Timeline for How strong is the gravity from half of the distant universe?
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
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| Apr 26, 2017 at 21:37 | comment | added | Jonathan | @Brian Tung I would especially like to see the effect of the "dense edge" of the universe, where the cosmic microwave background comes from, and beyond. Not 100% sure if the approximation using the average density of the universe gets us there or not, but it is a reasonable approach. | |
| Apr 26, 2017 at 13:37 | history | tweeted | twitter.com/StackAstronomy/status/857227141225820160 | ||
| Apr 26, 2017 at 3:22 | comment | added | userLTK | @PM2Ring Well, you did the calculations and I didn't, so props for that. Dark energy changes the entire thing. Straight gravity, I think the pull in this theoretical is enormous, which is why I replied to mikey's post. With dark energy, the math is over my pay-grade. Props for working it out though. | |
| Apr 26, 2017 at 2:12 | comment | added | PM 2Ring | @userLTK Although I assumed that the observable universe isn't expanding, I kind of included dark energy in my calculation because I used the full critical density, so my mass estimate is that of the total energy content of the observable universe - normal matter and energy as well as dark matter and energy. | |
| Apr 26, 2017 at 1:29 | comment | added | Jonathan | @zephyr Yes, I believe so. This question arose from an interesting variation on the original question where I consider the whole universe vs half of it. In the original question, the full shell has the force cancelling out, except maybe for stretching space. | |
| Apr 26, 2017 at 1:26 | vote | accept | Jonathan | ||
| Apr 25, 2017 at 23:49 | comment | added | userLTK | @mikey Gravity falls off by the square but the mass of everything within 2 light years vs 1 light year increases by the cube if we assuming uniform density. It wouldn't be negligible at all. It would start out negligible for near-by it would grow. Dark energy however is the wild card. It's impossible to work out an answer with Dark Energy. Ignoring the dark energy and expanding universe, it could be done I've not wanted to do the math cause I do math badly and I don't speak Jax very well, but I think, off the top of my head, the gravitation would be surprisingly high. | |
| Apr 25, 2017 at 23:00 | comment | added | Brian Tung | How abstract are we talking about this? Do we assume a uniformly dense universe (at sufficiently large distance scales)? | |
| Apr 25, 2017 at 13:53 | answer | added | PM 2Ring | timeline score: 5 | |
| Apr 25, 2017 at 13:40 | comment | added | zephyr | Is this question sufficiently different from your other question? | |
| Apr 25, 2017 at 12:15 | comment | added | Jonathan | @mikey Excellent starting point, yes, that factor will certainly come into play. Note that the universe used to be extremely dense, and the gravity from that should be reaching us from the region where the cosmic microwave background was emitted and beyond. We are effectively seeing and probably experiencing gravity from the past universe. | |
| Apr 25, 2017 at 9:56 | comment | added | user15317 | Not an answer, but it will be useful to consider that gravity falls off as 1/r^2. At 10 billion light years (much less than half the radius of the known universe), the effect would likely be negligible (maybe barring supermassive black holes). | |
| Apr 24, 2017 at 23:46 | history | asked | Jonathan | CC BY-SA 3.0 |