We are confused about how old the Universe is. Until recently, astronomers estimated that the Big Bang occurred between 12 and 14 billion years ago. Astronomers can place a lower limit to the age of the universe by studying globular clusters. Globular clusters are a dense collection of roughly a million stars. Stellar densities near the center of the globular cluster are enormous. If we lived near the center of one, there would be several hundred thousand stars closer to us than Proxima Centauri, the star nearest to the Sun.
Really, we are confused about how fast the Universe is expanding today, measured by how fast distant objects are moving away from us, which directly determines how old the Universe is. This conundrum arises from a mismatch between two rigorously vetted approaches to measuring the expansion rate of the Universe. One uses the baby picture of the Universe, the cosmic microwave background. This relic radiation, imprinted on the cosmos shortly after the Big Bang, provides a snapshot of the Universe’s infancy, shedding light on its earliest moments. The other approach relies on constructing a “cosmic distance ladder” with pulsating stars and supernovae in the nearby universe. These measurements have led to a fascinating puzzle, as these methods yield different results, sparking the so-called “Hubble tension.” Our presenter’s research investigates possible solutions to this tension in the form of new, undiscovered physics. For our April General Meeting, she explored this debate on the age of the Universe, journeying through cosmic time and drawing a through line across the evolution of the Universe. Our speaker wasTanvi Karwal is a theoretical cosmologist working at the University of Chicago. Dr. Karwal earned her PhD at Johns Hopkins and spent time doing research as a postdoc at UPenn. She thinks about everything larger than a galaxy but makes an exception for cake. She thinks about cake a lot. She also thinks about how fast the Universe is expanding, about dark energy, dark matter and how it all comes together to form our Universe today. Tanvi is originally from India, has strong opinions on desserts, and likes to illustrate.
May ’25 — Rick’s Picks
Transient Events That Can Give Us a Good Enough Reason to Get Outside and Do a Little Observing All month: the planets continue their exodus from the evening sky this month. Uranus is now lost in the solar glare – it will reach conjunction on May 17 and return as a...
Astronomy Fundamentals: A Look at the History of Alvan Clark Telescopes
In the 19th century, Alvan Graham Clark was one of the premier lens makers for telescopes. His craftsmanship was sought after and many observatories in the late 19th and early 20th centuries were built to house his refractor telescopes. In fact, smaller Alvan Clark...
April ’25 – Rick’s Picks
Transient Events That Can Give Us a Good Enough Reason to Get Outside and Do a Little ObservingAll month: the solar system balances morning and evening targets this month as Mercury, Venus, Saturn, and Neptune move into the predawn sky, while Mars, Jupiter, and Uranus...
Astronomy Fundamentals: What We Can Learn from Impact Craters
Impact craters can be found throughout the solar system. NASA scientists use impact craters and volcanic activity to learn about the process throughout the solar system. By studying craters on Earth, scientists gain knowledge of volcanic landform formation and...