Thread: The Hubble Ultra Deep Field in 3D

Please take the time to watch this.

Great vid. One comment by the narrator is puzzling to me.

Galaxies, some of which are "traveling at greater than the speed of light". Thought this was not possible?

Originally Posted by Norton

Great vid. One comment by the narrator is puzzling to me.

Galaxies, some of which are "traveling at greater than the speed of light". Thought this was not possible?

I am not sure Norton. Yet I am no expert.

Originally Posted by bsnub

Yet I am no expert.

Nor am I so I defer to Einstein.

From the first vid:

"Photons that have been traveling for over 13 billion years"

Amazing stuff, thanks for posting.

Good OP bsnub, very interesting stuff mate

Well done norton. Nice find bsn00b

Originally Posted by Norton

Just did some checking and sure enough, the narrative is likely correct. Other galaxies may be observed to be moving at greater than light speed because telescopes measure speed relative to the speed of the observation point and the observed point. So, closing or opening speed is the sum of the speed of both and could well be greater than the speed of light.

Don't think that can be correct as the observation point is basically fixed. A sattelite orbiting the earth will still be moving at a reltive snails pace around earth in terms of light.

The speed that a galaxy is moving away is measured by the shift in wavelength. If a galaxy was moving faster than the speed of light the light would never reach the observer and thus the wavelength of the light could not be measured.

I would advise all to read a great book by the late Carl Sagan titled "Cosmos". Humbling stuff.

A useful link on faster than light phenomena...

Faster Than Light

I find this all very fascinating.

If you look inside yourself, you'll understand the universe

Originally Posted by StrontiumDog

Originally Posted by Begbie

Originally Posted by Norton

Just did some checking and sure enough, the narrative is likely correct. Other galaxies may be observed to be moving at greater than light speed because telescopes measure speed relative to the speed of the observation point and the observed point. So, closing or opening speed is the sum of the speed of both and could well be greater than the speed of light.

Don't think that can be correct as the observation point is basically fixed. A sattelite orbiting the earth will still be moving at a reltive snails pace around earth in terms of light.

The speed that a galaxy is moving away is measured by the shift in wavelength. If a galaxy was moving faster than the speed of light the light would never reach the observer and thus the wavelength of the light could not be measured.

A useful link on this subject

Apparent Superluminal Velocity of Galaxies

Apparent Superluminal Velocity of Galaxies

A distant object can appear to travel faster than the speed of light across our line of sight, provided that it has some component of motion towards us as well as perpendicular to our line of sight. Say that on January 1st you make a position measurement of galaxy X. One month later, you measure it again. Assuming you know its distance from us by some independent measurement, you derive its linear speed, and conclude that it is moving faster than the speed of light.

What have you forgotten? Let's say that on January 1st, the object is Dkm from us, and that between January 1st and February 1st, the object (which is actually moving at 45 degrees to the line of sight) has moved dkm closer to us. You have assumed that the light you measured on January 1st and February 1st were emitted exactly one month apart. Not so. The first light beam had farther to travel, and was actually emitted (1 + d/c) months before the second measurement, if we measure c in km/month. The object has travelled the given angular distance in more time than you thought. Indeed, we can calculate that if its real velocity is v, then its apparent velocity in this case is v/[sqrt(2)-(v/c)] which could be higher than twice the speed of light without v being greater than c. For galaxies moving at more acute angles to the line of sight the apparent velocity can be much higher. Similarly, if the object is moving away from us, the apparent angular velocity will be too slow, if you do not correct for this effect, which becomes significant when the object is moving along a line close to our line of sight.

The effect has been observed in the radio emissions from jets of quasars which are thought to travel close to the speed of light in a direction near to our line of sight.

Awesome! We are on to something here. Here is another great one;

Originally Posted by Norton

Great vid. One comment by the narrator is puzzling to me.

Galaxies, some of which are "traveling at greater than the speed of light". Thought this was not possible?

Relativity.

If I move away from you at 2/3 the speed of light, and you move away from me at 2/3 the speed of light, either of us appear to be moving away at greater than the speed of light, yet without ever individually surpassing the speed of light.

Additionally, the narrator explains in the sequence following that the expansion of the universe additionally contributes to this perception (which is why it is possible for some objects appear to move at greater than 2x the speed of light).

Originally Posted by Begbie

The speed that a galaxy is moving away is measured by the shift in wavelength. If a galaxy was moving faster than the speed of light the light would never reach the observer and thus the wavelength of the light could not be measured.

Wrong - a galaxy moving at faster than the speed of light would still generate photons that are left behind, and that leave it at the speed of light. Just because the galaxy moves at speeds beyond c does not mean it 'captures' its own light - only black holes are known to do that, and that's not the case here.

Originally Posted by teddy

If you look inside yourself, you'll understand the universe

Useless, as always.

Anyway if that was the position 13 billion years ago it's fair to say they are long gone by now, that's what really freaks me out, we are looking at things who have been gone for a very long time, and our sky if we could get an instant photo of real time positions, would look vastly different. That is to me a real strange thing to come to terms with when everything else we look at is more or less where we see it.

When you lie down and look up at the night sky most of what you see is the distant light of things as they once was, very strange

Originally Posted by larvidchr

Anyway if that was the position 13 billion years ago it's fair to say they are long gone by now, that's what really freaks me out, we are looking at things who have been gone for a very long time

Essentially, what we consider 'present day', whenever we are looking up, is actually ancient (VERY ancient) history.

We are always living in the past, ever second of our lives -- just in the case of our 'reality', the time lag is short enough to allow us to fool ourselves.

Now, try to align that awareness with the illusion of 'free will'.

Tanks for the OP and the Video

Originally Posted by StrontiumDog

Apparent Superluminal Velocity of Galaxies

Very interesting read.

One point the author seems to have gone wrong though IMHO.

Shadow and Light spots

Shadow and light spots are described like objects that move. They are not objects and the observed speed therefore is not the speed of an object. He makes clear at the same time that both are not methods of transferring information so it is really ok.

Very interesting the
Quantum tunnneling effect.

The scientists who performed the experiment even claimed that they transferred information faster than light. But this description explaines why that is not worth much and is probably wrong.