Planet Four Talk

Questions for the team

  • mschwamb by mschwamb scientist, translator

    Hi,

    I thought I'd try something new here on Planet Four: Talk. Does anyone have questions for the science team on anything related to Mars or astronomy or solar system. We had our Zooniverse Talk question discussion awhile ago so I thought it might be fun to do a follow-up here now.

    Ask away. We'd love to hear your questions related to Mars and Planet Four or anything else Solar System related. We'll do our best to answer over the next several weeks.

    Cheers,

    ~Meg

    Posted

  • wassock by wassock moderator

    OK, totally off topic one for y'all. In the olden days, when I was a boy, the general idea was that water was a scares commodity in the solar system and the search for off earth life tended towards "lets find somewhere with water". Now it seems that pretty much all the rocky planets and moons have water to some degree so not so rare at all and the need for aliens to come and steal our precious oceans has receeded. All that in prelude to a simple question - where does the water come from - clearly hydrogen and oxygen plus a spark will do the job but how and where does it form, once the stars have made the ingredients?

    Posted

  • Kitharode by Kitharode moderator

    If you were offered a one-way ticket to Mars to begin the process of permanent human settlement, as well as working as a hands-on martian scientist, would you go? If yes, what is your primary motivation. If no, what's the main problem?

    Posted

  • mschwamb by mschwamb scientist, translator in response to wassock's comment.

    Nice question

    My rough understanding as it's not my particular field, I get to assume bodies just form out of then liquid water molecules and ice making up the circumstellar disk that begins to form planetesimals and then locks water as ice in bodies below the ice line. I know a lot less about the formation of the terrestrial planets so it may have be able to incorporate some of the water in the gas disk as well as from being bombarded by icy planetesimals.

    The water itself I believe is formed on interstellar grains in the instellar medium. The oxygen is generated in the cores of older stars and released into the interstellar medium through stellar winds,shedding layers in planetary nebula at the late stages of stars and also in supernovae explosions. I think this has a nice description.

    Cheers,

    ~Meg

    Posted

  • mschwamb by mschwamb scientist, translator in response to Kitharode's comment.

    In case of the first wave of people to establish a permanent human settlement on Mars, I think I'll pass sadly. I definitely have no aspirations to be an astronaut and would like to firmly keep my feet on the group and rather do the work that can help the first people who do explore mars to have a better foundation. I'm okay with analyzing the data from the remote robots who are going to these other worlds in our Solar System and exploring in that way. Maybe if it got to the point that you could vacation on Mars, I would try it.

    Cheers,

    ~Meg

    Posted

  • wassock by wassock moderator in response to mschwamb's comment.

    Yerse but: Even at STP if you mix hydrogen and oxygen nothing happens. You have to put some energy into the system to get them to react - to get hydrogen to burn spontaneously in air you've got to get it to over 900K. It's a lot colder out in space than that so either something has to catalyse the reaction of there has to be a lot of energy (UV) floating around out there. Can't see that "the dust soaks up the oxygen and when a bit of hydrogen floats past, bang - water", holds up.

    Posted

  • mschwamb by mschwamb scientist, translator in response to wassock's comment.

    There are lots of radiation environments that the interstellar medium interacts with. Actually far UV radiation is thought to evaporate the outer edges of circumstellar disks around young stars.

    ~Meg

    Posted

  • wassock by wassock moderator

    Yeah I kinda realise that, the hard bit I find is getting ones head around just how long, time wise, things have to happen in.

    Posted

  • wassock by wassock moderator

    OK next topic - red shift. (Sorry if this is a bit off the original spec for this)
    So things which are far away are receeding from us faster than things which are closer in a way which is proportionate which distance. Reword that and things which emitted light a long time ago were moving faster than things which let go their light more recently. Ergo expansion was faster a long time ago so the rate of expansion is slowing?

    2nd thing if the redshift of light is down to space actually getting bigger, why does that seemingly apply only to the space the light passes through? Far as I can see the redshift is relative to the atoms/molecules and light they emit in our space-time. If space-time has got bigger since the light started its journey then the emitters would have been smaller than our equivalents are now and so the wavelength of the light at source would have been different. I don't see how you can make space bigger without also changing the properties of the stuff which inhabits the space.

    Posted

  • p.titchin by p.titchin

    That's confused me!! I always try to concentrate on the Einstein start idea that I am the obsever, and all is measured in resperct to me. As a sailor I then imagine sailing into, or away from waves. Simplistic, but that's me. 😃 Thus if I sail into the waves, I pass more per second and my observed frequency of the wave frequency increases, although a swimmer in those waves sees the waves 'own' frequency. If I sail down wave, then the apparrent wave frequency becomes less, although they haven't changed. Thus if the universe expands from me, my observed light frequency drops, (red shift) whatever the direction of the emitted light.' Given light travels at the same speed,then the effects can only be explained by the changing relative speed of the observer. So apparantly simple, but so confusing!! 😦 (There must be someone that can say it better) Come on Brian Greene,join P4 😃 ~Pete

    )Pete

    Posted

  • wassock by wassock moderator

    Hi Pete, as I, don't, understand it the idea is that the doppler explanation for red shift is just an illusion, the star and us are not actually moving, the space between us is getting bigger. So draw the two points on a balloon and a wiggly line between them for the light wave. Now blow the balloon up. The points don't move relative to the bit of rubber you drewes them on, but the wiggly line between will be stretched and will look the same to the observer as if it had been red shifted due to movement.

    Posted

  • p.titchin by p.titchin in response to wassock's comment.

    Hi, thats about as I don't understand it as well. I can see that the balloon analogy helps to explain that although supposedly,nothing goes faster than light, the expansion of the universe means that space is expanding so fast between us and some parts that the light can never reach us. So we can't see them. Leaves my mind well and truely "boggled"~ Pete

    Posted

  • pete-j by pete-j

    Replying to Andy's post above:

    Firstly, this may help a bit:

    i.e.

    Cosmological Redshift The cosmological redshift is a redshift caused
    by the expansion of space. As a result of the Big Bang (the tremendous
    explosion which marked the beginning of our Universe), the Universe is
    expanding and most of the galaxies within it are moving away from each
    other. Astronomers have discovered that all distant galaxies are
    moving away from us and that the farther away they are, the faster
    they are moving. This recession of galaxies away from us causes the
    light from these galaxies to be redshifted. As a result of this, at
    very large redshifts, much of the ultraviolet and visible light from
    distant sources is shifted into the infrared part of the spectrum.

    [http://coolcosmos.ipac.caltech.edu/cosmic_classroom/cosmic_reference/redshift.html]

    Secondly, it may well be that the current theory about the fabric of space-time getting larger and larger may be wrong! After all, science is evolving and there are still problems with the concepts behind dark energy and dark mass.
    See this:

    i.e.

    Now, a new theory suggests that the accelerating expansion of the
    universe is merely an illusion, akin to a mirage in the desert. The
    false impression results from the way our particular region of the
    cosmos is drifting through the rest of space, said Christos Tsagas, a
    cosmologist at Aristotle University of Thessaloniki in Greece. Our
    relative motion makes it look like the universe as a whole is
    expanding faster and faster, while in actuality, its expansion is
    slowing down just as would be expected from what we know about
    gravity.

    [www.livescience.com/33522-accelerating-universe-dark-energy-illusion.html (2011)]

    The mind does indeed boggle!

    Cheers,

    PJ

    Posted

  • Kitharode by Kitharode moderator

    The Universe might be expanding, or it might not. Spacetime might be expanding, or it might not. What we can say (from the study of redshift) is that the distance between the galaxies is increasing. For this to occur we don't need space to expand, we just need space to be there. 😉

    So if I stand still and one of you walks away from me at 2 km/hr, whilst another of you walks away from me at 4 km/hr, then the distance between us will increase. Expanding universe is not required.

    Posted

  • mschwamb by mschwamb scientist, translator in response to Kitharode's comment.

    Hi,

    Well said Kith. We see redshift in star's light due to it's rotation. With the side of the start rotating toward us being blue shifted and the part turning to the side of the star away from us being red-shifted. This can actually be used to identify the inclination of a transiting planet.

    Cheers,

    ~Meg

    Posted

  • Kitharode by Kitharode moderator in response to mschwamb's comment.

    Yes indeed. Same thing with Saturn's ring system. Also tells us about the relative motions of other stars in the spiral arms of the Milky Way. Three cheers for Mr Doppler, eh? 😃

    Posted

  • wassock by wassock moderator

    OK half term done with time to return to the fray.

    This from pete-j''s link above

    Expanding spacetime also explains the redshift of galaxies, which is interpreted as Doppler motion. Since space expands, any photons traveling through that space (from distant galaxies to us) must also expand, i.e. the photons are `stretched' as they travel across the Universe

    So the universe gets bigger and so do the photons in it, and presumably the atoms and the rest of the zoo as well? But my query is that our bit of universe has also expanded since the light left the distant star and is thus also bigger now, as are our photons, than the stars photon was when it started out. So we're not doing a like for like comparison when we compare the 2. The assumption that the light emmited in the distant past would have been the same as the light emitted here and now is false because our space is bigger than the distant stars was?

    Posted

  • Kitharode by Kitharode moderator

    I don't see that "Expanding spacetime also explains the redshift of galaxies...". The redshift of galaxies could imply that spacetime is expanding, if you needed it to expand (which some scientist do), but redshift and blueshift are more easily explained by ordinary movement rather than 'expanding spacetime'.

    Have you ever wondered where this 'expanding spacetime' idea came from? As I understand it, the idea was introduced to answer the question; What happened before the Big Bang? The answer being that there was no 'before'. The big bang 'created' everything, including space and time. Therefore if the universe began as an infinately small point/singularity and is now very large because it expanded, spacetime must also have expanded/is expanding. A very elegant solution, but elegance is not truth. Rather than elegance we need evidence.

    Where is the evidence that spacetime is expanding? Put another way, if the big bang theory is correct, how can we be sure that it did not occur in an infinately large region of empty space? As I understand it the two scenarios produce the same view, so we arrive at a 'belief' system. You believe that space/time was created at the instant of the big bang or, like myself, you believe the bang happened in empty space.

    Posted

  • wassock by wassock moderator

    Think you need space to have gotten bigger to explain the wavelength of the microwave background, or t'other way round the wavelength of the background provides evidence for an expanding universe.

    Thing that I wonder on is that all of this, red shift, gravity, dark matter and all, is based on the assumption that space is "flat" so the effect of gravity can be modeled with a taught rubber sheet (for space) and a ball bearing which distorts the space. So what if space isn"t a flat surface to start with, what if it's actually an egg box?

    Obviously we'd be talking about an n dimensional eggbox

    Posted

  • wassock by wassock moderator in response to Kitharode's comment.

    As the end game of an ever expanding universe is all the energy reduced to individual photons each a very long way from one another, and before that we would still may be have galaxies but each so far distant that you couldn't see one from the other. In either how would you tell if the space inbetween was other than empty, particularly when all the galaxies have gone?
    Preumably even when everything is as spread out as far as, the particle dance of matter/antimatter creation and anililation continue, with the very remote possibility that another big bang could happen again out of nowhere, if it did how could we tell that it didn't start from nowhere? And if such a thing is possible then it must surely happen eventually?

    Posted

  • pete-j by pete-j in response to wassock's comment.

    There was a recent BBC horizon program I would have to get back to you for the title (I have recorded it in my archives for own use).

    Off the top of my head: this used spherical trigonometry (i.e. applying trig to 3D); using the Earth and two very very distant objects in the Universe to form the corners of a triangle. Depending on how the angles added up (not necessarily 180deg) then a determination could be made if the Universe is flat or curved (to 2 decimal places if memory serves me right).

    The result was that space is flat...

    Posted

  • wassock by wassock moderator

    Moving on. Does anyone know how long the microwave background radiation was emitted for? Was it over a period of time or as a single flash of light?

    Posted

  • mschwamb by mschwamb scientist, translator in response to wassock's comment.

    Hi,

    Well the cosmic microwave radiation comes from the moment the photons decoupled from the matter and leave the surface of last scattering, before the moment the soup of atomic particles and photons was opaque and coupled, so it's not a single moment and they were emitted by the hot plasma, so more a period of time (although extremely short in terms of cosmic time). More here.

    Cheers,

    ~Meg

    Posted

  • wassock by wassock moderator in response to mschwamb's comment.

    So are the photons created at the moment everything becomes transparent, or are they there building up over time but unable to go anywhere?
    where I'm going with this is - at the moment the mbr gets released all the matter there is already exists, each photon is the product of one bit of matter. So the number of mbr photons (~400 per Cc? ) is proportionate to the amount of matter in the universe. Not sure where that gets me though.

    Posted

  • mschwamb by mschwamb scientist, translator in response to wassock's comment.

    Hi Wassock,

    I think it's more that some of photons are absorbed by the plasma's electrons and emitted,so it's a state of constant renewal if that makes sense.

    Cheers,

    ~Meg

    Posted