Rotation Sensing Lasers in General Relativity: Some Technical Notes and Current Advances

Round 1

Reviewer 1 Report

Seethe attached file

Comments for author File: Comments.pdf

Author Response

Dear Editor,

We thank the referees for their efforts, noting that referee two suggests the manuscript can be published as it stands whilst referee 1 makes absolutely no comment with respect to the scientific content of the manuscript but rather the context in which the manuscript is placed. Below, we address this referee’s points in turn:

[1] The referee proposes the addition of 33 further references. We disagree with the referee, this is not appropriate for a manuscript of this size, neither are the references helpful for the scope of this paper. We wish to outline where terrestrial gyroscopy technically stands with respect to the highly demanding requirements for tests in general relativity.

[2] The referee comments that tests with geodetic satellites are controversial and that this should be mentioned. This is not the authors area of expertise and therefore, it would not be appropriate for us to make comments of this nature. Furthermore, we think this request is not within the scope of this contribution.

[3] The referee notes there is no mention of the GINGER project. We have added a reference to the manuscript in this regard.

[4] We have expanded our statement in respect of the outcomes of the GPB experiment as suggested by the referee.

[5] The referee notes we make no comparison with ring lasers from the ‘Stedman’ group in New Zealand. We respond that the referee appears to have misread the author list. We *are* in the ring laser group in New Zealand.

[6] Figure 7 has been rescaled as suggested by the referee.

[7] The conclusions have been modified as per the referees suggestion.

We trust this meets with the approval of the editor.

With Kind Regards

Ulrich Schreiber, on behalf of all authors.

Reviewer 2 Report

I have carefully read this manuscript and judge it to be well written, accurate and potentially quite useful to researchers in the field. I recommend publication as is.

Author Response

Dear Editor,

We thank the referees for their efforts, noting that referee two suggests the manuscript can be published as it stands whilst referee 1 makes absolutely no comment with respect to the scientific content of the manuscript but rather the context in which the manuscript is placed. Below, we address this referee’s points in turn:

[1] The referee proposes the addition of 33 further references. We disagree with the referee, this is not appropriate for a manuscript of this size, neither are the references helpful for the scope of this paper. We wish to outline where terrestrial gyroscopy technically stands with respect to the highly demanding requirements for tests in general relativity.

[2] The referee comments that tests with geodetic satellites are controversial and that this should be mentioned. This is not the authors area of expertise and therefore, it would not be appropriate for us to make comments of this nature. Furthermore, we think this request is not within the scope of this contribution.

[3] The referee notes there is no mention of the GINGER project. We have added a reference to the manuscript in this regard.

[4] We have expanded our statement in respect of the outcomes of the GPB experiment as suggested by the referee.

[5] The referee notes we make no comparison with ring lasers from the ‘Stedman’ group in New Zealand. We respond that the referee appears to have misread the author list. We *are* in the ring laser group in New Zealand.

[6] Figure 7 has been rescaled as suggested by the referee.

[7] The conclusions have been modified as per the referees suggestion.

We trust this meets with the approval of the editor.

With Kind Regards

Ulrich Schreiber, on behalf of all authors.

Round 2

Reviewer 1 Report

The major points of disagreement between the authors and this referee seem mainly to be those marked as [1], [2], [3] by the authors in their reply.

This referee respects the views by the authors, but not entirely.

If, on the one hand, it is acceptable to discard the point [2] about the LAGEOS and other proposed space based tests (points b) , b') and e) of my previous report), on the other hand, this referee finds inappropriate not citing the other ground-based experiments which have been proposed in the past (point c) of my previous paper). If the author prefer, they can shorten it by removing the Cerdonio's paper. The other ones should be cited. This referee does not see why also the other papers on GINGER have not been cited (point d) of my previous report). The authors, if they like, can omit the paper in Laser Physics. Furthermore, this referee does not see why relativistic gravimagnetism should not be introduced and referenced (point a) of my previous report). If the authors like, they can omit the Costa et al paper, and the second Schaefer paper, i.e. the one in Space Sci. Rev. Moreover, this referee does not see why the first two general references on GR (Debono et al. 2016 and Iorio 2015) should not be cited when GR is mentioned.

When the authors write: "as one might have hoped" about GP-B, it would be better to change it to "as one might have initially hoped". Moreover, this referee deems appropriate to cite here at least one of the two Everitt papers in the point e) of the previous report.

The authors should have in mind the broader readership of the journal Universe; as such it is quite appropriate to broaden the general context of the paper. 

Author Response

Dear editor,

We have received the attached reply on our manuscript revision and we are not sure of how
to respond to that. The scope of our contribution is to outline, where ring lasers are standing
with respect to the measurement of signals in GR, most prominently the Lense-Thirring frame
dragging. My co-authors and myself agree on the judgement, that the realization of an ground
based inertial experiment is exceedingly difficult and although we have already come a long way,
we are still facing a number of significant challenges. We concentrate on the application of large
inertial ring laser gyros and we mark where we are, with a clear focus on the experiment and the
respective technological aspects as we are dealing with them right now.

None of us authors has the capacity to discuss fundamental theoretical aspects. Neither would we
know enough about the controversies of the LAGEOS experiment (although I have high respect for that).
Last but not least, we know about and respect the GINGER proposal and we are contributing to this
as good as possible for us. However, at this point in time it is a proposal and not existing hardware. With
specifications and the overall approach still undergoing changes, we feel that we cannot rightfully quote on this
and believe that this will (or should) have room in a specific contribution from the principal working
group.

Having explained all this, I would like to ask you as the editor, how should we address the concerns
of reviewer one in the most practical and constructive way?

Kind regards, Ulrich Schreiber on behalf of the authors