Speed of Universe's Expansion Measured Better Than Ever

The most precise measurement ever made of the speed of the universe's expansion is in, thanks to NASA's Spitzer Space Telescope, and it's a doozy. Space itself is pulling apart at the seams, expanding at a rate of 74.3 plus or minus 2.1 kilometers (46.2 plus or minus 1.3 miles) per second per megaparsec (a megaparsec is roughly 3 million light-years).

This is pretty awesome.
Someone correct me if I'm wrong, but being able to more accurately measure the speed at which the universe is expanding. Should help us get a more precise Age of the Universe, and also help better determine how much force Dark Energy exerts on matter throughout the universe.

“Just over a decade ago, using the words ‘precision’ and ‘cosmology’ in the same sentence was not possible, and the size and age of the universe was not known to better than a factor of two,” said Freedman. “Now we are talking about accuracies of a few percent. It is quite extraordinary.”

This is a pretty big advance, I would guess within the next five years or so we should have it down to less than 1%. I would also expect to hear some new updated ages and forces announced shortly down the road here.

I thought this was cool, and I'm sure some others will also.
Enjoy.

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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

excellent post!
s+f
maybe now we can find out how the universe came into being in the first place

the LHC,spitzer and many other experiments will answer this question piece by piece
until the day we have the full picture and think of our present day ancestors as idiots for not figuring out sooner

good day to all i love this sort of topic... call me a geek

reply to post by fenceSitter


Yeah, I'm terrible at math, so I didn't even try.

But I know that's stupid fast. It didn't occur to me that the edge would be traveling faster than the center. I guess I thought everything would be moving at a uniformly accelerating pace.

I just learned something too.

reply to post by Insearchofthetruth1987


Ha, yeah.
There is no shortage of science geeks on ATS, myself included.

reply to post by fenceSitter


It's not just related to Hubble's Law...it is the numerical value of Hubble's Law.

And the speeds, themselves, don't actually translate into physical (that is, proper) velocities. They only appear to be traveling that fast relative to us. In reality, it's the space between us that's stretching, causing light from distant objects to become redshifted (velocity and the expansion of space both cause the same sort of redshift).

I find it funny that everything seems to be the same distance it was 20 years ago as I look up.
Of course in astronomical terms the expansion is probably not that fast.

I am working on my own theories about this expansion stuff, with different thinking.

reply to post by CLPrime

I figured there are plenty of variables in play - I was just trying to dumb it down for myself!

I think it just goes to show that although we understand a lot more than we did even a decade ago, there are still a lot of things we just can't comprehend yet. One day, when someone eventually figures it out, they will look back and laugh about how stupid we were

Originally posted by CLPrime
reply to post by fenceSitter

 

It's not just related to Hubble's Law...it is the numerical value of Hubble's Law.

And the speeds, themselves, don't actually translate into physical (that is, proper) velocities. They only appear to be traveling that fast relative to us. In reality, it's the space between us that's stretching, causing light from distant objects to become redshifted (velocity and the expansion of space both cause the same sort of redshift).

Beat me to it. The edge of the observable Universe is not actually travelling at some ridiculous speed, the expansion of space makes it seem like that. I like this diagram, really helps visualize what is happening:

Originally posted by fenceSitter
reply to post by CLPrime

 

One day, when someone eventually figures it out, they will look back and laugh about how stupid we were

I don't think so. We just don't have all the information yet.

We don't sit around laughing at how scientists from hundreds of years ago were so stupid. At least I don't.
Most are recognized for figuring out what they did with such limited info.

Originally posted by watchitburn
But I know that's stupid fast. It didn't occur to me that the edge would be traveling faster than the center. I guess I thought everything would be moving at a uniformly accelerating pace.

If i understand it correctly, it DOES expand at a uniform rate.

What isnt uniform however is our perspective. Since ALL space expands uniformly, sitting 1 kilometer from the edge of the universe and looking to the edge, you would only witness 1 kilometer stretching. At the very centre, you would witness 7-8 billion light years of space (half the radius of the observable universe) all stretching simultaneously, therefore it would appear greatly accelerated compared to what was witnessed at the edge, when again it is in fact uniform. What has changed is your perspective.

Originally posted by fenceSitter

One day, when someone eventually figures it out, they will look back and laugh about how stupid we were

We would do better to laugh at how stupid we are now.

Originally posted by ChaoticOrder

Beat me to it.

Of course I did I'll let you get the next one.

Personally I'm putting my bets on the theory that predicts Dark Energy = Vacuum Energy

In physical cosmology and astronomy, dark energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe.[1] Dark energy is the most accepted hypothesis to explain observations since the 1990s that indicate that the universe is expanding at an accelerating rate. In the standard model of cosmology, dark energy currently accounts for 73% of the total mass–energy of the universe.[2]

The simplest explanation for dark energy is that it is simply the "cost of having space": that is, a volume of space has some intrinsic, fundamental energy. This is the cosmological constant, sometimes called Lambda (hence Lambda-CDM model) after the Greek letter Λ, the symbol used to mathematically represent this quantity. Since energy and mass are related by E = mc2, Einstein's theory of general relativity predicts that this energy will have a gravitational effect. It is sometimes called a vacuum energy because it is the energy density of empty vacuum. In fact, most theories of particle physics predict vacuum fluctuations that would give the vacuum this sort of energy.

Dark Energy - Wikipedia

Vacuum energy is an underlying background energy that exists in space throughout the entire Universe. Since there is so much space, this background energy is currently estimated to make up about 73% of the total mass-energy content of the Universe. (Dark matter apparently makes up 23%, with all the atoms we know about coming in at 4%.) Current theory has it that the vacuum energy of "empty" space not only contributes to the mass-energy content, it carries the added quality of negative pressure, which provides a mechanism for the expansion to be accelerating.

Special relativity predicts that energy is equivalent to mass, and therefore, if the vacuum energy is "really there", it should exert a gravitational force. Essentially, a non-zero vacuum energy is expected to contribute to the cosmological constant, which affects the expansion of the universe. In the special case of vacuum energy, general relativity stipulates that the gravitational field is proportional to ρ-3p (where ρ is the mass-energy density, and p is the pressure). Quantum theory of the vacuum further stipulates that the pressure of the zero-state vacuum energy is always negative and equal to ρ. Thus, the total of ρ-3p becomes -2ρ: A negative value. This calculation implies a repulsive gravitational field, giving rise to expansion, if indeed the vacuum ground state has non-zero energy.

Vacuum Energy - Wikipedia

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.

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.

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.

reply to post by nightbringr


I believe what CLPrime meant was "the edge of the observable Universe".

Originally posted by ChaoticOrder
reply to post by nightbringr

 

I believe what CLPrime meant was "the edge of the observable Universe".

Ahhhh, fair enough. Yes, provided we hit the edge of the observable universe and there is still at least another 7.5 billion years of universe beyond that, then yes, it would look exactly the same.

Originally posted by nightbringr

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.

I see your "No" and raise you a Nay-Nay. You're getting the radius and diameter confused. Radius is half the diameter, and it's the radial distance that we see in every direction.

Originally posted by CLPrime

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.

There is only an observational edge due to the fact that light from further out hasn't reached us yet. Though, there is also a slightly nearer "edge" - the Cosmic Microwave Background - which we can't quite see beyond, yet, because the universe at any age/distance beyond that was/is opaque. That was 13.7 billion years ago, though...if we were actually at that "edge" there would be no edge...and the "edge" would appear to be where we are, since the light from here from 13.7 billion years ago is just arriving there.

Since the universe appears to be flat (not spherical or hyperbolic), it would be reasonable to assume that the universe is infinite.

Originally posted by CLPrime
I see your "No" and raise you a Nay-Nay. You're getting the radius and diameter confused. Radius is half the diameter, and it's the radial distance that we see in every direction.

Ahhhh! Of course your right, my bad. As you said, got radius and diameter mixed up.

Originally posted by CLPrime
Since the universe appears to be flat (not spherical or hyperbolic), it would be reasonable to assume that the universe is infinite.

Reasonable perhaps, but if we are discussing the "expanding universe" theory, is there not an edge?

reply to post by nightbringr

Reasonable perhaps, but if we are discussing the "expanding universe" theory, is there not an edge?

Quick answer: infinite space can expand.

Originally posted by nightbringr

Reasonable perhaps, but if we are discussing the "expanding universe" theory, is there not an edge?

Not necessarily. An infinite flat universe is able to expand just the same as a finite universe is. With a finite universe, you have to explain what the "edge" is and what exists "outside." An infinite universe avoids that.

And it's really quite simple to imagine an infinite expanding universe. Picture a number line... 0 in the middle, negative numbers at regular increments to the left, positive numbers at regular increments to the right. Each half goes off to infinity. Now, stretch each side of that number line so that the numbers get further apart. You have just taken an infinite dimension and expanded it.
Do that for all three dimensions and you have an infinite expanding universe.