!
    I don't seem able to access the paper you mention - "Evidence That The Reactivity Of The Martian Soil Is Due To Superoxide Ions", Yen et al. - without subscribing to Science Online.
    I have come across statements elsewhere, though, which suggest Yen and company used UV  light intensities 100 times higher than actual Martian levels in order to obtain their results.
    Is this true?

Hi Nirgal!
    Thanks for this fascinating item about a potential new source of energy.
    I, too, tend to think there's more to cold fusion than the scientific establishment is currently acknowledging. We may yet see something come of it - and I feel all the more confident in saying that because no less a person than Arthur C. Clarke himself seems to think there's way too much smoke to explain without a fire somewhere to explain it!

    This latest apparent energy source appears to be something different again - based on physics unknown to me (nothing strange in that! ) which concerns the 'metastable' form of hydrogen. I assume this means that, at least theoretically, hydrogen is often (? mostly) not in its most energetically stable form (i.e. at its lowest energy level). In other words, given a 'nudge', it may be possible to extract energy from it at little cost.
    Sounds like a dream come true ... perhaps even better than cold fusion - or an alternative explanation all together for the energy attributed to fusion processes in a glass jar.

    What worries me is that this potentially incredible discovery, like all the rest, will die a quiet death and we'll hear no more about it! That seems to happen quite a bit with these things. Whether it's because they're all found to be based on wrong-headed thinking or experimental error, or because endless supplies of cheap clean energy would upset the present world economic system, maybe we'll never really know.

    Anyway, I'd certainly be keen to hear more about this extremely interesting phenomenon.
    Thanks again, Nirgal.
                                     

Thanks, Robert, for the interesting post about drinking and dancing with girls.
                                         

[P.S. The other stuff you mentioned was OK too.    ]

Thanks for the reply, Rex. I've been away for a few days which explains why I've taken a while to respond.
    You raise interesting points about the layering pattern and the logic seems compelling that perhaps they could be 'high tide' marks of an ever-receding waterline.
    I wonder if anyone else has any opinions about this?
                                     ???

I'm not sure if anyone else has posted a reference to this already but, if they have, I apologise in advance!

    One of the latest photographs from Mars has been released via Space.com at this site.

    The picture shows the floor of a crater in western Arabia Terra and it looks like a geologist/paleontologist's delight to me - so many sedimentary layers!
    The lower portion of the photo seems to show lower altitude terrain, judging by the lighting, and some of the ravines there have very dark material in them.
    I have had communication with Rex Carnes here at New Mars (and privately) about such features and, as I understand it, he is of the opinion that dark areas like these may possibly be standing bodies of water ... or, at least, concentrated brine.
    I have an open mind on the subject but he has put forward intriguing arguments for this hypothesis and I, for one, see no obvious reason why he should not be correct in this.

    The physics behind the possibility of standing bodies of brine in certain areas of Mars has been touched on more than once in New Mars threads and I believe the arguments are valid. In low-lying regions, not too far from the equator, such as Isidis Planitia and western Arabia Terra, the atmospheric pressure exceeds the triple point of water - allowing it to exist as a liquid when the temperature is high enough. When you consider the case of very briny water, the 'window of opportunity' for water to exist as a liquid opens much wider. NASA's Chris McKay has published material showing that brine can stay liquid below minus 20 deg.C and at pressures as low as 1 millibar!

    It seems that what looks like dark liquid in the low-lying areas of this picture from Arabia Terra, could plausibly be liquid. It's in the right area and physics allows it.

    Putting aside the mainstream paradigms and just examining the facts as you see them, what does everyone else here think about these features and others like them?
    We know there's lots of water available on Mars.
    We know there's no objection in physics to liquid brine on Mars.
    Many of these features look just like dark bodies of water.
    We know transient dark streaks of liquid flow downhill on certain Martian slopes (we've seen the pictures).
    If it looks like a duck, waddles like a duck, and quacks like a duck ... !

    I'll stick my neck out and say I think we're dealing with standing bodies of briny water.
    What do you think?   ???

This is a little off-topic, for which I apologise, but the drift of the conversation has veered towards the large insects of the carboniferous, a subject I find quite interesting.
    As Robert points out, there is no doubt an ecological-niche explanation for at least some of this gigantism - with lots of food and no predators being among the driving forces behind it.
    However, insects and arthropods don't have lungs in the sense that reptiles, birds and mammals do. To a large extent, they rely on diffusion of oxygen into their bodies through openings in their exoskeletons. Today's 21% oxygen levels put upper limits on the size to which insects can grow before their deeper organs become hypoxic.

    But, as BGD mentions, Earth's atmosphere has varied greatly over geological time. It has been estimated that oxygen levels during the carboniferous period reached a peak of as much as 37% - approaching double the present day concentration! This has been put forward as one of the main factors which allowed the existence of dragon flies with 75cm wing spans, stocky armoured arthropods similar to millipedes but with a length of 1.8m (nearly 6 feet! ), and scorpions which reached dimensions of up to 70cms (~2.5 feet)!!! ... A carboniferous forest was not a good place for a picnic!
                                                 

    Interestingly, the oxygen levels at other times, during the Permian and Triassic eras, dropped as low as 10-12%. At those times, a human would have noticed a marked difficulty in maintaining normal metabolism due to the very low O2 partial pressure. It's hard to imagine needing an oxygen mask just to walk around on your own planet, isn't it? It makes me wonder how the first dinosaurs, which made their appearance during the Triassic, managed to cope in the oxygen-poor air. Perhaps they developed larger chest cavities and lungs to enhance their breathing capabilities(? ).

    Oxygen wasn't the only atmospheric constituent which fluctuated greatly through the ages. 'Only' 220 million years ago, CO2 levels were ~5 times the present day amount. And 450-550 million years ago, CO2 levels were nearly 20 times what they are today!!
    Figures like these put recent man-made rises in CO2 levels into perspective. It is obviously very much harder to create a runaway greenhouse effect on Earth than some of the doomsday merchants would have us believe, thank goodness!
                                           

[Apologies again for getting off-topic. I'll go away now!  ]

Dicktice, have you found time yet to browse through the discussion about photon momentum which Josh provided the link to? If not, I feel it would be a big help to us in this exchange to do so, in order to avoid needless repetition.

    It may help to imagine your single wavelength photons as perfectly elastic rubber balls, all of precisely the same mass, striking a perfectly rigid, flat surface normally (as you specify).
    Each rubber ball has momentum - a certain 'energy of movement' in a certain direction - which we can designate positive momentum. When it strikes the surface in question, it is momentarily halted and then rebounds. It is perfectly elastic and the surface perfectly rigid, so it rebounds at exactly the same speed but in the opposite direction. The surface has not only absorbed all the positive momentum of the rubber ball, but has endowed it with an equal amount of negative momentum (momentum at 180 degrees to the original momentum).
    The surface is consequently given positive momentum equal to twice the original positive momentum of the rubber ball.

    The situation with photons is exactly the same. As discussed previously, a photon has momentum too. With a solid object the momentum can be calculated using this simple equation:-
                  p = mv    (.... where p is momentum
                                              m is mass
                                              v is velocity.)
    This equation holds for all but relativistic velocities.

    For photons, it has been shown that momentum can be calculated using this equation:-
                  p = h/L    (.... where p is momentum
                                               h is Planck's constant
                                               L is wavelength.)

    Thus, the idealised light-sail is propelled forward courtesy of the imparted momentum.
    The wavelength of visible light is very small, but Planck's constant is excruciatingly tiny!! So, the momentum of each photon is also extremely small.
    But at Earth's distance from the Sun, the number of photons per second striking a light-sail is vast and therefore we get a measurable thrust which we can utilise.

    You may be interested to know that The Planetary Society, of which I'm proud to say I've been a member since 1989, will stage a demonstration of light-sail propulsion later this year.
    This first ever solar sail mission is called 'Cosmos 1' and you can read more at this site.
                                     

As most of you know, I'm not 'American' .. in any sense of the word. (The argument over who calls themselves American seems exceedingly puerile to me - just one more infantile example of anti-US belligerence.)
    However, I do try to understand today's politics in some kind of historical perspective. I'm sure most US citizens don't appreciate that their country's dominance is a passing thing. They may be top dog now, but it won't last .. these things never do.
    Those who indulge in the knee-jerk reaction of hating all things American, simply because America is the presently dominant power, are convinced that the future will be better once US power is broken. They imagine a peaceful world dominated by an egalitarian and just UN.
    Maybe they're right ... but that's definitely NOT the way to bet! Human nature (however much the left denies its existence) will almost certainly ensure that selfish power struggles will continue into the future. When America is gone, some other entity will arise to fill her shoes. Power is an intoxicating drug that many, if not most, humans are all too easily attracted to, and addicted to.

    What I don't think very many people understand is the relatively benign nature of the current US dominance. America, though patently imperfect, definitely does NOT deserve the levels of vilification she has been subjected to.
    It's possible to work with America. She is amenable to negotiation and compromise. And, while capable of outright selfishness, she is simultaneously capable of acts of remarkable mercy, generosity and benevolence. America isn't just a faceless bureaucracy - she consists of the people of America .. the ordinary, decent and caring individuals who make up the great majority of her population.
    I, for one, refuse to demonise these people who, on more than one occasion, have used their strength to uphold the traditions of freedom instigated in the old world of Europe. I don't kid myself for one moment that much, if not most, of the freedom I enjoy today I owe to the decency of the American people. When the chips were down - and I mean really down - the American people were there for my ancestors. As far as I'm concerned, they're my cousins.

    As far as the rest of the world is concerned, you should think carefully before opposing everything America says and does, as a matter of course. When the US ceases to be the predominant power, you may not get the world you think you're going to get!
    There are some VERY bad people out there!    ???

Amazing!!
                     

My question about the LIGO thing wasn't actually directed specifically towards Josh. It was really an open question, so if anyone can help, please feel free to jump in! (I usually need all the help I can get! )
    How gravitons fit into this problem is a mystery to me, I'm afraid. I have enough trouble with the wave/particle duality of light ... never mind the proposed similar duality of gravity!! (So no I won't bother to thank you for your suggestion, since it's only added to my confusion! )
                                     

    In response to your question, Dicktice, I don't think it's possible to get total reflectance of light from a light-sail. Imperfections in the surface must result in some absorption.
    The photons which reflect impart twice the momentum to the sail, I would think, as the photons which are merely absorbed. This is because, with reflectance, you have a complete reversal of the sign for the momentum from +ve to -ve. With absorption, the momentum of the photon is merely reduced to zero.
    The light reflected from one light-sail will still impart momentum to a second light-sail in accordance with the equation for momentum.