On Tuesday night, I headed to the Scintillating Symphony Space, on the Upper West Side of Manhattan, for the latest Secret Science Club North lecture, featuring astrophysicist Dr Jason Kalirai of the Space Telescope Science Institute and NASA's James Webb Space Telescope project. Dr Kalirai's lecture was a commemoration of both the 100th anniversary of the publication of Einstein's Theory of General Relativity and the 20th anniversary of the launching of the Hubble Space Telescope.
Dr Kalirai began his talk by asking, what is our place in the universe? His quick answer was that it depends on when an individual asked that question. He followed up with a quick overview of the history of astronomy, beginning with the ancient Egyptians, who aligned their pyramids with the circumpolar stars and used astronomical observation to determine the times of planting and harvest. He then moved on to a quick discussion of Greek philosophers and mathematicians, such as Pythagoras and Aristotle, who believed that earthly standards could be applied to celestial bodies. He singled out Hipparchus as an avid mapper of the changing positions of celestial bodies, and Ptolemy, whose geocentric model of the universe held sway for fifteen-hundred years, until Copernicus publicized his heliocentric model. Copernicus' model was corroborated by Galileo's discovery of moons orbiting Jupiter. By shifting the center of the universe away from the Earth, our position in the universe was considerably diminished.
In 1920, the Great Debate between Harlow Shapley and Heber Curtis regarding the nature of spiral nebulae took place- Shapely believed that spiral nebulae were formations within the Milky Way, which comprised the totality of the universe, while Curtis believed that spiral nebulae were additional galaxies outside the Milky Way, which would necessitate a vastly larger universe and a Milky Way which was merely one galaxy among many. Edwin Hubble was able to determine that spiral nebulae lay outside the Milky Way by observing a certain type of star in several nebulae, indicating that they lay outside our galaxy.
The next great leap forward in astronomy would require a telescope in space, outside of Earth's atmosphere- in 1946, Lyman Spitzer wrote a paper titled, "Astronomical Advantages of an Extra-Terrestrial Observatory". Within fifty years, the Hubble space telescope was sent into orbit, science fiction became science fact. Dr Kalirai then proceeded to show us some wonderful images from Hubble depicting the life of stars such as the explosion of a star and the end of a supernova. Stars are largely composed of hydrogen and helium- the heavier elements were formed in the core of stars and are disseminated throughout the universe by the explosion of older stars. The Earth formed in a region 'polluted' by supernovae, and we are all made of stars. He also showed lovely images of the Hubble Deep Field, which gave us a glimpse of the thousands and thousands of galaxies in the universe.
The talk then shifted to the topic of Einstein's Theory of General Relativity. In 1905, Albert Einstein published his Special Theory of Relativity. The two main postulates of Special Relativity are that the laws of physics are independent of a frame of reference and that light has a constant speed independent of the direction and motion of its source. According to Special Relativity, time and space are one (physicists speak of spacetime), and that time slows down for objects in motion (time dilation). Special Relativity was thought to apply only to systems in which there is no acceleration, in which speed is constant.
In 1915, Einstein published his General Theory of Relativity, which was a response to Newton's Law of Universal Gravitation- Einstein was not satisfied with Newton's equations, which approximated reality. He desired a more elegant explanation for gravity because Newton's laws break down at high speeds in high gravitational fields. Einstein noted that mass bends space and time, with larger masses distorting spacetime more than smaller masses. Gravity is the interaction of objects in the warped spacetime.
Dr Kalirai then noted that there are five basic pieces of evidence that backed General Relativity. First, the gravity of the sun bends light from objects behind it, an effect observed by astronomer Arthur Eddington during a solar eclipse in 1919, during which it was observed that stars behind the sun could be seen. The second piece of evidence is the observed precession (rotation) of Mercury, which deviates from the precession predicted by Newtonian models. The third piece of evidence supporting General Relativity is gravitational lensing- the bending of light from distant sources by intervening mass (the subject of the first Secret Science Club North lecture was the use of gravitational lensing to infer the presence of masses of dark matter). The fourth piece of evidence in support of General Relativity is stellar life cycles and black holes. Small stars, approximately the size of our sun, will form white dwarfs at the end of their 'lifespans'- these stars expand to form red giants, then lose their outer layers, with the core remaining, a small star remnant about the size of the Earth with a mass approximating that of our sun. Stars with higher mass will end up as pulsars, superdense neutron stars which emit beams of radiation that appear to pulse due to rotation. The largest stars will collapse to form black holes, which are so dense that their escape velocity exceeds the speed of light, so that not even light can escape their gravitational forces. The fifth piece of evidence supporting General Relativity is dark matter and dark energy- Einstein believed in a static universe and postulated a cosmological constant in order to 'hold back gravity' in order to allow his equations to account for it. When Edwin Hubble discovered that the universe is expanding, Einstein is reported to have labeled the cosmological constant his 'greatest blunder'. Dark energy is believed to compose 70% of the universe and is postulated to cause the acceleration of the expansion of the universe.
Dr Kalirai then tied the two major threads of the lecture together, talking about the need for improved telescopes to improve our observation of the universe in order to increase our knowledge. He talked about the James Webb Space Telescope project, which involves sending a telescope with a mirror array the size of a tennis court to a position a million miles away from Earth. The resolution provided by the telescope will exceed that of the Hubble. He also brought up the Wide Field Infrared Survey Telescope, which is supposed to explore the nature of both dark energy and exoplanets. Besides the 100th anniversary of General Relativity and the 25th anniversary of the Hubble, it's the 20th anniversary of the discovery of the first exoplanet. He noted that the Hubble Telescope was limited by its size- he likened its use to peering through a drinking straw. The Wide Field Infrared Survey Telescope will be able to observe a field one hundred times that provided by the Hubble. It is hoped that the WFIRST will allow us to transition from finding exoplanets to learning about exoplanets- using spectra to determine the composition of planetary atmospheres. Another desired result of the use of these telescopes is to search for the first light of the first stars.
All told, Dr Kalirai's lecture was a slam-dunk... he really tied together an introduction to General Relativity and research projects which will expand on our knowledge of astrophysics, the experimental data which corroborated Einstein's theoretical framework. The audience skewed both older and younger than the typical Secret Science Club crowd, with many senior citizens and a sprinkling of children. Only a handful of the Brooklyn regulars were on hand. The main Symphony Space auditorium was about 80% full, and the Q&A session was lively. After the lecture, I had a nice, brief discussion with Dr Kalirai about the use of these telescopes to give us a better idea of the larger structure of the universe- the clusters of galaxies and the tendrils of dark matter which trail from galaxy to galaxy. Dr Kalirai indicated that much of our theories about this structure were extrapolated from the Hubble Deep Field images- we're basically peering through the soda straw and making predictions about that. Any widening of the field will widen our knowledge.
Once again, the Secret Science Club delivered a great program- Dr Kalirai was an engaging, charismatic speaker, a true populizer of science, able to convey complex astrophysical information to a lay audience. Here is a video of him delivering a lecture on our place in the universe:
The lecture begins about ten minutes into the embedded video... pour yourself a nice cold beverage and approximate that Secret Science Club vibe.