Friday conumdrum with DDD - The twin paradox, help!

Kieran_Burns

DonDaddyD wrote:

IDIC?

I'm shocked. I truly am. :shock:

Boy Lard

I remember reading a book called Einstein for Dummies or something like that which explained the whole concept of 'frames of reference' which I understood. There again, I did physics at Uni and have a pretty good understanding of these things anyway, so I'm not sure of the book was that good.

Imagine there is a train with a laser on it......

....actually trains with lasers on sounds more fun than relativity.

greg66_tri_v2.0

Kieran_Burns wrote:

DonDaddyD wrote:

IDIC?

I'm shocked. I truly am. :shock:

+1. I have only a modest interest in the Trek, and I had that one instantly.

DDD, perhaps you need to consider evening classes.

tailwindhome

DesWeller wrote:

It's worth point out that there are probably only a few thousand people on the planet who genuinely understand Einstein's Special and General Theories of Relativity. .

I have a theory that in all walks of life, when 'stuff' gets to a certain level of complexity people just start making sh1t up.

DonDaddyD

You two are showing your age. You probably first ecountered the IDIC in the original series. I wasn't even born then.

My core trek knowledge stems from the Next Generation (pun intended) and that was all about Klingons, Cardassians, Q and the Borg!

Now I can tell you about Kahless, the Prophets, Omega particles and the Borg Queen. But Vulcan's they're not cool.

Will Snow

mkirby wrote:

g00se wrote:

Now, nothing can go faster that the speed of light.

Thats not strictly true, light itself can go faster then c when passed through the correct medium.

Inncorrect. c is the speed of light in a vacumn, and nothing can go faster than it. You can get light to go faster than the speed of light in a material, giving rise to cherinkov radiation and all that jazz, but that is not c.

With regards to the original twin paradox, the paradox isnt that one ages more than the other. The paradox is that when you work out the time dilation from observer a and observer b's inertial frames of reference then according to eachother, both have aged two separate amounts, i.e. observer a has watched for 4 years and sees b as 40 years older, but from observers b's frame of reference he has been watching for 4 years and observer a has aged 40 years. That is the actual paradox, however if you sit down and work out the mathematics of acceleration and deceleration that such a trip would involve, then it all works out quite nicely and the paradox disapears

Will Snow

also speed dependent mass is a lazy way of working with relativity, and not correct.

Zachariah

The twin paradox has been observed in reality - they took two ultra-accurate atomic clocks, put one on the space shuttle and let it run around in orbit while the other one stayed on earth.

Result - The one that stayed on earth was ahead of the other one by a detectable amount, ie it had experienced more time than its space borne twin.

Here's yet another analogy:

Imagine you are filming your life. But you don't have fancy digital cameras, you have old-style film reels that come in those big round metal canisters (hence 'in the can').

You share your film with your twin, who is standing next to you. Imagine you are constantly spooling out new film to him at 24 frames a second. Even though he's right next to you, he only looks at the tape. Neither of you are moving, so the film runs at normal speed. He can see the film at the same speed you do.

Now imagine your twin gets in a car and drives away. He's still watching the film, and you're still spooling it out at 24 frames a second.

But he's moving away at a decent pace. The spool can't quite keep up. To him, the framerate drops to 20 a second. Your life appears to be going slower than before, though you are still standing there, spooling it out at the same speed.

If your twin puts his foot down, he can get up to a speed that matches the framerate. It now looks to him as if your film has frozen, because he's moving at the same speed as the camera can churn out pictures. If he goes any faster, he'll outpace the film and break the tape.

Meanwhile, you don't notice any change in your own life.

Will Snow

Zachariah wrote:

The twin paradox has been observed in reality - they took two ultra-accurate atomic clocks, put one on the space shuttle and let it run around in orbit while the other one stayed on earth.

Result - The one that stayed on earth was ahead of the other one by a detectable amount, ie it had experienced more time than its space borne twin.

Again, thats not the paradox. There isnt anything even vaguely paradoxical about that

Monkeypump

I don't get it. Will tune in next week for the next conundrum...

(and I actually quite like Vulcans).

cee

Kieran_Burns wrote:

No. You have to start looknig at the concept of spacetime (the old rubber sheet analogy)

oh no...not the old rubber sheet analogy!

I stopped that when I was a young child.....

Kieran_Burns

cee wrote:

Kieran_Burns wrote:

No. You have to start looknig at the concept of spacetime (the old rubber sheet analogy)

oh no...not the old rubber sheet analogy!

I stopped that when I was a young child.....

some people start when they're an adult... less said the better :shock:

Oddjob62

Zachariah wrote:

The twin paradox has been observed in reality - they took two ultra-accurate atomic clocks, put one on the space shuttle and let it run around in orbit while the other one stayed on earth.

Result - The one that stayed on earth was ahead of the other one by a detectable amount, ie it had experienced more time than its space borne twin.

I thought these experiments always showed that the clock at higher altitide was ahead, due to gravitational time dilation being a more significant factor

Zachariah

Gravitational potential did play a significant part in the Hafele-Keating experiment, and was taken into account. I can't find anything detailing the space-based experiment (someone might be able to decipher this, I certainly can't).

Big Wib

g00se wrote:

OK - this is a good description of what you're talking about. I heard it a few months ago.

Time is the forth dimension and we're travelling through it. We can't 'see' the forth dimension but we experience travelling through it as time.

Ah, so it's a Scottish thing

[I'll get my coat]

Big Wib

mr_poll wrote:

"Time?
Time is an illusion - lunchtime doubly so".

- Ford Prefect

Doesn't help matters I just love the quote.

Readers Digest has a section for people like you

Bassjunkieuk

DonDaddyD wrote:

You two are showing your age. You probably first ecountered the IDIC in the original series. I wasn't even born then.

My core trek knowledge stems from the Next Generation (pun intended) and that was all about Klingons, Cardassians, Q and the Borg!

Now I can tell you about Kahless, the Prophets, Omega particles and the Borg Queen. But Vulcan's they're not cool.

I think both of them appeared in DS9 :-) Unless you meant everything after TNG, in which case we're both in the same camp as I never watched TOS.

I started reading this as a "wind down" at the end of a day of reading about Dell Blade Servers. My head now hurts more.

TGIF.

PBo

Boy Lard wrote:

I remember reading a book called Einstein for Dummies or something like that which explained the whole concept of 'frames of reference' which I understood. There again, I did physics at Uni and have a pretty good understanding of these things anyway, so I'm not sure of the book was that good.

Imagine there is a train with a laser on it......

....actually trains with lasers on sounds more fun than relativity.

you were just about to do Einstein's thought experiment weren't you?

bunter

http://www.youtube.com/watch?v=JkxieS-6WuA

the thing I have trouble with is the speed of light being constant no matter how fast you travel relative to it. I can never square that with things like red/blue shift.

antontordy

I only understand time in 2 ways:

1) In terms of the Earth moving around the Sun (clocks, sundials etc)

2) In terms of biological time (ageing process, cell division etc)

I can imagine that gravity can affect the orbit of a planet around a star and thus affect time (1)

But how can gravity or space travel affect biological time which after all must keep to a constant rythm in order to keep the organism alive?

Will Snow

because relative to you, time does not change. From you looking outwards, time would be slowed down, and people looking in on you time would be sped up. Time is relative to your frame of reference. As is length, and various other things

antontordy

So if you and I were aged 20 and you got in a spaceship and travelled at the speed of light for 50 years around the Universe what would your age be in relation to mine when you got back?

Will Snow

you cant go at the speed of light. at near light speed then you would end up younger. The paradox arises from the calculations, which ive been over earlier in the thread. Time is relative

antontordy

But surely this is not biologically possible?. Does this not suggest therefore that this theory is not possible in real life?

Will Snow

it has been observed. It is what happens. The hard part of relativity is getting your head around it. Well, that and the Lorentz transformations.

antontordy

Interesting! - but they don't appear to address the biological paradox - thanks all the same.

Will Snow

what biological paradox? Your cells would age, split and die at the same rate relative to you... but not to everyone else. There isnt a clock at the middle of the universe keeping the 'real time'. Time varies from place to place

antontordy

What about the clock on planet Earth when one gets back? Does this not indicate that the theory is not possible biologically?

Will Snow

again its not a theory. Time has moved differently for the chap on the spaceship, that is observable fact. Time is not a constant thing.

antontordy

I can see that time does indeed change depending on gravity and speed of travel but what we observe is only tiny fluctualtions which the biological clock can cope with. But the faster we go the greater the loss of syncopation between biological time and planetary time. This is ok whilst we can't travel very fast.......