New Mars Forums

Hi Alokmohan!
    Just in case there's any confusion here regarding silicon based life, none has been discovered here on Earth, or anywhere else yet either.
    Some people here are talking about a possible new form of life, created by humans, in the form of smart computers. Since computers use silicon chips, they are saying you might label such life (if and when it ever eventuates) as silicon based. This is a highly specialised case and is not strictly an accurate use of the term 'silicon based life'.

    As most people probably know, carbon is remarkable in that one carbon atom can simultaneously bond with up to 4 other atoms, thus making highly complex structures possible. This allows for the creation of an almost unlimited array of intricate compounds, an ideal situation for producing something as complicated as life.
    Silicon also has this property of quadruple bonding and has therefore featured in science fiction as an alternative element on which to base life. But there are differences between carbon and silicon which undermine the analogy in fairly fundamental ways. Like Rustyplanet, I can't remember all the differences but there is one which springs to mind: Among aerobic, terrestrial, carbon based life forms, carbon in compounds like sugar is 'burned' in oxygen to provide energy and gaseous carbon dioxide is the respiration by-product. Being a gas, this by-product can be dissolved in circulatory fluids and quickly and efficiently carried away from the cells to where it can be exhaled.
    The product of 'burning' silicon in oxygen is silicon dioxide, which in granular form is better known as sand!
    I'm not saying that marked chemical differences like this one automatically mean that silicon based life cannot exist, but it does put considerable constraints on such life. While I suppose we can imagine a silicon based humanoid (called Rocky, perhaps! ) breathing in oxygen and coughing out clouds of gritty sand, we're still left with the question of how to transport an insoluble solid away from the countless silicon based cellular units in Rocky's body to a place where it can be expelled.
    While slow-moving or stationary silicon based life might exist, undergoing a kind of slow-motion type of life by our standards, it may be harder to visualise it as a high energy, fast metabolising form of life.

    Although silicon may form the basis of life somewhere in the universe, I think the advantages of carbon and its phenomenally diverse range of compounds will always make it the 'element of choice' in the life stakes.
    But then, that's just what I think!!
                                     

Hi Ian!
    The biggest conundrum in physics today is how to reconcile Einstein's relativity with quantum mechanics. Don't ask me why but apparently the mathematics of each, while perfectly consistent and experimentally justified in itself, just won't mesh with the mathematics of the other.
    The best attempts to meld the two into a single Grand Unified Theory (GUT) currently involve the use of something called 'string theory'. To the best of my knowledge, this string theory involves representing particles as infinitesimally small oscillating strings which exist in up to 10 dimensions, including time as one of them. (Yeah, I know ... I have enough trouble visualising 4 dimensions, never mind 10!! )

    Anyhow, the point is that the curved-space-time explanation of gravity stems from Einstein's work on relativity. On the other hand, I believe the Higgs Boson explanation for gravity is based in quantum mechanics and forms part of the search for a theory of 'quantum gravity' which, if found, would amount to the 'holy grail' of unification we've all been looking for.

    If the Higgs Boson doesn't exist, then a lot of apparently very sound theoretical work will have to be re-written. I think it would be quite a drama, resulting in a major re-think of how we understand the universe. But judging by current difficulties in reconciling the two major pillars of theoretical physics, maybe a complete re-think is just what we need!

    As for a spacecraft creating (or enhancing) its own gravity well, that's a very tall order, since such control of gravity would also mean control of time (see Einstein) and would automatically imply a gravity-drive!
    SpiderMan and some others aren't convinced Einstein got it right with relativity. They maintain that there are other explanations for how the universe works and that the speed of light is not the limit, gravity, for example, being thought by some to propagate at almost infinite speed.
    If Einstein's relativity were to be found wanting, and other, better, quantum mechanical explanations were to supplant it, then maybe Higgs Bosons do exist and maybe one day we'll use them to create gravitational fields at will and greatly exceed the speed of light.

    These are exciting times for cutting-edge physics. Back in 1903, there were anomalies that didn't fit in with the state of knowledge at that time; perhaps the most obvious being how to explain where the Sun got the energy to keep shining. These annoying anomalies eventually gave rise to a total paradigm shift with the emergence of e = mc^2, a better understanding of the structure of matter, and the harnessing of nuclear energy. All this came about in just a few short decades.
    I believe we may be on the brink of a new re-evaluation of what we know and I'm hoping it'll give us access to impressive new technologies and open up opportunities for humanity we can only dream about today.

    There are new particle accelerators close to completion. Watch out for news of the discovery of the Higgs Boson ... it could be the start of something big!
                                     

Hi SpiderMan!
    It appears my last post wasn't very clear, for which I apologise. I'm not sure how else to explain what I see as the situation regarding the mechanism by which a solar sail 'sails'.
    Suffice it to say, my personal understanding is that the photo-electric effect isn't a significant contributor.
    As to the relevance of examining the purported difference in wavelength of the sunlight arriving at and leaving the sail (you shrugged and expressed puzzlement at this), this is crucial to answering Dicktice's query. Some theoreticians are asking where the energy is coming from to push the sail. They have concluded that this energy is coming from the difference in wavelength, the red-shift, of the reflected light bouncing off the sail as it recedes from the Sun. They appear to be saying that 'regular' photons from the Sun hit the sail but that red-shifted, or lower energy, photons are reflected back. This difference in energy is where the push comes from.
    They even take this argument further by maintaining that a sail which is perfectly stationary relative to the Sun, won't move. The push, which they say results from the differential in photon wavelength, doesn't happen until something else gets the sail moving in the first place.
    Then they take it still further by deducing that the faster the sail goes, the bigger the wavelength differential, and the faster the sail goes ... and then the wavelength differential is still bigger, so the push is greater and the sail goes even faster!! (Sounds like a 'free lunch' to me.)

    I dispute this. I maintain there is no significant difference in the wavelength of the incident and reflected light at the sail's surface. I justify this argument by appealing to Einstein's concept of relativity to assert that the red-shift is just as applicable to photons reaching the sail as to those reflected back from it.
    But then, if there's no energy differential in the wavelength (or thus frequency) of the photons, where does the push on the sail come from? It comes from the change in momentum of the photons.
    Dicktice once asked me to explain the detailed mechanism whereby a photon arriving at a highly reflective surface has its momentum reversed and flies backwards along its original path, thus imparting twice its original momentum to the sail. I couldn't answer him and I still can't! An excellent knowledge of quantum mechanics is required for that and I haven't the background for it, unfortunately.

    Anyhow, I hope I've at least clarified my position somewhat(?). Apologies again if my previous post was too vague.

    SpiderMan, you asked about the launch of Cosmos 1. It looks like it will be in early 2004 now, following a delay designed to allow more testing. If you're interested, there's a news update at this site.
    Being a longstanding member of The Planetary Society myself, and having donated money towards making this thing happen, I'm very excited about it and looking forward to the launch.
                                         

The last I heard, it should happen in 2005. But I'm not certain of that.
                                   

Hi Alokmohan!
    First of all, welcome to New Mars!

    It's possible Adrian is busy at the moment and might not have noticed your question.
    The Mars Gravity Biosatellite experiment (MGB) is to take place in orbit around Earth. There will be mice on board and there will be time for them to breed and produce more mice.
    The capsule in which they'll live for the duration of their stay in space is to be rotated at such a speed that the mice will experience the equivalent of Martian gravity, i.e. 0.38g.
    The idea is to see what effect, if any, living under Martian gravity has on the ability of mammals to survive and reproduce successfully. We tend to assume that a colony of humans on Mars will adapt to the lower gravity and be able to raise families in the usual way but we have no solid data to show this is possible. If there are any serious problems, MGB should help us to understand those problems in advance of sending people to colonise Mars.
    Obviously, it's much better to find these things out before committing resources and risking lives.
    I hope this has helped to answer your question.
                                     

Thanks, guys, for this interesting 'word origin' diversion!   

    Don't misunderstand me if I sound as though I believe in some kind of righteous correctness of the British way of spelling. In fact, I'm well aware that languages and spellings have always been malleable and have changed in arbitrary ways and for the most obscure reasons.
    I do agree that much of the British spelling is really quite quaint in some respects and, having always liked to imagine I have a scientific streak in me somewhere, I appreciate America's (and Byron's! ) attempts to simplify and rationalise the language.
    No doubt the process of change will continue and, over the centuries, English will evolve into something that we today would find difficult to understand. By then, the little differences we debate today will seem relatively trivial I suppose.

    SpiderMan and Pat, I stand before you embarrassed and chastened. I have indeed confused the 'estset' with the ornate 's' discussed above. My apologies!
    The only excuse I can muster is the 32 year interval since my last German examination ... and maybe the brain damage inflicted by Mr. Billington!
    I generally pride myself on going to considerable lengths in trying to avoid careless errors like that. It makes it all the more frustrating when I do make a stupid mistake!
    But thanks, SpiderMan, for setting me straight. I stand corrected.
                                         

Congratulations Robert!

    You've certainly got me convinced.
    If I ever need my software developed, my firmware initialised, or my system analysed, you are definitely the man I'm going to call!!
                                     

    Keep up the good work!

Robert:-

    This may be an impossible question to answer at the moment, Robert. Your point is certainly a very valid one but there are extenuating circumstances at Mars, compared to Venus, including the fact that sputtering by the solar wind must be roughly only a quarter as intense at Mars' distance from the Sun. In addition, Mars does actually have some degree of protection as a result of its remnant crustal magnetic fields, some of which are remarkably strong and reach hundreds of kilometres above the surface.
    Neither of these factors is going to completely eliminate the water loss problem, I admit that, but it all helps. And I do appreciate that what we gain in terms of magnetic field remnants and distance from the Sun, we tend to lose in terms of Mars' weaker gravitational hold on its volatiles. But I think we probably won't know for sure what the actual rate of water loss is going to be until we set up the 'experiment' for real!
    We don't yet know, for instance, just how much water we'll have to play with. We don't yet know how warm, and hence how humid, we can make the Atmosphere; it may be more difficult than we think to maintain significantly higher global temperatures.
    One more wild card is the so-called 'snowball comet theory', which you've probably heard of. The point of the theory is that the inner planets are still being peppered constantly with watery snowballs some metres across, which keep adding to the volatile inventory. If this turns out to be true, and it is only a fringe theory right now, then not only does Mars probably have more water than we think but its net rate of water loss, even with a denser and more humid atmosphere, may be quite low.
    In any event, I think we are talking about a rate of water loss which, at least on the human time scale, is likely to be virtually negligible ... I hope!!
                                     

    [Even if the rate of water loss is vastly greater than I have suggested, say a half-life of 10 or 20 thousand years, I am confident that our continually improving technological prowess will, by that time, allow us to recoup the losses in some way. In other words, we have plenty of time to worry about it later.]

A great link, Cindy! Thank you.
    I know this is a subject dear to Phobos's heart. Such a pity he no longer contributes to New Mars.

    The space elevator concept appears to be gaining momentum and the hard research into carbon nanotubes seems to be progressing nicely too. I was particularly encouraged by the news from China that it may be possible to fuse nanotubes together without the need for a matrix. From the little I know of this technology, using a matrix dilutes the strength of the finished product. Not having to use one means we should be able to approach or equal the theoretical maximum strength of a carbon nanotube 'ribbon', which means we will have more than enough strength to construct very robust elevator cables.
    The biggest problem, apart from the ever-present threat of attacks by ignorant religious zealots, may be the orbital debris we've left cluttering up near-Earth space. Sooner or later, I suppose we can expect an impact on the cable by a chunk of metal travelling at 27,000 km/h!! This is new territory for theoreticians, I should imagine, and samples of the cable will have to be tested in labs to see how they stand up to that sort of collision. If a cable is going to shear through when hit by something, then it may prove impossible from a safety point of view to ever utilise this brilliant new technology. And what a terrible shame that would be!

    A more sinister aspect to this story may be the involvement of the U.S. military in the background. If space elevators are going to make space easily and cheaply accessible to all nations and groups, then the American military's plans to dominate the planet by securing monopolistic control of the so-called 'high ground' will be scuttled. There may be moves afoot, as we speak, to simultaneously encourage research and development into space elevators while secretly ensuring that their use is strictly controlled. This would be a tragedy if it were allowed to occur because of the consequences to human expansion into space and because it would give the islamic terrorists a new excuse and a whole new selection of recruits eager to bring the cable down!
    I believe moves should be made, early in the piece, to make absolutely sure the space elevator is strictly for the benefit of all. It must not be used for any military purpose and all payloads must be available before launch for multilateral, free-and-open inspection!
    This new technology is potentially a highway into space and no single country, group, or individual should have overall rights to it. It has to be "for all mankind", as is written on that plaque on the Moon.

    Another potential problem is the possible use of carbon nanotubes as horrible weapons here on Earth. I saw reference to this possibility in a fictional book some years ago and it still gives me the creeps just thinking about it!
    You can make a carbon nanotube thread so thin it is virtually invisible to the naked eye but with staggering tensile strength. If you take about 2 metres of this thread, attach a handle at one end and a 500 gram weight at the other, and swing the weight round and round whilst holding the handle, you have a cutting weapon of chilling efficacy. The taut, exquisitely thin, but enormously strong thread would easily sever a human body clean through at the waist (or anywhere else) without losing any appreciable momentum at all! The cut would be so fine you wouldn't know it had happened until you tried to turn around ... !
    An absolute nightmare!!   

    This space elevator technology is just one of a new range of applications of materials science which promise to revolutionise our civilisation over the next 20 years. I think the law makers will be scrambling to catch up with developments during that time in order to protect us all from the potential 'dark side' of these new inventions. And let's face it, somehow there's always a 'dark side', isn't there?
                              ???

Hi Cindy!
    I think the main point they were making with this "can move beyond low Earth orbit to the Moon or beyond" business, is that we have experience with re-entry into Earth's atmosphere by capsules coming in from 'deep space'.
    The shuttle only ever has to survive a 27,000 km/hr re-entry from Low Earth Orbit (LEO). The Apollo capsules returning from the Moon routinely survived re-entry at 40,000 km/hr. A capsule with its one-piece heat-shield is a more compact and robust structure than the shuttle and upgrading the latter to withstand a 40,000 km/hr meeting with our atmosphere would be very difficult.
    In addition, capsules are lighter and easier to launch, not having to bring along wings and hydraulically operated undercarriages with them. Thus it's easier to lob them into LEO with a considerable amount of rocket fuel and a large motor attached, which can then be used to propel them out of LEO to, say, the Moon.
    But I don't think anyone seriously expects NASA to use cramped Apollo-style capsules to make the trip to Mars. The astronauts would surely go mad and kill one another under those conditions!

Gosh! I knew this Voltaire character was a cut above the average philosopher (spot the understatement! ) but this praise by Frederick really underlines Voltaire's almost God-like talent, intellect, self-assurance and social savoir-faire.
    Thank goodness I never met him! The poor man would have been bored to distraction.
                                       

Hi Ian!
    Are you sure you're not thinking of Jupiter? I believe the Jovian atmosphere is constantly wracked with lightning discharges but, in common with Cindy, I couldn't remember anyone saying the same about Venus.

    A bit of research revealed this site, where the following salient points were expressed:-
1) " ... radio data gathered by the Cassini space probe has demonstrated the absence of terrestrial-like lightning on Venus."
2) "If lightning occurs at all on Venus, it must therefore be 100-1000 times weaker, rarer, or briefer than terrestrial lightning."

    Apparently the jury is still out on whether cloud-to-cloud lightning discharges occur on Venus but it's thought cloud-to-ground lightning is inhibited by the "rapid horizontal circulation, or 'super-rotation' of the Venusian atmosphere."

    It's not looking good for lightning bolts on Venus.