Astronomers See Evidence of Something Unexpected in the Universe

GR does posit that the speed of light is the same for all observers in all reference frames.

All inertial reference frames, actually.

Unless I am missing the point General Relativity actually assumes that standard clocks and rulers don't exist and then makes predictions for what we should see here based on that.

Yes, I agree with that.

Thus it could be that local clocks and rulers show that the cosmos appears to be expanding locally, yet there is no meaning of "expanding" that applies to the cosmos as a whole.

To be clear: I'm suggesting everywhere in the cosmos, local observers might see the local appearance of expanding. And yet that does not make "expanding" a meaningful term to apply to the cosmos as a whole.

NoNukes makes the point that Creation was focused on time, but Creation wasn't capable of generalizing and made his points with examples. Time was his initial example, but he moved on to say we couldn't know relativity behaved the same in deep space as it does here (Message 682), and he said we couldn't know the speed of light out there is the same as here (Message 703). He used examples rather than generalizations, but he obviously believed we can't know whether scientific laws out there are the same as here.

All of creation's conclusions were based on time not behaving the same as it does here. For example, he said that we could not know how far light traveled because we did not know the rate of time passage in those distant places. He may well have believed more than that, but at this point, you appear to be putting ideas into the rather small place that was creation's thinking on this topic.

Despite the differences, I would respond to both nwr and creation in pretty much the same way Taq has already answered. We have at least some evidence for the position that our formulation of physics is applicable in distant space, while the opposing position is just denial and supposition.

Hi NoNukes,

NoNukes writes: All of creation's conclusions were based on time not behaving the same as it does here.

Just one of my foolish thoughts but I thought it was a given that time in space does not behave the same as it does on earth.

In one of the twin's taking a journey into space and returning that twin is supposed to have aged a lot less than the twin on earth.

So wouldn't that mean that the speed something traveled in space would change time compared to here on earth.

Just asking.

God Bless,

Just one of my foolish thoughts but I thought it was a given that time in space does not behave the same as it does on earth. In one of the twin's taking a journey into space and returning that twin is supposed to have aged a lot less than the twin on earth.

You are confused and if you are looking for my help, you can stay confused. I am not going to discuss special relativity with you again. You are the one adult on earth with whom I refuse to have a dialog about physics.

Edited by NoNukes, : No reason given.

Edited by NoNukes, : No reason given.

Special Relativity posits that all inertial observers agree on the speed of light.

General Relativity, lacking global inertial observers (i.e in general there are no inertial frames) doesn't even posit that. The speed of light will be observer dependent.

nwr writes: Thus it could be that local clocks and rulers show that the cosmos appears to be expanding locally, yet there is no meaning of "expanding" that applies to the cosmos as a whole.

If the expansion was local then all galaxies outside of the local area would be redshifted by the same amount, but they aren't. More distant galaxies are redshifted more strongly than nearby galaxies, and there isn't a point in the cosmos where redshift caps out. The only explanation that makes sense is that the entire length of space between us and all galaxies is expanding at the same rate per unit of length.

Son Goku writes: Special Relativity posits that all inertial observers agree on the speed of light. General Relativity, lacking global inertial observers (i.e in general there are no inertial frames) doesn't even posit that. The speed of light will be observer dependent.

Could you describe a situation where the speed of light is observer dependent within GR?

ICANT writes: Just one of my foolish thoughts but I thought it was a given that time in space does not behave the same as it does on earth. In one of the twin's taking a journey into space and returning that twin is supposed to have aged a lot less than the twin on earth. So wouldn't that mean that the speed something traveled in space would change time compared to here on earth.

Clocks do tick at different rates with respect to gravity and relative velocity. The famous Hafele-Keating experiment used atomic clocks on jetliners to determine that clocks tick faster further away from the Earth's center of gravity. In modern times we observe that the clocks on GPS satellites tick at a higher rate than those same clocks on the surface of the Earth. However, the differences are in the nanosecond range, so not that significant.

Cosmologically, you don't see significant time dilation until you get to the highest redshifted galaxies. In these cases, scientists have seen time dilation in the form of type Ia supernovae taking longer to brighten and dim compared to the same supernovae in nearer and less redshifted galaxies. Within our own galaxy, movements are dominated by gravity so any redshift we see is due to movement through space instead of expansion of space itself.

I don't know how much detail you want (actual calculations?), but if you shine light on a mirror above the event horizon of a black hole and time the return of the beam and the distance, you won't get the usual speed of light.

If the expansion was local then all galaxies outside of the local area would be redshifted by the same amount, but they aren't.

Sigh!

This is still a complete misunderstanding of what I have been saying.

nwr writes: This is still a complete misunderstanding of what I have been saying.

You can hardly blame us if you then refuse to clear up any misunderstandings.

Son Goku writes: I don't know how much detail you want (actual calculations?), but if you shine light on a mirror above the event horizon of a black hole and time the return of the beam and the distance, you won't get the usual speed of light.

I would assume that this would also be true for a laser beam shot from space and bouncing off of a mirror 500 miles below on the face of the Earth (but obviously with less of a difference than with a black hole)?

Yes indeed, the black hole is a dramatic exaggeration where it would be obvious to a human, but it'd be true above the Earth.

For spherical gravitational fields the speed would be:

where c is the usual speed with no gravity around and the speed in the presence of gravity. M the Mass of the body, G is Newton's Constant and r is the radius of the observer.

For the case you mentioned that results in light being less than a m/s slower.

Edited by Son Goku, : No reason given.

Talk of "the expanding universe" implicitly assumes that there is a yardstick (for measuring distance) which can be used throughout the cosmos and for all time. I cannot see any reason to believe that. We use a local yardstick defined in terms of local features. And it may well be that every location can have a local yardstick. But I cannot see any certainty that we can put these together to have a cosmos-wide yardstick. It might be that there are local distance functions at every location, but no single distance function that can be used across the entire cosmos. And there could be similar issues with the measurement of time and with the measurement of other physical properties.

The map of distance to red-shift is empirically derived and is checked against phenomena that do not require measuring the travel of light. In addition, in those few situations where we can use the speed of light to make a measurement, such as SN 1987a, we have confirmation using an additional method.

Against all that we have your proposal of a completely different universe for which we have no confirming science whatsoever. Why do you believe in your model over those of others?