Space In General

[occasionalracer]

I don't have too much knowledge of the forces and all the mathematics that are balancing out our solar system, but I just think it's incredible how unbelievably advanced humans have become in the last half century.

It's quite fascinating that there are all these other planets, and that we know so much about their composition, even though we haven't been there. I am sure there are perhaps living creatures or organisms on some of the planets, but as far as any alien life that is capable of similar or far more advanced technology and engineering than we are, to build a spacecraft and jet over to planet earth and snatch up humans and take them away, is absurd!

I mean to think about how old the earth is and know how many billions of years it took evolution to create humans, and more importantly the way the human brains memory works, has to be a such a stroke of luck (if you will).
So it could easily be another couple of billion years until any alien life is blessed with such enormous capability to construct spacecrafts from existing materials they may have on their planet and land here to visit us.

I'd be much more concerned about the forces on earth, and the high chances of a massive natural catastrophe, that we cannot foresee.

 

[Moot]

I agree it is amazing how advanced we have become, but still humbles me when I think how a common cold can still kill us. We are almost as fragile as ever, looking at it as a whole, it looks like our evolution although statistically adding years to out lifespans, the main progression is through applications of physics rather than biology/chemistry to improve our lives. I'm not complaining, I just want us to be good at everything.
Eventually a god will be wishing he knew as much as we do and will be wondering how we do things as it will be beyond his comprehension.
There is nothing in the laws of physics that says we can not build from scratch our own planets out of harvested mass and once formed to our liking seed it with biological forms.
It just a case of resources and tech. Child's play, the tough stuff will be out of bounds for any sentient spiritual entity.

 

[Keef]

It seems like as we advance intellectually, we grow weaker in other areas, particularly biologically. Luckily our intelligence has led to the development of all sorts of drugs that have our backs, but without them, and with the habits that many people have these days, we'd be helpless without them.

 

[Moot]

There will be a tipping point at some time in the future when a whole load of worries facing humanity disappears. That will be when we know how to perform conciousness transplants.
I read a little about it recently. Experts are confident that it will be done at some point, as there is no mysterious unknown or any reasons on why it can not be done, it's just science method at the end of the day (there is no evidence of any spirit or unexplained factor of conciousness to what makes you, you, it's just complex information). But what they do say as perhaps as unlikely to be achievable it to swap your conciousness to know for example what it's like to be a bat. What does it feel like to be a bat, and only a bat and nothing else. I can see their point but I still can think of how it could be done. But it's just when you go back to being your normal conciousness, the previous experience would not exist anymore, and any memory swapped back would only just be that, a memory with your own interpretation, and not of what it was like to actually be a bat with a bats conciousness.
There could be a hybrid conciousness, but it would not be true and might get messy.

For now we just have dreams.
Incidentally last night I had a dream where for a (too) short time I was a Peregrine Falcon, it was great. Swooping around, flying high and spotting each individual bird that was also in the area, I scared some pigeons, I didn't make a kill, but I remember being a bit wary of hurting myself if I went for a kill by going in at speed and making contact.
Who knows what a real Falcon thinks and feels, but I think my mind did a pretty good job. The only unreal thing occurred when I decided to chase a commercial passenger jet that was flying low. I gave up. Also while in flight saw a golden eagle, and used both my wing tips to point it out to my human father below on the ground. That was a perfect human/hybrid dream discrepancy occurrence.
A bit like how we can perhaps never escape ourselves unless we erase them and start again.

 

[Vince_Fiero]

I don't think the Milky Way orbits anything, but It's getting closer to Andromeda galaxy at about 120km/s or 268,000mph , which means contact in 3-5 billion years time.

Most astronomers would agree with this, since it might imply the universe itself is rotating, an idea which astronomers are very reluctant to allow.
...

Respectfully,
Steve

Back to space:

1) I do believe there is a lot of emptiness (no matter), although with the mass–energy equivalence any light going through makes it not empty?

2) on the above quotes, we are trying to explain things too simple. The curved space (gravity as a curvature of spacetime) is a difficult reference for us.
I certainly still have trouble getting all the details and I believe most of the advanced scientists do too, it will take some more revolutionary theories (probably when Einstein's theory fails) before the common scientist (not even a common man like me) will understand the full impact of space - time bending, read these as an example:
http://chongonation.com/Articles/physics/bending_space.htm
http://www.black-holes.org/relativity6.html

Space the final frontier.

 

[Danoff]

Nobody posted this yet?

 

[Stevisiov]

An antimatter belt around Earth discovered.

http://www.bbc.co.uk/news/science-environment-14405122

Interesting.

Nobody posted this yet?

Very interesting.

 

[PeterJB]

Interesting day today. We will be at opposition with Venus and conjunction with Mercury today. This means that Mercury will now be visible before sunrise for the next couple of months and Venus will now be visible after sunset until June next year when it will transit the Sun.

 

[onearmbandit]

Are you going for the 'new threads in a week' record?

Space isn't general to start with. It's complex place that is full of misnomers and paradoxes which vary depending on who's book you read or your personal take on spirituality, physics and current theorem.

Now, I'm no astrophysics, but luckily for me one of my best pals is. It also happens that my father has a doctorate in metaphysics. I know a great deal about the subject, you can imagine, and know that having a thread about 'Space in general' is either, 1) not going to take off (excuse the pun) or 2) end up with raging battles going on between member who believe different theories.

Yes, universe debate is great, I spend lots of time doing it with the right company and a few beers. I really do feel that this site could do without it to be honest.

Think highly enough of yourself? By the way, I think you meant 'Now, I'm no astrophysicist, unless you really do mean that you are not 'the branch of astronomy that deals with the physics of the universe'.

 

[PeterJB]

Think highly enough of yourself? By the way, I think you meant 'Now, I'm no astrophysicist, unless you really do mean that you are not 'the branch of astronomy that deals with the physics of the universe'.

If he's from China I get the distinct feeling English isn't his first language...

 

[axletramp]

If he's from China I get the distinct feeling English isn't his first language...

Shem isn't Chinese but he does live there.

I do have a bit of a problem with people criticising other people's threads like this though. It's up to the mods if they think a thread is incorrect or inappropriate. I can sympathise that the 'space' subject is vast (every pun intended) and is difficult to generalise - which I think is Shem's point. But if you want a specific thread on any one area of astrophyics, astronomy, etc why not just start one and use this as a 'general' thread for monkeys like me who aren't up to speed on quantum physics?

Just my two-pennies-worth...

 

[Submerged]

If he's from China I get the distinct feeling English isn't his first language...

Technically he is from London, born and bred. He is only in China because he has decided to work there and has decided to settle down there for the time being.

So, his first language is English.

To be fair, the word in question "astrophysicist"(from Mozilla spell checker) or "astrophysicist" (the dude's spelling) isn't the easiest word to spell in English. Or the easiest to remember.

Plus, double checking the spelling on dictionary.com is quite slow on Chinese internet line sometimes (talking from experience here, six months in Shanghai!)

I do agree with axletramp's comments, as I feel that this thread was really for a more general explanations of Space as a whole.

 

[Stevisiov]

If he's from China I get the distinct feeling English isn't his first language...

Try Expat. English is probably shem's primary language, shem raises an interesting point, but it's not necessarily correct.

A general topic about space makes it amorphous and with no specific topic will be prone to a paradigm shift in discussion at the drop of a hat, any number of discussions completely unrelated could potentially happen at once in the same thread, to the point the thread becomes largely incoherent to read. This would almost certainly be the case if it had the volume and frequency of posts we see in threads like the "GT5 general discussion thread".

What perhaps shem didn't consider, is that in the GTP Opinions forum, its unlikely that this thread will ever have to deal with such large volumes posts and as such won't suffer such incoherence issues and as a result, making it a general thread, will likely make it more resilient than specific threads on space. Not that its a necessarily a good thing mind.

 

[axletramp]

^ Agreed.

Anyway, if you could - theoretically - produce a carbon rod 1 light year in length and placed one end on a planet and the other end 1 light year away in space, then one person could shove said rod, would the 'shove' travel faster than the speed of light and therefore transmit basic push-pull messages very quickly?

 

[Stevisiov]

^ Agreed.

Anyway, if you could - theoretically - produce a carbon rod 1 light year in length and placed one end on a planet and the other end 1 light year away in space, then one person could shove said rod, would the 'shove' travel faster than the speed of light and therefore transmit basic push-pull messages very quickly?

I don't fully understand what you are saying, are you saying you could transmit a message by tugging the rod?

If so, the message would not travel faster than the speed of light, as even a carbon nanotube is not entirely rigid.

 

[axletramp]

Ah, so the speed at which a wave of energy can travel through an object which is slower than lightspeed. Fair enough. So how fast would the message get there?

Just asking.

 

[PeterJB]

I think this where Special Relativity comes in. The point of reference of the wave is the rod, not space, so from the waves perspective, it is still traveling at light speed through the rod, not through space.

 

[axletramp]

Hmm, I think I get that.

👍

 

[BobK]

^ Agreed.

Anyway, if you could - theoretically - produce a carbon rod 1 light year in length and placed one end on a planet and the other end 1 light year away in space, then one person could shove said rod, would the 'shove' travel faster than the speed of light and therefore transmit basic push-pull messages very quickly?

The 'shove' would travel much slower than the speed of light because it would travel at the speed of sound which is slower by around 4 orders of magnitude. So figure on the shove taking 10,000 years to get to the other end.

 

[axletramp]

So figure on the shove taking 10,000 years to get to the other end.

Bang goes my idea for super-fast interspace communications via sticks!

*screws up paper and throws in bin*

 

[Famine]

Not quite the case.

Electricity propagates through cables at approximately the speed of light. The electrons within the cable move at about 8 centimetres per hour*. It's essentially based on the same principle as above - get a metre long rigid PVC tube and stuff it full of marbles, push one marble in one end and another will fall out of the other end almost immediately. Though the actual marbles move by a handful of millimetres, the marbleforce propagates at the order of hundreds of metres per second.

For the "nudge a long object" notion above, you'd need to invoke special relativity*. If you and I were holding a five metre pole at each end and I gave it a push, you would receive the pole** almost immediately. The actual "speed of pole" would be however far I pushed it in however long it took for the push to occur. If it were fifty metres long - and appropriately rigid so it didn't bend in the middle - you'd still receive it almost immediately and the actual "speed of pole" would be the same as before. If it were five hundred metres long - same caveats - the same would occur. Five thousand metres, five million metres, 6 trillion miles... it's all the same.

This is where special relativity comes in. The classical upper bound of speed for the universe is c - the speed of light in a vacuum. It's not possible for anything - even (especially) information - to travel faster. Except that it is, depending on your frame of reference. Special relativity provides for this (errr... sorta) by deconstructing the paradox into inertial frames of reference.

Imagine you have a spacecraft that can fly at most-of the speed of light (from the inertial frame of the universe) - call it 0.9999c - and you fly to a point a light year away. From the frame of reference of an Earth-bound observer you would have taken 1/the speed of the craft years to do it (1/0.9999 = 1 year, eightish hours). Due to relativistic time dilation, your on-board clocks will say it took you less than a year and from your frame of reference you would have taken the time your clocks say/1 years to do it (the Lorentz Factor, by which time "slows", at would be about 25 million, so your clocks would say it took you 1.2 seconds). Your speed - or "proper speed" - would be 1 year/the time you took, so it'd be just about 25 million times the speed of light.

But your "proper speed" is only how fast you're going in your frame of reference. There is, in fact, no upper bound on proper speed.

So what you'd end up with is a whole series of things that look like they're moving at speeds above the speed of light in a vacuum from one reference point, but from the reference point of the universe nothing actually exceeds this speed. Except maybe the phase velocity, but that's normal (the phase velocity of X-Rays in glass can exceed c) and transfers no information.


I appreciate that much of the above looks like complete bollocks. That's special relativity for you.

*Yes I've footnoted two things with the same notation. The electrons move at relativistic speeds relative to their atoms, but at 8cm/hour (give or take) relative to one another and to the flow of charge.
**Fnarr!

 

[axletramp]

Wow, have a drink on me! That's great, and I (kinda) understand it. So the message would, in theory, be faster than the previously quoted 10,000 years?

*gets ready to retrieve and uncrumple paper*

I can't help feeling I've dragged you away from something far more important than to write that answer to my question.

 

[Famine]

Even if you were to take into account the time taken to receive and understand the message, you're looking at getting it there in an appreciable amount of the speed of light.

But then rather than lashing two planets together with an infinitely rigid pipe of ridiculous proportions and communicating by Morse Code you could just, say, send a EM signal at the speed of light...

 

[axletramp]

Damn the competition!

 

[Stevisiov]

Ah, so the speed at which a wave of energy can travel through an object which is slower than lightspeed. Fair enough. So how fast would the message get there?

Just asking.

Well, to understand why its not the speed of light, it is as you say a wave propagating through the material, you need to understand that even the carbon rod (about as rigid substance known to man) is not completely rigid, and if you look at what is going on at nano scale, you will understand that when you nudge a rod, you nudge the carbon atoms nearest to you, these in turn nudge then carbon atoms next to them, which in turn nudge the carbon atoms next to them. This is an impluse travelling through the material moving from carbon to carbon. It's therefore understandable that its not the fastest process in the world.

BobK is correct when he says that this is the speed of sound, although the speed of sound in rigid solid is much faster than a gaseous substance such as air (the airplane mach speed we are familiar with). Generally the more rigid the substance is the faster the speed of sound in that substance, it should come as little surprise to you then that the speed of sound in a carbon nanotube is much faster than most other materials. It's hard to find any concrete data on the speed of sound in a carbon nanotube, but I have found a theroetical estimation of 22 000 m/s, which is mighty fast, but its incredibly slow when compared to light speed.

So if you made a carbon nanotube an incredible 1 light year in length, and you sent a physical impulse down it; it would take....

...Drum Roll....

14 413 years! compared to the 1 year it took light to send the equivalent information.

Or to look at it another way, the speed of sound of a carbon nanotube is 0.007% the speed of light.

----

On a side note, to send a message the equivalent distance of mars at its closest point to the earth (54.6million km):

29 days.

Of course the practical problems of such are massive.

 

[axletramp]

14 413 years! compared to the 1 year it took light to send the equivalent information.

Or to look at it another way, the speed of sound of a carbon nanotube is 0.007% the speed of light.

...Of course the practical problems of such are massive.

The final nail. I guess I'll just have to go Dragon's Den with another idea then...

...I know, my portable light spheres! But that's more a question of physics rather than 'general space'.

 

[Vince_Fiero]

I appreciate that much of the above looks like complete bollocks. That's special relativity for you.

The relative speed is OK for me, although I admit that thinking in an accelerating frame of reference still has many challenges.

However, even if we feel the bar movement as almost immediate, there must be an interaction on micro-particles (lets stop at atoms) level. Where on a small rod you do not feel this, it must be different on distances of a light year. For me it is these minuscule movements of atoms in the rod that will make it slower then the speed of light.

In the end, I guess that getting a feeling what the limits of communicating over distances of a lightyear are that makes it relevant to "Space in General".

The fastest way might be to create a wormhole with ends between the 2 points you want to communicate. But playing with gravitational singularities is not recommended in our current stage of science development.

On the other hand we are playing with some of them already:

 

[Vince_Fiero]

sorry Stevisiov, was writing this at the same time it seems
sorry all the others, pushed wrong button (quote, not edit, it seems).

 

[Famine]

BobK is correct when he says that this is the speed of sound

I disagree.

To transmit sound from one atom to the next requires that all of the oscillations associated with that sound are transmitted - back and forth at the appropriate frequency/frequencies (in special relativity it's held that a monochromatic wave - one of a single frequency - can exceed c in certain circumstances but transmits no information and cannot be held to break the upper bound of c for information, so we'll take "sound" to be multifrequency). To transmit a single impulse "push" doesn't.

A twang on a string would be transmitted at the speed of sound. The force from me pushing a six foot staff into someone's face would not.

 

[Griffith500]

I disagree.

To transmit sound from one atom to the next requires that all of the oscillations associated with that sound are transmitted - back and forth at the appropriate frequency/frequencies (in special relativity it's held that a monochromatic wave - one of a single frequency - can exceed c in certain circumstances but transmits no information and cannot be held to break the upper bound of c for information, so we'll take "sound" to be multifrequency). To transmit a single impulse "push" doesn't.

A twang on a string would be transmitted at the speed of sound. The force from me pushing a six foot staff into someone's face would not.

So what if you bashed one end of the rod with a hammer, and listened on the other end? What about shock-waves? It's all interesting, but I think the power required to send such a "signal" down said rod would probably destroy the matter at the transmitting end anyway.

Interestingly, the impulse function is defined as containing all the frequencies (hence, impulse response). I think a push is more like a step-change / DC offset, so zero-frequency (except the transition does contain other frequencies... argh!) since the rod doesn't come back - it is accelerated, "moved", and decelerated then stays put.

I remember having this discussion a few years ago, and one guy, an electrical engineering post-Doc, seemed to think that if you were to move the rod at one end, the other end wouldn't move at all. I didn't really understand his explanation at the time, but it was something to do with the other end being inobservable from the pusher's perspective. Or something. I don't really get this relativity lark. Practically, I can see this arising from the interaction of elasticity and inertia, though.

I guess it's the assumption that the matter can be moved collectively, as opposed to as a result of the interactions within that matter. It's those interactions that propagate, even when you're just moving stuff about.

EDIT: The speed of sound in solids is generally of the order of kilometres per second, so you can see the difficulty in testing this...