A long time ago I had a blog, it was a good blog and before I left to go to Israel for 2 weeks I e-mailed my sister giving her posting privileges. She had a nice long post at the beginning and then stopped. I had hoped to return to a vibrant and alive blog discussing the issues which would come up in a century or two. This blog was beautiful it had comments and everything, but then Tobie killed it. So for once at least I’ll try to do something similar here (if you want more of these ask for a topic in the comments writing these is easy, coming up with ideas is hard).
The question I was considering was, what sort of effect special and general relativity would have on Halachah. Systematically I’m going to go through the issues and try to at least get some reasonable approach as to how the issues should be dealt with. The first and most obvious issue is how observing shabbas would change. Due to the large distances the orbit speed around the Earth would probably approach 24 hours in Earth time. However relativistically you would be compressing time at around a minute or two per hour at .99c (.99 speed of light). The standard issue for space is to use the time you came from. The question is, which time its perception of time, or your perception of time. For Yom Tov at least it seems like there is a requirement for the holidays to follow the seasons which would be a strong argument for the idea that you have to keep Shabbas every 15 minutes or so. However I nelieve there is a source for saying that you should keep what your time is and not base on what exists back on the rest of Earth. We know that in the time of Joshua the Sun and the Moon held still so that the Jews could defeat their enemies before Shabbat. However, assuming that this was a local miracle, the Jews should have gone with the regular clock. Instead they kept the ordinary clock and had Shabbat later. The argument could be made that the relativistic spaceship is in a similar scenario and therefore it should be it should be 24 hour days from space perspective which would mena nearly year long weeks on Earth. In addition there is a principle of Horaas Sha’ah. Therefore if you have these very long journeys with many years passing by, it may be necessary to change the definition of Shabbat in order to save it once you get to a star (which is a whole ‘nother can of worms). As for a bris it seems obvious that it is 8 days from the child’s perspective, but if you go with the Earth time shabbat idea then the Gemorah which says that we wait for one shabbas before the bris would support the idea of doing it as soon as possible
Another smaller issue is the issue of the shiurim for food. Relativity states that space is also compressed near light speed. Therefore the shiurim should be similarly compressed. The real issue is two fold. are these measurements from Earth or Space perspective and, secondly, if they are from Earth perspective, what is there reason. Is it a law from G-d with no reason in which case you would be able to drink a drop of wine for kiddush, or is it a shiur of satisfaction, in which case it would remain the same no matter what.
A third issue is (again assuming you use the Earth time Shabbas pshat) is what do you do when you pass near a star which deflects the Sun’s light. Do we say that you follow the actual position of the sun, or do we go by our percieved position of the sun.
The final issue is what to do in the case of a rapidly (9.000.0000 rph) kilometer wide spinning centrifuge. If you have food in there and drop treif food equal to 1/50 of the centrifuges contents, but on the relativistic edes, how is the food treated. In fact according to some opinions as long it was batul it is now considered kosher food completely even if could later combine to make more than 1/60 of the total contents. Therefore it is possible that you could eat something which is half treif, ( if the edges are spinnign rapidly enough) and still be allowed to eat it (presuming the food doesn’t add taste).
That is all (Tobie, I expect a link, considering…..)