Dark Matter Jumps the Shark

Mainstream theoretical physics needs to take a long hard look at itself. I've just read an article about Lisa Randall's new suggestion that dark matter killed the dinosaurs and after collapsing in a tangled heap of laughter I realised that this perfectly captures the attitude of mainstream theoretical physics: the extrapolation of untested and possibly untestable hypotheses into a regime where you are unlikely ever to be proven wrong, like the interior of black holes, the first millisecond after the big bang or the age of the dinosaurs. It is the physics of the unimaginative and cowardly.

Dark matter is like a universal plaster for any anomaly. For galaxies stick the invisible stuff freely onto your equations in a halo. For the flyby anomalies put it in a thin disc, for the dinosaurs it is a layer (I refuse to look at the details, like I refuse to read up on ghostology). There's a useful idea called Russell's teapot (pointed out to me by DaKangaroo on twitter). Bertrand Russell said that if someone claims there's a teapot orbiting the sun between Mars and Jupiter the onus is on them to prove it, certainly before expecting people to believe anything else deduced from it (By the way, I'm not saying dark matter can't exist at all in some minor form, just not as it is taken by the mainstream as a panacea for all their problems).

In contrast to dark matter's arbitrary flexibility, MiHsC is unadjustable. This means that, unlike the dark side, I can't cheat. MiHsC only predicts one possibility, and yet that possibility correctly models the observed anomalies I've tried it on: galaxy rotation, cosmic acceleration, the orbit of Proxima Centauri, the spin of extreme dwarf galaxy Triangulum II, the Pioneer and flyby anomaly, the Tajmar experiments and the emdrive. Meanwhile the mainstream is messing around with the insides of black holes, the early universe and the dinosaurs, confident no-one can disprove them.

But there is hope. In the fifth season of the TV series Happy Days ratings were falling so that the writers wrote in a scene where Fonzie jumped over a shark on skis. Ever since then a useful phrase has entered the English language: to 'Jump the Shark' meaning to use shock tactics to retain dying interest. There's now a similar term 'Nuke the Fridge' based on Indiana Jones 4. With Randall's dinosaur demise the dark matter bandwagon has just jumped the shark, so things may now get interesting.

Evidence for MiHsC: Triangulum II

The usual balance in systems such as galaxies is between gravity which holds them in (keeps them bound) and the inertial centrifugal force that tries to explode them. In all the systems we see today these two forces must be balanced, or we wouldn't still see them. Writing this balance mathematically gives

G*M*mg/r^2 = mi*v^2/r

where G is the gravitational constant, M is the galaxy's mass within a radius r, mg is the gravitational mass of a star at radius r, v is its orbital speed and mi is the star's inertial mass (usually it is assumed that mg=mi, the equivalence principle). For the amazingly low accelerations in deep space MiHsC proposes that mi is much less than mg so that a gravitationally bound system should appear to have stars orbiting too fast, this is indeed the case. This is because MiHsC reduces the centrifugal force breaking them apart, allowing them to spin faster without exploding. Therefore, to prove MiHsC, a good plan would be to look for galaxies with mindbogglingly low accelerations, ie: low mass ones.

The most extreme such system has just been found by Laevens et al. (2015). Triangulum II is a dwarf galaxy, one of many orbiting our Milky Way galaxy, with very little visible mass in it: only 450 times the light output of the Sun, so the equivalent of 877 Suns in mass (Assuming star type K0 - thanks to Javier Freire Venegas for putting me right on the mass/light ratios) and it is only 34 parsecs in radius.

As expected, both Newton's and Einstein's models (General Relativity, GR) have a problem with this dwarf galaxy because they predict that any rotation speed above 0.34 km/s would blow it up (v=(GM/r)^0.5). But, Kirby et al. (2015) have just seen the stars zooming around it at 5.1 km/s! (with an error bar meaning that the speed is somewhere between 3.7 and 9.1 km/s). Assuming that this system is stably bound (something probable, but still debated) then to keep Newton and Einstein happy and stop it exploding you'd need to add 3600 times more invisible dark matter to it than the visible matter present. This is clearly becoming ridiculous.

MoND does a slightly better job. The MoND formula, which is v=(G*M*a0)^0.25 predicts an orbital speed of 2.1 km/s, but MoND relies on an adjustable parameter a0 which must be set by hand to be typically 1.8x10^-10 m/s^2 and MoND has nothing to say about where this number comes from.

MiHsC does an even better job, and it contains no convenient adjustable parameters. The MiHsC formula, v=(2GMc^2/Theta)^0.25, predicts a rotation speed of 3.0 km/s (in this formula c is the speed of light and Theta is the Hubble diameter). This Table summarises the observed speed and the various predictions:

  Observed     = 3.7-9.1 km/s (range of possible velocity dispersions)
  Newton/GR  = 0.34 km/s
  MoND          = 2.1 km/s
  MiHsC         = 3.0 km/s

Whether or not MiHsC agrees with the observation depends on the error bars in its prediction, and so I need to know what the uncertainty of the mass given for Triangulum II is (I'm writing a paper so will have to look closely at all the error bars), but the MiHsC prediction is clearly the best in the Table. As for the dark matter hypothesis, the amounts needed for this particular case are clearly ridiculous.

References

Kirby et al., 2015. Triangulum II: possibly a very dense ultra-faint dwarf galaxy. Astrophysical Journal Letters, 814: L7. Pdf

Laevens, B.P.M. et al., 2015. Astrophysical Journal Letters, 802: L18.

McCulloch, M.E., 2012. Testing quantised inertia on galactic scales. Astrophysics & Space Science, 342: 575-578. Preprint

A Case for Human Spaceflight

I spoke at a debate at Exeter University's debating society yesterday in favour of human, as opposed to robot, space exploration. Here is roughly what I said:

I would say that human spaceflight and settlement off-world is as inevitable and natural as the first fish crawling out of the sea, or humans leaving Africa, and this is why:

It is already possible, given the will: Six humans are living in space on the ISS which is already providing a dividend in showing Americans and Russians that they can co-operate. For this reason the ISS has been suggested for a Nobel prize. The Moon and Mars are settle-able in the next few decades, the Moon being the obvious first choice.

Even interstellar travel is more possible than you might think because special relativity says that time slows down aboard a spaceship moving very fast. So if you have an engine powerful enough to get you close to the speed of light, you can travel anywhere in the galaxy in the lifetime of a human on the ship, just not in the lifetime of people back on Earth. This gets rid of the need for generation-ships or suspended animation and reduces galactic colonisation from something that most people think is an impossibility, to merely a extremely difficult engineering problem (you have to accelerate and decelerate at 1g, 9.8 m/s^2, for a year, and then cruise).

New physics is coming, since general relativity has difficulty with galaxies (needing arbitrary dark matter), with cosmology (needing dark energy) and is inconsistent with quantum mechanics, and there are experimental problem like the EPR-Bell tests and other anomalies. I have suggested MiHsC to fix these problems.

Where do we go? Well, this is the time and place to ask that. Many exoplanets are now being discovered, some will be like the Earth, and one of the main centres for exoplanet research is here at Exeter University.

So if it is possible, is it a good idea? I would argue yes as follows:

Insurance: Humans have had a long and painful struggle to civilise (well, partially anyway) and we have something unique to say. It would be a shame if that was lost. Off-world colonies are essential so that if the Earth is damaged by an asteroid, nuclear war or climate change, humanity will endure and our long history will not be in vain.

Finite planet: Earth's resources are finite, and yes, we should learn to be sustainable, this will also help us with space travel and settlement, but even with sustainable policies, resources will eventually run out on the finite Earth. Space offers infinite or at least mind-boggling resources.

The need for challenge: humans have an innate need for challenge, and the challenges on Earth are running out and in these circumstances there is the danger of degenerating into a stagnant heirarchical society where a few try to make money off the rest. We need a collective and hopeful project, like Project Apollo, to bind our society together and give everyone hope of a better future. Hope is important. Also, the failures of a system can often only be seen by looking at it from the outside, that is increasingly difficult in our connected world.

Cultural diversity: The culture of Earth is becoming more uniform and this is a shame since it leads to sterility. There is very little option now to try radical new ideas on Earth, but if some people left the planet they could start radically different societies and experiment with them, just as the Pilgrim fathers did and devised a better constitution, and other brilliant inventions, eg: pizza.

The imperative: If we look at plants & animals we see the huge resources they put into reproduction, for example Salmon return over whole oceans to their birth place to reproduce. Evolution has made them that way since the ones who couldn't be bothered left no offspring. Lovelock has suggested that the Earth is an organism. If so, then it is logical to say it intends to reproduce. Is it developing us, a space-faring species, to do that?

Exploration by proxy is shallow: History tells us that if you send people to new environments, in this case other planets, they'll invent things we'd never dream of. One example is Charles Darwin who went to the Galapagos Islands and noticed the animals varied from island to island and thought of evolution. Robots are not yet creative like this. A robot on the Moon may be the eyes for someone back on Earth, but that someone is still on the Earth sat on a chair. If the person was on the Moon, they would think in a different way and could be a new Thomas Jefferson or Darwin, inventing a better society or a better way to generate energy.

The importance of human exploration is instinctively understood: almost no-one remembers the first probe to the Moon (Luna 2) but everyone remembers the first human. You can’t predict the ideas space settlers will have, but you can help it to happen by voting for human spaceflight today.

How can MiHsC be applied to a hot star?

Peter Reid just asked me this following question: 'For one of those stars near the edge of a galaxy, wouldn't its individual particles still be accelerating quite a bit, since they are part of a seething ball of plasma? It seems like that should make the minimum acceleration not apply to the individual particles, and so not apply to the star as a whole. How do you account for this?'

This is a good question because MiHsC usually only produces anomalies for things at very low accelerations, so how can it predict anomalies for stars with huge thermal accelerations inside? The diagram below explains how. It shows a star (the yellow circle) orbiting the galaxy (the centre of which is to the left), with an orbital speed shown by the arrow pointing up. The schematic shows five hot, highly-accelerated particles inside the star (the red circles) and their acceleration vectors (the black arrows). Each particle has a large acceleration and so a Rindler horizon forms close by in the opposite direction (the black curves) and this horizon affects the particle's own inertial mass due to MiHsC, but since there are a lot of particles and they are moving randomly in the plasma, the black Rindler horizons are distributed randomly around the star and they therefore have no effect on the star as a whole (we'll forget the star's spin for now, which is a small acceleration in comparison). In this schematic there are only five particles, so it may not look like the black horizons quite average out, but in a star there are a very large number so the average will be very good.

Each particle within the star also has a tiny acceleration that it shares with all the other particles due to the orbit of the star in the galaxy. In the diagram this is shown by the light blue arrows, which are all pointing at the galactic centre to the left. The Rindler horizons associated with these smaller accelerations are much further away because the orbital acceleration is ridiculously smaller than the thermal, and these horizons must be far off to the right hand side, something I can't represent well on the diagram (see the blue curves surrounded by the dashed circle). This circled pack of horizons is the composite horizon that MiHsC applies to stars, or any object, as shown in the previous blog. If you consider an object as a whole, you can ignore its particle's individual horizons which average out, and just consider the composite horizon due to its combined acceleration, and figure out how Unruh waves hitting it are sheltered by that.

I've been asked other insightful questions recently, so I'll answer those in following blogs...