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Expansion vs distance and time

08/15/2022 6:04 AM

When astronomers look at distant galaxies, they are observing them as they were billions of years ago, and the red shift corresponding to their relative speed is a snapshot of billions of years ago. Naturally,the further away, the more Redshift, because that is a snapshot of the past, closer to the beginning of the BB event. The earlier in the universe, the further away, and the more Redshift, and the faster the expansion rate, which would be normal in a regular explosion.

Closer galaxies would show less Redshift because they are more "recent", which would indicate to me that they are moving away slower than distant ones.

So how can they determine that the universe is currently expanding at an accelerating rate? All they can see is the state of the universe billions of years ago.

As usual, I appreciate and welcome all constructive comments with an open mind.

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#1

Re: expansion vs distance and time

08/15/2022 6:31 AM

Everything could just be shrinking I guess....

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#2

Re: expansion vs distance and time

08/15/2022 7:35 AM

Please define <...they...>?

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#3
In reply to #2

Re: expansion vs distance and time

08/15/2022 7:49 AM

In the first instance of "they" in my post,I am referring to astronomers.

In the second instance I am referring to galaxies.

All clear now?

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#4
In reply to #3

Re: expansion vs distance and time

08/15/2022 9:14 AM

I’m feeling left out… where do I fit in?…

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#6
In reply to #4

Re: expansion vs distance and time

08/15/2022 4:57 PM

You can be an independent observer on an undefined plane of existence...

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#7
In reply to #6

Re: expansion vs distance and time

08/15/2022 5:16 PM

Sounds complicated, I’ll try not to let you dow… *poof*

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#5

Re: expansion vs distance and time

08/15/2022 11:03 AM

So how can they determine that the universe is currently expanding at an accelerating rate?All they can see is the state of the universe billions of years ago.

There are independent ways of measuring astronomical distances (parallax, Cepheid variable stars, Type I Supernovae, etc), and these can be correlated with redshift. If the expansion rate of the universe were constant, the redshift would be proportional to distance (Hubble's constant). If the expansion rate is changing over time, there will be a deviation in the straight line plot between distance and redshift.

https://www.physicsforums.com/attachments/i02-15-accelerating-jpg.200356/

https://owlcation.com/stem/The-Standard-Candles-of-Astronomy-or-How-We-Attempt-to-Measure-Distance-in-Space

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#8

Re: Expansion vs distance and time

08/15/2022 11:26 PM

What is the oldest star in the milky way? It has to be less than 100,000 LY from us. What is it's red shift? Does it match other same age, far off stars?

We have never found a method of oscillation yet, which does not change with gravity. From pendulums to crystal oscillators to atomic clocks, they all change with gravity.

I think a rotational ticker for a clock, would solve our clock problem, and allow absolute time to be measured.

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#9
In reply to #8

Re: Expansion vs distance and time

08/15/2022 11:59 PM

"I think a rotational ticker for a clock, would solve our clock problem, and allow absolute time to be measured."

Don't most mechanical clocks and watches use a rotational ticker? In fact, a pendulum is a rotational ticker.

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#11
In reply to #8

Re: Expansion vs distance and time

08/16/2022 5:56 AM

The expansion of the universe refers to galaxies, on average, receding from each other. AFAIK individual galaxies are not expanding, so no reason why stars in the Milky Way would be moving away from Earth.

Also the expansion of the universe is on average. Our nearest galactic neighbour, Andromeda, is moving towards us, and will eventually collide. I don't know the estimated time frame, but long after humans have disappeared, and probably after the Sun has turned into a red giant, about 1 billion years.

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#10

Re: Expansion vs distance and time

08/16/2022 1:34 AM

If you prefer, but I would consider a pendulum an oscillation, as it changes direction plus two full stops plus the 2 accelerations.

A rotational ticker would have one constant direction and a constant angular velocity.

Only one variable is changing...the direction, and it's a constant change.

Compare that to an oscillation and all the changes that it goes thru. Almost any exterior force can change a back and forth motion.

This allows us to use 3 axis vibrations(oscillations) to measure motion and orientation of your smartphone. And to measure gravity gradients at great sensitivities.

An atomic clock uses a dipole vibration. Lifting and lowering an atomic clock, leads some to believe that they are measuring space-time.

However, a long vertical shaft along the gravity gradient, the rotation will not change with the gradient, like the oscillator does. It measures and detects absolute time. Anywhere.

I don't believe that space is related to time. We have quantified and inventoried everything for 1000s of years with numbers. Thus, it is we who has given everything a math relationship, not nature. The first thing we learn in math, is that the numbers themselves are related. Now, they have even given the emptiness of space mathematical properties.

These modern academic narratives and pronouncements mystify me.

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#12

Re: Expansion vs distance and time

08/16/2022 3:21 PM

"Closer galaxies would show less Redshift because they are more "recent", which would indicate to me that they are moving away slower than distant ones."

No, closer does not mean more recent, but less redshift means moving away slower. But they are not moving IN space, they are moving WITH space as space is expanding. However the closest ones are moving towards us from gravitational "forces" IN space.

The Physics Forums has multiple threads on things like this, so is a better place to find out about cosmology and several other topics.

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#13
In reply to #12

Re: Expansion vs distance and time

08/16/2022 6:19 PM

I will not argue with you.

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#14
In reply to #12

Re: Expansion vs distance and time

08/20/2022 7:16 AM

Something wrong with age of the universe calculations,and if so. that would affect everything we think we know about it.

Methuselah older than the universe?

https://www.youtube.com/watch?v=jiSwvxA5v4Q

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