You can't prove every single theory in mechanical or structural engineering just because you can usually touch what you design.
I may be missing something here, but I think we
can build proof of anything that we can theorize in my fields.
'Course something's would take enormous expenditures, materials, time, and manpower.
Do you have an example in mind of something we couldn't build to prove a mechanical or structural engineering theory?
I asked because you seemed to lack any theoretical knowledge or understanding of electromagnetism. Coupled with the way your post is written, here's how it sounds: "There's no way I can be wrong because we can't go there to test it." That's pretty absurd considering how many things we know that can only be tested from afar.
Sorry, that's probably just my writing style, it was not meant to imply that I knew the answers. Only that I felt the answers we have, have in no way been proven absolutely correct, but that we make the assumption they are because we can't produce the physical proof that we demand of almost all other theories.
I do have a working knowledge of electro-magnetism, and do feel that whether it can or cannot be worked out mathematically, a unified field does exist and gravity is
the major player in binding it together (no pun intended).
Nope and nope. If you look at something really, really far away, the last few miles aren't going to matter for this kind of measurement. Most of the medium between here and really, really far away is deep space with a particle density as close to vacuum as is likely possible - something like 1 proton per cubic meter. People who do this stuff for a living are smart enough to figure out how to work around the issue you're trying to lay down as insurmountable. It's possible that we have the wrong value for the speed of light and it's possible that we think we know more than we do, but not for the reasons you're suggesting.
While I can respect that opinion, I can't take it as proof.
You're looking at
one end of a beam of light that has been traveling in some cases, longer than we have been observing the stars.
Just because the portion of the stream you are looking at is traveling at a fixed speed does not absolutely mean the entire stream is or has been.
If it helps think of it as a river.
The Mississippi at it's delta is normally at a fixed speed (let's discount storms, winds and floods for now, we will assume they are stuff in deep space we have no knowledge of).
As the river makes it's way to the delta from where it starts, it speeds up and slows down depending on conditions (that we of course, can't see from the delta)
Standing at the delta (Earth) we can see none of that (without physically following the river's route).
So we could naively say we know the absolute speed of the river because we observe it at the delta.
And if our observations are limited to a short time period vs how fast the river flows, we could always appear to be correct over that short time period where we were observing from.
Yet, at the same time upstream 500 miles the river is flowing twice as fast and 1000 miles upstream only half as fast, but unless something happens to change things, the speed remains constant from our point of view.
It took almost 50 years to prove that the Higgs-Boson particle actually existed and wasn't possible to prove without the Hadron Collider to
physically prove it.
My point is that if it is something that we
can physically do, science doesn't call it absolutely proven until we actually see or do it.
But, if it is something beyond our abilities to prove physically (presently), we theorize and
call it correct, until it isn't.
By that reasoning the world was flat for eons and the theory should have not been challenged, eh :biggrin:
It's funny that you mention this because I designed a high accuracy laser range finder that I was able to accurately test even if I didn't walk 2000 meters away from the base station. I was able to determine if the air between the base station and the target was hot, cold, dusty, obstructed, or a host of other environmental issues without ever leaving my computer. The only thing I had to do to normalize my measurements was use the range finder in my lab. Assuming I don't point it at something that will confuse the sensor, which is a completely different issue, I don't ever need to visit a location to know how far away it is.
As I said, for what we do here on Earth, I'm sure you're distances are accurate and that you have compensated for all known issues.
But, that is also my point,
known issues.
Without actually going there, we don't know all the issues that may or may not affect measurements using speed of light.
As far as "confusing the sensor", when we look into deep space, how can we be certain we aren't.
Without the physical aspect being involved, we can only assume.
To the best of my knowledge Einstein never imagined that we could stop light, yet as of last year we held it to a standstill for over a minute.
Current theory has it that light has an absolute speed of about 186,000mi/sec.
And it is easily proven that it does, here and near the Earth.
But, since only the naïve would believe (and not the astrophysicists I've taught to) that we have discovered all the secrets of the universe, we can only surmise what the light does it deep space or what else is in deep space beyond what limited range our instruments can
reliably observe.
(kinda sounds like one of the Discovery Channels pseudo-docs, huh)
Here's a simple example to illustrate what I mean.
We all know that Einstein showed that gravity can curve the fabric of space-time and that light follows that curvature.
So, Draw a half circle
Place a dot at each end of the half circle.
Label them A and B
Measure the distance in a straight line between the dots,
and then draw a straight line that exact length, attaching it to APlace a dot at the end of the straight line and label it C.
(you should end up with something that looks like a raster side view of a spoon)
Assume the half circle is the path of light as traveled when affected by a blackhole somewhere between A and B.
So if A produces light, we measure the distance from A to C (the straight line) as X light-years.
But we measure the the distance from A to B as X+ light-years, because of the distance of the curved path.
Yet the A-B and A-C distance is in reality the same.
Not only that but the color shift caused, by the deflection, will point us in the wrong direction if we physically try to follow it back to A.
So where are we standing, on B or C ?
Yes, it is an exaggeration to make a point, but I think it is still valid enough.
While we know how to look for blackholes, we don't know how to look for things that we may not know about or know enough about.
Here's an easier one to confirm.
Until recently (2009) the nearest blackhole to Earth was pegged at approx. 16,000 light-years.
We
absolutely knew the speed of light and
all other conditions in deep space (or we were told we did).
Scientists have since determined that that distance is off by about a whopping 50%.
The new distance is pegged at 7,800 light-years (with a margin of error of 6%)
Apparently they underestimated how much interstellar dust affected the way the speed of light was used to measure the distance.
So what, our estimate of how dust affects optical measurements here on and near Earth doesn't apply to how it works in deep space all of a sudden?
Who knew?
And is that same interstellar dust compensation factor to be applied to other deep space objects?
They now assume they have it correct, and just may, unless they find another mitigating factor.
But
IF they do have it right, why haven't they used that dust compensation factor on other deep space distances?
How possible is it, that of all the objects we observe in deep space, this
single blackhole is the
only object we got the distance wrong on, based on a little dust between here and there?
There is just so much we don't know, but only assume about deep space.
We predict how close asteroids and other objects will pass by us when they are great distances away, yet those distances being accurate 20% of the time once the objects are much closer is doing good.
As they get closer, passing distances are constantly calculated and recalculated and often differ greatly form the original calcs.
So what happened, somebody "forgot to carry the one" or what?
No, it's just that we don't know all we need to, all the affecting factors, to plot the course even here in near space.
Yet we are arrogant enough to assume we know more about deep space??
Heck, I know astrophysicists that are still looking for the 10th and 11th planet/planetoid based on orbit deviations of those planets we can see, and this is in near space.
We won't accept the 10th's or 11th's existence without
double confirmed physical proof, but we readily accept the stuff we can only assume is going on in deep space as gospel.
BTW - Thanks for the discussion, that's kinda rare at ATOT
I'm going to end here as this has pretty much turned into an Off-Topic discussion, but I'd hate to see it moved there.