|
Light, gravity, and time...
Link |
by S-a-c-h-i-e-l
on 2006-01-09 14:19:34
|
|
I checked as well as I know, and as far as I know this has not been metioned yet. If I'm wrong, let me know and I'll lock this thread T.T People say that the more dense an object is, the more gravity it gets. What I want to know is what makes the gravity come out of the object. This could easily be a stupid question, but everyone I've asked doesn't know. And on the light part, is it possible that time and light are the same thing? Studies and experiments have been done, and it appears that the faster you go the slower time goes. So in essence, the closer to the speed of light you get the less influence light has on you, so maybe light and time are really the same thing... And if huge amounts of gravity comes near light, light will be "sucked in" by the gravity, thus making black holes and such. So what is light then? Extremely fast light-producing particles? But if light can get pulled in by gravity, then light is obviously not formless then. So light must have form then... >_< This is confusing me... Well, feel free to reply, although this is most likely seriously flawed as I'm a total newb in physics and I'm only 15... T.T  |
|
Re: Light, gravity, and time...
Link |
by
on 2006-01-09 14:43:31 (edited 2006-01-09 14:47:59)
|
|
Re: gravity According to general relativity, "gravity" is the bending of space-time in the presence of massive particles. The massive particles include: protons, nutrons, electrons, and (maybe!) the nutrino. The more dense an object is, the more particles are packed into a smaller space, and therefore the more particles overall. Things we often interact with (people, books, food, trees) are made of matter. This matter is composed of atoms which are bundles of mixed protons, nutrons, and electrons that hold themselves together. Hope that helps you understand a bit more. Re: light Light is an electromagnetic wave propagating in space-time. Time is the concept we use to measure one of the 4 simple dimensions of space-time. Another is length. I could argue that the faster I go, the more distance i travel in a second. This does not make me "length" itself. Re: time Light is a wave. When you jump in a lake, waves move out from where you broke the water's surface. In space-time, when a photon changes energy-levels, it produces a light wave. The particle which produces light need not travel with the light wave. That is why you can see a flashlight from far away. Re: form What do you mean by "form"? If you mean something you can feel with your hand, light has "form" because the sun heats up your hand when you put it in the sunlight. If you mean does it bend space-time, then no. Light has no rest-mass, which is to say it weighs nothing when at rest (and it can never be at rest, either). Re: black holes All particles (massive or otherwise) are sucked into black holes because space-time is bent around it. To understand this, picture a large bed sheet spread out so it is laying flat. Put a bowling ball in the middle. the ball sinks down in the sheet, pulling the sheet down around it. anything you place on the sheet will roll down towards the bowling ball. Your questions are not stupid at all! It makes me happy that you are interested in physics, and i am glad to help explain where i am able. 
|
|
Re: Light, gravity, and time...
Link |
by S-a-c-h-i-e-l
on 2006-01-09 19:50:12
|
|
Well, why can't light stop moving? And if light did stop, would we see it? You can't see the light a lamp produces, you see the light bouncing off of other objects. So... why can't we see light while it is still in the air? Why is it we only "see" light when it hits something? Yes, I know that stuff on gravity, but what makes gravity in the first place? Why is it that large objects (or dense objects) want to pull more things to it? And let's say that I suddenly teleport out of my home onto Mars (and I don't die and can breathe). I would be looking at Earth the way it was a while ago, because the light that I saw on Earth would still be on Earth but I would be on Mars. So, did I in essence time travel? |
|
Re: Light, gravity, and time...
Link |
by
on 2006-01-09 20:19:10 (edited 2006-01-09 20:29:03)
|
|
Well, why can't light stop moving? This is the same as asking why cant a wave in the ocean stop moving. You can cancel out the wave with another one, or smash it up against a wall. But that is destroying the wave, once you have done so, there is no wave left to be "stopped". If you take a wave in water, stop all the particles from moving relative to the observer, you no longer have a wave; you have a solid object! Why is it we only "see" light when it hits something? The mechanism for humans to see light is the eyes. When a photon hits our eyes, it interacts with our cells which send a signal to our brain. why can't we see light while it is still in the air? If, at some moment, a photon of light is in a space filled in front of you, it has not yet interacted with your eyeball, so you have not yet seen it. Later, it may travel towards and hit your eye. Once it does, the signal travels to your brain. That is when you "see it". You can't see the light a lamp produces... Not true. Stare directly at the lamp. Some photons will be produced in the filament of the light bulb, which travel strait towards your eye. what makes gravity in the first place? gravity is a field in physical theory. it is not something you can see, feel, hear, or smell directly. this makes it hard to understand. nevertheless, it is an explanation that allows scientists to make predictions about how the universe works. that is its value. in classical times it was thought that angels held the sun, moon, stars, and planets in the heavens. the angels were believed to cause the movement of these celestial bodies by flapping their wings. in modern physics we have replaced the angels with gravity. nothing else has changed. a better answer to your question does not yet exist to my knowledge. Your teleportation idea is a good start, but it needs some refinement. Lets say you are already on mars in your mars base with a space suit. You have an atomic clock, and you have synchronized it with mine. That is to say, you call me at noon and i receive the message a second after noon, but I know it took a second for the signal to reach me, because i know how far away mars is, and i know the speed of light, so i know you called me precisely at noon. A volcano erupts on earth at midnight and you see the light from the eruption. Later, you tell me you saw the eruption happen at 1:00:01 PM. I know that the eruption happened at 1:00:00 because i was very close by when it happened, and my computer registered an earthquake at exactly that time. We will both agree on what happened. You know it took a second for the light to travel, so you know it was 1:00:00 for me when the volcano erupted. My readings agree. There is no way you could have gone "back in time" to warn the earth about the volcano, because it takes time to reach the planet. There is no paradox, but if you think thats time traveling, you are free to do so. Right now, im laying on my bed, and time is moving, so i think that im a time traveler, too! Your asking some really good questions, and i am enjoying typing responses to them.
|
|
Re: Light, gravity, and time...
Link |
by S-a-c-h-i-e-l
on 2006-01-09 23:53:32
|
|
So when you say that when a wave a water stops moving, it'll over a short period of time turn into a flat surface of water. That bein' the case, what does light turn into if that wave stops moving? And light does not move instantly, it moves very quickly; so let's say (since I'm too lazy to do all sorts of math) that it takes light 15 seconds to get from Earth to Mars. So I couldn't see the light from the volcano on Earth until 15 seconds have past, so wouldn't that mean that I would be seeing the volcano from 15 seconds ago with your time? In that case, I would be looking into the past, so to speak, correct? So no one knows what effect produces gravity, then? T.T And for the rest of your comments, I don't really understand the answer, but I get it mostly... I'm assuming that you are correct on the things that you answered ^_^; Wait... You say that you enjoy replying to this stuff, but it's nothing new to you and you can answer it right off T.T And I never thought of it that way. Everyone and everything is a time traveler! ^_^ |
|
Re: Light, gravity, and time...
Link |
by
on 2006-01-10 00:47:05 |
|
The energy of a photon can be turned into heat (warming in the heat of the sunlight), or in the case of a solar sail, the energy can be conserved as momentum. Light can also ionize an atom (which is technically another case of momentum) in the case of a solar electric cell. Yes, you are detecting photons which have been traveling through space for 15 seconds. Yes, this is a way to see events that have happened in the absolute past. Gravity is the curving of space-time around massive particles. We know which particles are massive (except for the neutrino, maybe), and how much they curve space-time, as well as how that effects other particles. What we don't know is WHY massive particles bend space. But, be it invisible angels or an invisible field, it doesnt change our predictions, which are the point of doing science. I have taken advanced physics, and I try to avoid shooting my mouth off when it comes to things I dont know anything about. So, I would say you can trust my answers pretty well. Dont take my word for it, though. Check out this thread for some good reading sources.
|
|
Re: Light, gravity, and time...
Link |
by S-a-c-h-i-e-l
on 2006-01-10 01:28:12
|
|
Ah, thanks for those links... I will be reading them tomorrow (or later today, since it's currently 2:28 AM). Err, I'm not sure I get what your first paragraph there meant... Gendou, not shooting off your mouth on something you don't know much about = smart. I know someone/people that do that... Very stupid X_X Thanks again for those links, and I will now be retiring to my bed... well, my computer desk, but it counts as my bed >:-) |
|
Re: Light, gravity, and time...
Link |
by
on 2006-01-10 07:30:17 |
|
You seem to be facinated by the fact that watching something from far away enough to make the light traveling time significant would be, in a matter of thought, looking into, or at, past events. This isn't all that uncommon of a situation though. Imagine you are talking to someone on AIM using a slow dial-up connection and they have a high-speed connection. When they type in a message and press enter, their message will be displayed on their chat window almost instantly. On your computer it may take several seconds to actually show up, so you are seeing your friend talking in the past, so to speak. In your situation on Mars, while you are viewing events 15 seconds after people expierenced them on Earth, it's not like you're looking back through a time warp-hole that lets you see the past. Even if you wanted to, you couldn't view events on Earth in 'real time'. It just so happens by the nature of your situation that your entire perspective of Earth is 'lagging' by 15 seconds, just like a slow internet connection. |
|
Re: Light, gravity, and time...
Link |
by S-a-c-h-i-e-l
on 2006-01-10 12:53:18
|
|
Yeah! It's cool stuff! See, if me and you were instant messenging each other (and it really was INSTANT messaging), you could see something and tell me about before I saw it... It's cool ^_^ It also makes you wonder where the planets really are... You can see stars that are actually planets in the sky at night, but they could very well be out of the sky by now in reality and we just see them as they were a while ago. AND... That makes you think that if someone sent a probe to Saturn, Saturn would appear to go faster while the probe was going toward it because thwe light you are seeing is getting newer and newer ^_^ |
|
Re: Light, gravity, and time...
Link |
by
on 2006-01-10 15:04:45 |
|
Be carefull not to interchange starts and planets, they are not the same thing. Stars emit light, and are made up mostly out of plasma. The light we see from the stars is actually the heat emitted by the nuclear reaction that takes place inside the star. Planets on the other hand are vast solid masses that just reflect the light. Planetes don't "make" their own light. But what you say is true, the stars or planetes we see in the sky at night may not be there anymore, because of the time it takes for the light to reach us. So what we see is indeed how the star/planet looked when the light was emited/reflected from them. Wikipedia Planet Wikipedia Star
[Quiet dogs know when to be silent]
Sheep & Tiojar's Anime Episodes |
|
Re: Light, gravity, and time...
|
|
Getting back to the topic of stopping light...... So I understand the fact that a wave can't be stopped while still existing, but does that mean that an object can't be accelerated to light speed?
Wise Man says: "Take a dog off its leash and it will wander."
|
|
Re: Light, gravity, and time...
Link |
by
on 2006-01-10 16:10:46 (edited 2006-01-10 16:28:37)
|
|
@engineer: i have not the time to explain Einstein's theory of relativity, but therein lies your answer. Simply put, it is meaningless to say you have accelerated an object to the speed of light. The sentence is a contradiction. Edit: i am at work right now... i would rather talk relativity than code, so you are in luck! The first, and ONLY postulate of special relativity states that the laws of physics are the same in any reference frame. A reference frame is a cartesian coordinate system in which an observer lies. If one observer is moving with respect to another, they have different reference frames. If they are at rest with one another, they share a common reference frame. One mathematical ramification of Einstein's theory of relativity is that the mass of an object (defined as its resistance to acceleration) increases with its velocity, asymptotically approaching the speed of light. Therefore, it can quickly be understood that it would take infinite energy to accelerate an object to the speed of ligth. If this does not convince you, consider the effect of near-light-speed velocities on space itself. As an object increases in speed, its length dimension of space is observed to be shorter. Since the length of an object cannot be negative, the we should hope its speed does not exceed the speed of light. There are several other contradictions which arise when you study relativity in school. These are the two that come off the top of my head.
|
|
Re: Light, gravity, and time...
Link |
by
on 2006-01-10 17:03:41 |
|
@Sachiel: And continuing off of Gendou's last thought, while it may be fun to ponder it. You could never pull off any truly 'instant' messaging because (unless you could send the information without sending any mass with it) whatever way we choose to carry the communication, something would be traveling faster than light. In the future, it may be possible to form some sort of tunnel behind the fabric of space-time to transport things through that would allow faster than light travel. Or there may be some method of carring information between points faster than light without having an object with mass carry the signal. For now, I just can't happen though. @engineer: I can't be sure of this, but I think I remember reading about scientists in some lab actually being able to freeze a photon of light in position momentarily. I don't know what good it did them or the world, or if I'm just thinking of something else though. Any clarification here Gendou? |
|
Re: Light, gravity, and time...
Link |
by
on 2006-01-10 17:22:48 (edited 2006-01-10 17:25:29)
|
|
regarding sending a messege instantaniously: it is possible to teleport information instantly. this can be done by exploiting the "spooky action" of subatomic particles. this is also known as Quantum Entanglement. See: http://en.wikipedia.org/wiki/Quantum_entanglement See also:http://en.wikipedia.org/wiki/EPR_paradox regarding the experiment with light: what was achieved in the lab was not "freezing light". you are very likely referring to an experiment where light is sent on a spiral course which measures a few ligth-seconds in length (on the order of some thousands of miles), but which is so tightly compacted (like a slinky) that it only moves a few feet or inches horizontally. This is NOT changing the speed of a moving photon. It is simply allowing a signal of light to have a latency, which im sure has plenty of practical and theoretical application.
|
|
Re: Light, gravity, and time...
Link |
by
on 2006-01-10 19:15:23 |
|
Now that my Greek vocabulary has been effectivly doubled, I stand corrected. I think I have heard some mention of that phenomenon in other times and places as being a way to transmit encrypted information so that you could tell if it had been observed by a third party. I somehow didn't catch how that would work, or maybe that's something different. |
|
Re: Light, gravity, and time...
Link |
by S-a-c-h-i-e-l
on 2006-01-10 19:34:44
|
|
Advanced physics are too complicated T.T But I kinda sorta get what's going on... Don't expect my posts to be too helpful though ^_^; And Sheep, I'm well aware of the difference of planets and stars ^_~ |
|
Re: Light, gravity, and time...
|
|
Sorry Gendou..... I know all about the Theory of Relativity, I just wasn't thinking at the time of my last post, it was a dumb question on my part. According to the equations, at light speed mass and time become undefined, and length becomes zero. There's also another equation with "u" in it I think, but my teacher said we didn't need to learn that one.
Wise Man says: "Take a dog off its leash and it will wander."
|
|
Re: Light, gravity, and time...
|
|
I'm not really sure what produces gravity, but I think it has to do with the hypothetical subatomic particle called a graviton which is far smaller than an atom and exists indepedently from other forms of matter as said by the string theory (I'm not too sure about that). You guys already explained everything that was needed about space and time so, about light and gravity. I'm going to go with Einstein's theory of general relativity on this one; gravitational effects are caused by masses or concentrations of energy causing a distortion in the shape of four-dimensional space-time (space-time continuum). That is, gravity might be a purely geometrical consequence of the effect of mass on space-time. It's kind of like if you drop a bowling ball on a trampoline, it will cause a large dent. If a lighter golf ball comes close to the bowling ball, it will fall into the dent thus becoming captured in an orbit around the bowling ball. If so, because light also exists as a particle, it will curve around a mass because of the warping of space-time caused by the mass
You need a reason to be sad. You don't need a reason to be happy. The secret to happiness is to face the fact that the world is horrible.
|
|
Re: Light, gravity, and time...
|
| I thought that the mass of an object creates gravity. Or am i wrong? I dunno not too sure maybe ill go check my text book. |
|
Re: Light, gravity, and time...
Link |
by
on 2006-01-29 17:46:44 |
|
black hole? are they big or small? why do we call hem "black" instead of something like ultramagneticgravitationalsomthing... and "what if" we get sucked into one of them black holes? what results could happen there? |
Go to page: 0,
1 Displaying 1 to 20 of 27 Entries.