'Second Earth' found, 20 light years away

[OilKiller]

Wow...my head hurts after reading this thread. Think I'm going to go watch Jerry Springer now...

[lifer]

So you're saying that if it was possible to travel there at the speed of light we could send Bob Cole and Harry Neale to this planet, bring them back and they would still be the same age (well, physically and mentally) and then they could call the Leafs game on opening day of the 2047 NHL season and mark the 80th anniversary of no Stanley Cups in the Centre of the Universe?
That totally blows my mind.

[4X4]

^^ that deserves a red square

[metal_geek]

Think about traveling at the speed of light with 1 clock behind you and 1 beside you in your light speed machine.

Standing still, both clocks point directly at 12:00...


For simplicity sake.. say you instantly start moving at the speed of light. You look behind you and the light comming from the hands of the clock is moving at the same speed as you, so what you see is the clock still pointing at 12:00. Because you are going at the same speed the light never has a chance to catch you. Think of it like running the same speed as bullet, as long as you are going the same speed as it is, you are not gonna get shot, it stays a constant distance behind you. What do you think is gonna happen with that bullet when you stop? Say You travel for 10 min at light speed, according to the clock on your machine.. then come to a full stop.

The light from the clock behind you starts catching up to you and the hand would appear to start moving, same as the bullet would. The clock would appear to be 10 min behind the one in your ship, because the light that left 10 min ago is only starting to pass you now..

You start moving at the speed of light again. The clock behind you stops again at 12:01 your inside clock says 12:11. Now you turn on Light after burners and are suddenly going Faster then the speed of light. Now you are catching upto and passing the light the left the clock behind you.. so it starts to move backwards... and after another min of travel your ship clock says 12:12 and the clock behind you says 12:00 again.. you keep going and the clock behind you starts showing 11:59....58....57 and you clock reads 13..14...15...

Techincally you are going BACK in time. All the while you are moving the pace of time back at the other clock never changed..

So as you are moving away from the clock behind you, the faster you go, the slower time moves on that clock untill you hit the speed of light at which time STOPS. So while time stops for you the people back at the first clock have been continuing to watch the clock at the normal time speed. You appear to have been gone MUCH longer then them because time has slowed to a crawl or stopped for you. So your 15 min of travel to you has taken 10's of years to the people behind you.
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[Cube Inmate]

In addition to time dilation, there's also compression of length. Two sides of the same coin, really. The length that a relativistic traveller measures in the direction of his motion is shortened by an amount depending on his speed. This is the Lorentz contraction.

Travelling at 90% of the speed of light (0.9c), the Lorentz contraction is a factor of about 2.3. The distance that we on Earth would measure as 20 light years would only be 20/2.3 = 8.7 light years to the astronaut. If he increases his velocity to 0.99c, the contraction factor is about 7 times, so the astronaut would measure it to be only 2.85 light years. As you go faster, the contraction factor approaches infinity as speed approaches the speed of light. Thus, IF a traveller could travel at the speed of light, the Lorentz contraction would be infinite and, in theory, he would simultaneously occupy all points in the universe.

Nope...ain't going to happen.

Any physicists are welcome to correct me.

[worth]

Sorry, that's not correct metal geek. Light travels at the speed of light no matter how fast you are going. If you are going 50% the speed of light, you're not 50% away from matching the light. You're still 100% away.

http://www.physlink.com/Education/AskExperts/ae558.cfm

[evman150]

Originally Posted by Cube Inmate

In addition to time dilation, there's also compression of length. Two sides of the same coin, really. The length that a relativistic traveller measures in the direction of his motion is shortened by an amount depending on his speed. This is the Lorentz contraction.

Travelling at 90% of the speed of light (0.9c), the Lorentz contraction is a factor of about 2.3. The distance that we on Earth would measure as 20 light years would only be 20/2.3 = 8.7 light years to the astronaut. If he increases his velocity to 0.99c, the contraction factor is about 7 times, so the astronaut would measure it to be only 2.85 light years. As you go faster, the contraction factor approaches infinity as speed approaches the speed of light. Thus, IF a traveller could travel at the speed of light, the Lorentz contraction would be infinite and, in theory, he would simultaneously occupy all points in the universe.

Right on (although I didn't calculate the Lorentz factors myself).

[MolsonInBothHands]

My simple brain is seeing contradictions.

Does light bend around strong gravitational pulls like that of a black hole? and if so, does a photon, a light particle have mass? and if so, how is it that something with mass is travelling the speed of light?

As well, in regards to the Lorentz contraction theory, does it really take 20 years for light to travel 20 light years if the contraction occurs and photons have mass, and so on?

My head hurts.

[worth]

Yes light bends around gravity. You can see it during a lunar eclipse, light will bend around the moon and distant stars will be shifted over a bit compared to when there is no moon in the way.

And yeah, you are encountering contradictions. Not sure if those have actually been answered by scientists or if they just chalk it up to one of those things.

I'm not so sure they actually know what makes up light. I think the photon has a shady past, but i'm sure these other guys in here know a lot more.

[metal_geek]

Originally Posted by worth

Sorry, that's not correct metal geek. Light travels at the speed of light no matter how fast you are going. If you are going 50% the speed of light, you're not 50% away from matching the light. You're still 100% away.

http://www.physlink.com/Education/AskExperts/ae558.cfm

Not realtive to the photon of light that was emmitted from the hand of the clock that was at a fixed point. That photon of light would never catch up to you if you were traveling at the same speed as that photon... Hence the time back on the ground appears to stop.. according to the light from that clock..

As you slow back down from the speed of light the time back on the ground would appear to be speeding up as the difference between your speed and the constant speed of the light behind you increases.
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[evman150]

Originally Posted by MolsonInBothHands

My simple brain is seeing contradictions.

Does light bend around strong gravitational pulls like that of a black hole? and if so, does a photon, a light particle have mass? and if so, how is it that something with mass is travelling the speed of light?

As well, in regards to the Lorentz contraction theory, does it really take 20 years for light to travel 20 light years if the contraction occurs and photons have mass, and so on?

My head hurts.

The Lorentz Transformation Equations are not theory.

Photons do not have mass. They do have momentum (p=hf).

Yes light bends around mass. This was one of the original cases that proved General Relativity.

It takes the light 20 years, from our perspective, to get here.

Don't worry, my head hurts too.

[jammies]

Originally Posted by worth

Yes light bends around gravity. You can see it during a lunar eclipse, light will bend around the moon and distant stars will be shifted over a bit compared to when there is no moon in the way.

And yeah, you are encountering contradictions. Not sure if those have actually been answered by scientists or if they just chalk it up to one of those things.

Rather than thinking of gravity as attracting mass, think of it as bent space. So the photons are shifted because space itself has curvature and they must follow the "straight" path along that geodesic. The idea of gravity being a force between two masses is somewhat incomplete, and is one of the things resolved by Einsteinian physics that was not by Newtonian; in fact the measure of the curvature of starlight around the sun was one of the compelling proofs of relativity, since the predicted curvature by the Theory of Relativity was correct and predictions by Newtonian physics were not.

[evman150]

Originally Posted by worth

I'm not so sure they actually know what makes up light. I think the photon has a shady past, but i'm sure these other guys in here know a lot more.

The photon does not have a shady past. And yes they do know what light is made of.

Light is quantized. The quanta are called photons. Each photon has a characteristic wavelength (or frequency). Photons have no mass. They have a momentum (which I just realized is not equal to hf, but hf/c).

Light also acts as a wave. This is what you are most likely thinking of when you say the photon has a "shady past". How can something be a particle and a wave at the same time? Googling "wave particle duality" does wonders.

http://physics.about.com/od/lightopt...veparticle.htm

The most common interpretation is that the wave function represents the probability of finding a given particle at a given point. These probability equations can diffract, interfere, and exhibit other wave-like properties, resulting in a final probabilistic wave function that exhibits these properties as well. Particles end up distributed according to the probability laws, and therefore exhibit the wave properties. In other words, the probability of a particle being in any location is a wave, but the actual physical appearance of that particle isn't.

That sums it up very nicely. Too much nomenclature though maybe, not sure.

[foofighter15]

This just in Gary Bettman determined to make the NHL successful puts a new team on Second Earth of the Libra constellation. Groans come from the teams of the western conference as the "Second Earth Skywalkers" don't leave the eastern time zone after their December road trip.

[MolsonInBothHands]

The most common interpretation is that the wave function represents the probability of finding a given particle at a given point. These probability equations can diffract, interfere, and exhibit other wave-like properties, resulting in a final probabilistic wave function that exhibits these properties as well. Particles end up distributed according to the probability laws, and therefore exhibit the wave properties. In other words, the probability of a particle being in any location is a wave, but the actual physical appearance of that particle isn't.

Wow, that makes sense. I'm still trying to wrap my head around momentum without mass though. Layman's terms for quanta might help. Off googling I go, my employer didn't want me to be productive anyway.

[troutman]

Originally Posted by evman150

The photon does not have a shady past. And yes they do know what light is made of.

Light is quantized. The quanta are called photons. Each photon has a characteristic wavelength (or frequency). Photons have no mass. They have a momentum (which I just realized is not equal to hf, but hf/c).

Light also acts as a wave. This is what you are most likely thinking of when you say the photon has a "shady past". How can something be a particle and a wave at the same time? Googling "wave particle duality" does wonders.

http://physics.about.com/od/lightopt...veparticle.htm

That sums it up very nicely. Too much nomenclature though maybe, not sure.

[photon]

Originally Posted by MolsonInBothHands

Wow, that makes sense. I'm still trying to wrap my head around momentum without mass though. Layman's terms for quanta might help. Off googling I go, my employer didn't want me to be productive anyway.

It might help to remember that while light has no mass, it does have energy (and energy and mass are interchangeable).

I think this used to be referred to light not having a rest mass but having a relativistic mass, but I don't think they use that anymore.

[MolsonInBothHands]

Originally Posted by photon

It might help to remember that while light has no mass, it does have energy (and energy and mass are interchangeable).

I think this used to be referred to light not having a rest mass but having a relativistic mass, but I don't think they use that anymore.

That does help I agree, I am just trying to understand how gravity exerts force on a body without mass, and even momentum of an object without mass. I read a bit on Planck's constant and quanta.... it is sinking in a little. I need to read more, the brain is getting mushy.

[photon]

For gravity, I think someone already mentioned it it's not so much as gravity attracting something without mass, it's more space and time itself bend around an object with mass, so light can travel in what it thinks is a straight line but is actually a curved path.

How about this one. Take a box with two infinitely reflective mirrors, and place a photon inside so that it bounces back and forth forever. Even though that photon has no mass, it will contribute to the mass of the box!

[Cube Inmate]

Is Schrodinger's cat alive or dead?