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## Hubble constant question

Hello been reading up on Hubble Constant.
So it looks as though 3 different group have 3 different values of expansion speed. My questions are as follows.

Are the 3 different speeds being measured at the same time by each group or are the numbers varied because the time frame which they calculated this is different?

Is the speed different because the expansion has actually sped up that fast from the time the lowest number was calculated to the time the highest was calculated.

Did each group calculate in the same timeframe and came out with different numbers but also used different was ya of measurement

Does the different speeds being seen change the age of the universe we currently think, of yes how much of an age difference?.

Thank you
Last edited by Sinbad; 2020-Jan-11 at 01:17 PM.

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Hello been reading up on Hubble Constant.
So it looks as though 3 different group have 3 different values of expansion speed. My questions are as follows.

Are the 3 different speeds being measured at the same time by each group or are the numbers varied because the time frame which they calculated this is different?

Is the speed different because the expansion has actually sped up that fast from the time the lowest number was calculated to the time the highest was calculated.

Did each group calculate in the same timeframe and came out with different numbers but also used different was ya of measurement.

Thank you
Good question.

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Hello been reading up on Hubble Constant.
So it looks as though 3 different group have 3 different values of expansion speed. My questions are as follows.

Are the 3 different speeds being measured at the same time by each group or are the numbers varied because the time frame which they calculated this is different?
They are being measured over a range of distances (and hence times) and then corrected back to H0, which is known as the Hubble parameter and equal to the Hubble constant now.

Is the speed different because the expansion has actually sped up that fast from the time the lowest number was calculated to the time the highest was calculated.
It would be if they were not doing the correction mentioned above.

Did each group calculate in the same timeframe and came out with different numbers but also used different was ya of measurement
This is more of the issue. Each group uses a different method to derive the Hubble parameter and there is a small but significant difference in the answers they get. For example to do the correction I mention above you have to have a relationship between the measured Hubble constant and the the Hubble parameter. This involves having a model for how it changes over time. In some cases the Hubble parameter is not what is being measured but inferred from very different measurements and then related back to the Hubble parameter through a model of the universe which contains a lot of complexity and could have inaccuracies in it. That said these models are the best we can currently do.

Does the different speeds being seen change the age of the universe we currently think, of yes how much of an age difference?.
It does result in a difference, but the age of the universe is also sensitive to how the expansion of the universe is changing. You can use cosmology calculators like this one to try out what happens to the age of the universe when H0 changes, and also see what else it is strongly dependent on. For one of the high values (73.5) it gives an universe of 12.89 billion years. For one of the low ones (67.8) it gives 14.1 billion years. Current consensus estimate is around 13.8 billion years.

And it's worse than just three groups - https://en.wikipedia.org/wiki/Hubble...ubble_constant
You can see from the table the sheer variety of ways that are used to estimate this number. Hopefully the differences will show up which methods are not giving consistent results and in doing so expose some assumptions that we made that are wrong.

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Thank you Shaula, I kind of understood your response, need to look into some though since my knowledge is lacking so some lingo goes over over my head.

So which is right and which is wrong. And since the times vary to a factor that’s how they know the age of the universe. Is that the only way they know.
Last edited by Sinbad; 2020-Jan-11 at 04:17 PM.

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So which is right and which is wrong. And since the times vary to a factor that’s how they know the age of the universe. Is that the only way they know.
The joy of science - we don't know which is right and which is wrong. In fact the odds are that at some point in the future all of these methods will seem flawed or wrong. Science progresses by making ever more stringent tests for itself, trying to prove itself wrong. In this case we have a model that gives slightly different results for what should be the same number when we feed in different sets of measurements. There isn't an independent way to know the age of the universe so we don't know which one is actually the best result. All we can do is come up with other tests of the model, work out where it is going wrong and then replace or tweak those parts of it.

Cosmology is a lot like trying to work out what a building is for from a vantage point on a hill a long way away. You can't see inside it, you have to watch what goes on around it and build hypotheses about what that means is happening inside it. Then you compare these hypotheses to other observations and gradually eliminate the ones that are proven wrong and alter your theories until you have something that matches what you are seeing.

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Am I correct in stating that, it’s not the expansion rate fluctuationing faster or slower,it’s the different ways it’s calculated that are giving different results.

And through science and history of observation we can tell the age is between 12 and 15 billion years old then.
Last edited by Sinbad; 2020-Jan-11 at 08:00 PM.

7. Brand new paper on the faster-than-expected expansion of the universe. Not noticeable in our lifetimes, of course.

https://arxiv.org/abs/2001.03624

The Expansion of the Universe is Faster than Expected
(Submitted on 10 Jan 2020)

The present rate of the expansion of our Universe, the Hubble constant, can be predicted from the cosmological model using measurements of the early Universe, or more directly measured from the late Universe. But as these measurements improved, a surprising disagreement between the two appeared. In 2019, a number of independent measurements of the late Universe using different methods and data provided consistent results making the discrepancy with the early Universe predictions increasingly hard to ignore. We review key advances realized by 2019:
-- The local or late Universe measurement of the Hubble constant improved from 10% uncertainty twenty years ago to under 2% by the end of 2019.
-- In 2019, multiple independent teams presented measurements with different methods and different calibrations to produce consistent results.
-- These late Universe estimations disagree at 4σ to 6σ with predictions made from the Cosmic Microwave Background in conjunction with the standard cosmological model, a disagreement that is hard to explain or ignore.

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What does this mean?

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Still not sure has the expansion drastically sped up or is it the fact they are using different measurements and equations give for the different values?

Also I take it that it is by all these different equation results which lets them know that the universe is between 12 and 14 billion years old and the average calculation amongst all results give it 13.8
Last edited by Sinbad; 2020-Jan-16 at 03:14 PM.

Still not sure has the expansion drastically sped up or is it the fact they are using different measurements and equations give for the different values?

Also I take it that it is by all these different equation results which lets them know that the universe is between 12 and 14 billion years old and the average calculation amongst all results give it 13.8
It will be a few years before we know more solidly what the discrepancy is caused by. Odds are that there are some different issues with the distance ladder for the different kinds of measurements, but it is also possible that the accelerated expansion has been speeding up slightly over the last seven billion years. Until we measure things more carefully with some additional methods, we can only make models and see which ones fit best. That is why this is currently a hot topic... it is being actively researched.

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Do these descrepencies Still keep the age of universe around 13.8 or does it extend the age to older than we think
What I mean is it seems the differences range higher and lower which each measured equation so regardless or the difference it still always puts age of universe between 12 and 15 billion years of age right
Last edited by Sinbad; 2020-Jan-16 at 05:34 PM.

Do these descrepencies Still keep the age of universe around 13.8 or does it extend the age to older than we think
What I mean is it seems the differences range higher and lower which each measured equation so regardless or the difference it still always puts age of universe between 12 and 15 billion years of age right
Because of the uncertainties in the various measurements it feels wrong to give 3 significant digits for the bounds, but the 13.8 billion number comes from the precision cosmology efforts (Planck and WMAP) which examine the CMBR, but doesn't take into account possible more recent changes in 'Dark Energy' which may or may not explain the discrepancies. For the time being, you can either use 13.8 billion years, or express it with implied range, and no one will be critical of your choice. In no case do we know the age anywhere near close enough to use Google Calendar to see what day of the week the big bang happened on.

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I guess what I meant was we are looking at approximate 13.8 and not a possibility of some thing like 23 billion year old. I was not asking for exact day lol

I guess what I meant was we are looking at approximate 13.8 and not a possibility of some thing like 23 billion year old. I was not asking for exact day lol
23 billion is very unlikely. I haven't seen anything outside the window of 12.8 to 14.4 billion recently, and 13.8 is still a good number to quote.

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Thank you

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When you said slightly speeding up over the past 7 billion years that is not something we just learned correct that is something we have known about and still brings the general average to 13.8 billion years. Am I correct in this?

I also assume that when the value of big rip, Big Crunch or big freeze which have been predicted billions of year from now also take the expansion speeding up into there time frame of billions of years from now.

17. Some models for dark energy have the accelerated expansion increasing mainly after the first 7 billion years, and that depending on how different that behavior is, it can mean that local observations about the rate of expansion (formerly The Hubble Constant) will be higher numbers and make the universe look a little younger than it really is.

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Yes but from my understanding it is a different of millions of years and not billions still keeping it under 15 billion years old. Not a drastic change of billions of years. I guess what I am trying to say is all these factors which you have stated is what makes us know the age is around 13.8 and not like 22 billion years old.

Your comment of making it look younger than it really is confuses me. Are you stating that the universe is like 20 billion years old and we see it as 13.8 or are you stating that it is around 13.8 give or take a few billion years?

I also assume that when the value of big rip, Big Crunch or big freeze which have been predicted billions of year from now also take the expansion speeding up into there time frame of billions of years from now.
Last edited by Sinbad; 2020-Jan-16 at 11:40 PM.

... Your comment of making it look younger than it really is confuses me. Are you stating that the universe is like 20 billion years old and we see it as 13.8 or are you stating that it is around 13.8 give or take a few billion years? ...
If the actual age is 13.8 (as measured looking at the CMBR), but expansion has accelerated in the second half of the universe, when we look at the expansion of the local galaxy clusters viewing only the last half billion years, the universe might look like it is 12.8 billion years old.

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Ok I get it I think so basically the u inverse is only between 12.8 to 13.8 billion years old.

Now the caliculations for the end of the universe stated billions of years from now take the current age of the universe as there factor for producing these conclusions.

According to this we are at the end of our universe

http://vixra.org/pdf/1912.0358v3.pdf
Last edited by Sinbad; 2020-Jan-16 at 11:57 PM.

... According to this we are at the end of our universe

http://vixra.org/pdf/1912.0358v3.pdf
It might be good to not take these guys very seriously. The paper is doing a lot of hand-waving, and the authors don't seem to have any credentials or institutions backing them.

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But am I correct according to them the universe will end in our lifetime? Or am I misunderstanding what I am reading

I also assume that when the value of big rip, Big Crunch or big freeze which have been predicted billions of year from now also take the expansion speeding up into there time frame of billions of years from now.
It wouldn't, because we don't know enough about the ultimate fate of the universe to be able to tell now which scenario will happen and when. The best guess we have (I could be wrong) is that it could be a big freeze (i.e. that the universe is flat), and in that case the time frame is not governed by the Hubble expansion but rather by how stars burn and stuff like that.

But am I correct according to them the universe will end in our lifetime? Or am I misunderstanding what I am reading
I think you are misreading them even if they are correct. I think they are saying the universe ends after 22 billion years, and we are 13 billion into it, so unless our lifetime is very long it doesn't seem likely.

But am I correct according to them the universe will end in our lifetime? Or am I misunderstanding what I am reading
They are just making stuff up. It depends on some "edge of the universe" that everything is heading towards, but we have no evidence that there is anything like this, let alone what the size of it would be if there were. Really, IF there is anything to what they are writing, then nothing else we have discussed has any meaning. What is the age of the universe? using their model it can't be measured using our methods. Further, using their model, there is no explanation for the CMBR, or the Baryonic Acoustic Oscillations. By their model, we are accelerating from one point. What direction is that? The universe should look different in that direction, but there is no such direction. I can't say you are misunderstanding what you are reading. You are reading nonsense that doesn't relate to our actual universe and our observations of it. Feeling like you are misunderstanding it, that probably means you understand that it has holes in it.

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Can you please explain how you understand that. I mean I have no clue and we all know that but from what I tried to understand with the millions of years away and universe is 13.8 billion years old we are past due,

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So basically what I understood was right, they are stating it would end in our lifetime?

They are just making stuff up. It depends on some "edge of the universe" that everything is heading towards, but we have no evidence that there is anything like this, let alone what the size of it would be if there were. Really, IF there is anything to what they are writing, then nothing else we have discussed has any meaning. What is the age of the universe? using their model it can't be measured using our methods. Further, using their model, there is no explanation for the CMBR, or the Baryonic Acoustic Oscillations. By their model, we are accelerating from one point. What direction is that? The universe should look different in that direction, but there is no such direction. I can't say you are misunderstanding what you are reading. You are reading nonsense that doesn't relate to our actual universe and our observations of it. Feeling like you are misunderstanding it, that probably means you understand that it has holes in it.

Can you please explain how you understand that. I mean I have no clue and we all know that but from what I tried to understand with the millions of years away and universe is 13.8 billion years old we are past due,
In the discussion they say:

In spinning sphere theory, cosmic doom is 21.98 billion light years.
Where do you get the figure of millions of years?

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It wouldn't, because we don't know enough about the ultimate fate of the universe to be able to tell now which scenario will happen and when. The best guess we have (I could be wrong) is that it could be a big freeze (i.e. that the universe is flat), and in that case the time frame is not governed by the Hubble expansion but rather by how stars burn and stuff like that.
I understand but what I mean is from our current understanding and calculations it is atleast 2.8 billion years away unless I am missing something somewhere?