Universe Definition and 1000 Threads

Daniel Vasilaky asks do physicists know "how much energy the universe has"? An infinite amount seems absurd - no need for conservation laws and so perpetual motion would be possible. I'd say no to a negative amount also. So it'd be zero (I'd say probably) or a finite, positive amount (maybe)...

I found an article by James Bjorken (https://arxiv.org/abs/hep-th/0210202) which argues that universes with different size would have different physics (like different Standard Model parameters). When applying this reasoning to our own universe, Is this pure conjecture? Or is there some truth...

https://arxiv.org/abs/1803.08928. This is a simple and elegant theory, but there are some things I don’t understand. Why would the anti-universe exist before the Big Bang? From the viewpoint of the anti-universe, isn’t our universe time-reversed? Also, unless the total charge of...

For reference:

(a) We first find that: ##T_A=\frac{P_A V_A}{nR}=\frac{1\cdot 10^5 \cdot 4}{40\cdot 8.314}K\approx 1202.7904 K##, ##\frac{T_B}{T_A}=\frac{\frac{P_B V_B}{nR}}{\frac{P_A V_A}{nR}}=\frac{P_B V_B}{P_A V_A}=\frac{P_A \frac{V_A}{2}}{P_A V_A}=\frac{1}{2}##, ##\frac{T_C}{T_B}=\frac{P_C...

I tried setting the Universal time T = Tp as when T = 0 there was no universe and thought Tp would be the first instance of the universe, but I still can't figure out how equation (3.1.3) implies that M0 = Mp/2

The following is the closest chart to what I want that I could find. https://map.gsfc.nasa.gov/media/990350/990350b.jpg This chart has four curves, but only two of them has Omega_m + Omega_Lambda = 1. I would like to see a curve (of several) which expands and then contracts, like the...

Global Newtonian mechanics seems to be compatible with 1) Hubble's law, and 2) the cosmological principle: take a vector space, set the velocity of a galaxy at x to be v=x, where x is the position vector. Then from any galaxy, the other galaxies seem to go away with velocity v2-v1 = x2-x1. That...

The integration tool I am using is https://www.symbolab.com/solver/definite-integral-calculator . The following are the values of the five variables in the Friedmann equation with references of sources. I have also defined single letter variables I used for convenience...

I am trying to understand / visualise, recognising that the Big Bang is not thought of as an explosion, how the Universe could have come into existence as a 'point' but came into existence 'everywhere'? Is it a concept that such a point was then everywhere, and that the mass of the Universe, as...

There are some theoretical processes (like vacuum decay in quantum field theory) that could change the physical constants of the universe. Similarly, in inflation theory, various models predict that multiple regions that would stop inflating would become "bubble universes" perhaps with different...

Hello, this is my first post here. I have a couple questions regarding the Gott-Li model of a self creating universe, proposed in "Can the Universe Create Itself?", Phys. Rev. D 58, (1998). https://doi.org/10.48550/arXiv.astro-ph/9712344 First, I should disclose that I am an amateur and may...

We know that the large majority of galaxies we see can never be reached. We know in 100 billion years we will lose sight of any galaxy outside out local group (which will itself merge into one big galaxy). But what is the maximum distance you could theoretically go if you made it your #1...

If experiments were conducted with a particle accelerator in a distant space from Earth or even our galaxy somewhere in the universe would the results change? I.e finding different elements ect..

If the universe is "expanding", does that mean less dense, or does that mean there are measurable boundaries? With very far away galaxies that stay "alive" for a "short" time, is most of the very distant observable-from-earth universes now gone?

how could something infinite expand? expandig mean geating bigger but if its already infinite how could it get bigger

What does the universe expands into? Its a really big question that has been stuck in my head

References (1) https://www.physicsforums.com/threads/what-is-the-probability-that-the-universe-is-absolutely-flat.971984/ (2) https://www.physicsforums.com/threads/calculating-the-probability-that-the-universe-is-finite.1011826/ Suppose the Friedmann equation is used to analyze two models. (1)...

This is just a rough estimate of what a simple bock universe might be to an observer in the red worldline on the left side, and what it is to an observer in one of the blue worldlines in the graph on the right side. In the graph on the left side, two blue objects moved past the red object very...

I may be way off, but at some point in the past I understand there was super expansion where the universe expanded faster than the speed of light. If matter expanded with it it's an example of matter in separate areas moving apart faster than the speed of light. If it didn't the universe has...

The entire universe has a single very complicated wave function ##\psi##, and if we plug this into the schrödinger equation will that mean we live in a deterministic universe? (whatever happens and will happen was already predetermined at the time of the big bang. the initial conditions of the...

Reference https://www.cosmos.esa.int/documents/387566/387653/Planck_2018_results_L06.pdf I note that the use of Gaussian probabilities is mentioned many times in the reference. However in many discussions via posts in many threads, there seems to be a consensus that the distribution is...

Hello, can somebody help me out please? just watched this video so far understood but if motion changes the now frame its logic if the alien cylcles to the guy sitting that his time is slower and the guys time will be in the future (time delitation). but when the alien is moving away how can...

My source for Ωk and H0 is https://www.cosmos.esa.int/documents/387566/387653/Planck_2018_results_L06.pdf , page 40, equation 47b. Ωk = 0.0007. Page 15 equation 13 has H0 = 67.27 km/(s Mpc). The formula I used is R = (c/H0) (1/Ωk)1/2 . ( I did have a reference for this, but I misplaced it, and I...

I make use of the 100,000 stars online visualization (https://stars.chromeexperiments.com/) to gain an idea of where stars are in relation to each other but the UI is not designed for anything but simple interactivity. It helps with plots and guestimating spaceship travel times, but it's tedious...

Are there any other ways for the entire universe to die other than freeze death, big crunch, vacuum decay and big rip?

(See illustration) Object A is moving, to the right, really fast towards object B on the x axis. At (0,0) they meet. There are two rocks next to each other ahead of the speeding object A. The two rocks are shown as world lines red and green as they would exist for each observer. Assume that...

I've read that ESA's Gaia space observatory has created the "richest map of our galaxy (and beyond)" https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_creates_richest_star_map_of_our_Galaxy_and_beyond Meanwhile, it's been widely reported tat the "The Dark Energy Spectroscopic...

Greetings, all. Please forgive my ignorance, but this is a question which has been on my mind for many years: What space does the universe occupy? To clarify what I mean: I'm in a building which is in the city of Hillsboro, which is the county of Washington, which is in the state of Oregon...

ok so I've been curious about this theory for a while but just haven't started digging into it until tonight : if energy creates gravity no matter how small, couldn't the universe be infinite and coincide with Newtons second law of thermodynamics; if when the heat death of the universe happens...

Without suggesting that there actually is a massive spherical shell enclosing the universe, I am trying to explore whether the observed expansion of the universe would be the same if there was a spherical shell with a diameter greater than the universe, with some arbitrary mass producing a...

Is energy really not conserved in a constantly expanding universe?

[Moderator's note: Spin off from previous thread due to topic change.] It's my understanding that Edwin Hubble used the Hooker telescope to measure the red shift of galaxies only within the Local Group of galaxies to determine that the universe was expanding. As we see here...

Does the Earth's orbit get very slightly larger over long periods of time due to the expansion of the universe? If so does it stay at the slightly larger distance or somehow does the energy to go back to the earlier orbit go somewhere else and if so where? If the orbit does not get slightly...

Hi If the universe is expanding, then why does the Andromeda Galaxy approach us? Does not it contradict Hubble's law?

Will the universe keep expanding faster and faster for all eternity or is there a limit to how fast the expansion will get?

Hey all, I am looking forward to knowing some software/sites that show an extensive collection of the DSOs. I want it to be 3D, but it can also be 2D. I know/tried some of these, Stellarium - 2D Celestia - 3D https://www.legacysurvey.org/viewer#IC 2095 - 2D Gaia Sky (I have tried to download...

Are there exactly as many negative charges as positive, in the universe? If so, how can we be sure, and if not then what is the difference and why? If there is an assumption of charge neutrality at time zero, then why? Is there a rationale behind that or just an unsupported supposition?

Googleing this question yields answers that don't really seem to address the core of my question. I apologize if I just haven't been able to see how answers are applicable, and would greatly appreciate any insight. Imagine a universe consisting of only our sun. no planets, no galaxies...

We get the following picture of the formation of inhomogeneities: Initially, all eternally existing fields (possibly fermionic-lepton-quark-DM-field and GUT-field) lived in a vacuum state --- no real particles (only virtual ones), just fluctuated (##\left\langle\Delta E\right\rangle = 0##...

Consider two observers, Alice and Bob, standing on the Earth together with synchronized clocks. Bob asks Alice, “Is this now?” to which Alice replies, “Yes, it is”. They are clearly both in the present moment. Bob climbs a mountain and some time later, due to the lower gravitational field...

Hi, All cosmological models with a non-zero cosmological constant will approach a de Sitter universe in the far future. In theory this can means that the most basic group of particle physics should be the de Sitter rather than Poincaré. Mass is a Casmir operator of the Poincare but not of the...

On page 353 of Schutz's textbook he writes the following: So it seems that the ether is replaced by a "homogeneous perfect fluid". It seems the medium which fills the universe is not ether but "homogeneous perfect fluid". But in that case what characteristics did the proposed ether have that a...

How do gravitational waves in spacetime stretch and compress solid matter such as the LIGO experiment. I ask this because the expansion of spacetime of the Universe doesn't seem to have any effect on the small scale ie the solar system.

Cyclic models for reference. I will take simple Big Bounce as an example of what I have in mind. In Big Bounce there periods of expansion and periods of contraction which result in a never-ending series of Big Bangs. However if Universe is infinite in extent this would require infinite amount...

Among other things, inflation explains the horizon problem, as to why even though the proper distance between two antipodal points on the last scattering surface is greater than the horizon distance, and therefore causally disconnected, yet the two points have the same temperature. So is this...

Hello, I am a 15 year old who has done research around the topic of why the universe is expanding at an accelerating rate, and how it will come to an end. After years of thought (since I was 11) I have come up with my hypothesis that time itself is accelerating and slowing down, and has been...

I see much confusion about the "origin" of the universe. When discussing what caused the big bang, we need to describe the conditions of the universe before the big bang. For me, the big bang occurred in the universe. The universe existed prior to the big bang and provided the energy to fuel...

When trying to explain from where did all the laws come from, John Wheeler proposed the anaphorism of "Law without law". He proposed that at the "beginning" there were no laws whatsoever, only pure chaos, and that they emerged from randomness and chaos when our universe was created. In his own...

In the standard framework of ideas about cosmology, is it possible to have a universe that is infinite in extent?