Would we as humans ever be able to travel close to the speed of light?

[zeromodz]

I mean how would we ever do it in the first place? What rockets or propulsion units would we use?

 

[mgb_phys]

It doesn't affect measurements you make in your own reference frame.
You wouldn't notice getting shorter, more massive, slower - only an outside observer would.
That's rather the whole point of relativity.

 

[cfrogue]

It doesn't affect measurements you make in your own reference frame.
You wouldn't notice getting shorter, more massive, slower - only an outside observer would.
That's rather the whole point of relativity.

The SR acceleration equations provide a different and impossible answer.

How much fuel is this? The next chart shows the amount of fuel needed (M) for every kilogramme of payload (m=1 kg).

d Not stopping, sailing past: M
4.3 ly Nearest star 10 kg
27 ly Vega 57 kg
30,000 ly Center of our galaxy 62 tonnes
2,000,000 ly Andromeda galaxy 4,100 tonnes
http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html

 

[DaveC426913]

I mean how would we ever do it in the first place? What rockets or propulsion units would we use?

Well, it's untold centuries in the future, so the technology we'll use is going to be even weirder than anything we could dream of.

Ask a roman centurion how we will power our hybrid cars in the 21st century. (What's a hybrid car? What's a car?)

 

[atyy]

But the Earth is already traveling at 0.99999999999c , so we are traveling close to the speed of light.

 

[DaveC426913]

How much fuel is this? The next chart shows the amount of fuel needed (M) for every kilogramme of payload (m=1 kg).

d Not stopping, sailing past: M
4.3 ly Nearest star 10 kg
27 ly Vega 57 kg
30,000 ly Center of our galaxy 62 tonnes
2,000,000 ly Andromeda galaxy 4,100 tonnes

Since there are no constraints on imagining how we do it, I would guess that, if/when we manage to do this, it will be by
a] not having to bring our fuel with us
b] using something more efficient than "primitive" total conversion of mass to energy.

 

[cfrogue]

Since there are no constraints on imagining how we do it, I would guess that, if/when we manage to do this, it will be by
a] not having to bring our fuel with us
b] using something more efficient than "primitive" total conversion of mass to energy.

I vote for the no fuel option and pick up random particles in space, ...

lots of them.

 

[cfrogue]

Since there are no constraints on imagining how we do it, I would guess that, if/when we manage to do this, it will be by
a] not having to bring our fuel with us
b] using something more efficient than "primitive" total conversion of mass to energy.

How silly of me.

Atyy already has this figured out.

We start out at 0.99999999999c and we do not need to worry about all this.

Sometimes, the answer can be so simple.

 

[DaveC426913]

How silly of me.

Atyy already has this figured out.

We start out at 0.99999999999c and we do not need to worry about all this.

Sometimes, the answer can be so simple.

OK, all seriousness aside, I'm pretty sure the point of pushing c is to get some distance from Earth.

 

[Matterwave]

I vote for the no fuel option and pick up random particles in space, ...

lots of them.

Only problem with that is the interstellar medium is oh so sparse...you'd need a catching tool on the order of Astronomical units across just to get a few particles.

The interstellar medium is a much better vacuum than any vacuum we've ever been able to create on Earth.

I suppose you could just boost off each star system tho. Aim for one star system at a time, and bring enough fuel for ~10 Light-years of travel.

 

[cfrogue]

Only problem with that is the interstellar medium is oh so sparse...you'd need a catching tool on the order of Astronomical units across just to get a few particles.

The interstellar medium is a much better vacuum than any vacuum we've ever been able to create on Earth.

I suppose you could just boost off each star system tho. Aim for one star system at a time, and bring enough fuel for ~10 Light-years of travel.

Fine then,.

I say drive by planets and whatever else and suck their mass.

I note I can buy the latest vacuum cleaners on TV and they are guaranteed..

 

[atyy]

OK, all seriousness aside, I'm pretty sure the point of pushing c is to get some distance from Earth.

mgb-phys and I answered when the original question was: would traveling near the speed of light Lorentz contract our organs and kill us?

 

[Matterwave]

In your own reference frame, nothing changes. You would see the universe around you contract though...that would be quite weird! =P

 

[cfrogue]

mgb-phys and I answered when the original question was: would traveling near the speed of light Lorentz contract our organs and kill us?

You failed to consider the acceleration to get you there.

We have a recent thread on the Born issue about this.

 

[DaveC426913]

mgb-phys and I answered when the original question was: would traveling near the speed of light Lorentz contract our organs and kill us?

When was that the original question?

 

[cfrogue]

mgb-phys and I answered when the original question was: would traveling near the speed of light Lorentz contract our organs and kill us?

The born thread shows our organs would expand during acceleration.

 

[DaveC426913]

The born thread shows our organs would expand during acceleration.

What??

 

[ideasrule]

In case anybody doesn't know about this, see:

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

Orion spacecraft , which are actually possible to build today, can achieve 8-10% the speed of light using hydrogen bombs and 50-80% the speed of light using matter-antimatter annihilation. If it's possible to store antimatter, relativistic space travel is certainly possible.

BTW, Dave, did you just say "all seriousness aside"?

 

[cfrogue]

What??

?
the born thread recently shows during acceleration, all expands in the accelerasting frame.

 

[atyy]

When was that the original question?

Oh, I don't know. Maybe I was dreaming, but mgb_phys's answer makes much more sense if he also had the same dream. Anyway, it doesn't matter.

 

[DaveC426913]

?
the born thread recently shows during acceleration, all expands in the accelerasting frame.

Is English not your first language? That's not even a sentence.

 

[cfrogue]

Is English not your first language? That's not even a sentence.

hear is the thred

https://www.physicsforums.com/showpost.php?p=2443198&postcount=36

please make sure you read ther paper

 

[matheinste]

I mean how would we ever do it in the first place? What rockets or propulsion units would we use?

Not a very popular opinion in some quarters, but I believe that eventually humans will achieve everything that is theoretically possible. The laws of physics are our only limitations, all technologies required will eventuially become realities.

Matheinste.

 

[DaveC426913]

hear is the thred

https://www.physicsforums.com/showpost.php?p=2443198&postcount=36

please make sure you read ther paper

What are you telling me? That this thread is a continuation of that thread? Is that what you mean when you say "born thread"? Am I the only one here that did not know there was a previous thread?

 

[cfrogue]

What are you telling me? That this thread is a continuation of that thread? Is that what you mean when you say "born thread"? Am I the only one here that did not know there was a previous thread?

No, I was telling you acceleration under SR expands the internal metrics of the accelerating frame.

 

[Matterwave]

No, I was telling you acceleration under SR expands the internal metrics of the accelerating frame.

This makes no sense. SR is a theory that is devoid of accelerating reference frames, and only considers inertial reference frames, that's why it's Special. You mean GR?

 

[yossell]

This makes no sense. SR is a theory that is devoid of accelerating reference frames, and only considers inertial reference frames, that's why it's Special. You mean GR?

What? SR can deal with acceleration - it's gravity that requires GR.

Maybe there are different understandings of 'frames' at play. One sense, just focus on an accelerating object - say a rocket ship - and ask how clocks and rods stationary with that rocket ship would behave. On another sense, 'frame' is short for 'inertial frame' - in which case, a frame can't be accelerating. Behaviour of objects in an accelerating rocket ship can be done within SR.

Of course, speed of light is not measured to be c, and the laws don't have the same form from the point of view of an accelerating frame. But SR alone will tell you that.