Cosmos: A Sky Full of Ghosts

“What actually transpires beneath the veil of an event horizon? Decent people shouldn't think too much about that.”

-- Academician Prokhor Zakharov, "For I Have Tasted The Fruit"

As I begin writing this, I think it will perhaps be a shorter review this week, as it is taking time away from my playing of the new computer game Civilization: Beyond Earth. Supposedly Cosmos: A Spacetime Odyssey was an influence on this game, but another obvious influence is the previous Civilization-in-space Alpha Centauri. And this episode of Cosmos reminded me of Alpha Centauri, as we shall see...

The narrative line of A Sky Full of Ghosts concerns William Herschel and his son John. William is credited with the idea that looking into space is looking back in time, because of the speed of light and the distances involved.

Tyson gives examples of how far things are from the Earth as measured in light minutes/hours/years, from the moon (at 1 light second away) to the first galaxies and the big bang, as far away and as far back as we can observe the light. Considering this light is billions of years old, Tyson takes a swipe at Creationists who take the Bible literally, saying that if the universe was only 6,000 years old, then only the light from within 6,000 light years would have had the time to reach us.

As the previous episode dealt with light, so this deals with gravity, taking us (briefly) through the discoveries of Newton, Faraday, James Clerk Maxwell, and finally Einstein, with a bit more time spent on the latter's thought experiment about travelling at the speed of light that gave rise to his Theory of Relativity.

A less well-known scientist who gets discussed is John Michell, who predicted the existence of Black Holes, or "Dark Stars" as he called them - you can't see them because they (by definition) give off no light, but we can now detect their gravitational effect on nearby stars.

Staying with the subject of gravity, there is a very vivid scene where Tyson visits a New York street and 'turns off' the gravity to see what happens, and then turns the gravity up to many multiples of Earth's normal gravity. As with the soundwaves scene last time, this is a visually impressive  and imaginative set-piece.

Back on Black Holes for the remainder of the episode, Tyson takes us through how giant stars become Black Holes at the end of their natural lives, and how scientists discovered the first actual Black Hole, Cygnus X-1, using X-rays and the effects it had on a nearby star. This led on to detecting giant Black Holes at the centres of galaxies, including the Milky Way.

Finally Tyson takes his Ship of the Imagination into a Black Hole, speculating about what lies beyond the Event Horizon - a tunnel to somewhere else in the universe, or maybe even another universe, raising the possibility of universes within universes, and these with their own Black Holes, layered infinitely.

This bit cannot help but remind me of the Singularity Inductor project from the Alpha Centauri game, with the quote I gave at the beginning of the review ironically tying in here - what Zakharov warns against is precisely what Tyson is doing.