Question Is Gravitational Wave the same as Gravity?

[J@i]

Is Gravitational Wave the same as Gravity?

 

[Helio]

Is a water wave the same as water?

A rock thrown in a calm pond suddenly applies pressure on the water it displaces, and a ripple-effect takes place on the surface. Similarly, a sudden shift in mass also produces a similar result on the fabric of spacetime, as predicted in GR. Mass curves spacetime, so sudden movements can form noticeable waves, though they are incredibly small in amplitude after many trillions of miles.

 

[Jzz]

Who can tell. With space (according to astrophysicists) expanding at several times the speed of light (!) one would have thought that gravity and electromagnetism would have been affected.

 

[Helio]

Who can tell. With space (according to astrophysicists) expanding at several times the speed of light (!) one would have thought that gravity and electromagnetism would have been affected.

That‘s an important thought for the events in the first second. Today, expansion locally is next to nothing. It’s only~ 70 kps at 1Mpc.

 

[billslugg]

Due to the expansion of space, the Sun and Earth are separated by an additional inch every day.

 

[Jzz]

That‘s an important thought for the events in the first second. Today, expansion locally is next to nothing. It’s only~ 70 kps at 1Mpc.

Thank you for your input. Surely this is one of the paradoxes of modern day physics: "everywhere else" the Universe is expanding at faster than light speeds but 'locally' there is hardly any expansion at all. The keyword here is the Universe is still expanding:

"Assuming that dark energy continues to make the universe expand at an accelerating rate, in about 150 billion years all galaxies outside the Local Supercluster will pass behind the cosmological horizon. It will then be impossible for events in the Local Supercluster to affect other galaxies." quote from wikipedia.

As can be see there are many self contradictions.

 

[billslugg]

It is not true that the universe is expanding faster than light "everywhere else". It is doing so only at the cosmological horizon, 16 billion light years away. Please restate one of your claimed contradicitons, I am not following your logic.

 

[Jzz]

It is not true that the universe is expaning faster than light "everywhere else". It is dois so only at the cosmological horizon, 16 billion light years away. Please restate one of your claimed contradicitons, I am not following your logic.

Is it possible to get so mired down in ideology, that it is impossible to see the lack of logic in ones dogma? I believe it is. For instance, if space is only expanding at the cosmological horizon of the Universe, sixteen billion light years away, how is it possible for the galaxies that are within view (less than 13.7 billion years or so) to have their spectra red shifted to an extent that shows they are moving several times the speed of light? If this expansion can affect galaxies and stars billions of light years distant from the cosmological edge, surely it can affect the rest of the Universe too?

Here is a quote from Ethan Siegel that supposedly explains cosmological expansion. Looked at logically it is pretty shaky ground. Like saying and proving that 2 + 2 = 4, which it doesn't, or does it:

"But even though the fabric of space is expanding throughout the Universe — everywhere and in all directions — we aren't. Our atoms remain the same size. So do the planets, moons, and stars, as well as the distances separating them. Even the galaxies in our Local Group aren't expanding away from one another; they're gravitating towards one another instead. Here's the key to understanding what is (and isn't) expanding in our expanding Universe..............."

 

[billslugg]

Space is expanding faster than light only at the cosmological horizon, but is expanding at very high speeds far short of that horizon. It is a gradual increase from Earth to the horizon.

The spectra of galaxies within view is not shifted by velocities faster than the speed of light. Their velocity is some fraction of the speed of light. Recession at the speed of light only occurs once one reaches the cosmological horizon.

The reason we cannot see the expansion of spacetime in our locality is how small it is in our locality. The rate is 70 kilometers per second per megaparsec. This is a rate of 2.3e-18 meters per second per meter. The Sun, which is 1.5e11 meters away from us thus moves .35 microns per second further away. Over one year this amounts to only ten meters. This is too small to measure.

Similarly, the amount that our atoms expand is much too small to measure.

The reason that nearby galaxies are moving towards us is local gravitational attraction which overwhelms the movement due to the expansion of spacetime.

 

[Helio]

Is it possible to get so mired down in ideology, that it is impossible to see the lack of logic in ones dogma? I believe it is. For instance, if space is only expanding at the cosmological horizon of the Universe, sixteen billion light years away, how is it possible for the galaxies that are within view (less than 13.7 billion years or so) to have their spectra red shifted to an extent that shows they are moving several times the speed of light? If this expansion can affect galaxies and stars billions of light years distant from the cosmological edge, surely it can affect the rest of the Universe too?

Yes.

The balloon analogy helps here because the greater the distance from any given spot, the greater the expansion speed it will have from the spot. I like to think of a rubber band that is nailed at one end, pulled at the other. The amount of movement with time (speed) increases with distance

The fact that the more distance regions observed are receding from us faster than light is why theDoppler redshift model fails, hence the cosmological redshift is used.

"But even though the fabric of space is expanding throughout the Universe — everywhere and in all directions — we aren't. Our atoms remain the same size. So do the planets, moons, and stars, as well as the distances separating them. Even the galaxies in our Local Group aren't expanding away from one another; they're gravitating towards one another instead. Here's the key to understanding what is (and isn't) expanding in our expanding Universe..............."

I agree with this. Local expansion is very easily overcome by local forces. Earth holds its orbit rather than moving outward with expansion. But this seems to be a matter of debate, admittedly.

iPhone