does the past still exist ?

[PhysicsMan94]

Oh I have no doubt its convincing, just as many things have been convincing in the past. I have no issue with the believability of it all, I'm sure it fits perfectly with our understanding of the universe. My query isnt about the limitations of its viability, its with the limitations of our understanding.

Problem is that we have a fairly good understanding of both General and Special Relativity now and even have to account for the effect of the latter in spacecraft maneuvers and such. If we suddenly found that one of the most important underlying principles of SR (and GR to an extent), namely the fact that no object with any mass may travel at or faster than the speed of light in any frame of reference, was broken then a whole load of well-established Physics would be undermined.

Now that's not impossible, we've been wrong before, but the chances of us being wrong to such an extent as this are unlikely.

Does this mean "FTL travel" is impossible? Absolutely not, there are hypotheses of ways of getting around this fundamental limit via travelling through separate dimensions such that rather than actually travelling at a speed exceeding c, you instead cut the distance between 2 points in space-time via a different "route". Very sci-fi sounding, but so many things previously thought fiction are now very much reality.

 

[FoxEye]

Yes thats what ime saying!!

If if you "stopped" the earth continued as it always has what would the differnce in time be.


We know how to work it out as GPS satelites adjust for the fact time is slower for them, we've stuck atomic clocks on aeroplanes and spacestations and seen the tint differnces as a result.

I suppose what tim asking is how fast are we going (obvioudly this will change as times our orbit will say counter our spin) but assuming everything lined up so our maximum possible speed (and maybe our minimum) it would be interesting to see how much we are slowed in time by our speed.

Despite of course 1 second being perceptibly as fast in either reference.

You can't work out "absolute speed" by any means. It's a meaningless phrase. There is no reference point, hence no absolute speed. For all we know the entire universe could be moving at billions of miles per second in any direction, or flipping end over end, or...

We only have any speed at all relative to something else.

 

[d_brennen]

All our current theories are probalbly wrong in some sense, simply becasue that's how theories work. You make an assumption, test it, if it's right happy days, if not, make a new theory and test again

New data pops up from time to time and puts theories at risk - no bother, re-theorise and continue

Also, for some reason made me though of this

 

[Tombstone]

Now that's not impossible, we've been wrong before, but the chances of us being wrong to such an extent as this are unlikely

I'm happy with unlikely, that means that there is a chance that we are wrong. I'm quite content with that

 

[Tefal]

You can't work out "absolute speed" by any means. It's a meaningless phrase. There is no reference point, hence no absolute speed. For all we know the entire universe could be moving at billions of miles per second in any direction, or flipping end over end, or...

We only have any speed at all relative to something else.

Ok if we assume the universe is expanding equally in all directions the point which remains in the absolute center of the expansion can be taken to be "fixed" or at least fixed for the frame of refernce for our entire universe whixh frankly will do for my curiosity,


Compared to this point what is the relative speed of the earth at ots maximum and minimum and thus we could see vaugly the relative range of time dilation we all experience

 

[new boy]

Thats because I am not attempting to prove otherwise , all I am attempting to do is suggest its a possibility.

Its just not good enough mte, we have provides strong evidence to prove our side, its only fair we expect to see strong evidence for your side, otherwise how can we take it seriously?

 

[PhysicsMan94]

Ok if we assume the universe is expanding equally in all directions the point which remains in the absolute center of the expansion can be taken to be "fixed" or at least fixed for the frame of refernce for our entire universe whixh frankly will do for my curiosity...

Actually that's a bit of a misconception. When we say the universe is expanding, it does not mean it is expanding from a point outwards into "something", but rather all of space-time itself is expanding. To even consider it as expanding into "something" is erroneous as there is nothing "outside" the universe (the word outside doesn't even make sense when considering the universe itself).

So with said, it is not really accurate to say there is a fixed point anywhere in the universe as all points are expanding.

 

[wildman]

You can't work out "absolute speed" by any means. It's a meaningless phrase. There is no reference point, hence no absolute speed. For all we know the entire universe could be moving at billions of miles per second in any direction, or flipping end over end, or...

We only have any speed at all relative to something else.

the universe is moving in all directions all the time as it is constantly expanding. This is a measurable via redshift calculations which enable you to understand how fast a galaxy is moving away from your point of observation. Redshift from what I remember studying doesn't have any units it's just a number which allows you to understand how the universe is expanding. Might need to dig out my old physics books as i remember doing a boat load of this when studying planetary science

 

[Tombstone]

Its just not good enough mte, we have provides strong evidence to prove our side, its only fair we expect to see strong evidence for your side, otherwise how can we take it seriously?

Its not my side, I am just a gamer, I'm not a quantum physicist, I have no background in science, my thoughts and opinions carry absolutely no weight in the world, or even on this very limited forum. I am not championing a cause or attempting to win a contest here, whether anyone takes my meandering thoughts seriously is of no consequence to anyone on this forum, its just one nerd talking late night on a forum to another, to pass the time. If I really knew about this stuff, I wouldnt be doing the job I do in life and I most certainly wouldnt be discussing it on the General Discussion forum of a retail company

In Star Trek terms, if you know the episode, I am Data playing the game against the tactical genius who ended up getting angry because Data wasnt playing to win

 

[d_brennen]

Like the balloon analogy. If you were sat on the surface of a giant ballon that was inflating, all points on the surface of the baloon are moving away from your relatively fixed position, except space isn't a flat plain

 

[wildman]

Ok if we assume the universe is expanding equally in all directions the point which remains in the absolute center of the expansion can be taken to be "fixed" or at least fixed for the frame of refernce for our entire universe whixh frankly will do for my curiosity,


Compared to this point what is the relative speed of the earth at ots maximum and minimum and thus we could see vaugly the relative range of time dilation we all experience

there is no fixed centre point though, only points from which your observations are taken.

 

[Threepwood]

the only problem is you need a DeLorean and someway of producing 1.21 jigawatts of electricity to get there......................

1.21 gigawatts??!!

Great Scott!

Or warp.

Aye. But you can't warp to anywhen, that is just absurd. You can't change the laws of psyics you know.

 

[Destination]

there is no fixed centre point though, only points from which your observations are taken.

This is something I have ponderd, if there is no fixed centre so to speak, and we see doppler red on most galaxies, very few are moving towards us, mostly moving away, how can it be that it doesn't trace back towards some type of centre.

Everything can't be moving away from everything else, without it having some sort of middle towards which little or nothing is moving.

 

[PhysicsMan94]

This is something I have ponderd, if there is no fixed centre so to speak, and we see doppler red on most galaxies, very few are moving towards us, mostly moving away, how can it be that it doesn't trace back towards some type of centre.

Everything can't be moving away from everything else, without it having some sort of middle towards which little or nothing is moving.

As someone pointed out earlier, an expanding balloon or sphere is a good analogy - all points on the sphere expand but there is no "centre" of expansion. The centre of the inside of the sphere is not applicable as that would be "outside" of the universe in our analogy which makes no sense in this context.

It's difficult to picture, but one has to remember that when we are speaking about the universe itself we are not just dealing with a simple flat 2D topology.

 

[Destination]

Indeed, but balloon theory I can understand, as it still has a centre, our universe is 4D afaik from the pov of expansion.
The balloon might expand itself, but there still exists a centre, not on the surface of the balloon, but it is still there.

So do we have a 'centre' or not? Is our centre simply based inthe time dimension?

 

[PhysicsMan94]

The balloon might expand itself, but there still exists a centre, not on the surface of the balloon, but it is still there.

Exactly, in the case of the balloon analogy the centre of expansion is not on the surface - extended that to the universe (and noting that this analogy is, of course, just a guideline and not precise) means that the "centre of expansion" lies outside of the universe itself. But "outside" in the context of the universe makes no sense - it doesn't exist.

Thus, there is no true "centre" of the universe. Remember that at t = 0 (the instant of the big bang), the entire universe was a singularity and so you could assert that at this point the entire universe was the centre.

 

[asim18]

Is it better to think of the universe as "decreasing in density" rather than "expanding"?

 

[V F]

1.21 gigawatts??!!

Great Scott!

 

[aardvark]

According to Prof. Brian Cox (and I tend to agree with him), yes it does. Everything that has ever happened at some point still exists somewhere in spacetime.

Cox says a lot of garbage with not a shred of evidence to back it up.

 

[Cosimo]

That's enough thinking for one night, it's time to retreat back to the earwax thread I think.

It's too much to contemplate over breakfast, back to watching the birds.