Food for thoughts.

[Dave 123]

@Drago you state that nothing can travel faster than light. Don’t you remember Blazed, who is so fast he can’t communicate with us anymore?

 

[Moon bunny]

When you say “intelligent life will wipe itself out” How intelligent is intelligent? Earthworm level?. Butterfly? Slow worm? blackbird? Mouse? Dog? Cat? Squirrel monkey?
A very few technologically advanced (not the same as intelligent) humans have developed the ability to wipe out just about all life on Earth, but the vast majority haven’t, couldn’t, and wouldn’t. Perhaps on other planets sanity has prevailed.

 

[markemark]

When you say “intelligent life will wipe itself out” How intelligent is intelligent? Earthworm level?. Butterfly? Slow worm? blackbird? Mouse? Dog? Cat? Squirrel monkey?
A very few technologically advanced (not the same as intelligent) humans have developed the ability to wipe out just about all life on Earth, but the vast majority haven’t, couldn’t, and wouldn’t. Perhaps on other planets sanity has prevailed.

Any society than can create the tech to transmit data will very shortly be able to wipe themselves out. Few thousand years. As a percentage of the 14odd billion years the universe has been around that thousand years is vanishingly small to conincide with another.

Should the signals we transmit be revived by another civilisation, by the time it gets there we’ll all be wiped out. By the time their reply comes back to the human less earth, they’ll all be wiped out.

 

[Ming the Merciless]

The warping of space time due to massive objects does not enable faster than light travel.

NASA on lensing and dark matter

https://science.nasa.gov/universe/how-gravity-warps-light/

Summary of recent theoretical research

https://physicsworld.com/a/spacecra...ld-travel-faster-than-light-claims-physicist/

Actually you can. Space time itself is expanding faster than the speed of light. Speed of light is a governor within Space Time, not of Space Time.

Speed limits is special relativity and it applies to what we call local physics. For objects the other side of the universe General relativity applies, and in this latter theory there are no speed limits.

 

[Ming the Merciless]

Plus we need to consider quantum entanglement. In theory there are no distance limits to how close particles need to be for entanglement to work. Aliens may be quite busy communicating across vast distances via quantum entanglement and us primitive earthlings won’t have a clue.

i would not be so arrogant as to assume our Science has reached its pinnacle of understanding or application. We are but babies.

 

[Dogtrousers]

I'm heartily suspicious of the argument that "intelligent life will wipe itself out", or the SETI lot listening for transmissions from "intelligent life". It's hopelessly anthropocentric and far too influenced by Star Trek. At least Star Trek had the excuse that the aliens should look like people with minor prosthetics - it was cheaper to cast actors that way. I'm similarly suspicious of anything involving space travel, especially human crewed space travel.

I would say that people watch too much Star Trek, but really that's impossible. You can never have too much William Shatner. That's a physical impossibility.

 

[SpokeyDokey]

The furthest objects detected are estimated over 13 billion light years away.

They are much further away than that due to the expansion of Space.

Around 46.5 billion light years.

Aa determined by red shift analysis of starlight that started its travel some 13.8 billion years ago.

 

[roubaixtuesday]

They are much further away than that due to the expansion of Space.

Around 46.5 billion light years.

Aa determined by red shift analysis of starlight that started its travel some 13.8 billion years ago.

We are using different definitions of distance

https://explainingscience.org/2021/03/13/distances-in-cosmology/

 

[lazybloke]

Nothing can travel faster than light, at least with the current understanding of physics. The faster physical object travels the heavier it becomes, until it becomes infinitely heavy at the speed of light. It is not possible to provide infinite thrust via conventional means, making light speed travel impossible.

You need to set aide the conventional comcept of "travel", or distance, time and therefore velocity. Manipulating the structure of space-time would be circumventing those extreme distances insted of actually traveling them in full. Think of it as taking the lift - the conventional route might be walking round and taking the stairs which could be a journey of hundreds of feet, but the lift takes you to the same destination for a journey of 10 feet. Or in one possible scenrio the lift wohld remain stationary while the building itself moves up ormdkn around us. So using my theoretical suggestion we would be taking taking an extreme shortcut, possibly even at zero relative velocity by manipulating space around us as we remain in place, rather than actually travelling ourselves.

As aforementioned by my good self, we know the structure of space time can be affected (or manipulated if you will) by mass and gravity because we see it in nature - there are no physical laws being broken. However, humankind will likely never be able to manipulate it for ancillary reasons such as energy budget, etc (energy budget being my favourite objection, did some of the maths for that for my Masters - we'd have to likely harness the energy of galaxies worth of stars, which seems unlikely in the extreme.)

But just because we may never be able to do it doesn't mean physics won't permit it...because we can clearly see with a telescope that it does.

You mean it won't be such a long way down to the chemist?

 

[SpokeyDokey]

We are using different definitions of distance

https://explainingscience.org/2021/03/13/distances-in-cosmology/

Are we?

I thought the discussion was about the actual size of our observable universe ie the current distance to the furthest objects that we can see.

The comoving size of our observable universe has an actual diameter of around 93 billion light years. Hence 46.5 billion light years is the actual distance from Earth to those furthest objects; even though the light from those objects has taken 'only' 13.8 Billion years to arrive at Earth.

https://en.wikipedia.org/wiki/Observable_universe#:~:text=The comoving distance from Earth,8.8×1026 m).

 

[roubaixtuesday]

Are we?

I thought the discussion was about the actual size of our observable universe ie the current distance to the furthest objects that we can see.

The comoving size of our observable universe has an actual diameter of around 93 billion light years. Hence 46.5 billion light years is the actual distance from Earth to those furthest objects; even though the light from those objects has taken 'only' 13.8 Billion years to arrive at Earth.

https://en.wikipedia.org/wiki/Observable_universe#:~:text=The comoving distance from Earth,8.8×1026 m).

Yes the original discussion was about the time light from distant civilisations would take to get to us.

The objects' distance, as set out in link you post can be described in this way (light travel distance) or by your preferred measure. They're not inconsistent, just different. Both are valid.

 

[SpokeyDokey]

Yes the original discussion was about the time light from distant civilisations would take to get to us.

The objects' distance, as set out in link you post can be described in this way (light travel distance) or by your preferred measure. They're not inconsistent, just different. Both are valid.

The OP was about the size of the Universe in light years. The value was wrong, though.

The actual distance is 93 Billion light years ie the size of our observable universe. (Even though it is obviously not the value for the entire universe.)

Light travel time distance is not the same and it confuses by failing to recognise redshift and the expansion of Space itself.

https://astro.ucla.edu/~wright/Dltt_is_Dumb.html

I'll leave it there.

 

[roubaixtuesday]

The actual distance is 93 Billion light years ie the size of our observable universe

Yet from your own link

The Universe is homogeneous and isotropic, so it has no edge. Thus there cannot be a maximum distance

we're just describing the same thing on different ways.

 

[SpokeyDokey]

Yet from your own link

The Universe is homogeneous and isotropic, so it has no edge. Thus there cannot be a maximum distance

we're just describing the same thing on different ways.

I didn't say it had a maximum distance. I just stated the size of our observable universe.

As per the UCLA link I provided there is a lot of confusion caused by the information, oft reported, via media channels.

The same happens re the edge of our observable universe. It is simply an edge caused by happenstance. It does not signify the end of the universe in totality. Clearly there are many observable universes each depending on the observation point. Hence, there will be many more galaxies beyond what we are able to observe. Media reports ignore these facts too.

An interesting field of study and one which I wish l knew, and understood, a whole lot more about!

 

[Dogtrousers]

The Universe is homogeneous and isotropic,

Or is it ...

That's the Cosmological Principle but my feeble understanding is that it's a basic assumption but some evidence tends to argue against it (big galaxy clusters, big voids and other inhomogeneities)

Anyway, there are some things that are brick walls that we cannot see past. The boundary of the observable universe is one of them. They are unknowable so there's little point worrying about it.