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E=mc^2 how you picture it in nature?

  1. Jan 16, 2016 #1
    When you close your eyes and visualize E=mc2 in nature without math, what images do you see?

    I always saw the Hiroshima mushroom cloud, but after reading your posts, I agree bombs are not the right image when introducing concept to kids.

    1. I now see star core nuclear fusion of hydrogen into helium as the best visual of E=mc2. Agree? What you see?

    2. Is starlight most obvious example of E=mc2? Can we say stars shine for billions of years entirely because of E=mc2?

    3. If Starship Enterprise transporter transported a kilogram of star core onto the transporter pad, what would we see? Solid, liquid or gas? Glowing or dark? How radioactive would this star core goop be? How hot would the goop be and how long would it remain hot? Removed from star core pressure, would this goop just be a harmless inert puddle?

    4. Atomic bomb is fission, star core is fusion, but is a hydrogen bomb explosion more fusion than fission?

    I misunderstood C2 as lightspeed so saw it involving Han Solo or Captain James T. Kirk going warp speed. After reading your posts I see C2 is not about travel or light, but about potential energy. It is easier for me to now see C2 as Universal Constant Squared, to avoid Star Trek images.

    As a humanities teacher, I can easily teach most high school astrophysics. Kepler and Newton are easy. Einstein is much harder. I avoid math, but E=mc2 is too important to ignore.

    I'm a huge fan of Carl Sagan's COSMOS and Neil Degrasse Tyson. Sagan's last interviews before dying lamented most Americans no longer understand technology we depend upon: TV, radio, lightwaves, electricity, nukes, computer software is all a total mystery to 90% of the public. That is dangerous, as Sagan says: "If we don't understand our world, then we are just putty in the hands of those in power."

    Take a look at Sun video below: It is exactly what I've been asking for, the kind of simple stuff anyone can understand, using props and toys. When this Australian dude smashes wet sponges together, even the girl who didn't understand suddenly understands water splashing out is the Energy that starts solar convection that results in sunlight photons.

    Know any more easy youtube videos to introduce astrophysics?

    Best videos to introduce E=mc2 so far:

  2. jcsd
  3. Jan 16, 2016 #2


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    Staff: Mentor

    1. I see nothing.

    2. I think you're getting too caught up in a cause/effect relationship. Star's shine because they are very, very hot. Fusion in the core releases energy which replaces the energy lost by the star as radiated starlight. You could claim that mass-energy equivalence is responsible for this, but you could also claim that the interaction between nuclei via the strong nuclear force is responsible and the loss of mass via mass-energy equivalence is just a by-product.

    3. They'd see nothing, as the sudden drop in external pressure would cause the material to violently explode, obliterating the ship. However, inside the star the material exists in a very, very dense plasma (an entirely separate phase of matter that is neither solid, liquid, nor gas) at around 15 million kelvin. You can find more info here: https://en.wikipedia.org/wiki/Solar_core

    4. It depends on the design. Most warheads, if not all, generate the majority of their explosive power through fission. The fusion stage is simply used to generate a massive neutron flux that then initiates the fission of the tertiary stage. Replacing the tertiary stage with a non-fissile material can help increase the proportion of energy generated by fusion, resulting in a cleaner bomb.

    I don't see why E=MC2 is so important. The fact that energy has mass is hardly important to understanding the vast majority of basic astrophysics. And the fact that your students probably won't have any idea what energy really is doesn't help the matter.

    For students who require this kind of teaching method, I can't see how they would understand mass-energy equivalence. Do they even understand what mass or energy is?
  4. Jan 16, 2016 #3


    Staff: Mentor

    All current warheads do AFAIK; but the "superbomb" warheads that were tested in the 1950's and 1960's (and were in some cases put in service on bombers and missiles, though thankfully none were ever actually used) got most of their explosive power from fusion. See, for example, here:


    The key design difference in the "superbomb" warheads was that the tertiary stage was fusion instead of fission; that makes the yield of the weapon potentially unlimited, whereas the yield of a boosted fission weapon (i.e., a weapon with a fission tertiary stage, boosted by a fusion secondary) is limited.
  5. Jan 16, 2016 #4


    Staff: Mentor

    None of the above. A star is plasma throughout; and in the core, electron degeneracy pressure (due to the Pauli exclusion principle) is significant, so it's nothing like any substance we can observe on Earth.

    This also means, btw, that, as Drakkith pointed out, the core substance would explosively expand as soon as it was transported, since it would have just been transferred from being compressed by the weight of an entire star to not being compressed at all. It would vaporize the transporter, and indeed the entire starship, within a fraction of a second. So you would have to be sure not to blink if you wanted to see what it looked like. :wink:

    It would be glowing in visible light, but that would be only a small part of the energy being emitted. Most of the radiation in the core is gamma rays produced by nuclear reactions; depending on the specific reactions, there might also be a large neutron flux.

    It wouldn't be "radioactive", strictly speaking, because that word implies nuclei decaying via relatively slow and low-energy weak interactions. But it would certainly be emitting very energetic radiation; see above.

    Typical star core temperatures are in the tens or hundreds of millions of degrees Kelvin. It would take a lot of expansion (see above) to lower that temperature to something manageable.

    Most certainly not. See above.
  6. Jan 16, 2016 #5


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    Who is this "your" that you are referring to? It seems that you're talking to someone, and forgot to mention who this person is.

    Wow. This is astoundingly puzzling. If starlight is THAT obvious of an example, this relationship would have been discovered by cavemen, because they certainly saw starlight back then, and probably even brighter than what we are seeing today.

    The rest, I'm not going to touch with a 10-ft. pole.

  7. Jan 17, 2016 #6


    Staff: Mentor

    Personally, my favorite example is electron-positron annihilation which is used every day for medical purposes in PET imaging.

    However, I don't think that it is logically possible to think about E=mc2 itself without math since it is a mathematical formula. When I think about The formula I think about geometry where m is the length of a four-vector whose components are E and p.
  8. Jan 17, 2016 #7


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    I don't know why. When I was a kid, I always liked seeing stuff blown up. You may think kids just want to see Frozen or the Little Mermaid, but they're also happy watching Godzilla flatten Tokyo. It's why parents spend so much time educating the savage out of their children, to turn them into (responsible) adults.

    But if Hiroshima brings up too many questions, there are plenty of videos of nuclear tests where no one was harmed which are still quite spectacular.

    Here is a short clip of the underwater test done at Bikini Atoll in 1946:

    Both tests at Bikini used plutonium bombs similar to the Fat Man device dropped on Nagasaki 11 months earlier, and each had a yield of about 23 kilotons of TNT.


    The pictures from this test were so spectacular, that French fashion designers decided to use the name 'Bikini' for a new line of two-piece women's swimsuits which they were about to introduce.
  9. Jan 22, 2016 #8
    I see "our" misconception about mass. Take look at this PBS Spacetime video :
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