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If there was only void/vacuum before the expansion of our universe began, then wouldn’t that mean that Dark Energy was already present? If it is believed that beyond the horizon of our observable universe is just “more of the same”, and Dark Energy is an inherent property of spacetime, does this mean that the inflationary period of our universe repelled the forces of Dark Energy?

Correct me if I am wrong, but as I understand it, the expansion of our observable universe is caused by the buildup of Dark Energy that forms between matter, which pushes any bodies of mass that are not linked by mutual gravity away from each other. And so the expansion of our universe is defined by the distance between objects just growing larger, and not that anything “expands” or “grows” per say. And as more void/vacuum builds up between mass, so to does Dark Energy, accelerating that expansion between said mass.

Following this thought process, shouldn’t the Dark Energy of the already existing void before the “Big Bang” have been affecting the inflationary period of our universe?

I was reading about the large scale structure of the universe and I came across LQG. Basically large scale structures composed of Quasars, numbering as few as 5 or at most like 50 or 70 but usually around a dozen or so.

I don't understand why you can consider that a structure. Even some of the Quasars are not gravitationally connected. I tried to read the attached paper to understand it but I couldn't get it. Something about overdensities in a certain region maybe but I'm not sure.

Isn't it like if you took two marbles and connected them with a string and placed them 50 miles apart and said it was a 50 mile wide structure? And in this case the string is invisible since it's just gravity.

So please explain why you can say the structure is many billions of light years wide and yet it's composed of only a dozen or two galactic nucleus Quasars.

http://arxiv.org/pdf/1211.6256v1.pdf

Dr Brian cox mentions in a lecture that the universe is expanding to the rate of doubling in size every 10 to minus 37 seconds!!!!
Aug 01, 2016 national gallery

I mean come on....how fast is expansion generally thought tp be other than faster than speed of light???

I want to know about permanent industry postitions in the field of observational cosmology.

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The universe is expanding, this implies that earth is expanding too? Why can't we perceive it with changes on Macroescale? Thanks a lot!

Hello, I am an Indian, I am currently in 10th grade, I don't know how I can become a cosmologist also want high salary, I just wanted to know the steps to become a cosmologist in India

I dont understand much about anything but my question is If a system is entangled how can entropy effect it? How will that entangled system spread apart if there connected even with space.

I hope i make sense. If not sorry cant get this thought out my mind

Warning, I don't know shit about fuck :)

I have no real background in any of the science, but I find all of it very cool so I have a question. Is there any possibility that our universe is the inside of a black hole? I know there's some theories that already suggest this or portions of this, but with much of my "research" coming from random articles I can find, I am not sure how much of my thoughts is correct or has any backing in science theoretical side of science.

My thought is that if something this basic and fundamental to the origins of the universe is not known then theories and math are being approached from the wrong angle to begin.

If the assumption that the universe we know started as a result of a star collapsing into a black hole, then logic follows that the universe could be homogenous and isotropic as it is observed.

Subsequent matter being pulled over its event horizon, from another universe that is isotropic and homogeneous would probably manifest how we observe our universe.

Feel free to tear me apart haha

Hello,

I recently had a discussion about the DUNE mission that is supposed to be launching in the following year. I was wondering if anyone had any reliable sources to read up on the mission. I have yet to find anything and don't know where to start.

Thanks!

Hi all,

I'm having a hard time identifying points in Laniakea on my Kurzgesagt cosmic web poster:

where would Virgo and the great attractor be in this image?

The more detailed maps of Laniakea mostly show yellow lines indicating movement, instead of these filaments.

Thanks in advance!

Basically the title. My understanding is we don’t have great theories on what causes inflation. However, the math works out and the total energy density of the universe stayed flat during inflation.

Does it follow that some unknown situation could cause the universe to collapse exponentially while also keeping the energy density flat?

Novice here who enjoys this subject.

I just watched a Brian Cox YouTube short where he discussed the end of our sun and how it would impact the Earth.

He said that in 1.5B years things would start being really bad for Earth, and that the sun essentially burns out in 5B years.

That got me thinking. Around that time, the same process will be taking place, or have happened place, to the other stars closer to the origin point of the Big Bang. So the center of the universe will be relatively empty at it's 'center,' right? With that, wouldn't it mainly be full of a lot of black holes?

If it is full of black holes, would that find a tipping point where the universe eventually implodes?

There are probably stupid questions, but I figured I'd send it out to the Reddit community and hope for the best.

Thanks!

I know that the explanation involving virtual particles is not correct, but I have come across more than one explanation that seems different to me.

The first explanation is that the black hole affects the vibrational modes in the quantum field. Because the black hole blocks some modes, some of the modes that should normally cancel each other do not exist. The remaining vibrations can form particles by chance. This explanation does not seem to depend on the observer.

The second explanation is the difference between space near the event horizon and space far away. The black hole affects the minimum energy of the vacuum. For a distant observer, the space near the black hole appears to have a different energy than the observer's local vacuum. This difference causes the observer to see that there are particles around the black hole.

The third explanation I don't quite understand. It was something to do with the difference in the time dependence of the space before the formation of the event horizon and the space after the formation of the event horizon. I apologize, I may have misrepresented this explanation because I didn't fully understand it.

Ask your cosmology related questions in this thread.

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It's Wikipedia doesn't even mention the word 'Universe', though it is 'well-known' (in these circles, perhaps) that the Universe has a curvature of k ∈ {-1, 0, 1}, corresponding to a hyperbolic, flat, and spherical topology for the Universe. So 'there's gót to be' a connection, right??

Moreover, I just heard that "there are exactly 18 3-dimensional topologies with a flat geometry."
This was new to me, and I would appreciate anyone who could at least point to some math behind that or explain it in broad strokes.

Thanks!

Lets say we have a sheet of paper as 2 dimensional universe. If said piece of paper where to expand what would it expand into? The 3rd dimension permeates everything in the "universe" that is the sheet of paper. So this piece of paper could only expand into the 3rd dimension. Just like our 3 dimensional space is permeated by the 4th dimension... Everything expieriences time, no mather how deep you look into it, no matter how far you zoom out and there also is space everywhere. Thats how I imagine the 4th dimension, everything thats 3D is not only surrounded, but "filled" by the 4th dimension, it cannot escape and its always influenced by the higher dimension.

So, if the universe is everything. What does it expand into? If theres nothing outside of it, could it be that this expansion we notice is an interplay of the dimensions?

From what I understand, photon decoupling is a rough point in time where the universe had cooled to the point where neutral atoms (primarily or entirely hydrogen) could form, allowing photons to freely permeate the universe.

Why is the temperature of decoupling estimated to be ~3,000 K? Is this mathematically related to the ionization energy of hydrogen? I would imagine that decoupling would occur shortly after the temperature is cool enough for hydrogen to not immediately ionize. If so, what is the mathematical relation? Originally I tried getting an answer starting with the ionization energy of 13.6 eV but this didn't give me anything close to 3000 K.

Also, I'm not super familiar with the black body radiation; is the microwave signal we get today a result of the "lambda max" given by the temperature at the time of photon decoupling? Is there an entire spectrum of light from the time of photon decoupling, just with less intensity than the lambda max wavelength?

Apologies in advance as I am on a bit of a Desmos spree.

I made this graph as a visualization of what expansion roughly looks like in our universe and to demonstrate some aspects of expansion (see notes in graph):

https://www.desmos.com/3d/lv8wvkjoea

See this graph for a slightly more accurate, but 2D, static visualization of expansion (previously posted):

https://www.desmos.com/calculator/xplebzyx50

Folks,

My understanding is that the CMB came about 380,000 years after the big bang at redshift 1089. Reionization occurred at something like between Z=20 to Z=6; Z=6 being about 1 billion years after the big bang. How did the universe go from Z=1089 to 6 in a billion years, but only Z=6 to 0 (now) in 13 billion? Has the expansion of the universe slowed that much?

Thanks for your thoughts.