Theory of Special Relativity

[venus/bacchus]

This is one of the most popular "modern" theories, along with possibly being one of the most important, but it's easily one of the most difficult to understand, even putting it in completely layman's terms. I've been trying for as long as I can remember to completely grasp the concepts, but I don't think my brain's capable.

Basically it comes down to this:
# The speed of light is the same for all observers, no matter what their relative speeds.
# The laws of physics are the same in any inertial (that is, non-accelerated) frame of reference. This means that the laws of physics observed by a hypothetical observer traveling with a relativistic particle must be the same as those observed by an observer who is stationary in the laboratory.

http://www2.slac.stanford.edu/vvc/theory/relativity.html

The first basically says, that unlike any other forms of energy, if you were on a train going 50 km/hr, you would see a light wave traveling at the same speed as someone who was standing and watching the train. How? I don't know. The second implies that the faster you travel, the shorter time and space become. A metal bar may be a meter long, but if you're traveling at near the speed of light, it is actually shorter. Or, when you're traveling near the speed of light, what takes 40 years on earth may take only a few "days" in the ship.

Wrap your mind around that one, I know I can't.

[_astheruinfalls]

Hm. I get it, but I don't fully grasp the bottom part.

Does that have anything to do with a feather and penny falling at the same speed if there's not gravity present? Or no?

[Tanooki Suit]

What really gets me is the speed of light. I mean, I can accept it in my head, but it doesn't mean I'll question it. Why would the speed of light be the same for someone traveling at the speed of light? Wouldn't it be essentially zero (i.e. stationary with respect to the observer)?

[Chemical Love]

i hate physics.

[venus/bacchus]

Does that have anything to do with a feather and penny falling at the same speed if there's not gravity present? Or no?
No, it's not like that at all. And that's not even true. A feather and a penny fall at the same rate if there's no air resistance present.
What really gets me is the speed of light. I mean, I can accept it in my head, but it doesn't mean I'll question it. Why would the speed of light be the same for someone traveling at the speed of light? Wouldn't it be essentially zero (i.e. stationary with respect to the observer)?
Here's what my physics book has to say about the subject:

The Speed of Light Postulate - The speed of light in vacuum has the same value c in all directions and in all inertial reference frames.

We can also phrase this postulate to say that there is in nature an ultimate speed c, the same in all directions and in all inertial reference frames. Light happens to travel at this ultimate speed, as do any massless particles (neutrinos might be an example). However, no entity that carries energy or information can exceed this limit. Moreover, no particle that does have mass can actually reach speed c, no matter how much or how long it is accelerated.
Both postulates have been exhaustively tested, and no exceptions have ever been found.

Testing the Speed of Light Postulate - If the speed of light is the same in all inertial reference frames, then the speed of light that is emitted by a moving source should be the same as the speed of light that is emitted by a source at rest in the laboratory. This claim has been tested directly, in an experiment of high precision. The "light source" was the neutral pion, an unstable, short-lived particle that can be produced by collisions in a particle accelerator. It decays into two gamma rays. Gamma rays are part of the electromagnetic spectrum (at very high frequencies) and so obey the speed of light postulate, just as visible light does.
In a 1964 experiment, physicists at CERN, the European particle-physics laboratory near Geneva, generated a beam of pions moving at a speed of 0.999 75c with respect to the laboratory. The experimenters then measured the speed of the gamma rays emitted from these very rapidly moving sources. They found that the speed of the light emitted by the pions was the same as would be measured if the pions were at rest in the laboratory.

[venus/bacchus]

I'm taking that to mean that light can't be accelerated, and is unaffected by being emitted by an "accelerating" source. Now, does that mean the same thing as someone on a train moving near the speed of light would see the same light traveling at the same speed as someone standing on earth? I have no idea.

[Tanooki Suit]

I tend to believe that neutrinos have mass (check it out, most phycists don't even know yet), and are thus not under the speed of light postulate.

[venus/bacchus]

I tend to believe that neutrinos have mass (check it out, most phycists don't even know yet), and are thus not under the speed of light postulate.
that wasn't the point....

[Tanooki Suit]

that wasn't the point....
I know.

[_astheruinfalls]

Oh, air resistence. Bah, whatever.

[_astheruinfalls]

Hm. That is weird. I have to agree with Tanooki's first post.

[venus/bacchus]

Well damnit I don't want people to tell me it's weird...I want someone to make me understand

[_astheruinfalls]

Hahaha.

Well, it's weird.

I mean, I can see the part about how how things move at the same speed, c. But basically when it comes to when other things around it are moving, I can't.

[richter915]

I'm taking that to mean that light can't be accelerated, and is unaffected by being emitted by an "accelerating" source. Now, does that mean the same thing as someone on a train moving near the speed of light would see the same light traveling at the same speed as someone standing on earth? I have no idea.
I dunno like...what I can tell is that light has both particle properties and wave properties...so if it has particle properties...it has a mass...you can assume that photons have a mass. If you were moving at the speed of light...you'd probably see just like...something amazing...just...it would like you're standing in a huge block and not moving at all (assuming you're in an empty area)...once you hit something else with a size large enough to reflect light...you'll break your face...like...bad.

ya that made no sense but just sounds kool.

[venus/bacchus]

I don't think you're supposed to assume photons have mass. That would affect a lot more than just their properties of motion. And plus, if they have mass, they can't ever move at the speed of light (which would be a problem if light can't move at its own speed). I don't really understand what you meant by the end.

[Mad Caddie]

A good, straightfoward (and animated!) explanation of the special theory of relativity is given in the very handy Encarta encyclopedia. It simplifies it down a bit for you, but i still struggle. My mind cant even handle the fact that speed has a limit. what stops something from going faster than the speed of light?? Shouldnt speed be effectively infinite?

[richter915]

I don't think you're supposed to assume photons have mass. That would affect a lot more than just their properties of motion. And plus, if they have mass, they can't ever move at the speed of light (which would be a problem if light can't move at its own speed). I don't really understand what you meant by the end.
But then...well I obviously need more education in physics to understand why photons should only be looked at as energy and not be considered to have mass. But ya...if it was assumed to have mass...everything would look different.

I dunno, my last part makes no sense if you assume there's no mass. But, I dunno I don't know much on this but...would you be able to say that what Einstein is saying...if you moved at the speed of light...you'd be able to "see" energy?

[sleepygrlgreen]

I dunno like...what I can tell is that light has both particle properties and wave properties...so if it has particle properties...it has a mass...you can assume that photons have a mass. If you were moving at the speed of light...you'd probably see just like...something amazing...just...it would like you're standing in a huge block and not moving at all (assuming you're in an empty area)...once you hit something else with a size large enough to reflect light...you'll break your face...like...bad.

ya that made no sense but just sounds kool.

ah, you're adorable when you explain things. :: pinches cheeks!!!::

i'd be more than happy to give my input on this matter, but i don't know enough about this to say ..anything educated. heh.

[richter915]

ah, you're adorable when you explain things. :: pinches cheeks!!!::

i'd be more than happy to give my input on this matter, but i don't know enough about this to say ..anything educated. heh.
ya....

venus/bacchus...reply to what I said...please.

[Bishop]

A good, straightfoward (and animated!) explanation of the special theory of relativity is given in the very handy Encarta encyclopedia. It simplifies it down a bit for you, but i still struggle. My mind cant even handle the fact that speed has a limit. what stops something from going faster than the speed of light?? Shouldnt speed be effectively infinite?

Well there is such a thing as terminal velocity, although that only applies to places where gravity comes into play and even then I don't think you'd always be falling at the same rate if the strength of the gravitational pull varies from planet to planet.

[Bishop]

My Astronomy teacher talked about this some this past week, an interesting conjecture. I asked him some more about it and he says he can't really go into that without dealing with String Theory and I started reading up on it some and my head is still hurting.

[venus/bacchus]

But then...well I obviously need more education in physics to understand why photons should only be looked at as energy and not be considered to have mass. But ya...if it was assumed to have mass...everything would look different.

I dunno, my last part makes no sense if you assume there's no mass. But, I dunno I don't know much on this but...would you be able to say that what Einstein is saying...if you moved at the speed of light...you'd be able to "see" energy?
I think you need to try to put out the entire idea of mass/no mass out of your head. That has very little to do with the theory (except that nothing of mass can travel at the speed of light). Really, mass is just concentrated energy, so they're one in the same.

You also need to remember that we always "see" energy in the form of "light" waves (an easier way of describing all electromagnetic waves). The visibility is not the problem, rather it's the light's behavior as it travels that is the problem. Here's what it comes down to: If you're on a train traveling at 50 mph and you threw a baseball forward at 30 mph, you would see the baseball traveling at 30 mph. If I was standing on the platform watching the train go by, I'd see the baseball traveling at 80 mph. Fairly obvious and pretty simple if you ask me. Now, if you were to shine a flashlight while you were on the same train and somehow I could watch the lightwaves because my eyes were sensitive enough, the light waves would travel the same speed to you and to me. The fact that you're moving at a constant velocity on the train has no bearing on the speed of the light being emitted from the flashlight. If we both chose a single point on the light wave and watched it, we'd see that single point travel at the same speed, regardless of our reference point or relative velocity. How is that possible?
Well there is such a thing as terminal velocity, although that only applies to places where gravity comes into play and even then I don't think you'd always be falling at the same rate if the strength of the gravitational pull varies from planet to planet.
Gravity exists everywhere in the universe. There are no points in which you don't have some sort of force being exerted on you. Terminal velocity only applies in situations when there is air resistance.

[Bishop]

Fuck.

[richter915]

wow.

I wish I could understand.

[richter915]

ok venus/bacchus...I spent like three hours last night researching up on special relativity and I say...my head is still in some pain. I think the "freakiest" oddity associated with special relativity is time dilation. Like the whole twin spaceship thing...it's really interesting but you're right...I have no idea how it could be explained and how exactly Einstein even postulated that. When you see the world in Einstein's eyes, the fact that he wanted time as a fourth dimension makes perfect sense but it's so difficult to grasp that when we live in a "3D" world.

length contraction is even more messed up...the length stays the same but it looks smaller to you...so...man, I don't even know my head hurts even more now.

please more comments and thoughts...and then we can go into how this relates to time travel...yay.

[Tanooki Suit]

Well, length contraction is just a form of the doppler effect, right? If you're moving towards a source, the waves are going to appear to have a higher frequency, and vice versa.

[richter915]

I don't think it's as simple as the doppler effect mainly cause the doppler effect applies mostly to sound and sound is a whole different thing. It might relate but I dunno.

from what I know though, length contraction involves two people moving at near the speed of light and looking at an object the other person has...and that object looks smaller...I would really like to know why that is...it's really really freaky but not nearly as interesting as time dilation.

[richter915]

Hey venus/bacchus...look into the Lorentz Transformations...I think they're the set of mathematical equations that allow you to convert values from one frame of reference to another....so it applies from going from the time frame of reference to length etc. I think Einstein used this with SR...SR actually helped prove the Lorentz Transformations...if you could understand those, I think you'll answer your questions on length contraction/time dilation.

tanooki suit, I made a mistake with my post...I was wrong in saying that both were moving at the speed of light...you have the observer and the person moving at the speed of light...I dunno if it has any relationship with the doppler effect though.

[osunfg]

man am i happy i found this thread :)
alright, time to spit out the info i know on light, relativity, quanta, time travel, etc.

*on a side note, a very very awesome read that introduces relativity, quantum mechanics, and combines them with string theory is Brian Greene - The Elegant Universe.

where to begin?
the doppler effect is one of the main topics that people need to grasp. although light always has its constant speed in a vacuum, it doesnt always have the same energy. while the speed of light may be the 'universal speed limit', even if u have the speed of light, plus the source moving at a speed, the speed of light will remain constant. however the difference is turned into energy. rather than staying at the constant spectra, it will shift accordingly to how fast it is moving towards you or away from u. a light source moving towards u will emit a spectra closer to the high energy waves (xray, gamma), while a light source moving away from u will produce spectra closer to the lower energy waves (radio, microwave). i dont know if that helps anyone understand the race between 2 waves of light moving at different speeds.

as with the understanding of time and space, its necessary to think of them as one in the same, as spacetime. time is solely dependent on space, and as u warp the field of space, we also warp time. that is why in einsteins theory of relativity, he expresses space much like a trampoline, with masses creating dents, such as placing a bowling ball on that trampoline. the field created is than that objects gravitational field. (on a side note, we dont even know what gravity is, which is a fucked up in its own)
that is why if we can travel to the future by chilling outside a black holes event horizon. the gravitational effects warp space so much, that time will fly by for us, relative to another observer. both observers however would experience the same amount of time personally passing. which is why it is a lot easier to 'possibly' travel to the future. in order to travel to the past, we would need to surpass the speed of light, which is arguable with current physics.


i've written enough as it is, so i'll leave it at that for now. i'll probably post more later.

[when 4ever ends]

haha and you think this is hard, try reading anything by stephan hawking... i cant even spell his god damn name right.

[burningwithin]

the most interesting part of physics is when you get into theoretical physics and astrophysics.

string theory, m-theory, brane theory = fun stuff.

now, the idea of holographic universe is the type of New Age physics type of stuff that's just makes a mockery of science. hehe. as you can tell i'm going to be a physics major in college,

=)

[scitsofreaky]

A good, straightfoward (and animated!) explanation of the special theory of relativity is given in the very handy Encarta encyclopedia. It simplifies it down a bit for you, but i still struggle. My mind cant even handle the fact that speed has a limit. what stops something from going faster than the speed of light?? Shouldnt speed be effectively infinite?
As mass' velocity increases, it's mass increases (but sadly I don't remember the damn equation) perportionally, and as it's mass increases, it takes more energy to move, and when mass reaches the speed of light its weight in infinite, so it would take an infinite amount of energy to keep it moving. I think it is something along those lines, but I'm not positive.

[richter915]

the most interesting part of physics is when you get into theoretical physics and astrophysics.

string theory, m-theory, brane theory = fun stuff.

now, the idea of holographic universe is the type of New Age physics type of stuff that's just makes a mockery of science. hehe. as you can tell i'm going to be a physics major in college,

=)
ya I was looking stuff up on string theory. Did not get it at all...care to explain for me? thanks.

[Alan Rupp]

Buuuuuuuump.

[richter915]

Buuuuuuuump.
nice! I'm so glad u did...I was so stupid back then haha.

alright I was talking about it today with my brother cause my physics class won't teach this...alright...with time dilation and the whole twin paradox...my friend once told me that the brother in the ship will see him and his brother the same age the whole time but only when he decelerates back to v=0 will he see his brother age. Is there any validity to that? If so, what makes it the case?

[Alan Rupp]

nice! I'm so glad u did...I was so stupid back then haha.

alright I was talking about it today with my brother cause my physics class won't teach this...alright...with time dilation and the whole twin paradox...my friend once told me that the brother in the ship will see him and his brother the same age the whole time but only when he decelerates back to v=0 will he see his brother age. Is there any validity to that? If so, what makes it the case?
I think it's safe to say we were all much dumber. It was a year and a half ago. Anyway:

That's not true at all. For instance, imagine that the Earth brother were holding a digital clock and it was large enough to be visible from the spaceship. Now imagine that the spaceship brother also had the same clock. As he traveled at near the speed of light, he would be able to look at both clocks at the same time and it would be obvious that they were not going at the same rate, and thusly, he would be able to tell that their ages were not progressing at the same rate.

I think the easiest way to picture this situation is an example Stephen Hawking used. I'll summarize:

Let's define a second as the time it takes a photon to reflect from a light source to a mirror and back. Now let's assume there is also a mirror on the other end, so the photon is constantly moving back and forth between the two mirrors. Everytime it makes a round-trip, that's one second.

Now, let's put the apparatus on a wheeled cart. If we set the cart in motion, the photon now has to travel a further distance because it is traveling at a diagonal path, but it always must travel at the same speed to all observers.

So let's assume there is one person watching the cart go by and one person sitting on the cart. To the person watching the cart, the photon is traveling in its obviously diagonal path (or else it wouldn't hit both mirrors). However, to the person riding on the cart, the photon would be simply going back and forth and tracing the same path because he has no perception of the motion of the cart. Therefore, "time" (as defined above) would be different for both people watching the same event.

That's in essence how that same digital clock analogy works.

[richter915]

I think it's safe to say we were all much dumber. It was a year and a half ago. Anyway:

That's not true at all. For instance, imagine that the Earth brother were holding a digital clock and it was large enough to be visible from the spaceship. Now imagine that the spaceship brother also had the same clock. As he traveled at near the speed of light, he would be able to look at both clocks at the same time and it would be obvious that they were not going at the same rate, and thusly, he would be able to tell that their ages were not progressing at the same rate.

I think the easiest way to picture this situation is an example Stephen Hawking used. I'll summarize:

Let's define a second as the time it takes a photon to reflect from a light source to a mirror and back. Now let's assume there is also a mirror on the other end, so the photon is constantly moving back and forth between the two mirrors. Everytime it makes a round-trip, that's one second.

Now, let's put the apparatus on a wheeled cart. If we set the cart in motion, the photon now has to travel a further distance because it is traveling at a diagonal path, but it always must travel at the same speed to all observers.

So let's assume there is one person watching the cart go by and one person sitting on the cart. To the person watching the cart, the photon is traveling in its obviously diagonal path (or else it wouldn't hit both mirrors). However, to the person riding on the cart, the photon would be simply going back and forth and tracing the same path because he has no perception of the motion of the cart. Therefore, "time" (as defined above) would be different for both people watching the same event.

That's in essence how that same digital clock analogy works.
alright I think I'm starting to understand it. Just to make sure I understand this...the clock for the brother on earth would be going at a faster rate than the clock on the ship, right? This is from the ship brother's POV...but from the earth Brother's POV...the ship brother's clock is going slower. Same thing with the photons and the cart...to the stationary brother, it takes longer for the photons to make one cycle but that's not the case for the brother on the cart.

ok with the example of the carts now...I have a new question. If we assume that time is based on the linear movement of the photon...just by changing it's vectors it causes a change in time, right? Is that how it works in reality too? How does the theory explain this whole change in time?

oh another question...I'm always hearing about spacetime...is that just an x-y axis with one being space, the other being time? If you were to graph the position of a planet relative to time, you'd get a sin wave, right?

[Alan Rupp]

alright I think I'm starting to understand it. Just to make sure I understand this...the clock for the brother on earth would be going at a faster rate than the clock on the ship, right? This is from the ship brother's POV...but from the earth Brother's POV...the ship brother's clock is going slower. Same thing with the photons and the cart...to the stationary brother, it takes longer for the photons to make one cycle but that's not the case for the brother on the cart.

ok with the example of the carts now...I have a new question. If we assume that time is based on the linear movement of the photon...just by changing it's vectors it causes a change in time, right? Is that how it works in reality too? How does the theory explain this whole change in time?

oh another question...I'm always hearing about spacetime...is that just an x-y axis with one being space, the other being time? If you were to graph the position of a planet relative to time, you'd get a sin wave, right?
Well that's where it gets tricky. The brother on earth would perceive the space brother's clock to be moving slower, yes, but it's best to think of things in terms of one person, and for simplicity I'll stick to the one on the ship.

The problem with this example is that it's not from a completely inertial reference point. Remember, he has to turn around and come back towards Earth, and even if he maintains the same speed, by changing direction, he's accelerating. It's very difficult to explain, I don't know what to say.

I'd suggest just reading this (http://en.wikipedia.org/wiki/Twin_paradox). It does a lot better job than I ever could.

About the changing the vector of the photon, I don't think it can work that way, but I don't know for sure. That was just an example to give a physical definition of time in something we can understand. Photons change direction and vectors all the time. That doesn't mean time is constantly changing. But I'll have to read up more on it.

Well, to be specific, you should probably draw spacetime as a three-dimensional graph with planes cutting through it at different intervals to represent various times. Kind of like an f(x,y,z) graph from multivariable calculus.

[richter915]

"In a sense, during the U-turn the plane of simultaneity jumps from blue to red and very quickly sweeps over a large segment of the lifeline of the resting twin. The resting twin has suddenly "aged" very fast, in the reckoning of the traveling twin."

I think this is what I was talking about...they explained 3 frames of reference and that when the turn is made...inertial forces (acceleration/deceleration) take place and in that time period, the resting twin ages faster. I think that Minkowski diagram explained it pretty well. What do you think?

[mps]

Well there is such a thing as terminal velocity, although that only applies to places where gravity comes into play and even then I don't think you'd always be falling at the same rate if the strength of the gravitational pull varies from planet to planet.

Terminal velocity really doesn't have much to do with this. Terminal velocity just determines the maximum speed at which an object can fall under gravity in an atmosphere (it is all about air resistance). An object will reach terminal velocity when it's drag is directly proportional to the square of its speed.

[mps]

man am i happy i found this thread :)
alright, time to spit out the info i know on light, relativity, quanta, time travel, etc.

*on a side note, a very very awesome read that introduces relativity, quantum mechanics, and combines them with string theory is Brian Greene - The Elegant Universe.

where to begin?
the doppler effect is one of the main topics that people need to grasp. although light always has its constant speed in a vacuum, it doesnt always have the same energy. while the speed of light may be the 'universal speed limit', even if u have the speed of light, plus the source moving at a speed, the speed of light will remain constant. however the difference is turned into energy. rather than staying at the constant spectra, it will shift accordingly to how fast it is moving towards you or away from u. a light source moving towards u will emit a spectra closer to the high energy waves (xray, gamma), while a light source moving away from u will produce spectra closer to the lower energy waves (radio, microwave). i dont know if that helps anyone understand the race between 2 waves of light moving at different speeds.

as with the understanding of time and space, its necessary to think of them as one in the same, as spacetime. time is solely dependent on space, and as u warp the field of space, we also warp time. that is why in einsteins theory of relativity, he expresses space much like a trampoline, with masses creating dents, such as placing a bowling ball on that trampoline. the field created is than that objects gravitational field. (on a side note, we dont even know what gravity is, which is a fucked up in its own)
that is why if we can travel to the future by chilling outside a black holes event horizon. the gravitational effects warp space so much, that time will fly by for us, relative to another observer. both observers however would experience the same amount of time personally passing. which is why it is a lot easier to 'possibly' travel to the future. in order to travel to the past, we would need to surpass the speed of light, which is arguable with current physics.


i've written enough as it is, so i'll leave it at that for now. i'll probably post more later.

We know that every 'force' must have an exchange particle. There are four 'forces' in the universe. Weak nuclear force, strong nuclear force, electrostatic force, and gravity. We believe that this exchange particle is called a graviton, and is most likely in a different dimension.

Talking about 'chilling outside a black holes event horizon' (that is if black holes actually exist, and are not just dark energy stars - quantum mechanics do not allow black holes to exist as in quantum mechanics absolute time is required)...but yes, back to general relativity, you cannot actually ever pass the event horizon, because spacetime is warped so much that time itself begins to pass infinitly slowly (think of it as an asymptote on a graph - you never actually get to the asymptote, you just 'tend' towards it).

FTL (Faster Than Light) travel...I'd like to go into a discussion about that, but I have to go soon, so let's save it for another day.

[mps]

I tend to believe that neutrinos have mass (check it out, most phycists don't even know yet), and are thus not under the speed of light postulate.

Neutrinos have no rest mass, or very very little. Anyways, if you think like that, then are you saying that you think light has no mass at all then? It must have at least some mass if it is a particle (photon), although we generally say it has no rest mass. This means that light exerts pressure when it falls on things. Look up 'the pressure of light' or something, it's quite interesting.

E=cp

Where p is momentum. :thumbsup:

[mps]

the most interesting part of physics is when you get into theoretical physics and astrophysics.

string theory, m-theory, brane theory = fun stuff.

now, the idea of holographic universe is the type of New Age physics type of stuff that's just makes a mockery of science. hehe. as you can tell i'm going to be a physics major in college,

=)

I talked about M-theory with richter once...I wish I could find that thread.

[richter915]

Neutrinos have no rest mass, or very very little. Anyways, if you think like that, then are you saying that you think light has no mass at all then? It must have at least some mass if it is a particle (photon), although we generally say it has no rest mass. This means that light exerts pressure when it falls on things. Look up 'the pressure of light' or something, it's quite interesting.

E=cp

Where p is momentum. :thumbsup:
ya you're definitely right with that...I don't know much about the rest mass with neutrinos bit but I know that light exerts pressure...those solar sails work like that...really thin sheets that're pushed by the pressure of light.

[mps]

ya you're definitely right with that...I don't know much about the rest mass with neutrinos bit but I know that light exerts pressure...those solar sails work like that...really thin sheets that're pushed by the pressure of light.

Solar sails work with the solar wind mainly I think (?). But yeah, they take a looong time to pick up speed, but they never stop accelerating, and require no fuel.

[richter915]

Solar sails work with the solar wind mainly I think (?). But yeah, they take a looong time to pick up speed, but they never stop accelerating, and require no fuel.
solar wind isn't the same as pressure due to the photons? But ya...I don't know the purpose of solar sails...can you hook em up to satellites and shit?

[mps]

solar wind isn't the same as pressure due to the photons? But ya...I don't know the purpose of solar sails...can you hook em up to satellites and shit?

Nah, the solar wind is not photons. Charged particles, like electrons and protons in a plasma.

Oh, and yeah of course solar sails can be hooked up to probes. I made a mistake before when I said it was the solar wind which accelerates them. You are correct, it is pressure from radiation (photons) that propels it. The force due to light pressure is about 100 times as strong as that due to solar wind (which can be up to 800km/s fast at times!), so I was wrong. Sorry, hah.

[richter915]

Nah, the solar wind is not photons. Charged particles, like electrons and protons in a plasma.

Oh, and yeah of course solar sails can be hooked up to probes. I made a mistake before when I said it was the solar wind which accelerates them. You are correct, it is pressure from radiation (photons) that propels it. The force due to light pressure is about 100 times as strong as that due to solar wind (which can be up to 800km/s fast at times!), so I was wrong. Sorry, hah.
hah funny we're discussing this...today at my Physics review class he explained how solar winds work and said exactly what you and I said.

[mps]

hah funny we're discussing this...today at my Physics review class he explained how solar winds work and said exactly what you and I said.

Hahaha, cool. What other stuff did you do?

[richter915]

Hahaha, cool. What other stuff did you do?
eh, not much...our final is in a week and a half so we went over mostly nuclear/modern physics. We mighta done optics but I had left by then. The nuclear physics we are doing is really really basic and is mostly conceptual...I learned 95% of it in freshman chem too so I'm not too concerned.

I'm thinking of starting a thread on quantization and quantum physics cause I have a few questions on what it means at the core of it all. Like, my professor just started quantum one day and (like he did with vectors) just kinda assumed we knew it. It's not that he does that to screw us over...it's just...he knows that 99% of the class doesn't care for the concept...but more for how to solve different kinds of questions...I fall in that 1% that needs to know the concept though, hah.

[mps]

eh, not much...our final is in a week and a half so we went over mostly nuclear/modern physics. We mighta done optics but I had left by then. The nuclear physics we are doing is really really basic and is mostly conceptual...I learned 95% of it in freshman chem too so I'm not too concerned.

I'm thinking of starting a thread on quantization and quantum physics cause I have a few questions on what it means at the core of it all. Like, my professor just started quantum one day and (like he did with vectors) just kinda assumed we knew it. It's not that he does that to screw us over...it's just...he knows that 99% of the class doesn't care for the concept...but more for how to solve different kinds of questions...I fall in that 1% that needs to know the concept though, hah.

What nuclear physics are you doing?

And yes, please do! We can then debate the existance of black holes, as quantum mechanics does not allow for their existance.

[richter915]

What nuclear physics are you doing?

And yes, please do! We can then debate the existance of black holes, as quantum mechanics does not allow for their existance.
just things with decay, fission, fusion...blackbody radiation...a lot of stuff with energy, photoelectric effect...nothing that complex at all. If he has time he's gonna teach us stuff with bombs, nuclear reactors, and physics in medicine (MRI, PET scans, etc).

[mps]

Bump!