Physics
Between 1998 and 2001 I measured background radiation in Fourmilab's
computer lab with a Geiger-Müller tube interfaced to a
computer. Analysing the data revealed both an apparent divergence
from a Gaussian distribution of counts per minute and a
variation in background radiation with time of day. This page
presents the data, analysis, speculation on possible causes, and
provides a link whence you can download the data and programs
for your own investigations.
“What is the heaviest stable element?” This question,
easily posed, is not so easy to answer. In fact, nobody
knows. This document explores the stability of heavy
elements, the difficulty of experimentally confirming theoretical
predictions of very rare events, and elements whose half-lives are
longer than the lives of all stars in the universe.
Cellular Automata Laboratory
invites you to explore the world of cellular automata with
the aid of a high-speed programmable simulator which runs
within your Web browser. Cellular automata rules are defined
by short programs written in JavaScript or Java. Rule
definitions in JavaScript are compiled directly inside the
browser and do not require installing a programming
environment on your machine. The accompanying on-line
laboratory manual
explains the theory of cellular automata, how to use the simulator
programs, documents the many ready-to-run rules included,
describes how to create your own original experiments,
and contains a comprehensive bibliography. A development
kit supplies source code for all of the rule definitions
and the files they use, providing a starting point for your
own explorations. New:
2017 update
includes browser-based simulation and JavaScript rule
definition.
The only reason Einstein's special theory of relativity seems weird to those
learning it is that the velocities we're familiar with are such a tiny
fraction of the speed of light we've never had a chance to
gain an intuitive sense of relativistic effects. If the speed of
light were 100 kilometres per hour, footballers would have no trouble
dealing with relativistic goal shots. C-ship
uses computer image synthesis to put you aboard a starship entirely
consistent with the laws of physics and lets you look out the window to
experience special relativity with your own eyes.
This “basement science” experiment demonstrates the universality of
gravitation, showing the gravitational attraction between masses of
less than a kilogram. Could Archimedes have discovered universal
gravitation nineteen centuries before Newton? Well, let's see….
An interactive animation illustrates how orbits around compact
objects such as neutron stars and black holes depart drastically from
Kepler's laws, and explains why.
Update: January
2017 update uses HTML5/JavaScript animation,
eliminating the need for Java, and improves graphics rendering. The
original Java version
remains available.
Quantum mechanics teaches us that, at the deepest level, uncertainty
rules the universe: there are things we cannot predict, even in
principle. HotBits harnesses this fundamental
uncertainty of nature to generate truly random bits, unlike the
pseudorandom sequences created by an algorithm on a computer.
Along the way, you'll find a discussion of the hardware and
software used to generate the random bytes comprehensive enough
to build your own, and peek under the hood
of quantum mechanics to see why the data are genuinely random,
and some of the implications of all this.
On October 15th, 1991 a proton
with an energy of 3×1020 electron volts slammed into in
the Earth's atmosphere. Let's crunch some numbers…. A
performance comparison with 24th century Galaxy Class
starship technology is presented.
An English language translation of Albert Einstein's 1905 paper which introduced
Special Relativity, as published in the 1923 book
The Principle of Relativity.
This document is
is both a monument of twentieth century physics and
a masterpiece of scientific communication. In addition to
the Web edition,
a ready-to-print
PostScript
file and
LaTeX source code
of this document may be downloaded.
Stefano Taschini
has produced a beautiful Adobe Acrobat
PDF edition
of this document--thank you!
An English language translation of Albert Einstein's 1905 paper which
first derived the equivalence of mass and energy,
as published in the 1923 book
The Principle of Relativity.
Starting solely from the principle of relativity for
observers in uniform motion and the constancy of the
speed of light, Einstein employs an elegant kinematical
argument to deduce the most famous equation of twentieth
century physics: the equivalence of mass and energy.
In addition to
the Web edition,
ready-to-print
PostScript
and Adobe Acrobat PDF
files as well as
LaTeX source code
of this document are available.
In April 2013 I had the privilege of visiting CERN: the premier
particle physics laboratory in the world. This
photo essay shows some of the
underground wonders of the largest and most complicated
machine ever built by our species.
“Sustainable energy” is on the lips of politicians, media
figures, and others seeking to signal their virtue, but rarely do they
mention that a technology first demonstrated in 1951 has the ability,
any time we choose to adopt it, to entirely replace fossil fuels,
eliminate 100% of carbon emissions from energy production, and provide
power for all people on the globe at European per capita energy
consumption for at least the next ten thousand years. But it has a
scary name.
Why did such a long interval elapse between the appearance of life on
Earth and the emergence of complex, multicellular organisms? Perhaps
it had little to do with biology and everything to do with the
half-life of a radionuclide forged in the supernova whose debris gave
rise to us all.
It's sometimes said that special relativity has no consequences
in everyday life. Yet there's an effect of special relativity
which is immediately apparent at the glance of an eye and
observed (if not understood) since antiquity—the yellow
gleam of gold.
In 1963, Analog was a large format monthly magazine,
part slick and part pulp, with a cover price of 50 cents. Its
eclectic readership and contents attracted some curious
advertisements, such as this one from Leesona Moos Laboratories
for aerospace devices self-powered by Krypton 85 nuclear batteries.
How many Analog readers in 1963 assumed that in a
couple of years there'd be nuclear flashlight batteries for sale
at the hardware store? This one certainly did.
The longest continuously-running scientific experiment demonstrates that
even extremely viscous fluids will eventually flow as the liquids
they are. Do it yourself instructions are included.
To understand the news about negotiations with aspiring nuclear
powers, it's important to comprehend the technical fundamentals of
both paths to nuclear weapons. Here are the physics, chemistry,
and engineering behind the production of plutonium for nuclear
weapons applications, described for non-specialists.
A companion document discusses
uranium enrichment.
In the late 1950s and early '60s Project Pluto aimed at developing a nuclear powered
cruise missile which could fly three times the speed of sound at low altitude with
unlimited range and deliver nuclear devastation to multiple targets with pinpoint accuracy. It
was one of the most bizarre concepts of the age of unlimited nuclear optimism, and got
as far as ground testing a full scale flight weight propulsion system.
Explorations of radiation around the house and in the air
with a Geiger counter.
The books gotta balance! The mass of the inputs and outputs of the
human body, averaged over time, are equal. So where does the energy
the body consumes come from?
Due to the finite speed of light, observers in different locations or
moving with respect to one another may see events as occurring in
different orders—simultaneity depends upon your viewpoint.
You've heard the mission control recording of Apollo 11
landing on the Moon, but what did it sound like on board the
lunar module?
This document
demonstrates the relativity of simultaneity and lets you experience
the Eagle's touchdown from a lunar perspective, providing
an insight about Neil Armstrong's first radio transmission after
the landing.
Rocket engineering is complicated and demanding, but rocket
science is pretty straightforward. Explore the rocket equation,
which governs the operation of all rockets, and understand why it's so difficult
to get to orbit from the surface of the Earth and why multistage rockets
make sense.
Thermodynamics confronts special relativity in this
physics puzzle which explains why intergalactic spacecraft
will be streamlined just like in the movies.
A review/rant about Frank Tipler's 1994 book,
The Physics of Immortality.
The 1977 third (and most recent) edition of this book, compiled by
Samuel Glasstone and Philip J. Dolan and published by the
United States Department of Defense and Energy Research and
Development Administration (now Department of Energy) is the
definitive work on nuclear weapons effects. It is presented in a
hybrid form, with an XHTML table of contents which links
to PDF file containing scans of the pages of the book. An
interactive Web edition of the
nuclear bomb effects computer
circular slide rule which accompanied the 1962 edition of
the book is also available.
Relive the chilling calculations of the Cold War with this
interactive edition of the Nuclear Bomb Effects Computer published in
1962 by the United States Atomic Energy Commission. Enter the yield
and range, and the full suite of weapons effects will be displayed
just as on the original pocket slide rule. Nuclear weapons users who
prefer a physical slide rule, either out of nostalgia or an
appreciation for its ability to operate in post-apocalyptic
conditions, will find instructions for making their own.
In 1955 the giant mushrooms sprouted in abundance at the Nevada Test
Site north of Las Vegas. A total of fourteen fission devices were
detonated, with yields as high as 43 kilotons. The “Desert Rock VI”
exercise exposed 8000 troops to nuclear blasts to train them
for combat operations on the nuclear battlefield. This document was
distributed in January 1955 to those living near the Nevada Test Site
to prepare them for the 1955 test series. Illustrated with
delightful 1950s line art, it includes such sage advice as, “Your
best action is not to be worried about fall-out.” and
“We can expect many reports that ‘Geiger counters were going crazy
here today.’ Reports like this may worry people unnecessarily.
Don't let them bother you.”
Units Calculator is a Web interface to the
GNU
Units utility which allows conversion among thousands of
physical units, constants, and currencies. Units Calculator
may be used to perform complex scientific and engineering
calculations involving physical units and guards against
common errors due to dimensional incompatibility. Units
Calculator is 100% compatible with GNU Units, but as a Web
application can be used from any platform with a Web browser.
Currency exchange rates and precious metal prices are updated
daily. See the Introduction
for a tutorial, or proceed directly to the
Expert page, which contains
a click-to-copy table of common units.
To understand the news about negotiations with aspiring nuclear
powers, it's important to grasp the technical fundamentals of
both paths to nuclear weapons. This document describes the science
and engineering behind enriching natural uranium for use in civil
nuclear power reactors or weapons. A companion document discusses
plutonium production.
Fast interstellar travel will never be possible with any kind of
rocket, regardless of the energy source (be it chemical, nuclear, or
antimatter), due to the need to carry the rocket's
reaction mass on board. How can a person who coined the maxim
“Never invest in something that violates a conservation law” seriously
entertain the possibility of “propellantless propulsion”? This
brief document speculates on how a “Vacuum Propeller” might be
built which violates no law of physics.