On February 4, NASA did something rather strange. The space agency transmitted a Beatles song to the North Star, Polaris. Why did they feel compelled to do such a thing? Did NASA feel the need to make a statement about its love for the Fab Four? Were the Deep Space Network (DSN) operators such ardent Anglophiles they thought the cosmos needed more of a British twist to go with its microwave background radiation?
Actually, it was none of the above.
Feb. 4 was the 40th anniversary of when John, Paul, Ringo and George recorded "Across The Universe" and it was also NASA's 50th birthday. Obviously NASA had to transmit "Across The Universe" ...across the Universe. It seems only fair.
Space is Pretty Big
This sounds like a perfectly good reason to blast a classic tune across the void, but why am I bringing this up now? Feb. 4 was seven months ago, it's old news. But when we're talking about space, time, interplanetary, interstellar and intergalactic distances, 200 days is no time at all. Even 200 years is a flash of a meteor's ionization trail; 200,000 years is a fleeting moment when we are talking about stellar evolution, universal expansion and the vastness of space.
So this got me thinking. I wonder how far the Beatles signal has gone? I realize 218 days (or 1,880,000,000 seconds) is nothing in cosmic timescales, especially as Polaris is a target some 431 light years from Earth (i.e. it will take the Beatles tune 431 years to get there, as radio waves travel at the speed of light), but surely the signal must have reached a planet or two by now?
Actually, "Across The Universe" hasn't visited any planets in the Solar System, or even come remotely close to any other star yet.
When a Trillion Isn't a Big Number
How can this be? I hear you say, after all, the moon is only 1.255 light seconds away (it takes 1.255 seconds for light to travel from Earth to the moon); even (ex-planet) Pluto is a maximum of seven light hours away. But the DSN signal wasn't sent along the plane of the ecliptic (i.e. where the planets orbit around the sun), it was sent up, north of the ecliptic. Therefore, the signal never passed any of the planets in our Solar System.
Okay, so that was a bit of a technicality, but has the Beatles signal gone past anything yet?
Well, the song was transmitted 218 days ago. Traveling at the speed of light, the song has covered a distance of 0.59 light years or 3.5×1012 miles - that's 3.5 trillion or 3,500,000,000,000 miles.
That's a long way, huh?
Across Not Very Much
Actually, in cosmic distances, that's barely the end of the garden path in our own back yard.
The nearest star, Proxima Centauri is over 4 light years away. "Across The Universe" hasn't come across anything! It's only traveled 1/8 of the distance to our nearest star (but the signal doesn't even go in that direction anyway, so the Proxima Centaurians won't ever be dancing to Ringo's beat).
Nobody said communicating across the Universe was easy, let alone fast! We can forget about using this Beatles song as a means to get the attention of any alien civilization for at least 400 years (although Polaris isn't really an alien-hunting candidate anyway). No, this was just a symbolic message... to no one in particular.
However, within the next few months, the Oort Cloud (the hypothetical volume of space surrounding our Solar System, approximately 1 light year away) will soon be echoing with the Beatles... but there's nothing there to receive the radio signal anyway, just a few icy proto-comets. Oh well.