If our measuring tools are not as expanded as the light then only then can we measure whether or not the light is expanded. Otherwise if all space was expanding then that would mean we wouldn't notice because the measurer and the wavelength would be proportionate during expansion. So the only way we would know space is expanding by light expanding is if space around us wasn't expanding as well. Which doesn't make sense with the theory that space itself is expanding everywhere equally.


So what about everything? If galaxies can move apart then why doesn't everything move apart? Space itself is expanding, so why don't the earth and the moon separate? Gravity is a weak enough force and the masses of the earth and moon are relatively small. Or why don't atoms break apart?

there would still be redshift even if 2 galaxies were moving away from one another in a non-expanding universe.

as for the last part, it's like i said, supermassive black holes are hypothesized to be the reason galactic matter stays together, while moving away from one another. it's not about the gravity between the earth and the moon, its about all the matter in a galaxy being attracted to the supermassive black hole at the center. although it is largely bound by the mass of dark matter. atoms dont break apart because the snf is millions of times stronger than gravity.

This post was edited by dothe on Mar 9 2011 11:37pm

Yes, but that wouldnt' be because of space epxanding but because of the doppler shift, which causes a change in wavelength in light that is measurably different from the measuring apparatus' scale.

Space itself is expanding. Gravity is weak enough to cause gravitationally attracted objects to spread apart. So why don't the moon and the earth separate?

yes thats redshift..you said "only then can we measure whether or not the light is expanded". the expanding space theory is based on the fact that basically all galaxies are moving away from us. that wouldnt make sense in a static, closed universe. the redshift is just proof that they are moving away.

"Gravity is weak enough to cause gravitationally attracted objects to spread apart." lol interesting sentence

"So why don't the moon and the earth separate?"

gravity on a large scale (galaxy) is actually extremely strong.

This post was edited by dothe on Mar 10 2011 12:00am

Yes, but they claim that they can also measure the expansion of the universe through the expansion of space itself. Even if they only measure redshift through doppler shift and understand from that the expansion of the universe then we couldn't say space itself is expanding with certainty.

That sentence was complete fail. I meant to say "Gravity is weak enough to allow gravitationally attracted objects to spread apart [due to space expanding].

Well yeah, but since gravity is an incredibly weak force it takes a lot of mass to pull things together strongly.

Somehow space expanding is moving galaxies and stars but it isn't moving any other matter or causing any bonds to break besides gravitational. It must be a weak expansion, but I've heard it's faster than light.

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not sure if this was pointed out...but the moon does rotate ever so slowly

LOL the moon is ever so slowely drifting apart from the earths gravitation pull.
Any point you just made has been shut down