The expanding universe
24 March 2005, 01:18 AM
#32
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ALthough I think my wife might be able to travel in time. It seems she can leave the house with my credit cards at about 9.00 on a Saturday morning and get in a full 9 hours of shopping before the shops close at 5.00 
24 March 2005, 04:14 AM
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24 March 2005, 07:44 AM
#35
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may be someone has travelled in time but we don't know about it? 
i think it's in our nature to think everything has some sort of measure or is finite, it could be possible that the universe didn't 'start' at any particular point in time...imagine a graph with the y axis showing time and the x axis showing expansion of the universe. i think of it as the graph being a curve where no specific point on the that curve (same principle as a circle) could be labelled as being the the 'start', there's no beginning or end to a circle.
i think it's in our nature to think everything has some sort of measure or is finite, it could be possible that the universe didn't 'start' at any particular point in time...imagine a graph with the y axis showing time and the x axis showing expansion of the universe. i think of it as the graph being a curve where no specific point on the that curve (same principle as a circle) could be labelled as being the the 'start', there's no beginning or end to a circle.
24 March 2005, 08:38 AM
#36
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The future would have to have happened for you to travel to it. If that is so, it would be history.
So we will never be able to do it or someone in the future would have came back in time by now.
Simple enough logic.
So we will never be able to do it or someone in the future would have came back in time by now.
Simple enough logic.
24 March 2005, 08:43 AM
#37
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Originally Posted by fast bloke
guys - you need to do a lot more reading. Have a google for event horizons and escape velocities to understand black holes, white holes and ever expanding universes.
For the original question, the problem with the question is that you are trying to understand the answer based on the 4 dimension that we can understand (3 normal space dimensions and time) All of these dimensions are merely a measure of our universe, so anything that happened 'before' out universe existed cannot be explained using these 4 dimensions. To put this in perspective - imagine we gave the ancient greeks a scoob and asked them to measure BHP at the crank. The tools they had available would have been a ruler and a graduated candle. Now - how do you measure (or explain) BHP using a ruler and a candle?? you can't. You need to understand new technologies (and possibly dimensions) to do this. We do not currently have the tools or the understanding to measure or explain the universe. The main problem is that it must expand at the speed of light (anything less and it would have collapsed at the same instant that it was formed) Say there is a 'centre' of the universe, and we are for the sake of arguement, 1 light year from this centre. Also work on the assumption that the big bang happened 100 light years ago. Some of the light that was emmited from the big bang 100 light years ago is now 101 light years away. IN another 100 light years it will be 201 light years away. The only way we can ever see it is to travel faster than light. If we travelled faster than light, we would catch up with the light that was here previously. That would be time travel. We can work on the assumption that if time travel was ever going to be invented at any point in the future, then it would have already been invented, as future time travellers would surely try to abuse the power of time travel for personal gain. Given that time travel doesn't currently exist, then it will never exist, so no-one ever figures out how to travel faster than light, then we will never see the bit of the universe that is moving away at the same rate that the light it is emmitting is moving towards us
now - more beer
For the original question, the problem with the question is that you are trying to understand the answer based on the 4 dimension that we can understand (3 normal space dimensions and time) All of these dimensions are merely a measure of our universe, so anything that happened 'before' out universe existed cannot be explained using these 4 dimensions. To put this in perspective - imagine we gave the ancient greeks a scoob and asked them to measure BHP at the crank. The tools they had available would have been a ruler and a graduated candle. Now - how do you measure (or explain) BHP using a ruler and a candle?? you can't. You need to understand new technologies (and possibly dimensions) to do this. We do not currently have the tools or the understanding to measure or explain the universe. The main problem is that it must expand at the speed of light (anything less and it would have collapsed at the same instant that it was formed) Say there is a 'centre' of the universe, and we are for the sake of arguement, 1 light year from this centre. Also work on the assumption that the big bang happened 100 light years ago. Some of the light that was emmited from the big bang 100 light years ago is now 101 light years away. IN another 100 light years it will be 201 light years away. The only way we can ever see it is to travel faster than light. If we travelled faster than light, we would catch up with the light that was here previously. That would be time travel. We can work on the assumption that if time travel was ever going to be invented at any point in the future, then it would have already been invented, as future time travellers would surely try to abuse the power of time travel for personal gain. Given that time travel doesn't currently exist, then it will never exist, so no-one ever figures out how to travel faster than light, then we will never see the bit of the universe that is moving away at the same rate that the light it is emmitting is moving towards us
now - more beer
you are aware that a light year is a distance and not a measure of time yeah??
24 March 2005, 08:44 AM
#38
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oh yeah going back to the approaching light theory... to approach that kind of speed, your mass would need to be zero according to one of the theories... however a photon can do it and that has a mass of >0 .
Faster however is a different story.
Faster however is a different story.
24 March 2005, 08:45 AM
#39
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Originally Posted by Brendan Hughes
It's nicely explained in Bryson's Short History of Nearly Everything.
Someone's nicked me copy though, so I can't tell you which page numbers...
Someone's nicked me copy though, so I can't tell you which page numbers...
24 March 2005, 08:48 AM
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Originally Posted by paul-s
it hasnt been tested, but if time travel were possible someone would have come back already, therefore altering the sequence of events from that point onwards causing the point in the future that this person came back at to not exist in this alternate time, therefore causing everything to cease being
theres no law that says there can only be one universe with a set time and shape, if someone has travelled back and changed something, although we will not experience it, they will from what they create.
The best way to picture it is like a comic book strip.... moving from left to right, then just add an alternate line underneath with the same constant time but a different occurance of events
24 March 2005, 08:53 AM
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Only real way to understand this stuff is to visit your local friendly shaman and take a dose of peyote or preferably ayawaska.
http://www.shamanspirit.net/ayawaska.htm
Then you will see we are one big simulation and god is one scary ****.
http://www.shamanspirit.net/ayawaska.htm
Then you will see we are one big simulation and god is one scary ****.
24 March 2005, 09:08 AM
#44
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Originally Posted by suprabeast
nothing can have zero mass or it would not exist
24 March 2005, 09:36 AM
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The big problem we have here is that we are trying to describe complex physics concepts that don't translate from mathematical formulae to the English language very well.
I have read a little on QM and the early universe and I don't for a moment admit that I understand anything but the most basic of concepts. There are people out there that know an awful lot more about it that I will ever know and I am happy to accept they are far closer to understanding these questions than probably any of us. I also accept that they do not know all the answers (yet) and that I almost certainly never will.
But none of that causes me any great concern, I accept things as they are, and accept my own limitations. I don't see the need to resort to the creation of a supernatural being to explain the creation of the universe, that solves nothing, it just moves the same questions 1 step back and modifies the paradox of "what created the universe?", which we know exists to "what created god?" for which we have no proof of existence at all.
I have read a little on QM and the early universe and I don't for a moment admit that I understand anything but the most basic of concepts. There are people out there that know an awful lot more about it that I will ever know and I am happy to accept they are far closer to understanding these questions than probably any of us. I also accept that they do not know all the answers (yet) and that I almost certainly never will.
But none of that causes me any great concern, I accept things as they are, and accept my own limitations. I don't see the need to resort to the creation of a supernatural being to explain the creation of the universe, that solves nothing, it just moves the same questions 1 step back and modifies the paradox of "what created the universe?", which we know exists to "what created god?" for which we have no proof of existence at all.
Last edited by OllyK; 24 March 2005 at 09:42 AM.
24 March 2005, 10:03 AM
#48
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Sorry, i wasn't being very specific.
photons have energetic mass, but zero rest mass, or rather, intrinsic mass.
einstein's theories only allow objects with zero rest mass to move at c
photons have energetic mass, but zero rest mass, or rather, intrinsic mass.
einstein's theories only allow objects with zero rest mass to move at c
24 March 2005, 10:16 AM
#52
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Originally Posted by paul-s
it hasnt been tested, but if time travel were possible someone would have come back already, therefore altering the sequence of events from that point onwards causing the point in the future that this person came back at to not exist in this alternate time, therefore causing everything to cease being
24 March 2005, 10:16 AM
#53
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Originally Posted by TelBoy
That's 99% of us lost then 
24 March 2005, 10:16 AM
#54
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Originally Posted by suprabeast
do you consider light to be the ultimate speed?? and do any of the theories cater for any speeds faster than light??
Originally Posted by http://en.wikipedia.org/wiki/Light_speed
The speed of light (denoted as c, reputedly from the Latin celeritas, "speed", and also known as Einstein's constant) in a vacuum is exactly equal to 299,792,458 metres per second (approximately 186,282.4 miles per second). The carrier particle of light is the photon. This exact speed is a definition, not a measurement, as the metre is defined in terms of the speed of light and the second. The speed of light through a medium (that is, not in vacuum) is less than c (defining the refractive index of the medium). "Speed of light" is sometimes abbreviated SOL.
24 March 2005, 10:18 AM
#55
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What happens if you have a space ship travelling at the speed of light, then turn on a lightbulb inside it?
Does that mean that the light inside is travelling at faster than the speed of light?
Does that mean that the light inside is travelling at faster than the speed of light?
24 March 2005, 10:19 AM
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Originally Posted by Iain Young
What happens if you have a space ship travelling at the speed of light, then turn on a lightbulb inside it?
Does that mean that the light inside is travelling at faster than the speed of light?
Does that mean that the light inside is travelling at faster than the speed of light?
24 March 2005, 10:20 AM
#57
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Originally Posted by suprabeast
do you consider light to be the ultimate speed?? and do any of the theories cater for any speeds faster than light??
24 March 2005, 10:22 AM
#58
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Originally Posted by OllyK
Relativity!
24 March 2005, 10:25 AM
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Originally Posted by OllyK
Relativity!
or something like that
24 March 2005, 10:26 AM
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Originally Posted by Iain Young
Ok, so what happens if you then open the door. The photons inside the ship are travelling at twice the speed of light (the speed of the ship + the speed of the photons inside it). When you open the door and the photons escape, is there an instant decelleration to same velocity as the ship, or do those photons actually travel faster than the speed of light once they have left the safety of the ship?