Slinkey

Indeed. Now apply that to the EH. As you move towards the EH it is contracted in the direction of your movement and as your velocity increases the BH becomes more and more pancake shaped. If you could reach light speed it would become an infinitely thin pancake. Falling towards a BH isn't just like falling towards a planet although even when you fall towards a planet, like Earth, it also is contracted in the direction of your movement, but because you are travelling at a tiny fraction of c this effect is negligible.

My son has asked me if any of you know of any decent childrens science sites? he is 10 years old and pretty new to things scientific, so it would be much appreciated if anyone can point me to a site for this level of understanding. thanks in advance

Where are these inquisitive minds? All I can see here is obvious trolling.

Yep. You're a troll. End of convo.

Please provide some evidence of this assertion.

The guy is either unable to learn or a troll. For his sake I hope it is the latter. Don't put words in my mouth. This is classic trolling behaviour. I agreed to no such thing and if you had actually bothered reading and thinking about what people are writing to you, you might actually see the irrelevance of your statements. It is quite clear your level of understanding. This rant shows precisely why.... These all class as observations. In science this is the same as saying measurement your lack of precision notwithstanding. I have no idea if objects exist before they are observed/measured, and I don't need to make up my mind either as this is completely irrelevant. And you intend to prove this how? No, I didn't say it had no basis in science. I said depending on your interpretation of QM this question is unresolved to a satisfactory degree. For the purposes of length contraction it is however completely irrelevant. It has nothing to do with length contraction. If SR is correct then from the perspective of light there is no passage of time (this is however an assumption as no one knows). Thus light leaving a source takes no time to reach an object and the reflected light takes no time to reach your eye andt herefore the object does not have to exist before the light hits it - from the perspective of a photon that is. So, no. I could argue that the object does not need to exist before the light hits our eye. It depends on your reference frame. Check out QM and the Copenhagen Interpretation. You might have a seizure. And, no, that is not wishful thinking you lot! What I personally think with regard to this existential question has no bearing on length contraction. URRR-urrrr. Sorry, but no it doesn't. The "ground floor" of length contraction is the constant speed of light in vacuo regardless of reference frame. As you are being told: the existence of an object and whether it was there before we observed/measured it is irrelevant to length contraction. If something is in its "natural undistubred state" then it is not being observed or measured and we can say nothing about it. As far as we on earth are concerned if we don't know about it then we don't know about it. How about on your planet? Have you considered bricklaying? It wont get you in MENSA.

I guess he meant sub-luminal but near light speed. I would say even that is infeasible because the background radiation will be harmful to you at appreciable fractions of c. Also, it's worth pointing out that with a constant acceleration you would not reach c. Hence Tom's quote.

You seem to be falling over right at the start. The bench, before anyone observes it, has undefined dimensions. Until we measure something we can say nothing about it. Depending on your frame of reference different observers may report different measurements. That is more of a philosophical stance than a scientific stance. Whether an objects exists before we view it is irrelevant. When we measure the object observers in different frames of reference will report different measurements. No. I'm saying that depending on your frame of reference your measurements will disagree with people in different frames of reference measuring the same object. Most of the rest is you just saying the same thing over and over again. Sorry you're having such a hard time understanding this. Maybe you should become a carpenter instead.

Which infinity? There are more than one.

Yes. Depending on your frame of reference there can be disagreement about how much space it occupies. It is different for anyone in non-mutual reference frames. I notice you didn't answer the questions I gave you with the bench example. One person measures it as 8m and the other as 6m. So how long is the bench, Eric? If an object changes shape then we try to discern why it changes shape. We don't exclaim "it didn't really change shape though". You're welcome. In my hand I have an object. How long is it, Eric? You don't know? Then how can we know if anything has any dimensions unless we look at it in some way? Your question "Does the bench have a length when no one is looking?" is an insensible question as it assumes we can know something before we know it. We only know the length of the bench from measuring it and, has been relayed to you countless times, the length depends on your frame of reference. As Swanson told you: the "best" you can do is find its proper length. ie. the length you measure it to be when you are in the same reference frame as the bench. In the example I gave the proper length of the bench is 10m, but for the two moving observers the length is not 10m and is dependent on their motion relative to the bench.

Zephir, It's not a claim. If you had bothered to actually read this thread you would already know that. Indeed. It doesn't make them wrong. This is precisely what we are trying to get across to Eric 5 - the length is dependent on the frame of reference.

Cough

Eric 5, consider this question please: Two trains are travelling towards a station from opposite directions. Train A is moving at 0.8c. (these are exceptionally fast trains). Train B is moving at 0.6c. On the platform is a bench. As train A passes the bench it measures the bench to be 6m. long. As train B passes the bench it measures the bench to be 8m long. How long is the bench?

As Timothy Leary said "I love the words 'I don't know' as I know I am about to learn something". I did think about that but didn't consider it a force in the same sense as Eric 5 meant it. ie. there is no force outside the ball compressing or decompressing it, but as you say, it can do work so therefore there must be a force to do that work. Bah! The easiest way to understand the logic behind length contraction is with muon decay as it is well documented. http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html What you have to sort out in your mind first and foremost is the idea of reference frame as you seem to be having difficulty grasping it.

Apart from the elastic qualities of the rubber ball (doesn't have to be strong elastic just needs to be strong enough to make a ball shape), air pressure (ignorable for a vacuum scenario) and gravity (ignorable in a flat spacetime) I can't think what force you are pointing at. Even if you're suggesting the phase transition it's not a force being acted on from outside the ball. All we are doing is cooling and heating the ball. By doing so we are not trying to compress or decompress the ball, but it does indeed change size. But I'm sure you're going to make me look stupid now for some glaring oversight so go ahead. I love moments like this because I usually learn something quite important.

Hi Tom, For sure these are not frame dependent. The point I was trying to get across was that matter doesn't need a force applied to it to "change shape" and thus his claim that it does is actually incorrect.

Cool animation. I could really picture that in my mind as if I was on that little blue spaceship. OK, now my question. The two electrons are a distance, d, apart at rest in my reference frame. A virtual photon will take time, t, to travel the distance between them. When the electrons are moving at 0.8c relative to me, the distance, d', the virtual photon has to travel is far greater in my reference frame and, as you say above, the virtual photon's wavelength, and thus its energy, is dilated. If I had two electrons at rest in my reference frame at distance d' apart would QM allow a virtual photon exchange between them, and if so, would the virtual photon have the same energy as the virtual photon moving between the two moving electrons above?

The animation shows the rest frame for each observers point of view. In your own rest frame a meter is a meter is a meter. However, when either person looks at the other person they find that the meter is shorter. ie. length contraction is observable from either rest frame as no one has an absolute definition of length. I was being sarcastic actually. I was pointing out that the page you claim supports your POV does nothing of the sort. Unfortunately, and please don't take this as an insult, you simply do not understand what the page is telling you. There is no absolute time. There is no absolute length. There is no absolute energy. All are frame dependent. And, unfortunately, it is wrong. Actually, I'm beginning to think that you were educated far beyond your intelligence, or you are some kind of elaborate troll. I have read lots of books on relativity and not in any of those books does it ever say that length contraction happens in the math but does not happen in reality. It seems the whole world disagrees with you my friend, and although that is a logical fallacy argument, I believe in this instance it might be worth you pondering for one moment why this is the case. sigh..... Hmm, if I have a rubber ball filled with water and remove heat energy from it it seems to expand once the water turns to ice. No "decompressive" force needed. Just a refridgerator. If I take the ball out of the fridge and leave it in the corner of a warm room (for example room temperature) it will shrink. No compressive force needed. Just had to take it out of the fridge and allow it to gain heat energy from the warm room and turn back into water. So, your "has to be a force applied" is clearly not an absolute. Funnily enough, neither is time, length or energy. I am, and some of the more advanced stuff too, although I am far from being an expert. However, my betters here are also telling you the same thing, and I don't see any evidence of your credentials within this thread. Personally, I don't care whether you accept it or not. However, whilst you make the claim on here I, and no doubt, others will endeavour to point out your failure to grasp this subject. Because the evidence is overwhelming - muons - Michelson-Morley - Einstein - Feynman - Thorne - any notable scientist. It makes perfect sense. These people weren't saying it just to piss you off. Relativity shows us how matter changes shape dependent on reference frame. We are debating the mathematical proof of length contraction right here. Maybe you could post up a mathematical proof, or even a thought experiment, that would show us why we observe length contraction but it doesn't really happen? Thus far all I have seen you do is say "isn't".

I have a question/thought experiment: According to relativity the speed of light is constant in all frames of reference. This got me to thinking about virtual photon exchanges between electrons. If I was watching the exchange of a virtual photon between two electrons would the virtual photon move at the same velocity if the exchange was taking place on a spaceship passing me at say 0.8c? Also, if the exchange of the virtual photon was alligned with the direction the spaceship is travelling would the virtual photon's energy appear to be reduced as from my frame of reference the distance the virtual photon has to travel is greatly increased?

Would I be right in thinking that a better way of seeing relativistic mass is that when we accelerate a massive body we are increasing its inertia? ie. the faster we "push" it the more inertia it has?

So, what you're saying is that time dilation is an illusion also? Weird. I went to the website you posted and found an animation explaining to me how length contraction works. Maybe you posted the wrong web address? The math tells me that length contraction happens and the demo displayed length contraction happening. Again, perhaps you posted the wrong web site as nothing on the one you posted supports your viewpoint. The material's length is changed due to the constant speed of light for all observers. As I have already told you, the laws of mechanics have no choice but to change in a universe where the speed of light is constant for all observers. You are welcome to show us the math that allows for this singular premise without length contraction. The premise being that the speed of light is constant for all observers. I look forward to seeing your math. Are you talking to yourself here? Nice quote. Completely irrelevant to the thread but a nice quote. ie. you don't understand the math, nor can you accept the inescapable consequences of light being a constant for all observers. It seems in your world that when I am motionless with respect to a light source that I measure the speed of light as 300.000km/sec. Yet when I move towards it at, for eg., 100,000km/sec, I will now measure the speed of the light coming from the light source as 400,000km/sec. Unfortunately, there is no evidence this is correct. What we actually find is the speed of light is always 300,000km/sec regardless of our motion with respect to the light source. The inescapable consequences of this fact are that time dilation occurs, mass/energy dilation occurs, length dilation occurs. And guess, what? There are reams of evidence tyo support this and nothing to support you. Whom shall I believe, Bertrand? All the evidence, or some frothing poster on SFN?

"They said I was mad. I said I was not. Unfortunately I was outnumbered" http://www.phys.unsw.edu.au/einsteinlight/jw/module4_time_dilation.htm#length Every link you post confirms the existence of length contraction. In this one it says we "observe" them to have different lengths. Is that appears or actually?

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html#c3

http://theory.uwinnipeg.ca/mod_tech/node136.html

Thanks. Nice to know I'm not the only loony here. Indeed, and a stroke of genius on Einstein's part to realise it. A triumph for theoretical physics. The implication of GR is that it would seem that there is no passage of time at the singularity. However, as GR is an incomplete description of a black hole I think that GR could actually be misleading us at the singularity. My speculations about black holes are detailed in another thread on this forum - The Paradoxical Nature of Black Holes.