Intergalactic Doppler effect joke, on a car, for nerds

It’s good to use the title of a blog post to make your target audience clear.  And by doing so, I have clearly limited the potential audience of this particular post to about a fraction of one per-cent of my total potential readers.  Which probably means no-one will ever read this and find it funny.

But anyway, here is what has had me chuckling into my beard on and off for the last few days:

Of course, those of you with a scientific brain will already get the joke and why it doesn’t work.  Those of you who don’t get it, well, you know how the siren on an ambulance sounds different after it’s driven past you?  That’s when the source of your sound waves is moving, it goofs up the shape of the waves and so by the time they get to you they seem different.

Light does exactly the same thing – it will change colour slightly if it’s coming towards you or going away from you.  But the joke breaks down when you realise you need to be going quite a way above the speed limit, say around 671,000,000 mph or so, to make it work.

In case you’re wondering why this is important, it’s sort of how we know the Big Bang happened.  But that, as they say, is for another day.

This physics-related gag was found here:

http://readmybumpersticker.com/wp-content/uploads/2010/02/redshifthumor1.jpg

And more info on red shift and the Doppler effect can be found, well, on Google, you lazy so-and-so.  But you’re learning it for GCSE, try this place first:

http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/radiation/originsrev2.shtml

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