# Shouldn't the Universe be slowing down in expansion?

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As you look at galaxies further and further away, they appear to be moving faster and faster away from us, doesn't it also mean that galaxies that we see more in a past are moving away faster then the ones we see closest to the present time. Why cant we then conclude the obvious from it, that the Universe is slowing down in expansion.

I have learn't about Universe actually increasing its speed of expansion. But isn't the true answer obvious from a fact I have just mentioned, and that they must have made an error in measurement.

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Hello Mohika and welcome to forum. On your question - the experimentation and calculations to show an accelerated expansion are pretty rock solid, the fluid part is the explanation. To get a better understanding I would heartily recommend listening to the three physicists who got the gong for this discovery.

The Nobel Prize in Physics 2011

Beneath each Laureates name (click the little arrow) you can listen and watch the Nobel lecture. These are for a lay audience and, these three in particular, give a brilliant grounding in the discovery. I am pretty certain your question is covered - it was the anomalous readings that did not concur with the predictions based on the ideas you have mentioned that made them realise something was incorrect in our model

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As you look at galaxies further and further away, they appear to be moving faster and faster away from us, doesn't it also mean that galaxies that we see more in a past are moving away faster then the ones we see closest to the present time. Why cant we then conclude the obvious from it, that the Universe is slowing down in expansion.

I have learn't about Universe actually increasing its speed of expansion. But isn't the true answer obvious from a fact I have just mentioned, and that they must have made an error in measurement.

No error in measurement, no way!

But sometimes I also wonder what is the difference between what scientists have in mind and what they explain.

For example in the following graph stolen from Schmidt Lecture page 23:

I would have drawn the red line exactly the other way. That is: elongated in the past and compacting to the left.

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As you look at galaxies further and further away, they appear to be moving faster and faster away from us, doesn't it also mean that galaxies that we see more in a past are moving away faster then the ones we see closest to the present time. Why cant we then conclude the obvious from it, that the Universe is slowing down in expansion.

I have learn't about Universe actually increasing its speed of expansion. But isn't the true answer obvious from a fact I have just mentioned, and that they must have made an error in measurement.

This Figure is good for understanding universe expansion.

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That figure is meaningless.

Ever since you learned how to use paint, we've had one meaningless figure after another.

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That figure is meaningless.

Ever since you learned how to use paint, we've had one meaningless figure after another.

We can see this scenery in the night sky.

To see accelerated expansion or decelerated expansion, we transfer this data to the figure that I posted before at #4.

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As you look at galaxies further and further away, they appear to be moving faster and faster away from us, doesn't it also mean that galaxies that we see more in a past are moving away faster then the ones we see closest to the present time. Why cant we then conclude the obvious from it, that the Universe is slowing down in expansion.

I have learn't about Universe actually increasing its speed of expansion. But isn't the true answer obvious from a fact I have just mentioned, and that they must have made an error in measurement.

Does "Accelerating expansion" make sense? If it was true, we wouldn't even see any galaxies. They'd long ago have speeded away into the diistance, and vanished from our sight.

The fact that they haven't vanished seems to refute the "acceleration" theory.

The whole business is probably due to some error of measurement, as you say.

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Does "Accelerating expansion" make sense? If it was true, we wouldn't even see any galaxies. They'd long ago have speeded away into the diistance, and vanished from our sight.

do you have any math to show this? Or is it just a feeling you have?

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Does "Accelerating expansion" make sense? If it was true, we wouldn't even see any galaxies. They'd long ago have speeded away into the diistance, and vanished from our sight.

How long ago exactly? How long does it take for a galaxy in 'accelerating expansion' to vanish from our sight?

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As you look at galaxies further and further away, they appear to be moving faster and faster away from us, doesn't it also mean that galaxies that we see more in a past are moving away faster than the ones we see closest to the present time. Why cant we then conclude the obvious from it, that the Universe is slowing down in expansion.

I think the reason it may boil down to is that physics foots on consistent mathematical models, not the syntactical consequences of two randomly-picked sentences about traits of this model. Even if they were grammatically correct.
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Our observing method through the telescope.

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No error in measurement, no way!

But sometimes I also wonder what is the difference between what scientists have in mind and what they explain.

For example in the following graph stolen from Schmidt Lecture page 23:

I would have drawn the red line exactly the other way. That is: elongated in the past and compacting to the left.

Like this:

Or is this completely wrong?

Edited by michel123456
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This Figure is good for understanding universe expansion.

This is a constant accelerated expansion case.

Red line is an observers line.

The origin is Big Bang point.

Redshift = receding speed effect + universe expansion effect.

This chart is not a red shift chart, but a receding speed.

Edited by alpha2cen
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This is a constant rate expansion case.

Method of calculation of light arriving time.

arriving time = light leaving time + (distance)/C

= 13.75billion years

8a Super cluster case

t8a+distance 8a/C=13.75billion years

16a Super cluster case

t16a + distance 16a/C=13.75billion years(2012)

Observer line calculation

$t_{current}=t+L/C$

$t_{current}=t+(L_{initial }+vt)/C$

$v=(Ct_{current}-L_{initial})\frac{1}{t} -C$

$v=A\frac{1}{t}-B$

$t_{current};$ current time, 13.75billion year

$L_{initial};$ initial Supercluster distance from the Earth

Edited by alpha2cen
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More precise picture of #13, constant acceleration case.

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How about redshift gradient of supernova1a s in the very far away Superclusters ?

Redshift gradient is very big or small, which one?

Redshift gradient = |(redshift2 - redshift1 )/(light intensity2-0.5 - light intensity1-0.5)|

Redshift gradient far away superclusters (>>>, >, =~, <, <<,?) Redshift gradient near super clusters

Edited by alpha2cen
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As you look at galaxies further and further away, they appear to be moving faster and faster away from us, doesn't it also mean that galaxies that we see more in a past are moving away faster then the ones we see closest to the present time. Why cant we then conclude the obvious from it, that the Universe is slowing down in expansion.

The conclusion is that the expansion velocity is proportional to distance (more far more faster). Of course, when more far is the object of us more time needs the light to reach us, and this is why we speak about seeing them "in the past".

To check if the universe is slowing down in expansion or not, we must measure the expansion at different times (e.g. today, two years ago, five years ago...) and see what happens. The rate of expansion is not slowing down but increasing

http://news.nationalgeographic.com/news/2011/10/111004-nobel-prize-physics-universe-expansion-what-is-dark-energy-science/

http://map.gsfc.nasa.gov/universe/uni_expansion.html

Edited by juanrga
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This is a constant expansion case. The expansion started from one point.

From this graph, we can not find any difference between no acceleration and constant acceleration.

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How long ago exactly? How long does it take for a galaxy in 'accelerating expansion' to vanish from our sight?

Well, that depends on how much time the galaxies have had to accelerate away. If they've had 13.7 billion years to accelerate, they should by now be travelling so fast that they'd have exceeded light-speed - and thus completely vanished from our sight.

Yet we can still see galaxies. For example - a few nights ago I observed the Andromeda M.31 galaxy through my Zeiss 7X50's. The galaxy was definitely still visible.

How do you explain that?

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Well, that depends on how much time the galaxies have had to accelerate away. If they've had 13.7 billion years to accelerate, they should by now be travelling so fast that they'd have exceeded light-speed - and thus completely vanished from our sight.

Yet we can still see galaxies. For example - a few nights ago I observed the Andromeda M.31 galaxy through my Zeiss 7X50's. The galaxy was definitely still visible.

How do you explain that?

As far as M31 is concerned, that galaxy is still visible because it is in our local group and is therefore not subject to expansion from our perspective.

Generally speaking, the first place I'd look for an explanation is in your calculations. You are indicating that 13.7 billion years is enough time. This would seem to indicate that you have some idea of their acceleration rate, distance, etc. Perhaps if you supplied the method you used to determine that they should be out of sight by now we could determine if that is the source of the explanation.

It might be possible that you did not include in your calculation early inflation, expansion rate, acceleration rate, how long acceleration has been occurring, distances to other galaxies, light that is in transit toward us (and still arriving) that was generated prior to the galaxy's recession rate exceeding c, etc.

Edited by zapatos
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Well, that depends on how much time the galaxies have had to accelerate away. If they've had 13.7 billion years to accelerate, they should by now be travelling so fast that they'd have exceeded light-speed - and thus completely vanished from our sight.

The speed of the Superclusters, which is 10billion years away from the Earth, exceed the speed of light C.

If we can see the Supercluster outside of 10billion years, one point accelerated expansion might have a problem.

Observer line calculation method

tcurrent =t+L/C

tcurrent=t+(Linitial +(1/2)vt)/C

where (1/2)v is average velocity value from Big Bang to a point.

Solve above equation to the v.

v=(2C tcurrent -2Linitial)(1/t) -2C

one point expansion Linitial=0

v=(2C tcurrent )(1/t) -2C

v; speed of expansion(1x1022km/billion year)

C; speed of light(9.46x1021km/billion year)

t; time(billion year)

tcurrent; current time(13.75 billion year)

Edited by alpha2cen
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http://www.scienceforums.net/topic/68634-dark-matter-and-compton-wavelengths/

But DGP ( http://arxiv.org/abs/astro-ph/0603632 ), already at the extremes, is mathematically consistent. i.e. largest Compton wavelength = 13.7 B ly, in reduced form = 13.7/(Pi * 2) = 2.18 B ly. So the Schwarzschild radius for the Planck mass for this reduced largest wavelength is equal to 4.36 B ly or 95 % of the latest calculated time back to the formation of our solar system.

As a circle with a circumference of 13.7 B ly also has a diameter of 4.36 B ly (i.e. circle of the largest possible non reduced Compton wavelength in euclidian space) you can also wonder why this distance is also the circumference of the mouth of a theoretical black hole that could contain all of the mass in our visible universe (in one wavelength). DGP looks like it is a model of space time plus a rotation that is improperly represented as 5D even though it is, I suspect, mathematically consistent with the non reduced non euclidian waveform and everything else based off it for the same underlying reason.

I suppose it depends if you are in a black hole looking out or are actually outside of the 'wonderland' looking in.

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As you look at galaxies further and further away, they appear to be moving faster and faster away from us, doesn't it also mean that galaxies that we see more in a past are moving away faster then the ones we see closest to the present time. Why cant we then conclude the obvious from it, that the Universe is slowing down in expansion.

I have learn't about Universe actually increasing its speed of expansion. But isn't the true answer obvious from a fact I have just mentioned, and that they must have made an error in measurement.

So that you might better understand how it works let's simplify the model. Let's say the universe is full of galaxies exactly one Parsec (3 1/4 light years) apart. From here to the next galaxy let's say that the space between the next galaxy expands in distance at a rate of .000001 parsecs per year. That is such a small amount of change that we probably couldn't even measure it. But a billion parsecs away from us all the space in between galaxies is expanding at a rate of 1000 parsecs every year away from us. This we could readily measure by the redshift of the galaxies spectrum. It is not that the galaxies at a distance in this scenario are expanding away from each other at a faster rate in the past. Everything keeps expanding as to the whole at the same rate. It is simply that the more distant galaxies would be expanding away from us at a greatly faster rate, than those close by with much less space in between.

The accelerated expansion of the universe was proposed for a completely different reason. This proposal was based upon observations of type 1a supernova, which are a type of exploding star. Based upon observations they can be considered a type of standard candle giving off a similar amount of radiation at similar frequencies for a similar amount of time based upon their similarly consistent stellar explosions. But there were consistent anomalies in these observations. Those type 1a supernova closer to us seemed that their distances were farther away and their light weaker than their redshift calculations indicated. And those farther away were brighter. Either the "Hubble Law" for distance calculations was wrong, maybe there was something wrong with type 1a supernovas as standard candles, or the universe was changing its expansion rate over time. They finally decided on the latter since they could find no other explanation for what they were observing. They decided that the expansion of the universe, after the hypothetical Inflation era, was decelerating up until about 6 billion year ago, whereby accordingly they believe the expansion of the universe started accelerating again.

//

Edited by pantheory
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So that you might better understand how it works let's simplify the model. Let's say the universe is full of galaxies exactly one Parsec (3 1/4 light years) apart. From here to the next galaxy let's say that the space between the next galaxy expands in distance at a rate of .000001 parsecs per year. That is such a small amount of change that we probably couldn't even measure it. But a billion parsecs away from us all the space in between galaxies is expanding at a rate of 1000 parsecs every year away from us. This we could readily measure by the redshift of the galaxies spectrum. It is not that the galaxies at a distance in this scenario are expanding away from each other at a faster rate in the past. Everything keeps expanding as to the whole at the same rate. It is simply that the more distant galaxies would be expanding away from us at a greatly faster rate, than those close by with much less space in between. (...)

(bolded mine)

No. The rate is the same (.000001 parsecs per year).

and WE are expanding from them, not them from us.

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The speed of the Superclusters, which is 10billion years away from the Earth, exceed the speed of light C.

If we can see the Supercluster outside of 10billion years, one point accelerated expansion might have a problem.

Observer line calculation method

tcurrent =t+L/C

tcurrent=t+(Linitial +(1/2)vt)/C

where (1/2)v is average velocity value from Big Bang to a point.

Solve above equation to the v.

v=(2C tcurrent -2Linitial)(1/t) -2C

one point expansion Linitial=0

v=(2C tcurrent )(1/t) -2C

v; speed of expansion(1x1022km/billion year)

C; speed of light(9.46x1021km/billion year)

t; time(billion year)

tcurrent; current time(13.75 billion year)

Strait line calculation method.

We do not know Supercluster's moving speed 1 billion light years away.

So we use the light which begins 1billion years ago and arrives at present.

v=(2C tcurrent )(1/t) -2C

t<--1billion year, v calculation. Obtained value is(t1, v1)

From the obtained (t1, v1) value we calculate gradient a

a1=v1/t1

For calculation we think about the Universe model.

The model is like this.

At the big bang, every Super cluster attached at the one point.

--------000000----------

Some billion years ago

----0---0---0---0---0---0---..

At the present

-----0--------0--------0--------0---..

So near first 1 billion away Super cluster moving speed is

v1=a1t

2billion away Super cluster moving speed

v2=2a1t

4billion away Super cluster moving speed

v4=4a1t

8billion away Super cluster moving speed

v8=8a1t

16 billion away Super cluster moving speed

v16=16a1t

Edited by alpha2cen

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