speed of light

[skulldude]

We have found out rockets that resist the friction of our earth and do not catch fire. Similarly why is it not possible to discover a machine that travels with or greater than the speed of light. It will really boost our space research?

[NeonBlack]

The two have nothing in similar.

[CaptainPanic]

If your second question is: "Will a device capable of going faster than light boost space research?", then my answer is: "yes".

 

For the rest I say:

 

Our modern rockets can go something like 10000 m/s

Light travels 299000000 m/s

 

So to go from very fast rockets to lightspeed, we still need to find a way to go about 30000x faster than our rockets.

[insane_alien]

which will use 30000xinfinty more energy.

[CaptainPanic]

E = 0.5*m*v^2

 

So actually it will take 30,000*30,000 = 900,000,000x as much energy (900 million).

 

And I believe there's some quantum kinda problems that say that anything that has mass (that includes you, me and the rocket) that travels AT lightspeed needs an infinite amount of energy. But I can't give you any funny formula's about energy costs at lightspeed.

 

I think talking about lightspeed traveling while we have trouble going to Mars or the moon is like talking about highways and racecars when you haven't even invented the wheel. It's fun, but it makes little sense

[Klaynos]

E = 0.5*m*v^2

 

So actually it will take 30,000*30,000 = 900,000,000x as much energy (900 million).

 

And I believe there's some quantum kinda problems that say that anything that has mass (that includes you, me and the rocket) that travels AT lightspeed needs an infinite amount of energy. But I can't give you any funny formula's about energy costs at lightspeed.

 

I think talking about lightspeed traveling while we have trouble going to Mars or the moon is like talking about highways and racecars when you haven't even invented the wheel. It's fun, but it makes little sense

 

This equation is not valid for calculating the energy differences at speeds close to the speed of light.

[Janus]

E = 0.5*m*v^2

 

So actually it will take 30,000*30,000 = 900,000,000x as much energy (900 million).

 

And I believe there's some quantum kinda problems that say that anything that has mass (that includes you, me and the rocket) that travels AT lightspeed needs an infinite amount of energy. But I can't give you any funny formula's about energy costs at lightspeed.

 

I think talking about lightspeed traveling while we have trouble going to Mars or the moon is like talking about highways and racecars when you haven't even invented the wheel. It's fun, but it makes little sense

 

That equation only gives a a good answer at relatively low speeds (conpared to light).

 

More acturate would be:

 

[math]E = mc^2 \left ( \frac{1}{\sqrt{1- \frac{v^2}{c^2}}}-1 \right )[/math]

[swansont]

The problem of traveling at lightspeed is not an engineering issue, as far as current science tells us.

[Reaper]

To expand upon what ^ said, try plugging in the speed of light for v, and see what happens....

[thedarkshade]

We have found out rockets that resist the friction of our earth and do not catch fire. Similarly why is it not possible to discover a machine that travels with or greater than the speed of light. It will really boost our space research?

Energy energy energy! You need infinite energy to send any kind of substance with rest mass at the speed of light!

 

You easily work that out:

 

As [math]m=\frac{m_0}{\sqrt{1-\beta^2}}[/math] then just replace m in [math]E=mc^2[/math] and you'll get:

 

[math]E=\frac{m_0c^2}{\sqrt{1-\beta^2}}[/math] and taking v=300000km/s you will get zero under the fraction and anything divided by zero tends toward infinity, hence you need infinite energy!

[NeonBlack]

 

As [math]m=\frac{m_0}{\sqrt{1-\beta^2}}[/math]

 

Darkshade, forget you ever saw this equation.

There is no "relativistic mass." The factor of gamma that you see is due to time dilation, not an increase in mass.

[thedarkshade]

Darkshade, forget you ever saw this equation.

There is no "relativistic mass." The factor of gamma that you see is due to time dilation, not an increase in mass.

That's not what My intention was (which is clear enough) to show that anything with rest mass cannot reach c since infinite energy is needed, and this is shown good enough by the above equation I have pointed!

[NeonBlack]

I know what your intent was, but you arrived at your conclusion by the wrong means.

 

And stop saying "rest mass." It's just mass.

[kaneda]

We know from accelerating basic atomic particles that there comes a speed which is almost light speed beyond which they will not go and increasing their energy just makes them more massive. EMR and gravity travel at light speed and everything else slower.

 

While in theory a rocket could travel at a constant acceleration and eventually reach almost light speed (maybe in many thousands of years), it would need a planet sized fuel tank (which would of course slow it down) for such a trip.

 

We need a new type of propulsion. If you had told people 110 years ago that we could in the year 2000 cross the Atlantic in 5 hours and ask how we did it, they would imagine some kind of super sailing ship with loots of sails and never guess something like Concorde. At present, we cannot guess what will get us to the stars but it will hopefully come along in our lifetimes.

[swansont]

I know what your intent was, but you arrived at your conclusion by the wrong means.

 

And stop saying "rest mass." It's just mass.

 

Unfortunately there are multiple definitions of mass, since there is the "relativistic mass" equation used by some. At least saying rest mass avoids some of the confusion.

[thedarkshade]

At least saying rest mass avoids some of the confusion.

Yup! I wrote that on purpose to tell the OP that anything with rest mass cannot be sent, reach or move at the speed of light. As for the reason why, this forum is overloaded by that sentence!

[NeonBlack]

Swans, I don't know how many people doing serious physics have used relativistic mass in the past few decades, but I'm sure it must be in the vast minority. Most textbooks today will either make no mention it or only mention it to discourage its use. Not only is it pointless and confusing, but it is wrong. The factor of gamma that somehow gets attached to mass actually comes from time dilation (See the thread about Why c in E=mc2?).

 

As a compromise, I am willing to say rest mass, as long as nobody says relativistic mass or implies that mass can be a function of speed.

[swansont]

Swans, I don't know how many people doing serious physics have used relativistic mass in the past few decades, but I'm sure it must be in the vast minority. Most textbooks today will either make no mention it or only mention it to discourage its use. Not only is it pointless and confusing, but it is wrong. The factor of gamma that somehow gets attached to mass actually comes from time dilation (See the thread about Why c in E=mc2?).

 

As a compromise, I am willing to say rest mass, as long as nobody says relativistic mass or implies that mass can be a function of speed.

 

It's not the physicists that generally cause the problem. Most people posting here with such questions aren't physicists.

 

But the factor of gamma shows up in momentum, too, and in total energy, and I think that adds to the confusion.

[Dark matter]

Question: How are these topics similar>?

 

You might want to look at Einstein's theory or Relativity, or Relative mass.

 

Best of luck

[Slinkey]

......

[math]E=\frac{m_0c^2}{\sqrt{1-\beta^2}}[/math] and taking v=300000km/s you will get zero under the fraction and anything divided by zero tends toward infinity, hence you need infinite energy!

 

What about for speeds greater than 300000km/s?

 

The energy equations given above tell us that when v = c we are dividing by zero and it is meaningless. This tells us that relativity is only valid for sub-luminal speeds and breaks down when v = c.

 

The corrolary in GR is the singularity. GR predicts a singularity but cannot tell you anything more about it. Everyone seems to be generally agreed that within GR something else is needed to describe a singularity, but no one seems to be saying this about SR. My thoughts are that SR leads to a kind of ultraviolet catastrophe because it is not quantized.

 

Does anyone disagree that energy comes in packets? I hope not. How does this apply to GR and SR? The golden question, I know, but without it not only is GR incomplete but so is SR. Maybe when we have fused GR and QM we will understand something different about v=c and there might be no requirement for infinite resources to fuel your spaceship up to light speed.

 

My bet is that we end up with a quantized universe where movement is not smooth but trillions of quantum leaps one after the other.

[Klaynos]

SR is a specialist case of GR...

 

SR being incomplete lead onto GR... which is also incomplete but will hopefully lead to something else

 

QM and relativity are used in conjunction quite frequently, only around certain areas do they break down....

[Slinkey]

SR is a specialist case of GR...

 

SR being incomplete lead onto GR... which is also incomplete but will hopefully lead to something else

 

QM and relativity are used in conjunction quite frequently, only around certain areas do they break down....

 

Notably at singularities and at c. In fact there are many issues surrounding black holes that I am not happy about but they are all expressed in anither thread on this forum somewhere so I won't repeat them here.

 

What do you think of the idea of quantized movement?

[Klaynos]

Well I can understand why you like the idea of it, and there's alot of people who will tell you that the plank length will turn out to be something to do with quantum gravity and blackholes....

[NeonBlack]

Slinkey, when you say a theory breaks down at a singularity, you are simply stating the definition of the word. And since relativity is singular at v=c, (for massive objects anyway) this is doubly redundant. I am only saying this because so many people don't understand what a "singularity" is.

 

Klaynos, speaking of which, do you know what happened to Ben "the man"?

[Slinkey]

Well, I understood a singularity to be the point where the math breaks down usually due to divisions by zero b ut your point is taken.