Recent content by Jorrie

Lightcone8 does not allow for high Omega or very small Lambda, so I'm not sure that collapse can happen with these limitations. Any small Lambda may quickly become dominant again. As a matter of fact it seems to crash if I set Lambda to 0.001 and Omega to 1.5. Will have to investigate that. I...

Just go to 'Column definition and selection'. I usually click 'none' and then select the two or three that I need. The default selections are just to give an idea of how it works.

Not precisely, but you can get close enough for all practical purposes by playing around with the input parameters and output options. E.g. ##\Lambda = 0.0000001##, set the output scaling to Normalized, select Chart and set hor and vert scales appropriately: For Open and Closed cases, you play...

It may just be a cashed issue, because for me it gives:

Absolutely cool thanks! Just a question, do you assume that the 'lab' at x=0 has negligible mass, or does it not feature in the final analysis?

Agreed, but then we have a lab with non-negligible mass in the middle. Why not make the two labs (that I had in my last post) two nano-satellites as the test objects and let them do the measurements. They can have the added advantage of tiny boosters to accurately find the 'critical distance'...

Hmm, it looks like I will have to find a point at the center of some large void, separate my two labs by the calculated distance D apart and see if they fall towards each other or the other way. The reason for two labs is that they can continuously observe known emissions from each other and...

After this reply, the thread went into a "highly A" level, so I thought about a way to simplify it somewhat. Is it possible to do away with the cable and all its complexities? Perhaps. If we (one day) have the technology to put two labs, each of non-negligible mass M, somewhere in the...

Sure, but the two spaceships that hook up the cables with the lab will take much longer than that. The cables could presumably be rolled out from the two spaceships with just the right tension to keep the two masses at the required constant proper distance from the lab. It will be an...

Yes, I think that limit would be the Hubble radius, relative to the position of the lab. But I also think that the low speed/weak field equations will break down long before that, as the peculiar radial velocity grows to a significant fraction of the speed of light. This is all rather...

It is easy to calculate the mass of the cable and also how it is distributed. What is not so easy is to calculate is the force contributed by the distributed mass. The cable mass will contribute zero at the lab and more and more for the more distant parts being forced off their geodesics. H...

Correct, but I was thinking that the very symmetrical situation would enable a fairly reliable OOM determination. As always, the "devil" might well be in the details...

The idea was that the cables are only attached to a strain gauge in the relatively small lab; so the lab itself is under negligible strain.

I apologize to all who have misunderstood the scenario that I have presented. I should have made it more clear that I was talking about cosmological distances and I should have done a better job of the schematic. That said, I should also have stressed that the equation that I've used is a weak...

In order to make it as simple and non-controversial as possible, I propose a setup where inhomogeneity and change of reference frames play as little role as possible, i.e. in free space and with its center of mass comoving. I'll call that point the origin and set up my lab there. Rockets...