TASP – twelve million miles a minute

Tuesday afternoon, time for a poem – or in this case a song – with some science in it. There are lots of figures in this one mainly speeds and distances; the title of this post is the speed of light, in not-so standard units.

You might want to check the numbers (nerd! …although I’ll admit I did this, too) and/or sing along loudly. Whatever you do, have fun.

Galaxy Song

Just remember that you’re standing on a planet that’s evolving
And revolving at nine hundred miles an hour,
That’s orbiting at nineteen miles a second, so it’s reckoned,
A sun that is the source of all our power.
The sun and you and me and all the stars that we can see
Are moving at a million miles a day
In an outer spiral arm, at forty thousand miles an hour,
Of the galaxy we call the ‘Milky Way’.

Our galaxy itself contains a hundred billion stars.
It’s a hundred thousand light years side to side.
It bulges in the middle, sixteen thousand light years thick,
But out by us, it’s just three thousand light years wide.
We’re thirty thousand light years from galactic central point.
We go ‘round every two hundred million years,
And our galaxy is only one of millions of billions
In this amazing and expanding universe.

The universe itself keeps on expanding and expanding
In all of the directions it can whizz
As fast as it can go, at the speed of light, you know,
Twelve million miles a minute, and that’s the fastest speed there is.
So remember, when you’re feeling very small and insecure,
How amazingly unlikely is your birth,
And pray that there’s intelligent life somewhere up in space,
‘Cause there’s bugger all down here on Earth.

Monty Python



  1. Who

    Hi florine, Monty Python is great and I like the poiem but some of your readers may know that it has a mistake. this is wrong:
    The universe itself keeps on expanding and expanding
    In all of the directions it can whizz
    As fast as it can go, at the speed of light, you know,
    Twelve million miles a minute, and that’s the fastest speed there is.

    the speed of recession from us, that parts of the universe have, is not limited by c.

    that is, the rate that distance to some galaxy is increasing can be several times c.

    recession speed—the rate the distance to something is increasing—is not the same thing as relative speed in the same frame, and recession speed is not governed by the same speed limit

    the saying that nothing can go faster than light is true, in the sense that nothing can CATCH UP and PASS a batch of light, but that is not the same as some galaxy getting farther from us by the expansion of the space in between and getting farther at a rate exceeding c.

    since you are a physics education specialist maybe you not only know about this but also have had to explain it to students. that could be a bit hard because it could be causing them confusion

  2. You’re right about the recession speed. Actually, it occurred to me when I was cycling home yesterday, that I could have said something about it.
    Twelve million miles a minute is really the speed of light, approximately, and it really is the fastest speed there is – but the expansion of the universe is not limited by it, because it is *space becoming bigger* rather than things flying away from us. But of course the idea of space becoming bigger is hard to grasp. It is sometimes explained with a rising (??) cake, or the surface of an expanding balloon.

  3. Who

    A woman named Siobhan Morgan who teaches astrophysics has a calculator
    where you put in the hubble 71
    and Omega_matter 0.27
    and Lambda 0.73

    and then it will tell you for any redshift z what the recession speed was when the matter emitted the light that is now reaching us.

    so it is rather amusing to put in z = 1100 which is the redshift of the Cosmic Microwave Background and have it tell you that when that CMB light was emitted, the matter that emitted it was moving away from us at 57 times the speed of light.

    the calculator also says that the matter that emitted the CMB light (now stretched to microwave) which we are now receiving is now between 45 and 46 billion lightyears away.
    So when we detect the CMB we are “seeing” something that is at this moment 45 Gly away from us.

    Ned Wright also has such a calculator
    which you can use to check the numbers of Siobhan Morgan
    but Wright’s does not give some things which Morgan’s does.

    I hope if you invent some science projects for highschool students that you teach some of them how to enjoy these cosmology calculators. I find them delightful.
    I like to know, when one observes a galaxy at z = 3, for example. How fast was that galaxy receding when it emitted the light. And how fast is it receding now. And how far away is it.

  4. Who

    this is Siobahn Morgan
    did you already know of her, or of her calculator

    perhaps not, since she is not so famous
    but many people know of Ned Wright

  5. Your comments were in the moderation queue, I guess because you provided more than one link…
    But thanks for those links. Wow, 57 times the speed of light… amazing. (Not that I can imagine it, really… that’s always a problem with these astronomic numbers, of course.)

  6. max

    ok, you guys need to do something else than sit at some random site and argue about how fast the speed of light is and what is the fastest speed is… i mean really… come on

  7. Really? Why?

    (And this is not some random site to me, you know…. it’s my blog!)

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