Dark matter - what we're really made of | Michelle Thaller | TEDxBinghamtonUniversity
TEDx Talks・19 minutes read
The Milky Way galaxy contains around 500 billion stars and spans about 100,000 light years, with a small portion of the sky showing about 1,000 galaxies that represent the universe's vast history and composition, including dark energy and matter. Astronomers have discovered that dark matter, which makes up about 23% of the universe, plays a crucial role in binding galaxies together through gravitational effects, influencing the evolution of the universe's structure and history.
Insights
- Galaxies like the Milky Way are vast, containing billions of stars and taking hundreds of millions of years to complete an orbit, with the universe's energy content primarily composed of dark energy, dark matter, and only a small percentage of regular matter.
- Dark matter, comprising about 90% of the mass in galaxies, remains a mysterious and enigmatic form of matter detected solely through its gravitational effects, influencing the universe's structure and evolution significantly, as observed through gravitational lensing and computer simulations based on microwave background data.
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Recent questions
How many stars are in the Milky Way?
Around 500 billion stars
What is the size of the Milky Way?
Spans about 100,000 light years
How far are some galaxies from Earth?
Situated 12 billion light-years away
What is the composition of the universe's energy content?
73% dark energy, 23% dark matter, 4% regular matter
How is dark matter detected?
Solely through its gravitational effects
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Cosmology and the arrow of time: Sean Carroll at TEDxCaltech
Summary
00:00
"Galaxies, Dark Matter, and the Universe"
- A galaxy, like the Milky Way, consists of around 500 billion stars and rotates around a common center, taking a quarter billion years to complete one orbit.
- The Milky Way galaxy spans about 100,000 light years, with a light year representing the distance light travels in a year at 186,000 miles per second, totaling around six trillion miles.
- The Hubble Space Telescope captured an image showing numerous galaxies, each containing billions of stars, with some galaxies situated 12 billion light-years away, showcasing the universe's history.
- The image of about 1,000 galaxies represents a minuscule portion of the sky, akin to viewing the sky through the eye of a needle held at arm's length.
- The universe's energy content comprises 73% dark energy, discovered a decade ago, causing the universe's acceleration and expansion.
- Regular matter, including stars, galaxies, and planets, constitutes only 4% of the universe, with the remaining 23% being dark matter, a mysterious form of matter.
- Astronomers like Fritz Zwicky and Vera Rubin observed galaxies' movements within clusters, leading to the discovery of dark matter, which constitutes about 90% of the mass in galaxies.
- Initially, dark matter hypotheses included cold gas, black holes, and giant planets, but improved telescopes ruled out these possibilities, leaving dark matter as a new, exotic form of matter.
- Dark matter's presence is detected solely through its gravitational effects, binding galaxies and clusters together, with Albert Einstein's theory of gravity aiding in its understanding.
- Gravitational lensing, observed in galaxy clusters like the Bullet Cluster, provides evidence of dark matter's existence, as it interacts minimally with regular matter, showcasing its enigmatic nature.
14:50
"Discovery of Cosmic Microwave Background Radiation"
- The discovery of a faint hiss corresponding to a temperature of 2.7 degrees above absolute zero confirmed a specific prediction of the Big Bang Theory, indicating the universe's evolution from a dense, opaque state to one where light could freely travel.
- Detailed mapping of microwave radiation from 13.7 billion light years away revealed small temperature variations, allowing the visualization of sound waves propagating through the universe and the identification of dark matter's gravitational influence on the universe's structure.
- Computer simulations based on observations of the microwave background illustrated the role of dark matter in forming a web-like structure that influenced the evolution of galaxies, stars, and planets, emphasizing the significant impact of dark matter on the universe's history.
