Faster than light approaches and impact?

[GoldenKingGaze]

Considering that by chance perhaps with a swing around different galaxies, two free planets are moving towards each other at 30% and 80% light speed, the total is more than 100% and matter cannot naturally exceed light speed. What would happen around impact? In time and energy, would one planet turn into light?

 

[Neogaia777]

Considering that by chance perhaps with a swing around different galaxies, two free planets are moving towards each other at 30% and 80% light speed, the total is more than 100% and matter cannot naturally exceed light speed. What would happen around impact? In time and energy, would one planet turn into light?

I don't know that that situation or circumstance is possible in our time and space, but I'll wait to see what those who probably know a lot more about it than me have to say?

God Bless.

 

[essentialsaltes]

Considering that by chance perhaps with a swing around different galaxies, two free planets are moving towards each other at 30% and 80% light speed, the total is more than 100% and matter cannot naturally exceed light speed. What would happen around impact? In time and energy, would one planet turn into light?

At relativistic speeds, speed doesn't 'add' normally.

In the scenario, presumably some observer sees one planet moving at 30% of c, and the other at 80% of c in the opposite direction.

But if you are an (unfortunate) observer on one of the two planets, you would see the other moving at:

88.71% the speed of light towards you.

It would be a heckuva collision, but nothing particularly strange would happen.

 

[Neogaia777]

Considering that by chance perhaps with a swing around different galaxies, two free planets are moving towards each other at 30% and 80% light speed, the total is more than 100% and matter cannot naturally exceed light speed. What would happen around impact? In time and energy, would one planet turn into light?

It takes galaxies, with stars and planets in them, to be 46.5 billion light years away, in order to appear to be moving out away from us as the center at 1x the speed of light, so I doubt that there is any situation in any individual galaxy where individual stars, or planets, or star systems, could each individually be moving toward each other at speeds relatively close to the speed of light, or even near the speed of light, etc. Or with individual galaxies either, I don't think individual galaxies could be on a collision course toward each other at speeds close to the speed of light. They actually move quite slowly for both theirs, and the universes immense size, etc. Not a whole lot in the universe on the macro scales moves, or is in motion, at speeds close to the speed of light, etc, or even half of the speed of light, etc.

But I could be wrong about that or those though maybe? Like I said, I'll wait for others to offer more, etc.

God Bless.

 

[Astrophile]

Considering that by chance perhaps with a swing around different galaxies, two free planets are moving towards each other at 30% and 80% light speed, the total is more than 100% and matter cannot naturally exceed light speed. What would happen around impact? In time and energy, would one planet turn into light?

It wouldn't happen. The orbital speeds of stars and rogue planets around the centres of galaxies are hundreds of km/second, not >10% of the speed of light.

 

[GoldenKingGaze]

From ChatGPT:
In space, when two objects approach each other at high velocities, the relative speed at which they approach is not simply the sum of their individual speeds. Instead, we need to use the principles of special relativity to calculate the relative velocity.
When dealing with velocities that are significant fractions of the speed of light, the formula to calculate the relative velocity vrelvrel of one object with respect to another is given by:
vrel=v1+v21+v1v2c2vrel=1+c2v1v2v1+v2
where v1v1 and v2v2 are the velocities of the two objects, and cc is the speed of light.
Given:

• Object A's speed v1=0.80cv1=0.80c
• Object B's speed v2=0.30cv2=0.30c

Plugging these values into the formula:
vrel=0.80c+0.30c1+(0.80c)(0.30c)c2vrel=1+c2(0.80c)(0.30c)0.80c+0.30c
Simplifying the expression:
vrel=1.10c1+0.24vrel=1+0.241.10c
vrel=1.10c1.24vrel=1.241.10c
vrel≈0.89cvrel≈0.89c
So, the relative velocity of the two objects as they approach each other would be approximately 0.89 times the speed of light, cc.

What Would Happen?​

1. Impact and Energy Release: If these objects were to collide at this high relative velocity, the impact would release an enormous amount of energy, potentially causing both objects to be destroyed. The energy involved in such a collision would be much greater than what we experience in collisions at lower velocities.
2. Relativistic Effects: At velocities close to the speed of light, relativistic effects such as time dilation and length contraction become significant. These effects would need to be considered when analyzing the dynamics of the collision.
3. Limitation by Speed of Light: No object with mass can reach or exceed the speed of light relative to any other object, according to special relativity. The calculation above ensures that the relative velocity remains below the speed of light, respecting this fundamental limit.

In summary, even though individual objects are traveling at high speeds, their relative velocity will still be less than the speed of light due to the way velocities add in the framework of special relativity. The collision would result in an extremely high-energy impact, with significant relativistic effects.









ChatGPT can make mistakes. Che

 

[Neogaia777]

From ChatGPT:
In space, when two objects approach each other at high velocities, the relative speed at which they approach is not simply the sum of their individual speeds. Instead, we need to use the principles of special relativity to calculate the relative velocity.
When dealing with velocities that are significant fractions of the speed of light, the formula to calculate the relative velocity vrelvrel of one object with respect to another is given by:
vrel=v1+v21+v1v2c2vrel=1+c2v1v2v1+v2
where v1v1 and v2v2 are the velocities of the two objects, and cc is the speed of light.
Given:

• Object A's speed v1=0.80cv1=0.80c
• Object B's speed v2=0.30cv2=0.30c

Plugging these values into the formula:
vrel=0.80c+0.30c1+(0.80c)(0.30c)c2vrel=1+c2(0.80c)(0.30c)0.80c+0.30c
Simplifying the expression:
vrel=1.10c1+0.24vrel=1+0.241.10c
vrel=1.10c1.24vrel=1.241.10c
vrel≈0.89cvrel≈0.89c
So, the relative velocity of the two objects as they approach each other would be approximately 0.89 times the speed of light, cc.

What Would Happen?​

1. Impact and Energy Release: If these objects were to collide at this high relative velocity, the impact would release an enormous amount of energy, potentially causing both objects to be destroyed. The energy involved in such a collision would be much greater than what we experience in collisions at lower velocities.
2. Relativistic Effects: At velocities close to the speed of light, relativistic effects such as time dilation and length contraction become significant. These effects would need to be considered when analyzing the dynamics of the collision.
3. Limitation by Speed of Light: No object with mass can reach or exceed the speed of light relative to any other object, according to special relativity. The calculation above ensures that the relative velocity remains below the speed of light, respecting this fundamental limit.

In summary, even though individual objects are traveling at high speeds, their relative velocity will still be less than the speed of light due to the way velocities add in the framework of special relativity. The collision would result in an extremely high-energy impact, with significant relativistic effects.









ChatGPT can make mistakes. Che

I've been watching the show "How the Universe Works" lately, and it's a very interesting and informative and entertaining show, maybe you should try it, or try looking it up sometime. It's a very cool show. Might be able to find some of it on YouTube, IDK?

God Bless.

 

[Halbhh]

Considering that by chance perhaps with a swing around different galaxies, two free planets are moving towards each other at 30% and 80% light speed, the total is more than 100% and matter cannot naturally exceed light speed. What would happen around impact? In time and energy, would one planet turn into light?

Using the special relativity formula, the combined total approach velocity of the 2 planets towards each other would be about .89c.

 

[The Liturgist]

At relativistic speeds, speed doesn't 'add' normally.

In the scenario, presumably some observer sees one planet moving at 30% of c, and the other at 80% of c in the opposite direction.

But if you are an (unfortunate) observer on one of the two planets, you would see the other moving at:

88.71% the speed of light towards you.

It would be a heckuva collision, but nothing particularly strange would happen.

That said, in the ensuing collision, it seems likely some matter would get converted into energy relativistically, just like with a nuclear weapon. Indeed, if one of the two planets was made of antimatter, you might get a near 100% conversion into gamma rays.*

*I have a nagging suspicion that antimatter weapons, in the terrifying but fortunately somewhat unlikely scenario that anyone is ever able to build them, might be prone to “fizzle”, in that while certainly all of the antimatter would annihilate, the trick would be to get it to annihilate simultaneously. Thus their designers would be faced with a project similar to that faced by the Manhattan Project when designing plutonium weapons, which in that case was solved by von Neumann, who I have always particularly liked due to his enthusiastic support of the emergence of computer systems.

 

[essentialsaltes]

That said, in the ensuing collision, it seems likely some matter would get converted into energy relativistically, just like with a nuclear weapon.

Probably not substantially, at least in the way you're describing 'like a nuclear weapon'. Unless, as you suggest, one planet is antimatter.

I mean, matter/mass is energy. Those fast moving planets have a lot of kinetic energy. Another way to think of that (relativistically) is that they have a relativistic mass that is greater than their rest mass.

When they collide, in what I expect would be a very inelastic collision, a lot of that kinetic energy will get turned into heat and light ('energy'), but I expect there will be very little change to the rest masses of the matter making up the planets.

In a nuclear bomb, the energy doesn't come from kinetic energy, but from the difference in rest mass between the original nucleus and the fission products. Since mass is energy, any 'missing' mass emerges as energy.

 

[The Liturgist]

Probably not substantially, at least in the way you're describing 'like a nuclear weapon'. Unless, as you suggest, one planet is antimatter.

I mean, matter/mass is energy. Those fast moving planets have a lot of kinetic energy. Another way to think of that (relativistically) is that they have a relativistic mass that is greater than their rest mass.

When they collide, in what I expect would be a very inelastic collision, a lot of that kinetic energy will get turned into heat and light ('energy'), but I expect there will be very little change to the rest masses of the matter making up the planets.

In a nuclear bomb, the energy doesn't come from kinetic energy, but from the difference in rest mass between the original nucleus and the fission products. Since mass is energy, any 'missing' mass emerges as energy.

Indeed, I am aware of why nuclear weapons work, and that mass is energy.

I did not say “substantially.” I think some fission is inevitable if two planetary masses collide, because it is likely that, among other things, this might cause critical masses to form if fissile elements in each planet are amalgamated. Additionally, it is possible that enough heat in a sufficiently gravitationally constricted environment in the core of the planet might be produced so that one would see a short-lived fusion in which any lighter elements that became trapped between the two planets might fuse, but this would depend upon the speed of the impact, the composition of the planets and how precisely they collided with each other. I would be very surprised if the rest mass of the combined planet was not slightly less than the rest mass of the two original planets.

This is in addition to material which would likely be ejected from the combined planet in the process of the collision which would likely wind up orbiting it in the form of moons or a ring. Actually, that assumes a collision at sub-relativistic speeds; if we take things up to a relativistic velocity, where planet A collides head on with planet B at the velocities mentioned above, I would be surprised if the mass of the combined planet were not dispersed in a disk-shaped explosion. I think the planets would be obliterated in the process and the result would be the formation of a dust cloud, which might eventually coalesce into a new planet.

 

[The Liturgist]

As an amusing aside, the 1951 SF film When Worlds Collide happens to be on YouTube at the moment.

 

[sfs]

I did not say “substantially.” I think some fission is inevitable if two planetary masses collide, because it is likely that, among other things, this might cause critical masses to form if fissile elements in each planet are amalgamated.

No, nothing will be amalgamated in this kind of collision -- nothing is going to stick around long enough to cause any kind of chain reaction. If I'm not mistaken, the kinetic energy of an approaching nucleon (neutron or proton) in the rest frame of the other would be roughly 1.1 GeV, which is far higher than nuclear binding energies. So molecules and atoms would be pretty much irrelevant: atoms would be completely ionized and I would expect many (most? it's hard to picture the overall progression of the collision) nuclei to be completely disrupted, producing a spray of electrons, gamma rays, protons, neutrons, and alpha particles. Probably some positrons as well.

I would be very surprised if the rest mass of the combined planet was not slightly less than the rest mass of the two original planets.

Many nuclei would be blown apart at the velocities mentioned, not fused together, yielding constituents with higher rest mass. The one thing there won't be is anything resembling a planet.

I think the planets would be obliterated in the process and the result would be the formation of a dust cloud, which might eventually coalesce into a new planet.

Most resulting debris will likely have velocities far exceeding the escape velocity of the system.

 

[The Liturgist]

No, nothing will be amalgamated in this kind of collision -- nothing is going to stick around long enough to cause any kind of chain reaction. If I'm not mistaken, the kinetic energy of an approaching nucleon (neutron or proton) in the rest frame of the other would be roughly 1.1 GeV, which is far higher than nuclear binding energies. So molecules and atoms would be pretty much irrelevant: atoms would be completely ionized and I would expect many (most? it's hard to picture the overall progression of the collision) nuclei to be completely disrupted, producing a spray of electrons, gamma rays, protons, neutrons, and alpha particles. Probably some positrons as well.

Many nuclei would be blown apart at the velocities mentioned, not fused together, yielding constituents with higher rest mass. The one thing there won't be is anything resembling a planet.

Most resulting debris will likely have velocities far exceeding the escape velocity of the system.

This seems reasonable, given the extreme nature of planets colliding at relativistic velocities.

By the way, correct me if I’m wrong, but as far as I am aware, we are not aware of such a scenario happening, even in the case of galactic mergers, since it is expected that, for example, in the case of the merger of Andromeda with the Milky Way, and later of the Local Group Cluster, few planets or solar systems will collide due to the vast distance between them, and furthermore, these collisions would not be at the extreme relativistic velocities implied by the OP.

 

[Hans Blaster]

This seems reasonable, given the extreme nature of planets colliding at relativistic velocities.

By the way, correct me if I’m wrong, but as far as I am aware, we are not aware of such a scenario happening, even in the case of galactic mergers, since it is expected that, for example, in the case of the merger of Andromeda with the Milky Way, and later of the Local Group Cluster, few planets or solar systems will collide due to the vast distance between them, and furthermore, these collisions would not be at the extreme relativistic velocities implied by the OP.

The relative velocity between galaxies in collision is a few hundred km/s (not even close to relativistic). For a planet to reach orbital speeds like those in the OP, the orbit would be so tight, the planet would probably fall with in the Roche limit of the object it was orbiting and break apart. It is at most a thought exercise.

 

[Tinker Grey]

It's worth noting that the average distance between asteroids is around 600,000 miles. That's 2.5+ time the distance between Earth and the moon. The average distance between stars is 5 light years. <- that's 6.8 million times the diameter of the sun.

That's a lot of space.

 

[The Liturgist]

The relative velocity between galaxies in collision is a few hundred km/s (not even close to relativistic). For a planet to reach orbital speeds like those in the OP, the orbit would be so tight, the planet would probably fall with in the Roche limit of the object it was orbiting and break apart. It is at most a thought exercise.

That was my understanding. I merely sought to make sure I was correct.

 

[The Liturgist]

It's worth noting that the average distance between asteroids is around 600,000 miles. That's 2.5+ time the distance between Earth and the moon. The average distance between stars is 5 light years. <- that's 6.8 million times the diameter of the sun.

That's a lot of space.

Indeed. God has given us a universe which reflects the splendor inherent in the union of the persons of the Father, Son and Holy Ghost, ever one God, whose existence transcends spacetime, which He created.

 

[sjastro]

While stars present a small target in galaxy mergers the same cannot be said of gas and dust.

The dark lane in my image of Centaurus A which is a merger between an elliptical and spiral galaxy is the result of shock waves which compresses the gas and dust clouds from each galaxy triggering star formation activity.
A supermassive black hole at the centre of the merger feeds off the gas and dust and produces electromagnetic radiation across the spectrum.

 

[sjastro]

A supermassive black hole at the centre of the merger feeds off the gas and dust and produces electromagnetic radiation across the spectrum.

Here is an example of Centaurus A at different wavelengths of the spectrum.
Near UV reaches the earth's surface but since my CCD is not an efficient UV detector I had to add blue light from Centaurus A to the near UV image to produce a sufficiently high S/N ratio.