Show I r Do You Know it 1 ASTRONOMERS A A announce that an explosion I- I probably the gre greatest test in our history took place February 27 out among the stars Beta star brilliancy brilliancy bril bril- a of the second magnitude or suddenly flamed up and became one of the brightest stars stars technically known as first magnitude What the astronomers really mean nean is that the explosion took place eighty years ago and that it became visible to us February 27 Beta Is s so o far away from our earth that it I takes light traveling miles a second eighty years to reach us In other other words when we look at this star we see it as it existed in 1843 What is it like now No way of knowing knowing knowing know know- ing until eighty years hence in n the year 2003 A man ten feet from you looks up and sees you at a certain instant Farther away i feet behind him another man looks up at identically identically iden iden- the same time But the second man sees you a fraction of a second later than does the first man since it takes the light waves a fraction fraction fraction frac frac- I tion of Df a second longer to reach him The rhe fraction fraction frac frac- II tion is infinitesimally small of course It in increases increases jn- jn creases with distance Youve You've noticed a similar phenon phenomenon enon if you ever looked out at sea and saw smoke come from a cannon before you heard the report of the the explosion The explanation here is that light waves travel faster than sound wa waves ves When you look up ip into the sky at night t you see the stars not as they are today but as they were at various times in the past The t time me depends depends de- de de 1 on their distance Suppose there were people peo peD- peo 1 pIe living in Beta There c couldn't b be as we I understand things because of the intense heat up there But just suppose And suppose also that an astronomer on Beta has ha's a telescope powerful enough to enlarge our earth sufficiently to see what's going on here Since it takes takes' eighty I years for light waves to travel bet between een our earth I I and Beta that astronomer is seeing what happened on earth eighty y years ars ago It would I be the year 2003 before he could see what is happening happening hap hap- pening here today Apply the same idea to more distant stars and people on them would be peering peering peering peer peer- ing through their telescopes today watching matching the battle of pf Waterloo the building of the pyramids funeral of King Tut and Tut-and and so so on according to distance This is what Einstein has in mind when he says that time is relative not fixed and absolute If you ponder the idea it will impress you that in the universe there is not r really all any presen present t pa past t or future All is an eternal l now Time is a delusion of our senses A ligh wave light wa t-wa image of everything we do tra travels travels' velson vels' vels on forever into space |