41

Physics, Astronomy & Cosmology / Re: Can Stars form without Planets?

« on: 28/04/2012 22:36:11 »

A fairly large proportion of stars are "double stars" -- two suns orbiting each other. With double stars, there is no necessity for planets to form during the accretion stages of formation, and even if they do there are no stable planetary orbits. So "double star" systems have no planets.

I do not see how a star could form from a cloud of dust and gas into a single body, but I am not an expert, or even well read up in this area. I think that if a star does not have a companion star, then it must have had a planetary system at some stage of its evolution. Conservation of angular momentum pretty much guarantees it.

A good example would be Zeta Reticuli - a binary star system which in cosmological terms, is very close. I forget how close now, maybe 38 light years away? I might be way off with that. Anyway, some exobiologists believe there might be life there, including planets. We haven't detected any planets yet, but we may in the future.

42

Physics, Astronomy & Cosmology / Re: What is the temperature inside a Black Hole?

« on: 28/04/2012 22:26:41 »

Numerous event horizons at different gravitational potential? 

Differences in gravitational potential would normally imply different time dilation factors but at the event horizon time is already infinitely dilated (time stands still). 

Time can't go any slower inside the EH.  Maybe time reverses direction.  That would account for why something that is very hot from one reference point is actually very cold from another.  Maybe from a time reversed reference frame within the EH, black body radiation of the black hole is seen from the outside as black-body absorbtion. 

Obviously, this is pure speculation as we have little idea of the physics of black holes.

added
The above would seem to be in keeping with my reply #6 in this thread.
"So is absolute hot, the same as absolute cold?"

Take what I said above as true... but there was something else I realized just there.

Time-reversed scenario's of black holes also go by another name, called white holes, but these objects spit out energy  instead of sucking it in. They may not exist however because it is generally believed they violate the second law of thermodynamics.

43

Just Chat! / Re: Something wrong with my thread?

« on: 28/04/2012 20:40:32 »

Ahhhh is that were my problem lay yesterday


hahahahaha

I am an idiot.

44

New Theories / Re: Is there Gravitational Red Shifting?

« on: 28/04/2012 19:15:43 »

This article suggests that the speed of gravity may in fact be much greater than the speed of light.

http://metaresearch.org/cosmology/speed_of_gravity.asp

Yes superluminal theories of gravitation have been around for a while. If spacetime is only a disortion - a curvature without any physical mediator then it may be conceivable that gravity could be a superluminal phenomenon. Personally, I don't think it will, but it is a tantalizing thought since curvature stores energy in the vacuum.

45

Physics, Astronomy & Cosmology / Re: Times less than Planck Time?

« on: 28/04/2012 19:09:26 »

That was so weird... a good while ago I couldn't even post here lol

46

Just Chat! / Something wrong with my thread?

« on: 28/04/2012 10:08:15 »

Every time I go into this thread: http://www.thenakedscientists.com/forum/index.php?topic=43930.0 my name, messages and the dates all disappear at the top right of the page, also, the options to reply, edit anything has all disappeared for me... is this the same for anyone else, or just me?

?? confused.com

47

Physics, Astronomy & Cosmology / Re: What is the temperature inside a Black Hole?

« on: 28/04/2012 09:24:53 »

I can tell you why. The interior boundaries are created from space and time switching coordinates. I could show you math which explains how space and time switch roles... it doesn't really mean that space is really time and time is really space now, it's just a coordinate phenomena.

The gravitational effects of a black hole become so strong at the horizon, that space and time switch roles: space becomes timelike and time becomes spacelike. Then somewhere inside the black holes, these artefacts change back to normal and it will be here you find the inner boundary. With that said, Sean Carrol is dedicting a lot of his time to weild the idea that we are living inside a black hole, and I can only presume it would be inside the interior where space and time are acting normally again.

Is it possible that space and time switching coordinates is the same as the arrow of time reversing?

It would account for "space and time acting normally again".

You do realize that I don't believe an arrow of time exists? I won't go into the reasons why, but I should state that time is not linear - and for this reason, the whole idea of the coordinate change might be a load of rubbish.

In some loose way of speaking about this coordinate transformation, Space becomes Timelike, but what does that mean?

Well, in the view of mathematics, time goes one way: it looks like an arrow to us, because everything has a forward directionality, we never see things going back in time. Because of this, we humans often project this phenomenon subjectively and believe that time has some ''linearity'' about it. Well, when we say that space has become timelike, we mean that we are now [moving in space] as if we were linearly moving through time. This means we cannot move to the sides, we cannot move backwards.

We can however begin to move through time very freely. We may in fact, oscillate in time. This would mean there is no preferred directionality and this is what we mean when time becomes spacelike.

So as for time being viewed linear, that is dubious and the greater collection of physicists today don't believe that time flows linearly like a river. However, even with that said, even in the view of time being spacelike, linearity is not preserved, you may oscillate in the time dimenion.

48

Physics, Astronomy & Cosmology / Re: Times less than Planck Time?

« on: 28/04/2012 06:44:32 »

Oh yes, I agree, physics is the best game there is and you're a gamer Wulf.

And I shouldn't be so harsh on Brian, he's a cool guy, although temperamental at times as seen at some blogs
He's doing some pretty impressive speculating, as we all want to do at times

==

As for above and under Planck, it's like you said, most of the physics we use today draw a line there for what we can explain. Maybe we will get a way to prove scales under it too, Smolin had some ideas there, or rather some of his friends? Using astronomical evidence for drawing conclusions of what might be under Planck scale.

In regards to Smolin, did he? (or his friends)? I haven't seen any of that work, do you know where a link is at?

49

Physics, Astronomy & Cosmology / Re: Times less than Planck Time?

« on: 28/04/2012 06:35:56 »

I dare say sub-Planck physics might be the right track though.

If spacetime arose from a singularity, a point - in no dimensions, then perhaps this makes sense why spacetime would make no sense below the Planck lengths. Below these lengths, we must assume that space and time are not fundamental. And below this length, the uncertainty principle concerning energy  is very high. Hopefully all these things will lead to some clues in which we can treat the initial conditions with a new type of understanding, or maybe try and understand it with the physics we have - as it may just be a matter of peicing a very complicated jigsaw puzzle together.

50

Physics, Astronomy & Cosmology / Re: Times less than Planck Time?

« on: 28/04/2012 06:29:27 »

Well Wulf, Brian has a very fertile mind And.. He.. Will.. speculate..
and as he does, sell books..
==

But yes, he's interesting, and some of his attempts to explain, especially entanglements, was very good. Still I prefer the experiments first. Theory building on that, and I'm not discussing weak measurements when I say experiments.

I do try and speculate myself. I am already trying to write out some kind of unification in my head as well, so I can see why physicists enjoy the speculations so long as there is a real science behind it

Unlike Hawking... who recently advocated M-theory as the theory of everything... I was very disappointed at this.

51

Physics, Astronomy & Cosmology / Re: Times less than Planck Time?

« on: 28/04/2012 06:12:08 »

Interestingly, Brian Greene has speculated on sub-Planckian existences. Whilst the Planck lengths could be fundamental, we don't know this for fact. He said:

"the familiar notion of space and time do not extend into the sub-Planckian realm, which suggests that space and time as we currently understand them may be mere approximations to more fundamental concepts that still await our discovery.”

Which is interesting, because if anyone actually follows my own speculations and contentions, I have been wheeling the idea that space and time could certainly not be fundamental since in the very beginning, there was no geometry (space-time) - not in the sense that GR deals with it.

52

Just Chat! / A question for the site

« on: 28/04/2012 03:41:14 »

Why doesn't the Naked Scientist Forum have a mathematics subforum?

I think it would add some flavour to place...

53

New Theories / Re: Is absolute hot the same as absolute cold?

« on: 28/04/2012 00:06:20 »

Cold takes energy and time.Hot gives energy and time.

Ęthelwulf

I think what simplified meant was cold represents a lack of usable energy and hence time dilates.  Hot represents energy and time contraction.

No. One is very warm relatively associated with one which is very very cold.

I am perplexed by your logic.


... look. Theories should tackle either problems known, or problems yet to be solved. Not by speculations and certainly not by models which permit the old saying ''if it is not broke, why fix it?''

This thread arose in response to a another thread.  What is the temperature inside a black hole.  Some proposed it is near absolute hot, I proposed it is near absolute cold.  This thread attempts to explain how two seemingly opposites can be the same thing.

Yes, it is speculation in as much as it is not proven but time reversal does come within the laws of physics as we understand them.

The physics of black-holes is fundamental to our understanding of the Universe and there is much we do not know.  Debate is a means of reaching that goal.

I understand your frustration, because if time reversal were to be a proven fact then your ideas of the non-existence of time would be thrown out of the window.

Time reversal might have significance for individual particles, but as far as the entire universe goes, the universe is asymmetric. If it was symmetric, we might expect things like a time reversal in physics... but as far as I understand physics, time reversal is a much abused concept. Such a symmetry is a simple mapping



But the observable universe does not contain such a transformation, the universe is largely asymmetric due to the second law of thermodynamics.

54

Physics, Astronomy & Cosmology / Re: Are frames of reference even more misunderstood than centripetal force?

« on: 27/04/2012 19:33:15 »

I think we all agree on the physics, but we disagree on what terms should be used to describe different parts of the physics.  The problem with writing this agreement off as semantics is that you're indicating that semantics isn't important in physics.  But the precision of the definitions we give to terms is absolutely critical to science!

I'm not saying semantics is really not that important, only that it has muddled this conversation to tenebrous levels

55

Physics, Astronomy & Cosmology / Re: Force of impact question

« on: 27/04/2012 19:32:02 »

I drop a 1kg weight from a meter in height and it decelerates to a stop in 0.1 of a meter (total distance travelled 1.1 meters)
What force is applied to the impact object?
What force is applied to the falling object? (assuming no deformation)
All assuming no air resistance and no bouncing

Why is your question expressing weight in kilograms, that is the unit for mass. Weight is expressed traditionally in Newtons?

http://en.wiktionary.org/wiki/weight

You should check out def no.s 2,3 &5.  Weight in the OP is being used as a concrete noun - ie a lump of metal of known mass.

Oh right. Ok.

So really

1kilogram of mass  as we know is 9.81 newtons thus I suppose, 1kg = 9.81 newtons and since 1 newton is 0.101971621 kilogram of force then 1 kilogram of force is 9.80665 newton.

56

Physics, Astronomy & Cosmology / Re: Force of impact question

« on: 27/04/2012 19:26:01 »

I drop a 1kg weight from a meter in height and it decelerates to a stop in 0.1 of a meter (total distance travelled 1.1 meters)
What force is applied to the impact object?
What force is applied to the falling object? (assuming no deformation)
All assuming no air resistance and no bouncing

Why is your question expressing weight in kilograms, that is the unit for mass. Weight is expressed traditionally in Newtons?

http://en.wiktionary.org/wiki/weight

You should check out def no.s 2,3 &5.  Weight in the OP is being used as a concrete noun - ie a lump of metal of known mass.

Oh right. Ok.

57

Physics, Astronomy & Cosmology / Re: Force of impact question

« on: 27/04/2012 18:50:33 »

I drop a 1kg weight from a meter in height and it decelerates to a stop in 0.1 of a meter (total distance travelled 1.1 meters)
What force is applied to the impact object?
What force is applied to the falling object? (assuming no deformation)
All assuming no air resistance and no bouncing

Why is your question expressing weight in kilograms, that is the unit for mass. Weight is expressed traditionally in Newtons?

58

Physics, Astronomy & Cosmology / Re: Times less than Planck Time?

« on: 27/04/2012 18:47:24 »

The Planck Scale

The Planck scale is where one can no longer rely on GR and Quantum Gravity is needed.  Additionally QFTs breakdown because one is no longer able to renormalise out the effects of gravity.  It is beyond the planck scale that we need unified theories - the four forces are no longer separate but are all aspects of a single force (possibly)

The planck scale, the p. time, the p. lenght, and the p. mass do not form a fundamental limit beyond which nature does not pass (as an analogy absolute zero is a fundamental limit); the planck scale is a limit of our current understanding, but we are almost certain that it can be exceeded physically - look at the Planck Epoch aka Planck Era.   

Experimentally - we are not even close to the Planck Scale - and we don't have any good ideas of how to get there yet; but that is a technical limit not a fundamental one

Imatfal, could you please return this thread back to the question and answers forum. This is completely in the wrong place. It is not a new theory thread.

59

Physics, Astronomy & Cosmology / Re: Force of impact question

« on: 27/04/2012 18:33:28 »

Well, what equations have you learned for the question? I assume this is homework. I'll steer you in the right direction:



The force is and weight is also a force .

60

Physics, Astronomy & Cosmology / Re: Times less than Planck Time?

« on: 27/04/2012 18:01:55 »

Here is a derivation I quickly looked over and which might help.

http://www.colorado.edu/philosophy/vstenger/Cosmo/PlanckScale.pdf

There are a few jumps in these derivations you need to be careful of just looking over it again, it may not seem clear. For instance, when it asks us to take as the radius of a sphere... thus



Then it asks to consider a special case



a bit of jump without a derivation. I work it out as, multiply both sides of
 with the speed of light squared,



The c in the denominator on the right cancels, a appears besides the reduced planck constant . Then one must know that so



And that looks close to the equation for