We are all going to miss Stephen Hawking. His incredible intellect, and his even more remarkable determination to make something of himself despite a terrible affliction, has been a universal inspiration all over the world. Stephen Hawking was the individual equivalent of the Apollo lunar program. He raised the bar when almost everyone else we see nowadays is lowering it. He succeeded against all the odds.
Now would be a good time to watch (or rewatch) five extraordinary documentaries and films about Stephen Hawking and his ideas.
Fermilab is a name well known to all physicists. When I was an astrophysics undergraduate student at Iowa State University in Ames, Iowa in the mid-to-late 1970s, I remember that several members of our large high energy physics group made frequent trips to Fermilab, including Bill Kernan and Alex Firestone. At the time, it was the best place in the world to do high energy physics. What is high energy physics? Basically, it is the creation and study of new and normally unseen elementary particles formed by colliding subatomic particles into one another at very high velocities (kinetic energies).
On Sunday, March 4, a group of us from the Iowa County Astronomers met up at Fermilab for an afternoon tour of this amazing facility. We were all grateful that John Heasley had organized the tour, and that Lynda Schweikert photo-documented our visit.
Our afternoon began with an engaging talk by Jim Annis, Senior Scientist with the Experimental Astrophysics Group: “Kilonova-2017: The birth of multi-messenger astronomy using gravitational waves, x-rays, optical, infrared and radio waves to see and hear neutron stars”. Here he is showing a computer simulation of an orbiting pair of neutron stars coalescing, an event first observed by the LIGO and Virgo gravitational wave detectors on 17 August 2017 (GW170817), and subsequently studied across the entire electromagnetic spectrum.
One of the amazing factinos I remember from his talk: even though neutrinos were not directly detected from the GW170817 event, the matter in colliding neutron stars is so dense that neutrinos push material outwards in what is called a neutrino wind. Yes, these are the same neutrinos that could pass through a light year of solid lead and only have a 50% chance of being absorbed or deflected, and pass through your body at the rate of 100 trillion every second with nary a notice.
Even though CERN has now eclipsed Fermilab as the world’s highest-energy particle physics laboratory, Fermilab is making a new name for itself as the world’s premier facility for producing and studying neutrinos. This is a fitting tribute to Enrico Fermi (1901-1954)—after whom Fermilab is named—as Fermi coined (or at least popularized) the term “neutrino” for these elusive particles in July 1932.
Basic research is so important to the advancement of human knowledge, and funding it generally requires public/government funding because practical benefits are often years or decades away; therefore such work is seldom taken up by businesses interested in short term profit. However, as our tour guide informed us, the equipment and technology that has to be developed to do the basic research often leads to practical applications in other fields on a much shorter time frame.
Thoughts Inspired by Leon Lederman: A Footnote
I had the great privilege in October 2004 of attending a talk given by Leon Lederman (1922-), winner of the 1988 Nobel Prize in Physics and director emeritus of Fermilab. I listened intently and took a lot of notes, but what I remember best besides his charm and engaging speaking style was his idea for restructuring high school science education. The growing scientific illiteracy in American society, and the growth of dogmatic religious doctrine, is alarming. Lederman advocates that all U.S. high school students should be required to take a conceptual physics & astronomy course in 9th grade, chemistry in 10th grade, and biology in 11th grade. Then, in 12th grade, students with a strong interest in science would take one or more advanced science courses.
Teaching conceptual physics (and astronomy) first would better develop scientific thinking skills and lay a better groundwork for chemistry, which in turn would lay a better groundwork for biology. Whether or not a student chooses a career in science, our future prosperity as a society depends, in large part, on citizens being well-informed about science & technology matters that affect all of our lives. We also need to be well-equipped to assimilate new information as it comes along.
It is in this context that I was delighted to read Leon Lederman’s commentary, “Science education and the future of humankind” as the last article in the first biweekly issue of Science News (April 21, 2008). He writes:
Can we modify our educational system so that all high school graduates emerge with a science way of thinking? Let me try to be more specific. Consider Galileo’s great discovery (immortalized as Newton’s First Law): “An isolated body will continue its state of motion forever.” What could be more counterintuitive? The creative act was to realize that our experience is irrelevant because in our normal experience, objects are never isolated—balls stop rolling, horses must pull carts to continue the motion. However, Galileo’s deeper intuition suspected simplicity in the law governing moving bodies, and his insightful surmise was that if one could isolate the body, it would indeed continue moving forever. Galileo and his followers for the past 400 years have demonstrated how scientists must construct new intuitions in order to know how the world works.
I’d like to take Lederman’s comments one step further. Whether it be science, politics, economics, philosophy, or religion, we must realize that most ignorance is learned. We all have blind spots you could drive a truck through. Our perceptions masquerade as truth but sometimes upon closer inspection prove to be faulty. Therefore, we must learn to question everything, accepting only those tenets that survive careful, ongoing scrutiny. We must learn to reject, unlearn if you will, old intuitions and beliefs that are harmful to others or that have outlived their usefulness in the world. We must develop new intuitions, even though at first they might seem counterintuitive, that are well supported by facts and that emphasize the greater good. We must, all of us, construct new intuitions in order to make our world a better place—for everyone.
The following excerpts are from the 1911 and 1925 editions of A Text-Book of Physics by Louis Bevier Spinney, Professor of Physics and Illuminating Engineering at Iowa State College (now Iowa State University) in Ames, Iowa.
From the 1911 edition…
516. The intensity of illumination of any surface is defined as the ratio of the light received by the surface to the area of the surface upon which the light falls. A unit of intensity which is oftentimes employed is known as the foot candle, and is defined as the intensity of illumination which would be present upon a screen placed at a distance of one foot from a standard candle. The meter candle is a unit of intensity which is employed to some extent.
The table below gives a number of values of illumination such as are commonly observed, the intensity of illumination being expressed in foot candles.
Suitable for drafting table . . . . . 5 to 10
Suitable for library table . . . . . . 3 to 4
Suitable for reading table . . . . . . 1 to 2
Required for street lighting . . . . . 0.05 to 0.60
Moonlight (full moon) . . . . . . . 0.025 to 0.03
And from the 1925 edition…
532. The eye has a remarkable power of adaptation. In strong light the pupil contracts and in weak light expands, so that we are able to use our eyes throughout a range of illumination which is really quite astonishing. However, the continued use of the eyes under conditions of unfavorable illumination causes discomfort, fatigue, and even permanent injury. Experiment and experience show that eye comfort, efficiency, and health considerations demand for each kind of eye work a certain minimum illumination. Some of these illumination values taken from tables recently compiled are given below.
Streets . . . . . . . . . . . . . . 1/20 to 1/4
Living rooms; Halls and passageways . . 1 to 2
Auditoriums; Stairways and exits;
Machine shops, rough work . . . . . . 2 to 5
Classrooms; Laboratories; Offices;
Libraries; Machine shops, close work . . 5 to 10
Engraving; Fine repairing work; Drafting;
Sewing and weaving, dark goods . . . . 10 to 20
By comparing the 1911 and 1925 data with the illumination levels recommended today by IESNA, we can see that recommended light levels for streetlighting have increased anywhere from 40% to 380% since 1925. A cynic might say that we need more light than our ancestors did to see well at night. As you may have noticed, light levels have been steadily creeping upward, everywhere, over the last few decades.
Recommended Illumination Levels for Streetlighting
Year Minimum Average Maximum
1911 0.05 ??? 0.60
1925 0.05 0.25 ???
1996 0.07 1.20 ???
Have you ever noticed how well you can see at night when the full moon is lighting the ground? The full moon provides surprisingly adequate non-glaring and uniform illumination at just 0.03 footcandles! For inspiration, take a look at the following text from an Ames, Iowa city ordinance, dated July 8, 1895:
“The said grantees shall keep said lamps in good condition and repair, and have the same lighted every night in the year from dark until midnight, and from 5:00 a.m. until daylight, except such moonlight nights or fractions of the same as are not obscured by clouds, and as afford sufficient natural light to light the streets of said city.”
This was originally published as IDA Information Sheet 114 in November 1996, and authored by David Oesper.
A vacuum is not nothing. It is only a region of three-dimensional space that is entirely devoid of matter, entirely devoid of particles.
The best laboratory vacuum contains about 25 particles (molecules, atoms) per cubic centimeter (cm3).
The atmosphere on the surface of the Moon (if you can call it that) contains a lot more particles than the best laboratory vacuum: about 40,000 particles per cm3. This extremely tenuous lunar atmosphere is mostly made up of the “noble” gases argon, helium, and neon.
The vacuum of interplanetary space contains about 11 particles per cm3.
The vacuum of interstellar space contains about 1 particle per cm3.
The vacuum of intergalactic space contains about 10-6 particles per cm3. That’s just 10 particles per cubic meter of space.
But what if we could remove all of the particles in a parcel of space? And somehow shield that empty parcel of space from any external electromagnetic fields? What would we have then?
It appears that even completely empty space has some inherent energy associated with it. The vacuum is constantly “seething” with electromagnetic waves of all possible wavelengths, popping into and out of existence on unimaginably short time scales—allowed by Heisenberg’s energy-time uncertainly principle. These “quantum flourishes” may be a intrinsic property of space—as is dark energy. Dark matter, on the other hand, is some weird form of matter that exists within space, exerting gravitational influence but not interacting with normal matter or electromagnetic waves in any other way.
Is there any evidence of this vacuum energy, or is it all theoretical? There are at least three phenomena that point to the intrinsic energy of empty space. (1) The Casimir effect; (2) Spontaneous emission; and (3) The Lamb shift.
The Casimir effect
Take two uncharged conductive plates and put them very close to each other, just a few nanometers apart. Only the shortest wavelengths will be able to exist between the plates, but all wavelengths will exist on the other side of the two plates. Under normal circumstances, this will cause a net force or pressure that pushes the two plates towards one another.
An example of spontaneous emission is an electron transitioning from an excited state to the ground state, emitting a photon. What causes this transition to occur when it does?
The Lamb shift
The Lamb shift is a tiny shift in the energy levels of electrons in hydrogen and other atoms that can’t be explained without considering the interaction of the atom with “empty” space.