4 ms·

Is the lopsided Universe telling us we need new theories

38 points by efficientarch 13y ago

Myrth 13y ago
It's unclear for me how observers can be sure that the differences they see are actually originated far far away, and not result of local interference: cloud or dark matter or whatever else. As far as I know, we have only 1 point of perspective, our Earth. Of course I have no idea how exactly they observe stuff, but that's the question I immediately have.
- bladedtoys 13y ago
  Very roughly speaking there are at least three ways to measure distances. For "near by "objects on can use parallax: look at the object on a given date then again 6 months later and see how much it shifts against the back ground stars. Simply triangulate using the known distance from earth to sun as half the side of a triangle. For "moderate" distances one can rely on certain variable stars that always have a known brightness. Then when you locate such a star, note how dim it is and calculate how far away it would have to be to have that brightness level. For "far" distances one can measure the red shift. That is to say, on the large scale everything in the universe appears to be moving away from us. Further away object move faster than nearby objects. Thus if you can measure how fast something is receding from us you can tell how far it is. The technique for measuring speed like this is to measure the Doppler red shift.
  - Steuard 13y ago
    But none of those techniques is applicable to variations in the CMB (the subject of this article), which is a more or less uniform glow at constant (and in some sense, maximal) redshift (and by definition, behind the "background" stars). I suppose that if this "axis of evil" were due to a pattern in nearby dust clouds we might be able to see some hints of paralax, but paralax would probably be difficult to measure for something as diffuse and broad as the pattern visible in this data. It's my impression, for the record, that cosmologists are pretty confident that these variations aren't due to intervening dust. My sense is that the spectrum of the CMB in any given direction is very clearly a blackbody spectrum (the most precise blackbody spectrum in nature, in fact), so any absorption due to foreground matter should be pretty recognizable (and possibly even something they could correct for).
- jerf 13y ago
  The CMB is "so far away" that the largest structures that you can think of are still incredibly tiny points against the CMB. We can tell it's not being blocked by normal matter, because we know what that looks like. If you want to hypothesize other possible effects, well, join the club; that's a popular cosmologist past time, but bear in mind that in addition to explaining the lumps, your new hypothesis must actually explain the non-lumps, and everything else as well. This turns out to be a pretty big hurdle. Furthermore, we're not measuring "things", we're measuring temperature. If a "thing" was blocking the CMB, it would do so by being a hotter thing. Thus, a "thing" can't create a cold spot just by obscuring the CMB... it can only create a hot spot, relative to the CMB. Another place you can see this is in "dark matter" replacement theories. As unsatisfying as an invisible, undetectable particle is to answer the questions about the universe, it isn't enough to just explain one or two subquestions; you need to provide a better explanation of everything we see, including the places where it really, really looks like dark matter is the only feasible explanation (where galaxies collide and the visible matter appears to have gotten detacted from the dark matter halos, as seen by gravitational distortions, which is really hard to explain with any of the alternate theories). It's "easy" to beat the consensus on one detail; it's proved pretty hard to beat the consensus across the board, even as the consensus is known by everybody to be unsatisfactory in some ways.
Steuard 13y ago
This is a fascinating anomaly, and totally worth studying. But my perspective as a physicist in a different but somewhat related field has always been to tentatively assume it's just a statistical fluctuation. If you look at the graph at the bottom of the first page of this article, have a look at the error bars on those data points: every one of them is at least borderline consistent with the smooth theoretical curve. (Or, alternately, look at the light green region around the curve: that shows the unavoidable uncertainties that we expect based on our finite view of the universe. The points they're interested in almost all lie within that range.) So yeah: it's a neat possibility, and it's great that people are looking into models to explain this (and to search for related predictions they can test). But it's not significant at a level that should get non-cosmologists tremendously excited at this point.
- graycat 13y ago
  Okay, when I was in physics as a ugrad, it was a long time until the LHC! So, my understanding of the now hot topics is from little more than just layman reading! Or, as I can guess at Guth's inflation, there was a quark; space expanded explosively so that maybe any two 'sides' of the quark were pulled apart faster than the speed of light; so, the quark was split into two quarks, that is, some energy was converted into quark mass. But two quarks have an axis. Could that be the origin of the 'axis of evil'? Or, how the heck else to have Guth's inflation starting with the first split of something without having an axis, that is, in 3 space, a line for the axis and perpendicular to a plane? Or, from that first split that generated mass, how can we avoid an axis, sure, in some 'random' direction but, still, an axis?
  - Steuard 13y ago
    The issue you're running into here is that you're focusing on the description of this physics in terms of particles. That's usually a very convenient perspective, but it tends to have issues when gravity/spacetime is doing weird things (or even in an accelerated reference frame, which is sort of the same thing). What you really want to focus on is the question, "What are the (quantum) fields doing during inflation?" Those fields will typically be in a state with a whole lot of symmetry, and only small, random fluctuations away from that state will lead to perturbations in the CMB. I might be able to frame this in the particle picture, too. The issue is that there wasn't just one quark! There's a whole intense thermal mass of quarks and other particles, and the energies are high enough (and times short enough) that more of them are being pulled from the vacuum and annihilating back into it all the time (this is largely a field-theory statement, I'm afraid). That mass of quarks is what's being pulled apart by inflation. So there's no single special original quark particle that triggers the whole thing. [Disclaimer: I'm not actually a cosmologist, so I welcome corrections on anything I've misstated there!]
coldcode 13y ago
Physics is a strange and wonderful science. The more we learn the more we realize we don't understand. I've always believed that there are features of the the structure of the universe(s) that we have no idea even exist yet. It's like bringing Newton from the past, dropping him in an open field, and telling him he is surrounded by wireless communications. He'd have no clue what that meant. Likewise we are likely surrounded by things we don't have the background yet to recognize.
brlewis 13y ago
http://en.m.wikipedia.org/wiki/Betteridge's_law_of_headlines http://en.m.wikipedia.org/wiki/Betteridge's_law_of_headlines
gottebp 13y ago
I ran across this before the Planck probe data had confirmed what WMAP had found. There is a good write up on the alignment anomaly by theoretical cosmologist Dragan Huterer about it: http://www-personal.umich.edu/~huterer/PRESS/CMB_Huterer.pdf http://www-personal.umich.edu/~huterer/PRESS/CMB_Huterer.pdf Fascinating to see it still causing a ruckus all these years and a whole other probe later.
- dhimes 13y ago
  This is a really excellent link. Thank you.

38 points by efficientarch 13y ago

Myrth 13y ago

It's unclear for me how observers can be sure that the differences they see are actually originated far far away, and not result of local interference: cloud or dark matter or whatever else. As far as I know, we have only 1 point of perspective, our Earth. Of course I have no idea how exactly they observe stuff, but that's the question I immediately have.

bladedtoys 13y ago
Very roughly speaking there are at least three ways to measure distances. For "near by "objects on can use parallax: look at the object on a given date then again 6 months later and see how much it shifts against the back ground stars. Simply triangulate using the known distance from earth to sun as half the side of a triangle. For "moderate" distances one can rely on certain variable stars that always have a known brightness. Then when you locate such a star, note how dim it is and calculate how far away it would have to be to have that brightness level. For "far" distances one can measure the red shift. That is to say, on the large scale everything in the universe appears to be moving away from us. Further away object move faster than nearby objects. Thus if you can measure how fast something is receding from us you can tell how far it is. The technique for measuring speed like this is to measure the Doppler red shift.
- Steuard 13y ago
  But none of those techniques is applicable to variations in the CMB (the subject of this article), which is a more or less uniform glow at constant (and in some sense, maximal) redshift (and by definition, behind the "background" stars). I suppose that if this "axis of evil" were due to a pattern in nearby dust clouds we might be able to see some hints of paralax, but paralax would probably be difficult to measure for something as diffuse and broad as the pattern visible in this data. It's my impression, for the record, that cosmologists are pretty confident that these variations aren't due to intervening dust. My sense is that the spectrum of the CMB in any given direction is very clearly a blackbody spectrum (the most precise blackbody spectrum in nature, in fact), so any absorption due to foreground matter should be pretty recognizable (and possibly even something they could correct for).
jerf 13y ago
The CMB is "so far away" that the largest structures that you can think of are still incredibly tiny points against the CMB. We can tell it's not being blocked by normal matter, because we know what that looks like. If you want to hypothesize other possible effects, well, join the club; that's a popular cosmologist past time, but bear in mind that in addition to explaining the lumps, your new hypothesis must actually explain the non-lumps, and everything else as well. This turns out to be a pretty big hurdle. Furthermore, we're not measuring "things", we're measuring temperature. If a "thing" was blocking the CMB, it would do so by being a hotter thing. Thus, a "thing" can't create a cold spot just by obscuring the CMB... it can only create a hot spot, relative to the CMB. Another place you can see this is in "dark matter" replacement theories. As unsatisfying as an invisible, undetectable particle is to answer the questions about the universe, it isn't enough to just explain one or two subquestions; you need to provide a better explanation of everything we see, including the places where it really, really looks like dark matter is the only feasible explanation (where galaxies collide and the visible matter appears to have gotten detacted from the dark matter halos, as seen by gravitational distortions, which is really hard to explain with any of the alternate theories). It's "easy" to beat the consensus on one detail; it's proved pretty hard to beat the consensus across the board, even as the consensus is known by everybody to be unsatisfactory in some ways.

Steuard 13y ago

This is a fascinating anomaly, and totally worth studying. But my perspective as a physicist in a different but somewhat related field has always been to tentatively assume it's just a statistical fluctuation. If you look at the graph at the bottom of the first page of this article, have a look at the error bars on those data points: every one of them is at least borderline consistent with the smooth theoretical curve. (Or, alternately, look at the light green region around the curve: that shows the unavoidable uncertainties that we expect based on our finite view of the universe. The points they're interested in almost all lie within that range.) So yeah: it's a neat possibility, and it's great that people are looking into models to explain this (and to search for related predictions they can test). But it's not significant at a level that should get non-cosmologists tremendously excited at this point.

graycat 13y ago
Okay, when I was in physics as a ugrad, it was a long time until the LHC! So, my understanding of the now hot topics is from little more than just layman reading! Or, as I can guess at Guth's inflation, there was a quark; space expanded explosively so that maybe any two 'sides' of the quark were pulled apart faster than the speed of light; so, the quark was split into two quarks, that is, some energy was converted into quark mass. But two quarks have an axis. Could that be the origin of the 'axis of evil'? Or, how the heck else to have Guth's inflation starting with the first split of something without having an axis, that is, in 3 space, a line for the axis and perpendicular to a plane? Or, from that first split that generated mass, how can we avoid an axis, sure, in some 'random' direction but, still, an axis?
- Steuard 13y ago
  The issue you're running into here is that you're focusing on the description of this physics in terms of particles. That's usually a very convenient perspective, but it tends to have issues when gravity/spacetime is doing weird things (or even in an accelerated reference frame, which is sort of the same thing). What you really want to focus on is the question, "What are the (quantum) fields doing during inflation?" Those fields will typically be in a state with a whole lot of symmetry, and only small, random fluctuations away from that state will lead to perturbations in the CMB. I might be able to frame this in the particle picture, too. The issue is that there wasn't just one quark! There's a whole intense thermal mass of quarks and other particles, and the energies are high enough (and times short enough) that more of them are being pulled from the vacuum and annihilating back into it all the time (this is largely a field-theory statement, I'm afraid). That mass of quarks is what's being pulled apart by inflation. So there's no single special original quark particle that triggers the whole thing. [Disclaimer: I'm not actually a cosmologist, so I welcome corrections on anything I've misstated there!]

coldcode 13y ago

Physics is a strange and wonderful science. The more we learn the more we realize we don't understand. I've always believed that there are features of the the structure of the universe(s) that we have no idea even exist yet. It's like bringing Newton from the past, dropping him in an open field, and telling him he is surrounded by wireless communications. He'd have no clue what that meant. Likewise we are likely surrounded by things we don't have the background yet to recognize.

brlewis 13y ago

http://en.m.wikipedia.org/wiki/Betteridge's_law_of_headlines http://en.m.wikipedia.org/wiki/Betteridge's_law_of_headlines

gottebp 13y ago

I ran across this before the Planck probe data had confirmed what WMAP had found. There is a good write up on the alignment anomaly by theoretical cosmologist Dragan Huterer about it: http://www-personal.umich.edu/~huterer/PRESS/CMB_Huterer.pdf http://www-personal.umich.edu/~huterer/PRESS/CMB_Huterer.pdf Fascinating to see it still causing a ruckus all these years and a whole other probe later.

dhimes 13y ago
This is a really excellent link. Thank you.