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visinedrops

Does outer space have drag?

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Looking at space and time, relativity, and matter, I have prompted a question in my head.  If time is reactive to something, it implies that it travels.  Photons have mass when they are traveling and they travel at the speed of light.  

It takes around 8 seconds for light to travel from the sun to Earth.  The same concept can be procured from terminal velocity of a falling object.  It reaches a set speed based on its mass to resistance of the matter it is traveling through.  So, the thought in my head is that space itself has resistance.  Since light is composed of photons, and they have mass, then the time it takes them to travel a distance implies that there is a certain amount of drag to space itself.  Otherwise, when a photon is created on the sun, it would instantly appear on the earth, and therefore negate the effect of time.

So, back to my question, does space have drag?

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4 minutes ago, visinedrops said:

Looking at space and time, relativity, and matter, I have prompted a question in my head.  If time is reactive to something, it implies that it travels.  Photons have mass when they are traveling and they travel at the speed of light.  

It takes around 8 seconds for light to travel from the sun to Earth.  The same concept can be procured from terminal velocity of a falling object.  It reaches a set speed based on its mass to resistance of the matter it is traveling through.  So, the thought in my head is that space itself has resistance.  Since light is composed of photons, and they have mass, then the time it takes them to travel a distance implies that there is a certain amount of drag to space itself.  Otherwise, when a photon is created on the sun, it would instantly appear on the earth, and therefore negate the effect of time.

So, back to my question, does space have drag?

Analogies are sometimes interesting, but very limited. The speed of photons is not really a limiting speed. Photons have a constant speed no matter how you look at them. Your analogy would be more appropriate for massive particles under constant force (hyperbolic motion). But the problem is: What kind drag motion represents photons then? What's more similar to a drag due to vacuum is the resistance due to the vacuum scalar field at inflationary times previous to re-heating (inflaton drag force: google for "inflation as viscous force" or similar). In that case the analogy can be taken to be closer to what you suggest AFAIK.

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14 minutes ago, visinedrops said:

If time is reactive to something, it implies that it travels. 

Not sure what you mean by time being reactive. And I don't understand why that would mean it travels. I don't even understand what it would mean for time to "travel". 🤷‍♂️

14 minutes ago, visinedrops said:

Photons have mass when they are traveling and they travel at the speed of light.

No. Photons are massless.

14 minutes ago, visinedrops said:

It takes around 8 seconds for light to travel from the sun to Earth.  The same concept can be procured from terminal velocity of a falling object.  It reaches a set speed based on its mass to resistance of the matter it is traveling through. 

It has nothing to do with terminal velocity. Light always travels at the same speed.

Quote

Since light is composed of photons, and they have mass, then the time it takes them to travel a distance implies that there is a certain amount of drag to space itself.  

No. Photons do not have mass. And even if they did, it would not imply that space has drag.

Nothing with mass can travel at the speed of light.

15 minutes ago, visinedrops said:

Otherwise, when a photon is created on the sun, it would instantly appear on the earth, and therefore negate the effect of time.

No. Photons always travel at the speed of light. Which is why it takes them 8 minutes to get to Earth from the Sun.

14 minutes ago, visinedrops said:

So, back to my question, does space have drag?

No.

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7 minutes ago, Strange said:

Not sure what you mean by time being reactive. And I don't understand why that would mean it travels. I don't even understand what it would mean for time to "travel". 🤷‍♂️

I concur. I should have read this more carefully. Time doesn't react to anything, or travel.

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A few points in addition to explanations above:

1 hour ago, visinedrops said:

Photons have mass when they are traveling and they travel at the speed of light.  

A photon is massless. Maybe you mean momentum? A photon carries momentum.

"When they travel" is maybe not the best way to label photons, a photon always move and always at the speed of light in vacuum. Photons do not "not travel", but photons can be absorbed. And the mass of a system that absorbs a photon is increased by an amount corresponding to the energy of the photon (energy measured in the rest frame of an absorbing system) 

A rough sketch of a sentence, including movement, mass and speed could be* 

Photons carry momentum, they always move at the speed of light in vacuum and the energy they carry contribute to the mass of an absorbing system.

 

*) If one long sentence is preferred

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Space does have drag, because there will be some small amount of matter in it. Drag implies an object would continue to slow down. That would apply to objects with mass, but photons are massless; even in a uniform medium they will maintain a constant speed. In a vacuum, it’s c.

 

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I suppose I completely garbled my thought while trying to put it into words and confused everyone with a greater ability to explain things than I.  My thought encompasses the idea that light travels at a set speed.  Constantly.  Since there is a mathematical calculation to determine how long it takes for a photon to travel from one place to another, it would stand to reason that whatever it is travelling through (space) is causing resistance in its momentum.  

Since nothing with mass can travel light speed, it would also imply that, although space is a vacuum, it restricts the movement of an object through it.  Hence why I'm curious if space has drag.

I don't know if that cleared it up any, or just added mud.

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1 hour ago, visinedrops said:

Since there is a mathematical calculation to determine how long it takes for a photon to travel from one place to another, it would stand to reason that whatever it is travelling through (space) is causing resistance in its momentum.  

Are you saying that it would stand to reason there is resistance, because without resistance  photon travel between two points would be instantaneous? If that is not what you are suggesting, can you please explain why being able to calculate how long it takes to get from point A to point B given a constant speed implies resistance?

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It would be more accurate to think of the drag being caused by the particles that reside in space. 

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4 hours ago, visinedrops said:

I suppose I completely garbled my thought while trying to put it into words and confused everyone with a greater ability to explain things than I.  My thought encompasses the idea that light travels at a set speed.  Constantly.  Since there is a mathematical calculation to determine how long it takes for a photon to travel from one place to another, it would stand to reason that whatever it is travelling through (space) is causing resistance in its momentum.

You mentioned terminal velocity earlier, so you seem to be thinking that it requires drag to stop things just getting faster and faster until they are travelling infinitely fast and take zero time to get from A to B.

This is not consistent with Newton's laws of motion:

1. A body at rest remains at rest or, if it is in motion it moves with uniform velocity, unless acted on by a force.

2. A moving object will only change speed (or direction) if there is a force acting on it (F = ma)

https://en.wikipedia.org/wiki/Newton's_laws_of_motion

So the concept of terminal velocity only applies to things falling through the air (or similar situations) where there is a constant force of gravity acting on it.

There is no force acting on photons and so they continue to move at the same speed all the time.

 

Also, the speed of light is not just constant, but it is invariant. It is the same for all observers, regardless of their relative speed.

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44 minutes ago, Strange said:

Also, the speed of light is not just constant, but it is invariant. It is the same for all observers, regardless of their relative speed.

And this is why simple drag won't do the job. +1

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7 hours ago, visinedrops said:

I suppose I completely garbled my thought while trying to put it into words and confused everyone with a greater ability to explain things than I.  My thought encompasses the idea that light travels at a set speed.  Constantly.  Since there is a mathematical calculation to determine how long it takes for a photon to travel from one place to another, it would stand to reason that whatever it is travelling through (space) is causing resistance in its momentum.  

Since nothing with mass can travel light speed, it would also imply that, although space is a vacuum, it restricts the movement of an object through it.  Hence why I'm curious if space has drag.

I don't know if that cleared it up any, or just added mud.

Drag is a force, which means an acceleration. If freely-traveling photons experienced drag, they would have to slow down. They don’t.

Another option is to have some kind of thrust to counter the drag. That would mean a loss of energy (work is being done), which doesn’t happen. No drag.

 

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2 hours ago, swansont said:

Drag is a force, which means an acceleration. If freely-traveling photons experienced drag, they would have to slow down. They don’t.

Another option is to have some kind of thrust to counter the drag. That would mean a loss of energy (work is being done), which doesn’t happen. No drag.

 

That clinches the case. +1

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Thank you for all the replies.  I need to take a class (or series of classes) in whatever science it is I'm trying to figure out.  I had an idea of using light as a propellant for space vehicles where individual light-emitting devices would turn on and off in sequence along the outer hull of a cylinder and the ability to be aimed in such a way to create omni-directional thrust.  But, since space causes no drag on photons, then they would not be a viable source of propulsion.  

Again, thank you.  

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21 minutes ago, visinedrops said:

Thank you for all the replies.  I need to take a class (or series of classes) in whatever science it is I'm trying to figure out.  I had an idea of using light as a propellant for space vehicles where individual light-emitting devices would turn on and off in sequence along the outer hull of a cylinder and the ability to be aimed in such a way to create omni-directional thrust.  But, since space causes no drag on photons, then they would not be a viable source of propulsion.  

Again, thank you.  

Light has momentum and would produce thrust. The reason it’s not viable is that the photon momentum is E/c, so the thrust produced is P/c (P is power)

So you need 300 MW to produce 1 N of thrust. The only real advantage it has is that there is no reaction mass needed. 

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Posted (edited)
18 hours ago, Mordred said:

It would be more accurate to think of the drag being caused by the particles that reside in space. 

In particular (pardon the pun but not bolding for that reason), I would say any body experiencing CMBR anisotropy would experience drag forces (Without looking it up I'm guessing to the square of the speed wrt to CMBR isotropy but please correct me if I'm off the mark)

Deep space, what constitutes greater drag, CMBR photons or other particles assuming average (deep space) distribution?

20 minutes ago, swansont said:

Light has momentum and would produce thrust. The reason it’s not viable is that the photon momentum is E/c, so the thrust produced is P/c (P is power)

So you need 300 MW to produce 1 N of thrust. The only real advantage it has is that there is no reaction mass needed

Except you lose mass emitting the light (conservation of momentum and all)

Edited by J.C.MacSwell

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8 hours ago, visinedrops said:

Thank you for all the replies.  I need to take a class (or series of classes) in whatever science it is I'm trying to figure out.  I had an idea of using light as a propellant for space vehicles where individual light-emitting devices would turn on and off in sequence along the outer hull of a cylinder and the ability to be aimed in such a way to create omni-directional thrust.  But, since space causes no drag on photons, then they would not be a viable source of propulsion.  

Again, thank you.  

As noted, this works in principle (just isn’t very effective in practice - although light sails may be).

But I am curious why you think it would require space to have drag for it to work? Are you thinking that the light would need to push against something? But that is not how propulsion works - otherwise rockets would not work in space! It is enough that the light pushes against the spacecraft (as it leaves).

8 hours ago, visinedrops said:

I need to take a class (or series of classes) in whatever science it is I'm trying to figure out. 

Physics 🙂

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10 hours ago, J.C.MacSwell said:

 Except you lose mass emitting the light (conservation of momentum and all)

As long as you can generate the power, you will have thrust. Reaction mass is not something extra that has to be loaded.

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2 hours ago, swansont said:

As long as you can generate the power, you will have thrust. Reaction mass is not something extra that has to be loaded.

Granted.

 

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