Universe's Expansion Rate Is Different Depending on Where You Look

Space.com ^ | July 13, 2018 | Elizabeth Howell, Space.com Contributor

[GodBlessRonaldReagan]

Alvy at 9: [his head still down] The universe is expanding.

Doctor in Brooklyn: The universe is expanding?

Alvy at 9: Well, the universe is everything, and if it's expanding, someday it will break apart and that would be the end of everything!

Alvy's Mom: What is that your business?

[she turns back to the doctor] Alvy's Mom: He stopped doing his homework!

Alvy at 9: What's the point?

Alvy's Mom: What has the universe got to do with it? You're here in Brooklyn! Brooklyn is not expanding!

[ETL]

I suspect that is a bit misleading. I don't think they are measuring Cepheid variables at 14,000,000,000 light years.

Yes, they use different measuring techniques depending on how remote the target objects are. Cepheid variables are only good to a particular distance.

[ETL]

Redshift refers to the displacement of a set of spectral lines which identify a particular chemical compound.

The chemical "ID" is like a bar code for merchandise at the store, only, that with chemicals, each line represents a particular chemical element with a known frequency and wavelength, such that, if the elements appear at a different frequency/wavelength, they know that the object is either moving away from us or towards us. If the sequence is shifted to a lower frequency/longer wavelength, then the host object is assumed to be moving away. ie, redshifted. Vice-versa for objects with lines shifted to higher frequencies/shorter wavelengths. ie, blueshifted

[DungeonMaster]

Thanks for taking the time to type up that reply. Happily I knew quite a bit of the basics of distance measurement.

They are the main reason we now think the Hubble "Constant" is not really constant, but drops off with distance (or, conversely, increases as you get closer in distance and time). That accelerating expansion is not explained by gravity - in fact, it contradicts the expected effect of gravity. Since the velocity (and hence energy) of observed objects seems to be increasing, they call the mechanism we can't otherwise detect "dark energy."

This makes me scratch my head. If the Hubble constant drops off then that implies a slower expansion at the outer edge. Would they expect gravitational slowdown to be equal at all distances? Therefore over a billion years the observed Hubble Constant would reduce evenly. I guess only if they expect even distribution of matter.

I remember my old astronomy books suggesting that galaxies were evenly distributed. How surprised they were to find clusters, filaments, voids and strange motions among them.

[ETL]

“The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A real direct distance measurement of an astronomical object is possible only for those objects that are “close enough” (within about a thousand parsecs) to Earth.

The techniques for determining distances to more distant objects are all based on various measured correlations between methods that work at close distances and methods that work at larger distances. Several methods rely on a standard candle, which is an astronomical object that has a known luminosity.

The ladder analogy arises because no single technique can measure distances at all ranges encountered in astronomy. Instead, one method can be used to measure nearby distances, a second can be used to measure nearby to intermediate distances, and so on. Each rung of the ladder provides information that can be used to determine the distances at the next higher rung. ...”

Contents

1 Direct measurement
1.1 Astronomical unit
1.2 Parallax
2 Standard candles
2.1 Problems
3 Standard siren
4 Standard ruler
5 Galactic distance indicators
5.1 Main sequence fitting
6 Extragalactic distance scale
6.1 Wilson–Bappu effect
6.2 Classical Cepheids
6.3 Supernovae
6.3.1 Measuring a supernova’s photosphere
6.3.2 Type Ia light curves
6.3.3 Novae in distance determinations
6.4 Globular cluster luminosity function
6.5 Planetary nebula luminosity function
6.6 Surface brightness fluctuation method
6.7 D–[omega]; relation
7 Overlap and scaling
8 See also
9 References
10 Bibliography
11 External links

https://en.wikipedia.org/wiki/Cosmic_distance_ladder

[PGalt]

Interesting. Thanks for posting.

"We are very perplexed,"

[FroggyTheGremlim]

Trump’s fault.

[Migraine]

The universe is expanding and accelerating in its expansion as it grows,...

BTW, nothing in the universe can do this (except, maybe, the universe). Just a thought: when an observation leads to a conclusion that contradicts the most fundamental axiom of science, you might need to re-examine that observation (clean your lenses, maybe). Unless, of course, you want to start calling weak foul balls home runs.

[Migraine]

Circular reasoning is very much in vogue nowadays.

[LibWhacker]

Different universes tugging on us differently in different directions, depending on their mass, distance and direction, and nine other things we don’t know about.

[I want the USA back]

How can they measure far-away galaxies? I think the whole theory is full of hot air. They needed to invent dark matter and dark energy to fill in the holes in the theory.

[ETL]

https://www.freerepublic.com/focus/chat/3671561/posts?page=25#25

[ETL]

They needed to invent dark matter and dark energy to fill in the holes in the theory.

Also "Inflation Theory". Big Bang wouldn't work without it.

[SunkenCiv]

Thanks ETL.

---

· String Theory Ping List ·

---

---

· Join · Bookmark · Topics · Google ·
· View or Post in 'blog · post a topic · subscribe ·

---

[SunkenCiv]

LOL!

[onedoug]

Fascinatin’.

Thanks for posting.

[Phlyer]

If the Hubble constant drops off then that implies a slower expansion at the outer edge.

The 'outer edge' is just the edge of the observable universe. There is no 'edge' to the expanding universe that shows a measurable dropoff in density of material. I've seen some estimates, but they all acknowledge they are just estimates. They tend to run that the "true" size of the universe is two or three times what we can observe. The time back to the beginning is known (reasonably well) but all we can see in all directions is out to the observable limits with no indication of an 'edge' in any direction.

So, instead of thinking of it as an 'edge' it's better to think of it as a distance over which light has travelled, and therefore as a time. The expectation was that the universe was originally expanding faster (hence a higher Hubble Parameter), and that it then slowed down due to gravity. If it was slowing fast enough, eventually it would stop expanding and collapse back in on itself. Instead, they found that it was "originally" (again, meaning as far back as we can see) expanding more slowly. So, what has been making it speed up since the Big Bang?

I remember my old astronomy books suggesting that galaxies were evenly distributed.

And so they are, when the question is whether there is any direction we might look where they are significantly more or less dense. They 'web' of the universe does not show any particular direction that is different than any other, except at the level of small 'ripples' in the overall distribution analogous to raindrops in a storm. If you're in the middle of it, it's raining in all directions. That doesn't mean there aren't individual drops (or galaxies, in this analogy) coupled with gusts and eddys.

[SuperLuminal]

Hmmm...I wonder if this could explain the Red Dwarf’s shrinkage and expansion...Probably were crossing an intersection point of the elastic oscillating universe..

[Reily]

Its a function of the type of vindaloo modulated by a the strength of the hops in the lager!

[SuperLuminal]

{:-)