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What is spacetime?

Discussion in 'Road Side Pub' started by James Snover, Apr 9, 2021.

  1. James Snover

    James Snover The Ill-Advised Physics Amplification Co Established Member

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    What is space? Why is time tied to it, so that Einstein called it spacetime?

    Einstein created the best theories ( so far) of the universe at the "macro" level, I.e., the one of one in which we live, with his theories of Special Relativity (special, because it did not include gravity), and General Relativity (general, because it did include gravity in it's scope.) it took the old boy over ten years to figure gravity into the big picture. Incredibly successful, but while they explain spacetime and gravity, they do not explain what either one is.

    But he wasn't done there. Uncle Al also started the framework on quantum mechanics, the study of the sub-atomic realm of the atom. Uncovered a whole bunch of strange things he couldn't even begin to explain. It worked, but he hated it. But it worked, so he continued to develop it.

    Fast forward a hundred years or so, and:

    We think spacetime may come in discreet quanta, like elementary particles. We think entanglement and wormholes may act to combine to create what we think of as spacetime. In the same way that individual molecules of water do not act anything like bodies of water. Maybe.

    For further reading, look up "It From Qubit."


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    Last edited: Apr 10, 2021
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  2. 2011 gtcs

    2011 gtcs GT500 poster Established Member

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    Definitely well beyond my knowledge lol. But it's interesting
     
  3. ShelbyGT5HUN

    ShelbyGT5HUN Well-Known Member Established Member

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    What's cool is the earth doesn't orbit the sun because of gravity, but due to the fact that the mass of the sun curves space, creating a "depression" in space. Screenshot_20210410-014956_Chrome.jpeg
     
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  4. DaleM

    DaleM T$45GOATMAGAMen Established Member SVTP OG 4 Life Single Barrel Sirs

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    Which is fine just for earth. How does it work for the other planets?
    OK Bozos, stop clowning around.
     
  5. ShelbyGT5HUN

    ShelbyGT5HUN Well-Known Member Established Member

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    Same effect, just not as pronounced. The sun curves space so every planet will orbit. This picture only shows Earth and Mars, but applies to the other planets as well. Sorta like those "coin funnels" you see at supermarkets

    Fun fact...if you could magically remove the sun instantly, the earth would continue to orbit in a circular path, for 8 mins 20s, at 8:21, once space time flattened out, the earth would shoot off in a straight line for eternity


    Screenshot_20210410-071253_Chrome.jpeg Screenshot_20210410-071517_Google.jpeg
     
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  6. blk02edge

    blk02edge Well-Known Member Established Member

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    Mass bending spacetime IS gravity..
     
  7. DaleM

    DaleM T$45GOATMAGAMen Established Member SVTP OG 4 Life Single Barrel Sirs

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    Jim,
    My son,12, has a space simulation program. You can input most parameters like rotation, revolution, mass, density, temperature ect.

    He want to see if planet formation could have been the result of two different occurances. One, a large object quickly flying through or near the sun and pulling out hot gasses and those gasses quickly cooling to form planets.

    The next is as the star was born did gasses violently escape and did not overcome the gravitational attraction and cooled to form a series of diverse planet structures.

    A couple things he has thought of based on the overall presumption or bias is the cores are super hot for most planets band is that moltwn state a result of just gravity pressures in a solid structure or have origins from a gas rapidly cooling.

    Finally as the kid surprises me is the talk of white hole theories and that the possibility of our known universe emerging from a black holes invisible side, if that even exists.

    He sees a correlation of elongated gasses and masses rapidly shot thru the other side, sorry I am not sure of that term, he just calls it the white side. He imagines it as like a Venturi or water hose for my simple mind. All this hot pressurized and stretched material suddenly experiencing the near opposite of forces into space or a universe that has the physics to assembly the dissemble stuff.

    Any recommended reading for the kid? Just to make sure you understand where this kid's mind is. Over the pandemic he taught himself trigonometry and calculus. Now he says shit that makes me feel like I am talking to an alien.
    OK Bozos, stop clowning around.
     
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  8. wizbangdoodle

    wizbangdoodle Inslee is an Idiot Premium Member Established Member

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    Ok, so from what I gather here, we are in a continual rotational spin, much like an eternal turd going around a toilet bowl. Does that sum it up accurately?

    Move on, nothing to see here.
     
  9. blk02edge

    blk02edge Well-Known Member Established Member

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    Planets form from gas/dust/rock/ice etc. that are in random orbit and slooooowly gravitate towards each other eventually clumping up into a sphere. Your son's explanation could certainly play a huge part it in.
     
  10. James Snover

    James Snover The Ill-Advised Physics Amplification Co Established Member

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    Right, but it's a combination of the Sun's _and_ the Earth's mass, even though the sun out masses Earth by something like 330,000,000-to-1. It distorts space enough that as far as the Earth is concerned, it's moving in a straight line next to the sun. But that straight line is a full circle warped into space. Which is why the Earth doesn't experience any sort of centrifugal force (which, itself, is an illusion, but a useful one, so I'll allow it). Mass causes space to bend, and the bending in space dictates how mass moves. It's a real headache to calculate all the interacting forces in multiple bodies, but we do know this: mass always adds up. Never down. Which is why gravity has such a huge effect on the universe. All the other forces are polarized, and can be made to cancel each other out. Not gravity. Which isn't really a force, just a side effect.
     
  11. James Snover

    James Snover The Ill-Advised Physics Amplification Co Established Member

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    Yes and no. Yes, because it approximates the same effect. No, because the coin trick is a product of angular momentum being conserved, more commonly, but erroneously, known as "centrifugal force." The Earth, in fact, none of the planets, anywhere, feel any sort of centrifugal force effect. The Earth "thinks" it and the sun are just going along, forever, in a straight line. But the nifty trick is that this straight line is a product of the distortion of space by the mass of the sun and the Earth, and it turns out that this straight line is, in fact, a circle.
     
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  12. James Snover

    James Snover The Ill-Advised Physics Amplification Co Established Member

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    Your son has got a sharp mind! Can't wait to see what the young man will do with it, in time.

    I'm going to intersperse the replies in your original post, hopefully to avoid confusion:

     
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  13. ur bittn

    ur bittn By the snake Premium Member Established Member

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  14. BlckBox04

    BlckBox04 I am the liquor Premium Member Established Member

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    Space time in my house is just called “alone time”
     
  15. quad

    quad Well-Known Member Established Member

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    Space is curved by the sun because of it's mass and gravity. Replace the sun with a little rock and boom space is not curved as much. And the Earth spins off into the galaxy along with all the other planets lol! Maybe Jupiter will keep them bound to the Solar System?

    If You Think Jupiter Orbits the Sun, You're Mistaken

    If we picture the solar system, we often picture our dominant star at the center of things, static and immobile as planets orbit circles around it. That picture makes things simple to understand, but technically it's inaccurate. Take our largest planet Jupiter, for instance. It doesn't orbit the sun's center — it orbits a spot in empty space between it and the sun called the barycenter. This is because the sun doesn't just exert gravity on Jupiter — Jupiter's so big that its own pull affects how the sun moves, too.
     
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  16. PhoenixM3

    PhoenixM3 Hello Kitty Slayer Premium Member Established Member

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    What I’ve learned is that you nerds get laid a lot less than some us.
     
  17. LuuisHernandez

    LuuisHernandez Active Member Established Member

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    Are you saying earth doesn’t feel the centrifugal force or that it doesn’t experience centrifugal force at all?


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  18. James Snover

    James Snover The Ill-Advised Physics Amplification Co Established Member

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    Dosen't feel or experience centrifugal force, at all. Because centrifugal force is not a factor in Earth's, or any other orbiting body's, orbit. Nothing in orbit around another body feels centrifugal force. Because the bodies themselves aren't traveling in a curve; it is the space itself that is curved. Curved by the mass of the two bodies. Mass/energy curves space, space tells mass/energy how to move.

    Think of it like this: tie a baseball on a six foot string, dunk it in water, and spin it around your head. That is centrifugal force. For a very a small body, moving at far less than a 100mph. It's a pretty considerable amount of force. Enough to throw off any water remaining on the baseball.

    The Earth is orbiting the sun at a distance of 93,000,000 miles, at a speed of 67,000mph. If it were affected by centrifugal force, there wouldn't be anything on it, everything would have been flung off, including the atmosphere, oceans, and us. In fact the planet would most likely crumble and break up from that much angular momentum.

    Ironically, though, we do feel centrifugal force, due to Earth's rotation. And it's worth about five pounds. Stand at either pole, and you'll be about five pounds heavier than if you were at the equator. Thanks to the Earth's 1,000mph average rotational speed.
     
  19. LuuisHernandez

    LuuisHernandez Active Member Established Member

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    Conversely, what keeps gravity from essentially crushing us? I understand the earth’s gravity is weak, relatively speaking, but I always thought gravity counteracted the also weak centrifugal force. That’s the suspected reason behind the earth bulging along its equatorial diameter compared to its polar.


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  20. DaleM

    DaleM T$45GOATMAGAMen Established Member SVTP OG 4 Life Single Barrel Sirs

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    He chose the Misner collaboration about Gravity. Should be here tomorrow.


    OK Bozos, stop clowning around.
     
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