Science Conjecture

This page contains some comments and conjecture* about science topics. It was inspired by the work of Carl Sagan. Be skeptical about things appearing on this page (and on many other web sites) - check the facts yourself. See Carl Sagan's Baloney Detection Kit.

Quote from a BBC interview with Douglas Adams : "Technology is a word which means something that doesn’t work yet".

* "Conjecture" - guess, assume, hypothesize, imagine, surmise, dare say.


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Contents

[Astronomy] [Computing] [General Science] [Road Safety] [External Links]


Sites created by Michael Paine

Astronomy
• Two tides per day?- the Moon passes overhead once per day - why are there two high tides in most parts of the world?
• Life on Mars - from Earth? see also Swapping Rocks
• Where would you locate a base on the Moon?
• The Planetary Society Australian Volunteers - news and links about planetary science
• SETI - the search for extraterrestrial intelligence. Join SETI@home (external site)
• Australian Spaceguard Survey - the search for asteroids and comets that might collide with Earth
• Tsunami from asteroid impacts - create a similar tsunami in your bathtub using a bursting balloon
• "Recent" lunar impacts:
• Apollo mission seismometers and
• an impact observed by monks in 1178AD - crater Giordano Bruno
• Index to my "Rocks from Space" column in Explorezone (a US science website) - also at Space.com

Computing

• Year 2000 - tips and links
• The DNA Computer - billions of calculations in a test tube!
• The Quantum-Mechanical Computer - billions of calculations by jostling atoms!
• One page introduction to HTML - the language of the Internet
• Shattered Windoze- some serious and humerous criticism of the popular but annoying operating system. With more from Douglas Adams.
• Some WAV files from the TV/Radio show Hitchhikers Guide to the Galaxy

General Science

• Darwin's Natural selection - elegantly simple computer program to illustrate to power of mutation/variation and competition for resources
• Eye damage from laser pointers - they are definitely not toys
• A model for gravitational and electrical fields - made from kitchen items
• A Hand-held Photon Propulsion System for Astronauts ;<)
• Pistol starts to races - are they fair?
• Hydrodynamics of surfboards
• GEMFIND - a computer program to plot the location of gemstones on a scaleable map of Australia - great for planning an Australian holiday
• Australian snowfall statistics - for skiers
• Greenhouse gases and global warming.
• Perpetual Motion and the Big Wither.
• Pet parasites might alter the human brain
• Energy from rain drops

Road Safety

• "Physics of rollover crashes" including some interesting video snapshots of heads out of windows and driving tips to avoid the dangerous rollover crash.
• "Flashing Warning Lights on School Buses" - the science of signal lights
• Devices to help drivers control their speed - the risk of a fatal crash rises exponentially above the optimum speed for the conditions
• Four-wheel-drive/Sport Utility Vehicles - not all fun, there are road safety, economic and convenience issues to consider before you buy.
• Shortcomings in vehicle design exposed by offset crash tests.

Other web sites with science stuff (external links - some may no longer work)

• Explorezone - many interesting science items and links
• Frank Potter's Science Gems - thousands of links
• Dr Karl Kruszelnicki - (Australian) ABC Triple J Radio Show with live internet chat Thursday at 11am Sydney time
• The Australian Museum - Sydney
• Powerhouse Museum - Sydney
• Exploratorium
• Quantum - Australian ABC TV Show
• Robin Williams' Science Show on Australian ABC Radio
• The Why Files - great explanations of science issues
• Scientific American - Editor's web selections.
• Britannica - online at last - worth the wait.
• NOVA - Australian Science News
• EurekAlert - list of global science press releases
• How stuff works - car engines and much more
• Gemini - Norwegian science research magazine
• Earthscape - University of Columbia
• Star Class - learning astronomy
• Innumeracy.com.
• Dr. Odenwald's ASK THE ASTRONOMER
• Origins Education Forum - from the Big Bang to the origin of life
• First Sunrise of the New Millennium - US Navy FAQ.
• NASA's Solar System Exploration Education and Outreach Forum
• Sun-Earth Connection Education Forum
• The Universe in the Classroom - Astronomical Society of the Pacific
• Dihydrogen Monoxide FAQ - a common household compound can be hazardous ;<)
  

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• Demonstration of hammer and feather dropped in vacuum Apollo 15 on the Moon (link to external site). See also NASA History of Apollo

Science units and measurement:

(thanks Engineers Australia)
• OnlineConversion.com
• Dictionary of Units of Measurement
• TechEncyclopedia
• Unitconversion.org - free online conversion for a huge range of units
  


Suggest a link for this section


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There is no copyright on the following material but if you use it acknowledgment would be appreciated.


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Two tides per day?

(first posted September 1996)
Why is there a high tide on the side of the Earth opposite the moon? The answer is that the Earth and Moon revolve about their common centre of gravity (barycentre) which is about 4700 km from the centre of the Earth (in the direction of the moon). This "dance" produces a small centripetal acceleration which varies according to distance from the barycentre. At the centre of the Earth the centripetal acceleration exactly balances the gravity effects of the Moon (that is why the Moon is in a stable orbit!). This is not the same centripetal acceleration that results from the rotation of the Earth - the main effect of this rotation is to cause any point on the surface of the Earth to pass through the two tidal "high spots" each day.

The following diagram shows the effects at the Earth's surface. On one side the high centripetal acceleration is partially cancelled by the Moon's gravity. On the other side the smaller centripetal acceleration combines with the Moon's gravity. The Earth's oceans therefore experience a similar magnitude of
acceleration on either side - producing two high tides per day!

Note: this explanation is in some high school science texts but is rarely covered in popular encylopedias. The values in the illustration are guesses but are in roughly the correct proportions.



The actual tide-producing factors are fairly complicated - see this great NOAA explanation with diagrams (thanks  Frieder Gross-Alltag)

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Life on Mars

(first posted October 1996)
The debate could rage for many years on the possible discovery of primitive life on Mars.

One matter which should not be overlooked is the possibility that early life was transported from Earth to Mars in a similar manner to the way the Martian "fossil" got to Earth. It could even be that life started on Mars (or elsewhere) and seeded the Earth in the same way. The July 1994 issue of Planetary Report has an article Swapping Rocks: Exchange of Surface Material Among the Planets by H Jay Melosh. The article explains how this might occur and covers ejection, transit and "re-entry". It is estimated that about half a tonne of Martian material falls to Earth each year.

Consider the odds in the case of the Martian "fossil" meteorite: A rock containing micro-fossils was blasted off the surface of Mars by another meteorite some 15 million years ago. This orbited the Sun until it fell to Earth on Antarctica some 10,000 years ago. On the Earth today, what are the chances of a rock containing a fossil being picked up compared with one containing live organisms? I would suggest at least 1000 times less! On Earth today (or Mars 15 million years ago), what are the chances of a chunk of rock being blasted into space by a meteorite impact, compared with the conditions 4 billions years ago? Meteorite impacts were much more frequent at that time (when life is thought to have arisen). This suggests that the chances are also at least 1000 times less. The odds of a Martian fossil being blasted into space 15 million years ago are therefore likely to be at least 1 million (1000 x 1000) times less than the chances of a rock containing live organisms being blasted into space 4 billion years ago!

Assuming that some of the organisms could survive the journey through space then the possible discovery of a Martian fossil on Earth at least suggests the possibility of Mars or the Earth being seeded from space.

Update Jan 97: Exchange of early life between Earth and Mars (in both directions) could help explain the recent finding of possible signs of life on Earth some 3.9 billion years ago, before the massive asteroid bombardment which heavily cratered the Moon. The sequence might be: life gains a foothold on Earth (either evolves or is seeded from elsewhere); Earth rocks with live organisms reach Mars and life is established on Mars; Earth is bombarded by asteroids, destroying any life here; Mars rocks reach Earth, re-establishing life here. Carl Sagan pointed out this possibility in 1988!

Update May 98: Chris Chyba's paper "The Origin of Life in a Cosmic Context" in the newly published book "Carl Sagan's Universe" discusses the possibility of "panspermia" between Mars, Earth and Venus.

See also New Scientist Survivors from Mars by Paul Davies and his new book 'The Fifth Miracle' which explores these ideas, and many more about the origin of life. Carl Sagan's popular science book Planets , written in 1966, refers to the possibility rocks from Earth seeding the Moon with microbiotic life.


This discussion is continued on the Transpermia web page.


Additional Links

• The Planetary Society Australian Volunteer Coordinators
• NASA/LPI
• Yahoo - science category - life on mars
• Scientific American Dec 97 Issue
• London Open University
• Life in the Universe
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Where would you locate a base on the Moon?

 
Near the lunar South Pole!

First posted December 1996. Updated 13 Dec 1997 based on advice from Chris White.

The Moon is a body of extreme cold and extreme heat. On most locations on the moon daylight "day" lasts 14 Earth days then there are 14 Earth days of darkness - pretty harsh conditions. However, the tilt of the Moon's rotational axis is only about 1.5 degrees to the Earth/Moon's orbital plane around the sun. There is a giant basin (dip) at the lunar South Pole which has large areas in permanent darkness. Furthermore, some points on the rim are in permanent sunlight. Therefore a base located at the South Pole would have permanent access to very cold and very hot locations - ideal for generating electricity (the principle of an electric power station is that there is a source of "heat" which is at a higher temperature than the surroundings). Unlike on Earth, there is no atmosphere to diminish the intensity of sunlight at the poles but the collectors would need to face nearly horizontal.

There is talk of mining Helium on the moon to generate power by nuclear fusion. Even if the huge difficulties of building a fusion reactor on the moon could be overcome (assuming that a fusion reactor is, in fact, possible), it seems to me that the best source of fusion power (the Sun) is being overlooked.

Links (several of the reference articles have limited web life)


• 4 Jun 1999: Explorezone item Spaceship to crash land on Moon - NASA is looking at crashing the Lunar Prospector spacecraft into Mawson Crater at the Moon's South Pole on 31 July this year. They will look for water vapour in the resulting impact cloud. Also BBC item about radar mapping of this region
• 4 May 1999: CNN article Scientists pinpoint potential sites for moon colonies "Three sites, located near the moon's south pole, provide nearly constant  sunlight, the researchers report in the May 1 edition of Geophysical Research Letters..." Told you so! ;<)
• 16 Mar 1999: BBC article "Best site for Moonbase revealed"
• NASA's Lunar Prospector finds ice at the moon's poles
• Planetary Science Research Discoveries Hawaii University, article "Ice on the Bone Dry Moon" by Paul D. Spudis. Has a good illustration of the orbit of the moon showing how the South Pole is in permanent shadow (see thumbnail below).
• The Planetary Society "The European Moon Program", Jan/Feb 95 issue of The Planetary Report
• Scientific American, March 1990 "Observatories on the Moon"
• CNN Science
• Apparently this idea goes back to at least 1961, when Ken Watson, Bruce Murray and Harrison Brown suggested that ice might be collecting in the shadowed craters at the lunar poles (see Scientific American May 1998, page 15).

 

 
 
 
 
 
 
 
 
 
 



• Update 3 August 1998: The July/August 1998 issue of Planetary Report has an article "The Hunt for Lunar Ice" by James D Burke. It includes the following illustration of a base at the lunar pole with a solar collector located on a mountain in permanent sunlight. (painting by Marilyn Flynn). More detail of the solar furnace.
• 10 Jul 03 SpaceDev: SpaceDev To Design Lunar Dish Observatory Mission
• 20 Mar 04 BBC: Lunar mountain has eternal light. [North Pole]
• 21 Sep 05 Space.com: Moon-to-Mars Plans Emerge: New Agenda or Apollo Retread? - A key goal is to use water ice that may be stashed within permanently shadowed craters at the Moon's poles...
• 5 Dec 06 Forbes: NASA Says It Will Set Up Polar Moon Camp.
 

 



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Darwin's Natural Selection

 
(First written in Locomotive Basic in 1987)
For a dynamic and elegantly simple demonstration of the mechanism
of natural selection see Freeware.

Sample screen dump.


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Model for gravitational and electrical fields

(First posted January 1998 - idea first seen in Carl Sagan's 1980 Cosmos TV series)
In physics a "field" is a region of influence surrounding an object. It is difficult to picture gravitational or electrical fields - the traditional field lines don't mean much. With a piece of plastic cling wrap and a large bowl or pan from the kitchen and some spherical lead fishing weights you can create a simple model of a gravitation field or electrical field. Watch the movement of the balls change the shape of the plastic wrap. You might be able to get them to partially orbit one another before they roll together under mutual "attraction". (Wash your hands thoroughly afterwards to remove any lead).

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Pistol starts for races

(First posted January 1998)
Is the runner closest to the starter pistol at an advantage?

The speed of sound is roughly 300 metres per second (actually 344m/s). If the runner in the outside lane is 6 metres further away from the starter's pistol than the runner in the inside lane then the sound of the pistol will reach that runner 6/300 = 0.02 of a second later. Therefore the inside lane runner has two-one-hundredths of a second advantage. Given that world-level races are won and lost in less than one-hundredth of a second it is important that this effect is taken into account (is it?!).
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Pet parasites might alter the human brain

This low-key article from New Scientist might be the key to explaining people's response to pets:

Parasite hijacks brains with surgical precision
A mere parasite controls the fate of rats and mice by hijacking the part of the brain that makes the rodents naturally fear cats, a new study shows. Rats and mice normally flee if they smell cat urine, but not if they're infected by the protozoan parasite Toxoplasma gondii. The parasite can only complete its life cycle if its rodent host is eaten by a cat, so it "brainwashes" the creature into apparently liking the scent.  

and Cosmos magazine: Parasite gives rats suicidal cat attraction

...It is spread when the parasite is passed out in cat faeces and contaminates soil, where rats and mice pick up the infection. The parasite's lifecycle is completed when the mind-altered rats, which have been shown to be less fearful of cats and have slower reaction times, are caught and eaten...Around 15 to 20 per cent of Americans are infected with the parasite...

So there is a possibility  that similar parasites, passed on by pet cat or dog saliva or faeces, might alter the brains of their human owners. This might explain why some dog owners do not experience revulsion at dog "functions" that are not accepted behaviour by humans - urinating and defaecating in public and licking the face of people (particularly children). These actions should have been bred out of dogs after thousands of years of domestication and selective breeding.

Energy from rain drops

How much kinetic energy is in falling rain?

Say we have 10mm of rain falling in one hour. That means 0.01 x 1 x 1 = 0.01 cubic metres = 10 kg per hour.

Wikipedia states that a 5mm diameter rain drop hits the ground with a speed of 9 m/s. The kinetic energy of 10mm of rain falling on one square metre of ground for one hour is therefore ( half x mass x velocity squared):

0.5 x 10 x 9 x 9 = 405 Joules (per sq m per hour) = 0.11 Watt-hours (per sq m per hour)

Therefore a heavy rain shower will deliver (power of) about 0.11 Watts per square metre (compared with a solar panel that generates about 200 Watts per square metre under good conditions). Of course there would be major loses converting the rain's kinetic energy into usable energy.

Oh well ...

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by Michael Paine (home)
Last update February 2005.
Background - Voyager image of Jupiter by NASA.
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