1. New to the forums? Check out our Mentorship Program!
    Our mentors will answer your questions and help you become a part of the community!
  2. Welcome to Smogon Forums! Please take a minute to read the rules.

Planck telescope results - the next steps for cosmology

Discussion in 'Congregation of the Masses' started by cantab, Jul 6, 2010.

  1. cantab

    cantab

    Joined:
    Oct 22, 2009
    Messages:
    3,300
    [​IMG]
    http://news.bbc.co.uk/1/hi/science_and_environment/10501154.stm

    This is the first all-sky map created by the European Space Agency's Planck space telescope. It images in the microwave wavelengths.
    For one, this is an absolutely brilliant image. It will I think become recognised as one of the truly great astronomical images, up there with the likes of the Hubble Deep Fields and some of the brilliant nebula photographs.
    It's also of great scientific significance - or rather the data behind it is. ESA say this particular rendering is no good for science due to the colouring and lowered resolution.

    Features of interest:

    The bright mauve across the middle is our galactic disk

    The blue features above and below it are reckoned to be "streamers" of gas that surround our galaxy. The exact origins of these streamers is I think still not fully settled, but they're suspected to be formed from dwarf galaxies that came too close to the Milky Way and got ripped apart.

    The mottled red background is perhaps the main focus of interest - the Cosmic Microwave Background, the oldest radiation in the Universe. This is the data that could answer the really big cosmological questions - although in fairness, many, like the Universe's age and overall composition, are already pinned down well by WMAP. But already the Planck image looks sharper than that of WMAP, and the Planck data will get even better as the probe continues operating.

    Thoughts, on either the Planck results or on cosmology in general? (To be honest I really just want people to see the picture)
  2. vonFiedler

    vonFiedler Visualize It
    is a Community Contributor

    Joined:
    Mar 22, 2010
    Messages:
    4,192
    It's so relatively symmetrical, is that merely due the perspective of the rendering?
  3. cantab

    cantab

    Joined:
    Oct 22, 2009
    Messages:
    3,300
    If you mean the way stuff seems to curve inwards, then yeah, I think it's to do with the projection - this is a flat picture of what's actually a full sphere, so inevitably there's some distortion.

    The similarity between top and bottom hemisphere's is because the galactic plane is picked as the "equator", so you'd expect the same general thing either side, though of course details differ.
  4. MrIndigo

    MrIndigo

    Joined:
    May 30, 2009
    Messages:
    2,244
    In fact, it's the asymmetries in the cosmological data that are most interesting, because all of our models take homogeneity as given.
  5. cantab

    cantab

    Joined:
    Oct 22, 2009
    Messages:
    3,300
    Although in fairness, the approximation of an isotropic, homegenous Universe is one made simply to make the maths easy.

    Slight inhomgeneity we expect. After all, the Universe today isn't a uniform gas. In the cosmic microwave background the variations are absolutely tiny.

    But large scale anisotropy WOULD be interesting. (In fact, in the CMB one hemisphere does differ from the other, and this difference tells us how fast we're moving relative to the CMB reference frame. That's not of massive cosmological importance but is kind of neat.)
  6. TubaKing

    TubaKing

    Joined:
    Jul 12, 2009
    Messages:
    315
    This image is marvelous.
    It's weird to think of the limitations of satellites in relation to the constancy of the speed of light.
    Like... an image of something one light-year away will take at least one year to reach us, so we'd be seeing something as it was one year ago.
    I think Carl Sagan talked about something like this in his book Cosmos, where he wrote of a hypothetical situation where two astronauts were floating in the middle of space with nothing but void between them while being an X number of light-years (or whatever unit he used) apart from each other. For my retelling of this situation (for I don't recall exactly what he wrote, seeing that I read this four years ago), I'll say that the two astronauts are one-hundred light-seconds away from each other.
    If light were somehow reflecting off of the two astronauts, they would see each other not as they actually "are" in space-time, but as they "were" a hundred seconds ago. So once they see each other, they would then see their reactions to each other one-hundred seconds apart.
    Also, if we developed a telescope to see the center of the universe, and the center of the universe is, say, one-hundred-billion light-years away, we would be seeing it as it was one-hundred-billion years ago and not as it actually is today.
    Sorry that my post was only tangentially related to the OP and not particularly well expressed, but I wanted to share some food for thought.
    EDIT: Actually, do you know how far away the satellite was from Earth when this was sent?
  7. cantab

    cantab

    Joined:
    Oct 22, 2009
    Messages:
    3,300
    The "centre of the Universe" does not exist, or alternatively, everywhere is the centre. This holds for either an infinite Universe or a finite Universe that "loops back" on itself.

    Special relativity gets weird. What really blew my mind when studying it at uni is that simultaneity is relative. To take your astronauts. Suppose they both pick their noses without seeing the other do it first. In a piece of unfortunate timing, three spacecraft fly by with different velocities (and all with no acceleration eg engines off). Craft 1 sees both astronauts pick their noses at the same time, craft 2 sees astronaut A pick first, craft 3 sees astronaut B pick first. And each craft's view is considered equally valid - none is preferred over any other.

    1.5 million km from Earth, at the Earth-Sun L2 point, which is 'outside' the Earth's orbit. The combined gravity of Earth and Sun mean craft at the L2 point orbit the Sun at the same angular speed as the Earth. There's a few craft there, including Planck's predecessor WMAP. Craft actually orbit around the L2 point, so they don't crash into each other, though the orbits are unstable so they need to expend a little fuel to stay in them.
  8. MrIndigo

    MrIndigo

    Joined:
    May 30, 2009
    Messages:
    2,244
    I don't think this is exactly true; I'm pretty sure you can't reverse the order of events (i.e. causality) using the Lorenz transforms. What you can do is say that Craft 1 sees Astronaut B pick his nose 10 seconds after Astronaut A, Craft 2 sees Astronaut B do it 15 seconds after Astronaut A, and so on.
  9. cantab

    cantab

    Joined:
    Oct 22, 2009
    Messages:
    3,300
    You can't reverse causality, no. Relativity of simultaneity holds only for events with a spacelike seperation; events that could not be travelled between by an object moving at or below the speed of light and thus neither can cause the other.

Users Viewing Thread (Users: 0, Guests: 0)