redshift

Grasper

5:00 PM

if the car pass you, it's already going away from you

Sklivvz

Metric expansion of space

The metric expansion of space is the increase of the distance between two distant parts of the universe with time. It is an intrinsic expansion whereby the scale of space itself changes. This is different from other examples of expansions and explosions in that, as far as observations can ascertain, it is a property of the entirety of the universe rather than a phenomenon that can be contained and observed from the outside. Metric expansion is a key feature of Big Bang cosmology, is modeled mathematically with the FLRW metric, and is a generic property of the Universe we inhabit. However, the model...

This explains it

Grasper

that's why you hear stretched sound

but if the object following you and the space is getting bigger you will still see it as going towards you

redshift tells us that all objects are going away from us

it's not saying that the space between two objects is getting bigger

if the train going towards you but you are faster and getting away, you still hear the compressed sound

you will only hear the stretched sound if the train is going away from you

Using the redshift of their electromagnetic spectra to determine the distance and speed of remote objects in space, he showed that all objects are moving away from us, and that their speed is proportional to their distance, a feature of metric expansion.

any comments on this?

Larry OBrien

@Grasper "if the object following you and the space is getting bigger you will still see it as going towards you" : only if it is following you faster than space is getting bigger. Many nearby objects in the universe, including the Andromeda Galaxy are coming towards us because they are close enough that the redshift does not dominate.

Grasper

5:16 PM

"only if it is following you faster than space is getting bigger." how can it be getting bigger if it's following you faster then you are escaping?

ChrisW

@Grasper en.wikipedia.org/wiki/Relativistic_Doppler_effect says, "The relativistic Doppler effect is the change in frequency (and wavelength) of light, caused by the relative motion of the source and the observer ..."

Larry OBrien

As for your comment "scientists are avoiding confirming this evidence": I used to work at one of the premier observatories in the world and I assure you that the redshift is part of astronomers daily life.

ChrisW

if the distance between them is getting greater then their "relative motion" is that they are moving away from each other

Grasper

@ChrisW, no, one is approaching and one is leaving

you are going towards me but I'm going away from you

Larry OBrien

Why do you say that? Why is "one approaching" and "one leaving"?

Grasper

5:19 PM

if the train is going towards you but you are faster and going away from the train. The train is approaching and you are going away from the train

Larry OBrien

Here is a classic metaphor: draw several stars on an uninflated balloon. They are all close to each other. Blow air into the balloon and they all grow further apart from all the others. Another metaphor is the raisins in an unbaked loaf of bread. As the bread rises, they all move further apart from each other.

If you are faster than the train coming towards you and you and the train are heading in the same direction, the train sound will be stretched, not compressed.

Grasper

I will here it compressed and the train will here my sound stretched.

because I'm running away from the train but I here train going toward me

Larry OBrien

You are incorrect if you are faster than the train coming towards you and you and the train are heading in the same direction.

If you are faster than the train, the sound will be stretched.

ChrisW

@Grasper you shouldn't say that the train is "going towards you" if the train is getting further and further away from you.

Grasper

@ChrisW, no it's coming towards me but in a slower rate then I'm leaving...

so will never get me

Larry OBrien

5:25 PM

If that is the case, the sound you hear will be stretched.

Grasper

if you are on a highway driving, do you hear stretched sound of the cars you are passing or compressed? I hear compressed and they here me as a stretched sound

Larry OBrien

Doppler shifts (what you call "Redshift") are relative to every observer. The cosmic expansion of the universe is a daily observation to professional astronomers.

Grasper

@la

@LarryOBrien, I understand that, that's why I'm suprised

Larry OBrien

OK. Yes, astronomy (and science) is full of wonderful surprises.

ChrisW

@Grasper I think you haven't learned 'special relativity': that no frame of reference is special; and that the motion of two object is relative (to each other) and not absolute

Grasper

5:29 PM

@ChrisW, it is going towards me if it's getting further, why not?

Larry OBrien

As I said, many objects that are "nearby" in the universe are actually blue-shifted (compressed) because they are approaching us faster than the rate of cosmic acceleration. This includes the Andromeda Galaxy.

Grasper

ok, I need to go, thanks for you input

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