Quantcast

Lawrence Krauss, author of A Universe from Nothing lecturing on cosmology.

  • Don’t really agree with or like his monolithic straw-man representation of “religion" versus "science" at minute 6. "Religion pretends to know all the answers" .


    Sub-i, sub-j, larry. There are many religions and many sciences.
  • Minute 14. Edwin Hubble’s original data! straight-line plot through a bunch of dispersed points. “That’s why we know he was a great scientist” — nobody laughed in the tape, but I did — “he knew that he should draw a straight line through a cloud of points”. I also love it when people take the time to go through an old paper, pull things out, and present them anew.
  • I have never understood the business of standard candles. To me it seems like you have two degrees of freedom (distance and brightness), only one of which can be knocked out by the measurement of apparent brightness.

    So say we figure out a “standard candle” — a star with a particular colour signature that tells us “The star is at X phase of its life, is made up of Z, and such stars always shine at a constant brightness of 1 for Q million years.”

    But still — how do we know that our theory is right? How do we know, know, know that  it’s really brightness of 1? It’s not like we can triangulate. And it’s certainly not like we’ve been there and seen it first-hand.
  • I had the same problem in a discussion with a geologist a few months ago. I sometimes get the sense that working scientists are so immersed in the practical fact that, yes, for all intents and purposes we know X to be true, that they’re not willing to step back to an abstract, philosophical level and say: “Well, if you really keep pulling on the threads, there are assumptions at the bottom of everything, so yes, we really don’t absolutely know X to be the case. However, Philosophical Prig, we don’t really know we’re not living in The Matrix either! So hush up and get back to doing something relevant.” But that’s the kind of answer I really want to hear: no, we don’t know know know, but for all practical purposes, yes we know.
  • Minute 15. How old is the universe? So Hubble got the answer wrong in 1929, and it was obviously wrong. “Scientists don’t know what they’re doing”

    But I had the same reaction to people talking about dark matter in the 90’s. “What is this stuff we call dark matter? Or dark energy?” As I understood it at the time, “dark matter” just represented a 90% fudge factor in astronomical measurements. It could be that gravity or quarks or anything else about the laws of physics is simply different in other parts of the universe. And how would we rule out that hypothesis? We just rule it out by assuming that the laws of Nature are the same everywhere, because that’s what we’ve assumed for the last few hundred years and it’s always worked out. Straight-line extrapolation to “That assumption must be true now and everywhere” despite that we’re now talking about multiple galaxies so unimaginably far away.
  • Minute 18:30 "This is a Hubble plot, much better than Hubble’s plot. It was made after the discovery that on a log-log plot, everything is a straight line.” Again, no laughs, but I thought that was hilarious.
  • Calculations that estimate the total energy in all vacuums add up to 10^28 times the observed mass of the universe. Whoops.
  • Dark matter here on Earth? Let’s go down into the mines and measure it. (By the way, where would the physicists be if those evil resource-extraction companies in Lead, South Dakota hadn’t negotiated with the legal entities that be and drilled into the Earth’s crust? Way to play it as it lies, Sandia Labs. #scruples)
  • Flat, closed, or open universe? (also why are these the only three options?) Well, we only observe 30% of the mass thta would be required to make the universe flat.
  • A gigantic, gigantic, um, really gigantic triangle — to measure the curvature of the universe.
  • That’s what those microwave-background radiation detecting balloons in Antarctica have been doing.
  • There’s always something there, even when there’s nothing. (see this video of the quantum fields flickering about in empty space)
  • 90% of the mass of a proton is due to the vacuum. (not delta spikes, more like 1/x or exp(−x) integrals.) Therefore your mass is 90% due to quantum fluctuations around the zero point energy.
  • The universe also has a net total energy of 0. Hence the possibility of “a universe from nothing” (our universe needn’t have a Creator since there is enough mass/energy in the physical vacuum that those virtual fluctuations could have acted as a Prime Mover).
  • 70% + 30% = 100%
  • Making our place in the Universe even less special. “Regular” matter—the stuff we observe—is only a 1% pollution in the uniform dark-energy / dark-matter background of the universe.
  • Deep-future scientists (like in a few billion years) won’t be able to observe other galaxies. Measuring the universe, they will observe (correctly) that their galaxy is the only one around, and that there is nothing but empty, eternal space around them.
  • So they will be “Lonely and ignorant, but dominant. Of course those of us who live in the United States are already used to that.”

20 notes

  1. tolerablescamp reblogged this from isomorphismes
  2. spetharrific reblogged this from isomorphismes
  3. king-of-dongs reblogged this from isomorphismes
  4. dorkshdw said: for standard candles, look up cepheid variables and type IA supernova. you’re right to be worrie/d about their standardness, and you wont get a full understanding of all the groundwork & maths unless you’re taking an astro degree.
  5. intothecontinuum said: lol at the lines! Also, were you going to link to a video with the “quantum fields flickering”?
  6. isomorphismes posted this