Speed of Universe's Expansion Measured Better Than Ever

Originally posted by nightbringr

Originally posted by CLPrime
reply to post by nightbringr

 

That's essentially right, except it is the radius of the universe that we view expanding from the apparent center, not half the radius. We view 13.7 billion light-years expanding in every direction.

No. If the radius is 15 billion light years, and we are in the middle looking towards the "edge", we only are viewing half of the 15 billions, thus 7.5 billion.

Originally posted by CLPrime
It's also misleading to say "edge" or "center". Galaxies at what we see as the "edge" see exactly the same sort of stuff that we see, and, to them, we appear to be at the edge while they appear to be at the center. It's all a matter of perspective.

Perhaps you can explain this more? This would only work in the "wrap around universe" theory. Since we are discussion the "expansion" theory, this is i believe incorrect. The would be a distinct "edge". After all, the galaxy closest to the edge would see nothing looking towards the edge, however would view 15 billions light years of universe looking towards the center.

A balloon (or more exotic closed shape) expanding has no edge.. how can you be so sure that just because the universe is expanding it has a definite edge? not necessarily so.

Not directed at you this one but other posters in the thread need to understand that you need to talk about 'The Observable universe traveling outwards from the center of Earth at the speed of light in all directions, we know the speed of light so can estimate distance at 'the observable edge'.. but the universe itself may be much much bigger, so large in fact that civilizations would never even see each other (although they could see the same object in space without ever noticing each other) due to the restrictions of light.

reply to post by Quantum_Squirrel

reply to post by ChaoticOrder

reply to post by nightbringr

reply to post by CLPrime


Thank you.
It was looking like this thread was going to die a quiet death, but you have made it interesting.

To break it down Barney Style.
It seems to me that Space itself is infinite, but the observable universe (all the stuff) is obviously finite (at least according to the big bang theory). And it is the observable universe that is expanding infinitely into infinite space.

Did I get that right?

reply to post by watchitburn


Not quite. It is the entire infinite universe that's expanding. But we can only see a small sphere of it (the "observable universe") because light from further away hasn't reached us yet.

reply to post by CLPrime


If the observable universe was infinite, wouldn't that require the big bang to be occurring infinitely as well?

I may be wrong. But there must have been a fixed point at which there was so much matter before the bang. If not, where would the infinite matter be speculated to come from?

reply to post by watchitburn


There was no matter before the Big Bang... matter formed after (quite a while after).

Put simply:

An initial infinite empty vacuum experienced quantum collapse, releasing a large amount of energy (vacuum energy, having negative pressure, so it constitutes an inflation field).
That vacuum energy/inflation field caused a brief period of rapid inflation, and then experienced a phase shift, becoming standard (positive pressure) energy.
As the universe continued to expand, it cooled and matter formed from that energy.
And the universe is still expanding today. In fact, the expansion appears to be accelerating over the last 7 billion years or so.

reply to post by CLPrime


May I ask why you think the process begun in a way where the "initial infinite empty vacuum experienced quantum collapse". Doesn't really seem like something that could physically happen in my mind. I would be more inclined to believe it begun with a super massive vacuum fluctuation or perhaps a slow build up of fluctuation energy as I described in my theory which I posted a few months ago.

reply to post by ChaoticOrder


You and I discussed this before, but "quantum collapse" and "quantum fluctuation" are similar in that they both involve the spontaneous creation of energy. The difference is, quantum vacuum collapse can account for the inflation field. In fact, the collapse (really, the tunneling) of the quantum vacuum is the inflation field.

reply to post by ChaoticOrder


It seems that the current model actually combines the two (though, there is no longer any tunneling involved).
Chaotic Inflation says that the universe was initially in a true vacuum state and filled with a scalar inflaton field. It then experienced some form of quantum or thermal perturbation (similar to your theory). This perturbation caused the inflaton field to displace, which then caused rapid inflation as the field returned to its true vacuum state. The inflation field then couples to other fields, reheating the universe, from which point it evolves like the standard Big Bang model.

I'm still getting my grip on the actual mechanics of the theory, but that's the basics anyway.

Originally posted by fenceSitter
I was trying to figure out exactly what the km/s/megaParsec speed meant. I guess it is related to Hubble's Law which states that the further an object is away from us, the faster it goes.

So according to this new measurement, anything 3 million light years away is travelling at 74.3 km/s (+/-). That would mean something 10 times farther away is travelling 10 time faster - 743 km/s. If the estimated size of the observable universe is around 93 billion light years, the universe's farthest edge (from the 'center') would be 46.5 billion light years. That would mean the edge is travelling 15,500 x 74.3 km/s = 1,151,650 km/s!

If my math is right - that is hard speed to fathom. Thanks OP - I learned something today

Glad someone could figure it out. To me, it just sounds really REALLY fast, to the point where I have to ask, if this has been going on for 14 billion years it sure seems like every galaxy would've flown out of our sight by now. Wouldn't you think?

Originally posted by fenceSitter
So according to this new measurement, anything 3 million light years away is travelling at 74.3 km/s (+/-). That would mean something 10 times farther away is travelling 10 time faster - 743 km/s.

The second statement might be true though you really need to go further out, the first almost certainly isn't though your calculation would fall on the line of Hubble's law. The problem with your first statement is that distance is within our galactic cluster, where the galaxies are moving toward rather than away from each other. For example Andromeda is 2 million light years away and it's moving toward us rather than away from us.

Is the Hubble constant universally applicable?

a galaxy at 1 million parsecs will not be observed to recede from us (unless possibly it is located in a direction from us opposite the direction to Andromeda), because the diameter of the Local Group of galaxies is about 3 million parsecs, and within the Local Group, galaxies are not observed to recede.

Here's a collection of previous measurements in addition to the latest:

Hubble's law

A recent 2011 estimate of the Hubble constant, which used a new infrared camera on the Hubble Space Telescope (HST) to measure the distance and redshift for a collection of astronomical objects, gives a value of H0 = 73.8 ± 2.4 (km/s)/Mpc.[9][10] An alternate approach using data from galactic clusters gave a value of H0 = 67.0 ± 3.2 (km/s)/Mpc.[11][12]

As of 3rd Oct 2012 the Hubble constant, as measured by NASA's Spitzer Telescope and reported in Science Daily, is 74.3 ± 2.1 (km/s)/Mpc

An observational determination of the Hubble constant obtained in 2010 based on measurements of gravitational lensing by using the HST yielded a value of H0 = 72.6 ± 3.1 (km/s)/Mpc.[13] WMAP seven-year results, also from 2010, gave an estimate of H0 = 71.0 ± 2.5 (km/s)/Mpc based on WMAP data alone, and an estimate of H0 = 70.4 +1.3
−1.4 (km/s)/Mpc based on WMAP data with Gaussian priors based on earlier estimates from other studies.[14] In 2009 also using the Hubble Space Telescope the measure was 74.2 ± 3.6 (km/s)/Mpc.[15] The results agree closely with an earlier measurement, based on observations by the HST of Cepheid variable stars, of H0 = 72 ± 8 km/s/Mpc obtained in 2001.

It's interesting that not all of the uncertainties overlap, but there are no huge disagreements.

reply to post by Arbitrageur


Do you just know all this stuff, or do you have to go dig it up?

Because it seems that every thread I start in this forum or the Space one, you always come by and enlighten us with tons of knowledge and facts.
Either way, please continue. And thank you for your contributions.

Originally posted by watchitburn
reply to post by Arbitrageur

 

Do you just know all this stuff, or do you have to go dig it up?

I just finished re-watching a video course in cosmology, so the fact that I watched it once before, and the 2nd time was just within the last few weeks makes this stuff pretty fresh in my head. The TTC site is down right now, but here's a spam-type link (I have no affiliation with this "download provider" scam, and don't recommend it) so disregard any download links, but you can see a description of the course:

Understanding the Universe

01 From Dawn To Dusk
02 Exploring The Night Sky
03 Recent Discoveries in Our Solar System
04 Other Worlds Galore
05 The Formation and Evolution of Stars
06 Supernovae - Catastrophic Stellar Explosions
07 Gamma Ray Bursts and the Birth of Black Holes
08 Observational Evidence For Black Holes
09 Einstein's Relativity
10 Cosmology And Cosmic Expansion
11 The Birth And Evolution Of Galaxies
12 The Accelerating Expansion of the Universe
13 The Stuff of the Cosmos
14 Energy-May The Force Be With You
15 Theories of Everything and Hidden Dimensions
16 Our Universe One Of Many

It's a good course and he's a good teacher. I've got another course by him on astronomy too, but it's more about watching the sky in your backyard, and what to look for.

Given that stars farther away from us are also farther back in time (their light has traveled a longer distance), wouldn't the observation that these older stars are moving faster imply that the Universe's expansion is actually slowing down with time?