Gravitational Lensing

Discussion in 'Science and Nature' started by MelT, Sep 21, 2009.

  1. A nice example:

    2009 September 21
    [​IMG] Abell 370: Galaxy Cluster Gravitational Lens
    Credit: NASA, ESA, and the Hubble SM4 ERO Team & ST-ECF Explanation: What is that strange arc? While imaging the cluster of galaxies Abell 370, astronomers had noted an unusual arc to the right of many cluster galaxies. Although curious, one initial response was to avoid commenting on the arc because nothing like it had ever been noted before. In the mid-1980s, however, better images allowed astronomers to identify the arc as a prototype of a new kind of astrophysical phenomenon -- the gravitational lens effect of entire cluster of galaxies on background galaxies. Today, we know that this arc actually consists of two distorted images of a fairly normal galaxy that happened to lie far behind the huge cluster. Abell 370's gravity caused the background galaxies' light -- and others -- to spread out and come to the observer along [ame="http://www.youtube.com/watch?v=BkBNf_nFuhM"]multiple paths[/ame], not unlike a distant light appears through the stem of a wine glass. In mid-July, astronomers used the just-upgraded Hubble Space Telescope to image Abell 370 and its gravitational lens images in unprecedented detail. Almost all of the yellow images pictured above are galaxies in the Abell 370 cluster. An astute eye can pick up many strange arcs and distorted arclets, however, that are actually images of more distant galaxies. Studying Abell 370 and its images gives astronomers a unique window into the distribution of normal and dark matter in galaxy clusters and the universe.
     
  2. I'm not allowed to +rep you right now so I'll just say that that's pretty cool! I've known of the effect for a while now but never seen a good example like that.

    Physics is so bizarrely interesting. Who could make up the idea that it would be theoretically possible to make a lens out of spacetime?
     
  3. Tremendous, isn't it? Always makes me smile...:)


    MelT
     
  4. #4 ibjamming, Sep 22, 2009
    Last edited by a moderator: Sep 22, 2009
    That's another "theory" that I don't believe... Why isn't it symmetric? I've seen other pictures of it too. One was a star with 4 smaller ones making a perfect +. I think that REAL gravitational lensing should be symmetric...making a halo and not some long stringy thing like that...or four images in a perfect cross pattern.

    What it that we're seeing? Maybe "shimmering" of space. Shimmering due to density fluctuations in the aether that light travels through? I don't buy the lensing story...I'm a skeptic.

    Sure, gravity can bend light...but I don't think it can bunch it up lie that.
     
  5. Why?

    Hold on. Are you saying you disagree with general relativity and, by extension, modern cosmology, in favor of the theory of luminiferous aether? Because gravitational lensing is just a consequence of general relativity, and general relativity explains how light can travel without any special medium. If you think that gravitational lensing doesn't happen and that light needs a medium in which to travel beyond just spacetime, you're basically saying that you don't buy general relativity.

    Plus I thought the Michelson-Morley experiment put the aether theory to rest a long time ago. If you can't detect it no matter what you do, it could possibly maybe be there, but it probably isn't.
     
  6. he must believe in specific relativity
     
  7. Yes...I do disagree with some of general relativity...just as I disagree with Newtonian physics. There is more...we've only scratched the surface. It's good enough for "our world" right now...but it doesn't explain it all.

    He proved an aether that is made of "matter" doesn't exist. But remember...matter is 99.9% empty...what if the proton and electron themselves are 99.9% empty. What if the "aether" is so small that electrons pass through it as effortlessly as we would through a vacuum. Light is a wave...it can't "wiggle" unless it's wiggling in something...this is the medium. It's the "aerogel" that gives space it's structure. It's what light rides in/upon.

    Don't get me wrong, relativity explains a lot...in a "simplistic" way. Just as Newton did many years ago.

    Us detecting the aether is as impossible as you detecting a single atom hitting your hand. It is so small that atoms are like our sun in comparison. Is the sun slowed by the few atoms in the vacuum of space? Would atoms be slowed by something comparatively as small? It's so small as to never be able to be detected. But is DOES do things that we can see...allow light to travel as a wave. Maybe has to do with gravity? I don't know...this is MY best guess.
     
  8. #8 sikander, Sep 23, 2009
    Last edited by a moderator: Sep 23, 2009
    What if, what if, what if...

    General relativity has good evidence in its favor, especially in re the whole dynamic spacetime/bending light thing. You have untestable speculations (if nothing can interact with your version of aether then we can never test for its existence). You could be right, but it's impossible to know. I'll go with the guys who have falsifiable theories, since that remains in the realm of science.

    Also, light is not a wave. You're about a century behind in your physics, which I guess might explain your attachment to aether. Einstein suggested in 1905- 104 years ago- that light is not in fact a wave or a particle, but something that exhibits properties of both. It's called wave-particle duality and can probably be found in any physics textbook published after 1940 or so. Light doesn't need a medium like a classical wave does because it's not in fact a classical wave at all. Or if you wanted to split hairs you could argue that spacetime is its medium.

    Quantum physics, which is probably one of the most successful scientific theories of all time, depends on the idea. If it was wrong I'm highly dubious QP would be as successful as it is.

    But hey, who knows? You might be right. But you're going to need some evidence before I'm willing to throw out the last century or so of physics developed by some of the brightest minds of their time in favor of theories that have been consigned to the dustbin of scientific history on the suggestion of some guy on teh Intarwebz.
     

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