Hubble constant & Critical density?
1. multiply by (light year)³ with AU expressed in so many metres That is 3.3480 X 10³³. It gives an answer 3013264742 X 10¹¹ kg = 301326474.2 tons 2. {you didn't mention the link up -- that the Earth mass to be distributed at the above density}. Since Volume = mass / density, divide Earth's mass (=5.977 X 10²³ kg) by the density given above. It gives you the volume of the cube.take the cube root of such cube to get one side. ∛Volume = ∛[mass / density] = ∛[5.977 X 10²⁴ / 9 x 10‾²³] = 4.0496 X 10¹⁵metres = 27069.60 AU = 0.1311 pc
Hubble Constant?
Hubble's law is a statement in physical cosmology which states that the redshift in light coming from distant galaxies is proportional to their distance. The law was first formulated by Edwin Hubble and Milton Humason in 1929[1] after nearly a decade of observations. It is considered the first observational basis for the expanding space paradigm and today serves as one of the most often cited pieces of evidence in support of the Big Bang. The most recent calculation of the proportionality constant, using the satellite WMAP began in 2003 and a combination of other astronomical data, yielding a value of 70.1 ± 1.3(km/s)/megaparsec. In August, 2006, a less accurate figure was obtained independently using data from NASA's orbital Chandra X-ray Observatory: 77 (km/s)/Mpc or about 2.5×10−18 s−1 with an uncertainty of ± 15%.
Hubble s constant lab! HELP!!!?
I am doing a lab on Hubbles constant and I just can t get the numbers right on this data table. We must find the distance in megaparsecs, recessional velocity km/s, and Hubbles constant km/s/mpc for the following galaxies: Virgo: 7.80x10^7 Ursa Major: 1.00x10^9 Corona Borealis: 1.40x10^9 Bootes: 2.90x10^9 Hydra: 3.96x10^9 And then the average value for Hubbles constant. It is given that H= 50km/s/mpc
If the Hubble constant were to be found to be much smaller than we think it is right now how would this change
It would mean the galaxies were moving more slowly and would have taken longer to reach their present position. Meaning that more time had gone by since the Big Bang.
The Hubble constant has been measure to have a value of 70 km/s/Mpc. From this, astronomers are able to calcul?
One issue is that the Hubble constant isn't actually constant, because the universe is expanding at an increasing speed due to "dark energy" Since the Hubble constant is always increasing, the lower the lower the speed, the younger the universe and the higher the speed of the constant, the older the universe is. Not sure what what grade you're in, but you would have to plug the constant of 35 into an algorithm for you to determine the age of the universe since it doesn't scale linearly. If you're in a high school class, then I'd suspect that they're just looking for the simple answer of at 35km/s/Mpc the age of the universe would be cut in half.
What is the physical significance of the Hubble constant?
The Hubble parameter is defined as [math]H\left(t\right) = \frac{1}{a\left(t\right)}\frac{\mathrm{d}a\left(t\right)}{\mathrm{d}t}[/math], where [math]a\left(t\right)[/math] is the scale factor of the universe, that is how much it’s bigger/smaller at a certain time relative to its dimension now. The physical meaning is the relative rate of growth of the universe, and it has been decreasing since the beginning. In a matter dominated universe, [math]a\left(t\right) \sim t^{2/3}[/math], so [math]H\left(t\right) = \frac{2}{3t}[/math]. In a dark energy dominated universe, [math]a\left(t\right) \sim \exp{\sqrt{\Lambda/3\,t}}[/math], and [math]H = \sqrt{\Lambda/3}[/math] is truly a constant (in time). Right now our universe is dominated by dark energy, but the matter contribution is still not negligible, so [math]H\left(t\right)[/math] is somewhere in the middle.The Hubble parameter also specifies the physical distance at which objects are receding at the speed of light, called the Hubble distance: [math]R_H = \frac{c}{H}[/math], which is approximately 4.4 Gpc at current time. Not that this distance is smaller than the current radius of the observable universe, which is around 14 Gpc.
Could you interpret Hubble's constant as indicating that expansion is slowing down by 70km/s every 3,270,000 years?
No, the Hubble constant (never Hubble’s constant) is simply the rate of expansion of the Universe at a particular time. Ho (“H naught) is the present value that we see around us in the nearby Universe, which differs from the expansion rate at cosmologically distant times. H has the dimensions of inverse time, and its reciprocal provides an estimate of the age of the Universe (under the assumption of a constant rate), which is ballpark OK. The value encodes no information about the rate of its change, however.
Value of Hubble Constant, tricky/contradictory information?
KennyB is 100% correct. > "I know it can expand faster than light, but once you get to that distance isn't it impossible for photons to reach us because the Universe is expanding too fast?" This is true. The "edge" of the observable universe is the point at which no photons will ever reach us because they are too far and cannot ever reach us, even if they are travelling at the speed of light. This point is known as the Particle Horizon. http://en.wikipedia.org/wiki/Observable_... > "They say that the Hubble constant is 70.4 (km/s)/Mpc." This is pretty much correct. I believe the most authoritative source on the value of the Hubble Constant is the WMAP satellite. They have made it a goal over the past 7 years to nail down an accurate value of the Hubble Constant (amongst other values) and they suggest it is equal to 69.32 +/- 0.80 km/s/Mpc. You will generally find sources quoting values in the range of 68 to 76 km/s/Mpc. Anything outside this range, I think, is outdated and incorrect. > "By doing some algebra and using the speed of light you should see that the edge of the Observable Universe is expanding at the speed of light, right?" Actually no. If you do out the math - and the math is actually kind of complicated - you find that the edge of the observable universe is expanding away at three times the speed of light. > "c /(Hubb_cnst) = Size of Universe c/H = 14,000 megaparsecs Solve for H and you get that it is 21.4 km/s/Mpc BUT on the same page it says H =70Km/s/Mpc" This actually doesn't work, for a variety of reasons. First off, c / H does not give you the size of the universe. Second, the edge of the universe is traveling faster than c, as I mentioned above. Third, H is not constant. I know that may sound wrong, but the term "Hubble's Constant" is somewhat of a misnomer. The constant is actually a function of time. And because looking farther into space is equivalent to looking back in time, effectively Hubble's Constant is a function of distance from us as well. That means you need a function that tells you how Hubble's Constant changes over time and space. It is really only constant for the local region of our universe. You cannot apply it any farther than about the Virgo cluster. If you really want to check up on the math, get a cosmology book and study the Friedmann Equation.
Taking into consideration Hubble's Law, from an Earth perspective, is the expansion of space accelerating equally rapidly in all directions? Wouldn't that mean that we are "at the center of the Universe" which isn't the case?
I'm not sure I understand your assertion about the rubber sheet analogy. If I take a rubber sheet and mark a series of points on it, then fix a camera such that one point is held in the centre of the frame, when I stretch the sheet uniformly in both directions the camera records that all the other dots are receding from our chosen point. Where does the analogy break down?We know where the centre of the observable universe is - at the observer. If the universe is larger than the observable universe we have no information regarding the direction in which the true centre is to be found. If we did we would know for sure that there is more universe than we can see.However I was always taught that when we look into the further reaches of space we see the universe as it was. I never got an answer to the question that if a photon set off from a galaxy far back in time it would come to our eyes when we had moved into our current position. If light travels in straight lines, why then don't we see an increased density of the earliest galaxies in the direction of the centre of the universe? Except that one lecturer remarked that the expansion of space means that light doesn't travel in straight lines. Ouch.