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How did we get ahead of the waves? Or did they wrap around a curved universe and come back to us?

by nsxwolf 13y ago

dangrossman 13y ago
Any echo of the big bang would be coming from all directions and going in all directions. It did not leave from here and come back, it left from some other point in the universe and is just reaching us. /not-a-scientist
- contulluipeste 13y ago
  That's how the current estimation of the universe age was made (only it was about the background space temperature of about 4 Kelvin). This time, by measuring magnetic waves they seek to find a (even slight) difference in expanding directions. /not-a-scientist-either
ggdG 13y ago
IANAC [1], but here's my Wikipedia-level 2 cents: (Warning: leaky metaphors ahead!) We stayed ahead of the primordial gravitational waves [2] for so long because the expanding universe went through an "inflation" period: in a very short time - immediately after the Big Bang - spacetime expanded at a rate that was many orders of magnitude too big for phenomena like light or gravitational waves to catch up to. It leveled off quickly to a more gentle rate of expansion [3], but in the meantime the universe has gotten so big that even its current age of 13.7 billion years isn't enough for us to be able to observe every object. Many objects are so far from us that it will take much more than 13.7 billion years for their photons to reach us. And no matter how distant the objects that will 'come into view' in the future, the light that appears the most distant to us will always be the cosmic microwave background radiation. So here we find ourselves, Earthly observers, sitting in the center of a sphere with an apparent radius of 13.7 billion lightyears - called the observable universe - at the edge of which we can see the immediate aftermath of the Big Bang. No one knows how much bigger the total universe is w.r.t. to the observable universe. It's hard to find out because we have no causal relation to anything outside the observable universe. A safe bet IMHO (given past experiences in the history of cosmology) is this: the entire universe is way, way, way bigger than the observable universe. [1] I Am Not A Cosmologist [2] and also of the cosmic microwave background radiation [3] sub light speed, at least for distances within the observable universe
- xenophonf 13y ago
  Just a slight correction: The distance from Earth to the edge of the observable universe is 46 Gly, not 13.7 Gly, because of the metric expansion of space.
  - ggdG 13y ago
    True. The light has been traveling for "only" 13.7 billion years, but meanwhile the space between origin & destination kept expanding. That's why I wrote about an apparent radius, but on further thought I no longer believe that the travel time will reflect in an apparent distance. It's the amount of redshift that will result in a calculated proper distance.
- vl 13y ago
  In my layman understanding current prevailing theory is that acceleration of expansion will reduce observable universe, and as consequence there is basically no question of "size beyond observable universe" - there is no possible interaction with it and as such it doesn't exist. http://en.wikipedia.org/wiki/Accelerating_universe http://en.wikipedia.org/wiki/Accelerating_universe
  - lutusp 13y ago
    > In my layman understanding current prevailing theory is that acceleration of expansion will reduce observable universe, and as consequence there is basically no question of "size beyond observable universe" ... Yes, but that was true before the Dark Energy discovery. It's predicted to become much worse in the far distant future because of the acceleration caused by Dark Energy, and eventually there will be comparatively small island universes -- galactic clusters -- that will remain gravitationally bound far into the future, after the remainder of the universe has receded from view. This is because galactic clusters are below the threshold for being affected (i.e. torn apart) by Dark Energy. > there is no possible interaction with it and as such it doesn't exist. Yes to the first, no to the second. At present, we cannot see beyond a certain time horizon, but cosmological curvature measurements take this invisible mass-energy into account even though it's not directly observable. Our present conjecture that the universe is infinite in size (based on curvature measurements) obviously implies a universe most of which isn't visible, but all of which affects the measurements.
deleted 13y ago
[deleted]
laumars 13y ago
Think of the universe like a low resolution digital image. When you zoom in, every part of the larger image is still part of the smaller image. And so the universe expanded in a way that every part of the universe would be an original starting point from before the expansion. Thus these waves would be coming from all directions rather than just being "ahead" or "behind" us.

How did we get ahead of the waves? Or did they wrap around a curved universe and come back to us?

by nsxwolf 13y ago

How did we get ahead of the waves? Or did they wrap around a curved universe and come back to us?

Any echo of the big bang would be coming from all directions and going in all directions. It did not leave from here and come back, it left from some other point in the universe and is just reaching us. /not-a-scientist

contulluipeste 13y ago
That's how the current estimation of the universe age was made (only it was about the background space temperature of about 4 Kelvin). This time, by measuring magnetic waves they seek to find a (even slight) difference in expanding directions. /not-a-scientist-either

ggdG 13y ago

IANAC [1], but here's my Wikipedia-level 2 cents: (Warning: leaky metaphors ahead!) We stayed ahead of the primordial gravitational waves [2] for so long because the expanding universe went through an "inflation" period: in a very short time - immediately after the Big Bang - spacetime expanded at a rate that was many orders of magnitude too big for phenomena like light or gravitational waves to catch up to. It leveled off quickly to a more gentle rate of expansion [3], but in the meantime the universe has gotten so big that even its current age of 13.7 billion years isn't enough for us to be able to observe every object. Many objects are so far from us that it will take much more than 13.7 billion years for their photons to reach us. And no matter how distant the objects that will 'come into view' in the future, the light that appears the most distant to us will always be the cosmic microwave background radiation. So here we find ourselves, Earthly observers, sitting in the center of a sphere with an apparent radius of 13.7 billion lightyears - called the observable universe - at the edge of which we can see the immediate aftermath of the Big Bang. No one knows how much bigger the total universe is w.r.t. to the observable universe. It's hard to find out because we have no causal relation to anything outside the observable universe. A safe bet IMHO (given past experiences in the history of cosmology) is this: the entire universe is way, way, way bigger than the observable universe. [1] I Am Not A Cosmologist [2] and also of the cosmic microwave background radiation [3] sub light speed, at least for distances within the observable universe

xenophonf 13y ago
Just a slight correction: The distance from Earth to the edge of the observable universe is 46 Gly, not 13.7 Gly, because of the metric expansion of space.
- ggdG 13y ago
  True. The light has been traveling for "only" 13.7 billion years, but meanwhile the space between origin & destination kept expanding. That's why I wrote about an apparent radius, but on further thought I no longer believe that the travel time will reflect in an apparent distance. It's the amount of redshift that will result in a calculated proper distance.
vl 13y ago
In my layman understanding current prevailing theory is that acceleration of expansion will reduce observable universe, and as consequence there is basically no question of "size beyond observable universe" - there is no possible interaction with it and as such it doesn't exist. http://en.wikipedia.org/wiki/Accelerating_universe http://en.wikipedia.org/wiki/Accelerating_universe
- lutusp 13y ago
  > In my layman understanding current prevailing theory is that acceleration of expansion will reduce observable universe, and as consequence there is basically no question of "size beyond observable universe" ... Yes, but that was true before the Dark Energy discovery. It's predicted to become much worse in the far distant future because of the acceleration caused by Dark Energy, and eventually there will be comparatively small island universes -- galactic clusters -- that will remain gravitationally bound far into the future, after the remainder of the universe has receded from view. This is because galactic clusters are below the threshold for being affected (i.e. torn apart) by Dark Energy. > there is no possible interaction with it and as such it doesn't exist. Yes to the first, no to the second. At present, we cannot see beyond a certain time horizon, but cosmological curvature measurements take this invisible mass-energy into account even though it's not directly observable. Our present conjecture that the universe is infinite in size (based on curvature measurements) obviously implies a universe most of which isn't visible, but all of which affects the measurements.

deleted 13y ago

[deleted]

laumars 13y ago

Think of the universe like a low resolution digital image. When you zoom in, every part of the larger image is still part of the smaller image. And so the universe expanded in a way that every part of the universe would be an original starting point from before the expansion. Thus these waves would be coming from all directions rather than just being "ahead" or "behind" us.