A few questions about astronomy/astrophysics.
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First of all, thrust(not quite the word I need; chemical reaction is better) equals energy, which equals light. Therefore it is impossible to have more thrust than pure energy itself; therefore speed of light is impossible to exceed.
mxdplay4 wrote:
It's confusing when you try to visualise quantum physics in terms of Newtonian mechanics. Assumptions which everyone makes regarding relative speed etc just simply do not apply.
Did you know that it has already been proved that objects travelling at very high speeds 'go slower'. (This was done using atomic clocks).
The problem is that we talk of distance and speed which is equivalant to talking about space and time. But space and time are inextricably linked. We should talk in terms of the space-time continuum.
Just to throw us into further confusion, the 'impossible' has apparently been achieved by accelerating a (very small) particle to faster than the speed of light (!!!!) (for an incredibly short time).
Trying to get your head round this is like trying to explain to an ant in London what the Sydney harbour bridge is like. What is infinity....? Where did all this matter come from...? Does the Universe expand,contract or just hang at the end of time...? What is the end of time if time is infinite...?
What we do know now is at the very edge of human knowledge and therefore very difficult to comprehend.
Stuff like sunlight exerting pressure because it has mass is actually pretty standard easy physics. If you cant get that, you have got no chance with quantum physics.
Why can't you macho people explain things in an easy way?
1. Quantum Mechanics is hard to relate to ordinary things.
2. Special Relativity predicts clocks go slower the faster their speed, and we have proved it.
3. The impossible has not been achieved with a particle .
4. Some questions are meaningless. "What is the end of time?" Dear me.
5. Actually the edge of human knowledge is very easy to comprehend if you have a good teacher. I do both.
6. Sunlight does not have mass but it exerts radiation pressure because it has momentum (p=E/c)
7. Therefore you have no chance with quantum physics, QED
mxdplay4 wrote: Loomis wrote:
mxdplay4: "Stuff like sunlight exerting pressure because it has mass is actually pretty standard easy physics."
Even massless particles like photons can carry momentum.
Photons have relativistic mass due to their velocity, but no inherent mass like we are used to in everyday situations (resting mass). I'm not disagreeing with Loomis since his statement is correct in the major sense. But it just shows that this is a very difficult area to get your head around.
Photons do not have relativistic mass. They have zero mass period. They exert momentum effects because of their velocity. They ACT like they have mass, but do not have mass. "inherent mass" is not a term used by any scientist.
Soulcrates wrote:
1.) Why doesn't light follow the absolute reference frame rules that apply to other objects (like if you headed opposite a light beam it's apparent speed wouln't be the speed of light + your speed)?
I've often pondered a similar question, but there are so many sources of light, it would be impossible to only have 1 frame of reference in space. My question was if you are moving away from an object nearing the speed of light, does that object appear to slow down in its movement, and when you reach the exact speed of light, would that object cease to be visible, then as you exceeded the speed of light, would it then be moving in the opposite direction, since you're now catching up to light particles from prior to its current position.
2.) According to String Theory, everything is made up of strings... so If energy has no mass than how come the universe and the stuff on it does?
It's a theory, as much as I can understand from it, I assume that the mass is so minute that they assume it is 0, like sunlight.
3.) Would a black hole be very hot or very cold?
I would assume very hot.
4.) How do you come up with 12 dimensions in string theory ( be gentle so a teenager can grasp it)?
I've never heard of 12 dimensions, but here's a cool video that explains 10.
http://video.google.com/videoplay?docid=-97057222894136590
5.) Why would mini-black holes created in particle accelerators instantly disintigrate?
Since black holes ingest everything around them, I would assume they had no more food.
The velocity of light is constant no matter how fast you are moving. Counter-intuitive but there you go. It is actually a product of studies made by Maxwell into electricity (see my blog post).
It is a consequence of light needing no medium to be transmitted through.
Daemon_Panda wrote: First of all, thrust(not quite the word I need; chemical reaction is better) equals energy, which equals light. Therefore it is impossible to have more thrust than pure energy itself; therefore speed of light is impossible to exceed.
Whoops! You are confusing Chemistry with nuclear physics. Speed of light has nothing to do with Chemistry. Sorry.
Daemon_Panda wrote: First of all, thrust(not quite the word I need; chemical reaction is better) equals energy, which equals light. Therefore it is impossible to have more thrust than pure energy itself; therefore speed of light is impossible to exceed.
You're misunderstanding of the topic astounds me.
Kazue_Fukiishi wrote:
"inherent mass" is not a term used by any scientist.
You can use the term 'invariant mass' then. To be correct for the people who already understand it.
Kazue_Fukiishi wrote: mxdplay4 wrote: Loomis wrote:
mxdplay4: "Stuff like sunlight exerting pressure because it has mass is actually pretty standard easy physics."
Even massless particles like photons can carry momentum.
Photons have relativistic mass due to their velocity, but no inherent mass like we are used to in everyday situations (resting mass). I'm not disagreeing with Loomis since his statement is correct in the major sense. But it just shows that this is a very difficult area to get your head around.
Photons do not have relativistic mass. They have zero mass period. They exert momentum effects because of their velocity. They ACT like they have mass, but do not have mass. "inherent mass" is not a term used by any scientist.
The key term here is relativistic mass. Photons have no rest mass (invariant mass, intrinsic mass, and proper mass are all terms for this), but they do have mass because they carry energy. By mass-energy equivalence they also have mass.
Relativistic mass (or apparent mass) is the sum of a particle's rest mass and the mass from kinetic energy. An observer who sees an object moving near the speed of light would measure the mass of that object to be larger than its rest mass (which is the mass measured when the object is stationary w.r.t. the measuring reference frame). This "extra" mass is actually the kinetic energy that the object possesses due to its motion.
I was talking about energy; I'm sorry I am not in college yet. I have my own theories about this sort of thing; me and a friend of mine.
What you said still isn't correct. The exhaust velocity of any rocket (conventional or otherwise) is not what limits the speed of the craft. The limiting factor is that it literally takes an infinite amount of energy to accelerate a craft up to the speed of light.
" First of all, thrust(not quite the word I need; chemical reaction is better) equals energy,"
It most definitely does not. Thrust is a force which is the time derivative of momentum. Energy isn't. The two quantities aren't equal. They even have different units: Newtons for thrust (or kg*m/s²) and Joules for energy (kg*m²/s²). Similar, but different.
Perhaps you should explain more of your "theory".
I'm trying to figure out how to better explain it
AHA!!!
I got it!!!
...I think...
Tell me if I am wrong
Light is pure energy
Since nothing can have more energy than pure energy, it is therefore impossible for any object to exceed the speed of pure energy, hence, no object can exceed the speed of light.
And as for the 11 dimesions beside our own; one branch of String theory says there are 9, another says 43 (or 34; not sure but it is a random big number)
I actually replaced my random number generator with a string theorist. Whenever I need a random number, I just ask him how many dimensions there are in the universe.
With modern physics you need to have an intimate understanding of the mathematics at play behind the scenes to get anything useful out of it. Visualizing more than 4 dimensions is an excercise in futility. However, modeling in more than 4 dimensions can be useful. For example, rigorous economists and financial anylists may use thousands of dimensions to model a particular event in an effort to predict an outcome. Each dimension can be thought as just another variable, for example if an economist wants to predict the overall change in investment in a country he may choose one dimension as the interest rate of that country, another dimension as the GDP of that country and so on.
An introduction to linear algebra will give you a better understanding of what we mean when we say "dimension."
The video about imagining 10 dimensions is absolute bogus. Heres a review of the book called "Imagining the Tenth Dimension: A New Way of Thinking About Time and Space"; the book was written by the same author of the video and is meant as a complete explanation of that video:
"I bought the book, because I am a graduate student in string theory and was curious about "new" ways of thinking in ten dimensions. I knew the author of the book was actually a musician (some research with google was required for that), but so is Brian May of Queen, and his book "BANG - THE COMPLETE HISTORY OF THE UNIVERSE" is very well-written. Well, I couldn't be more wrong. Whereas Brian May studied physics (and is currently doing his long-lost PhD), Bryanton has never touched a scientific article, let alone stood near the mathematics required to grasp them. All his "knowledge" comes from science fiction (which he uses as genuine "references" for his wild ideas), popular science books (Greene, Kaku and Randall) and Scientific American.
Although the book is not intended to be a discription of "real physics", as he points out in the introduction, his ideas on ten dimensions and the alledged connection to string theory and the many worlds interpretation of quantum mechanics couldn't be stated more explicitely and couldn't be more wrong. The many world interpretation 'assumes' multiple universes in which all possible quantum processes do happen. Bryanton thinks these multiverses are in the dimensions 5 to 10. Moreover, our third spatial dimension is merely the thing "we fold through" to go from one place on a surface to another, which are not directly linked. If he is referring to the holographic principle, he's wrong there as well. Physically and mathematically, what he claims about space and time is absolute bullocks, if I may use the expression. The first chapter is exactly what is shown on his website and the rest is just a filler in which he tries to explain the ideas of quantum observation and its relation to philosophy, poorly. There is absolutely no (scientific) connection to string theory or whatsoever, except that the number 10 and the word dimensions are in the same sentence. The eleven dimensions of M-theory are in his view superfluous.
The book is perhaps intended to be scientifically and philosophically provocative, but in fact it is scientifically incorrect and at most philosophically boring. If you really want to know something about string theory and modern developments on a non-technical level, buy The Elegant Universe or The Fabric of the Cosmos by Brian Greene, Hyperspace or Parallel Universes by Michio Kaku, or Warped Passages by Lisa Randall, and your money will be well-spent. Other ideas on quantum gravity can be found in Lee Smolin's "Three Roads to Quantum Gravity". For the mathematical inclined reader (as Greene would call it in the notes), Penrose's "The Road to Reality" could be interesting, which is a brilliant mathematical exposé of theoretical physics.
Moreover, because the author does not fully understand quantum physics, his explanations are even for scientists hard to follow, because they don't seem logical. For non-scientists, I cannot recommend this book either, since I don't think it will help you in any way: you probably won't understand the science and if you do understand what the author says, you understand the wrong thing."
Jan 15, 2008
0
#36
I have Dr. Sir Roger Penrose's book Road to Reality (and several other books of his) in front of me (he mentions chess in it). He is the brother of International Master (and Correspondence GM) Jonathan Penrose of England. I think the entire Penrose family (father, 3 sons and daughter - all famous mathematicians and scientists) is one of the smartest group of people as a family that has ever lived and still has living relatives. And they all play chess.
Loomis wrote: I actually replaced my random number generator with a string theorist. Whenever I need a random number, I just ask him how many dimensions there are in the universe.
now THAT was funny.
I can only help with #1:
This may sound condescending but I do not mean it to. Read "Einstein for Beginners." It's a GREAT book that helps an inquisitive person understand the theory of relativity.
I don't think the meaning of the temperature inside a black hole would have any validity. It's like the old question about a tree falling in the woods w/ no one around to hear it. Does it make a noise? The answer's NO because we can't detect the sound vibrations. The inside of black holes are similar. We can only detect what happens outside the event horizon. Once something goes past that, it's outside of our abilities to detect exactly what's going on.
ChuckG wrote:
I don't think the meaning of the temperature inside a black hole would have any validity. It's like the old question about a tree falling in the woods w/ no one around to hear it. Does it make a noise? The answer's NO because we can't detect the sound vibrations. The inside of black holes are similar. We can only detect what happens outside the event horizon. Once something goes past that, it's outside of our abilities to detect exactly what's going on.
Does it make a noise? No? NO!!!!!???? Spoken like a true non-scientist. To make sense of that nonsense, you first have to define what a "noise" is. According to you, a "noise" is what humans hear. This is wrong. A "noise" or sound is a sinusoidal longitudinal vibration in a medium, or, in the tree's case, the movement of the air caused by the action the tree makes when falling. Just because there are no ears to register this movement does not mean there IS no movment. Then, think about the conservation of energy. The energy the tree has from it's height is first converted to kinetic energy of the movement it makes whilst falling, which is then converted to sound and heat energy when it hits the ground.
As for lack holes, no-one can say what goes on inside them. All we know is that from the outside, the Hawking Radiation makes it SEEM like they have a definite temperature.