5 ms·

Astronomers Indirectly Spot Neutrinos Released 1 Second After the Big Bang

47 points by srikar 11y ago

bognition 11y ago
So how exactly does the timing of this work out. If the neutrinos were kicked off at the big bang and have been traveling at nearly the speed of light since then, how is it that we are further away from the epicenter of the big bang than the neutrinos?
- fennecfoxen 11y ago
  "Epicenter"? No, no, it doesn't work that way: the Big Bang was everywhere all at once. It's just that "everywhere" had much less empty space in between it at the time. The way it works is that neutrinos were made everywhere, including some places which, after adjusting for cosmic inflation, are ~13.7 giga-light-years away, therefore the speed-of-light neutrinos produced there will arrive at the Earth approximately Now.
  - danbruc 11y ago
    True but actually unimportant, they didn't observe any background neutrinos but the effect of them on the structure of the cosmic microwave background. Besides that neutrinos have a mass and are therefore expected to travel at subluminal speed and should arrive after photons from the same event however a deviation from the speed of light has not yet been measured (except in Italy but there in the wrong direction).
  - PhilWright 11y ago
    If the Big Bang happened everywhere at the same time then does that mean the universe was infinitely big at the start? Every time I watch a science program about the big bang they say that everything was contained in an area smaller than an atom? Surely both cannot be true. I don't have a physics background, so forgive a naïve question.
    - pdonis 11y ago
      > If the Big Bang happened everywhere at the same time then does that mean the universe was infinitely big at the start? Not necessarily; there are models with a spatially infinite universe and models with a spatially finite universe. In our best current model, the universe is spatially infinite; but there is enough wiggle room in the data that a spatially finite (but very, very large) model is still possible (though unlikely). > Every time I watch a science program about the big bang they say that everything was contained in an area smaller than an atom? They are talking about the observable universe, not the entire universe. Unfortunately, many pop science treatments don't make the distinction clear.
      - TeMPOraL 11y ago
        So correct me if I'm wrong, but it seems that in a model of a spatially finite universe there obviously has to be a centre, right?
        pessimist 11y ago
        Consider the surface of a sphere. It is finite but has no centre.
        krisgee 11y ago
        To make it clear we're on the surface of the sphere, not inside it. I misunderstood this analogy for a long time.
        TeMPOraL 11y ago
        Oh, I forgot about those cases. Thanks! But are those types of models the only finite universe models currently considered? What about just bog standard "surface of a circle", aka. space in a sphere? After all, Olbers' paradox gets resolved by the speed of light and the expansion of the universe.
        pdonis 11y ago
reptation 11y ago
Does anyone know of strong proofs of galaxy red shifts being due to relativistic Doppler effect? It seems like almost everything in Cosmology depends on this being true.
- ProAm 11y ago
  Im not sure what you are asking, this is really proven. Are you asking about a differing theory??
  - reptation 11y ago
    I work down the hall from this guy and he's really convincing: http://www.ccsenet.org/journal/index.php/apr/article/viewFile/25856/15981 http://www.ccsenet.org/journal/index.php/apr/article/viewFil...
    - pdonis 11y ago
      People can be really convincing and still be wrong. As far as I can tell on a quick skim, this theory (that the redshifts are due to differential scattering of starlight) is one that was ruled out several decades ago by cosmologists. Also, his "fundamental inconsistencies of the Big Bang Theory" would be better titled "fundamental misunderstandings on the author's part". The cosmology FAQ I linked to upthread discusses a number of these misunderstandings.
- pdonis 11y ago
  > Does anyone know of strong proofs of galaxy red shifts being due to relativistic Doppler effect? Actually, they're not, they're due to the expansion of the universe. Pop science treatments often say the redshifts are due to the Doppler effect, but that's sloppy terminology. The redshift doesn't really tell you "how fast" a distant galaxy is moving away (although the pop science treatments talk as if it does); what it really tells you is how much the universe has expanded since the galaxy emitted the light you are seeing. So if we're seeing light from a quasar at redshift z = 1, the universe has expanded by a factor of 2 (i.e., a factor of 1 + z) since that light was emitted. And the cosmic microwave background has a redshift of about 1000, so the universe has expanded by a factor of about 1000 since it was emitted (for redshifts this large, 1 + z and z are pretty much the same). As far as "strong proof" that the redshifts are in fact due to the expansion of the universe, and not some other cause, see Ned Wright's cosmology FAQ for a good discussion: http://www.astro.ucla.edu/~wright/cosmology_faq.html#QZ http://www.astro.ucla.edu/~wright/cosmology_faq.html#QZ

47 points by srikar 11y ago

So how exactly does the timing of this work out. If the neutrinos were kicked off at the big bang and have been traveling at nearly the speed of light since then, how is it that we are further away from the epicenter of the big bang than the neutrinos?

fennecfoxen 11y ago
"Epicenter"? No, no, it doesn't work that way: the Big Bang was everywhere all at once. It's just that "everywhere" had much less empty space in between it at the time. The way it works is that neutrinos were made everywhere, including some places which, after adjusting for cosmic inflation, are ~13.7 giga-light-years away, therefore the speed-of-light neutrinos produced there will arrive at the Earth approximately Now.
- danbruc 11y ago
  True but actually unimportant, they didn't observe any background neutrinos but the effect of them on the structure of the cosmic microwave background. Besides that neutrinos have a mass and are therefore expected to travel at subluminal speed and should arrive after photons from the same event however a deviation from the speed of light has not yet been measured (except in Italy but there in the wrong direction).
- PhilWright 11y ago
  If the Big Bang happened everywhere at the same time then does that mean the universe was infinitely big at the start? Every time I watch a science program about the big bang they say that everything was contained in an area smaller than an atom? Surely both cannot be true. I don't have a physics background, so forgive a naïve question.
  - pdonis 11y ago
    > If the Big Bang happened everywhere at the same time then does that mean the universe was infinitely big at the start? Not necessarily; there are models with a spatially infinite universe and models with a spatially finite universe. In our best current model, the universe is spatially infinite; but there is enough wiggle room in the data that a spatially finite (but very, very large) model is still possible (though unlikely). > Every time I watch a science program about the big bang they say that everything was contained in an area smaller than an atom? They are talking about the observable universe, not the entire universe. Unfortunately, many pop science treatments don't make the distinction clear.
    - TeMPOraL 11y ago
      So correct me if I'm wrong, but it seems that in a model of a spatially finite universe there obviously has to be a centre, right?
      - pessimist 11y ago
        Consider the surface of a sphere. It is finite but has no centre.
        krisgee 11y ago
        To make it clear we're on the surface of the sphere, not inside it. I misunderstood this analogy for a long time.
        TeMPOraL 11y ago
        Oh, I forgot about those cases. Thanks! But are those types of models the only finite universe models currently considered? What about just bog standard "surface of a circle", aka. space in a sphere? After all, Olbers' paradox gets resolved by the speed of light and the expansion of the universe.
        pdonis 11y ago

reptation 11y ago

Does anyone know of strong proofs of galaxy red shifts being due to relativistic Doppler effect? It seems like almost everything in Cosmology depends on this being true.

ProAm 11y ago
Im not sure what you are asking, this is really proven. Are you asking about a differing theory??
- reptation 11y ago
  I work down the hall from this guy and he's really convincing: http://www.ccsenet.org/journal/index.php/apr/article/viewFile/25856/15981 http://www.ccsenet.org/journal/index.php/apr/article/viewFil...
  - pdonis 11y ago
    People can be really convincing and still be wrong. As far as I can tell on a quick skim, this theory (that the redshifts are due to differential scattering of starlight) is one that was ruled out several decades ago by cosmologists. Also, his "fundamental inconsistencies of the Big Bang Theory" would be better titled "fundamental misunderstandings on the author's part". The cosmology FAQ I linked to upthread discusses a number of these misunderstandings.
pdonis 11y ago
> Does anyone know of strong proofs of galaxy red shifts being due to relativistic Doppler effect? Actually, they're not, they're due to the expansion of the universe. Pop science treatments often say the redshifts are due to the Doppler effect, but that's sloppy terminology. The redshift doesn't really tell you "how fast" a distant galaxy is moving away (although the pop science treatments talk as if it does); what it really tells you is how much the universe has expanded since the galaxy emitted the light you are seeing. So if we're seeing light from a quasar at redshift z = 1, the universe has expanded by a factor of 2 (i.e., a factor of 1 + z) since that light was emitted. And the cosmic microwave background has a redshift of about 1000, so the universe has expanded by a factor of about 1000 since it was emitted (for redshifts this large, 1 + z and z are pretty much the same). As far as "strong proof" that the redshifts are in fact due to the expansion of the universe, and not some other cause, see Ned Wright's cosmology FAQ for a good discussion: http://www.astro.ucla.edu/~wright/cosmology_faq.html#QZ http://www.astro.ucla.edu/~wright/cosmology_faq.html#QZ