// \$Id: sem.C,v 1.3 2006/12/05 08:59:12 jingliu Exp \$ // include std C++ IO functions #include #include using namespace std; // include necessary header files provided by ROOT (the declarations // of Int_t, Double_t, etc. are automatically included when you // include one of these header files, eg. TMath.h) #include using namespace TMath; #include // http://root.cern.ch/root/html/TVector3.html #include #include #include const Int_t n = 3; // Sun, Earth and Moon // change rate of the position TVector3 fx(Int_t i, TVector3 *x, TVector3 *v) { return v[i]; } // change rate of the velocity TVector3 fv(Int_t i, TVector3 *x, TVector3 *v) { Double_t GM[n]; // G*M GM[0] = 4.0*Power(Pi(),2); // mass of the Sun GM[1] = GM[0]*3.00e-6; // mass of the Earth GM[2] = GM[1]*1.23e-2; // mass of the Moon // by default all vector components are initialized to zero TVector3 r; // relative position vector TVector3 a; // acceleration for (Int_t j=0; j= 3) { dt = atof(argv[1]); Tmax = atof(argv[2]); } else { dt = 0.001; Tmax = 1; } */ ofstream dat[n]; dat[0].open("sun.dat"); dat[1].open("earth.dat"); dat[2].open("moon.dat"); // initialize system Double_t t = 0; Double_t Ve=6*3.14159265; // velocity of the Earth Double_t R=0.985; // R = V_moon/V_earth TVector3 x[n], v[n]; // position & velocity vectors TVector3 xp[n], vp[n]; // temporary vectors for calculation x[0].SetXYZ(0,0,0); // Sun in Origin x[1].SetXYZ(0.2,0,0); // Earth is 0.2 A.U. away from Sun (periapsis) x[2].SetXYZ(0.2026,0,0); // Moon is 0.0026 A.U. away from Earth v[0].SetXYZ(0,0,0); // Sun is still v[1].SetXYZ(0,Ve,0); // Earth moves towards Y direction v[2].SetXYZ(0,Ve*R,0); // Moon moves also towards Y direction while (tSetTitle("the Sun, Earth and Moon"); g2->GetXaxis()->SetTitle("X (A.U.)"); g2->GetXaxis()->CenterTitle(); g2->GetYaxis()->SetTitle("Y (A.U.)"); g2->GetYaxis()->CenterTitle(); g2->GetXaxis()->SetLimits(-2,0.5); // set real range of axis g2->GetXaxis()->SetRangeUser(-2,0.5); // set visible range of axis g2->GetYaxis()->SetLimits(-1.25,1.25); g2->GetYaxis()->SetRangeUser(-1.25,1.25); g2->SetMarkerStyle(20); // http://root.cern.ch/root/html/TAttMarker.html g2->SetMarkerSize(0.2); g2->SetMarkerColor(46); // http://root.cern.ch/root/html/TAttFill.html g2->Draw("ap"); g1->SetMarkerStyle(20); g1->SetMarkerSize(0.2); g1->SetMarkerColor(38); g1->Draw("p"); g0->SetMarkerStyle(29); g0->SetMarkerSize(1); g0->SetMarkerColor(2); g0->Draw("p"); TLegend* leg = new TLegend(0.6, 0.7, 0.85, 0.85); leg->AddEntry(g0,"Sun","p"); leg->AddEntry(g1,"Earth","p"); leg->AddEntry(g2,"Moon","p"); leg->Draw(); // http://root.cern.ch/root/html/TPostScript.html#TPostScript:description c1->Print("sem.pdf"); return 0; // C++ std }