The Milky Way Project Talk

What is gravity?

  • homie12 by homie12

    is the force we here on earth observe, really universal?

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  • tryingtothinkagain by tryingtothinkagain

    There is certainly a large body of evidence suggesting that there is a force affecting all objects within the visible universe, and some outside of the visible universe, that causes mass to be drawn to each other with a force inverse to their distance and directly related to their mass. However, gravity is still technically a theory, and not all observations of motion of large bodies perfectly match predictions produced by even Einstein's theory of gravity as a warping of spacetime.

    So, is the force we here on Earth observe really universal? Almost definitely yes, but almost definitely not exactly the way our current theory/theories suggest it works.

    EDIT: If I remember correctly, it's even theorized that gravity, along with other fundamental forces, work differently in different parts of the universe, for any of many possible reasons.

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  • homie12 by homie12

    well ok then wheres its universality then? and using a popular term doesnt explain things to me like what is this space thing? And how can lights speed be constant and time vary when velocity has time as a property?

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  • Feylin by Feylin

    Well, we now have nothing that suggests differently I guess...
    gravity is, as far as I know, simply mass. Even I have gravity, tough its so less it has no effect on the outer world at all.

    But all the stuff, it seems overlapping each other. (I want to add that I don't know if I'm right, since I'm not on this subject with school and I probably won't be for a long time. So I might be wrong, simply because I have incomplete knowledge.)

    Just... why are you getting heavier when speeding up, and why does time slow down in the same situation too.
    Well, does that mean that high masses slow down time? And what makes as mass heavy? Energy? Why do you get heavier then by speeding up? Do you accumulate more energy or something like that? Does time also slow down when you're near a black hole??
    And why does the speed of light always remain the same for the observer, even if the observer is flying with 99,999...% of the speed of light? Then you should see a light beam CRAWL past you. All speed is relative, right?? :S
    But is light even light when it stops? What is light when it stops going fast? What is light anyway? A wave function?
    When time nearly stops when flying with 99,999...% of the speed of light, does it enterely stop when actually flying with the speed of light? What happens in that case when you go PAST that speed? (I know its not possible to do that, (but its still fun to think about) not even to fly with the speed of light itself, because when you speed up you get heavier, it costs more energy to accelerate you and even if you have an infinite amount of energy you will never have enough energy to speed up fully till the speed of light. You can get close, but never a full 100% . Right?? Oh, wait, then why can... well... light fly with the speed of light if it should get infinitely heavy when doing so? Does light have mass? I heard somewhere it does...)
    And why is the speed of LIGHT the universal speed limit? Why not just some other random number? Why the speed of LIGHT?? What's so special about light...? 😕 (a lot things, but you get what I mean I guess...) and how could we ever get past our galaxy? Or better, how could we ever get to the damn NEAREST star?? The speed of light is the fastest speed possible, but even then you would still be CRAWLING to the moon. Damn you nature! I wish I, I wish we, knew more... to tie it all together... But yea... sadly enough I'm not even off secondary school 😕 and I have no idea what is possible, what isn't possible and what is yet known and isn't known. For me right, its all a mess -a very interesting mess tough- with many, many questions...

    Tough, one thing differently, I want to say: great project! 😃 I feel honoured that we, the "normal" people, can now also somehow participate and help science, even if its just a little bit! I hope we help, but I still find it hard to label things correctly... since some features look really much alike. I once saw something that could be a green knot with a red fussy object before it, but it could also be a "small" bubble... 😕

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  • KhalilaRedBird by KhalilaRedBird in response to Feylin's comment.

    One bit of information: gravity is a force. it is a force of attraction between 2 objects whose magnitude depends on the mass of each and on the distance between them. The closer they are, the larger the force. You don't have gravity all by yourself -- it exists between you and the Earth, you and the moon, Earth and the moon, Earth and the sun, etc.

    Feylin

    gravity is, as far as I know, simply mass. Even I have gravity, tough its so less it has no effect on the outer world at all.
    But all the stuff, it seems overlapping each other. (I want to add that I don't know if I'm right, since I'm not on this subject with school and I probably won't be for a long time. So I might be wrong, simply because I have incomplete knowledge.)

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  • Feylin by Feylin

    Okay, thanks. 😃
    But what actually "causes" gravity? (I'm not sure if I formulated the question correctly, I'm not English so I might have got it wrong...)

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  • KhalilaRedBird by KhalilaRedBird in response to Feylin's comment.

    I think the jury is still out on what causes gravity. The attraction of masses for each other is one of the fundamental characteristics of this universe -- so far as we know There is another attractive force that pulls electric charges toward each other. The relative velocities of 2 masses with respect to each other increases the mass and therefore the gravity that each object finds the other to have. The rest mass of a photon is zero. Or so I remember. The discussion and the research continue.

    Feylin

    But what actually "causes" gravity?

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  • gwolfchase by gwolfchase scientist

    I recommend a book entitled "Einstein's Telescope", by Evalyn Gates, for a good discussion about how we currently understand gravity, and the composition of the universe (normal matter, dark matter, and dark energy).

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  • Feylin by Feylin

    thanks! I'll put it on my "to read" list. Which is currently quite long...
    but it really sounds interesting ^^ still looking for some good books about this subject!

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  • Ken_Koester by Ken_Koester

    "Mass tells space-time how to curve; space-time tells mass how to move." That's the saying you see in a lot of discussions about gravity and other things. It's useful to treat gravity as a force, but it isn't clear exactly what a force is--Newton had the same uneasiness way back when. Even worse, gravity is 40 orders of magnitude--that's 10 to the 40th power--weaker than the other 3 forces we know about. So it seems that there is something odd about it from the get-go. In fact, some recent theories posit that gravity "leaks over" from higher dimensions & that that is why it is so weak, that it isn't in some sense one of the fundamental forces.

    Part of our problem is that relativity and quantum mechanics are two of the most successful models ever created; their accuracies extend to many decimal places. But relativity is an outgrowth of classical physics & sort of has that feel to it. QM is completely different. There are subtle reasons I don't completely understand why we think that both of them cannot be right, but no one has been able to come up with a quantum theory of gravity to reconcile the two.

    As for the time dilation thing, it's true that velocity is distance over time. But if your ruler is shrinking at the same rate that your clock is slowing down, you aren't going to notice a thing inside your frame of reference. You only notice when you compare against other frames & the point of relativity is that no frame is more right than any other--they are all relative. (We do know that the effects exist; we can actually measure them with incredibly subtle instruments.)

    As for speed of light, it isn't just light but all forms of electromagnetism as well as strong and weak nuclear forces. Basically, it is saying that information about one part of the universe can't communicate any faster than that with another part (& don't get started with quantum entanglement!). If you travel at 0.99c & emit a light beam behind you, it travels at c--but gets terribly, terribly shifted into the red or even microwave regions (it's all just photons!) to make up for it. Only way I know to beat this cosmic speed limit is to expand space itself--which the universe is currently doing, quite nicely & which is one of the things that Star Trek got right.

    I don't know if I can recommend any books on gravity; the standard reference is about 1200 pages long & throws tensors at you on about page 6 (after which it overran my current abilities (-: ). But you might try Hawking's =A Brief History of Time= or the followup, which is even briefer, IIRC (-:

    And as a coda, apparently Einstein started wondering about relativity at about 16 when he asked himself what the universe would look like if he could ride on a beam of light--and eventually concluded that nothing could go that fast except light itself.

    Snarkhunter

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  • broomrider1970 by broomrider1970

    Whew, talk about twisting the brain of an average citizen LoL Thanks for explaining it so the average pleb can understand it Ken. 😃

    ~Bright Blessings!
    Tina

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  • Ken_Koester by Ken_Koester

    I'm just beginning; I'm retiring end of July to study astro full time. So these are definitely with-a-grain-of-salt comments, & very likely aren't true in various ways. But it's what I remember at the moment.

    Snarkhunter

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  • broomrider1970 by broomrider1970

    Um, You've far more knowledge about any of it than I do. I'm just a military housewife with interest in the beauty of the images. 😃 So I truly do appreciate the information provided. Even if I may not remember it, at least it is here, where I can always return to review it again. 😉 Fibromyalgia kills the memory. LOL

    ~Bright Blessings!
    Tina

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