That system is broken and useless for writing useful program. The posix subsystems support the minimal posix standard and microsoft implemented this because at that time goverment computer were supposed to be posix compilant.
I am not a physicist so all my understanding comes about the relativity comes from this article.
My orginal question was how come the universe can expand at the rate which is faster than light and still be consistent with the relativity. I think I understand now why this is possible and this is all because of your and other posters.
Your explanation also explained for the first time to me what is background radiation and why its microwave. So thanks.
All right. Consdier Alice and Bob are being carried along by expanding space but they are motionless themselves. Also, assume that the rate of expansion is less than the speed of light. Q1. Will Alice actually see Bob clock slowing down ? Ans: Yes. Not see as in it takes some amount of time for the light to reach Alice but see as it in Alice adjust the time by taking that time in account. For example if Alice sees that the Bob clock is 1200 hrs and Bob at that time is 1 light hour away then Alice will assume that actual time on Bob clock is 1100 hrs. Alice's clock will then say something like 1130 hrs. And Alice will assume that Bob clock is slowing down.
Also all the relativistic effect will be visible for Alice. Bob will be heavier etc.
In case when the expansion rate is more than the speed of light, Bob will be out of event horizon of Alice and hence will not observe anything about Bob. Not only that, every other point in the space will be out of event horizon of Alice( like Alice is in a black hole) hence the relativity does not hold because Alice cannot observe.
I believe that whether space expand or their is motion, according to relativity the effect should be same.
Thanks for the answer. I am not a physicist so bear with me. The problem with your explanation is that you say when time slows down because the observer SEE it slowing. This is not the case, the time actually slows down. you can make correction for the speed of light still you will see the clock slowing down.
Consider my example. Alice is travelling in a train and Bob is in the platform. On the train floor is a light source which sends a beam straight up the ceiling. On the ceiling is a mirror which reflects the light down. The experiment here is to measure the time taken for a photon to leave the source and come back again. For Alice the photon goes straight up and then comes down so the time will be t = 2*h/c where h = height of the train and c = speed of light For Bob, since he sees the train is moving the photon is moving diagnally up and then diagonlly down. The distance travelled by the photon is more than what Alice sees. Now in Newtonian mechanics this is fine because the train speed will be added to the photon speed. But according to Einstien, if one observer sees the object moving with the speed of light then ALL observer will see that the object is moving with the speed of light. This means that Bob will see the photon moving with the speed of light. But the photon has to move more distance. Now here is the problem the same experiment which both Bob and Alice are measuring finishes at different time. Bob has to conclude that the Alice clock was slowed down.
Now for the original question I asked, I have understoon as follows. The two point on the balloon can move faster than the speed of light because 1. The points are moving away with every other point on the surface of the balloon. 2. Consider some point on the surface. This point will be outside the event horizon of all the points hence it cannot observe the event happening on any other point. Hence the relativity is not broken.
All right. That explains why the causality is not broken. What about the other problem ?
Suppose there are two ant then the ant see the other ant moving away with the speed of light. this means the clock in the other ant frame of reference has stopped and the ant has infinite mass.
Perfectly clear now. This is why the Alcubierre drive can travel faster than light. I thinnk the same princile is behind the fictitious star trek warp drive.
First, thanks for your explanation. If I understand you correctly then you are saying that if there is a particle at some point and the point is moving because of expansion then the particle will not move with the point (or with the same rate)
Pardon me but if the universe expanded in such a manner wouldn't that be against the theory of relativity. What about breaking causality ? Perhaps this is a foolish question.
Thanks for the explanation. I am a doctor not a physicist.:) After the post, I found the problem with my model. The photon has to move with the speed of light in all frame of reference hence there will be resultant momentum and hence momentum will not be conserved.
Let me say that you are right but I still have some doubt. After the collison the reference frame is still moving along with the photon so the momentum is zero after the collison.
Yes you can conserve momentum with a single photon except in head on collison. It is true however that there are always two photon.
Consider that the electron is moving in south east direction and positron in north east. When they collide their north - south momentum will cancel out. Now the only remaining momentum is in the east direction. This momentum will be the momentum of the photon moving in the east direction. The reason the momentum cant be conserved during head on collison is that the resultant momentum has to be zero and single photon will have a mometum.
Yes you are right. The momentum can be conserved even in one photon case except when the electron and positron are colliding head on. Still the resultant photon will be in gamma ray frequency 1.23*10^20 Hz.
Here is the math.. E = 2mc^2 E = h*frequency Frequency of the photon = 2 m*c*c/h where m = mass of electron c = speed of light h = planck constant Now according to google m = 9.109*10^-31 c= 3*10^8 h = 6.63 *10-34 frequency comes out to be 2.47*10^20 hertz which comes under gamma rays. So indeed the positron+electron will produce gamma rays
Why do you say that ? If an electron and positron react you get a photon and gamma ray is a high energetic photon. I am sure, that when the heavy subatomic particle like neutron, proton are mixed with their anti counterpart you may have gamma "particle" coming out.
In the textbook fo biochemestiry by Lehinger, he asked this question about silcon based life and then answer the question in negative. The reason he gave was that the bonding between silicon and oxygen is very strong and difficult to break.
I disagree. I believe that morality has come to us from the evolution itself and can be explained by science. In order for human species to surive as a social animal we need certain rules/guidelines which may seems to be against the natural selection but necessary for the survival of the society. So, the goodness of my heart, humanity, ethics, morality and even religion have all have roots in survival of the fittest.
I agree with you. Larry Niven is more of lefty. If you read his novel and stories there is a little mention of religon and from his discussion of organleggers in his books I assume he will favor stem cell research.
Slashdot Mirror
How come ?
C++ is almost a superset of C(99% of the C code will compile in C++)
That system is broken and useless for writing useful program. The posix subsystems support the minimal posix standard and microsoft implemented this because at that time goverment computer were supposed to be posix compilant.
First of all, I understood you loud and clear. Your explanation was lucid but I have to respectfully disagree with your explanation.
/ . The article explains that how the time slows down.
I also cheated here, because what I explained was not my explanation. You can read it from
http://www.physicsguy.com/ftl/html/FTL_part1.html
I am not a physicist so all my understanding comes about the relativity comes from this article.
My orginal question was how come the universe can expand at the rate which is faster than light and still be consistent with the relativity. I think I understand now why this is possible and this is all because of your and other posters.
Your explanation also explained for the first time to me what is background radiation and why its microwave. So thanks.
All right. Consdier Alice and Bob are being carried along by expanding space but they are motionless themselves. Also, assume that the rate of expansion is less than the speed of light.
Q1. Will Alice actually see Bob clock slowing down ?
Ans: Yes.
Not see as in it takes some amount of time for the light to reach Alice but see as it in Alice adjust the time by taking that time in account. For example if Alice sees that the Bob clock is 1200 hrs and Bob at that time is 1 light hour away then Alice will assume that actual time on Bob clock is 1100 hrs. Alice's clock will then say something like 1130 hrs. And Alice will assume that Bob clock is slowing down.
Also all the relativistic effect will be visible for Alice. Bob will be heavier etc.
In case when the expansion rate is more than the speed of light, Bob will be out of event horizon of Alice and hence will not observe anything about Bob. Not only that, every other point in the space will be out of event horizon of Alice( like Alice is in a black hole) hence the relativity does not hold because Alice cannot observe.
I believe that whether space expand or their is motion, according to relativity the effect should be same.
Thanks for the answer.
I am not a physicist so bear with me. The problem with your explanation is that you say when time slows down because the observer SEE it slowing. This is not the case, the time actually slows down. you can make correction for the speed of light still you will see the clock slowing down.
Consider my example. Alice is travelling in a train and Bob is in the platform. On the train floor is a light source which sends a beam straight up the ceiling. On the ceiling is a mirror which reflects the light down. The experiment here is to measure the time taken for a photon to leave the source and come back again. For Alice the photon goes straight up and then comes down so the time will be
t = 2*h/c where h = height of the train and c = speed of light
For Bob, since he sees the train is moving the photon is moving diagnally up and then diagonlly down. The distance travelled by the photon is more than what Alice sees. Now in Newtonian mechanics this is fine because the train speed will be added to the photon speed. But according to Einstien, if one observer sees the object moving with the speed of light then ALL observer will see that the object is moving with the speed of light. This means that Bob will see the photon moving with the speed of light. But the photon has to move more distance. Now here is the problem the same experiment which both Bob and Alice are measuring finishes at different time. Bob has to conclude that the Alice clock was slowed down.
Now for the original question I asked, I have understoon as follows. The two point on the balloon can move faster than the speed of light because
1. The points are moving away with every other point on the surface of the balloon.
2. Consider some point on the surface. This point will be outside the event horizon of all the points hence it cannot observe the event happening on any other point. Hence the relativity is not broken.
I agree with all other explanation. T
All right. That explains why the causality is not broken. What about the other problem ?
Suppose there are two ant then the ant see the other ant moving away with the speed of light. this means the clock in the other ant frame of reference has stopped and the ant has infinite mass.
Perfectly clear now. This is why the Alcubierre drive can travel faster than light.
I thinnk the same princile is behind the fictitious star trek warp drive.
First, thanks for your explanation.
If I understand you correctly then you are saying that if there is a particle at some point and the point is moving because of expansion then the particle will not move with the point (or with the same rate)
Are you saying that the universe will honor the rule only if no one is sending the signal ?
Pardon me but if the universe expanded in such a manner wouldn't that be against the theory of relativity. What about breaking causality ?
Perhaps this is a foolish question.
Thanks for the explanation. I am a doctor not a physicist. :)
After the post, I found the problem with my model. The photon has to move with the speed of light in all frame of reference hence there will be resultant momentum and hence momentum will not be conserved.
Let me say that you are right but I still have some doubt. After the collison the reference frame is still moving along with the photon so the momentum is zero after the collison.
You mean momentum.
Yes you can conserve momentum with a single photon except in head on collison. It is true however that there are always two photon.
Consider that the electron is moving in south east direction and positron in north east. When they collide their north - south momentum will cancel out. Now the only remaining momentum is in the east direction. This momentum will be the momentum of the photon moving in the east direction.
The reason the momentum cant be conserved during head on collison is that the resultant momentum has to be zero and single photon will have a mometum.
Yes you are right.
The momentum can be conserved even in one photon case except when the electron and positron are colliding head on.
Still the resultant photon will be in gamma ray frequency 1.23*10^20 Hz.
Here is the math..
E = 2mc^2
E = h*frequency
Frequency of the photon = 2 m*c*c/h
where m = mass of electron c = speed of light
h = planck constant
Now according to google
m = 9.109*10^-31 c= 3*10^8 h = 6.63 *10-34
frequency comes out to be 2.47*10^20 hertz
which comes under gamma rays.
So indeed the positron+electron will produce gamma rays
Why do you say that ?
If an electron and positron react you get a photon and gamma ray is a high energetic photon. I am sure, that when the heavy subatomic particle like neutron, proton are mixed with their anti counterpart you may have gamma "particle" coming out.
The density of the coal sack nebulae is around 100-300 molecules per cm*cm. Hence, his arguments are still valid.
No the cat is resting.
H2S is hydrogen sulphide, S here is for Sulphur. Formula for silicon is Si
In the textbook fo biochemestiry by Lehinger, he asked this question about silcon based life and then answer the question in negative. The reason he gave was that the bonding between silicon and oxygen is very strong and difficult to break.
I disagree. I believe that morality has come to us from the evolution itself and can be explained by science. In order for human species to surive as a social animal we need certain rules/guidelines which may seems to be against the natural selection but necessary for the survival of the society. So, the goodness of my heart, humanity, ethics, morality and even religion have all have roots in survival of the fittest.
I agree with you. Larry Niven is more of lefty. If you read his novel and stories there is a little mention of religon and from his discussion of organleggers in his books I assume he will favor stem cell research.
I believe that Heinlein was both right wing and left wing as far as his writing goes. His book "Moon is a harsh mistress" is decidedly lefty.
May I also suggest using BoostPython library to embed python into your c++ program(or viceversa)
OT.
I read The End of Eternity waaaaaaaaay back. why then you call it as a lost masterpiece ?
just wondering.