12 ms·
WMAP measurements put the age of the universe at ~13.77 billion years, so I was initially perplexed by this part of the article: > The object acting as a lens
by McKayDavis 8y ago
WMAP measurements put the age of the universe at ~13.77 billion years, so I was initially perplexed by this part of the article:
> The object acting as a lens turns out to be an elliptical galaxy located at a distance of approximately 7 billion light years (z = 0.556), while the source is at least 20 billion light years away (z = 3.03).
...but I found this explanation in the Wikipedia article on the most distant known galaxy (GN-z11), which is 32 billion light-years away [1]:
> At first glance, the distance of 32 billion light-years (9.8 billion parsecs) might seem impossibly far away in a Universe that is only 13.8 billion (short scale) years old, where a light year is the distance light travels in a year, and where nothing can travel faster than the speed of light. However, because of the expansion of the universe, the distance of 13.4 billion light years traveled by light from GN-z11 to Earth, called the light-travel distance, has expanded to a distance of 32 billion light-years during the 13.4 billion years it took the light to reach us.
[1] https://en.wikipedia.org/wiki/GN-z11#Notes https://en.wikipedia.org/wiki/GN-z11#Notes
see also:
[2] https://en.wikipedia.org/wiki/Expansion_of_the_universe#Measuring_distances_in_expanding_space https://en.wikipedia.org/wiki/Expansion_of_the_universe#Meas...
- teekert 8y agoThank you, went to the comments to learn this. So the universe actually expands pretty fast then! Faster than the speed of light? Strangely...
- jhoechtl 8y agoWhich makes it then effectivelly infinite?
- mirimir 8y agoIANAP, but I think so. I vaguely recall that early inflationary expansion was very fast. Like several times the speed of light.
- knappe 8y agoNo, not really. One theory is that eventually things will slow and then collapse again. https://en.wikipedia.org/wiki/Big_Crunch https://en.wikipedia.org/wiki/Big_Crunch Taken to the extreme, this expansion and collapse has been happening over and over again in a cyclical fashion. https://en.wikipedia.org/wiki/Cyclic_model https://en.wikipedia.org/wiki/Cyclic_model
- pixl97 8y agoThe shape of the universe currently prevents this. For what we can tell the universe is flat, which means at no point will it collapse on itself, unless something major changes. That said, major changes have happened, around 8 billion years ago expansion appears to have sped up.
- earenndil 8y agoI'm no expert (so correct me if I'm wrong), but from what I'm read, flat, concave, and convex universes are all possibilities and they would all look flat to us because our measurements take place on such a small scale.
- sandworm101 8y agoOur measurements occur across billions of light-years. By comparing redshift agaist the standard candles we measure relative speeds of vastly distant objects. And given the speed of light, we are also measuring what those speeds were billions of years ago. It is a very big ruler.
- roywiggins 8y agoWe've measured the flatness of the universe on the scale of the cosmic microwave background, which is essentially as big a ruler as could possibly exist. https://map.gsfc.nasa.gov/mission/sgoals_parameters_geom.html https://map.gsfc.nasa.gov/mission/sgoals_parameters_geom.htm... https://wmap.gsfc.nasa.gov/universe/uni_shape.html https://wmap.gsfc.nasa.gov/universe/uni_shape.html
- ryanseys 8y agoI think it means that it's expanding and traveling in the opposite direction of us. If we start at the same spot, then both travel in opposite directions at 1 mile/hour, at the end of an hour we will be 2 miles away from each other.
- teekert 8y agoThere is not really a center, galaxies are more like raisins in a rising bread. They all move away from each other with the same relative speeds. At least... Any physicists here to tell me whether or not space-time density get less closer to the edge? I mean... Is there an Edge?
- plazmaphyujin 8y agoThere is no edge. It defies the normal way of thinking but every point in the universe is also the center of the universe. The Big Bang happened at every point and space-time is expanding at every point.
- whatshisface 8y agoThere could be an edge, but it's definitely not within the distance we can see out. The main mind-bender is that there's no need for an edge.
- plazmaphyujin 8y agoWell, not really. The distance we can see out is measured in time and we can very nearly see the Big Bang. We can observe the Universe's Recombination event and it is in every direction we look as the Cosmic Microwave Background. This happened everywhere in existence. If there is an edge to the Universe it is in the fourth dimension when the Universe was a singularity.
- btilly 8y agoThis is a well-known phenomena. The usual image is to consider ants traveling on an expanding balloon. The speed of light is the limit of how fast the ants can walk. The expansion of the universe is the expansion of the balloon. And now you see how two distant ants can be carried away from each other faster than they can walk towards each other. If you understand manifolds and general relativity, this analogy is surprisingly exact.
- mehrdadn 8y agoI've heard of raisins on a cupcake instead (I hate raisins on cupcakes btw), I assume since it's a 3D example. It's meant to show how it's possible for everything to be getting farther away from each other without anything being at the center.
- jandrese 8y agoCupcakes have a center.
- btilly 8y agoI haven't heard the cupcake version. It does have something to recommend it, though raisins don't crawl. So that may make it harder to visualize the difference between how fast you're expanding versus how fast you're moving versus local space. Which is the whole point.
- mehrdadn 8y ago
- UlisesAC4 8y agoSpace still expands lower than light speed, the moment expansions goes faster night skies will be completely dark because other objects' light won't be able to reach our field of vision. I do not remember how that phenomenon is called.
- sandworm101 8y agoNot really. The far edge of our perception can be at lightspeed, but then everything closer would remain slower. So night wont suddenly become dark. We will first loose distant galaxies, but 99.9999 of starlight comes from our own galaxy. By the time that is moving away at lightspeed, the view will be the least of our concerns.
- caprese 8y agoOr the night skies light up completely because there was another big bang somewhere else and the light from that universe cluster just reached us our observable universe may be around an unobservable area whose light hasn't reached us yet
- martin1975 8y agoso a parallel universe somehow interferes with ours? I don't think even most enthusiastic multiverse theorists will be able to grasp that.
- caprese 8y agonot really parallel like alternate dimensions, maybe adjacent to not get distracted by colliqualisms and scifi tropes? just another area in the vast void that also had a big bang which is outside of our observable area right now, but whose light may reach us one day.
- 6nf 8y agoYou might be referring to the Big Rip?
- PopeDotNinja 8y agoYup! There is light moving towards us from the other side of the universe, but we'll never see it because the space between that light is stretching faster than thr light can travel (or something like that). Check out this page on the Observable Universe... https://en.wikipedia.org/wiki/Observable_universe https://en.wikipedia.org/wiki/Observable_universe.
- waterhouse 8y agoI think it expands uniformly, so that, after time t, a distance of x becomes a distance of x * k, with k being very slightly greater than 1. Then there will always exist large enough x to outstrip the speed of light. To illustrate, imagine the expansion factor is, say, 10^-20 per second. Then a distance of 10^30 meters will increase to a distance of 10^30 + 10^10 meters in one second, while light travels at 3 * 10^8 meters per second, so expansion would outstrip lightspeed at that distance. If the expansion factor were 10^-40 per second, then a distance of 10^50 meters would be increasing faster than lightspeed.
- Latteland 8y agoI had to look it up, paraphrasing from the article below, z is the cosmological redshift, indicating the recession velocity of the object. So smaller z values mean closer, large values mean higher, and the farther away it is the faster it is moving away. http://astronomy.swin.edu.au/cosmos/c/cosmological+redshift http://astronomy.swin.edu.au/cosmos/c/cosmological+redshift
- v_lisivka 8y agoSo, for object 13.4 b.l.y. away it took 13.4 b.y. to reach us, but for object 32 b.l.y. away, it took 13.4 b.y. to reach us only? Nice match.