Hubble Definition and 271 Threads

Hi there! I'm having some trouble understanding Hubble's Law and Constant and would be grateful for some help. So Hubble's Law shows that the most distant galaxies have the greatest red-shift, as they are moving away from us fastest. This shows that all galaxies are moving away from each other...

Dear PF Forum, I know this is a very basic, basic question. But I'd like to refresh my memory. In Hubble Law. ##V = H_0 \, D## ##H_0## is Hubble constant, aproximately ##\frac{1}{3.1E17t}## Okayy, let's say we alter those number to an easier number. For every 10 metres, the velocity adds 1 m/s...

I am interested in whether it is necessary to account for the effects of the Hubble Redshift in determining the rotation velocities of galaxies exhibiting keplerian motion and, in particular, whether the associated spatial expansion of the Universe is known to result in spectral shifts that...

Is there agreement here regarding the relationship between expansion of the universe from its initial conditions, entropy (2nd law), time, (and more tenuously perhaps) "evolution"? I asked a question awhile back that was too specific I think that tried to tie the constant of expansion to the...

I recently came across this claim: "On the other hand, in certain cases even an expanding cosmology may have 0 average expansion, due to the fact that we are averaging over an infinite amount of time. " Is this correct? can someone explain how averaging over infinity time leads to zero ...

Do I understand correctly (in general terms) or wildly incorrectly if I imagine that the constant of expansion and the second law of thermodynamics are very closely connected, or even that the constant of expansion is potentially the source of the second law?

Story at: http://spaceref.com/astronomy/hubble-sees-a-smiling-gravitational-lens.html

Hi there, This is my first post but I've been a spectator for a long time now. So I've been working on some of the basics of cosmic expansion and there is one contradiction that I came upon that I can't seem to resolve. I've looked around some of the similar threads but I couldn't find anything...

I'm interested in understanding what effect does long-term radiation and microdust exposure would do to the surface roughness of a high-precision mirror like the one on the Hubble. Since it has been on orbit for 24 years, it provides an unique opportunity to estimate accumulated environmental...

Is there any observational data available for evolution of Hubble rate? To give some context, read the dark energy FAQ by Sean Caroll here. He says: "If the universe is decelerating, the Hubble constant is decreasing. If the Hubble constant is increasing, the universe is accelerating. But...

if the speed of the expansion is decreasing then it would mean that the radius of the Hubble sphere is increasing because it would require more space to expand faster than the speed of light .but as you said if the speed of expansion is increasing then why is the Hubble sphere increasing and why...

why does the Hubble sphere increase amd why is the Hubble constant called a constant if the value keeps changing.

How one can say that the space is expanding by just verifying that the galaxies are speeding away from each other?

I'm looking at general relativity and particularly considering what happens at the Big Bang. I think the Friedman equation is H^2=\frac{8\pi G}{3}\rho so I see that as the matter density goes to infinity, H goes to infinity. According to this video (around 10:10), this is where the problem lies...

Is rather a question of calculus skills, but how do I get the time derivative of the Hubble parameter here in [1]? Is it the Leibnitz rule, the chain rule, some clever re-arrangement? thank you

by Dr. Ken Croswell, author of The Alchemy of the Heavens The Milky Way may have found a solution to its gas shortage. Astronomers had calculated that our home galaxy possesses only enough fuel to forge new stars for just a few billion more years. But scientists have now discovered that a...

T (Gy) R (Gly) 0.00037338 0.00062840 0.00249614 0.00395626 0.01530893 0.02347787 0.09015807 0.13632116 0.52234170 0.78510382 2.97769059 4.37361531 13.78720586 14.39993199 32.88494318 17.18490043 47.72506282 17.29112724 62.59805320...

There has been a flood of new data. Cosmologists have not yet settled on a new agreed value of H0. This may help lead to one. http://arxiv.org/abs/1406.1718 The 1% Concordance Hubble Constant C. L. Bennett (1), D. Larson (1), J. L. Weiland (1), G. Hinshaw (2) ((1) Johns Hopkins University, (2)...

Hubble’s law tells us that the velocity of distant objects increases with distance as v = Hr. Does this mean that the farther a distant object gets the more rapidly that object will recede away from us? That is, are these distant objects accelerating away from us? Can we say v = Hr, and so...

Jorrie's calculator (Lightcone) makes cosmic history tables which tell you among other things the Hubble times in past years. For convenience let's temporarily use greek Theta Θ to stand for THubble so we don't have to write so much. Basic facts (definitions actually) are that Θ = 1/H and the...

Hey guys, I feel like an idiot for asking this. However, I wanted to make sure that my head was screwed on straight before I asked my old astronomy professor permission to use some of his old lecture notes. Is gravitational redshift one of the causes of Hubble's Law? Is the Redshift of the...

Hello All, In Carroll's there is a brief introduction to a dynamical dark energy in which the equation of motion for slowly rolling scalar field is discussed. Then to give an idea about the mass scale of this field it is compared to the Hubble constant, saying that it has an energy of...

I did a cursory search on the forum, and I browsed Wiki...but maybe I missed it. What is that big Flap/Door on the end of the scope.? Is it part of the optics, or is it a protection device, or a...? Thank You

Homework Statement For a problem I'm doing, I am considering a universe in which k=0, and I'm told that I can consider most of the expansion to have happened during a phase when only one of the density parameters was dominant (I know which one, as well), but I don't know the scale factor or...

Hubble Sees Infant Galaxies at the Edge of the Universe http://www.slate.com/blogs/bad_astronomy/2014/01/09/distant_galaxies_hubble_image_of_galaxies_at_the_universe_s_edge.html

Hello! This is my first post, so go easy on me! I'm working through Scott Dodelson's book Modern Cosmology http://books.google.com/books?id=3oPRxdXJexcC&pg=PA23&source=gbs_toc_r&cad=4#v=onepage&q&f=false and I am a bit confused about equation 2.85: $$\rho_{DE} \propto e^{-3 \int^a...

Homework Statement For a κ=0 universe with no cosmological constant, show that H(z)=H0(1+z)3/2 Homework Equations Friedmann equation: H2=\frac{8*\pi*g}{3c^2}-\frac{κc^2}{r^2}*\frac{1}{a(t)^2} The Attempt at a Solution I know that R(z)=R0/(1+z) but I do not know where this comes...

Hello, everyone it seems to me that people understand how to do this problem but I am struggling to solve it. Homework Statement A quasar with redshift 0.3 is gravitationally lensed into two images by an elliptical galaxy at redshift 0.18. There are two images of the quasar which are separated...

How deep can Hubble Telescope see?? -I understand that the Hubble telescope can only resolve galaxies at about 13 billion years old, using gravitational lensing. I am curious, is this because the telescope does not have the power to see farther? Or is this because there are no farther...

http://www.cnn.com/2013/07/11/world/space-blue-planet/index.html?hpt=hp_t1

The cosmological "Big Rip" and a shrinking Hubble radius Doesn't an expanding universe forecast such outcomes as a faded and unobservable cmb, galaxies moving away from each other greater than the speed of light, a gravitationally unbound solar system, and eventually an observable universe...

My school textbook says that discovery of the 1a supernova was what led to the understanding that the universe expansion is accelerating but doesn't hubble's equation already suggest that the universe would expand at an accelerating rate? V = Hd (V = velocity, H = hubble's constant, d =...

When Hubble published that the galaxies were moving away from each other, the further away the greater redshift and the greater separation velocity, was he saying that space itself was expanding, on the basis of Einstein's general theory, or was he assuming a more or less fixed space, with...

How to derive "dark energy" density from Jorrie's Hubble radius limit (c^4/(8 pi G))*3*(17.3e9 light years)^(-2) Paste that in the google window, and see what you get. When I paste that into google I get 0.5393 nanopascal, which is equivalent to 0.5393 nanojoule per cubic meter. If the...

78 Pictures from the Hubble Space Telescope http://www.space.com/15235-hubble-space-telescope-latest-photos.html

Hi guys, I am in a state of slight confusion! I need to know if I am getting this information right, or I have gotten something wrong somewhere! It is to do with the Hubble constant and the Hubble law. So 1920 Edwin Hubble estimated that the Universe was 14 Billion years Old but new...

Recently, astronomers from Caltech and Edinburgh University discovered galaxies with a redshift of 11.9. With the Hubble constant at 67.8 km/s/Mpc ( according to the most recent survey with the Planck Satellite ) this means that the galaxies are at a distance of 14.24 billion light years ! With...

1. Homework Statement If \phi is a usual field is it possible that H\dot{\phi}=-\partial^2\phi/{\partial x^2} Where H is the Hubble constant and the dot denotes time derivative 2. Homework Equations H\dot{\phi}=-\partial^2\phi/{\partial x^2} 3. The Attempt at a Solution I tried different...

According to the wikipedia entry, the latest values for the Lambda-CDM model parameters for the age of the Universe, t_0, and the Hubble constant, H_0 are t_0 = 13.75 \pm 0.11 \times 10^9 \mbox{ years} H_0 = 70.4 \pm 1.3 \mbox{ km s}^{-1} \mbox{Mpc}^{-1} If you combine the errors this implies...

Hubble’s law, according to Wikipedia, says that the recession velocity of a distant object P comoving with Earth is vrec=HD where H is Hubble’s constant and D is the proper distance from Earth to P. The Hubble sphere is the area of space in which all objects comoving with Earth have vrec less...

[SIZE="3"][FONT="Times New Roman"]I'm doing a summer internship and my supervisor is currently away and uncontactable. He left me details of certain Hubble images to download and analyse asking for HST images of M31 with coordinates 00:42:52.534 +41:18:54.17 on 2006-07-15 and 2007-01-12...

Hi. If we fire a rocket into space at some significant fraction of the speed of light (say 0.1c) and then switch off the engines and let it cruise indefinitely, will it appear to accelerate away from us and in effect be carried along by the Hubble flow. Given a million or a billion years would...

What must the Hubble constant be if the Universe is flat. At the Lamda CDM article on wiki it says 70.4 km/s mpc. I'm not sure if that's what it must be if the universe is flat or if that's what experiments have measured it to be, I'm 99% sure that it's the former but I want to be 100% sure...

Hubble Law - recession velcoity? v = H0d tells us that the recession velcotiy of a galaxy is directly related to its distance from us on earth However, as the planets move further apart, their potential energy increases (and hence kinetic energy decreases). How do these two phenomena tie...

I understand that a Hubble diagram is a graph of recession velocity plotted against distance for distant galaxies, and shows a linear relationship. The Hubble constant is the gradient of the graph. We are now observing extremely distant galaxies with greater than expected velocities due to...

Hi all, this is my first post; apologies if it seems a bit basic, I suspect there's something fundamental I'm not getting here :smile: Say I observe the spectrum of a galaxy, and I calculate its redshift. I then use the Hubble Relation to find its distance, which is, say, ten billion light...

I am looking at inflation at the moment, and it says in my textbook that (aH)^(-1) is constantly increasing in matter or radiation dominated epochs. a is always positive and always increasing. This tells me that da/dt is positive. I think that setting the universe to MD/RD means that da/dt...

Some years ago I read that the Hubble Telescope is obsolete because modern telescopes have adaptive and corrective optics that make a space telescope unnecessary(at least for visible light). Since new Earth based telescopes have the advantage of very large mirrors(10 meters for the Keck) vs 2.4...

We normally assume that the recession of distant galaxies is due to the expansion of the space between the galaxies and us. In a co-moving frame the expansion of space is factored out so that all objects remain at a fixed distance away from us in cosmological time. Thus the co-moving frame is...

Homework Statement I should derive the Hubble law redshift from Maxwell equations in closed Universe. Homework Equations The metric of closed Universe is ds^2 = dt^2 - a^2(t)\left(d\chi^2 + \sin^2 \chi d\theta^2 + \sin^2 \chi \sin^2 \theta d\phi^2\right). The Hubble law redshift: \frac...