Are we really alone?

[Biff]

If there is anything intelligent out there (like aliens in saucers with a propensity for sticking things up people's bottoms), then they must have a different take on the space:time continuu

Assuming that 'they' have to travel at all, and that they're not already here, everywhere, in parallel to dimension to the one(s) we claim to know and inhabit.

When the punyverse was in its infancy there were an enormous number of dimensions in existence at any one moment in time. Some of these dimensions existed for millions of years, some for a few nanoseconds. Some had ‘worm holes’ into one another. These were, in effect, cracks in what later became known (by humans) as space – time.

[smokeyging]

How’s this for a theory, Time travel, supposing in 4-500 years say the human race has been able to develop a way to get back to the past. A bit like us going back to cooks day with our bikes and pulling wheelstands up the beach when cook first arrives on a New Zealand beach . Now, wouldn’t that have old ‘cookie’ a tad concerned? It could be some school kids on a history lesson, why learn it when you can be there? We now have ships that can blow the doors off the endeavour, just think what planes could do in 500 years time. Does this make sense?

[Hitcher]

Does this make sense?

Time-travelling bikers? I'm not sure if that explains that whole anal probe thang.

[bugjuice]

Dover can...

[Winston001]

lets imagine you could travel at the speed of light, if it was dark and you switched your headlights on, would you be able to see where you were going? cause you would be going as fast as your headlights could project their light, i know this is slightly off the subject, but id be interested if anyone has an idea?

Good question but, no. The speed of light is absolute. You cannot move at the speed of light and then accelerate something to go faster. So the headlight photons wouldn't move ahead.

E=MC2 says that if you did manage to get your body up to the speed of light, you'd be pure energy and spread all over. That's essentially what Einstein meant - mass changes under acceleration into energy.

Which explains why you get that weightless feeling on a Hayabusa.

[Finn]

Good question but, no. The speed of light is absolute. You cannot move at the speed of light and then accelerate something to go faster. So the headlight photons wouldn't move ahead.

E=MC2 says that if you did manage to get your body up to the speed of light, you'd be pure energy and spread all over. That's essentially what Einstein meant - mass changes under acceleration into energy.

Which explains why you get that weightless feeling on a Hayabusa.

And then into the room walks Quantum physics. I'm sure Winston knows but for you that don't, grab a blank piece of paper and draw two dots at opposite ends of the paper. What is the shortest distance between them?

[James Deuce]

You fold the bit of paper together.

But then Schroedinger's cat dies and the universe never was.

[Winston001]

My understanding is that the closest solar system that could stand any chance of supporting humanoid life as we know it is at least 10 light years away. All sorts of funny shit happens at speeds approaching the speed of light, which means that the 20-year round trip (if they could travel at the speed of light) results in them being away from home for a significantly much longer period (Lorentz Transformation). So travelling from point A in space to point B in space, even if they can do it really quickly in the same space:time continuum, makes little sense (even if it is practicable).

True. In fact the clocks in satellites run slightly slow because of time dilation.

The answer is to use hyperspace/wormholes. People such as Stephen Hawking can demonstrate the existence of such things and plenty of people understand the physics involved. The trouble is that to create a wormhole you need two rotating black holes and since we can't even get a space shuttle to reliably work, its a wee way off before interstellar travel arrives.

[Winston001]

You fold the bit of paper together.

But then Schroedinger's cat dies and the universe never was.

Jim - I'm rather fond of cats so to save this one, I never observe it.

And your folded paper is a very nice example of cutting the space-time curve.

But even more basically, all points are connected at the quantum level. Something to do with quantum foam and zero-point energy which is way beyond me.

[Big Dave]

THE question was - 'What is six times seven?'

[vtec]

Good question but, no. The speed of light is absolute. You cannot move at the speed of light and then accelerate something to go faster. So the headlight photons wouldn't move ahead.

E=MC2 says that if you did manage to get your body up to the speed of light, you'd be pure energy and spread all over. That's essentially what Einstein meant - mass changes under acceleration into energy.

Which explains why you get that weightless feeling on a Hayabusa.

Well actually, you can't accelerate normal mass up to the speed of light, because its apparent mass becomes infinite as it gets really close to the speed of light. But again, it's all relative. Just because something is close to the speed of light does not mean that it will change into pure energy, if it collided with something else at close to the speed of light, it would turn a whole lot of it's kinetic energy into mass, and probably go bang too.

That formula (E=MC^2) only applies to high energy collisions, and fusion, and fission, and any form of mass creation or destruction.

From the perspective of the guys inside the space ship, the light would be travelling away from them at the normal rate (c), however, from a third person perspective (stationery), if they could actually see the vehicle moving at close to light speed, the light would appear to be making very little progress away from the vehicle in question, but would still be travelling at exactly the speed of light. This would mean that to the stationery person, if the people inside the spacecraft were holding a clock, it would appear to have nearly stopped.

I would have thought that this would mean that from the people's perspective on the spaceship, if the stationery person were holding a clock it would appear that their clock was going really fast, but the quote in the next paragraph seems to dispute that as far as I can understand. I think it is saying that if you can see a moving clock, it doesn't matter who is stationery or moving, as movement is all relative, just that if you can see a clock moving at close to light speed it will appear slower... even if you are the one doing the high speed and the clock is stationery? I don't quite understand this, cause I would have thought that because the clock on the spaceship is apparently slowed right down, the people on the spaceship would see a clock in the stationery frame would appear to be going nuts... I don't understand.

Here's a quote from my physics text book (Mavis is moving, and Stanley is stationery). "Think of an old fashioned pendulum clock that has one second between ticks, as measured by Mavis in the clock's rest frame. If the clock's rest frame is moving relative to Stanley, he measures a time between ticks that is longer than one second. In brief, observers measure any clock to run slow if it moves relative to them. Note that this conclusion is a direct result of the fact that the speed of light in vacuum is the same in both frames of reference." - Sears and Zemansky's University Physics with Modern Physics 11th Edition

Time dilation is relative to t=t0/sqrt(1-u^2/c^2)
^ means to the power of
u is is a constant speed relative to the rest frame
c is the speed of light
sqrt() means that you square everything in the brackets
t0 is the stationery time relative to the rest observer
t is time at speed relative to the rest observer

I'm pretty sure I've worked it out quite well, but I might have made a mistake on the explanation of t0 and t.

[Lazy7]

given enough release of energy and in a frictionless environment? - why can something go faster than the speed of light?

instead of calling it "the speed of light" just call it 300,000km's per second or whatever it is.

that way its just a number to go faster than.

back in the day people were worried that if they went faster than 30mph in an open top car - the air would rush past so fast they wouldn't be able to breathe.

then we went past the speed of sound. ooh sonic boom. wicked. but we did it. 500mph. tick

300,000km's per second cant be that far away. its just another number.

[vtec]

given enough release of energy and in a frictionless environment? - why can something go faster than the speed of light?

instead of calling it "the speed of light" just call it 300,000km's per second or whatever it is.

That's exactly how I used to think not that long ago. But there have been heaps of experiments and plenty of evidence that relative to other things, mass can not quite reach 300,000k/s.

Check out info on particle accelerators. http://en.wikipedia.org/wiki/Particle_accelerators

Particle accelerators can accelerate atomic particles up to speeds very close to the speed of light, but no matter how much energy they put into it, the particles never quite reach the speed of light, as the particles approach the speed of light, they keep absorbing that energy in momentum, but instead of it adding to the velocity portion of momentum, it (in effect) adds a lot more to the mass portion. In otherwords, (in effect) the particles gain a lot of mass, and will keep gaining mass instead of gaining velocity and exceeding the speed of light.

As a mass approaches the speed of light, its momentum approaches infinity.

Plenty of other ways to prove light speed limit

[Hitcher]

Sears and Zemansky's University Physics with Modern Physics 11th Edition.

Is this text still used? I've got a copy at home somewhere, probably on a shelf between Hymns Ancient & Modern (Revised) and The Little Red Schoolbook, or Bullshit & Jellybeans.

[Winston001]

Is this text still used? I've got a copy at home somewhere, probably on a shelf between Hymns Ancient & Modern (Revised) and The Little Red Schoolbook, or Bullshit & Jellybeans.

The Little Red Schoolbook - now there is a blast from the past. I never did see it because it was banned as I recall. As was "Thoughts of Chairman Mao".