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## Main Question or Discussion Point

What is the reason for this?

- Thread starter homeylova223
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What is the reason for this?

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mathman

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it would need infinite energy to do so.

- #4

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I mean the speed of light is a fixed number so is there not a fixed number of energy unit that can reach this speed.

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ghwellsjr

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Most people can see the difference between 1/2 and 100 percent.

I mean light goes 365,000 km/s according to observations.

Force is mass times acceleration

Therefore

acceleration is Force/mass

If a strong enough force is applied an object could accelerate faster than the speed of light.

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Another thing that stops you is that as you go faster, time slows down for you. Again, weird, but it just does. Literally...your watch will show one hour has passed, while on earth perhaps a year or century has passed. The result is that you can be close to the speed of light and hit the gas and feel a huge surge of acceleration....BUT, in fact if someone on earth measured your acceleration it might be close to zero, because what was a second for you might be a thousand years on earth.

So then you might try to measure your speed, perhaps against a light beam. Well...that's useless, because light ALWAYS travels at the speed of light away from you. Even if you yourself are going at 99.9999% the speed of light. Again, doesn't make sense but that's how it is. Trying to catch a light beam would be like trying to reach the horizon.

So basically, the universe doesn't allow you to reach this speed. Your mass rises, your energy rises, your time slows, bunch of other things happen. In order for you to get to the speed of light, your mass would have to be infinity, your energy infinity, and time would be zero. Not even the mathematics allow you to do this, as you'd end up multiplying by infinity and dividing by zero and, well, good luck with that....

- #8

russ_watters

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Well, perhaps the easiest way to explain is that it turns out that equation is wrong. It works pretty well at low speed, but fails at high speed. Newton didn't have access to a particle accelerator, so he didn't know.I mean light goes 365,000 km/s according to observations.

Force is mass times acceleration

Therefore

acceleration is Force/mass

If a strong enough force is applied an object could accelerate faster than the speed of light.

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- #10

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We keep making particle accelerators multiple times more powerful than the ones before them, and yet all they can do is add another 9 to the 99.9......9% the speed of light that the particles actually reach.

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ghwellsjr

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It still won't be faster than the speed of light.

- #13

ghwellsjr

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With low velocities, the formula for calculating the velocity, v, after an acceleration, a, for a time, t, is:

Most people can see the difference between 1/2 and 100 percent.

I mean light goes 365,000 km/s according to observations.

Force is mass times acceleration

Therefore

acceleration is Force/mass

If a strong enough force is applied an object could accelerate faster than the speed of light.

[tex]v = a t[/tex]

So this says you could apply any acceleration for a long enough time and get v to exceed c. Or if you had a high enough acceleration, for a shorter time, it says you could get v to exceed c.

But this formula is only an approximation where the velocities end up being very small compared to c.

The correct formula is:

[tex]v = \frac{a t}{\sqrt{1+(a t/c)^2}} [/tex]

If you look carefully at this formula you will see that when [tex]a t[/tex] is very small, the formula approximates to:

[tex]v < \frac{a t}{\sqrt{1}} [/tex]

[tex]v < a t [/tex]

This is similar to the original formula.

But when [tex]a t[/tex] is very large, the formula approximates to:

[tex]v < \frac{a t}{\sqrt{(a t/c)^2}} [/tex]

[tex]v < \frac{a t}{(a t/c)} [/tex]

[tex]v < \frac{1}{(1/c)} [/tex]

[tex]v < c [/tex]

So in reality, no matter how much you accelerate, or how long you accelerate, you can never reach c.

Now to answer your other question about going one half the speed of light, I was trying to show you that since it is possible to accelerate to that speed, then you should be able to get to 100%c in two accelerations and even faster in three, correct? The only problem is that after each step, if you measured the speed of light, you will still measure it as c and you will be no closer than you were before you started. You could repeat this as many times as you wished and still not get any closer to the speed of light.

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