Stupid Questions Open Thread Round 2

OpenThreadGuy

From Costanza's original thread (entire text):

This is for anyone in the LessWrong community who has made at least some effort to read the sequences and follow along, but is still confused on some point, and is perhaps feeling a bit embarrassed. Here, newbies and not-so-newbies are free to ask very basic but still relevant questions with the understanding that the answers are probably somewhere in the sequences. Similarly, LessWrong tends to presume a rather high threshold for understanding science and technology. Relevant questions in those areas are welcome as well. Anyone who chooses to respond should respectfully guide the questioner to a helpful resource, and questioners should be appropriately grateful. Good faith should be presumed on both sides, unless and until it is shown to be absent. If a questioner is not sure whether a question is relevant, ask it, and also ask if it's relevant.

Meta:

How often should these be made? I think one every three months is the correct frequency.
Costanza made the original thread, but I am OpenThreadGuy. I am therefore not only entitled but required to post this in his stead. But I got his permission anyway.

From Costanza's original thread (entire text):

This is for anyone in the LessWrong community who has made at least some effort to read the sequences and follow along, but is still confused on some point, and is perhaps feeling a bit embarrassed. Here, newbies and not-so-newbies are free to ask very basic but still relevant questions with the understanding that the answers are probably somewhere in the sequences. Similarly, LessWrong tends to presume a rather high threshold for understanding science and technology. Relevant questions in those areas are welcome as well. Anyone who chooses to respond should respectfully guide the questioner to a helpful resource, and questioners should be appropriately grateful. Good faith should be presumed on both sides, unless and until it is shown to be absent. If a questioner is not sure whether a question is relevant, ask it, and also ask if it's relevant.

Meta:

How often should these be made? I think one every three months is the correct frequency.
Costanza made the original thread, but I am OpenThreadGuy. I am therefore not only entitled but required to post this in his stead. But I got his permission anyway.

Also, an object distant enough on way-bigger-than-galaxy-superclaster scale can have Hubble speed more than c relative to us.

Are you sure about this? I don't understand relativity much, but I would suspect this to be another case of "by adding speeds classically, it would be greater than c, but by applying proper relativistic calculation it turns out to be always less than c".

It looks like it is even weirder.

Proper relativistic velocity arithmetics you mention is about special relativity theory - i.e. local flat-space case. Hubble runaway speed is supposed to be about global ongoing space distortion, i.e. it is strictly about general relativity. As far as I know, it is actually measured based on impulse change in photons, but it can be theoretically defined using time needed for a lightspeed round-trip.

When this relative speed is small, everything is fine; if I understand correctly, if Hubble constant is constant in the long ... (read more)

21

Stupid Questions Open Thread Round 2

21

21

21

Stupid Questions Open Thread Round 2

21

21