After turning around and spending another 4 hours at that speed to return to Earth, you'd find that 2 years will have passed on Earth. This question has already been answered, but I'll try to answer it in a slightly different way. A lot of time has passed on the Earth, but since I was traveling so fast, I only experienced a few years passing. Kimetic energy is (m*v2 )/2, so any velocity requires 0 energy. To Mary, she feels like she’s a year older than when she left. The only time machines around today are telescopes that let us see deep into the universe’s past. For Bill, the ball is moving much faster than it is for Mary. He called it relativity. At this point, remember back to how the speed of the ping pong ball on the train was determined by what was relevant to the person looking at it. The record of the history of the universe is before our eyes to see and decipher. When we look out of our galaxy and look at other galaxies this lets us see even further back in time as light from other galaxies have traveled millions or billions of years to reach our telescopes. If you were talking to someone manning a spotlight on the ship and you both counted from 3 to 0 and then your covert on the ship turns on the spotlight, it would appear to you on land, that the light was turned on exactly when your counterpart said he turned the light on. Good question. I hope this chapter has helped you in understanding how light travels, the speed of light and time dilation. I know it sounds weird but just follow me because we need it to be that way but it doesn’t have much to do with what we’ll be talking about. I always thought it was the opposite...that is very interesting. Ask a science question, get a science answer. Time dilation is a difference in the elapsed time measured by two clocks, either due to them having a velocity relative to each other, or by there being a gravitational potential difference between their locations. Someone living on the top of a mountain would age faster than someone living at the base of the mountain, even though the time would be minisule. Cookies help us deliver our Services. By seeing further and further into the universe, we are looking further and further back into the Universe’s 13.7 billion year past. As measured by yourself, your journey is a much shorter distance and takes 1/70th of a year (about 5 days), and all your biological processes are normal. By using our Services or clicking I agree, you agree to our use of cookies. Time always seems to be passing at the same rate for everyone everywhere. do your bodycells also slow down aging? As far as how far in miles that is, yea right. Light travels so fast that from any distance we can see on the Earth, light travels to it in trillionths of a second which happens so fast we can’t notice the time it took to travel. Time feels like it’s passing at the same rate at every speed. The same is true when we look at a star such as Sirius, a bright star located only 8 light years away or 8 x 6 trillion miles, so its light has traveled 48 trillion miles, taking 8 years to reach us. With telescopes, we can watch events that happened 100’s, 1,000’s, millions and billions of years ago. All we can ever accept or understand of a number this large is that it’s a number with a lot of zero’s. When will this year pass from your point of view? Light has to leave what we are looking at and then travel to our eyes for us to see it. Time is no longer a thing when you're traveling at the speed of light. What are your thoughts? In essence, the further light has traveled to us, the further back in time we are seeing. 8 light minutes equals about 93 million miles. It’s a long way to travel in one second but now we’re going to go to much greater distances. If light was instantaneous and we saw everything in the universe as it happens, we would never be able see into the past which would mean it would be much harder, if not impossible to understand the history of our universe. The universe is the way it is today because of all the different things that happened since the Big Bang roughly 14 billion years ago leading up to today. Now when we determine the distances to the stars within our galaxy or even further to the 300 billion other galaxies in the Universe, we are talking about distances that are very, very hard to visualize and comprehend. We won’t know until our technology catches up to our ideas. After one minute hanging onto that photon of light, you will have traveled 11,160,000 miles. But to an outside observer, it took ten years for that object to reach them from ten light years away. As with the story with the train, we’re going to use Bill and Mary again. Or both bodies moving away from each other at 1/2 speed of light each. Now for both Bill and Mary, time will seem to be passing at the same rate to each of them. Time and the speed of light By Richard Costello ---- The Star Man. As you start to slow down, time would begin moving again. telescopes. So let us begin with the speed of light first if for the only reason, I just like thinking about it. All this is for an observer which is located at the center of the chart. Let's say a 90 year old cancer Patient wants to see his grandchildren graduate or marry, would he be able to slow down his cancer by going on a trip? You just can't travel at the speed of light. Looking at the train the player towards the back of the train is about to serve the ball towards his opponent on the side of the table towards the front of the train. When 20 min to them is only like 1 second to you how does it come across? when it is turned on, we see it immediately from any distance on Earth. I'm still having a little trouble grasping this concept. Well, lets say I have a flashlight that was the most powerful flashlight ever made and it was bright enough so that its light over time could travel through the universe. I would guess with the speed of light, it’s a subject most have a hard time understanding because it is out there and it’s sometimes hard just to get your brain to go there, to be able to picture what these theories are implying. That’s over eleven million miles and is called a “light minute”. If he was traveling at 99.999...% the speed of light...and went 10 light years...wouldn't it feel like 10 years to him, but much much longer would pass on earth? I like how you put this, and I would like to learn of your response to this thought: As you speed up time slows down so the inverse must be true, as you slow down time speeds up. when it is turned on, we see it immediately from any distance on Earth. I’ll begin with part of Einstein’s “Theory of Relativity.” One of the things this theory states is that “time” is relative to ones motion and also to the amount of gravity exerted on one. If Mary spent the rest of her life on her ship traveling close to the speed of light, the next 70 years would also to her seem like 70 years. Could you explain where I'm getting it wrong; "10 light years" is the distance light travels in 10 years. If light is traveling for 10 years to make that distance, isn't it still 10 years in the light's perspective? Again, this is not the way things actually are. We are seeing how Orion  looked 1600 years ago because it took that light 1600 years to reach us. One second for you is still one second for you. But it’s true. Light travels so fast we can’t notice it in our everyday lives. The farthest galaxies we can see today, we see them after they have traveled the universe  for the last 13.2 billion years (13 billion, 200 million). The speed of light. I know if you started not knowing what I am talking about, this last sentence didn’t help you much so I’ll explain it a different way which may be better. For example, if you want 20 years and two weeks to pass on earth and two weeks to pass for the astronaut, you could have the astronaut travel to a star 10 light years away at very nearly the speed of light, then stay there for 2 weeks, then travel back to earth. The diagram shows time-dilation, how time passes at different rates depending on ones speed relative to the speed of light. Remember, time is relative to ones perspective. Time and light hold the proof to how the universe started and evolved. Once you travel at the speed of light, there is no more energy to move through time. Light travels that fast and from our vantage of looking at distances from different points on Earth, everything we look at on Earth is too close and light is too quick to reach us from where it came that light seems to be instantaneous. So what’s the deal for calling someone on a phone who is on earth when your travelling at these speeds? But, if I could measure your clock during your journey, I would notice that your clock has come to a near standstill. You and your "spaceship" i presume, will be experiencing time as normal, but 1 year to you is to an outsiders like 14 years or something. Bill and Mary synchronize their watches and then Mary takes off in her space ship and she travels at 99% the speed of light which is 669,600,000 miles an hour. For example, if you were to travel 99.99999% of the speed of light, and do so for a year of Earth time, you would be sitting in your craft at that speed for approximately 4 hours. Which means, on return, the twin which traveled will be younger than the one who stayed on earth. I mean this is pretty cool stuff to think about when you do get it. When you move faster, closer to the speed light, time itself passes slower. Now, when we talk about how fast photons of light move, there is probably nothing faster than light. Even trying to picture the distance to the closest star to us, Alpha Centuari, which. If body A is moving close to speed of light relative to body B, then this is the same as body B moving away from body A at speed of light. Would it hypothetically be possible to "time-travel" on Earth into the future using a pod that would travel in circles at close to the speed of light? It’s the same as with gravity. That’s really a question hopefully future generations will be able answer. You would not feel any different, and if you had a clock, the seconds would seem to be passing by normally. It'd be easier to just travel outward, turn around, and travel back, but yea in concept. The record of the history of the universe is before our eyes to see and decipher. When we look at a galaxy 13 billion light years away from us, that photon has traveled 13 billion years at the speed of 6 trillion miles a year to reach our telescope and our eyes.