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Age of The Universe  Time vs Space 
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#1
Feb2206, 01:57 AM

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I have long wondered about this. When light takes x number of billion years to reach earth, we judge that the star emitting the light is x number of billions years old. I cannot understand that the star would be the same age as the distance it is away from us. If I was riding a spaceship at the head of that beam of light, I would not age the same as people, i.e.time, on earth. I would, in fact, be much yonger in years than the distance in light years traveled. Is this right? If it is, then would we not have to recalulate the age of the universe using this type of equation?



#2
Feb2206, 02:33 AM

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Well your first assumption is wrong. We get light from the sun in 5 minutes but that doesn't mean the sun is 5 minutes old...



#3
Feb2206, 03:21 AM

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It's 8 minutes, Pengwuino, but you're right, there's a misunderstanding here.
Properly phrased, the concept is this: If you're looking at an object that is a billion lightyears away, you're seeing light that was emitted a billion years ago. You are, therefore, seeing the object as it was a billion years ago. The age of the object  the time since it formed  has nothing to do with it.  Warren 


#4
Feb2306, 12:38 AM

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Age of The Universe  Time vs Space
Hi Buttonpusher! Welcome to PF. Plenty of brain bending concepts are regularly tossed around here. Chroot gave a very nice answer. Hopefully, I can expand on it a bit. If you were a photon, travelling at the speed of light, your wristwatch would indicate you had traversed the distance between your home star and earth in no time flat. You would look exactly like you did the moment you began your journey, aside from some bending and stretching effects.



#5
Mar306, 12:41 PM

P: 2

I thank you people for enlightening me on this subject. I understand now that when traveling at the speed at light, I get there quicker in time while the distance traveled remains the same.
_______________ Do not worry about your difficulties in Mathematics. I can assure you mine are still greater.  Albert Einstein 


#6
Mar306, 01:31 PM

P: 308

Actually, I believe that if you're going to use the "zero time" picture of light you must also have "zero distance". Physically this should be reasonable since if no time passed you didn't go anywhere.
Speaking more geometrically, as a velocity approaches c relative to some inertial observer both the time and space axes rotate up towards the 45 degree line on a Minkowski diagram, in the limit as v approaches c all of the events in spacetime approach one single event. 


#7
Mar306, 01:56 PM

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#8
Mar306, 03:37 PM

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