Universe Definition and 1000 Threads

Is a new article, btw June 2, 2015 Experiment Provides Further Evidence That Reality Doesn't Exist Until We Measure It http://www.iflscience.com/physics/measurement-rules-quantum-universe http://www.sciencealert.com/reality-doesn-t-exist-until-we-measure-it-quantum-experiment-confirms any...

Anyone have any insight concerning the latest research underway at Heidelberg University... concerning the "smaller than once thought" earliest stars? Any thoughts on why these 'smaller than once thought stars' also contain carbon, when at this early stage of star formation in a very young...

I'm a retired geologist ... Know little about cosmology or quantum physics so will defer to others. Please excuse my rambling question. Something has always 'made me wonder' about the potential fate of the Universe. Almost all models predict either an infinite Universe or a Universe that...

Hi, Where can I find a database with the mass distribution and its movement in the well-known universe? Best wishes, Jens

I have a question :x Technically, particles, like photons, which don't interact with the higgs field travel at the speed of light. wouldn't the absolute minimum speed limit be something that interacts infinitely with the higgs field?

Dear PF Forum, Sorry if I ask again, because I want a detailed information. Does the universe has a frame of reference? Two twins. A stays, B "travels". (Travel here is confusing, B will say I stay and A travels) and B "turns around" and come back. B ages more slowly then A. Q1: Why? A1...

I'm 13, so I was reading Discover and I read something about a "block universe" and I thought it was a bunch of hogwash... here is how I see it... Time is the same for everybody its just how people perceive it that makes people think its an illusion... any feedback? Thanks!

Do systems further away from equilibrium increase entropy faster than a system with a high level of entropy and does this increase push the universe towards thermal equilibrium faster. Is there anything stopping the universe from reaching thermal equilibrium?

I've just watched the lecture of Penrose on his cyclic universe theory here: I fact I understood that he claims that any kind of matter dissapears in a couple of Googol years due to Hawking radition; so there is no matter left at the end, which leads to a reduced degree of freedom in terms of...

Hubble observed that not only is the universe expanding but that it is accelerating. With the model of the Big Bang as I understand it, the universe began as a big explosion. That would mean that it expanded at a rate exceeding the speed of light or at least close to it. If that is correct, that...

Homework Statement (a) Show the relation between frequency received and emitted (b) Find the proper area of sphere (c) Find ratio of fluxes Homework EquationsThe Attempt at a Solution Part (a) Metric is ##ds^2 = -c^2dt^2 + a(t)^2 \left( \frac{dr^2}{1-kr^2}+ r^2(d\theta^2 + \sin^2\theta)...

By fitting redshift distance data we can estimate the present Hubble rate H0 and the longterm limit that the Hubble rate is tending towards H∞. The Age (how long the universe has been expanding) can be calculated just from those two measurements, assuming the spatial-flat standard cosmic...

What is the minimum speed in the universe ?

I want to know Universe density according to this equation( ##k=-1##) ? ##H^2(t)-8πρG/3=-k/a^2(t)## ##ρ_U=ρ_m+p_r## ##ρ_U##=Universe density ##ρ_m##=Matter density ##p_r##=Radiation density

Homework Statement The evaporation enthalpy of Hg is ##59.3 kJmol^-1## at its boiling temperature ##356.6ºC##. Calculate: (a) the vaporization entropy of Hg at this temperature (b) the change in entropy of the surroundings and universe (c) the vaporization entropy of Hg at 400ºC.I was also...

I still don't understand this fully. Can someone please explain? I saw a video where an analogy was made, the distant observer is like an accelerating observer in flat spacetime and guy falling in is like an inertial observer, is it just like the coordinates of the distant observer from the...

Hi people. I just read some articles about physicist starting to gain more and more evidence for the Universe to be a 3D Hologram of a 2D world (or that's how I understood it). And apparently for us living in a "Matrix", like the one in the movie. Now I would like to understand the relation...

Dear PF Forum, Sorry to ask this question again after so many threads here and in google that explain nothing! And many controversies, too. 1. Does the universe really comes from nothing? Yes or No? ------------------------------------------------------------------- 2. if "YES" then... What...

Dear PF Forum, Again the same question about preferred frame of reference. I have read several threads in Physics forum, but I think this question belong to cosmology. And I have searched in Google and in PF forum threads, so, I'll ask some confirmation here. 1. Does the universe have a...

Viewpoint 1: Because gravity or other forces that are holding the thing concerned (be it a galaxy, a ruler or an atom) together are way stronger than the "force" caused by the expansion of space. So strictly speaking, space does in fact expand everywhere, including the space inside an atom...

I found this article interesting it does away with dark energy and dark matter. two of the things i hate in cosmology. On the nature of cosmological time Pierre Magain, Clémentine Hauret Comments: 5 pages, 4 figures, submitted to MNRAS Subjects: Cosmology and Nongalactic Astrophysics...

Alan Guth mentioned in his lectures that to get the accurate linear relationship of Hubble's law, we need to subtract the velocity of the Earth with respect to the cosmic microwave background (CMB) when calculating the velocity of galaxies. Question 1: If space is expanding uniformly...

We know that universe is expanding .I am curious about how universe radius change with time or simply R(t)=? (Observable universe radius)

Hi i have a question, i m a engineer but i have probably a dumb question ¿if the Expansion of the Universe is accelerating, but exist a speed limit "c" this tell me that at one point the universe will expand at a constant rate?

Hello everyone, As you can see, I am new on this forum. In my first thread, I decided to ask one very interesting question, maybe one of the most shocking questions which exist at this moment. We all know the data which have been provided of WMAP and Planck satellites, and what this data shows...

What If we accept starting point of the big bang as the central point and what If the equatorial expansion rate of a spinning universe was the speed of light, how would it impact universe? ( In this question, you may think yourself as an observer from out of universe. I try to mean with "the...

What If the universe has a spin, was it causing the similar results like dark energy?

When temperature of the universe falls below nucleon mass ##T<<1## GeV, the number densities of nucleons (proton and neutron) which are in kinetic equilibrium can be obtained as ##n_i=g_i (\frac{m_i T}{2\pi})^{3/2} e^{\frac{\mu_i-m_i}{T}}##. Since baryon number should be conserved, then I...

My understanding: When we draw a triangle on a flat piece of paper and measure the angles using a protractor, the sum of the angles is ##180^\circ##. So we conclude that the universe is locally flat. Suppose we draw a very big triangle that spans across galaxies (say, using lasers and mirrors)...

Kolb&Turner in "the early universe" mentioned that for a scalar field ##\phi## at finite temperature, ##p=-V_T(\phi)## and ##\rho=-p+T\frac{d p(T)}{d T}## where ##V_T## is potential energy including temperature correction. My question is: when we consider the evolution of the universe using...

Would someone like to have a conversation with me about the bounds of the universe and energy? I have a few ideas rambling around.. When I say bounds I mean the expanding bubble. But I would like to discuss infinite matter and infinite energy big crunch possibility. I'm a beginner with BIG thoughts.

Dear PF forum, I once read that the universe IS nothing. And "FROM", too. But I like to ask about "IS". They say that "Gravity" is negative energy. So if you add all the masses and energies and gravity, it would be zero. What I'd like to ask is this. A. Is all Mass + Energy + Gravity = 0? B. Is...

Dear PF Forum, After searching many links in Google and threads in PF, I can't find the farthest object in the universe. I have some questions here, perhaps someone can give me quick and simple answer. A. What is the farthest object in the universe? How far away? B. The radius of the...

If you take the size of the observable universe can you find out how many cubic plank lengths can fit in the observable universe and it doesn't have to be exact just approximation.Also the math and formulas would be helpful too.

Whenever I attempt to research this question, my search results yield "Is the Universe Infinite" where the question ALWAYS refers to the volume of the universe. This question is usually answered along the lines of: "If the universe is closed, than it's volume, aka it's 3D surface area in...

There is a series of very interesting science fiction films lately related to physics and from Marvel Universe. To those dizzy already or want to relax from Many Worlds or unsolved problems in physics, etc. Try to watch the latest Avengers: Age of Ultron. I have to watch it the second time to...

I know that universe can be have three different futures.But for lastes theories universe is growing faster then we thought.I want to ask how much energy we need to make this observable universe.

What are the lines of investigation right now? I'd have listened that it could be more than one kind of Higgs particle, which ones? What if them are found? Could an arbitrary universe exist without the Higgs field? or it would exist as a it must exist? (maybe this is very philosofical) What...

I am studying general relativity from Hobson and came across the term 'lifetime' of a closed (k>0) universe, ##t_{lifetime}##. I suppose at late times the curvature dominates and universe starts contracting? Are they simply referring to ##\int_0^{\infty} dt##? If so, would the bottom expression...

Homework Statement (a)Find how ##\rho## varies with ##a##. (b) Show that ##p = \frac{2}{\lambda^2}##. Find ##B## and ##t_0##. (c) Find ##w## and ##q_0##. What values of ##\lambda## makes the particle horizon infinite? Find the event horizon and age of universe. (d) Find luminosity distance...

I have thought about something for a while now, and wondered if we would have a different understanding of the universe, and the smallest known particle, if we humans were smaller or larger. What if we humans was at the size of a pinhead (And maintained the same brain capacity as normal sized...

Homework Statement [/B] (a) Find the value of A and ##\Omega(\eta)## and plot them. (b) Find ##a_{max}##, lifetime of universe and deceleration parameter ##q_0##. Homework Equations Unsolved problems: Finding lifetime of universe. The Attempt at a Solution Part(a)[/B] FRW equation is...

I'm talking to a friend here in whatsapp, he says that he believe in a 'dimensionless universe', look what he said... "let's consider that time is an illusion and since time has such an intimate relationship with space, space is an illusion as well". he said that the concept of universal...

There is some surprising twist regarding measurements of accelerating expansion of Universe. Maybe it is not accelerating that fast as previously predicted. It seems that there is something questionable about Ia supernovae. What do you think about it? Is this real game changer or some minor...

This theory was accepted? Is it more to be correct or more to be wrong?

Nothing can exceed the speed of light so how can scientists can tell us about 1000s of light years away of our location in the universe ? I mean what instruments have they used for it ? Waves? ( what kind of waves ? ).

Starting from the FRW metric (for simplicity flat space, radial direction only): $$ds^2=-c^2dt^2+a(t)^2dr^2$$ If we take dt=0 then the proper distance ds(t) between two spatially separated points at cosmological time t is given by: $$ds(t)=a(t)dr$$ Now at the present time t_0 we can define...

This is a follow up to another thread (https://www.physicsforums.com/threads/something-about-calculating-the-age-of-the-universe.807250/), but I post it as a separate thread since it is not clear to me (a) this is actually correct, and (b) assuming it is, whether it actually provides a...

I think it is correct to say the farthest light we can see is about Z=7' it would be remiss of us to think astronomers will not find light from higher values of Z in the future. My question is how old IS the univeres. http://phys.org/news/2015-02-big-quantum-equation-universe.html...

Good day all,First of all, I want to let you guys know that I'm quite new to the subject so please bear with me in case I'm asking a very basic question here. I have a struggle with the way the Age of the Universe is calculated by using Hubble's Law: V = H x D and I hope you guys could clear...