Chasing light speed

[Rick Petrie]

I'm glad you sorted me out on that one Steven.

[gmbfilter (Geoff)]

The more follow this thread the less I follow this thread

Since both spaceships are in the same frame of reference, everything is normal, lights work backwards and forward, and bullets do what they do.

For anyone in a different frame of reference eg IIS things would appear quiet different to what the crew on spaceships perceive.

A good physicist should be able to explain it, a couple of belts of wild turkey makes it all seem OK

[sjastro]

Originally Posted by gmbfilter

The more follow this thread the less I follow this thread

Since both spaceships are in the same frame of reference, everything is normal, lights work backwards and forward, and bullets do what they do.

For anyone in a different frame of reference eg IIS things would appear quiet different to what the crew on spaceships perceive.

A good physicist should be able to explain it, a couple of belts of wild turkey makes it all seem OK

You would be correct only if the spaceships were travelling at less than the speed of light.

Since this thread was based on spaceships travelling at the speed of light (which of course is impossible) the scenario is very different. The spaceships will behave as photons. There is no front, back, gap or any specific spatial characteristic that can be assigned to photons.

Regards

Steven

[Karls48 (Karl)]

Hi Geoff, is not modern cosmology and theoretical physics wonderful? It can explain everything in whole universe.
So our two ships are receding from the Earth at speed of light or even faster. It seems to be confirmed observable fact (based on red shift) that more distant the galaxy is, faster it will recede from us. At some distance it will recede from as at speed of light and faster. If we take some distant galaxy that is receding from us at 70% of light speed and launch our spaceships at 35% of light speed from there, those ships would be travelling faster then the light relative to the earth and therefore backwards in time. Impossible, according to theory of Relativity. Relative to the galaxy the ships started from, nothing special will be taking place. This scenario (and some other things like massive monopoles that supposed to exist just after Big Bang) would render theory of relativity invalid. To salvage the theory our wonderful scientists invented assumption that the space itself is expanding. Not proven by any experiment, except other assumption that speed of light is constant in vacuum and ultimate speed that anything can move. So although some object in the universe appears to travel faster then light, according to current scientific dogma those object are travelling slower then speed of light but space between it and the Earth is expanding and therefore it appears that it is travelling faster then light. Well. Because of obvious problem with this assumption (the Earth and the rest of the solar system planets should be getting farther apart from each other) space expands only between objects that are not gravitationally bound. As no one come up yet with explanation of mechanisms that cause such a phenomena scientist have to invent other mysterious things as Dark Matter and Dark Energy. So we have Space that can be bend (curved), stretched, compressed (as it did not existed before Big Bang so it must be either compressed inside of object that exploded as Big Bang or created by some sort of conversion of matter/energy to space). It is then logical to assume that it can be also converted back to what it was before Big Bang. Where the Theory of Relativity stands on this? What is the speed of light in Dark matter?
At any given point in time in our history the intellectual elite of the society (shamans, priests, scientists) was absolutely convinced that they have all the answers to everything that is surrounding us, that what we consider as Universe today. And almost without exception their observations on which they based their conclusions were based on assumption that the earth is the centre of the Universe. Nothing really changed even today. We assume that basic law of nature that we observe here are universal and work everywhere. Well what about the Black holes? According to the scientists the laws of nature will break down inside of black hole and cannot work as they do elsewhere in the Universe. So logically – either Black holes don’t exist or universality of laws of nature is wrong.
Back to our two spaceships. The Enterprise is chasing Kiligons spaceship. Relative to the Earth the ships are receding at 105% of light speed but because of space expansion assumption they move only at 35% of light speed and therefore they exist as real object. From ships frame of reference ships are 500m apart and nothing unusual is taking place. Booth ships main weapons systems and engines are damaged so Capt. Kirk finds somewhere old M16 and order Scotty to mount the rifle in ships nose. Kiligons do same mounting similar rifle in rear section of their ship. Ships commence firing on each other. With every shot the Enterprise fires, rifle recoil will slow it down. Every time the Enterprise is struck by Kiligons bullet it will slow down even more. Exactly opposite will happen to Kiligons ship as they fire on Enterprise and are struck by the bullets from Enterprise. They will accelerate away from the Enterprise. Eventually the Enterprise will not be able to hit Kiligons ship as it will be moving faster then the bullets fired from the Enterprise. Also both ships will not be able to hit each other as the distance between them increase. No rifle will shoot consistently in same spot, the spread of shots over the large distance will cause bullets to miss. That’s applied science and it works. Theoretical science, especially in cosmology requires one important element. You have to believe in what it is telling you. Well, you may just as well believe in creation.
And one last thought about the high mathematics. Mathematicians can calculate temperature and size of the Universe milliseconds after the Big Bang (among other amazing things). Just ask them to calculate flip of the coin (head or tails). They will fail miserably. Although such event is taking place in same universe and is influenced by same law of nature with enormously smaller number of variables and possibilities. Make your conclusion about such mathematical proofs.

[Rick Petrie]

I like your assumptions Karl. There are just too many questions about our Universe that are unanswered and who is right and who is wrong?.

[sjastro]

That's quite a tirade Karl.

A ship travelling at 35% light speed towards a galaxy, will be travelling at that speed irrespective of the recession velocity of the galaxy.

The recession velocity of the galaxy is based on the expansion of space-time coordinates. The velocity of the ship is based on local coordinates which are independant of space-time expansion. You can't add both velocities.

I'll leave it at that.

Regards

Steven

[gmbfilter (Geoff)]

Ladies and Gentleman,

Google up "The relativity express "
There is some great stuff
especially on u tube.

Don't miss "Do-it-Your-Self-Relativity " Parts 1 and 2

Pay attention, there will be a short quiz

Simultaneity is also cool

Paradoxes only seem that way!

[Jeff]

Originally Posted by Karls48

If Big Bang theory is correct the only meaningful measurement of time, motion and distance is referencing it to the point in the universe where the Big Bang occurred, (and the time and space come to existence).

Is there a known point in the universe where the Big Bang occurred?

My current understanding is that we have a viewable horizon which is fairly homogeneous in every direction such that we are close to the centre of the observable universe. However, the observable horizon from an outlying galaxy would be completely different ... and it would appear to be at the centre of its observable universe.

Can a Big Bang Origin point be deduced (eg. from the CMB dipole and the modelled inflation/expansion history of the universe), or it a meaningless concept becasue the origin has expanded and is therefore now all around us? I understand that the CMB dipole for the solar system is estimated to be 368 km/sec ... can we draw any implications from this?

[sjastro]

Originally Posted by Jeff

Is there a known point in the universe where the Big Bang occurred?

Can a Big Bang Origin point be deduced (eg. from the CMB dipole and the modelled inflation/expansion history of the universe), or it a meaningless concept becasue the origin has expanded and is therefore now all around us? I understand that the CMB dipole for the solar system is estimated to be 368 km/sec ... can we draw any implications from this?

Jeff,

It's meaningless because the implication is that the universe was created in existing space. Space-time was created at the BB. From a topological perspective any point in the universe can be considered the "centre".

Regards

Steven

[MrB (Simon)]

Blah, thats like saying a falling tree doesn't make sound because no one is around to hear it.

Forget what was, or wasn't, there before.
Once there were no landmarks on earth, and no possitioning relative to them. Relative possitioning is done now, but using you're logic that shouldn't be possible, because those landmarks once weren't there and neither was our concept of space and distance etc.
There is matter now, and we should be able to find the point of origin of the expanding bubble.
We now have a reference, all the observable galaxies, so where is the origin(referenced to observable/mappable galaxies) that the red-shifted galaxies are moving away from?

[sjastro]

Originally Posted by MrB

Blah, thats like saying a falling tree doesn't make sound because no one is around to hear it.

Forget what was, or wasn't, there before.
Once there were no landmarks on earth, and no possitioning relative to them. Relative possitioning is done now, but using you're logic that shouldn't be possible, because those landmarks once weren't there and neither was our concept of space and distance etc.
There is matter now, and we should be able to find the point of origin of the expanding bubble.
We now have a reference, all the observable galaxies, so where is the origin(referenced to observable/mappable galaxies) that the red-shifted galaxies are moving away from?

Your line of reasoning contradicts the Cosmological principle. If you use red shift to calculate the origin you will find the BB to have occurred in your own backyard.

Red shifted galaxies are moving away from you, or from an observer from any point in the Universe. Doppler red shift is not an absolute parameter but is relative to the position of the observer.

At the scale of the universe, galaxies are essentially evenly distributed. This is a direct consequence of space time expansion which makes the universe homogenic and isotropic.

If you want to use a bubble analogy think of the universe as the surface of the bubble rather than its volume. You will find that every point on the surface is moving away from every other point as the bubble expands. There is no specific origin.

Regards

Steven

[Rick Petrie]

Originally Posted by sjastro

If you want to use a bubble analogy think of the universe as the surface of the bubble rather than its volume. You will find that every point on the surface is moving away from every other point as the bubble expands. There is no specific origin.

Regards

Steven

Yes there is - The centre of the bubble, easy.

[sjastro]

Originally Posted by Rick Petrie

Yes there is - The centre of the bubble, easy.

I'll assume the wink face is sarcasm.

[Rick Petrie]

Sorry Steve, Just my warped sense of humour. Couldn't help myself.

[MrB (Simon)]

Originally Posted by sjastro

Your line of reasoning contradicts the Cosmological principle.

Never heard of it, so it's somebody else's problem... hehe

If you use red shift to calculate the origin you will find the BB to have occurred in your own backyard.

Red shifted galaxies are moving away from you, or from an observer from any point in the Universe. Doppler red shift is not an absolute parameter but is relative to the position of the observer.

True. You can probably tell I've never read/learnt anything about this and I'm kinda making it up as I go along.
The furthest galaxies are moving at the same speed aren't they?
Does the level of redshift vary between these galaxies or is it the same for all?
I suppose if the observer(us) is too close to the 'origin', or the galaxies are at such distance that we appear to be close to the 'origin', then the delta-redshift (redshift's-shift(!)) between each galaxy would be minimal.
But assuming the observer is sufficiently removed from the origin, then the amount of redshift each galaxy has, their apparent speed, would be an indication of angle of movement relative to the observer?

At the scale of the universe, galaxies are essentially evenly distributed. This is a direct consequence of space time expansion which makes the universe homogenic and isotropic.

Not from the 3d plots/maps I've seen, there are clusters and strings and swirls etc etc. The position of the galaxies relative to each other is of no consequence anyway, only their true velocity/apparent velocity and the vector calculated(if possible?) from them.

If you want to use a bubble analogy think of the universe as the surface of the bubble rather than its volume. You will find that every point on the surface is moving away from every other point as the bubble expands.

Yep true, but again, observed from any point within the bubble, (or outside for that matter) other than the 'origin', the velocity of the surface at any point other than those perpendicular to the observer, will have different apparent velocities due to the angle of observation.
I failed physics at high school, it bored me shickless, but do remember vector diagrams... these should apply here right?

There is no specific origin.

Regards

Steven

Ofcourse there was, we just havent found it yet.
Hope my dribble above makes sense?

[sjastro]

Originally Posted by MrB

The furthest galaxies are moving at the same speed aren't they?
Does the level of redshift vary between these galaxies or is it the same for all?
I suppose if the observer(us) is too close to the 'origin', or the galaxies are at such distance that we appear to be close to the 'origin', then the delta-redshift (redshift's-shift(!)) between each galaxy would be minimal.
But assuming the observer is sufficiently removed from the origin, then the amount of redshift each galaxy has, their apparent speed, would be an indication of angle of movement relative to the observer?

There is a linear relationship between redshift and velocity (and distance) between the observer and galaxy provided the galaxy is not gravitationally influenced. If the furthest galaxies are at the same distance from the observer they will have the same velocity and redshift.

If galaxies are not gravitationally influenced they will not have an apparent speed nor travel at an angle different to the line of sight of the observer.
The point is that galaxies don't travel through space, they are in a fixed position and are swept along by the expansion of space time. Since space time expands in all directions galaxies are always in the line of sight of the observer.

If galaxies are gravitationally influenced such as being part of a cluster things are more complicated. The red shift/distance/velocity relationship is not as straightforward. The motion may no longer be in the line of sight of the observer and may even be approaching the observer. That's were your vector diagrams will come into play.

Originally Posted by MrB

Not from the 3d plots/maps I've seen, there are clusters and strings and swirls etc etc. The position of the galaxies relative to each other is of no consequence anyway, only their true velocity/apparent velocity and the vector calculated(if possible?) from them.

The 3D slices only represent a small percentage of the Universe. Due to the isotropic nature of the Universe an astronomer ten billion light years away will find the same sort of configurations in their own maps.

Originally Posted by MrB

Yep true, but again, observed from any point within the bubble, (or outside for that matter) other than the 'origin', the velocity of the surface at any point other than those perpendicular to the observer, will have different apparent velocities due to the angle of observation.
I failed physics at high school, it bored me shickless, but do remember vector diagrams... these should apply here right?

The surface of the bubble was meant to be an analogy for the expansion of the Universe nothing more. I'm sorry I raised the issue.

Originally Posted by MrB

Of course there was, we just havent found it yet.
Hope my dribble above makes sense?

You queries are perfectly sensible.

Regards

Steven

[MrB (Simon)]

Heh, I'm enjoying this discussion, however, the more I read your understanding of the universe, the less I understand it.
And I suspect the same for you and mine?!

BTW, I was aware of the 'bubble' analogy, in my view it makes no difference, if it suits you, replace the 'surface' with the most distant observable galaxies.

[sjastro]

What I understand is the common misconception that the Universe was created in existing space. Then you can pinpoint the origin by retracing the steps.

Unfortunately there are some dire consequences on the way, galaxies can travel faster than light, but then again they probably not, as matter would have collapsed onto itself long beforehand.

Regards

Steven

[MrB (Simon)]

Sorry, haven't time to reply in length, but I get the feeling we're both doing a little of this:http://www.clipartof.com/images/emot...all2/1920_.gif

I'll add this to my growing list of other POV's(religion, politics, war, nuclear power etc etc etc) I don't understand.

edit: I have no idea why the forum is converting an icon and image BBCode tags into a link?!.... icon shows fine in post-preview.... and in edit.

[skwinty (Steve)]

Originally Posted by sjastro

What I understand is the common misconception that the Universe was created in existing space.

What I find extremely difficult to understand is the concept of space not existing prior to the big bang. If space was created at the time of the big bang, what was space expanding into, if not more space.