Sign up with Google- Is it known why the speed of light is constant, why photons always travel at the speed c exactly?
- Is it understood why c = 299,792,458 m/s? What is special about this number, other than the fact that it represents the speed of light?
- Does gravity also propagate at the speed of light?
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Some questions about the speed of light
- Thread starter Humberto
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isie
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Not sure what you mean by whats special about the speed? thats the speed of light nothing in space can go faster then that.
an on your gravity questuion, if you mean draw an object to it at the speed of light, AFAIK you would need an object of almost infinate mass to do that.
@Humberto - what do you actually mean with your gravity question? Do you mean that, when one object's weight changes, how long before the gravity pull is changed for the second object? I.e. how long it takes for the second object to realize that the first object's weight has changed?
Ryanbighead
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To answer your question in one liners:
* The speed is constant as photons mass is constant, at 0. I assume this is the fastest an object with no mass can travel, as there are no variables.
* The number itself has no strange meaning, it is just a number given whilst using the metric system of measurement. If it were done in feet, miles, kilos, UI's per second it will be different. (I think you get what I mean here)
* I am led to believe that Gravity propagates faster than the speed of light...
Some further thought...
I don’t know how this is going to come out but I will try.
On the speed of light:
As far as I am aware, photons have no mass (as we understand). Thus, objects with mass can only travel up to 'just under the speed of light'. As an object accelerates towards the speed of light, its mass increases exponentially. The amount of energy required to accelerate said object, in small increments, increases faster than the objects mass or speed.
Energy required to move object > Mass of object > Speed of object
In my mind, maintaining speed would not require excessive amounts of energy, if any, in a perfect vacuum without gravity or obstacles but as we know, space is neither of those things. Even though the gravitational pull of distant stars / galaxies etc. are minute and there are various atoms which are measured in parts per **unfathomable number**, these would play havoc in attaining such speeds.
I am not going to touch on what happens with time at these speeds as I feel it is not relevant. It could be... but my monkey brain is a monkey brain.
On the speed of gravity:
Gravity on the other hand is said to propagate faster than light. To be precise, it happens instantaneously. It is said to be unconditionally infinite. Celestial mechanics calculations are based on this assumption. I however, as did sir Isaac Newton, think this is equal to Black Magic. This theory proposes that a finite body (say a planet) has infinite energy. I haven't done much reading into this but I think I will now... my thought processed could be incredibly outdated.
Please don't quote me on any of the above. Physics is a hobby... I don't even have a matric certificate.
* The speed is constant as photons mass is constant, at 0. I assume this is the fastest an object with no mass can travel, as there are no variables.
* The number itself has no strange meaning, it is just a number given whilst using the metric system of measurement. If it were done in feet, miles, kilos, UI's per second it will be different. (I think you get what I mean here)
* I am led to believe that Gravity propagates faster than the speed of light...
Some further thought...
I don’t know how this is going to come out but I will try.
On the speed of light:
As far as I am aware, photons have no mass (as we understand). Thus, objects with mass can only travel up to 'just under the speed of light'. As an object accelerates towards the speed of light, its mass increases exponentially. The amount of energy required to accelerate said object, in small increments, increases faster than the objects mass or speed.
Energy required to move object > Mass of object > Speed of object
In my mind, maintaining speed would not require excessive amounts of energy, if any, in a perfect vacuum without gravity or obstacles but as we know, space is neither of those things. Even though the gravitational pull of distant stars / galaxies etc. are minute and there are various atoms which are measured in parts per **unfathomable number**, these would play havoc in attaining such speeds.
I am not going to touch on what happens with time at these speeds as I feel it is not relevant. It could be... but my monkey brain is a monkey brain.
On the speed of gravity:
Gravity on the other hand is said to propagate faster than light. To be precise, it happens instantaneously. It is said to be unconditionally infinite. Celestial mechanics calculations are based on this assumption. I however, as did sir Isaac Newton, think this is equal to Black Magic. This theory proposes that a finite body (say a planet) has infinite energy. I haven't done much reading into this but I think I will now... my thought processed could be incredibly outdated.
Please don't quote me on any of the above. Physics is a hobby... I don't even have a matric certificate.
Last edited:
Gadget Man
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Hi,
That's the theoretical speed of light in a vacuum ... it changes based on the medium through which it travels, e.g. thick air will see the light travel slower etc. So, it is not really constant, but variable base don the medium of travel.
I have no idea how it is measured, but I am sure there is a clever way to do it. Much like when we measured the weight of an electron (a single electron) in the lab at varsity.
Gravity does not propagate at speed of light. Imagine a sky diver coming to the earth at the speed of light?
That's the theoretical speed of light in a vacuum ... it changes based on the medium through which it travels, e.g. thick air will see the light travel slower etc. So, it is not really constant, but variable base don the medium of travel.
I have no idea how it is measured, but I am sure there is a clever way to do it. Much like when we measured the weight of an electron (a single electron) in the lab at varsity.
Gravity does not propagate at speed of light. Imagine a sky diver coming to the earth at the speed of light?
Sinbad
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That's not propagation of gravity. That's the effect of gravity on someone.
Isn't gravity propagated by gravitons? Surely they aren't a FTL particle?
Ryanbighead
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If gravity did not propagate FTL then everything would be FUBAR.
Imagine the effect of the suns gravitational pull if it took the ±8 minutes that light takes to get here...
Gravity is conclusive proof that magic exists. I await my increadibly late letter to hogwarts.
Last edited:
Sinbad
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Why? The pull is constant, so how long it took to get here wouldn't make a difference....
isie
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AFAIK nothing in space time (including gravity) can travel FTL, though space itself can travel FTL - well at least expansion of space" between galaxies observed by those galaxies furthest away from us they are moving away from us at speeds greater then light
Mike Hoxbig
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Think of it as a piece of string wrapped around a ball. It's not a function of time.
Ryanbighead
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"................anyone with a computer and orbit computation or numerical integration software can verify the consequences of introducing a delay into gravitational interactions. The effect on computed orbits is usually disastrous because conservation of angular momentum is destroyed. Expressed less technically by Sir Arthur Eddington, this means: “If the Sun attracts Jupiter towards its present position S, and Jupiter attracts the Sun towards its present position J, the two forces are in the same line and balance. But if the Sun attracts Jupiter toward its previous position S’, and Jupiter attracts the Sun towards its previous position J’, when the force of attraction started out to cross the gulf, then the two forces give a couple. This couple will tend to increase the angular momentum of the system, and, acting cumulatively, will soon cause an appreciable change of period, disagreeing with observations if the speed is at all comparable with that of light.” (Eddington, 1920, p. 94)"
Source http://www.metaresearch.org/cosmology/speed_of_gravity.asp
Source http://www.metaresearch.org/cosmology/speed_of_gravity.asp
Mike Hoxbig
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He's saying that gravity travels faster than light :erm:
Sinbad
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Interesting. This whole relativity thing messes with my mind.
How big would that couple be, in effect?
bin3
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To the OP: and with all due respect, but this is starting to feel more and more like answer Physics 101? Especially with regards to some previous threads.
If so, maybe consider doing your homework yourself, or at least having some answers ready to debate? If I'm totally out of line, please ignore this, otherwise ...
If so, maybe consider doing your homework yourself, or at least having some answers ready to debate? If I'm totally out of line, please ignore this, otherwise ...
Scooby_Doo
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I think we need to take out the idea that gravity "travels", you assuming that gravity "sends" out "things" FTL to affect other objects. This idea is flawed.
Sinbad
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Gravity is still a cause and effect thing though. Something has to "carry" the "message". Otherwise you have the possibility of an effect being felt before the cause can be detected?
Unless Gravity = Monarchy?
So if gravity is instantaneous and nothing can travel FTL, then I would think that the "Higgs boson"(Gravity) is not a particle but an oscillation(of some sort in multiple dimensions) and that everything shares this interaction IE. the bigger the mass the more Gravity it has
...(eks afrikaans)
...(eks afrikaans
)- If the yet-to-be-discovered graviton is the messenger particle of gravity, then gravity can but propagate at the speed of light.
- If the effect of gravity were instantaneous, could this property be exploited to allow faster-than-light communication? Movements of objects far away would be known before light signals of those objects reached the observer.
- Imagine the sun were to suddenly disappear. If gravity propagates at the speed of light, earth would continue along its orbit for approximately eight minutes before flying off into space.
- If the speed of light is not invariable but medium-specific, could gas, dust, or hypothetical dark matter effect its speed in space?
- How is the distance of far-away objects in space measured, and what would be the role of the above point on this?