crazunggoy47 OP t1_jajyba4 wrote on March 1, 2023 at 11:34 PM

Reply to comment by Any-Broccoli-3911 in Why do cosmologists say that gravity should "slow down" the expansion of the universe? by crazunggoy47

Hmm. So if I understand you correctly, you're saying that an object that's moving away from us due to cosmic expansion has a finite kinetic energy (relative to us). So, from our perspective we should "expect" that kinetic energy to be falling, as our own gravity pulls them back in.

And then that galaxy, will also see the exact same thing. From its perspective every other galaxy is fleeing *it*. And if every galaxy sees this, and it just so happens that every trajectory has too little KE, then every galaxy would see the other galaxies crashing down on them.

Is that right?

Any-Broccoli-3911 t1_jajymds wrote on March 1, 2023 at 11:36 PM

Yes, though the galaxies that are outside the local group have enough energy not to crash into us even if we don't consider dark energy which will push them away even faster. Without dark energy, they would decelerate relative to us, but still always going away.