Talk:Galilean invariance

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[edit] einstein's elevator vs. einstein's cabin

Google searches for einstein's elevator and einstein's cabin give:

1. Results 1 - 100 of about 442 for "einstein's elevator".
2. Results 1 - 3 of 3 for "einstein's cabin".

All three results for einstein's cabin refer to the scientist's own residence, not his thought experiments.

This article says Einstein's elevator is used in Einstein and Infeld (1938), which I have somewhere. The article would benefit from any references in which einstein's cabin is used in a thought experiment.

As there appears to be a low-level edit war over this matter, here are two questions:

1. What did Einstein say?
2. Why can't there be two examples, contrasting the inertial and accelerated scenarios?

The article currently reads: "In special relativity, one considers Einstein's cabins, cabins that fall freely in a gravitational field." Is it really necessary to consider so many cabins? I find one cabin charming, but a whole rain of them frightening. :-)

--Jtir 16:38, 23 September 2006 (UTC)

(transfered from User talk:Mct mht)

thanks for the heads up. both "cabin" and "elevator" can be found in the literature. they convey the same idea. no objections from me if you strongly prefer elevatorvand wanna put it back. Mct mht 19:12, 23 September 2006 (UTC)

I like cabin in this example, because the cabin is in free fall. An elevator has a cable that can be used to accelerate it, so it provides a somewhat different example. Do you have a particular source, such as textbook, that uses cabin. I would like to add some references to this article and a title and author is all I would need. If you like, you can put it here and I will do the edit. --Jtir 19:43, 23 September 2006 (UTC)

[edit] examples of inertial frames in the lead paragraph

The lead paragraph reads very nicely until the last sentence: The fact that the earth on which we stand orbits around the sun at approximately 18 km/s offers a somewhat more dramatic example [of an inertial frame].

The Earth has a gravitational field, is subject to earthquakes, and is orbited by a moon, so it is not an example of an inertial frame.

Examples of nearly inertial frames in a gravitational field are the Vomit Comet and the International Space Station. As the article notes later, microgravity is still present in those frames.

--Jtir 18:58, 23 September 2006 (UTC)

The Earth also rotates. The ship example is triply qualified by assuming the ship moves "... at constant speed, without rocking, on a smooth sea...". Perhaps something similar could be done for the Earth example.--Jtir 17:36, 24 September 2006 (UTC)

I'm not sure how relavent this is, since i'm having trouble understanding Newtonian Relativity, the earth does rotate around the sun, as does the International Space Station around the earth, meaning that they are accelerating, as acceleration is not only speed but the direction of motion as well. So, take that into consideration, whoever understands this better than i.--The Sporadic Update 19:08, 28 September 2006 (UTC)

Indeed. The Earth also follows a (nearly) circular orbit. It has a constant speed of 18 km/s, but is continuously accelerating to follow a curved path; it is an example of a decidedly non-inertial frame. TenOfAllTrades(talk) 19:27, 3 October 2006 (UTC)

I think that what may have been meant originally is that the orbital acceleration is effectively "cancelled" by the gravitational field of the Sun. The same thing may be said about satellites in Earth orbit. The article needs to help sort this out. --Jtir 19:50, 3 October 2006 (UTC)