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A new Einstein cross is discovered

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Re: A new Einstein cross is discovered

#51

Post by happy-go-lucky »

panarky wrote: post #21

> This study, which has combined images from the Hubble Space Telescope with spectroscopic observations from the GTC, has confirmed the existence of a new example of a gravitational lens What is the "GTC"? The article doesn't say. It appears to be the Gran Telescopio Canarias. https://en.wikipedia.org/wiki/Gran_Telescopio_Canarias

The article is provided by the Instituto de Astrofísica de Canarias and this institute operates the Roque de los Muchachos Observatory. One of the telescopes at the site is Gran Telescopio Canarias (GranTeCan or GTC).

https://en.m.wikipedia.org/wiki/Roque_de_los_Muchachos_Obser...

Re: A new Einstein cross is discovered

#52

Post by earenndil »

pixl97 wrote: post #43
knappe wrote: post #39

Earlier quoted context omitted.

No, not really. One theory is that eventually things will slow and then collapse again. 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

The 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.

I'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.

Re: A new Einstein cross is discovered

#53

Post by saagarjha »

rough-sea wrote: post #50
mcguire wrote: post #47

Earlier quoted context omitted.

Infinitely large? My understanding was that the universe originated as a point, inflated a great deal, then began expanding at a rate that has changed over time. As a result, the universe would be significantly larger than the visible universe, but would have a finite size. (A finite size, but no boundaries. The universe is a sphere whose circumference is everywhere but whose center is nowhere. Cue Borges music.)

It’s a common misunderstanding of the Big Bang. There is not a point where the universe originated. Rather everything was just closer together. Imagine traveling back in time - you would see galaxies move closer and closer - until everything was super dense and hot - like the center of the sun but everywhere.

Isn’t the natural extension of things being “closer together” that they were at a singularity at some point (the Big Bang)?

Re: A new Einstein cross is discovered

#54

Post by rkagerer »

pixl97 wrote: post #43
knappe wrote: post #39

Earlier quoted context omitted.

No, not really. One theory is that eventually things will slow and then collapse again. 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

The 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.

Those darn flatspacers

Re: A new Einstein cross is discovered

#55

Post by rough-sea »

saagarjha wrote: post #53
rough-sea wrote: post #50

Earlier quoted context omitted.

It’s a common misunderstanding of the Big Bang. There is not a point where the universe originated. Rather everything was just closer together. Imagine traveling back in time - you would see galaxies move closer and closer - until everything was super dense and hot - like the center of the sun but everywhere.

Isn’t the natural extension of things being “closer together” that they were at a singularity at some point (the Big Bang)?

Nope. The universe is infinite, according to the model. We see observe galaxies speeding away from us in every direction - and it seems unlikely that the earth was the exact center of the Big Bang.

Re: A new Einstein cross is discovered

#56

Post by Qwertystop »

rough-sea wrote: post #55
saagarjha wrote: post #53

Earlier quoted context omitted.

Isn’t the natural extension of things being “closer together” that they were at a singularity at some point (the Big Bang)?

Nope. The universe is infinite, according to the model. We see observe galaxies speeding away from us in every direction - and it seems unlikely that the earth was the exact center of the Big Bang.

Wouldn't that also be consistent with a finite universe as long as the distribution of galaxies is not biased towards or away from the edge, as long as the edge itself is beyond the observable part of the universe? We wouldn't have to be in the exact center, just not too close to the boundary.

Re: A new Einstein cross is discovered

#57

Post by sandworm101 »

earenndil wrote: post #52
pixl97 wrote: post #43

Earlier quoted context omitted.

The 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.

I'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.

Our 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.

Re: A new Einstein cross is discovered

#58

Post by plazmaphyujin »

teekert wrote: post #35
ryanseys wrote: post #29

Earlier quoted context omitted.

I 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.

There 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?

There 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.

Re: A new Einstein cross is discovered

#59

Post by martin1975 »

caprese wrote: post #49
UlisesAC4 wrote: post #40

Earlier quoted context omitted.

Space 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.

Or 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

so a parallel universe somehow interferes with ours? I don't think even most enthusiastic multiverse theorists will be able to grasp that.

Re: A new Einstein cross is discovered

#60

Post by mordero »

rough-sea wrote: post #55
saagarjha wrote: post #53

Earlier quoted context omitted.

Isn’t the natural extension of things being “closer together” that they were at a singularity at some point (the Big Bang)?

Nope. The universe is infinite, according to the model. We see observe galaxies speeding away from us in every direction - and it seems unlikely that the earth was the exact center of the Big Bang.

| and it seems unlikely that the earth was the exact center of the Big Bang.

Wouldn't it be more accurate to say that everything was at the exact center of the Big Bang? Assuming it started from a singularity (which can't really be known), everything was in the center.

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