# Grav-wave eggheads come closer to nailing down Hubble's Constant – the universe's speedy rate of expansion

Scientists think they've made a major leap towards nailing the expansion rate of the universe, known as Hubble's Constant, thanks to gravitational wave data. The astroboffins, based at Princeton in the US, estimate the constant to be anywhere from 65.3 to 75.6 kilometers per second per megaparsec, according to a paper …

1. #### All of this assumes...

...That the universe is actually expanding. If the size of universe was constant and everything in it was getting smaller how would we know?

1. #### Re: All of this assumes...

The inverse square law means that things like gravity do not scale with linear dimensions, so we would have to assume extremely complicated contraction laws applying to different forces. This fails the Ockham's Law test - expansion is much simpler.

1. #### Re: All of this assumes...

What if there is no contraction? What would cause stuff to get smaller? What if adding more spacetime to a universe of a constant size causes all of the preexisting spacetime to get smaller?

1. #### Re: All of this assumes...

If everything were getting smaller then the gap between things (e.g. the atoms in your body) would also be getting smaller. This change in distance would change the strength of the forces between the atoms in your body as those forces depend on distance. So for you to not notice a difference (e.g. exploding like a nuclear bomb, or collapsing into a singularity) it would be necessary for the laws behind those forces to also be 'shrinking' at exactly the same rate.

So, as Benson's Cycle said, the simpler explanation is that the Universe is expanding.

2. #### Re: All of this assumes...

"This fails the Ockham's Law test - expansion is much simpler."

Sorry for cutting in like this, but did you mean Occam's Razor?

2. #### Re: All of this assumes...

Or the whole thing is a simulation, none of this is real...

(It's Wednesday, I feel parsecs from the weekend)

1. #### Re: All of this assumes...

https://www.xkcd.com/2173/

1. #### Re: All of this assumes...

This one's more relevant: https://xkcd.com/1365/

2. #### Re: All of this assumes...

For those arriving from the future:

https://www.xkcd.com/2173/ is the comic from the day the article was published.

As in, chuckfarley posted a permalink to *todays* comic, which might cause some confusion when it's no longer today.

2. #### Your Wish .... Ours to Command* An Alien Force of Novel Source ‽

Or the whole thing is a simulation, none of this is real... ..... Nevermind

Nevermind, just think of the possibilities and pitfalls when IT is in AIMasterful Control. ....... https://www.zerohedge.com/news/2019-07-08/matrix-reality-goes-mainstream-nbc-asks-are-we-living-simulated-universe ...... with Future Views for Presentation/Sublime Audio Visual Depictions for Remote Light Brainwashing/Heavy Virtual Indoctrination.

* That always begs the question ...... Who/What be US? And who/what be their Puppet Masters?

Simple questions easily able to easily enable the crashing of global markets and ponzi schemes alike.

1. #### Re: Your Wish .... Ours to Command* An Alien Force of Novel Source ‽

Yeah... it was kind of funny 5 years ago.

1. #### Re: Your Wish .... Ours to Command* An Alien Force of Novel Source ‽

Yeah ... it was kind of funny 5 years ago. .... Aristotles slow and dimwitted horse

Yeah ..... however, since then, funny to tragic in 5 short years is an abysmal record to be responsible for, Aristotles slow and dimwitted horse.

And to expect to escape accountability for such austere promotions and lack lustre presentations adds farce to the force of arguments displayed which easily results in abject derision and hubris for dessert leaving all diners in dire straits need of a great stomach pumping and colonic irrigation.

The BBC have been rendered a national disgrace rather than flagship entity with their pandering to bickering factions worldwide on second and third party stages which need media attention to survive and fester/prosper, and that is the rickety vessel you be flying in/disease-ridden vassal servering you. ...... Zero Prime 0Day Leadership in Drivering the Future in a Contiguous Series of Novel Engaging Events will always deliver Pitiful Consequences and Unleash Madness and Mayhem into the Insanity of Arenas in Conflict with CHAOS which would choose to ply Death and Destruction rather than Host Constructive Creative IT. And that is the sin and the monumental crime they be hereby charged with.

J'accuse. FFS FUD SNAFU is not a normal lifestyle choice, it is a perverse abomination and corrupt amalgam of an horrendous few. Change the Master Program.

IT aint Rocket Science .... Perfecting Greater Common Sense with Advanced IntelAIgent Input/Output? IT is designedly kept relatively simple so that practically all can learn and understand.

1. #### Re: Your Wish .... Ours to Command* An Alien Force of Novel Source ‽

"FFS FUD SNAFU is not a normal lifestyle choice, it is a perverse abomination and corrupt amalgam of an horrendous few. Change the Master Program."

That is the best summary of Brexit I've ever read. Have an upvote, and a pint on me.

3. #### Re: All of this assumes...

That the universe is expanding isnt an assumption, its a measurable fact. Thats what the whole thing is about, determining that measurement!

1. #### Re: All of this assumes...

It is being measured from the inside not from the outside and Einstein teaches us that the perspective of the observer has an effect on measurements.

1. #### Re: All of this assumes...

Which is factored into the experimental assumptions and tested. One condition should be that whichever direction we look in the expansion rate should be the same. This has been that case, thus far.

For eg if the earth is moving towards a source you are measuring for redshift the motion of earth has to be factored in as does the motion of the solar system. These days I expect the software does that automagically.

I'm a mere 'Stamp Collector' be we at least get taught experimental design and analysis even if the degrees of freedom we routinely work with give some Physicists the collywobbles. We have inbred mouse lines and maternal vs fraternal twins. What's the issue? Oh yes, we can measure dna imprinting now.

2. #### Re: All of this assumes...

Einstein doesn't teach us anything. He developed the General Theory of Relativity which describes the way accelerations and relative velocities affect observations in an extremely precise way.

It's obvious that you don't know how the framework of the observer versus the observed affects measurements. It isn't just a vague thing like "US sanctions on China affect the Chinese economy." There are rules.

I think too you are confusing relativity with quantum effects in which the fact of something being observed affects the observation - which was actually a no shit Sherlock the moment it was realised that anything you can probe an experiment with has momentum itself, but again quantum mechanics gave an explanation and precise numbers.

4. #### Re: All of this assumes...

...That the universe is actually expanding. If the size of universe was constant and everything in it was getting smaller how would we know?

I'll let Father Ted answer this one.

Small.....Far away. Small....Far away......

5. #### Re: All of this assumes...

But where do all the turtles fit in?

1. #### Re: All of this assumes...

I thought they went on bottom:

https://xkcd.com/1416/

6. #### Re: All of this assumes...

"If the size of universe was constant and everything in it was getting smaller how would we know?"

Well, for starters the Doppler shift observed by LIGO would be either zero (for a constant universe), or negative/blue (for a contracting universe). Instead they observed a 'red shift' (ie the wavelength of the waves had increased).

This expansion also agrees roughly with the measurements of the Cosmic Microwave Background radiation, and the measurements of distant supernovas. TFA is about how the estimations of the amount of expansion differ, but they're all within the same order of magnitude, so to a physicist, they're basically all the same.

1. #### Re: All of this assumes...

"Don't waste your time, Duke; the cameras are all right. What is exactly ninety degrees from

everything else?"

1. #### Re: All of this assumes...

Once upon a time, there was a Martian ...

7. #### Re: All of this assumes...

Spoken like a true contrarian, but I'll treat this as an amusing thought.

8. #### Re: All of this assumes...

I'd know if we were all shrinking - I'd have to get a whole new wardrobe.

2. #### "this approach relies neither on the cosmological model nor the cosmic-distance ladder"

And, unfortunately, it appears to agree with neither.

Space. It's big, it's complicated and we still have much to learn.

1. #### Re: "this approach relies neither on the cosmological model nor the cosmic-distance ladder"

It may not agree 100% with either, but the previous estimates were 65 and 75. This one got 70, bang in the middle. So i'd say its pretty damn close.

2. #### Re: "this approach relies neither on the cosmological model nor the cosmic-distance ladder"

"unfortunately, it appears to agree with neither"

Not to mention that

(a) the expansion rate could itself be changing - it's been a while since I dipped my toe in these murky waters, but I though it was still a matter of debate whether the rate of expansion was constant, accelerating, or slowing down.

(b) who's to say that the rate of expansion is constant everywhere in the universe? Again, this is far from being a topic in which I have any expertise, but is there any measurement or theoretical argument against there being different expansion rates in different parts of the universe? That would at least in part explain different measurements

1. #### Re: "this approach relies neither on the cosmological model nor the cosmic-distance ladder"

it's been a while since I dipped my toe in these murky waters, but I though it was still a matter of debate whether the rate of expansion was constant, accelerating, or slowing down.

It's accelerating.

When we look at standard candle supernovas in all directions, we observe that the far away (and thus older) ones are moving away from us more slowly than we would expect if the expansion of the universe was constant. Conversely, the closer (newer) ones are moving away from us faster than expected if expansion was constant. So we know that the expansion is accelerating, and that the acceleration is uniform in all directions.

This is the reason we see boffins wandering around scratching their heads and muttering bitterly about dark energy...

1. #### Re: "this approach relies neither on the cosmological model nor the cosmic-distance ladder"

"It's accelerating."

Not necesscelery, what it clearly means is that the standard luminosity supernovae nearer the fringe of our little universe are encountering increased repulsion/drag from the 'cosmic' soup of antimatter that exists beyond the bubble of space-time we inhabit which limits both the rate and extent of the expansion..

2. #### Re: "this approach relies neither on the cosmological model nor the cosmic-distance ladder"

"When we look at standard candle supernovas in all directions, we observe that the far away (and thus older) ones are moving away from us more slowly than we would expect if the expansion of the universe was constant. Conversely, the closer (newer) ones are moving away from us faster than expected if expansion was constant."

Hmmm... To do what you're saying we need to independently measure speed and distance of a star, and as I recall the whole Hubble thing, faster (more redshift) = further away, so we can use the redshift (ie velocity away from us) as a proxy for distance away. And the parallax + brightness 'ladder' method to measure distances surely to independently measure the distance to any star surely gets more inaccurate the further away you get.

It must be a pretty big difference between observed vs 'modelled for constant acceleration' to be able to say quite definitely that the expansion is accelerating. I am constantly in awe of how much we can learn across such vast distances with what are in effect quite puny instruments

3. #### Re: "this approach relies neither on the cosmological model nor the cosmic-distance ladder"

I think you mean...

Fortunately, it appears to agree with neither.

That will be more useful.

3. I don't understand those numbers. Please put them in El-Reg measurements. Thank you

1. That'd be 3198.3 Brontosauruses per second per 3.28 quadrillion double decker buses. i think.

1. "3.28 quadrillion double decker buses"

Hmmm... maybe we need an approved measure of length that's a few orders of magnitude greater than double-decker buses, or even brontosauruses or Devon fatbergs.

https://www.theregister.co.uk/Design/page/reg-standards-converter.html

Given the common popular usage I would suggest the "equator" (1 equator = 4,347,000 double-decker buses), or the "moonie" (ie distance to the moon - 1 moonie = 18,285,796 Brontosauruses)

1. #### The "moonie" as a unit of measure

The distance between us and the Moon varies by about 50,000km (±6.5%), so not an ideal candidate.

1. #### Re: The "moonie" as a unit of measure

Back in the day when the standard foot was the average length of foot of 12 men randomly selected after church*, I suspect the variation around the country was of that order, and the economy didn't fall apart.

*I suspect this is a rural myth, which is like an urban myth but with more cider.

2. Can't really use the equator as an El Reg measure as it's already in use. The metre is based on the distance between the pole and the equator, originally 10,000,000m (10,000km) so the equator must be roughly 40,000km.

4. #### El Reg delivering the Future directly into Myriad Spheres of Spontaneous Autonomous Influence?

The astroboffins, based at Princeton in the US, estimate the constant to be anywhere from 65.3 to 75.6 kilometers per second per megaparsec, according to a paper published in Nature Astronomy this week. That means the universe was observed to expand at a rate of up to 75.6 kilometers per second over an observed megaparsec, which itself spans 3.2 million light years.

Crikey, Katyanna Quach, that is surely more worthy of the Utterly pontless gobbledygook" moniker earlier misapplied by Christopher Rogers to something else quite altogether very different and much more relevant and relative to present possible virtualised shenanigans of fundamental cosmic consequence where SNAFU Rulers Rule?

Howso?

1. #### Re: El Reg delivering the Future directly into Myriad Spheres of Spontaneous Autonomous Influence?

Howso? .... STOP_FORTH

Speaking truth unto and through powers that wannabe is how so, STOP_FORTH.

Everything is no more difficult than that easy enterprise ...... but which humans appear to not yet have realised.

Quite whether that is a permanent retardation and systemic learning difficulty or merely an unfortunate temporary glitch is something for discussion and argument around any right royal round table of venerable peers and valiant knights of the realms, methinks, if there be no serious other business to be dealt with.

5. #### gravitational waves ripple through space at the speed of light

Or we assume so.

Probably true. But what are they? A distortion of the "fabric" of the universe. Forget rubber sheet analogies. Or the Æther, because the speed of light measurements suggest (before Einstein, after Maxwell. Michelson and Morley) suggest there is no fabric?

1. #### Re: gravitational waves ripple through space at the speed of light

In the event that was mentioned, involving the collision of two neutron stars, the three gravitational wave detectors triangulated its position and triggered the radio telescopes. So the gravitational and electromagnetic waves travelled the same distance in the same time.

The bit that I find implausible in all of this is the estimation of intergalactic distances - way beyond what can be done with parallax.

1. #### Re: gravitational waves ripple through space at the speed of light

The bit that I find implausible in all of this is the estimation of intergalactic distances - way beyond what can be done with parallax.

You look for Type 1a supernovas in distant galaxies. These occur in white dwarf binary systems, and only occur once a white dwarf has accreted a known amount of mass. Because the mass is known when the star goes nova, we also know the amount of energy released and how much light produced, and so they all have the same brightness.

Once you measure the apparent brightness of such a supernova in the sky, the inverse square law can be used to determine its distance away from us.

2. #### Re: "... estimation of intergalactic distances ..."

Apply the Hubble constant to the observed red-shift and that gives you distance. That's why it would be nice to have an accurate value so it would be easy to calculate distances without having to wait for a Type 1a to go off near to the observed object.

2. #### Space without mass thought experiment

Do the "what if there was no mass" thought experiment and its pretty clear.

-----

First of all, the speed of light is measured experimentally using experiments that themselves are based on how fast forces propagate. If forces propagate using the same mechanism as light travels, then you'd expect experiments to keep the speed of light constant, EVEN IF IT WAS NOT CONSTANT. i.e. if it takes 40 oscillations for light to travel a certain distance, then you measure 40 oscillation regardless of how far light has actually travelled, because your experiment is really measuring the speed of light based on those oscillations.

You cannot rely on the speed of light being a constant just because you measure it as such.

----

What if there was no matter in space, would space have a scale?

1. If matter was bound twice as loosely, it would be twice as big.

2. So the scale of matter depends at minimum on the matter itself, and possibly also on the scale of space.

3. You would have TWO competing things determining the scale of matter. How stretched space is, and how stretched the matter in that space is.

4. So if you took all the matter out of space, what scale would space have?

5. Infinite? Zero? Some arbitrary number? You could not determine it because there is no matter to measure.

6. So you really only need matter to scale space. Matter gives space its scale.

----

Does gravity bend space?

7. No, if space was all even, then forces would be all even.

8. Think of a bunch of magnets all spread to make an even field.

9. You disturb the field, and they all snap together organizing themselves to be attraction only.

10. It's the distortion in the field, that created the uneveness that permitted the magnets to organize themselves to attract.

11. Same with gravity.

In peasoup (the resonance electric oscillation model of matter), if the resonant wavelength is shorter to the left than to the right, then the nearest resonant point is likely more often less than right and the matter moves to the left more than the right.... i.e. gravity is a result of the distortion of space.

-----

Does matter bend space?

12. No. Look at the 'mass' used by the particle physicists. electron volts per C squared, essentially it is how much electric field there is in a volume.

13. It's simply a number indicating how concentrated the space is.... it's a measure of how concentrated matter is.

In peasoup, to estimate mass, I take the volume of post corrected space (corrected to make the speed of light the same in all directions) and count how many electric oscillations pass through that volume over 1 F oscillation. Very very similar.

------

So what does bend space?

14. If mass doesn't bend space and gravity doesn't bend space, what does bend space?

15. Well go look at point 6 again, its matter that gives space its scale.... if you organize matter to be tighter bound, then space is also tighter bound.

It's just how matter is organized that gives it scale. In peasoup, particles are loops of N resonant wavelengths of resonant oscillation. Those loops twist back on themselves to make tighter bindings. An F11 (11 wavelengths) is double twisted like a rubber band, whereas F2 (2 resonant wavelengths typically binding electrons) is a much simpler oscillation.

Stuff like light and forces propagate over that oscillating field. Light is near the 1W per oscillation resonance point. W is the local wavelength of oscillation, the tighter the binding of matter, the shorter W is, the tighter space is.

----

Motion is a phase shift over this W field.

In one dimension imagine an oscillation up and down, on a field going down-up. It cancels out the field and does not move as long as it stays in resonance.

Now suppose I pushed 1% of that oscillation into another axis. Now it will also flip over every 360 oscillations in that axis too.

So each oscillation it is 1% out of phase with the underlying field. It no longer cancels the field unless it moves.

So it's position moves to the nearest resonance point across this field, each oscillation.

Yeh sure I'm simplifying it so you can visualize it easier, but its really a complex oscillating wiggle in 3 dimensional space. All matter, all light is doing this.

If W is smaller then that 1% is also smaller and the motion is smaller.

i.e. the scale of space is also smaller if W is smaller.

-----

Light is electric oscillation motion, forces propagate the same way, i.e. they distort the field, as the oscillation happens, they move, which further distorts the field for the next particle, which moves as it oscillations which distorts the field.... and so on, propagating the field at the rate of the oscillations.

Since every experiment you perform is ultimately based on the rate of forces propagating or light propagating, so its equivalent to 'space' being distorted.

----

So no, the underlying fabric of space is not distorted, It never had scale to begin with, its scale comes from our perception of the resonant wavelength, which itself is based on how we measure and perceive the world.

1. Nurse!

6. #### Starts With A Bang!

I can't recommend Ethan Siegel too much......

He's great for covering most cosmic subjects.

7. #### It's all inside the error bars

The upper and lower limits of this gravitational wave-based observation bracket both the Cepheid-based result of 73.48 and the CMB-based result of 67.3.

So I'm unsure what the story is here.....

1. #### Re: It's all inside the error bars

That they've figured out a third independent way of measuring it, and they only need (roughly) 15 more examples to tighten down the error bars.

Either it will end up agreeing with one of the existing measurements, which will suggest that the third measurement might just be wrong.

Or it will miss both altogether, in which case who knows?!?

8. #### Durrr...

Sorry for being the token thicko, but can I have these quantitive figures in trusty El Reg units please?

1. #### Re: Durrr...

I did see that. But I'm not convinced the post is using previously agreed units. The post seems more suggestive than prescriptive.

9. #### potentially stupid question

A statement higher up in the thread gave me an idea - probably a stupid idea long ago considered and rejected by those far smarter than me. However, since a casual search reveals no evidence of such consideration and subsequent rejection, I must ask:

Stated above: 'If everything were getting smaller then the gap between things (e.g. the atoms in your body) would also be getting smaller." So why can't we measure the expansion rate more locally with, for instance, some mundane object of normal matter? Does the local gravity well slow the expansion rate OR is the difference simply too infinitesimal to measure with current instruments?

1. #### Re: potentially stupid question -- no, not really at all

Seems quite sensible.

However, as you hypothesized, gravitationally bound systems defeat the expansion. This means forces stronger than gravity -- the strong nuclear force, electromagnetic force -- stomp all over the cosmic expansion. No chance for our bodily molecules or atoms to take part.

I'd have to look it up to be sure, but I believe that clusters of galaxies, and even superclusters, are bound together by gravity such that the individual galaxies inside the cluster are not receding from each other.

10. don't know why molecular forces are being brought into the discussion given that they aren't impacted by gravity, which is so many many orders of magnitude weaker - and until we know exactly why the universe is expanding vs contracting or steady state (and that is still up for discussion since it is all predicated on what model of Inflation of space/time eventually proves to be correct) we won't be able to judge the constant delta of the Hubble Constant.

Dark Energy vs. Dark Matter - quantum effects vs mass effects; meanwhile we are all stuck in the middle with "u"

11. #### There's a third possibility

The rate of expansion hasn't been constant throughout the history of the universe. Some theories of the Big Bang pretty much require a period of really fast inflation in the first few moments, but even ignoring that there's no reason to assume that the rate of expansion today is identical to the rate of expansion 6 billion years ago. Especially if our universe is part of a bigger metaverse, and energy from the 'outside' influences our expansion.

If the rate of expansion isn't constant, then it makes sense that the constant calculated via the cosmic background radiation (which basically measures the rate of expansion at what 750,000 years of age of something like that?) and the rate calculated using Type Ia "standard candle" supernovas at varying distances and the rate calculated by measuring gravity wave events like neutron star or black hole mergers.

So I'm not sure they should reject the calculation of one method as "wrong" merely because it doesn't agree with the answer achieved using another method.

12. #### Maybe a dense question..

.. but what makes it so sure it's a constant?

13. #### Red-shifted gravity

My understanding of red-shifted waves is that the wavelength increases but also that the wave itself loses strength. Could that apply to gravitational waves and therefore to gravity losing strength, not strictly due to distance but due to the two objects moving apart at speed? If so, has anybody done used these calculations with relevance to the existence or not of dark energy?

1. #### Re: Red-shifted gravity

Mmmm. That's a question for physic maths.

I'm uncertain whether the properties of electromagnetic waves and the properties of gravity waves are identical in that regard.

Thinking intuitively, with no real physics to back me up: gravitational waves induce a stretch-squeeze as they pass through spacetime, and through matter. Similar (but not identical in detail) to the tidal stretch-squeeze of the Moon.

For waves of frequency X, pretend that the stretch-squeeze happens 10 times per minute; after the frequency is expanded by a factor of 2, the stretch-squeeze would happen 5 times per minute. So if you had something which extracted energy from the waves -- a piezoelectric crystal the size of Scotland, for example -- then the waves would transfer less energy per minute from the redshifted gravitational wave. Or so it would seem.

But imagining an event like the merging of two black holes, then the entire wavetrain generated by the event would have the same total energy after redshifting as before -- the wavetrain would just be twice as long, and would take twice the time to deliver the energy to your giant piezoelectric device.

I hope someone with knowledge of the theory and maths involved pipes up. I just hung my hat on a bunch of intuitive BS...

Incidentally, it's worth noting (again) that physics is mathematical. When one says that "the speed of light is measured experimentally using experiments that themselves are based on how fast forces propagate ... You cannot rely on the speed of light being a constant just because you measure it as such." that's kind of true... but in fact the speed of light can also be derived from Maxwell's wave equation. And like all well-established mathematical descriptions of the Universe, Maxwell's descriptions of electromagnetism, in math, has stood innumerable experimental tests coming at it from many, many angles. And of course his laws are retested every day inside your computer. The Electric Universe guys can toss out the bathwater, conceptually, but they don't realize the number of babies they toss out with it.

1. #### Re: Red-shifted gravity

Actually, the speed of light is a defined quantity. You want to measure how long, in seconds, a light pulse travels one meter. But the meter is defined as the length of the path traveled by light in a vacuum during a time interval of 1/299792458 of a second.

14. #### What if the universe expands at different rates over time?

What if the universe is indeed inside a black hole? As matter falls into that parent black hole the amount of matter inside it increases. As matter inside increases then it causes expansion of our universe. If this is the case then the rate of expansion will vary depending how much matter is falling into it. Clues that this is happening would be a very rapid rate of expansion at the start of our universe and then a difficulty over time to precisely measure the rate of expansion.

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