How are light-years measured?

[gcthomas]

Certainly the length of a half year is half the length of time of a year, which perhaps would need to be determined.

As for an angle, you are talking about more than one. You are using an angle to get an angle somehow?

Multiple measurements are made over a number of years to reduce the uncertainty in what is a very difficult and exacting measurement.

This link has a brief summary - the graph at the bottom is very illustrative.

 

[Jacob]

Here is an explanation. It is quicker and easier for you to follow the link than for me to cut and paste.

Here seems to be the assumption: "This redshift appeared to be larger for faint, presumably further, galaxies."

 

[Jacob]

Multiple measurements are made over a number of years to reduce the uncertainty in what is a very difficult and exacting measurement.

This link has a brief summary - the graph at the bottom is very illustrative.

Of course we could determine the length of a year or the distance to the sun or moon.

 

[CabinetMaker]

Here seems to be the assumption: "This redshift appeared to be larger for faint, presumably further, galaxies."

That is my understanding. The faster it is traveling away, the greater the degree is is red shifted.

 

[Jacob]

That is my understanding. The faster it is traveling away, the greater the degree is is red shifted.

Consider if this observation is uniform for faint objects distributed around the universe (is it?) (from our perspective may be the only observation we can make), then what would prevent us from making the determination that we are at the center of the universe? Or does the evidence under the assumption given show us something different?

 

[CabinetMaker]

Consider if this observation is uniform for faint objects distributed around the universe (is it?) (from our perspective may be the only observation we can make), then what would prevent us from making the determination that we are at the center of the universe? Or does the evidence under the assumption given show us something different?

The last I had seen about this was the milky way is not the center. There have been measurements of velocities of other galaxies and the relative motion would tend to indicate the milky way is not in the center. To be honest, I don't know. It is not a subject I am particularly interested in so I don't spend a lot of time digging into it.

 

[Jacob]

The last I had seen about this was the milky way is not the center. There have been measurements of velocities of other galaxies and the relative motion would tend to indicate the milky way is not in the center. To be honest, I don't know. It is not a subject I am particularly interested in so I don't spend a lot of time digging into it.

Okay. Distances from the earth in its orbit to distant stars and galaxies in the universe is one thing. Velocities is another.

 

[gcthomas]

Consider if this observation is uniform for faint objects distributed around the universe (is it?) (from our perspective may be the only observation we can make), then what would prevent us from making the determination that we are at the center of the universe? Or does the evidence under the assumption given show us something different?

For the universe to have a centre it would need to have edges - it doesn't seem to have them. The assumption is that the universe looks approximately the same from everywhere, which is reasonable since everywhere looks the same from here.

 

[Jacob]

For the universe to have a centre it would need to have edges - it doesn't seem to have them. The assumption is that the universe looks approximately the same from everywhere, which is reasonable since everywhere looks the same from here.

I don't follow this assumption. What do you mean?

I thought the assumption was that the universe is expanding.

 

[gcthomas]

I don't follow this assumption. What do you mean?

I thought the assumption was that the universe is expanding.

The universe looks isotropic so is assumed homogeneous, and the evidence is that it is expanding at an accelerating rate.

It can be both.

 

[OCTOBER23]

UNINTELECTUAL,

WHY ARE YOU ACTING SO SIMPLE .

YOU HAVE BEEN HERE SINCE 2006


I thought the assumption was that the universe is expanding.
==================================

WHY IS IT EXPANDING ????

GOD WANTS TO FILL IT WITH LIGHT AND LIFE

AND WE ARE AT THE BEGINNING OF IT ALL.

 

[Jacob]

The universe looks isotropic so is assumed homogeneous, and the evidence is that it is expanding at an accelerating rate.

It can be both.

Can you explain what you have said here?

We assume the universe is expanding at an ever increasing rate, but whether time and space are involved here we have distances to objects in our solar system, and from the sun to every planet and the planets to their moons, the same distance or less or more? These objects are closer to us than the distance reaches of the universe.

 

[Jacob]

UNINTELECTUAL,

WHY ARE YOU ACTING SO SIMPLE .

YOU HAVE BEEN HERE SINCE 2006


I thought the assumption was that the universe is expanding.
==================================

WHY IS IT EXPANDING ????

GOD WANTS TO FILL IT WITH LIGHT AND LIFE

AND WE ARE AT THE BEGINNING OF IT ALL.

I'm not sure what you are asking me.

Expanding by velocity or acceleration or both?

And how do you know it is expanding?

And is it expanding at different rates in different locations/places?

 

[gcthomas]

Can you explain what you have said here?

We assume the universe is expanding at an ever increasing rate,

Not assumed - observed. The most distant galaxies have more redshift than near ones, which fits a uniform expansion. The furthest galaxies are fainter than they should be for their redshift, indicating that they are further than a simple Hubble expansion would predict, leaving the conclusion of accelerating expansion.

but whether time and space are involved here we have distances to objects in our solar system, and from the sun to every planet and the planets to their moons, the same distance or less or more? These objects are closer to us than the distance reaches of the universe.

Planets don't move apart when the universe expands since gravity, weak though it is, is strong enough to counter the expansion locally. Galaxy clusters are far enough apart that the gravity is a much weaker effect, and the expansion carries them apart.

 

[Jacob]

Not assumed - observed. The most distant galaxies have more redshift than near ones, which fits a uniform expansion.

Uniform in what way? From a particular point in the universe? Or do you mean to describe something different?

The furthest galaxies are fainter than they should be for their redshift, indicating that they are further than a simple Hubble expansion would predict, leaving the conclusion of accelerating expansion.

I believe you are talking about the steps to making the determinations that we do.

Planets don't move apart when the universe expands since gravity, weak though it is, is strong enough to counter the expansion locally. Galaxy clusters are far enough apart that the gravity is a much weaker effect, and the expansion carries them apart.

How would you compare our solar system to our galaxy in this regard?

 

[OCTOBER23]

And how do you know it is expanding?

-- I TALK TO GOD EVERYDAY

And is it expanding at different rates in different locations/places?

--WOULD YOU LIKE IT TO CONTRACT AND GIVE YOU A BIG HUG ??????

-- USE YOUR BRAIN UNTELECTUAL , GOD IS EXPANDING HIS KINGDOM .

 

[Jacob]

And how do you know it is expanding?

-- I TALK TO GOD EVERYDAY

And is it expanding at different rates in different locations/places?

--WOULD YOU LIKE IT TO CONTRACT AND GIVE YOU A BIG HUG ??????

No, I mean we have asked where the center of the universe is and if it is not us then where is it.

 

[TIPlatypus]

We measure how far away an object was using Pythagoras theorem. We can then determine how many light years it took for the light to get here. Then, if the object is moving, we can find out where it is now.

 

[gcthomas]

Uniform in what way? From a particular point in the universe? Or do you mean to describe something different?

By uniform, I mean that the distribution of galaxies and gas has the same broad pattern in every direction we look. The background radiation is very nearly identical in every direction - identical to such a degree it placed severe limitations on the possible differences. Since everywhere looks the same, and the same near as far, then the universe should look the same from any location and looking in any direction.

I believe you are talking about the steps to making the determinations that we do.

Yes. The steps to confirm the accelerating expansion have been carried out independently and there is a strong consensus.

How would you compare our solar system to our galaxy in this regard?

Our galaxy is gravitationally bound and immune to the current rate of expansion, as is the local cluster of galaxies and probably the extended cluster. The expansion effect is very weak on these relatively short distances.

 

[TIPlatypus]

And, if the Universe is shape like a Klein bottle (a four-dimensional sphere) then every point in the universe is the center of the universe. Consider the 3-dimensional equivalent of the surface of a sphere.