I have to write an essay about speed of light and i have to prove either that the speed of light actually isnt constant, or that it is constant and time travel is possible. But i dont really get what time travel has anything to do with it. also i really dont get speed of light in general. why is it constant?
2007-12-14 23:48:35 · 10 answers · asked by jbdrummergirl93 2 in Science & Mathematics ➔ Physics
It's pretty understandable not to get the speed of light.
The importance of the concept has to do with relative velocities. If you can throw a ball at 50 mph, then if you throw a ball forward from a truck that's also moving 50 mph, then the ball's net speed should be 100 mph relative to an observer standing at the side of the road. The two speeds add together.
The same principle should seem to apply to light. If light is emitted from a moving object, the net speed should be the sum of the speeds of the two objects. That means the speed of light also depends on the speed of the object that emitted the light. You don't mention what grade level this essay is for, but just going this far and saying light isn't constant would probably show enough knowledge of physics to get a decent grade on your essay - after all, Nobel award winning physicists came to the same conclusion for years.
Except when they finally figured out a way to test this in an experiment (Mickelson-Morley experiment), the principle proved to be false. The speed of light is constant regardless of the motion of the object emitting the light.
If a flashlight is going almost the speed of light and emits light at the speed of light (naturally), the observed speed is the same regardless of the viewpoint - the person holding the flashlight sees the light move at the same speed as some observer that's standing still.
That creates a whole lot of problems with the normal ideas of physics and led to Einstein's Theory of Relativity. Namely, that the speed of light is the ONLY thing that stays constant. That means time doesn't move at a constant rate for two different observers. That means that the distance between two objects isn't necessarily the same for two different observers.
That doesn't mean that time travel is possible, though.
To travel in time, you'd have to travel faster than the speed of light and then could observe things directly that have already happened. In other words, you could rewind and reobserve, but you couldn't actually go back in time and be part of the scene.
The other problem with time travel is that it's impossible to go faster than the speed of light. As you speed up, time slows down and distances become smaller. Once you reached the speed of light, time would stand still for you (even though it's still moving for the rest of us that moving at mere mortal speeds). If you continued accelerating, you'd obviously be going faster than the speed of light when the next second clicks on your clock, except the next click would never come.
2007-12-15 00:16:20 · answer #1 · answered by Bob G 6 · 1⤊ 1⤋
In Genesis 1:3, it talks about the Big Bang-- God said it and bang, there it was. Here God created all of the matter and energy that makes up our universe, and He did it with His Word (John 1:1-13). Science also tells us that the universe is expanding, and not only that, the expansion is also accelerating with time. This is more evidence that our universe had a beginning. Also the Hubble Space Telescope has detected galaxies as far as 46 billion light years away in either direction, and there is still no end in sight. Whether you are a traditional evolutionist who believes that the universe is 15 billion years old or a young earth creationist who believes the earth is about 6000 years old, the conclusion is the same. This means that the expansion of the universe (or the expansion of space and time) is occurring at a speed much much greater than the speed of light. Even though it might take us billions of years to reach a distant galaxy, that doesn't mean that it took the light from there that long to get to us. So, for your information, the Bible is not in conflict with observable science.
2016-05-24 01:30:55 · answer #2 · answered by ? 3 · 0⤊ 0⤋
The speed of light (in a vacuum, like space) is the fastest speed in the universe. It is not constant as the speed of light is much slower when passing through materials (like water), but when people refer to the speed of light they are refering to the speed of light in a vacuum. Nothing can be faster than it. OK
Now for time travel. it's a trcky concept. let's start by clearing this up. you can not go back in time.
you can go "forward in time" however.
Alright here is how you do it.
1. you must go in a rocket and travel at nearly the speed of light for some amount of time measured by your onboard clock (say 5 years)
2. rendevous with earth and land safely
3. When you get out you will realise that the earth has progressed and experienced 70+ years while you were gone.
This is because the closer you go to the speed of light, the slower time is for you.
While this is technically travelling forward in time, this is very impractical as your speed increases to the speed of light, the amount of energy required to go that speed gets closer and closer to infinity, accompanied by several other weird phenomena.
P.S. : the speed of light in a vacuum is 299 792 458 m / s
meaning light travels 9.4605284 × 10^15 meters in a year, or 1 lightyear.
hope this helps
good luck!
2007-12-15 05:08:02 · answer #3 · answered by Supreme Overlord 2 · 0⤊ 0⤋
Others have already answered on the speed of light. For your essay, what needs explaining is that the speed of light is constant for all observers in different moving frames of reference. People moving 10,000 mph will get the same answer as someone stationary. They will NOT see the difference in speeds.
Common everyday observation: people on those walkways in airports move faster than normal. However, from their viewpoint, they only are moving as fast as they walk. From Joe Photographer's point of view, they are walking as fast as their walking speed + speed of the wallkway.
However, if both measure the speed of light, again, they both will get the same answer, c = 299,792,458 meters per second...
Time travel: if it were possible, you have already been back in the past, and have already changed or done whatever you were going to do. So time travel (at least as far as we know) to the past is a waste of time, because you couldn't change it because you already have.
Time travel, one way into the future is totally possible if you can go fast enough. The strange thing about the speed of light being constant for everyone measuring it, no matter how fast that observer moves, is that as you get moving closer and closer to the speed of light, time slows down (time dilation). However, it does NOT appear to slow down for you, the close-to-light-speed-journeyer, or for the stationary observer. But it DOES slow down for you. Thus 10 million years could pass on Earth, and it would be a mere second for someone going 99.9999999% the speed of light.
And since Einstein is the one who figured this all out, now you know why he is regarded as such a genius.
2007-12-15 01:16:03 · answer #4 · answered by Charles M 6 · 0⤊ 0⤋
Light is energy. Energy radiates from a source in whatever direction its creating forces it. Light is constant leaving from any energy source, though its strength can fluctuate with the strength of a light source.
Take a sonic boom from a jet. It is created in the sky as the jet reaches the speed of sound. Yet you see the jet well before the sound is made. That's because the light is faster than sound so you can see the plane's reflections and color in the sky first.
Ever watch a water balloon splash against a wall or sidewalk? See how the pattern is all over the place. Imagine the balloon is light from the sun. The water needed time to go from the explosion to the sidewalk, especially the farther distances. The sun's light is the same way. Each light particle is not instantaneous. It just seems that way to the naked eye.
Imagine a baseball pitcher pitching a fastball. The ball starts out strong but fades a bit at the plate. It's the same principle with light at the sun, only it's a plethora of pitchers trying to pitch to everything in sight. Each ray of light shoots in any direction from the sun to space. It actually takes about nine minutes for a particle moving at the speed of light to go from the sun to Earth.
2007-12-15 00:08:13 · answer #5 · answered by Your Uncle Dodge! 7 · 0⤊ 3⤋
the speed of light certainly isnt constant, it is A constant, but can actually travel way below the maximum. Light travels slower thru denser medium... which is where that Cherenkov radiation comes from... if you send a beam of say... high energy electrons at just under the speed of light IN A VACUUM into a dense medium like water or glass, the electrons may actually travel Faster-Than-Light... at lease faster than light will in that medium and there is that funny blue Cherenkov radiation emited.
2007-12-14 23:59:45 · answer #6 · answered by Faesson 7 · 0⤊ 1⤋
The speed of light is the speed at which electromagnetic waves can move in a vacuum: 299,792,458 meters/sec (186,000 miles/second). According to Einstein's Theory of Relativity, nothing can go faster than the speed of light.
Light is slowed down in transparent media such as air, water and glass
2007-12-14 23:56:06 · answer #7 · answered by Eviex 1 · 1⤊ 0⤋
It's not constant.
The speed of light in a PURE vacuum is constant.
That's why we're been telling our lasers
ever since the Physics cranks invented
Special Relativity, that the only thing
constant about a vacuum is
trains and morons.
2007-12-15 00:27:03 · answer #8 · answered by Anonymous · 0⤊ 2⤋
http://en.wikipedia.org/wiki/Theory_of_relativity
Follow the link above for a clear understanding.
2007-12-14 23:59:32 · answer #9 · answered by mark B 1 · 2⤊ 0⤋
2.998^8 m/s. Its particles are photons which have no mass.
2007-12-15 01:58:26 · answer #10 · answered by Anonymous · 0⤊ 0⤋