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After watching the Stephen Hawking Series

  1. Sep 24, 2012 #1
    I just finished watching a few Stephen Hawking specials. I watched "Did God create the universe" and the one about black holes. I am by far not even close to knowing anything about Astrophysics, so please forgive my ignorance. I just found the shows interesting and have a few questions.

    Anyhow, I came away from the series thinking that 1) Dr Hawking agrees that particles getting sucked into a black hole can't just disappear. 2) The center point of a black hole cancels out time (i.e time stops). 3) The big bang is generally the inverse of a back hole. Please let me know if this is not somewhat accurate.

    If it is somewhat accurate, and if the big bang seems like the inverse of a black hole, wouldn't it be safe to say that when a black hole is formed and sucking in particles, it's in theory causing a big bang and creating another universe? I believe that physicists are still trying to figure out where all the data is going, correct? Couldn't the explanation be that it's giving birth to a new universe with its own timeline?

    I'd like to know where all the reputable physicists are at with this. Thanks
  2. jcsd
  3. Sep 24, 2012 #2

    Simon Bridge

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    Re: After watching the Stephen Hawking Series, I have a question

    Broadly. You have watched a lay treatment of some tricky physics ... the idea is to give you an appreciation of how Hawking thinks about these things rather than to provide anything like a rigorous understanding of what is going on.

    1. Stuff going into a BH don't just vanish - no. This means that a BH has to have entropy changes.

    2. The math for BHs have singularities in them - in a non-rotating BH, there is a physical singularity at the center. Thus, what "happens" there is up for grabs. Usually, the singularity is considered to be the result of a mistake in the model rather than something you'd encounter in reality.

    3. I don't think this is mainstream thinking these days. The expansion of the Universe etc does not look like a time-reversal of a BH.

    Or - "could our Universe be on the inside of a supermassive black hole? Jim Haldenwang's article should be accessible - don't be intimidated by the math. It has a section on this.
    Don't understand what you mean by "where the data is going". The incoming particles form part of the BH .... increasing it's Schwarzschild radius.
    There are some fun multiverse models based around the idea that BHs can be sub-Universes with their own timelines etc.

    For an entertaining lay treatment see Gregory Benford's (SF) book, Cosm.

    In general - it is not useful to draw sweeping ideas from a pop-science description of anything science. Treat these things as infotainment and if something interests you, take it as a direction for further study.
  4. Sep 24, 2012 #3
    Re: After watching the Stephen Hawking Series, I have a question

    I agree that it's not "useful" to draw conclusion from unproven theories and pop science ideas. On the other hand, simple theories like "the earth is flat" did lead to the simple conclusion that the earth is not flat. :)

    I've always liked the A.E. quote "if you can't explain it to a six year old, you don't understand it yourself".

    Eventually, some of these frustratingly complicated questions will be answered, and the answers will be quite simple. ;)

    I really believe that if we can understand everything about a BH, it will change a lot of the way we see things.
  5. Sep 24, 2012 #4

    Simon Bridge

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    Re: After watching the Stephen Hawking Series, I have a question

    Beware: people like to put word in old Albert's mouth now he cannot contradict them. Can you cite the quote? (Not to say that it isn't worthy in itself.)

    Also see discussion:

    The trouble is that these pop science shows are not about explaining things to six year-olds: they are about entertainment and selling advertising slots to sponsors.
    Hopefully some of your questions arising from the show have been answered?
  6. Sep 25, 2012 #5
    Re: After watching the Stephen Hawking Series, I have a question

    It's accurate that Hawkings believes this. However his ideas are just one of dozens of competing ideas on what caused the big bang. Hawkings is just guessing and without firm data, his guesses about what happened at the big bang are really not that much better than your or mine.

    That's what Hawkings thinks what is going on. There are other ideas. One is that the information from the particles gets "trapped" near the surface of the black hole and gets sent out once the black hole evaporates.

    People are all over the place. The trouble is that without data, people's imaginations run wild, and there is very little data.


    There is *some* data. The idea is that by looking closely at the ripples in the cosmic microwave background, we might be able to say something about what happened at event zero. The data is improving, and if we can get to the point were we can start showing that some of these ideas are wrong, we are making progress.

    One big of progress was Leo Smolin's idea that black holes could generate baby universes. This was an interesting idea, because he came up with a prediction (i.e. that there wouldn't be massive pulsars) and that prediction was proven wrong (we found a massive pulsar).

    The hard part about the big bang isn't coming up with new ideas. That's easy. The hard part is coming up with a way to show that the idea is wrong.
  7. Sep 26, 2012 #6
    Re: After watching the Stephen Hawking Series, I have a question

    It probably evolved from this.

    "I couldn't do it. I couldn't reduce it to the freshman level. That means we don't really understand it." -- Richard Feynman

    These quotations always get tightened up, then attributed to someone more famous.
  8. Sep 26, 2012 #7

    Simon Bridge

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    Re: After watching the Stephen Hawking Series, I have a question

    Yeah - I found that reference too.
    It's in the intro to his undergrad lecture series - 2nd ed?
    (It is a good habit to cite quotations.)
  9. Sep 26, 2012 #8


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    Re: After watching the Stephen Hawking Series, I have a question

    Just to jump in on this point there's explained and there's explained. A six year old could ask how the heart works and I could explain that the heart pumps blood around the body and I could make motions with my hands to illustrate the muscles moving and perhaps even get a balloon filled with water to impart some understanding of pressure on liquids. But that would not really explain how the heart works in anything more than a very superficial way. To properly explain it would take a long time with hefty amounts of biology lessons to explain key points such as the anatomy of the chambers and vessels, regulation via the sympathetic and vagus nerves, the role of the sinoatrial node etc etc.

    I guess my problem with that quote (regardless of legitmacy) is that it reeks of a self serving attitude. Firstly because of the implication that anything can be simplified to less than lay understanding and still accurately reflect the original concept and secondly because it can be used to transfer any inablity to understand from the student to the teacher. [/rant]
  10. Sep 26, 2012 #9

    Simon Bridge

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    The popularity of the AE pseudoquote is probably due to the self-serving nature: I don't have to learn stuff, if you understood it you'd be able to explain it to me with what I already know.

    Well ... I probably could, but it may take a while.

    That's why the Feynman quote works better ... he didn't say anything about the students understanding the resulting lecture, or how rigorous it would have been, but it's fair comment since (at least after the first semester) a 1st year college physics student theoretically has the basic tools needed to tackle the concepts (and the quote is specific to a particular topic rather than general.)
  11. Sep 27, 2012 #10
    Hawkings shows are not standard astronomy show, it is more like imaginary science
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