Recent content by laymanB

Thanks. I am trying to learn the math so one of these days I can start posting at "I". I am not trying to dispute the majority consensus among the cosmological community that the best fit data is for a FRW spacetime that is flat and infinite, given a simply connected, trivial topology. What I...

So if our observable universe is ##E^3## according to our best observations, we conclude if it is simply connected that it is spatially infinite? Based on what foliation is this definition of spatially infinite made?

Man I have a short memory! Thanks. Edit: So let's forget about measuring time since the Big Bang, being this is an invariant proper time. The question that I'm trying to pose is that if we don't use invariant quantities and call any spacetime spatially "infinite" based on some arbitrary...

Unless I'm not thinking about it correctly, I agree. It seems to me that the relative aspect of relativity, where you can choose arbitrary coordinate charts and foliations and none are more correct or privileged seems to lend itself to equivocation when communicating a theory. That may not be a...

Yeah sorry, I realize you said that in your previous post. Thanks for all the insight and help.

Okay, that makes more sense. So, if you are on a null line on the edge of the cone, you do not ever cross one of these hyperbolas of constant proper time because they are asymptotic to the null lines, therefore the null line has no proper time? And the straight line in the center taking the...

That helps, thanks. Me neither. :smile: But what I was trying to convey was what Aguirre is referencing from about 24:00 to 25:00 in the above video. Where he is showing a number of spacelike surface hyperbolas that can be chosen to represent the Minkowski spacetime as infinite within a future...

So this is the YouTube video that got me thinking about this thread topic. If you watch from 22:00 to around 30:00 you will get the gist of the argument from Anthony Aguirre. So essentially he is saying you can have bubble universes that are finite or infinite depending on how you slice them...

@Bandersnatch thanks for that thread. I read the last page of posts and those where the kinds of questions I was having and the usual helpful posts by @PeterDonis . So I guess my next question would be: Can you compare spacelike slicing between different spacetimes? In other words, can we take...

I agree that when reading about eternal inflation models, one is not usually told explicitly that they require additional spatial dimensions. But I don't see how you can have a logically consistent eternal inflation model without extra spatial dimensions, unless each bubble universe is finite in...

That makes more sense. Thanks.

I was watching a conference on YouTube about cosmology and one of the speakers was Anthony Aguirre. He was giving a lecture on different cosmological models that are infinite in time as well as space. Here is a link to one of his papers and one of the models he was presenting. There is not much...

If this hypothesis was correct and the universe is not expanding, is eternal, and is evolving as a function of time, why would not all the stars have burned out an infinite time ago?

OK, now I understand you better. Thanks for elaborating.

I'm not sure I'm following your reasoning, but it could just be me, I don't know QED. If you want to use the reduction to absurdity way of reasoning to show that the "constants" are actually variables, then it seems to me that you should treat them as constants and show that the conclusion of...