t00fri wrote:Why in 0 time???
The speed of light is 300000km/sec.
Correspondingly, light often takes millions of years to reach your eye after being emitted on a far away galaxy.
It's true that, as we measure it, it takes light 13 billion years to reach us from distant quasars. But from the point of view of the photon that makes the journey, it has taken no time at all. If a photon carried a watch, it wouldn't tick. This is 'time dilation' - clocks in different reference frames tick at different rates - and it works at all speeds. (I know I'm teaching my grandmother to suck eggs here - but I thought it would be useful to spell it out.
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The difference in the rate at which time passes in a moving frame (t1) compared with one at rest (t0) is given by:
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t1 = t0/gamma
where gamma = 1/sqrt(1 - v^2/c^2)
where v is the speed of the moving frame and c is the speed of light(By the way - by 'frame' I just mean space as measured by a particular observer. E.g. when on a train, you measure distances such as the distance to the buffet in relation to the carriage. It would be daft to use the station platform as your point of reference. A moving train carriage is a differnt 'frame' from a station platform.)
If we travel to Mars at 99% of the speed of light, then as measured by someone on Earth, we would take about 15 mins to get there (with the planets in their current positions). But from the equation above, we can work out that our own watches would show that only about 2 mins had elapsed. If we travelled at 99.9% of the speed of light then, according to our watches, only 40 secs would have passed.
t00fri wrote: Since you have a /non-zero mass/ it would take an /infinite/ amount of energy to accelerate your body to the speed of the light beam on which you proposed to travel.
So in the future, you better take a car or a plane...
Fortunately, we travel by Celestia, so our rest mass is zero.
It would be possible to implement a 'special relativity' mode in Celestia where-by we can increase our speed only upto the speed of light (or just below it). We could have two clocks displayed. One showing the time according to our watch and one showing the time on Earth.
How cool would that be?
Incidentally, special relativity will be 100 years old next year - it would be nice to celebrate the fact somehow with Celestia.
StarCrazy wrote: Is gravity the only thing that can affect light so drastically? Always went for the underdogs, myself. Please correct me in any way...just trying to filter out myths from my mind and have a greater understanding in things.
In a way, gravity affects light only indirectly. What gravity does is change the shape of spacetime. Light follows the most direct paths through spacetime - lines that are, essentially, the shortest path between two points. If there is a lot of gravity around, then the most direct path for light might be a curve. This is a bit like travelling on the surface of Earth. If there is a hill in the way, the most direct path between two points might be a curve. In a black hole, spacetime is bent so much that the direct paths that light follows are closed loops.
StarCrazy wrote:I understand that greater mass creates greater gravitational forces, but essentially gravity is weak.
Gravity is indeed very, very weak. My favourite demonstration of just how weak it is works like this: Place a paperclip on a table. Hold a small magnet above the paperclip and it leaps off the table. Now, think of this as a tug of war between gravity and electromagnetism. The entire Earth is pulling the paperclip in one direction (down), yet it is beaten by one tiny magnet pulling the paperclip in the other direction (up).
The thing that distinguishes gravity from other forces is that it there is only one type of it (only one 'charge'). Everything is attractive - the more stuff you have, the more force you have and we feel the attraction through the whole of space. This is not true of electromagnetism. You can have lots and lots of electric charge but if half of it is positive and the other half negative then the long-range effect is nil.
So our magnet would have no (magnetic) effect on a similar magnet on the Moon, but the force of attraction of our paperclip (small as it is) extends to the the Moon, the Sun, the other stars of the Milky Way, the Local Group, etc.
Adam
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at least 1/2 of them have trouble subtracting fractions from whole numbers. I kid you NOT! Although Algebra 1 is a prerequisite for my course, higher math is not well taught to kids or applied in examples by many high school teachers, and the formulas and transformations present in relativity topics I would have to present would be stretching it a bit for at least 50% of my students, without a lot of remedial math. I don't have the time to do both.
...thanks for the wonderful refresher course and demonstrations.