# Can any object approach another at greater than light speed?

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'Closing speed' is not the velocity of any single object in the scenario, therefore nothing is violated, but is actually an artifact* of combining the measurements of two objects.

* Artifact - something observed in a scientific investigation or experiment that is not naturally present but occurs as a result of the preparative or investigative procedure.

So the in guy in the middle, hypothetically, if he looked at one fast approaching mountain, from his left side, would see it coming towards him at 90% light, if he look from the perceptive of his right side, he would also see a mountain approaching him at 90% light speed speed, and the gap between them closing/shrinking at 180% light speed. If he could do the impossible and observe what happens to his body, when both mountain crash into it. Would his died body realize that he had been impacted it with a force of a huge object hitting him at 180% c (Light Speed)?

A force of 180% c would destroy the universe, if my analogy is correct? Then exactly what would happen to cars of equal mass, crashing head on into each other could be extrapolated down to proton level?

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So the in guy in the middle, hypothetically, if he looked at one fast approaching mountain, from his left side, would see it coming towards him at 90% light, if he look from the perceptive of his right side, he would also see a mountain approaching him at 90% light speed speed, and the gap between them closing/shrinking at 180% light speed. If he could do the impossible and observe what happens to his body, when both mountain crash into it. Would his died body realize that he had been impacted it with a force of a huge object hitting him at 180% c (Light Speed)?

A force of 180% c would destroy the universe, if my analogy is correct? Then exactly what would happen to cars of equal mass, crashing head on into each other could be extrapolated down to proton level?

He gets hit by each object at 90% of the speed of light. Although it happens simultaneously, each collision with him is a separate event. Don' t add them up.

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He gets hit by each object at 90% of the speed of light. Although it happens simultaneously, each collision with him is a separate event. Don' t add them up.

If he were in the "exact center" and both were approaching him at 90% light speed "to reach him at the exact same moment in time", then logic tells me he has endured at impact by two huge objects at 180% light speed, which according to Einstein is an impossibility?

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If he were in the "exact center" and both were approaching him at 90% light speed "to reach him at the exact same moment in time", then logic tells me he has endured at impact by two huge objects at 180% light speed, which according to Einstein is an impossibility?

If you were standing in the path between two cars going 50 mph you are being hit at 50mph by each of them; not 100mph. The cars will experience a collision of 100mph but not you. Your speed, relative to each car, and vice versa, is 50 mph. It's the same thing in your scenario but you have to make relativistic corrections,

Edited by StringJunky
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If you were standing in the path between two cars going 50 mph you are being hit at 50mph by each of them; not 100mph. The cars will experience a collision of 100mph but not you. Your speed, relative to each car, and vice versa, is 50 mph. It's the same thing in your scenario but you have to make relativistic corrections,

That seems to be splitting hairs, your body will experience a force of being hit by a 100mph object, because you are in the path of both objects who will both collide with you, at the exact same moment in time, from exactly opposite directions.

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The key point is that not you nor the cars will measure any other object in this mix as traveling faster than the speed of light. This is all the special relativity says in the respect.

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A force of 180% c would destroy the universe, if my analogy is correct?

Speed is not force. And force is not energy. I doubt such a collision would release enough energy to destroy the universe. The planet, maybe.

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So the in guy in the middle, hypothetically, if he looked at one fast approaching mountain, from his left side, would see it coming towards him at 90% light, if he look from the perceptive of his right side, he would also see a mountain approaching him at 90% light speed speed, and the gap between them closing/shrinking at 180% light speed. If he could do the impossible and observe what happens to his body, when both mountain crash into it. Would his died body realize that he had been impacted it with a force of a huge object hitting him at 180% c (Light Speed)?

Other than that there is no equation that works for 1.8c. The impact force would be twice as big as a single mountain.

It occurs to me now that the question could either be about the momentum, which is what I have assume, or the relativistic correction formula. As I said, there is no was to calculate anything for 1.8c. The question as you phrased it is actually nonsensical.

The momentum of a mountain is $\gamma mv$

The momentum of 2 mountains is twice that.

A force of 180% c would destroy the universe, if my analogy is correct? Then exactly what would happen to cars of equal mass, crashing head on into each other could be extrapolated down to proton level?

That's what they do. They apply conservation of energy and momentum.

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Other than that there is no equation that works for 1.8c. The impact force would be twice as big as a single mountain.

It occurs to me now that the question could either be about the momentum, which is what I have assume, or the relativistic correction formula. As I said, there is no was to calculate anything for 1.8c. The question as you phrased it is actually nonsensical.

The momentum of a mountain is $\gamma mv$

The momentum of 2 mountains is twice that.

That's what they do. They apply conservation of energy and momentum.

You did not answer my question, but thanks for the effort it seems to me it is a mathematical equation that does not exist as a reality in the macro world we exist in?

Alan

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A photon is released towards you one light minute to your left. Another photon is released towards you simultaneously one light minute to your right.

It will take each photon one minute to reach you as they are each traveling at c.

The starting distance between the two photons is 2 light minutes.

Speed = distance / time

Two light minutes divided by 1 minute to close the gap between the photons equals a closing speed of 2c.

It cannot be less than 2c, otherwise it would take each photon longer than one minute to travel one light minute.

Same principle applies to everything else in this scenario.

If a mountain is coming at you at 90% of the speed of light from a distance of 90% of a light minute, it will take one minute to reach you. That is true no matter what direction the mountain is traveling from.

If you have two mountains traveling at you from opposite directions at 90% of the speed of light, each 90% of a light minute away from you, it will take each of them one minute to reach you, by definition of how fast they are going.

The starting distance between the two, in your frame, will be 1.8 light minutes or 180% of a light minute.

The distance of 1.8 light minutes is closed in one minute, so the closing speed is 1.8c.

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So the in guy in the middle, hypothetically, if he looked at one fast approaching mountain, from his left side, would see it coming towards him at 90% light, if he look from the perceptive of his right side, he would also see a mountain approaching him at 90% light speed speed, and the gap between them closing/shrinking at 180% light speed. If he could do the impossible and observe what happens to his body, when both mountain crash into it. Would his died body realize that he had been impacted it with a force of a huge object hitting him at 180% c (Light Speed)?

A force of 180% c would destroy the universe, if my analogy is correct? Then exactly what would happen to cars of equal mass, crashing head on into each other could be extrapolated down to proton level?

"A force of 180% c" is a nonsensical phrase, as the the force of any speed. The force experienced by two colliding objects depends on how the objects react to the impact. For example, if I fire a bullet at a block of wood, the force of impact depends on the wood. The more the wood resists penetration by the bullet the greater the force of impact. A hard dense wood resists penetration more than a soft wood, and so the bullet will travel further into the softer wood. The bullet has the same kinetic energy in both situations, and energy is force x distance.

So if we divide the distance the bullet travels into the wood, we get the force exerted to stop the bullet. And since the bullet traveled further in the softer wood, there was less force over a longer distance.

So how do we apply this to the colliding objects? When two objects collide, each one is going to compress a bit in the collision. The amount of force felt by each will depend on how much it compresses before the two come to a rest with respect to each other.

Imagine that you have two steel balls moving towards each other, each moving at 50 m/s. Between them is in-movable wall made of some in-compressible substance. Each ball hits it side of the wall at the same time as the other. The existence of the other ball has no effect on the force felt by either ball in hitting the wall. Each ball hits the wall, compresses at bit under the impact and this compression creates a force that brings the ball to a stop. The magnitude of force will depend on how much the ball compresses. The ball then decompresses, exerting causing the ball to rebound way at the same speed as it hit the wall.

Now imagine that the we make the wall thinner and thinner and thinner until we remove it completely. The two balls hit each other and rebound heading in opposite directions at the same speed they were moving before collision. This is exactly what happened when the wall was between them. Each ball experiences exactly the same forces it felt when it hit the wall. The force of impact between the two balls is the same as the force of impact between either a ball and the wall.

While at first blush, it might seem reasonable to assume that the force of impact would be twice as high for the colliding balls than for a single ball hitting the wall, it turns out not to be the case.

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"A force of 180% c" is a nonsensical phrase, as the the force of any speed. The force experienced by two colliding objects depends on how the objects react to the impact. For example, if I fire a bullet at a block of wood, the force of impact depends on the wood. The more the wood resists penetration by the bullet the greater the force of impact. A hard dense wood resists penetration more than a soft wood, and so the bullet will travel further into the softer wood. The bullet has the same kinetic energy in both situations, and energy is force x distance.

So if we divide the distance the bullet travels into the wood, we get the force exerted to stop the bullet. And since the bullet traveled further in the softer wood, there was less force over a longer distance.

So how do we apply this to the colliding objects? When two objects collide, each one is going to compress a bit in the collision. The amount of force felt by each will depend on how much it compresses before the two come to a rest with respect to each other.

Imagine that you have two steel balls moving towards each other, each moving at 50 m/s. Between them is in-movable wall made of some in-compressible substance. Each ball hits it side of the wall at the same time as the other. The existence of the other ball has no effect on the force felt by either ball in hitting the wall. Each ball hits the wall, compresses at bit under the impact and this compression creates a force that brings the ball to a stop. The magnitude of force will depend on how much the ball compresses. The ball then decompresses, exerting causing the ball to rebound way at the same speed as it hit the wall.

Now imagine that the we make the wall thinner and thinner and thinner until we remove it completely. The two balls hit each other and rebound heading in opposite directions at the same speed they were moving before collision. This is exactly what happened when the wall was between them. Each ball experiences exactly the same forces it felt when it hit the wall. The force of impact between the two balls is the same as the force of impact between either a ball and the wall.

While at first blush, it might seem reasonable to assume that the force of impact would be twice as high for the colliding balls than for a single ball hitting the wall, it turns out not to be the case.

Indeed - look at a newton's cradle if both end balls are dropped from a similar position at the same time

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"A force of 180% c" is a nonsensical phrase, as the the force of any speed. The force experienced by two colliding objects depends on how the objects react to the impact. For example, if I fire a bullet at a block of wood, the force of impact depends on the wood. The more the wood resists penetration by the bullet the greater the force of impact. A hard dense wood resists penetration more than a soft wood, and so the bullet will travel further into the softer wood. The bullet has the same kinetic energy in both situations, and energy is force x distance.

So if we divide the distance the bullet travels into the wood, we get the force exerted to stop the bullet. And since the bullet traveled further in the softer wood, there was less force over a longer distance.

So how do we apply this to the colliding objects? When two objects collide, each one is going to compress a bit in the collision. The amount of force felt by each will depend on how much it compresses before the two come to a rest with respect to each other.

Imagine that you have two steel balls moving towards each other, each moving at 50 m/s. Between them is in-movable wall made of some in-compressible substance. Each ball hits it side of the wall at the same time as the other. The existence of the other ball has no effect on the force felt by either ball in hitting the wall. Each ball hits the wall, compresses at bit under the impact and this compression creates a force that brings the ball to a stop. The magnitude of force will depend on how much the ball compresses. The ball then decompresses, exerting causing the ball to rebound way at the same speed as it hit the wall.

Now imagine that the we make the wall thinner and thinner and thinner until we remove it completely. The two balls hit each other and rebound heading in opposite directions at the same speed they were moving before collision. This is exactly what happened when the wall was between them. Each ball experiences exactly the same forces it felt when it hit the wall. The force of impact between the two balls is the same as the force of impact between either a ball and the wall.

While at first blush, it might seem reasonable to assume that the force of impact would be twice as high for the colliding balls than for a single ball hitting the wall, it turns out not to be the case.

Although I used mountains as an example we are in reality talking protons, and my watery body would offer no/zero resistance between the two colliding mountains approaching at 90% c.

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Not strictly true. If the mountain is colliding with you at 0.9c, that also means you are colliding with the mountain at 0.9c, and at that speed, both you and the mountain would be completely destroyed by the collision.

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Not strictly true. If the mountain is colliding with you at 0.9c, that also means you are colliding with the mountain at 0.9c, and at that speed, both you and the mountain would be completely destroyed by the collision.

You are right at 90% c my body would be as hard to penetrate as a massive wall!

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You are right at 90% c my body would be as hard to penetrate as a massive wall!

But you'll still end up as pancaked tomato sauce, for a fraction of second

Edited by StringJunky
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Or turned to plasma: https://what-if.xkcd.com/1/

"What would happen if you tried to hit a baseball pitched at 90% the speed of light?"

Let's just say: it doesn't end well.

Edited by Strange
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Or turned to plasma: https://what-if.xkcd.com/1/

LOL

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Or turned to plasma: https://what-if.xkcd.com/1/

"What would happen if you tried to hit a baseball pitched at 90% the speed of light?"

Let's just say: it doesn't end well.

You are wrong you will be flooded by base ball leagues to join their teams at a huge salary not seen in any sport before!!

Alan

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It is my understanding that from your perspective they are approaching each other at faster than c. Since noTHING is moving faster than c, no laws have been been violated.

I usually do not point mistakes out but, just to clear my doubts, doesn't special relativity state than nothings from any perspective can be observed to go faster than the speed of light. Even if you are moving towards a light source, the light being emitted should be measured the same speed as if you were moving away from the light source. Is this right or wrong?

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I usually do not point mistakes out but, just to clear my doubts, doesn't special relativity state than nothings from any perspective can be observed to go faster than the speed of light. Even if you are moving towards a light source, the light being emitted should be measured the same speed as if you were moving away from the light source. Is this right or wrong?

Right they will both show a redshift way from your perspective.

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I usually do not point mistakes out but, just to clear my doubts, doesn't special relativity state than nothings from any perspective can be observed to go faster than the speed of light. Even if you are moving towards a light source, the light being emitted should be measured the same speed as if you were moving away from the light source. Is this right or wrong?

Can you be more specific on what mistake you are talking about?

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Here's a simple way to look at it...

Faster than c motion is allowed as long as there cannot be any information transfer.

In the case of the two mountains separating or closing at 0.9c, any information is conveyed by them at only 0.9c ( not 1.8c ).

Even though the 'apparent' separating or closing speed is greater than c.

This same effect is observed in the motion of a shadow or an image on a surface. The image ( illuminated spot ) or shadowed spot, can be made to move across the surface superluminally.

But no actual information is being transferred at a rate faster than c

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Here's a simple way to look at it...

Faster than c motion is allowed as long as there cannot be any information transfer.

In the case of the two mountains separating or closing at 0.9c, any information is conveyed by them at only 0.9c ( not 1.8c ).

Even though the 'apparent' separating or closing speed is greater than c.

This same effect is observed in the motion of a shadow or an image on a surface. The image ( illuminated spot ) or shadowed spot, can be made to move across the surface superluminally.

But no actual information is being transferred at a rate faster than c

Thank you, then the ''Shrinking'space' does exist mathematically?

Edited by Alan McDougall
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It seems that this question is not so easy to answer but thanks!

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