As a youngster, a friend of mine owned a Datsun 240K automatic. Some of his friends had V8s. He discovered however that he could do some impressive burnouts by selecting reverse at highway speed & flooring it!

The argument is over the relative speed of one back tire spinning, compared to the road below.

The following are given:
1. Vehicle speed 120 km/h.
2. Engine at redline, consulting gearbox ratios extrapolates this to 100 km/h in reverse.
3. Open diff, so one tire does not slip at all, but remains in contact with the road while the other spins backwards.

So, does anyone have an idea what the relative speed difference was under those conditions?

His view, by assuming the same ratios as when driving at slow speed in reverse, results in a rear wheel speed equivalent to something over 400 km/h.

My view goes something like this. First, it seems inescapable that if the gearbox engages immediately and if there is no slippage in the torque converter, then the instantaneous situation would be that the engine must be rotating backwards. That simply isn’t possible, so we have to assume major slippage in the transmission.

Assuming there is slippage even for a brief period, then where is it? The torque converter is by far the best candidate. We know that a heavy load can switch a torque converter out of coupling mode (that happens if you tow something too heavy in too high a gear). So we get the following sequence of events.

1. Reverse gear engaged in gearbox.
2. Front shaft of gearbox reverses, breaks torque converter out of coupling mode (stator locks).
3. Engine goes to full power, peak revs.
4. Torque converter passes magnified engine torque back to gearbox.
5. Gearbox passes torque (reverse direction) back to diff and to wheels.
6. Torque exceeds limiting friction of one tyre, wheel slows down and may reverse.
7. Steady state is reached when torque transmitted by the engine is equal to torque transmitted from two wheels, one slipping.

If this is the situation, then it’s not possible to predict exactly what the slipping wheel is doing, but I would guess rotating slowly forwards (same direction as road).

Google was not my friend.

It’s rare to read a negative book review from the scientific community written with this kind of candour and certainty. Stephen Wolfram of course is the author of Mathematica and a pretty bright lad. Seems he went astray somewhere, or at least this reviewer thinks so.

The book is “A New Kind of Science”.

The reviewer calls it “A Rare Blend of Monster Raving Egomania and Utter Batshit Insanity.”

Worth a read, even if you have no interest in the book, science, Wolfram…

This article is about Keirsey personality types. See Keirsey describes four main types.

  • Guardians speak mostly of their duties and responsibilities, of what they can
    keep an eye on and take good care of, and they’re careful to obey the
    laws, follow the rules, and respect the rights of others. (SJ 40-45%)
  • Idealists speak mostly of what they hope for and imagine might be possible for
    people, and they want to act in good conscience, always trying to reach
    their goals without compromising their personal code of ethics. (NF 15-20%)
  • Artisans speak mostly about what they see right in front of them, about what
    they can get their hands on, and they will do whatever works, whatever
    gives them a quick, effective payoff, even if they have to bend the
    rules. (SP 30-35%)
  • Rationals speak mostly of what new problems intrigue
    them and what new solutions they envision, and always pragmatic, they
    act as efficiently as possible to achieve their objectives, ignoring
    arbitrary rules and conventions if need be. (NT 5-10%)


Couple of people have asked me about this, and I did a little research.

The quoted energy usage for early model reverse osmosis desalination plants is around 6 Watt-hours/litre. More modern plants appear to be more efficient and the quoted figures for WA and Vic are 4.1 and 4.6 respectively. A kilolitre of water costs around $1.

Assuming a modern shower head using 9 litres/minute and a 5 minute shower, the energy cost of a 45 litre shower using desalinated water is around 200-250 Watt hours. [In Vic that is about 240-300 gm CO2.]

But think for a moment about the cost of heating the water. Most people shower in water at around 43 degrees C, which is around 30 degrees above the temperature of cold water. It costs 4200 Joules to heat 1 litre of water by
1 degree C and 1 Watt hour is 3600 Joules. Putting the numbers together you get 45 * 30 * 4200 / 3600 = 1575 Watt hours (1800 gm CO2). Boiling water is around 3 times the energy cost.

So before you complain too loudly about the cost of desalination, remember that heating water for your shower costs roughly 6 times as much energy as desalinating the water.

You’ve heard of Einstein’s attempts to formulate a Grand Unified Theory, you’ve probably heard of String Theory and perhaps even Quantum Gravity. But have you heard of Holographic Space-Time?


Scientific American recently published an article by Max Tegmark, which provides calculations for a particular kind of infinite universe.

Although I think his use of the word “infinite” is a bit loose, he is careful to define exactly what he means, and his logic is scientifically valid. His argument is as follows:

How much energy do you use? Do you have any idea?

Here in Melbourne we have been subjected to an unrelenting campaign of messages and restrictions aimed at reducing speeding and drink driving. No-one can have missed the message, and anyone who gets caught must not have been paying attention. Anyone driving here will know it works.

Likewise there has been a campaign of rules and announcements aimed at making us conscious of our water usage and reducing how much we use. This is personal consumption, where you get to turn off the tap. Everyone now knows that the target is 155 litres per person per day. It works: usage has dropped.

If anything energy usage and conservation is even more important, but does anyone know how much energy they use or how much they should be using? There is little doubt that a similar public awareness campaign could achieve similar results to reduce the the energy we have direct and personal control over as a consumer: the energy each of us could use less of by our own direct actions.

Imagine that the universe is a simulation. What kind of computer would it take to run that simulation?

Just to be clear, imagine that every human intelligence on the planet is actually a piece of software running in a cosmic supercomputer, and that nothing else really exists. Everything you see, every sensory impression of any kind, is the result of executing an algorithm and evaluating some formulae. The sky, oceans, plants, even other living animals are all created to the extent that anyone is paying attention to them, and otherwise are simply not there. Ditto for physics, astronomy and the heavenly bodies: created and modelled for those who look at them.

[Yes, we could economise by only simulating a few people and creating all the others as needed, but that’s not the point.]

So how much computer power would it take? Hard to say, but perhaps not as much as you might think.

Mind you, whoever created the simulation and is now watching its progress might themselves be a simulation in some higher computer. Think about that for a while!

Speaking of good science, here is a nice article and video about the Hubble Ultra Deep Field.

It includes a “fly through” of ancient galaxies.

The earliest galaxies visible are 13 bn years old, were created when the universe was 0.5m years old, and are now 43 LY away and (although not actually moving much) are receding due to space time expansion at more than light speed.

Senator Fielding has been outspoken in questioning anthropogenic climate change. I wondered who was advising him.

David Evans seems to be not a climatologist but a mathematician who builds climate models.

Here is a summary, as I understand it. I think there are serious questions here to be answered, but I cannot answer them.


  • Global warming is on trend at around 0.5C per century since the end of the little ice age in 1700.
  • There is a roughly 30 year cycle, with rising temperatures from 1975-2001 and flat to cooler since then.
  • CO2 was 280 ppmv pre-industrial, started rising seriously in about 1945, now 389, still rising on a steady trend.
  • Ice cores show correlation of CO2 and temperatures, with temperature rising 800 years before CO2 (100,000 years).
  • Geologic evidence shows no consistent correlation over earlier periods (many millions of years).
  • There is no geologic evidence of runaway positive feedback despite higher CO2 levels (see later). [Accepted???]
  • Specific predictions made by main models (eg tropical hotspot) have not happened. [Accepted???]
  • Recent direct measurements of climate sensitivity produce an estimate of around 0.5C. [Accepted???]

Known theory (accepted):

  • [Climate sensitivity means how much warming for doubling of CO2 (280 to 570 in 2070)].
  • As GHG without feedback, climate sensitivity is 1.2C. Any deviation from this figure requires feedback because of effect on water vapour. Positive feedback means high figure; negative feedback means lower figure.

Model theory (not accepted):

  • Most assume (without evidence) positive feedback so climate sensitivity is roughly 3.3C (but could be higher or lower).
  • All predictions flow from this assumption. One prediction is the tropical hotspot, but this has not happened (so the model is wrong?).
  • If climate sensitivity is actually 0.5C (negative feedback) then the models produce totally different results.

If you remember just one question, remember this one: climate sensitivity: is the feedback positive or negative?

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