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Jan. 26, 2021 | Tuesday
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Dr. Brown: Finding our way through the universe
Dr. William Brown.

In the fictional "Star Trek" series of the 1980s and 1990s, it was never clear how the Starship Enterprise found its way among the stars.

Most fans of the series were probably more impressed with the claim that the starship was capable of blasting along at several times the speed of light, a feat that physicists pointed out was impossible, given Einstein’s theory of general relativity.

The latter makes clear that the energy required and the mass of the ship and everyone in the ship would rise steeply to reach infinity values at lightspeed making travel at lightspeed or anything close to it impossible, never mind blasting along at multiples of light-speed.

That realization makes it clear that travel to the centre of the Milky Way or the far reaches of the universe is impossible within a human lifetime and thousands, if not millions of lifetimes, for destinations in the distant universe.

What about landing a spaceship on Mars? How do spacecraft find their way to Mars and land precisely on a predetermined small site on the planet’s surface?

To navigate with such precision, what’s needed are stationary beacons located throughout the universe from which the position and course of spacecraft can be determined. Those beacons exist: they are called quasars.

Quasars are massive black holes, millions or even billions of times the mass of our sun, which formed soon after the Big Bang. Together with dark matter, they helped to shape the early universe, including the formation of the earliest galaxies and stars.

Some of those stars were giants and burned through their stores of hydrogen quickly before finally exploding in giant supernovas and scattering their remnants throughout the neighbouring early universe.

Some of the latter remnants, together with other matter and particles within the gravitational reach of these giant black holes, formed fiercely hot coronas whirling about the black holes outside the event horizon and generated huge amounts of energy in the form of radiation.

Over the last several decades radio telescopes dispersed about the Earth’s surface identified and located thousands of those radio-beacons. More recently the focus shifted to the visible band of the electromagnetic spectrum as the chief source for identifying and mapping the locations of quasars for providing precise reference co-ordinates.

Quasars are ideal because they are found where they originated – at the farthest reaches of the universe – which, despite the enormous distances involved (many billions of light years away from Earth), their emissions are sufficiently bright to be detected and precisely located.

How precise? Within a hundred millionths of a degree and much better if the bearings from more quasars are taken into account. That’s very impressive – and it allows us to land a craft on Mars within a few centimetres.

Such precise information serves other purposes. You may not be aware of it, but the Earth wobbles and jerks sometimes in response to natural phenomena such as earthquakes and hurricanes. Both of those may throw off the accuracy of GPS signals and cause navigational errors by land and air unless corrective data from quasars is used to compensate for the Earth’s movements.

(And remember my essays on time – time passes slower at the surface of the Earth compared to higher altitudes, and at higher speeds relative to slower speeds, corrections for which must also be incorporated into GPS calculations for accurate readings. We take GPS for granted these days – accurate to within a few centimeters – when all the potential and realized errors are taken into account and signals from several satellites are used. Without those corrections, GPS is almost as fallible as any other form of navigation, and when the signals from satellites go down, as they sometimes do, the result, especially in remote areas where ground navigational aids may be few and far between, can be dangerous – think the Artic and Antarctica here.)

Let’s close this item on quasars with a little perspective. Remember that to see far out in the universe is to truly to see far back in time.

That is certainly true for quasars: the signals we pick up in our time, began their voyage to Earth many billions of years ago when the universe was young. What we see now therefore, happened a very long time ago. That realization was brought home to me by Michael Shermer, who recounted looking through his home telescope at Andromeda, the nearest galaxy to the Milky Way.

A moment’s thought brought him the realization that the photons of light arriving on his eyes began their voyage from Andromeda about the time when that famous bipedal ape named Lucy walked the Earth some 3.4 million years ago.

That’s a mind boggler and a great perspective with which to begin 2021.

Dr. William Brown is a professor of neurology at McMaster University and co-founder of the Infohealth series at the Niagara-on-the-Lake Public Library. Read more of his articles here.