DanMP

Not all. An extra scattering and absorption due to higher interstellar gas density would decrease luminosity of the source in any scenario. How was this addressed?

Long time ago I was thinking about a method to subject athletes to higher gravity in order to increase their performance. I imagined special suits in which I would add half a kilogram (sand or something) each day until they double their weight. The extra weight must be evenly distributed and they should wear the suit all the time, so the idea is not very practical. Maybe a space station with artificial (centrifugal) gravity would be, one day, used to increase athletes performance by increasing gravity.

I didn't check but I agreed that Friedmann equations would account for increased redshift due to higher density back than. Still, there are other possible issues due to that higher density: more matter (mostly hydrogen) between stars/galaxies would absorb and/or scatter more light, decreasing the luminosity and making the source to appear farther ... It is very obvious, so I expect to be accounted for, but how? Another thing, nobody commented about the video I posted: the new estimation of the age of the universe and the possibility that part of the redshift may be from "tired light". I wonder if the late would also account for the increased expansion caused(?) by "dark energy".

OK, thank you!

I knew that you would say that. We probably can't. So, the age of the universe was not "converted" to "today time" on Earth. Still, there may be an unaccounted "gravitational" redshift, because the "ancient" light originates from a denser region than we have now, here.

Yes, good point. Still, the universe was much denser than today. Comoving with what? Also, where, on Earth surface, between galaxies or on a neutron star "surface" 😀? Keep in mind that the Earth was not there in the beginning, nor any neutron star, nor the current intergalactic space, which is almost empty now. We shouldn't neglect gravitational time dilation, nor gravitational redshift. Probably they didn't, but I'm not sure. Slower than our clocks, situated on Earth today.

I understand what you mean (I am also "redshifted" 😛), but still, this forum is much better than physicsforums, where the moderators are very quick to close the topic, or restrict your right to write in it, when you insist asking uncomfortable questions. Just search/see my activity there. They are like a Physics Inquisition. This is not the case here. Regarding this thread, I believe that your misconception was to consider the balloon analogy with the Earth in the center ... Consider the Earth as another point on the surface of the inflating balloon and you will understand the responses you get. I also have some questions and observations regarding big bang theory: When they assessed the time from big bang, what reference frame they used? There is no absolute time. Just after big bang, the mass was confined in a small volume, yes? We know from GR that the clocks are slower when they are situated in/near a place with high density. Also light originating from such a place would be redshifted. Was this redshift considered (subtracted) when the speed of expansion was calculated? Last but not least:

You have to ask RossJ what exactly he meant. I think (but I'm not sure) that by isolation in time he meant that in the nucleus time may be dilated (gravitational time dilation). Such a thing may partially explain: To be honest I don't agree with most of what he wrote, but I intended to be positive.

Interesting idea. I thought about something similar many times. Anyway, you may want to read about the Thorium Nuclear clock project.

In OP, wei guo wrote about many issues: dark matter, dark energy, "extra position", extra dimensions and "extra parallel reality". Most of you cherry picked the "extra position: superposition" error and ignored the issues of introducing: extra dimensions, parallel universes and dark energy. They are distorting the instinct of reality as Wei Guo said. Do we really have evidence for extra dimensions and/or parallel universes? Why such things are accepted in mainstream physics? About dark matter I disagree with Wei Guo, but for the rest I'm not. There are real issues. About "extra position: superposition" error, yes it was an error, but I guess that he/she was thinking about things like the explanation for interference of individual particles in the double-slit experiment, where we consider the particle taking more paths in the same time, as if the particle can be present in more than one position at a time. I don't agree with such explanations either (I have another one, more intuitive). yes

Well, I'm not really interested in this alien theme/subject and it seems that neither are you, because if you were, you would know about ancient aliens/astronauts theory, also that an alien civilization may be much older/advanced than ours, that a probe may stay hidden long long time, and so on. I wrote about this subject mostly because I hoped that someone interested in it, and talented, would be inspired by my ideas and write nice SF novels or movie scenarios. I don't know about you, but I decided to let others take over, if they want/need to. For me it's enough.

No, I meant around us ... Another reason to have more alien probes, with different agendas, here.

0.1c with the technology that we can have or imagine today ... Even so, I wrote "under 100 light years", not 100 or over. If the distance is around 20 LY we can get info from the probe in 2-3 centuries. I also wrote about other ways to get new info + other reasons to send new probes. And there may be more than one civilization around ...

Well, if the target is not very far (under 100 light years), new data may be collected in few decades/centuries, both by the first probe and/or by new/enhanced telescopes, or new data may arise due to the developments in the targeted planet (first EM emissions and/or other activities, like atomic explosions, artificial satellites, etc.). Other reasons to send new probes may be: the technology needed becomes less expensive the new senders are not happy with the others agenda the enhanced technologies offer new, much better, approaches/possibilities (see here how I would do it) Anyway, If they are Bracewell probes, we shouldn't care. Just wait for them to contact us, when they consider appropriate. If they are, instead, alien probes sent to spy us prior to a future invasion, we need to properly investigate all the sightings and also to prepare a defense, although our nuclear arsenals may deter such plans, because on arrival they may find here a destroyed, uninhabitable planet ...

Maybe, but not necessarily. The Americans, Russians and Chinese are not getting along very well and have different space programs/projects ... And we are talking about centuries from now ... and maybe more civilizations ... So one planet may have dozens/hundreds different visiting probes. A Bracewell probe may delay the contact "until we achieve a certain level" (my option 1) or just be "afraid" of us (my option 2) and abort it. If option 3 is the one, then the probe is not a Bracewell probe, yes, but we shouldn't ignore that possibility.