SEE ALSO Time Travel (1949), Miller-Urey Experiment (1952), First Humans in Space (1961).
Given that our universe is both ancient and vast, the physicist Enrico Fermi asked in 1950, “Why have we not yet been contacted by an extraterrestrial civilization?”
1951
HeLa Cells • Clifford A. Pickover
George Otto Gey (1899–1970), Henrietta Lacks (1920–1951)
Medical researchers use human cells grown in the laboratory to study cell functions and to develop treatments for diseases. Such cells can be frozen and shared among different researchers. However, most cell lines divide only a limited number of times and then die. A breakthrough occurred in 1951, when American biologist George Gey cultured cells removed from a cancerous tumor of the cervix and created the first immortal human cells. These HeLa cells, named after the unwitting donor, Henrietta Lacks, continue to multiply to this day. Gey freely gave the cells to any scientists who requested them, and more than 60,000 scientific articles and 11,000 patents have since been published relating to research performed on the cells.
Author Rebecca Skloot writes, “If you could pile all HeLa cells ever grown onto a scale, they’d weigh more than 50 million metric tons—as much as a hundred Empire State Buildings. HeLa cells were vital for developing the polio vaccine; uncovered secrets of cancer, viruses, and the effects of the atom bomb; helped lead to important advances like in vitro fertilization, cloning, and gene mapping; and have been bought and sold by the billions.”
HeLa cells contain an active telomerase enzyme that continually repairs the ends of chromosomes that would normally become too damaged after multiple cell divisions to permit the cells to continue propagating. The genetic makeup of HeLa cells is far from ordinary, as they contain genes from human papillomavirus 18 and extra copies of several human chromosomes. Because the cells are so prolific and can even be spread on particles through the air, they have contaminated many other cell cultures in laboratories.
Lacks died at age 31 from the spread of her cancer, and her family did not learn of her “immortality” until decades later. The cells have since been launched into space to test the effects of low gravity and have been used in research topics ranging from AIDS to the testing of toxic substances.
SEE ALSO Causes of Cancer (1761), Cell Division (1855), Discovery of Viruses (1892), Chromosomal Theory of Inheritance (1902).
Scanning electron micrograph of HeLa cells dividing.
1952
Cellular Automata • Clifford A. Pickover
John von Neumann (1903–1957), Stanisław Marcin Ulam (1909–1984), John Horton Conway (b. 1937)
Cellular automata are a class of simple mathematical systems that can model a variety of physical processes with complex behaviors. Applications include the modeling of the spread of plant species, the propagation of animals such as barnacles, the oscillations of chemical reactions, and the spread of forest fires.
Some of the classic cellular automata consist of a grid of cells that can exist in two states, occupied or unoccupied. The occupancy of one cell is determined from a simple mathematical analysis of the occupancy of neighbor cells. Mathematicians define the rules, set up the game board, and let the game play itself out on a checkerboard world. Though the rules governing the creation of cellular automata are simple, the patterns they produce are very complicated and sometimes seem almost random, like a turbulent fluid flow or the output of a cryptographic system.
Early work in this area began with Stanislaw Ulam in the 1940s, when he modeled the growth of crystals using a simple lattice. Ulam suggested that mathematician John von Neumann use a similar approach to modeling self-replicating systems, such as robots that could build other robots, and around 1952, von Neumann created the first 2-D cellular automata, with 29 states per cell. Von Neumann proved mathematically that a particular pattern could make endless copies of itself within the given cellular universe.
The most famous two-state, two-dimensional cellular automaton is the Game of Life invented by John Conway, and popularized by Martin Gardner in Scientific American. Despite its simple rules, an amazing diversity of behaviors and forms are generated including gliders—that is, arrangements of cells that move themselves across their universe and can even interact to perform computations. In 2002, Stephen Wolfram published A New Kind of Science, which reinforced the idea that cellular automata can have significance in virtually all disciplines of science.
SEE ALSO Turing Machines (1936), Information Theory (1948), Chaos and the Butterfly Effect (1963), Fractals (1975).
Cone snail with cellular-automata patterns on its shell, resulting from that activation and inhibition of neighboring pigment cells. The pattern resembles the output of a one-dimensional cellular automaton, referred to as a Rule 30 automaton.
1952
Miller-Urey Experiment • Derek B. Lowe
Harold C. Urey (1893–1981), Stanley Miller (1930–2007)
For thousands of years, humankind has been trying to understand the origin of life. Biochemistry had to start somewhere, and presumably was much simpler at the beginning. But what did that beginning look like, and how did it get going? Could it happen again on other planets? How similar, then, would it be to what we know? None of these questions have a good answer yet.
A major step forward was taken in 1952 by American chemists Stanley Miller and Harold C. Urey. The idea was to take a believable “prebiotic” atmosphere and subject it to heat and the equivalent of lightning to see what compounds might form. They sealed an apparatus with water, methane, ammonia, and hydrogen; heated the water; fired electrical sparks across the vapor; and then cooled the system again to send the condensate back into the water layer. The process was set to cycle repeatedly, and it began to make colored compounds during the first day. After two weeks, over 10 percent of the methane had been turned into more complex compounds, and analysis of the mixture was startling. At least eleven of the twenty key amino acids were present, along with many simple carbohydrates and a variety of other molecules. Modern re-analysis of the sample has shown that all of the major amino acids were produced, some of them originally below the limits of detection.
Many similar experiments have been run since, using all sorts of different possible early atmospheres and conditions. Almost all of them produce rich brews of simple organic compounds, including many of what we would now call the building blocks of life. These arise through the formation of reactive molecules like hydrogen cyanide and formaldehyde from the original gases, which can go on to produce complex structures. The mixture of compounds in samples like the Murchison meteorite can be quite similar to those produced by these experiments, and spectroscopic studies have found many of these compounds around other stars as well as in comets and interstellar nebulae. The universe appears to be swimming in small biomolecules.
SEE ALSO Refuting Spontaneous Generation (1668), Fermi Paradox (1950), Darwin’s Theory of Natural Section (1859).
A re-creation at NASA of the Miller-Urey experiment. Note the dark mixture already forming in the chamber. Such brews of organic molecules seem to have many opportunities to form in the universe.
1953
DNA Structure • Clifford A. Pickover
Maurice Hugh Frederick Wilkins (1916–2004), Francis Harry Compton Crick (1916–2004), Rosalind Elsie Franklin (1920–1958), James Dewey Watson (b. 1928)
The British journalist Matt Ridley writes, “The double helix [structure of DNA] has been a shockingly fecund source of new understanding—about our bodies and minds, our past and future, our crimes and illnesses.” The DNA (deoxyribonucleic acid) molecule may be thought of as a “blueprint” that contains hereditary information. It also controls protein production and the complex development of cells starting from a fertilized egg. Just as an error in an architectural blueprint for a building might lead to home collapses or leaks, errors in the DNA, such as changes in the sequence caused by mutagens, might lead to disease. Thus, an understanding of the messages in the DNA
can lead to cures for disease, including the development of new drugs.
At a molecular level, DNA resembles a twisted ladder in which the different rungs of the ladder (referred to as bases) represent a code for protein production. DNA is organized into structures called chromosomes, and the human genome has approximately three billion DNA base pairs in the 23 chromosomes of each sperm cell or egg. Generally speaking, a gene is a sequence of DNA that contains a “chunk” of information that, for example, specifies a particular protein.
In 1953, molecular biologists James Watson and Francis Crick discovered the double helical structure of DNA using molecular-modeling methods, along with X-ray and other data from scientists such as Maurice Wilkins and Rosalind Franklin. Today, with recombinant DNA technology, genetically modified organisms can be created by inserting new DNA sequences that force the organism to create desirable products, such as insulin to be used by humans. Forensic detectives can study DNA left at crime scenes to help identify potential criminals.
In December 1961, the New York Times reported on breakthroughs in understanding of the genetic code in DNA by explaining that “the science of biology has reached a new frontier,” leading to “a revolution far greater in its potential significance than the atomic or hydrogen bomb.”
SEE ALSO Mendel’s Genetics (1865), Chromosomal Theory of Inheritance (1902), Epigenetics (1983), Polymerase Chain Reaction (1983), Human Genome Project (2003), Gene Therapy (2016).
Molecular model of a portion of a DNA strand.
1955
Atomic Clocks • Clifford A. Pickover
Louis Essen (1908–1997)
Clocks have become more accurate through the centuries. Early mechanical clocks, such as the fourteenth-century Dover Castle clock, varied by several minutes each day. When pendulum clocks came into general use in the 1600s, clocks became accurate enough to record minutes as well as hours. In the 1900s, vibrating quartz crystals were accurate to fractions of a second per day. In the 1980s, cesium atom clocks lost less than a second in 3,000 years, and, in 2009, an atomic clock known as NIST-F1—a cesium fountain atomic clock—was accurate to a second in 60 million years!
Atomic clocks are accurate because they involve the counting of periodic events involving two different energy states of an atom. Identical atoms of the same isotope (atoms having the same number of nucleons) are the same everywhere; thus, clocks can be built and run independently to measure the same time intervals between events. One common type of atomic clock is the cesium clock, in which a microwave frequency is found that causes the atoms to make a transition from one energy state to another. The cesium atoms begin to fluoresce at a natural resonance frequency of the cesium atom (9,192,631,770 Hz, or cycles per second), which is the frequency used to define the second. Measurements from many cesium clocks throughout the world are combined and averaged to define an international time scale.
One important use of atomic clocks is exemplified by the GPS (global positioning system). This satellite-based system enables users to determine their positions on the ground. To ensure accuracy, the satellites must send out accurately timed radio pulses, which receiving devices need to determine their positions.
English physicist Louis Essen created the first accurate atomic clock in 1955, based on energy transitions of the cesium atom. Clocks based on other atoms and methods are continually being researched in labs worldwide in order to increase accuracy and decrease cost.
SEE ALSO Sundial (c. 3000 BCE) Time Travel (1949), Radiocarbon Dating (1949).
In 2004, scientists at the National Institute of Standards and Technology (NIST) demonstrated a tiny atomic clock, the inner workings of which were about the size of a grain of rice. The clock included a laser and a cell containing a vapor of cesium atoms.
1955
Birth-Control Pill • Clifford A. Pickover
Margaret Higgins Sanger Slee (1879–1966), Pope Paul VI (Giovanni Montini; 1897–1978), Gregory Pincus (1903–1967), Frank Benjamin Colton (1923–2003), Carl Djerassi (1923–2015)
Oral contraceptives, or birth-control pills, were among the most socially significant medical advances of the twentieth century. Supplied with an easy and effective means to prevent pregnancies, more women graduated from college and entered the work force. In the 1930s, researchers had determined that high concentrations of the hormone progesterone, which is normally present during pregnancy, also tricks a nonpregnant body into behaving as if it were pregnant and thus prevent the monthly release of an egg. In the early 1950s, American chemists Carl Djerassi and Frank Colton, working independently, discovered ways to manufacture chemical compounds that mimicked natural progesterone. American biologist Gregory Pincus confirmed that shots of progesterone prevent egg release from the ovary of mammals.
Margaret Sanger, a famous advocate for birth control, helped Pincus obtain the necessary funding to develop a hormonal birth-control pill for humans. Pincus selected Colton’s formula, and in 1955 he and colleagues announced clinical-trial results demonstrating the efficacy of the pill. In addition to inhibiting ovulation, contraception is enhanced by changes in the cervical mucus that inhibit sperm entrance to the uterus, and by changes in the lining of the uterus that inhibit egg implantation. U.S. regulators approved the pill for contraception in 1960, and the Searle drug company named it Enovid.
The original formulation, which also contained the hormone estrogen, had some undesirable side effects; however, modern formulations contain much reduced doses of hormones and have been shown to decrease ovarian, endometrial, and colon cancers. Generally speaking, women smokers who take the pill have an increased risk of heart attacks or strokes. Today, different hormonal formulations are available (including pills only with progestin, a type of progesterone) that supply hormone doses that are constant or that change from one week to the next.
In 1968, Pope Paul VI condemned artificial birth control, including the pill. Although adoption of the pill was rapid in the United States, distribution of contraceptives to unmarried women was not legal in Connecticut until 1972!
SEE ALSO Discovery of Sperm (1678), Cell Division (1855), Chromosomal Theory of Inheritance (1902).
A psychedelic portrait of a “post-pill paradise” in a new era for women. In the 1960s, many women achieved greater personal control over contraception, which contributed to the sexual revolution.
1955
Placebo Effect • Clifford A. Pickover
Henry Knowles Beecher (1904–1976)
Medical experts Arthur and Elaine Shapiro write, “The panorama of treatment since antiquity provides ample support for the conviction that, until recently, the history of medical treatment is essentially the history of the placebo effect. . . . For example, the first three editions of the London Pharmacopoeia published in the seventeenth century included such useless drugs as usnea (moss from the skull of victims of violent death) and Vigo’s plaster ([including] viper’s flesh, live frogs, and worms).”
Today, the term placebo often refers to a fake “drug” (such as a sugar pill) or a sham surgery (such as cutting the skin but going no deeper to treat a condition) that nevertheless produces a perceived or actual improvement in those patients who believe the medical intervention will turn out to be effective. The placebo effect suggests the importance of patient expectations and the role of the brain in physical health, particularly for subjective outcomes such as levels of pain.
In 1955, American physician Henry Beecher documented the famous case of soldiers in World War II who experienced significant pain relief when given injections of saline solutions when the morphine supplies were not available. One mechanism of the placebo effect appears to involve endogenous opioids—natural painkillers produced by the brain—as well as the activity of the neurotransmitter dopamine.
In one study, mice given a compound that suppresses the immune system along with a sweet-tasting chemical became conditioned over time, so that immune suppression occurred when given only the sweetener. Thus, conditioning may play a rol
e in human placebos. A placebo administered to people as a stimulant can increase blood pressure, and alcohol placebos can cause intoxication. Color and size of pills often make a significant difference in perceived effectiveness. The placebo effect also tends to work to varying degrees depending on the society and country tested. A nocebo response refers to a negative response to a placebo, such as the feeling of pain when the patient believes that the inert drug may have unpleasant side effects.
SEE ALSO Scientific Method (1620), The Principles of Psychology (1890), Psychoanalysis (1899), Randomized Controlled Trials (1948), Classical Conditioning (1903), Theory of Mind (1978).
Because a person’s expectations influence the placebo effect, the pill color, size, and shape all affect the placebo response. Red pills work better as stimulants, while “cool”-colored pills work better as depressants. Capsules are often perceived to be particularly effective.
1955
Ribosomes • Michael C. Gerald with Gloria E. Gerald
Albert Claude (1898–1983), George Palade (1912–2008)
The combination of cell fractionation and electron microscopy opened a new frontier in biology, making possible the visualization of the cell’s interior contents and determining their biological functions. In 1930, the Belgian biologist Albert Claude, at Rockefeller University, devised the process of cell fractionation, in which a cell is ground up to release its contents and centrifuged at different speeds to separate the contents according to weight. Claude’s cell fractionation process was refined in 1955 by his student George Palade, a Romanian-born American, who used the electron microscope to study these cell fractions. Palade was first to identify and describe “small granules,” which were given the name ribosome in 1958, and found to be the site of protein synthesis within the cell. Claude and Palade (the latter often called the father of modern cell biology and the most influential cell biologist ever) were co-recipients of the 1974 Nobel Prize.
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