Special Relativity In Rock Music Http://www.scribd.com/doc/20245751/39

Special Relativity in Rock Music http://www.pdfcoke.com/doc/20245751/39 David S. Latchman September 30, 2009

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Introduction

The song “’39” by the rock band Queen, written and sung by Brian May on the album A Night at the Opera, is the 39th song in the band’s album chronology. There has been debate as to the significance of the song’s title and suggestions that it may relate to some period in history. While many things did happen in the year 1939, it is apparent from the lyrics, that the song speaks of loss and sacrifice of some sort; there are no apparent historical references. But to best understand the song’s true meaning, we must focus on the singer and writer, Brian May. Brian May, the lead guitarist of the band, Queen, is an astrophysicist and graduated from Imperial College London with degrees in Mathematics and Physics. He was already a graduate student when Queen became successful and eventually chose to abandon his graduate school career to pursue an extremely successful one in music; science’s loss was rock music’s gain. Thirty years after abandoning his academic career, Brian returned to Imperial College to complete his doctorate. So now that we know a little something about this guitar and music giant, we wonder what has Brian said about this song? Brian describes the song as follows in an interview “The Guitar Greats” by John Tobler and Stuart Grundy: “It’s a science fiction story. It’s the story about someone who goes away and leaves his family and. . . because of the time dilation effect, when you go away, the people on Earth have aged a lot more than he has when he comes home. He’s aged a year and they’ve aged 100 years. So, instead of coming back to his wife, he comes back to his daughter and he can see his wife in his daughter. . . a strange story. I think, also, I had in mind a story of Herman Hesse, which I think is called ‘The River’1 . A man leaves his hometown and has lots of travels and then comes back and observes his hometown from the other side of the river. He sees it in a different light, having been away and experienced all those different things. He sees it in a very illuminating way, ‘cause I felt a little bit like that about my home at the time as well, having been away and seen this vastly different world of rock music... totally different from the way I was brought up, and I had those feelings about home.” This pretty much kills the history theme debate. So we know now that “’39” is a science-fiction story that deals with the special relativistic effect of time dilation. Simply put, as objects approach the speed of light, time slows down, or is dilated, and this is the crux of the story. We can also treat the song as a Physics problem and ask ourselves, how fast were the Volunteers traveling?

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The Song

Brian has, more or less, told us how to solve the problem in the Tobler and Grundy interview but, as Physicists, we will look for clues in the song to solve this question ourselves. Plus, just plugging the 1 In the interview Brian says ‘The River’ but he is incorrect. The story that he is referring to is ‘The Poet’ and is found in the short story collection ‘Strange News From Another Star’ by the same author.

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values into an equation will be cheating and we won’t appreciate the poetry of the music. To start with, we look at the Time Dilation equation, which is ∆t0 = r

∆t

v2 1− 2 c

(1)

where ∆t0 is the time experience by people on Earth and ∆t is the time experienced by the moving travelers. v and c are the speed at which the Volunteers are traveling and the speed of light respectfully. So as v increases the traveler’s clock moves slower than a person’s clock on Earth. Before we go plugging numbers into eq. (1), we should listen to the song. If for some unfortunate reason you are unable to do so, the song’s lyrics are as follows 1 2 3 4

In the year of ’39 assembled here the Volunteers In the days when the lands were few Here the ship sailed out into the blue and sunny morn The sweetest sight ever seen.

5 6 7 8 9 10

And the night followed day And the story tellers say That the score brave souls inside For many a lonely day sailed across the milky seas Ne’er looked back, never feared, never cried.

11 12 13 14 15 16

Don’t you hear my call though you’re many years away Don’t you hear me calling you Write your letters in the sand For the day I take your hand In the land that our grandchildren knew.

17 18 19 20 21 22 23 24 25

In the year of ’39 came a ship in from the blue The Volunteers came home that day And they bring good news of a world so newly born Though their hearts so heavily weigh For the earth is old and grey, little darlin’ we’ll away But my love this cannot be For so many years have gone though I’m older but a year Your mother’s eyes from your eyes cry to me.

26 27 28 29 30 31

Don’t you hear my call though you’re many years away Don’t you hear me calling you Write your letters in the sand For the day I take your hand In the land that our grandchildren knew.

32 33 34 35

Don’t you hear my call though you’re many years away Don’t you hear me calling you All your letters in the sand cannot heal me like your hand

36 37 38 39

For my life Still ahead Pity Me. Now we can begin our analysis and solve this problem. Lines 1 and 18 read In the year of ’39 assembled here the Volunteers ... In the year of ’39 came a ship in from the blue 2

This tells us the duration of the Volunteers’ journey takes 100 years in Earth time. Thus ∆t0 = 100 years; just as Brian said. Line 24 goes, For so many years have gone though I’m older but a year This tells us that the protagonist of the song, has aged only a year. Thus ∆t = 1 year. Plugging these values into eq. (1), gives us 100 = r

1 v2 1− 2 c

(2)

and solving for v, we get v = 0.99995c.2 So these guys were moving pretty fast, 99.995 % the speed of light3 . As we can see, being able to travel at those speeds would allow us to be a space-faring species but as the song demonstrates, there are some personal risks and sacrifice involved. So now that we shown how our voyagers have been affected by their journey, we can analyze the poetry behind the song. The chorus goes Don’t you hear my call though you’re many years away Don’t you hear me calling you Write your letters in the sand For the day I take your hand In the land that our grandchildren knew. We now understand the pain that our traveler experiences. As his rocket travels away from Earth through space, though he can eventually return to Earth, his clock now ticks at a different rate to his loved one, due to the relativistic time dilation effect, and they become separated in time. He is a time traveler. Unfortunately for him, Special Relativity only allows time travel forward and not backward. So his loved one will always be separated from him. In the year of ’39 came a ship in from the blue The Volunteers came home that day And they bring good news of a world so newly born Though their hearts so heavily weigh For the earth is old and grey, little darlin’ we’ll away But my love this cannot be For so many years have gone though I’m older but a year Your mother’s eyes from your eyes cry to me. Now our travel has returned home and his mission is a success, having found the new planet for the people of Earth to colonize. He sees a world that has changed in many ways and is no longer the way he left it. His one consolation is that he can see his beloved in his daughter. For my life Still ahead Pity Me. This sums up the sad ending. Our adventurer is still a young man but his youth and life are still ahead of him. Unfortunately, the life he knew is one hundred years in the past and there is no way to go back to it.

speed of light is 299 792 458 m s−1 or 186282.397 miles per second. a comparison, the Large Hadron Collider accelerated protons to the speed of 99.999 999 1 % the speed of light.

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