Wane tsarin haɗin kai ne Albert Einstein ya yi aiki a kai amma bai yi nasara ba? Bisa ga tambayar da ta gabata, ka rubuta mahallin da ke ɗauke da amsar. Zai iya zama jumla 1 - 20. Abubuwan da ke ciki:
Ci gaban ka'idoji na asali don dakarun ya ci gaba tare da haɗin ra'ayoyi daban-daban. Misali, Isaac Newton ya hada karfi da ke da alhakin abubuwan da ke faduwa a saman duniya tare da karfin da ke da alhakin zirga-zirgar injinan sararin samaniya a cikin ka'idar jan hankali ta duniya. Michael Faraday da James Clerk Maxwell sun nuna cewa ƙarfin lantarki da magnetic sun haɗa kai ta hanyar ka'idar ka'idar lantarki. A cikin karni na 20, ci gaban kimiyyar lissafi ya haifar da fahimtar zamani cewa abubuwa uku na farko (duk sai dai nauyi) sune bayyanar kwayoyin halitta (fermions) suna hulɗa ta hanyar musayar kwayoyin halitta da ake kira gauge bosons. Wannan daidaitaccen samfurin kimiyyar kimiyyar kwayoyin halitta ya nuna kamance tsakanin sojojin kuma ya jagoranci masana kimiyya suyi hasashen hadewar karfi da karfi na lantarki a cikin ka'idar lantarki mai rauni wanda daga baya aka tabbatar da shi ta hanyar kallo. Cikakken tsari na daidaitaccen samfurin ya yi hasashen wani tsari na Higgs wanda ba a lura da shi ba tukuna, amma lura kamar oscillations na neutrino ya nuna cewa daidaitaccen samfurin bai cika ba. An gabatar da Babban Ka'idar Haɗakarwa wanda ke ba da damar haɗuwa da hulɗar lantarki mai rauni tare da ƙarfi mai ƙarfi azaman yiwuwar tare da ra'ayoyin da ake nema kamar su supersymmetry da aka gabatar don saukar da wasu daga cikin matsalolin da ba a warware su ba a cikin kimiyyar lissafi. Masana ilimin kimiyyar lissafi har yanzu suna ƙoƙarin haɓaka samfuran haɗin kai masu daidaituwa waɗanda za su haɗu da dukkanin ma'amala huɗu na asali a cikin ka'idar komai. Einstein yayi ƙoƙari kuma ya kasa a wannan ƙoƙari, amma a halin yanzu mafi mashahuri tsarin amsa wannan tambaya shine ka'idar kirtani.:212<unk>219