Why time slows down when approaching the Speed of Light.

Ok, so you’ve heard that nothing can travel faster than the speed of light. (That’s not quite true. The expansion of the universe allows for faster than light travel but that’s another post.) You’re also aware that time slows down the closer you get to the speed of light. You know, the ‘One twin goes off to Alpha Centauri at the speed of light and comes back after 80,000 years but he’s only aged 3 months’ story.

Ever wonder why? Here’s the crib notes.

Everything in the universe always travels exactly at Light Speed. Always.

Time dilation: Special relativity declares a law for all motion: The combined speed of any object’s motion through space and it’s motion though time is always precisely equal to the speed of light.

That’s right, everything. You, me, the computer screen you’re looking at, your grandma’s French toast, Santa Clause… everything.

Everything is traveling through Spacetime: space (the three dimensions we experience and the nine others that m-theory predicts) and time.

Adding the total movement through both space and time always equals light speed. Always. Always. Always.

Space and Time do not exist seperately, the are parts of the same thing, Spacetime.

Since you must travel constantly at exactly the speed of light, when you increase your speed through space, you decrease your speed through time.

Your head (and the rest of you) is traveling through spacetime at the speed of light. But, when you’re at rest (not accelerating) all of your head’s movement is through time, none of it is traveling (accelerating) through space. Every time your head moves (accelerates) through space; in a car, in a plane, in a spaceship… even nodding up and down, some of it’s movement in time is lost since it is now moving through space.

Cool huh.

What about light?

Since light waves use all of their motion to travel through space at Light Speed, they have absolutely no motion through Time. Every photon that has ever been produced exists in an ageless state. (To us, the light seems to move through time but to the photon, time is standing still. This is one of the seemingly odd realizations fo Ensteins Theory of Relativity.) That's why poton's from the early universe don't 'fade out' or do something else. They can't, since for them, time is at a standstill.

The universe ages, light does not.

Reading: The Fabric of the Cosmos: Brian Greene

Comments

[Matthew Z.]

For those people that still cannot grasp the concept of this article, imagine this.
If you are driving a car at 1m/ph you will go slower than a car going at 2 m/ph (which is obvious).
This is because you travel a further distance in a shorter amount of time if you reach a faster speed than something in relation to you.
So, fast velocity=slower time and slower velocity=faster/longer time.
Hope this helped because this just popped up in my mind after reading some of the comments.
If all of you thought of this already, great!
If not, then this could be of great use to you.

[xxxx]

I have read this article and found it to be exactly correct.Though many posts state that this article is confusing, i agree with it but the explanation given is correct.Let me explain
When you are travelling in an aeroplane and you look down and it seems that you are not going anywhere and it fells like you are stationery,but people standing down on the ground see the aeroplane moving rapidly in the sky . The time on the aeroplane feels slow, while on the earth it is fast. this is because the time in aeroplane is 0.00000....(i dont know) seconds slow than that on the ground.If you could travel at about speed of light in a aeroplane("Which is not possible duh!) the difference in time on aeroplane and ground would be huge. For example if you had travelled in that aeroplane for about a month round the world at the speed of light, it would be some years for people on the earth, therefore you would have travelled through time and reached the future!

[Hyoooooo]

Interesting that the only misspelled word is Einstein. Very funy.

[Jeff]

The term theory really bothers me, it hasnt been able to be proven yet, therefore false.

[Tipsy]

Like JEFouie's has asked, my question is, if you were on the spaceship that travels at speed of 80% of light speed and watching a 10 min video that is broadcasted from earth, it would take 50 mins (600s / (100% - 80%) light speed) earth time to play the whole video on the spaceship. So, when you finished watching the video on the spaceship, would you feel like:

1. watching a normal 10 min video? In this case, if you stopped the spaceship and returned to where you started once you finished watching the video, it would be 50 mins for the people on earth, 40 mins after they watched same video.

or

2 watching a 10 min video in 50 mins in slow motion? In this case, you would feel the same amount of time elapses no matter where you are, on the groud or the spaceship, wouldn't you? The difference is that those who on the spaceship experienced everything in slow motion.

[Collier Hageman]

Mark and Leo - Then how do you explain all the experiments that have proven that time slows down for an object more and more the faster that object is moving. This has been conducted many times with atomic and subatomic particles, but most subjectively perhaps with NASA astronauts on the Apollo mission that circled the moon. Two highly synchronized atomic chronometers, (based on atomic decay, or half-life Mark) were used. One stayed on the earth and the other went aboard the space capsule. When the capsule returned there was a slight difference, showing that time had slowed down minutely for the space capsule. And the Apollo craft, though it was the fastest speed humans had ever gone before, only traveled at a tiny fraction of the speed of light. It is not a theory guys, it is a well-proven and established FACT that relative time slows down for an object the faster that object travels.

[Gus]

If time stops at the speed of light, then a particle traveling at the speed of light can be anywhere at any given time. Would that not mean that the same particle could be here with me, travel to you at the speed of light, and exist in both places at the same time?


If time stops at the speed of light, how are we able to measure the speed of light?


If velocity equals distance over time, then distance would have to be divisible by 0, nothing is divisible by 0, therefore would distance cease to exist?

It's hard for me to grasp because I don't have any notion of space-time.

[Andy Baker]

Ye All Wrong God made ze earth peace dudes

[Agreentree]

Does time appear to slow down as you approach death? Many people who have had near death experiences or have actually died say those few minutes seemed like eternity how can this be explained with the theory of relativity or even calculas where you never reach zero or infinity. If time stops at the speed of light, would time be slowing down as you die?

[joebroome]

Is the following statment correct? We stick to the earth because as time passes we are going around a curve in spacetime caused my the mass of the earth, thereby causing Inertia to push us against the earth.

[Benjamin Kelch]

Theres a book called Decoding Reality, written by Vlatko Vedral, that deals with quantum information theory. Basically the basis of QIT is that if you take an atom and you split up one of its electron pairs and you take one to san fran and one to new york they communicate with each other faster than the speed of light. His proof of this is that when you flip the one in san fran's polarity, the one in new york responds by flipping its polarity to keep balanced with the the electron in san fran faster than the speed of light. Where does something like that tie in?

[Benjamin Kelch]

Also, to the people in the comments stating that there is no such thing as time, your being ridiculous. The word time was invented by man yes, but so was every other word. We use words to describe things that happen in our enviroment. The reason we refer to spacetime is that the event in the universe we are talking about is the combined result of the other events that we call space and time. If you want to argue that something doesn't exist, find a philosophical article, not a physics one.

[SStones]

"when you’re at rest (not accelerating) all of your head’s movement is through time, none of it is traveling (accelerating) through space. Every time your head moves (accelerates) through space; in a car, in a plane, in a spaceship"

Why does the author use BOTH movement and acceleration as if they're the same thing? Is one the correction of the other, and which is correct? If "Movement" is correct, it begs the question "In relation to what?" I'm moving at nearly the speed of light in relation to the light that has reflected off of me, which makes me consider that "Acceleration" is correct... But, again, in relation to what? It's easy at slow speeds on earth, you can use the surface of the earth closest to your car to say you're driving at 55MPH... But you're also moving around the earth, and around the sun and away from the center of the universe at 10000 times that speed...
In relation to something on the polar opposite of the universe, that would be going the opposite direction, we're moving away at twice again the last speed... Still not 0.1% of the speed of light, but speed is relative. I'm still moving at darn near the speed of light in relation to the light that has recently bounced off my lazy hide.

[Raw]

Brian is such an amazing author.

[Drocco]

My own thought experiment (and for simplicity assuming this is entirely in a vacuum):
So if astronauts are in a spaceship at 0.9*c (if only!) relative to Houston mission control, and they communicate via lasers or RF (or any signal 'at' the speed of light), wouldn't the radio frequency in Houston be different from the spaceship? If my intuition were correct, spaceship time would be running slower relative to earth time, thus the broadcast frequency would need to be different from the earth's receiving frequency. Does anyone know if there's any effect of relativity on space communications like this? At 0.9c this could be a major frequency difference, but even at our current spaceship speeds it would likely be a measurable frequency difference.

If this effect does not occur, why not? Does converting the signal from the normal 'perceived time' to light speed somehow eliminate the relativity of the reference frames? Does the speed of light transmission path provide a frame of reference for the signals regardless of the sending to receiving relativity?

[riley hartley]

is every thing moving at the speed of light because the universe is expanding at the speed of light

[Show IP]

To get the answer to the topic question, you will need to understand Lorentz transformation. Lorentz transformation gives a mathematical relation that tells that the time slows as we approach the spped of light.

Check out this link:
http://en.wikipedia.org/wiki/Lorentz_transformation

[Me]

i still don't understand... :( sorry...

[Collier Hageman]

Many, perhaps most of these misconceptions and confusion could be cleared up through a clear understanding of spacetime. Most simpy, time is a dimension of space. It is not nebulously related to it somehow - it is an integral and inextricable part of it. And just like the fact that the other three dimensions, length, width, and hieght, are not universally constant, because they are RELATIVE to the observer and to the object or area being observed/measured, the dimension of time is not a constant either, but is RELATIVE to the observer/measurer. And an observer may only be on a fixed point in a RELATIVE sense, because no truly fixed points actually exist. They can't exist on the earth - it rotates on its axis and orbits the sun. They can't exist in the solar system or on the sun - they are both traveling through space as a tiny part of one of the spiral arms of the Milky Way Galaxy as it spins on its axis. They can't exist in the galaxy - it is hurtling through space as well. ALL this motion through spacetime determines our relative passage through the dimension of time. Remember, the sum total of ANY object's velocity through spacetime will ALWAYS add up to lightspeed. On a lighter note, EInstein himself said "When you're talking to a pretty girl, an hour seems like a minute. If you put your hand on a hot stove, a minute seems like an hour. THAT's relativity." This is a beautiful and elegant illustration of his point that time is not a constant. It is relative to every observer.

[Collier Hageman]

And now that experiments have been conducted and confirmed showing that it is possible for some subatomic particles to move faster than light, what next? Following the points I expressed in my earlier post I put forth the proposition that they will be found to have negative mass. (Negative mass?! I can hear the doubters snickering already!) Negative mass has been proposed and written about at length. Do a bit of homework. It's at least as likely as any other explanation, and more so than many.

[Collier Hageman]

And Walker - The expansion of the universe is not occurring at the speed of light. It is expanding at a rate expressed as The Hubble Constant. Generally, it is assumed that the value of the Hubble Constant to be between 50 and 100 km/s/Mpc (which means that for each Megaparsec (Mpc), distant from us they are, galaxies appear to be receding at between 50-100 km/s, one Mpc being equivalent to 3.2 million light years) One group of astronomers and cosmologists place it at 55 km/s/Mps, while others find something around 85 km/s/Mpc. A large number indeed, but it isn't the speed of light. If you study the statement above you might deduce something extremely odd, and you'd be correct. The further away an object is in the universe, the faster it seems to be receding. This does not mean however that the furthest reaches f our universe are expanding at the speed of light. Unless they have negative mass, this just isn't possible.

[r wiseman]

Let me blow this thing wide open. I do understand the theory of relativity. One speeds up and the other slows down. This makes sense to me only because I agree that the speed of light is indeed the speed of the expanding universe. But I've done a lot of thinking about this, and with very very little research mind you, but what if we are all mis led in our understanding as well as our conception of time? I propose time is a measurement of distance. Think about it. The speed of light is 186,000 miles per second if I remember correctly. If the universe exists in a constant state of expansion then in my mind it seems as though the earth and everything else in the universe should be traveling at the same speed. If this was not true we should be able to notice the universe moving in erosion to us. Another contributing factor is that in space an object moving at speed will remain at that constant speed unless an outside force acts upon it. Therefore if you subscribe to the big bang theory (i believe in God so I don't but for the sake of argument I will play along) then every particle resulting from the big bang should be traveling at a constant rate of speed. Therefore the edge of the universe is expanding at exactly the same rate that as you and I through space. Our earth as is rotating which results in the changes of the season as well as the change from night to day. But at the same time, if what I say holds any truth, the earth should also be moving in a linear fashion at a constant rate . The same rate at which the universe is expanding. So we may use time to measure our days ,years, and hours. But I think that since a light year is 186,000 miles per second, one earth second equates to 186,000 miles. To put this into terms I can understand, time is the measurement of distance covered in relativity to accelerating object. If you go down the highway at 70 mph then in one hour the distance you have traveled is 70 miles. If an object on earth is stagnant it sill remains in motion at the speed of the earth as it travels through space. Therefore time still passes because we as objects continue to move through space. But what do I know, I'm just an appliance technician looking up at the stars.

[HyipTree]

I agree with Mark's statement.

[Collier Hageman]

The Hubble Constant, which IS the rate at which the universe is expanding, is not the speed of light, and shows that all parts of the universe are not expanding at the same rate. I have never understood why so many think that belief in the Big Bang means disbelief in God, and vice versa. That God caused the Big Bang isn't even dificult to accept. In fact, it makes it much easier to believe.

[Chris Tollman]

Thanks Collier! The expansion of the universe is actually an expansion of spacetime and not simply an specific speed like c.

I'd like to remind anyone claiming God and the Big Bang are incompatible beliefs, that not too long ago Christians were calling it heresy that the Earth orbits around the Sun... The anti-science movement in our society today is truly disappointing. From the Big Bang, to evolution, to climate change, our progress forward and potentially our future well being will suffer if our children aren't being taught the value (both historically and potentially) of the scientific method.