The Fermi Paradox

“The Fermi paradox (or Fermi's paradox) is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilization and humanity's lack of contact with, or evidence for, such civilizations.“ (Wikipedia)

If you had moved home to a new location far away from your previous one, and wanted to go out and make friends, which of these is least likely as a place to look:

            Sporting club?

Social club?

            Educational institute (e.g. evening classes)

Special interest group e.g. Astronomy society?

            Street full of knife-wielding brawling drunks?

I’m assuming you picked the last as the least likely.  On that basis, why would inhabitants of another planet pick Earth as a planet to be friends with?

For all we know, we were visited in the distant past and have been shunned ever since because of the constant warring.

That, I believe, is the explanation for Fermi’s paradox, and, incidentally, why SETI is a bad idea. We need to be careful whose attention we attract: there could be planets out there whose inhabitants are even worse than ours.

Astronomy and Global Warming

An Astronomical society friend has commented that there seem to be fewer clear skies since he bought his telescope.

When I heard about global warming, I got an impression (shared, I suspect, by many) of rising sea levels and the weather becoming more prone to storminess. The main message, apart from “stop making CO2” was: “live away from low ground”. And there was the bit about the conveyor belt turning off and causing a mini-ice age around the British Isles.

The increasing propensity for flooding has shown (to me) an unsuspected aspect: that of higher humidity and rainfall due to the warmer atmosphere.

When the ice melted after the ice age, the air temperatures were relatively low, so the extra liquid water stayed in the sea, raising sea levels. At the relatively warmer air temperatures of today, the glacial  melt water is evaporating, raising humidity levels, increasing cloudiness and producing more rain; hence the flooding. Also, I suspect, this process is maintaining the salinity of the oceans and, with it, the operation of the conveyor belt.

So the message is not so much “stay away from low level” as “stay away from rivers and valleys”. And councils need to make sure there is good road drainage, especially on hilly roads. Last winter, when returning to Sussex on a wet evening, I was appalled at the large puddles in the right hand lane of the M4: a recipe for disaster.

I wonder how many people are aware of the latent heat of fusion of ice. Ice doesn’t automatically turn into liquid water at 0 degrees Celsius. The ice requires a further dose of heat to change state from solid to liquid. That’s called the latent heat of fusion. It is possible for ice to be raised to 0 degrees just before winter, then, effectively store heat until the following spring, when it finally melts. This might help to explain why unexpectedly large pieces break off from polar glaciers. The recent BBC TV programmes Operation Iceberg showed that there is still a lot being learnt about glaciers and icebergs

Longer term, the situation is more complicated, goes further.

With the increased cloud coverage we will presumably see a greater greenhouse effect, which implies accelerated global warming. Our “evil twin” neighbour, Venus, is completely engulfed in cloud, and its surface temperature is 560 degrees Celsius; not a comfortable place to be.

Venus is about two thirds of our distance from the Sun, which means that, under the inverse square law, it gets more than double the Sun’s radiant energy, compared with the Earth. I suspect that Venus has much more internal heat than Earth: the extra radiation it gets from the Sun may have delayed the radiation of its own heat. Not only that, but its clouds are somewhat darker, (being sulphur dioxide-based) than our white water vapour clouds. That means that a fully cloud-shrouded Earth could display a higher albedo (the property of reflecting radiation) than Venus does. Currently Earth’s is much lower than Venus’s. The higher albedo of a cloudier Earth would deflect more of the Sun’s radiation, than currently, and could potentially allow the planet to cool itself down again. Once the planet has cooled, the polar ice could reform at the expense of the humidity and cloud cover, taking us back to “normal”.  So perhaps the Earth is self-regulating in that respect.

Clever planet is the Earth. There’s more to the Goldilocks zone than mere distance from the Sun!

Don’t hold your breath, though, it’s a very slow process.

Meanwhile, from an observational Astronomical point of view, and in the short term, I see a continuing reduction in the number of clear-sky nights for observing, and an increase in the need for dew management. Reputedly, a hazy sky yields improved seeing, so, at least, we should get clearer views when we can see the stars.

Conclusion: treat every clear night as if it’s the last!

12 days of Christmas for Astronomers

 On the first day of Christmas my truelove gave to me….

A black hole that swallows street lights

2 Adjuster screws and …..

3 Red LEDs

4 Dew strips

5 Parfocal rings!!!!

6 Colour filters

7 Sisters sparkling

8 Mounts a-moving

9 Guidescopes guiding

10 Tripods tripping

11 Lenses looking

12 APOs pointing

Black Holes are Misunderstood

 Despite the myths, the gravitational pull of a black hole is caused by its mass and, for distant objects, is no greater (initially) than that of the star that collapsed to form it. It doesn't suddenly develop a stronger gravitational pull simply by changing from a star to a black hole.  Obviously as it swallows more matter, its mass increases and so does its gravitational pull.

The scary bit about a black hole is that you can’t see it, because it’s hiding behind its “event horizon”; the invisible sphere, surrounding the black hole, from which light cannot escape. So you could accidentally stray into its gravitational field without knowing it’s there, until you suddenly feel yourself being strongly pulled towards it!

The radius of the event horizon (on formation) is very much less than the radius of the star that collapsed to form it. While the radius of the Sun is 7 x 10⁸ m, that of a Schwarzschild black hole of 10 solar masses is only  3 x 10⁴m. It’s only when you get closer to the black hole than the radius of the original star, that the weird stuff happens.

Distant objects are no more strongly pulled towards a black hole than towards a star of the same mass.

When a star collapses to form a black hole, it loses mass due to the energy squeezed out, according to Einstein’s mass/energy relationship. (E=mc²).

The minimum mass required of a star to become a black hole is about 6 solar masses. Less than that, it becomes a neutron star, and if much less it becomes a white dwarf.

We could not create a black hole accidentally on Earth because there is nowhere near enough mass in our neighbourhood to be able to do so. The Sun contributes 99% of the mass of the solar system, and the nearest massive objects, outside the solar system, are in the constellation Centaurus, 5 light years away.

Maybe some of the Centaurus constellation stars, at that distance, could potentially merge at some time in the distant future, and become a black hole, but at that distance would exert no bigger gravitational pull, on us, than they do now.

You can all calm down now.            

Olbers' Paradox

This states that if the universe was infinitely large, there would be a star along every possible line of sight and the sky would at all times be uniformly as bright as the sun. (Day and night; no dark bits!)

This argument presupposes that an infinitely large universe would contain an infinite number of bright objects. That is not necessarily the case.

According to currently prevailing theories, the universe is expanding at an increasing rate due to SPACE expanding. The total mass/energy in the universe has been estimated and is therefore finite. It is not believed to be increasing in mass/energy. Rather the total mass/energy density is decreasing.

Were the "finite" universe, as we see it today, to expand infinitely, in space terms, there would be no increase in the number of bright objects, and the sky would appear pretty much as it does today, albeit with some moving about. In fact, I believe (as many do) that it will become dimmer.

We would then have an infinite universe without a star on every possible line of sight.

Hence Olbers' paradox would appear to be flawed.

The Twelve Days of Christmas for Physicists:

The Twelve Days of Christmas for Physicists:

On the first day of Christmas my true love gave to me (etc.)

A glimpse of the Higgs Boson

Two spin dimensions

Three quark flavours

Four outer planets

Five years of funding!!

Six carbon protons

Seven new dimensions

Eight branes a-bumping

Nine telescopes tracking

Ten neutrinos speeding

Eleven strings vibrating

Twelve theorists thinking

A Eureka Moment About Genes

For a while, now, I’ve been intrigued by the parallels between genes/DNA and computer programming.

The salient points are:

                Modular programming

                Self-modifying code

Computer programs are structured as functionally oriented, self-contained modules. The advantages being:

The programming task can be shared between many programmers to reduce development time.

If the program is subject to modification, only the relevant module(s) need be amended and released to the user, reducing download time

A specialised module can be given to a similarly specialised programmer, to improve the quality of the developed module

Every program application on your computer has large numbers of such modules (suffixed by “.dll”).

The relevance to genes should be partly apparent by now. Genes are also functionally specialised.  We have learnt to swap out troublesome genes from an organism and replace them with good ones.

Question: how does a single egg, divide in two, repeatedly, until, 9 months later, we have a human being containing thousands of different types of cells, when we started with only one type?

A partial answer would be a form of self-modification.  In computer programming there are several types of language or development tool.  The most primitive form of programming is direct operating code programming, but more usually assembler programming, as it’s called. At this level, the program code can directly address memory locations to modify data but also its own program code.  So we can have a code loop (sorry, lots of “gotos” involved) and incorporate an instruction that modifies one of the others in the loop, so that it does something different each time around. A similar operation in genes would enable a cell in, say, the liver to evolve to connective tissue instead of liver cells, next time it divides. In a computer program we would use counters and change cell types on reaching a specified value in the counter.  We could, in fact, develop a complete computer model of the development from egg to human using this method. I had been wondering how this counter approach could be implemented in genes/DNA. Then I watched Prof Jim al-Khalili’s chaos TV program. 

Now to my “eureka moment”:

It took a while, then I realised that cells don’t need to count as such, they just do their thing. It’s all down to chance. If it makes too many, or not enough, cells of the right type, the organism will, as likely as not, be sickly and perhaps die.  The rest is up to Darwin. Eureka!