Путешествие на Луну
Reply from the Observatory of Cambridge
Atmidnightshewillbeinperigee,thatis,athershortestdistancefromtheearth,andatthesamemomentshewillbecrossingthezenith.
Onthefifthquestion,"Atwhatpointintheheavensoughtthecannontobeaimed?"
Answer.—Theprecedingremarksbeingadmitted,thecannonoughttobepointedtothezenithoftheplace.Itsfire,therefore,willbeperpendiculartotheplaneofthehorizon;andtheprojectilewillsoonestpassbeyondtherangeoftheterrestrialattraction.But,inorderthatthemoonshouldreachthezenithofagivenplace,itisnecessarythattheplaceshouldnotexceedinlatitudethedeclinationoftheluminary;inotherwords,itmustbecomprisedwithinthedegrees0°and28°oflat.N.orS.Ineveryotherspotthefiremustnecessarilybeoblique,whichwouldseriouslymilitateagainstthesuccessoftheexperiment.
Astothesixthquestion,"Whatplacewillthemoonoccupyintheheavensatthemomentoftheprojectile’sdeparture?"
Answer.—Atthemomentwhentheprojectileshallbedischargedintospace,themoon,whichtravelsdailyforward13°10’35’’,willbedistantfromthezenithpointbyfourtimesthatquantity,i.e.by52°41’20’’,aspacewhichcorrespondstothepathwhichshewilldescribeduringtheentirejourneyoftheprojectile.
