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Maria Mitchell (1818-1889)
Astronomer
Growing up in the whaling town of Nantucket, Massachusetts Mitchell grew up learning about the stars and navigation. She could rate the chronometers for whaling ships and plot the movements of the planets.
In 1847, her discovery of a comet invisible to the naked eye won her international fame and a medal from the king of Denmark. After that, she went to work for the U.S. Nautical Almanac Office to compute ephemeredes of the planet Venus.
When Vassar College was founded in 1865, she joined the faculty as a professor of astronomy and director of the college observatory. She became the first woman elected to the American Academy of Arts and Sciences, and founded the Association for the Advancement of Women in 1873, chairing the Committee on Women’s Work in Science until her death.
Women in Science: Rosalind Franklin (1920-1958)
Biophysicist
Franklin went to Newnham College, Cambridge and graduated in 1941, but was only awarded a degree titular, as women were not entitled to degrees from Cambridge at the time; in 1945 Franklin received her PhD from Cambridge University.
Franklin’s x-ray diffraction photographs led to the understanding of the structure of deoxyribonucleic acid (DNA). Her colleague, Maurice Wilkins, without obtaining her permission, made available to Watson and Crick her then unpublished x-ray diffraction pattern of the B form of DNA, which was crucial evidence for the helical structure of DNA.
Aside from her x-ray work with DNA, she also work with x-rays of lipids and proteins, and also did x-ray crystallography with the tobacco mosaic virus.
Mae Carol Jemison (1956-Present)
Chemical Engineer, Physician, Astronaut
She graduated from Stanford University in 1977 with a B.S. in chemical engineering and a medical degree from Cornell University Medical School in 1981.
She joined NASA’s astronaut training program in 1986 and was the first African American woman to travel to space in the Space Shuttle Endeavor on September 12, 1992. Jemison conducted experiments in life sciences and material sciences and was co-investigator in bone cell research experiment the space laboratory module. She developed and participated in research projects with the NIH on hepatitis B vaccine, schistosomiasis and rabies. Dr. Jemison also speaks Russian, Japanese and Swahili.
“We need science education to produce scientists, but we need it equally to create literacy in the public. Man has a fundamental urge to comprehend the world about him, and science gives today the only world picture which we can consider as valid. It gives an understanding of the inside of the atom and of the whole universe, or the peculiar properties of the chemical substances and of the manner in which genes duplicate in biology. An educated layman can, of course, not contribute to science, but can enjoy and participate in many scientific discoveries which as constantly made. Such participation was quite common in the 19th century, but has unhappily declined. Literacy in science will enrich a person’s life.”
― Hans Bethe
Hans Albrecht Bethe
Hans Bethe with Boyce McDaniel in the tunnel of the Cornell Electron Storage Ring, 1968. ©Russ Hamilton/CU
She studied at Cambridge as an undergraduate but was not awarded a degree because the university didn’t grant degrees to women at that time. After meeting Harlow Shapley, the Director of the Harvard College Observatory, who had just begun began a graduate program in astronomy, she left England for the United States in 1923.
Payne-Gaposchkin became the first person to earn a Ph.D. in astronomy from Radcliffe (now part of Harvard). By studying the spectra of stars, Payne-Gaposchkin determined that hydrogen and helium were the most abundant elements in stars. She was the first woman to receive the rand of full professor at Harvard and also the first woman chairperson of a department at Harvard University.
“Let’s grant that the stars are scattered through space, hither and yon. But how hither, and how yon? To the unaided eye the brightest stars are more than a hundred times brighter than the dimmest. So the dim ones are obviously a hundred times farther away from Earth, aren’t they?
Nope.
That simple argument boldly assumes that all stars are intrinsically equally luminous, automatically making the near ones brighter than the far ones. Stars, however, come in a staggering range of luminosities, spanning ten orders of magnitude ten powers of ten. So the brightest stars are not necessarily the ones closest to Earth. In fact, most of the stars you see in the night sky are of the highly luminous variety, and they lie extraordinarily far away.
If most of the stars we see are highly luminous, then surely those stars are common throughout the galaxy.
Nope again.
High-luminosity stars are the rarest. In any given volume of space, they’re outnumbered by the low-luminosity stars a thousand to one. It’s the prodigious energy output of high-luminosity stars that enables you to see them across such large volumes of space.”
― Neil deGrasse Tyson, Death by Black Hole: And Other Cosmic Quandaries
When spacecraft first transmitted the images of the moon’s far side to Earth, we saw the lunar farside lacks the large dark areas called maria, or seas. Why?
Composite image of the lunar nearside taken by the Lunar Reconnaissance Orbiter in June 2009. Note the presence of dark areas – called maria by astronomers – on this side of the moon. Image via NASA
Composite image of the lunar farside – the side that always faces away from Earth – taken by the Lunar Reconnaissance Orbiter in June 2009. Note the absence of large dark areas. Image via NASA
The dark maria or seas – large flat areas of basalt on the moon’s near side – are sometimes referred to as the man in the moon. No such features exist on far side of the moon. Why are there dark maria on the moon’s near side, but not far side? Penn State astrophysicists think they have the answer. They believe that the absence of maria, which is due to a difference in crustal thickness between the near side of the moon and the far side, is a consequence of how the moon originally formed. The researchers reported their results in the June 9 Astrophysical Journal Letters.
Jason Wright, assistant professor of astrophysics at Penn State, said:
I remember the first time I saw a globe of the moon as a boy, being struck by how different the farside looks. It was all mountains and craters. Where were the maria? It turns out it’s been a mystery since the 1950s.
This mystery – called the Lunar Farside Highlands Problem by astronomers – dates back to 1959, when the Soviet spacecraft Luna 3 transmitted the first images of the dark side of the moon back to Earth. Researchers immediately noticed that fewer maria on the portion of the moon that always faces away from Earth.
The Penn State astronomers looked back to the formation of the moon for their ideas on why one side of the moon has maria, and the other doesn’t. The general consensus on the moon’s origin is that it probably formed shortly after the Earth and was the result of a Mars-sized object hitting Earth with a glancing, but devastating impact. This Giant Impact Hypothesis suggests that the outer layers of the Earth and the object were flung into space and eventually formed the moon.
Shortly after the giant impact, the Earth and the moon were very hot, said researchers. The Earth and the impact object did not just melt; parts of them vaporized, creating a disk of rock, magma and vapor around the Earth.
The geometry was similar to the rocky exoplanets recently discovered very close to their stars, said Wright. The moon was 10 to 20 times closer to Earth than it is now, and the researchers found that it quickly assumed a tidally locked position with the rotation time of the moon equal to the orbital period of the moon around the Earth. The same real estate on the moon has probably always faced the Earth ever since. Tidal locking is a product of the gravity of both objects.
The moon, being much smaller than Earth cooled more quickly. Because the Earth and the moon were tidally locked from the beginning, the still hot Earth – more than 2500 degrees Celsius – radiated towards the near side of the moon. The far side, away from the boiling Earth, slowly cooled, while the Earth-facing side was kept molten creating a temperature gradient between the two halves.
This gradient was important for crustal formation on the moon. The moon’s crust has high concentrations of aluminum and calcium, elements that are very hard to vaporize.
Aluminum and calcium would have preferentially condensed in the atmosphere of the cold side of the moon because the nearside was still too hot. Thousands to millions of years later, these elements combined with silicates in the moon’s mantle to form plagioclase feldspars, which eventually moved to the surface and formed the moon’s crust. The farside crust had more of these minerals and is thicker.
The moon has now completely cooled and is not molten below the surface. Earlier in its history, large meteoroids struck the nearside of the moon and punched through the crust, releasing the vast lakes of basaltic lava that formed the nearside maria that make up the characteristic man in the moon features.
Meanwhile, when meteoroids struck the farside of the moon, in most cases the crust was too thick and no magmatic basalt welled up, creating the dark side of the moon with valleys, craters and highlands, but almost no maria.
Had we never seen the stars, and the sun, and the heaven, none of the words which we have spoken about the universe would ever be uttered. But now the sight of day and night, and the months and the revolutions of the years, have created number, and have given us a conception of time, and the power of enquiring about the nature of the universe; and from this source we have derived philosophy, than which no greater good ever was or will be given by gods to mortal man.
-Plato
One thing I have learned in a long life: that all our science, measured against reality, is primitive and childlike-
and yet it is the most precious thing we have.
-Albert Einstein
