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Old 09-16-2017, 08:13 AM   #31
Jeorbit
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I just came across this article in French from Swiss research university EPFL about mass and gravity : https://qi.epfl.ch/question/show/314

I'm not sure how well Google Translate would do with it, but here are some interesting bits I found:

- They write about how Einstein predicted the existence of gravitational waves and their speed in 1916
- Then how we got the first proof of their existence much later, in 1974 when astronomers at Arecibo observed a binary pulsar, and found the orbital period of the two bodies were exactly as predicted by Einstein's GR. But at this stage and for the next 40 years, it was only an indirect observation.
- And then at last in September 2015 how LIGO observed spacetime distortion caused by two colliding blackholes. Several other observations were made in December 2015 and the last in January 2017.

This might not answer the "why" question, but nevertheless I feel that actually observing the warping caused by gravitational waves is a pretty big deal. Or not?

Last edited by Jeorbit; 09-16-2017 at 08:14 AM. Reason: Typo
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Old 09-16-2017, 10:19 AM   #32
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Originally Posted by Jeorbit View Post
 This might not answer the "why" question, but nevertheless I feel that actually observing the warping caused by gravitational waves is a pretty big deal. Or not?
Yes it is, and not least just as a feast of engineering. Now, the basic concept of a gravitational wave detector is simple enough: you just need an ear or a microphone. If you were close enough to a black hole merger, you would actually be able to hear it without special equipment. The impressive part is building a microphone sensitive enough to pick up gravitational waves from across the universe.
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Old 10-02-2017, 09:00 PM   #33
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If you live in a 1-dimensional world, all other larger dimensions will appear as a line in your world.

If you live in a 2-dimensional world, all other dimensions will appear at least a line, or a plane in your world.

If you live in a 3-dimensional world, all other dimensions will appear at least a line, plane, or a sphere in your world....

So gravity is pervasive and seemingly independent of dimensions.. may we go 4th dimension+ as we know it.
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Old 10-03-2017, 07:14 AM   #34
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Quite a nice short called "Flatland", worth a look:

https://en.wikipedia.org/wiki/Flatland

I turn the pages, but they keep disappearing?

N.
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Old 10-03-2017, 03:39 PM   #35
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Here's something to think about:

The usual takeaway from Flatland has something to do with n-dimensional beings having a better understanding of lower dimensions than its residents but also a type of unaware blindness of higher dimensions. Along with this idea people usually consider lower dimensions as accessible to higher dimensional beings. However, I feel the real situation is that while any given n-dimensional being can more easily imagine lower dimensions, they remain experientially out of reach. Moreover, in the physical realm, we can simulate 2-D realms easily, however we cannot actually create true 2-D or 1-D objects with our 3-D matter.
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Old 10-03-2017, 05:03 PM   #36
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Quote:
However, I feel the real situation is that while any given n-dimensional being can more easily imagine lower dimensions, they remain experientially out of reach. Moreover, in the physical realm, we can simulate 2-D realms easily, however we cannot actually create true 2-D or 1-D objects with our 3-D matter.
I'm not sure I understand the point here.

In what sense do lower dimensions remain 'out of reach' experimentally? It's quite possible to create model systems in which objects (particles, excitations,...) can just move in two dimensions and have no freedom in the third - and these agree very well with 2-dim theoretical models (as in fact they should).

And, if you believe Lisa Randall (or any random string theorist) our matter isn't actually 3d, it just appears so for all practical purposes.

Point being, the question what something actually is is a bit pointless, the question what it is for all practical purposes usually leads you somewhere.
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Old 10-03-2017, 10:14 PM   #37
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Originally Posted by Thorsten View Post
 I'm not sure I understand the point here.

In what sense do lower dimensions remain 'out of reach' experimentally? It's quite possible to create model systems in which objects (particles, excitations,...) can just move in two dimensions and have no freedom in the third - and these agree very well with 2-dim theoretical models (as in fact they should).

...

not "experimentally"

they are experientially out of reach, in that we can't actually transfer our experience (consciousness) into a 2-D plane, or even craft 2-D or 1-D objects, these objects remain conceptual in nature, limited to numerical modelling and calculation.
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Old 10-04-2017, 05:39 AM   #38
Thorsten
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Oops - now that's a funny mis-reading

You're absolutely right of course, sorry - then it all makes sense.
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