# Striving Speed of Light?

1. Jul 19, 2011

### wilsonb

Can we hold on..stand up inside spacecraft that close 99% speed of light and can our physical effort to hold on that speed?

2. Jul 19, 2011

### edgepflow

Sure, if it is constant 99% speed of light, it is no different than sitting in your living room.

The danger is in the acceleration you experience reaching this speed.

3. Jul 19, 2011

### Pengwuino

Velocities aren't important, as edgepflow noted; it's the acceleration. That's why if you're on a bullet train going 250mph, you'd only know it by looking out the window and that's why everyone just walk around drinking tea and reading the newspaper inside one.

4. Jul 21, 2011

### wilsonb

Well, like we stay on the plane with speed, but we manage to walk inside without force back. But its gravity where let us stay on and walk. What bout space without gravity? Example: a tiny object with barely no weight, put inside of a big balloon, then try to pull the balloon ahead with speed, the object without gravity will be force backward inside the balloon... Sine the object wasn't stay or touch the balloon....

5. Jul 21, 2011

### Pengwuino

That's only because you're accelerating the balloon. Once you reach whatever speed you're looking for and stop accelerating, the object will float in the balloon. As for the airplane, yes gravity does provide a practical means to move around, but if you turned gravity off, you wouldn't be flung backwards if you're going at a constant velocity. You simply wouldn't be able to actually move anywhere because you need some sort of friction (or you could strap a small rocket onto you to get around).

6. Jul 21, 2011

### wilsonb

my opinion is:
when no other force apply on a mass, its speed will be constant.
when acceleration applies, speed increases.
more acceleration = more speed -> until speed is near to infinity

light is nothing more than a combination of magnetic & electronic wave with tremendous traveling speed. because it is the fastest thing human beings have found so far, einstein could only come out with the m c square before he died.

newton's theories cannot be applied on quantum theories, which was proposed 300 years later. we shall see 300 years after the accurate measurement of speed of light what equations the scientists will come out with.

7. Jul 21, 2011

### Staff: Mentor

All good except for that last step. Regardless of its proper acceleration, the ship will never reach, much less exceed, the speed of light.

8. Jul 21, 2011

### nitsuj

Yea, he used the word infinity. A good choice that also gets your point across.

9. Jul 21, 2011

### ghwellsjr

No matter how much you have accelerated in the past and no matter what speed you will have attained relative to your starting condition, the speed of light will still be just as unattainable as it was when you started. You won't be able to tell any difference between starting and after you have accelerated, except that lots of things will be flying past you (hopefully, instead of hitting you, which would put an end to your endeavors).

10. Jul 21, 2011

### Drakkith

Staff Emeritus
This is incorrect. It is PROVEN that c is unreachable and is a universal constant. The LHC in Geneva accelerates protons to greater than 99.99% the speed of light. The amount of energy it takes to get them up to speed agrees exactly with our calculations and predictions. Not only that, but e=mc^2 agrees with how much energy and mass are lost and gained in any chemical or nuclear reaction. If c was not correct then it would NOT work. The constant c is much more than simply a speed limit.

11. Jul 22, 2011

### GrayGhost

True Doc Al, but there is a sense in which infinite velocity applies mathematically. If one could attain speed c, the cosmos shrinks to a plane figure, and one then travels a finite distance in zero time. So speed c plays the role of an infinite velocity in STR. Yes? But then, I suppose "said one" may not even be considered to be moving at that venture, and would move (at c) only per sub c folks.

GrayGhost

12. Jul 22, 2011

### GrayGhost

When I do it, my legs fly out about 88.1 degrees wrt the horizontal :)

On a serious note, so long as you are not accelerating, you would float freely in your vessel just as the shuttle astronauts do in orbit. If you are not accelerating, you may consider yourself stationary.

GrayGhost

13. Jul 22, 2011

### Drakkith

Staff Emeritus
I can only point to the (fact?) that a photon has no frame of reference.

14. Jul 22, 2011

### mathfeel

But you are moving at this speed right now in some reference frame. And I see you are holding up pretty good.

15. Jul 22, 2011

### wilsonb

Can gravity be manipulated?
gravity.. Space was 0 to gravity. Can we build a machine or what ever to provide gravity? Although we can build space ship, there won't be any gravity wouldn't it? Any proof or article where gravity can be produce? Human will getting weak if no gravity, that's why astronaut need to do exercises often when they in the space. When they come back to earth, they are weak because they have stay long time at space without gravity...

16. Jul 22, 2011

### Ryan_m_b

Staff Emeritus
The only thing that can generate gravity is mass however you could http://en.wikipedia.org/wiki/Artificial_gravity#Rotation".

Last edited by a moderator: Apr 26, 2017
17. Jul 22, 2011

### Cosmo Novice

An easier solution to muscle entropy attributable to zero-g is using resistance training methods. The Coriolis effect has some pretty weird side effects! Saying that the rpm can be a lot less and still produce a simulated gravity field.

There is a very interesting couple of paragraphs in Arthur C Clarkes Rama novel - while a science fiction its tends to be more "hard" sci fi and raises some interesting questions on how we would mentally as well as physically deal with a simulated gravity environment. Perception of motion and up/down etc. Not fact obviously but from a scientifically very credible author so raises real concerns.

Last edited by a moderator: Apr 26, 2017
18. Jul 22, 2011

### Ryan_m_b

Staff Emeritus
I don't think resistance training would cut it I'm afraid. Bone mineral loss, heart muscle atrophy, fluid loss etc. The human body evolved to live in a specific environment, it doesn't bode well for drastic changes!

On the subject of Coriolis forces I wonder how people's perception would change with larger diameters?