These are brilliant, thank you. The only issue I have with them is;
Surely these deep 3d maps are extremely warped? The light from the closer points is far younger than the light from the further points. Meaning that the further points have moved their position since, in relation to the closer points.
These maps must be like long-exposure drag-effects, not a snapshot of current state.
That was a very helpful simile, thanks.
1 Like
Stephen Hawking backpedaled on his statement that âBlack holes donât existâ, just FYI.
Whilst itâs true that the âtraditionalâ Great attractor can be explained in terms of the galactic flow around our own super cluster, I was sure Iâd read about new evidence that indicated an even larger attractive force in the direction of the Pisces-Perseus Supercluster.
Iâm going mad trying to find information on it now though!
1 Like
Not really.
Expansion simply means a change in the curvature of spacetime. It can be flat or positive or negative curvature and still expand. It isnât expansion in the sense of pushing things away from a central point but expansion in the sense of accumulating more geometry everywhere. Local motions are pretty small and insignificant. Expansion is not a hypothesis. It has been an observation fact since Hubbleâs time.
This motion is not local (in cosmology, local encompasses some truly large sizes). What this means is that the distance between us and something else is decreasing and that can only be gravitational.
Iâm gonna guess someone let the vacuum out of Trumpâs head.
1 Like
There is no point of origin. If we smashed the universe down to 2 dimensions, itâs like the surface of an expanding balloon. Everything is expanding away from everything else, and there is no central point out from which the expansion is happening. The space between everything is getting bigger, not that everything is moving away from the center.
One thought I had would be that the great attractor could be like a âthickerâ part of the balloon that doesnât expand quite as fast as everything else. That could look to us like a pull towards the attractor, when in actuality itâs just the expansion in the vicinity of the attractor being slower than in the rest of the universe.
But thatâs entirely armchair speculation, and Iâm almost certainly completely wrong for obvious reasons that a physicist could explain to me. I welcome any edification.
True dat.
And I am also likely just flat out wrong, but I didnât think inflation was region specific? Iâd love to read some papers.
My precise assumption was that this wasnât the case. But assumptions and all that 
Hey, from my very cursory, mostly passing knowledge of dark energy and just a few of the possible mechanisms, thereâd be no way for the expansion caused by dark energy to have any kind of âlumpinessâ.
So, Iâm just really shooting off at the mouth here.
WRT the locality of inflation, Iâve heard a few cosmologists describe multiverse theories where instead of universes being separated by dimension, all the universes are âlocalâ. Basically, theyâre only separated by distance, and thereâs no transition between universes. The thing that makes the next universe over separate from ours is the fact that itâs so far away that cosmic inflation makes it inaccessible. It isnât separated strongly because if thereâs an observer half-way between earth and the next universe over, theyâd be able to see both earth and parallel earth, but not parallel-parallel earth one universe over from themselves.
1 Like
Inflation is a different thing and refers to a specific very tiny period of time right after the big bang when the expansion was extraordinarily rapid before it settled down to the current situation. Complicated quantum field theory reasons.
The fundamental assumption of cosmology (which the data mostly supports) is that on the largest scale (= much larger than superclusters) all local motions average out and what youâre left with is a universal expansion.
Inflation is still moderately speculative and you can find a lot of models.Most of them have some lumpiness that gave rise to large scale structure.
4 Likes
Dark energy is not the only culprit for expansion. What it does is cause the expansion to accelerate but there would be expansion even without it.
1 Like
I appreciate it, and as a novice love the answers.
No probs. If I canât make a living at it, I can at least share the wealth. Thanks for being interested. Most people arenât.
5 Likes
+1 for sharing. I find cosmology fascinating, but I canât math soâŚ
To put things in perspective, this is approximately 1/50th the speed of light: 670,616,629 mph/14,000,000 mph = 47.9. Out of curiosity, one day I tried to calculate the relative speed of an individual on the earthâs equator with respect to center of the galaxy. Letâs see:
- The circumference of the Earth at the equator is 24,902 miles.
- It takes approximately 24 hours for the earth to complete on rotation.
- Therefore, the linear velocity of an individual on the earthâs equator is approximately 24,902 miles/24 hours = 1038 mph.
- Earth travels appx. 584 million miles in the course of a year. This equates to 584x10^6 miles/(365 days x 24 hours/day) = 66,666 mph.
- Ok, got lazy and decided to google âspeed of solar system around galactic centerâ and got a linear velocity of 514,000 mph. This is somewhat larger that an earlier estimate of 490,000 mph provided by Scientific American in 1998:
http://www.scientificamerican.com/article/how-fast-is-the-earth-mov/ - The Scientific American article above estimates that the Milky Way is moving toward the Great Attractor a speed of 1,000 kps or 2 million mph. This is smaller than the most recent estimate of 14 million mph.
- However, considering that the Milky Way is 100,000 light years or 6 x 10^17 miles across, I consider this to be an almost imperceptible drift since it would take appx. 5 million years to traverse the Milky Way even at the worst case speed of 14 million mph.
- Lesson: It sounds like a big number, but itâs really all relative.
- Just for fun, I calculated that it would take 346 days to walk around the earth at the equator at a speed of 3 miles per hour. Therefore, one could walk around the earth appx. 5.3 million times in 5 million years.
2 Likes
Alright imagine this: you get a large round bath made of ebony. And itâs conical.
1 Like
But⌠Would you walk 500 miles, then walk 500 hundred more, just to be the man who walked 1000 miles to fall down at my door?
3 Likes
Adrian Berry, 4th Viscount Camrose, author of âCrossing the universe through black holesâ? I am delighted to learn that he is still around.
âneither (X) or (Y)â
Poorly written and apparently not proof read so I guess it should be ânorâ (Y) otherwise it makes no sense.
Stephen Hawking backpedaled on his statement that âBlack holes donât existâ, just FYI.
Yup, Iâm well aware. I wasnât referring to that event at all. They were first postulated in 1790 and their existence (or rather the general acceptance of) has been argued back and forth since that time. Hawking is only one of many whom have participated in the debate.
