This week there is a very special treat here at the Book of Lost Nights, in that popular science writer and New Scientist cosmologist Marcus Chown, author of We Need To Talk About Kelvin (which I reviewed in these pages last Friday) has very kindly agreed to do a guest spot on the blog!
There was some discussion over what would constitute an interesting new angle for this, and in the end we decided that it might be kinda cool to allow SF (and other writers) to submit their own scenarios for their works in progress and ask Marcus what the thought the ramifications would be.
The shoutout for questions went to the T Party, my own writer’s group, my LJ friends, Twitter, Absolute Write, Litopia, and Futurismic, and Marcus very obligingly furrowed his brow over a set of very challenging and interesting conumdrums. At some point he even broke out some mathematical formulae, as you’ll see below, which to me is roughly analoguous to him conjuring demons and having them do a cover of “Bohemian Rhapsody”. The results, as I’m sure you’ll agree, were fascinating and thought-provoking:
The first question was from me:
1) If the Moon were to have a wobble in its orbit, say from an asteroid strike or some other catastrophic effect, what would the effect be upon the Earth, in terms of tide and weather? Would there be tsunamis, earthquakes? What if we woke up one morning and the Moon was just gone?
Marcus says: A biggish asteroid would be, say, about 300 kilometres across, which means it would have about 1/1000 the mass of the Moon. A bag of sugar is about 1/000th the mass of a car. Think of how much effect it would have on a car if you threw a bag of sugar at. Not much. So, although the impact of a big asteroid would have a big effect on the Moon’s surface, it wouldn’t effect the Moon’s orbit a lot. In the past – during the Late Heavy Bombardment 3.8 billion years ago – the Moon was hit by bodies this size. They punctured the Moon’s crust and the upwelling of lava from the lunar interior created the lunar seas (Mare basins) we see on its face today.
But such an impact might make the Moon’s orbit a little more elliptical, so it would swing in a little closer on its closest approach to the Earth. Since the height of tides on Earth depends on the inverse-cube of the Moon’s distance, if the Moon swung even a little bit closer it would make the tides noticeably bigger. But it would have no effect on tsunamis because, contrary to what many people think, they are not tidal waves, and have nothing to do with tides. And it would have no effect on the weather.
If the Moon disappeared overnight, the lunar tides would gradually stop (the Sun accounts for about 1/3 of the tides). In the long-term, however, the effect on the Earth would be very significant. A vast amount of habitat would be lost on the shorelines of the oceans and all creatures that are adapted to feeding on the mud exposed twice a day as the sea recedes would have hard time and maybe become extinct. But the biggest effect would be on our climate. The Earth spins on its axis like a top. And, like a top, it wobbles. If it wobbles too much from its axis, the Moon’s gravity pulls it back. Why is this important? Well, big wobbles would be accompanied by huge changes in climate. We see this on Mars, which has no big Moon. Water once ran on its surface but now it is in the deep-freeze. This kind of thing would happen on Earth without the Moon. In fact, we can thank the Moon for the benign climate the Earth has had for billions of years and, without which, we wouldn’t be here.
The next one is from Pelotard:
2) I have it on good authority (NS, and I actually wrote to the scientist in question and asked) that Mercury might be flung out of the solar system in about 10 billion years. Now… if another planet had been flung out of the solar system sort of recently (astronomically speaking), would there be any obvious signs of this today?
Marcus Says: Hi, Pelotard. Yes, although the planets appear to orbit the Sun as regularly as clockwork, physicists have discovered that the Solar System can sometimes go haywire as if someone has thrown a spanner in the works. This is the effect of something called “chaos”. If a planet was ejected during a chaotic episode, it might perturb the orbit of another planet if it passed close by on its way into interstellar space. But, after that, there would be little evidence that it had ever existed.
Interestingly, simulations of the formation of the planets 4.55 billion years ago often show about 10 Earth-mass bodies forming. The majority are catapulted from the Solar System early on by close encounters with forming giant planets. So, it could be that, in addition to the two Earth-mass planets in our Solar System – Earth and Venus – there are another 8 at this moment drifting through the darkness between the stars, having been kicked out of the embryonic Solar System.
Next up is Dave Gullen from the T Party!
3) Hi Helen and Marcus,
Thanks for doing this. As a regular reader of New Scientist I always enjoy Marcus’s articles. My question are about anti-matter:
- how much would you need to make a bomb with a yield of say 100 terrajoules?
- any idea what would happen if you set it off inside a hurricane?
Thanks again.
Dave Gullen
Marcus says: Hi, Dave. The annihilation of matter and antimatter converts 100% of their mass-energy into other forms of energy, ultimately heat (by comparison, a hydrogen bomb – or the Sun – converts less than 1%). The formula which gives the amount of energy, E, that can be liberated by a mass, m, is the most famous in science: E = mc^2, where c is the speed of light (300,000 kilometres per second).
100 terajoules = 10^14 joules
The amount of matter/antimatter required to liberate this is – using Einstein’s formula – therefore 10^14/ (3 X10^8)^2 = roughly 10^-3 kg, or just 1 gram!
The energy of a typical hurricane, I believe, is about 10^18 joules. So a 1g antimatter bomb exploded inside a hurricane would liberate only about 0.1 per cent as much energy as the hurricane itself. So it might not have a lot of effect. A better way to stop a hurricane would be to cool the seawater over which it is travelling since it is heat from the sea that drives a hurricane. How you would do that, though, is anyone’s guess!
Anonymous asks:
4) A popular trope for near-future SF is interplanetary space travel involving flight times stretching into years. How much of a hazard to travellers is exposure to cosmic rays and radiation from solar wind really?
Within the Solar System, cosmic rays from the Sun – mostly high-speed protons (hydrogen nuclei) are a real hazard for long journeys – for instance, the proposed 6-month journey to Mars. Although a modest amount of shielding might be enough to safeguard the astronauts, a big flare on the Sun that ejected material in their direction, could give them a fatal radiation exposure.
A bigger problem is for interstellar travel since, to get anywhere in a reasonable time, requires flying at close to the speed of light. That means the protons (hydrogen nuclei) of interstellar space hit the spacecraft at almost the speed of light, like a deadly sleet. A lot of shielding would be needed to keep humans safe, which would add to the weight of a spacecraft, meaning it would need more fuel, adding to the weight, and requiring more fuel… A way around this might be to build a black hole star ship! (see my article in “New Scientist” the week before last… http://tinyurl.com/y9axw62)
This is from Bob (MagicMan) at Litopia:
5) In my story, I have my main character create a new battery that recharges constantly by tapping into the earth’s magnetic field. First, will this pass the scientific test of plausibility? Second, would mass production of this battery drain the magnetosphere and what might be the negative effect…would the earth’s core stop spinning, would the electromatic shield that syncs with the solar wind vanish, would the massive energy reserves in the magneto tail dissipate?
Secondary question.
Faster than light speed (FLS) is not possible relative to a fixed point. FLS is possible when relativity is removed. Space appears to be a void but in reality it contains enough debris to create friction and limit the maximum FLS attainable. My premise in my novel is this threshold FLS can be increased by using a magnetic shield to repell the material that produces the friction thereby allowing a significantly increased threshold speed. Is this plausible?
Smiles
Bob
Marcus says: Hi, Bob.
1) Yes, you could certainly use the Earth’s magnetic field to generate power. Recall that whenever a conductor cuts through a magnetic field an electrical current is made to flow in the conductor. This is the principle behind the electrical generators that create our domestic electricity. NASA has experimented several times – though I am not sure with success yet – with a space tether. This is a long thin wire, lowered from the Space Shuttle towards the Earth. The idea is that, as the tether cuts through the Earth’s magnetic field, a current is created in the tether. In other words, power is generated.
You would have to drain a lot of energy from the Earth’s magnetic field to affect it! The Earth’s magnetic field is generated by electrical currents circulating in the Earth’s core, which are ultimately caused by the rotation of the core. No one knows the details. However, core has an enormous amount of rotational energy. Although it is possible that draining energy from the Earth’s magnetic field would have a “back reaction” on the core, the effect is likely to be negligible and the core is unlikely to be slowed significantly. Of course, I could be wrong!
2) The mechanism you suggest for faster-than-light travel is, unfortunately, not plausible. It isn’t the presence of “debris” in space that causes there to be a cosmic speed limit – the speed of light. It is a fundamental property of our Universe. However, according to Einstein, it is only the speed of light that cannot be attained. There remains the possibility of “tachyons”, which never have to attain the speed of light because they are born moving faster than light.
And from Dawn at Litopia:
6) Green lightning… what would the earth’s atmosphere have to change to produce green lightning?
Hi, Dawn. This a hard one! As electricity discharges between a cloud and the Earth, the air along the path is heated to about 30,000 degrees – far hotter than the surface temperature of the Sun. The super-fast expansion of that air creates the sound of thunder.
I think – and I could be wrong! – that at a temperature of 30,000 degrees, a lot is going on. An atom of, say, oxygen or nitrogen, has a number of electrons and each occupies a particular energy level. If an electron drops from one particular energy level to another it gives out light of a particular colour. Within an atom – particularly an atom which has been given a huge boost of energy by being heated by lightning – electrons will have been boosted to a large number of high-energy states (and some will have been ejected all together). As all these electrons drop in energy, light of a whole range of colours will be emitted. Mixed together this will make white light. Just as all the colours of the rainbow mixed together make the white light of the sun.
So I think it wouldn’t matter a lot what the atmosphere was made of. Lightning would be white.
This is from Melanie at the T Party:
7) What’s your favourite use of science in a movie? And what’s your least favourite and most unlikely application of science in a movie or book?
Marcus says: Hi, Melanie! Best – That stewardess walking upside down with Velcro slippers in 2001: A Space Odyssey. Worst – Superman turning back time to bring Lois Lane back to life by spinning the Earth backwards in Superman.
And finally, from Denni Schnapp at the T Party:
It gets cold at night in the Australian desert – an argument much favoured by climate change skeptics – but I wonder how cold it would really get there if the Earth had no atmosphere at all, and ditto how hot it would be during the day, say at noon in Wagga Wagga
Thank your very much for taking the time to answer our questions!
Denni
Marcus Says: Hi, Denni. Without the Earth’s atmosphere the Earth would indeed be frozen solid. By far the most important greenhouse gas in the atmosphere is water vapour. Together with carbon dioxide, this traps enough heat in the atmosphere to give the surface an average temperature of about 14 degrees Celsius. Without this cosy atmospheric blanket, the average temperature would be about –18 degrees Celsius and the Earth would be uninhabitable, a global arctic waste. Although it gets a lot of bad Press, we owe everything to the greenhouse effect! Unfortunately, the small additional effect humans are having by burning fossil fuels seems to be having a critical effect on the planet.
And that’s it – I’d just like to thank Marcus ever so much for agreeing to do this, and also to everyone that sent in such great questions. The next stop on Marcus’ Blog Tour is Teen Librarian on the 15th, so be sure to catch him there! And I really do recommend the book – most wonderfully thought-provoking!
This went so well, that I’m considering doing a guest blog for other fields of endeavour – such as answers to medical or historical questions, for instance. Shout out if you think it would be useful.
Next week normal service resumes, including a discourse on the bittersweet pleasures of redundancy, my unrequited love for Charlie Brooker, and mean-spirited movies, most notably “Law Abiding Citizen”…
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