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Radio transmissions are (IMHO) one of mankind's greatest achievements.
The ability to communicate information around the world and across the deep voids of space using subtle fluctuations in the ether is a truly astounding invention which changed our world forever.
These days, radio transmissions are an intrinsic part of our lives. Our smartphones, keyless entry on the car, PayWave at the checkout, TV broadcasts, entertainment, Bluetooth, GPS and even the way we recharge some of our devices are all things that rely on radio wave transmissions that we seldom even think about.
For most purposes, radio does a fantastic job.
It's fast (we're talking the speed of light) and it uses very little electrical power to span useful distances. It's comparatively safe (at low power levels) and non-polluting.
But in some applications, we're starting to reach some practical limits and we may find that alternatives are required.
What am I talking about?
Well how about our exploration of the universe?
The very impressive New Horizons mission is a good example of this.
Launched way back in 2006, this craft has been flying around the solar system, collecting valuable data and images on Jupiter, Pluto and beyond.
Its latest encounter was with Ultima Thule, an object in the Kuiper Belt which is so small and remote that back when the craft launched, we didn't even know of its existence. However, by some very clever science and navigation, the New Horizons probe managed to pass within a few thousand Km of this binary chunk of rock and has already sent back some images.
As if calculating the angles, velocities and timings for ensuring that the mission passed within spitting distance of Ultima Thule wasn't hard enough, we have to remember that this craft is now more than six light-hours away from Earth. That's a full half day for data to be sent and confirmation to be received back.
This latency means scientists effectively have to work six ours in the future when sending commands to the probe because one of the limitations of radio is that it only travels at the speed of light. While that's not a big problem for communicating around the Earth, it's an increasingly annoying hurdle as we reach further out into space.
Unfortunately, if Einstein's theories are correct, this is not a limitation that we are going to overcome any time in the near future.
However, there is another problem with radio and that is its limited range.
Things like the inverse square law and the sheer tyranny of distance mean that as we try to span greater and greater distances, the reliability and capability of our radio broadcasts becomes a growing problem.
To date, we've dealt with the problems of communicating these vast interplanetary (and beyond) distances by building huge antenna arrays to gather as much of the very weak signal as possible. Transmitting signals from Earth isn't too much of a problem because we have plenty of power and we can just crank up the noise. However, a tiny space craft billions of Km from home only has a very limited amount of power available to it so other solutions need to be found.
Right now we rely pretty much on those huge antennas here on Earth and an ability to reduce the rate at which the data is sent from these distant probes. There is a fortunate link between data-rate (bandwidth) and the sensitivity of radio receivers. Reduce the bandwidth and you can hear weaker signals more clearly. The down-side of course, is that it takes much longer to send a given amount of data.
Ultima Thule is now so far away that it's having to use very low bandwidth transmissions just to be heard back on Earth. This means that although it has taken numerous hi-resolution images of Ultima Thule, it will be some time before we get to see them.
Think of it as having to download a 4K movie using a dial-up modem. Yeah, it's almost that bad!
So the ability for us to explore beyond our own solar system may be limited not so much by the longevity of our space probes or our ability to hurl them at great speed into the vast unknown void of the universe - but our ability to hear them and download their valuable data at any kind of acceptable speed.
So what's the solution?
How can we circumvent these unfortunate limitations of radio waves?
Subspace radio? (LOL)
Something as yet undiscovered?
As explorers of the universe, we are indeed rank amateurs and our technology is very primitive... although I'm still gobsmacked at how well we do with what we have.
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