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Why is there a normal galaxy sitting at the edge of the Universe?

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Re: Why is there a normal galaxy sitting at the edge of the Universe?

#191

Post by solstice »

jecel wrote: post #181
nelsonenzo wrote: post #162

Earlier quoted context omitted.

Omg, thank you for this! The balloon model always confused me because I could never understand what was in the middle of the balloon, and why we were on top of it. It's an odd 2d example using an object that is 3d, the balloon. Raisin bread, oh I love thee even more today.

The raisin bread is a 3D expansion in 3D space. So from the viewpoint of a specific raisin the others are moving differently depending on what direction you look and you can use that to determine where the center of the bread is. The balloon is a 2D expansion in 3D space, which is a better analogy for our 3D universe expanding in 4D space. From the viewpoint of a particular dot you see the exact same thing no matter…

Your last point resonates with me. I had neither previously considered where the big bang might have taken place, nor that this would somehow be an erroneous concept. I scrolled through a bunch of disjointed answers on Quora that left me more confused than before. Could you point me to some good resource on that topic?

Re: Why is there a normal galaxy sitting at the edge of the Universe?

#192

Post by dumpsterdiver »

edjrage wrote: post #186
meowface wrote: post #176

Earlier quoted context omitted.

I'm absolutely terrible and uneducated when it comes to math, so I'm not sure exactly what you mean. But if you mean 1/x where x = infinity, then yes, the classical idea of a singularity (such as what's been theorized to exist within a black hole, curving to an infinitely small point) is basically like 1/infinity or dividing by zero. Rovelli hypothesizes this never actually happens and is not physically possible, and…

I'm not terribly educated either, but if you don't mind a minor possible correction, I suppose GP would have meant x = 0, which is the only point where the function would be typically undefined, and the closer x gets to 0, the more f(x) approaches infinity. Conversely, the more x approaches infinity, the more f(x) approaches 0. Also, because of the way these things are usually defined, it doesn't make sense to say x…

> "I really appreciate your comments! If you're interested in hypothesizing about physics, I think it would do you a lot of good to learn at least a bit of math to go with it."

Not disagreeing, I just wanted to suggest that the ideas come first, right? The math simply frames the ideas in a way that we can quantify and discuss, while also providing a "line in the sand" that other ideas must be compatibile with in order to be accepted among other the ideas that have already crossed that line. Those are very important things, but I would suggest that they are merely supporting an original idea that does not require math to intuit.

Re: Why is there a normal galaxy sitting at the edge of the Universe?

#193

Post by marsokod »

tectonic wrote: post #2

Nice gravitational lens observation! We're hoping to use the same technique with the Sun to observe exoplanets by launching a fleet of small satellites to 547 AU (80 billion km / ~3 light days). The craft would sample the distorted Einstein ring around our Sun from that vantage point, then combine and reconstruct an image of the disk of an Earth-like exoplanet up to 100 light-years beyond, at a resolution of 25 kilom…

That's completely mad! I'd love to be part of that.

Re: Why is there a normal galaxy sitting at the edge of the Universe?

#194

Post by not2b »

tectonic wrote: post #2

Nice gravitational lens observation! We're hoping to use the same technique with the Sun to observe exoplanets by launching a fleet of small satellites to 547 AU (80 billion km / ~3 light days). The craft would sample the distorted Einstein ring around our Sun from that vantage point, then combine and reconstruct an image of the disk of an Earth-like exoplanet up to 100 light-years beyond, at a resolution of 25 kilom…

That's four times as far away as Voyager 1 is. I see from the link that it would take 25 to 30 years to reach that distance, and only one target could be observed: we would have to have one particular exoplanet we want to image and go to the right point for the sun to focus the image to.

Re: Why is there a normal galaxy sitting at the edge of the Universe?

#195

Post by s1artibartfast »

morganvachon wrote: post #189
s1artibartfast wrote: post #146

Earlier quoted context omitted.

I don't think your childhood view holds up with contemporary views. My understanding is that 3 dimensional space, as well as time are properties of our local universe. There is no space outside the big bang and between universes if multiple exist

That's exactly what I have such a hard time wrapping my head around: The concept that there is not even a Void outside of the borders of our own universe, that existence itself doesn't, well, exist . The fact that "space" (as we define it) is finite just feels so wrong, so impossible.

To be frank, I totally agree. I don't think our brains can comprehend what existence would mean without 3 dimensions and time.

Re: Why is there a normal galaxy sitting at the edge of the Universe?

#196

Post by cygx »

mekkkkkk wrote: post #74
zemnmez wrote: post #59

Earlier quoted context omitted.

this is because things aren’t ‘moving apart’— space itself is expanding (into what? nobody knows). it’s not that the galaxies are being propelled apart from a force in a particular place either; everything is expanding away from everything else . On the traditional balloon model, the surface of the balloon represents space itself. Those dots on the surface of an expanding balloon are not moving relative to space (the…

Sorry for also asking a space 101 question, but since the fabric of space is expanding, does that mean that things are getting bigger as well? Naively, it would seem that way. In your balloon example, the dots would get bigger.

No, things aren't getting bigger.

Like other gravitational effects, locally, spatial expansion would manifest as a pseudo-force, but be too weak to overcome the nuclear and electromagnetic forces that keep matter bound.

However, Friedmann cosmology is only a large-scale approximation. A more realistic model is swiss-cheese cosmology, which comes with a different metric within the 'holes', and spatial expansion might indeed not act on galactic scales (though I would image it to have an indirect effect as boundary conditions at the edge of the hole have to be matched; I'm no expert on this part of the story, though).

Re: Why is there a normal galaxy sitting at the edge of the Universe?

#197

Post by [deleted] »

meowface wrote: post #137
dumpsterdiver wrote: post #67

Earlier quoted context omitted.

>"space itself is expanding (into what? nobody knows)" I have a terrifying theory on this (granted, the Earth will be long gone). What if the universe is not actually expanding in the sense that it is being propelled by an initial explosion, but instead falling towards a much greater mass - the end of time so to speak, where all mass ends. Considering that gravity is a "weak force", the scale of such a mass makes me…

From my layman's perspective, I think this is plausible, and many physicists seem to agree it's plausible. Maybe another plausible explanation could be the reverse: maybe before the Big Bang, our/the universe was in the state you describe, and the Big Bang is our perception of it "snapping back" and exploding violently outward (aka a white hole). Carlo Rovelli and others propose that black holes actually only appear…

[deleted]

Re: Why is there a normal galaxy sitting at the edge of the Universe?

#198

Post by [deleted] »

meowface wrote: post #137
dumpsterdiver wrote: post #67

Earlier quoted context omitted.

>"space itself is expanding (into what? nobody knows)" I have a terrifying theory on this (granted, the Earth will be long gone). What if the universe is not actually expanding in the sense that it is being propelled by an initial explosion, but instead falling towards a much greater mass - the end of time so to speak, where all mass ends. Considering that gravity is a "weak force", the scale of such a mass makes me…

From my layman's perspective, I think this is plausible, and many physicists seem to agree it's plausible. Maybe another plausible explanation could be the reverse: maybe before the Big Bang, our/the universe was in the state you describe, and the Big Bang is our perception of it "snapping back" and exploding violently outward (aka a white hole). Carlo Rovelli and others propose that black holes actually only appear…

[deleted]

Re: Why is there a normal galaxy sitting at the edge of the Universe?

#199

Post by skissane »

withinboredom wrote: post #172
skissane wrote: post #161

Earlier quoted context omitted.

The problem with dates like that is they are pure best wishes. They might have funding for a demo in 2024 – although it isn't even clear they've got that yet, it sounds like they may just have funding to develop their proposal further. Even assuming the tech demo is successful, it sounds like they don't even yet have a detailed costed proposal for a 2034 launch, and no idea how likely that it will actually get funded…

> Politicians and bureaucrats want immediate results This makes me sad. The entire point of Government is to be an enterprise spanning multiple generations.

The downside of electoral democracy, is if you are only going to be be in power for 5-10 years max, why care about the state of the country in 30 years time, except out of the goodness of your heart? And electoral politics often does a rather poor job of selecting leaders with goodness in their hearts.

Of course, non-democratic systems have their own, equally serious downsides. Consider China: a system which is arguably much better at making long-term investments in public infrastructure than most democratic countries are (witness China's high-speed rail system), but also a system which ruthlessly suppresses dissent and locks up over a million of its citizens in "re-education camps"

Re: Why is there a normal galaxy sitting at the edge of the Universe?

#200

Post by DoctorOetker »

perhaps they look less chaotic because the rays at each point of the the ring when reconstituted was not emitted at the same time, so the picture we computed is a reconstitution of a large spread of time during which movement of the stars in the galaxy blurred substantially giving the impression of a more homogenous and orderly galaxy (a chaotic galaxy at astronomical shutter times might look orderly)
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