Lunacy
First up was Terra Nova, a show where colonists from a over-polluted future travel back in time 85 million years to where the air is fresh and dinosaurs roam the Earth. One of the important characters is a geeky girl whose main function so far has been to explain backstory in a sciencey and geeky way. Fine.
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| The moon looked bigger 85 million years ago because it was closer to the Earth. True story. (Screen capture from pilot of Terra Nova.) |
That was when I died a little bit inside. The expansion of the universe is a large scale effect. Over cosmologically small distances gravity dominates. Like a lot. I touched on this in one of my galaxy posts when I said that the Milky Way and Andromeda will eventually merge. Basically, yes the universe is expanding, but it's only really far away things that are moving away from us. Even the nearby galaxies are being pulled gravitationally closer to us. Galaxies are made up of stars. Stars have planets around them and planets have moons. Our moon is much to close to the Earth for the expansion of the universe to pull it away.
So what is really causing the moon to drift away? Tidal forces, something else I've mentioned in the past. The moon causes tides on Earth by pulling water in the oceans towards it slightly, making it bulge out (and a bulge also forms on the opposite side to balance it). However, the Earth is rotating faster than the moon is orbiting it, so the bulge gets dragged along with the ground as it spins and in turn exerts a slightly different gravitational pull on the moon, pulling it forwards along its orbit. This causes an angular momentum exchange between Earth and moon--the Earth's rotation is slowing down and the moon's orbit is becoming wider (it's actually moving more slowly though...). Fun fact, that means tides would have been a bit higher back in the day, too.
There you have it. 85 million years ago, the moon was closer to the Earth because it hadn't had as much time to steal angular momentum from the Earth and hence widen its orbit. It has nothing to do with with the expansion of the universe.
Speaking of the expanding universe...
In the beginning there was the big bang. We don't know what caused it and for the purposes of my next rant, it doesn't really matter. At one point, everything was in the same place. Then it exploded.
I am going to digress slightly and talk about everyday explosions. (Well, hopefully things don't explode in your everyday life, but you know what I mean.) When something explodes, for simplicity let's say a bomb, then a sudden burst of energy--be it chemical or nuclear--pushes the material of the bomb (the outer casing or what have you) away from the centre. Depending on location and conditions, this material will fly through the air or water or whatever. In this sense, the big bang wasn't an explosion.
Matter, the stuff the universe is made of, did not explode out from a single location. It did not explode into anything because the universe is everything. There is nothing physically accessible outside it (M-brane theory notwithstanding). A common metaphor is this: imagine an un-inflated balloon with a bunch of galaxy clusters stuck onto its surface. The balloon part of the balloon is the universe. When you inflate it, the universe-balloon stretches and the galaxy clusters all move further away from each other. It's the space between the clusters that's expanding. You could make the balloon very small in its un-inflated form to get everything coming from one point. Then, at that point, everything was in the same place; all the space was together at the origin. Then it expanded. There is no single point that was once the origin, all the points were at the origin.
Imagine my frustration, then, when a genius scientist in the pilot episode of Eureka is looking for the origin point of the universe. It made me very angry. The fact that the MacGuffin of the plot hinged on his research was also a bit annoying. That he was trying to use an optical telescope to look for the beginning of the universe is just hilariously ridiculous (he would need to use very long wavelength radio waves, not visible light to do that--but I'll write a proper blog post about telescopes some time soon). It also really, really didn't help that the genius in question was a massively arrogant prick, but would it have killed the writers to make him a scientifically accurate prick? That would have mitigated my annoyance somewhat (not that much because the show is more sexist than it should be, but that's not a rant for this blog).
The moral of the story
If you don't take the time to get someone to check your facts (or if you do--and I know many Hollywood studios do--and then ignore the expert), you will piss geeks off. If you are making science fiction and geeks are a chuck of your target audience, why would you want to annoy them?
(And if you're wondering, I did actually like Terra Nova, it was just one line that irritated me. Eureka on the other hand, continued to annoy me with episode 2, even if irritating scientist prick wasn't in it.)
End rant.
PS You can read a bit more about the Terra Nova part of this (with more science and slightly less rant) in this post.
The expanding universe was nothing to do with reason behind the moons distance to earth. She says the stars look different, then says because the universe is expanding. Not being a correcting geek, just saying.
ReplyDeleteYes, she says the stars are different because of the expansion of the universe. That said, the moon couldn't be moving two centimeters away from the earth every year for eighty five million years because by now it would be too far away.
ReplyDeleteDid it move more slowly away from the Earth a long time ago? Would the stars really have been that different back then?
How does a family that can't even remember what the moon looks like be able to remember the constellations?
Anon 1 is right, she says the stars are different because of the expansion of the universe (she doesn't blame the moon on the expansion, my mistake). She is still wrong because the stars we see in the sky are all part of the Milky Way and hence too close to be expanding away from us (because they are gravitationally bound). They WOULD look different 85 million years ago, however, because all these stars, including our sun, are orbiting the centre of the galaxy. Over 85 million years they would have all orbited part way around and be in different positions.
ReplyDeleteGood point about them remembering the constellations, though. Perhaps geeky girl studied them in class? (The parents don't mention it, just that the moon looks different and that they were young last time they saw it.)
Anon 2: The moon IS moving away from us. 2 cm a year over 85 million years is an approximate amount, I admit; bouncing lasers off the moon now shows that it is moving away 3.8 cm per year, and on Terra Nova she said half a centimetre. The rate would not have been constant and there are estimates from palaeontological data that the average rate over that period was around 2 cm per year.
A recession of 2 cm a year over 85 million years gives us a moon less than 2000 km closer back then. Given that the moon varies more than that as it moves through closer (perigee) and further away (apogee) parts of its orbit now, the real question is would the moon really be that noticeably bigger?
I expanded a bit on my above comment in a new post. You can read it here: http://tsanad.blogspot.com/2011/10/more-on-terra-nova.html
ReplyDelete