Astrophysics: Back in time at edge of the universe

On wednesday, I got to hear George Smoot speak. Here are the awesome videos of his lecture with lots of cool visualizations of the universe.


The main lesson of his talk was “you can learn a lot about the structure of the universe by observing the fluctuations of the matter, light, etc.” He gave example after example of this in his talk, and explained some of the open questions.


According to the big bang theory, the universe started 13.4 billion years ago and has been expanding ever since. For his Nobel prize winning discovery, he used satellite measurements to find variations in temperature from cosmic microwave background (CMB) that provided a detectable signature of the big bang theory. a neat application of astrophysics + thermodynamics + statistics. he proposed this to NASA in 1974 and they finally launched the satellite 15 years later which provided the confirmation. This is his Smooth research group website. They have a new website for learning about cosmology called the Universe Adventure. As I continued to listen to his lecture about the timescales he was talking about measured in billions of years, everything on earth seemed completely insignificant in comparison–that effect lasted on me only for a few hours.


Smoot points out that in astrophysics time = distance / speed of light. Telescopes allow us to look back in time because the light we see is coming from such a long distance (millions and billions of light years away) all the way back to the big bang.


In the 1960s, Penzias and Wilson at Bell Labs used a satellite to measure microwave radiation and discovered some patterns that indicated they were remnants of the big bang. In 1992, the COBE satellite that Smoot sent up added greater precision and gave unambiguous confirmation of the big bang. Even greater precision was achieved with WMAP in 2003 and PLANCK to be launched in 2008.


Smoot explained that scientists learnt a lot about the structure of the sun by observing “ripples” caused by standing waves, which said something about the wavelength and velocity of propagation, and hence the density of the material inside it.


Using the Sloan Digital Sky Survey, maps of celestial bodies (stars, etc) all across the universe have been created and their lumpy structure was explained by gravitational attraction influencing the evolution of these bodies when simulations were run on similarly sized objects.


The best estimates say that universe consists of

  • 73% dark energy — no idea what this is, maybe a new force of nature

  • 23% dark matter — no light passes through it so we don’t know what it is

  • 4% normal matter

Supernovae are the “standard” candles or guideposts when mapping the universe based on observing their brightness versus time. Their distance can be estimated (calibrated) using the length of the time the star stays bright. Gravitation changes the path of light and that’s how we know about large clumps of “dark” matter. This is called “gravitational lensing.” Observations of light leads to a deconvolution problem to infer the structure of the dark matter.


He left the audience with these big questions seeking answers in astrophysics,

  1. What is the right physics to describe the universe?

  2. Did inflation [of the universe] happen? How?

  3. What is the dark matter?

  4. What is the dark energy?

  5. What generated the matter-antimatter asymmetry?

  6. Are there other relics to be found? (e.g. cosmic strings)?

  7. Are there extra dimensions?

  8. Do fundamental constants vary?

  9. What other exotic forces might come into play?


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