Space dimensions

[Tesseract999]

Is the more than 3 dimensions often discussed mere mathematical models or do they really eXist

[Strange]

5 minutes ago, Tesseract999 said:

Is the more than 3 dimensions often discussed mere mathematical models or do they really eXist

Currently they only exist in mathematical models like string theory. 

[Tesseract999]

That means they are just theoretical meant only for better comprehension? 

[Phi for All]

33 minutes ago, Tesseract999 said:

That means they are just theoretical meant only for better comprehension? 

It's difficult to imagine what a fourth spatial dimension is needed for, outside of mathematics. We use three spatial and one temporal dimension as a coordinate system to figure out when and where a particular event takes place. If we both know what x, y, z, and t are, we can arrange to meet (40.748817, -73.985428, +767 feet, 8/3/2019 1PM UTC tells you to come to the 59th floor of the Empire State Building at 9am local time tomorrow).

[Tesseract999]

Has this idea of time as a fourth dimension always been along or was this Einstein's contribution? 

[Phi for All]

1 minute ago, Tesseract999 said:

Has this idea of time as a fourth dimension always been along or was this Einstein's contribution? 

Time was considered an independent dimension before Einstein, who showed how "spacetime" is a continuum that can't be separated. 

[Strange]

2 hours ago, Tesseract999 said:

Is the more than 3 dimensions often discussed mere mathematical models or do they really eXist

The question of whether things "really exist" is outside the scope of science. Physics uses things like space-time dimensions, electromagnetic fields, etc. because they are useful for producing models that "work" (produce useful results). Whether those things exist or not is a question for philosophy, not science.

[beecee]

1 hour ago, Strange said:

The question of whether things "really exist" is outside the scope of science. Physics uses things like space-time dimensions, electromagnetic fields, etc. because they are useful for producing models that "work" (produce useful results). Whether those things exist or not is a question for philosophy, not science.

While I agree with that mostly, I see the acceptance of space and time [spacetime] being real, as reasonable considering that spacetime can be bent, warped, twisted or in some way misshaped from flat, in the presence of mass/energy, and that we interpret as gravity. The philosophical side imo starts when we question whether spacetime, gravity is the underlying  reality or truth of the universe. Science models what we see and to explain our experimental results, and any underlying truth or reality, if it at all exists, is not the goal. If though we happen to stumble on that reality or truth, all well and good.

[Tesseract999]

10 hours ago, Strange said:

The question of whether things "really exist" is outside the scope of science. Physics uses things like space-time dimensions, electromagnetic fields, etc. because they are useful for producing models that "work" (produce useful results). Whether those things exist or not is a question for philosophy, not science.

But if time as is said a physical entity relative, according to Einstein then only can it be possible to affect changes on time. On the other hand if it's actually an independent entity then it's unchangeable right. 

Again is it Experimentally proven that time runs slower nearlarge gravitational fields? Or that too is just speculation? 

Edited August 3, 2019 by Tesseract999

[StringJunky]

14 minutes ago, Tesseract999 said:

But if time as is said a physical entity relative, according to Einstein then only can it be possible to affect changes on time. On the other hand if it's actually an independent entity then it's unchangeable right. 

Again is it Experimentally proven that time runs slower nearlarge gravitational fields? Or that too is just speculation? 

The Global Positioning System corrects for it 24 hours a day... it's a fact.

Quote

Because an observer on the ground sees the satellites in motion relative to them, Special Relativity predicts that we should see their clocks ticking more slowly (see the Special Relativity lecture). Special Relativity predicts that the on-board atomic clocks on the satellites should fall behind clocks on the ground by about 7 microseconds per day because of the slower ticking rate due to the time dilation effect of their relative motion [2].

Further, the satellites are in orbits high above the Earth, where the curvature of spacetime due to the Earth's mass is less than it is at the Earth's surface. A prediction of General Relativity is that clocks closer to a massive object will seem to tick more slowly than those located further away (see the Black Holes lecture). As such, when viewed from the surface of the Earth, the clocks on the satellites appear to be ticking faster than identical clocks on the ground. A calculation using General Relativity predicts that the clocks in each GPS satellite should get ahead of ground-based clocks by 45 microseconds per day.

The combination of these two relativitic effects means that the clocks on-board each satellite should tick faster than identical clocks on the ground by about 38 microseconds per day (45-7=38)! This sounds small, but the high-precision required of the GPS system requires nanosecond accuracy, and 38 microseconds is 38,000 nanoseconds. If these effects were not properly taken into account, a navigational fix based on the GPS constellation would be false after only 2 minutes, and errors in global positions would continue to accumulate at a rate of about 10 kilometers each day! The whole system would be utterly worthless for navigation in a very short time.  http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html

 

Edited August 3, 2019 by StringJunky

[Strange]

47 minutes ago, Tesseract999 said:

Again is it Experimentally proven that time runs slower nearlarge gravitational fields? Or that too is just speculation? 

Yes, this is experimental confirmed. It can be measured over quite small differences in height (less than a meter, I think, from memory).

[Amazing Random]

48 minutes ago, Strange said:

Yes, this is experimental confirmed. It can be measured over quite small differences in height (less than a meter, I think, from memory).

Yes if one observer is at the top of a mountain and the second observer is at sea level then time for the first observer passes faster for 10^-6 s every 1 day.

[StringJunky]

59 minutes ago, Strange said:

Yes, this is experimental confirmed. It can be measured over quite small differences in height (less than a meter, I think, from memory).

20cm but I think that is with a what was then an experimental clock. GPS clocks are 30cm I think. 

 

Edited August 3, 2019 by StringJunky

[Tesseract999]

2 hours ago, StringJunky said:

20cm but I think that is with a what was then an experimental clock. GPS clocks are 30cm I think. 

 

But could that be Becoz the force interfered with the mechanism of the clock ,but does that mean the 'time' actually slowed as such.

And the idea that an astronaut travelling at near the speed of light does not age as quickly as people back on earth how is that possible? 

[StringJunky]

12 minutes ago, Tesseract999 said:

But could that be Becoz the force interfered with the mechanism of the clock ,but does that mean the 'time' actually slowed as such.

And the idea that an astronaut travelling at near the speed of light does not age as quickly as people back on earth how is that possible? 

NO but I'm sure swansont will explain why. It's his professional field. I think the most I can say is that it doesn't matter what type of clock you use,the result will be the same; as long as its resolution is fine enough, of course.

Edited August 3, 2019 by StringJunky

[swansont]

3 hours ago, Amazing Random said:

Yes if one observer is at the top of a mountain and the second observer is at sea level then time for the first observer passes faster for 10^-6 s every 1 day.

More like 10 nanoseconds, and it would depend on the mountain.

Someone I know did this experiment on Mt Rainier in Washington state

http://leapsecond.com/great2005/

"Clocks that run fast gain time, so given our high elevation and how long we stayed, the prediction was that these clocks would gain about 22 nanoseconds. This, not because the clocks were moving (they were in a parked minivan), but simply because the clocks experienced a lower gravitational field by being 5400 feet above sea level for two days."

(It's actually gravitational potential that's important. The field strength is one part of that)

4 hours ago, Strange said:

Yes, this is experimental confirmed. It can be measured over quite small differences in height (less than a meter, I think, from memory).

About a third of a meter, and it took several hours to get statistically significant data, but then this was a few years back. Optical frequency standards today could do it in a shorter time, or measure smaller distances, if anyone was interested in doing such an experiment again. (But it's kind of a stunt at this point, because we know the phenomenon will happen, and who wants to waste the effort of engineering it when you could be doing real physics?)

21 minutes ago, Tesseract999 said:

But could that be Becoz the force interfered with the mechanism of the clock ,but does that mean the 'time' actually slowed as such.

No, that doesn't work as an explanation. It doesn't depend on the kind of clock, and you wouldn't expect a physical mechanism to interact in identical way with atomic clocks made from different elemental species (and there are a bunch that are used). Plus, one of the basic assumptions that makes physics work is that the physics is the same in any inertial reference frame. If that fails, basically all of physics falls apart, and physics works pretty well. Having it be the result of a force means you have to identify this force, and why it's present at differing amounts in different frames. It leads you there being a preferred frame of reference, and physics doesn't work that way.

Time dilation is a direct consequence of c being invariant and finite. The result is that length and time are relative to your own frame of reference.

[Strange]

59 minutes ago, Tesseract999 said:

But could that be Becoz the force interfered with the mechanism of the clock ,but does that mean the 'time' actually slowed as such.

That doesn't work because it is a relative effect. So from one frame of reference, the clock doesn't slow at all. From another frame of reference it might slow by 10%. Frome another frame of reference it might slow by 50%. How can this force act on the clock differently depending on who is measuring it?