Galaxies and the )t$PTNJD$BMFOEBS

Cosmic Line Events Worksheet © copyright 2010 Astronomical Society of the Pacifc

Note: Te symbol ~ in front of a number means “roughly” or “about”

Number of Number of Date/Time on Event Days Ago on Ago Calendar

The 13.7 billion 365 Jan. 1, 12 am

13.7 billion The formation of frst neutral atoms (400,000 years 365 Jan. 1, 12:15 am after the BB)

Formation of frst stars & galaxies ~13 billion

Formation of the thin disk of the Galaxy ~9 billion

Formation of the Solar System 4.56 billion

Formation of the Moon ~4.5 billion

Birth of on Earth ~3.8 billion

First cells develop on Earth ~2 billion

First vertebrates (creatures with backbones) ~520 million

First 230 million

First ~200 million

Death of the dinosaurs from giant impact 65 million First bipedal hominids (human-like creatures walk- ~4 million ing on two legs) First humans ( sapiens) 200,000

Development of agriculture (farming) ~10,000

Development of the for transportation ~6500

Invention of the telescope 400

Right now 0 0 Dec. 31, midnight

5IF6OJWFSTFBU:PVS'JOHFSUJQTt"TUSPOPNJDBM4PDJFUZPGUIF1BDJöD Page 6 Galaxies and the Universe )t$PTNJD$BMFOEBS

Cosmic Time Line Events Calculations © copyright 2010 Astronomical Society of the Pacifc

In this exercise, we want to set the equal to one calendar . Ten we want to set up ratios to fgure out where in that calendar year signifcant events in the of the universe would fall. (In this analogy, UIF#JH#BOHIBQQFOTJOUIFĕSTUNPNFOUPG+BOBOE/08JTUIFWFSZMBTUNPNFOUPG%FD

4PPVSCBTJDJEFBJTUIBUCJMMJPOZFBSTFRVBMPOFDBMFOEBSZFBS EBZT 8FMMJHOPSFMFBQZFBSTGPSUIJTFYFSDJTF

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Number of years ago an event happened = x days Number of years ago Big Bang happened 365 days

Te number of years ago the Big Bang happened is 13.7 billion years = 13,700 million years.

8IFOZPVWFTPMWFEGPSY UIFOVNCFSPGEBZTBHP GSPN%FD UIBUBOFWFOUTIPVMECFQMBDFEPOPVSDBMFOEBS  you then have to count the days backwards. To make that easier, we have provided a table that tells you on what date any number of days counted backwards from Dec. 31 would fall. (You’re welcome.)

So, for example, the dinosaurs developed 230 million years ago. Setting up our equation,

230 million years = x days 13,700 million years 365 days x = 6.13 days (which we round of to 6 days ago)

-PPLJOHBUUIFUBCMFPGEBUFTDPVOUFECBDLXBSET EBZTCFGPSFUIFFOEPG%FDQVUTUIFTUBSUPGUIFEJOPTBVSTPO Dec. 26.

6TFUIFUBCMFi$PTNJD5JNF-JOF&WFOUT8PSLTIFFUwXIJDIMJTUTTPNFPGUIFLFZFWFOUTJOUIFIJTUPSZPGUIFVOJ- verse and do the same kind of calculation for each event. At frst, you can round of, but as you get to events closer to the end, fractions matter.

So we want to fgure out how many years of real time would make an hour on our cosmic calendar. If 13.7 billion years = 1 calendar year, then one day on our calendar would be:

13,700 million yrs in a calendar year = 37.5 million years/calendar day 365 days in a calendar year

In the same way, divide by 24 hours in a day to fgure out the number of years in a calendar hour and divide by 60 again to get the number of years in a calendar minute.

5IF6OJWFSTFBU:PVS'JOHFSUJQTt"TUSPOPNJDBM4PDJFUZPGUIF1BDJöD Page 8 Galaxies and the Universe )t$PTNJD$BMFOEBS *Does not leap*Does take years into account. DEC NOV OCT SEP AUG JUL JUN MAY APR MAR FEB JAN 122 153 184 214 245 275 306 334 365 31 61 92 1 121 152 183 213 244 274 305 333 364 30 60 91 2 120 151 182 212 243 273 304 332 363 29 59 90 3 119 150 181 211 242 272 303 331 362 28 58 89 4 118 149 180 210 241 271 302 330 361 27 57 88 5 117 148 179 209 240 270 301 329 360 26 56 87 6 116 147 178 208 239 269 300 328 359 25 55 86 7 115 146 177 207 238 268 299 327 358 24 54 85 8 114 145 176 206 237 267 298 326 357 23 53 84 9 113 144 175 205 236 266 297 325 356 22 52 83 10 Number of daysNumber before Decemb 112 143 174 204 235 265 296 324 355 21 51 82 11 111 142 173 203 234 264 295 323 354 20 50 81 12 Days of the Year* 110 141 172 202 233 263 294 322 353 19 49 80 13 109 140 171 201 232 262 293 321 352 18 48 79 14 108 139 170 200 231 261 292 320 351 17 47 78 15 107 138 169 199 230 260 291 319 350 16 46 77 16 106 137 168 198 229 259 290 318 349 15 45 76 17 105 136 167 197 228 258 289 317 348 14 44 75 18 er 31st 104 135 166 196 227 257 288 316 347 13 43 74 19 103 134 165 195 226 256 287 315 346 12 42 73 20 102 133 164 194 225 255 286 314 345 11 41 72 21 101 132 163 193 224 254 285 313 344 10 40 71 22 100 131 162 192 223 253 284 312 343 39 70 23 9 130 161 191 222 252 283 311 342 38 69 99 24 8 129 160 190 221 251 282 310 341 37 68 98 25 7 128 159 189 220 250 281 309 340 36 67 97 26 6 127 158 188 219 249 280 308 339 35 66 96 27 5 126 157 187 218 248 279 307 338 34 65 95 28 4 125 156 186 217 247 278 337 33 64 94 29 3 124 155 185 216 246 277 336 32 63 93 30 2 123 154 215 276 335 62 31 1

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