What is time

[TimbaLanD]

Thanks guys for all your comments. I am a little confused with twin paradox. The only way it makes sense (to me) is by imposing speed to time. As I understand it, time slows down as we get close to C. Therefore the speed of time somehow is slowing down(?). Say if I am standing on earth and I see a rocket passing by at C with a passenger inside, do I see the passenger’s actions in slow motion? Will the passenger see my actions in fast motion? This is why I am keep going on about time having a speed, else it makes no sense to me.

 

Another thing that confuses the daylight out of me is the speed of light. If I am at the back of a bus that travels at 10mph and I start walking from the back to the front of the bus at 2mph, my speed relative to the ground is 12mph. What if the bus is travelling at C and I do the same, why will I not be travelling at C+2mph? If I do, surely I have exceeded the speed of C.

[swansont]

Thanks guys for all your comments. I am a little confused with twin paradox. The only way it makes sense (to me) is by imposing speed to time. As I understand it, time slows down as we get close to C. Therefore the speed of time somehow is slowing down(?). Say if I am standing on earth and I see a rocket passing by at C with a passenger inside, do I see the passenger’s actions in slow motion? Will the passenger see my actions in fast motion? This is why I am keep going on about time having a speed, else it makes no sense to me.

 

Time slows down for the other guy as he gets close to c; your clock never appears to change. In inertial frames, we will never agree who is right. Anything you see in slow motion has to also be viewed in slow motion by the other observer.

 

Another thing that confuses the daylight out of me is the speed of light. If I am at the back of a bus that travels at 10mph and I start walking from the back to the front of the bus at 2mph, my speed relative to the ground is 12mph. What if the bus is travelling at C and I do the same, why will I not be travelling at C+2mph? If I do, surely I have exceeded the speed of C.

 

Speeds do not add linearly, it's just that we don't notice this very much at speeds we are used to seeing in everyday occurrences.

[ashennell]

If I am at the back of a bus that travels at 10mph and I start walking from the back to the front of the bus at 2mph, my speed relative to the ground is 12mph. What if the bus is travelling at C and I do the same, why will I not be travelling at C+2mph? If I do, surely I have exceeded the speed of C.

 

I'm not an expert on this so perhaps someone can correct me. I'm just interested to see if a can actually get something right regarding speed of light stuff.

 

If the bus is travelling at the speed of light then you would experience no passage of time if you are in the bus. Therefore you could not move forward - there would be no time for you to move forward in.

 

This may be very wrong!

 

Edit: Looks like I was wrong then.

[TimbaLanD]

Time slows down for the other guy as he gets close to c; your clock never appears to change. In inertial frames' date=' we will never agree who is right. Anything you see in slow motion has to also be viewed in slow motion by the other observer.

 

I am lost!!

 

Speeds do not add linearly, it's just that we don't notice this very much at speeds we are used to seeing in everyday occurrences.[/quote']

 

So, does this mean, if i switch on the light bulb inside the bus, it will not shine?

[TimbaLanD]

If the bus is travelling at the speed of light then you would experience no passage of time if you are in the bus. Therefore you could not move forward there would be no time for you to move forward in.

 

NO time? now i am totally confused!

[ashennell]

I think my answer is possibly wrong.

Im not a physicist.

 

I was under the impression that time 'stopped' if you travel at the speed of light. i.e -

Time slows down for the other guy as he gets close to c

 

If my interpretation is correct then when your bus reaches c everything freezes - you would not be able to turn the light on. If you could still see anything then I guess it would be a frozen image.

 

There are normally millions of physics experts around here so im sure one could set us all right.

[swansont]

Massive bodies can't travel at c, so it's a moot point. Nobody can state with any scientific basis what would happen.

[swansont]

So, does this mean, if i switch on the light bulb inside the bus, it will not shine?

 

The bus can't be travelling at c with respect to any other massive object. Yes, the light will shine. As far as any rider on the bus is concerned, with respect to the laws of physics the bus is at rest and the rest of the universe is whizzing by.

[ashennell]

So I was wrong then.

 

I think I could spend a whole light year trying to get my head round this stuff and still not figure it out

[TimbaLanD]

Massive bodies can't travel at c, so it's a moot point. Nobody can state with any scientific basis what would happen.

 

This may sound really stupid, but why cant massive bodies travel fast? I am sure Newton’s law states that an object travelling on a straight line will continue to do so until an external force acts up on it.

 

So, why can’t we travel at high speed in space? Maybe I have been watching too much voyager but I am trying to understand the basics.

[swansont]

This may sound really stupid' date=' but why cant massive bodies travel fast? I am sure Newton’s law states that an object travelling on a straight line will continue to do so until an external force acts up on it.

 

So, why can’t we travel at high speed in space? Maybe I have been watching too much voyager but I am trying to understand the basics.[/quote']

 

It's one of the consequences of relativity. Your momentum isn't a linear function of speed as Newtonian mechanics predicts, so a given force causes an increasingly smaller acceleration as your momentum gets larger. From another standpoint, traveling at c would require infinite energy.

[TimbaLanD]

It's one of the consequences of relativity. Your momentum isn't a linear function of speed as Newtonian mechanics predicts, so a given force causes an increasingly smaller acceleration as your momentum gets larger. From another standpoint, traveling at c would require infinite energy.

 

I see... that is hard to grasp but I think I should polish up on “relativity theory”. I do find it hard to understand.