Is there time dilation at the speed of light? How do we know?

Question

Nobody has ever gone the speed of light, so how can time dilation at that speed be measured? It appears that it is assumed in physics that there is time dilation at the speed of light. This is because the trend towards time dilation works----as an object accelerates, time dilation increases with increasing speed. But at light speed, what really happens? Perhaps the trend is completely reversed and there is no time dilation at all. Or, time passes by rapidly instead, rather than being dilated.

Could it be that time dilation for an accelerating object is only a physical consequence directly created by matter? Maybe only matter undergoes time dilation. Non-physical, massless entities (such as light) do not experience time dilation.

If matter itself is the reason why an object experiences time dilation, is it possible to alter the quantum parameters of matter so it circumvents time dilation as it accelerates? Is it possible to create time dilation free matter, even when it is traveling at relatively slow speeds?

Answer 1

"Is there time dilation at the speed of light? How do we know?"



We tested for it.

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html

... have for more than 100 years.



"Nobody has ever gone the speed of light, so how can time dilation at that speed be measured?"



Done. See the link.



"But at light speed, what really happens?"



Matter can never go that fast. Electrons are really light, and we cannot even get them to go that fast. Not enough energy available.



"Could it be that time dilation for an accelerating object is only a physical consequence directly created by matter?"



Sure, since "aging" is "directly created by matter".



"Maybe only matter undergoes time dilation. Non-physical, massless entities (such as light) do not experience time dilation."



What is red shifted light, then?



"is it possible to alter the quantum parameters of matter so it circumvents time dilation as it accelerates?"



In English, please?



"Is it possible to create time dilation free matter, even when it is traveling at relatively slow speeds?"



Sure, just move it out of space.



"Could it be that "as matter moves closer to the fabric of space-time, time dilation occurs"?"



Already covered in another question. No.



"Light has two natures,..."



Also covered in another question. Photons do not experience time, light (as in collections) do.

Answer 2

We know because time dilation occurs at speeds much less than the speed of light. The degree of time dilation is directly related to how close to the speed of light an object is moving. The slower an object moves, the less the time dilation; and the faster the object moves, the greater the time dilation. A few decades ago two atomic clocks were perfectly synchronized and one was sent into orbit around Earth, while the second one stayed on the surface of Earth. When the clock that orbited the Earth was returned to the Earth, it was very, very, very slightly behind (millionths of a second) the clock that remained on Earth's surface, even though the elapsed time for one second on both clocks remained exactly the same.



That's how we know.

.

Answer 3

Objects with mass cannot move at the speed of light- they can get as close as they want, but that speed is not attainable however hard you try.



In fact, the equations describing time dilation will not allow you to input the speed of light (if you try, you end up dividing by zero and the equation fails.



So basically, it cannot be calculated for light speed, but that's ok, as you can never get to that speed anyway.



There is also no such thing as "time dilation free" matter- time dilation is a fundamental law of physics that cannot be beaten. While it only applies to objects with mass, there is no known way to change that or exempt anything from it.

Answer 4

"But at light speed, what really happens?"

Assuming General Relativity to be correct (and we have no viable alternative to it right now), the answer is "you can't go light speed". So there is nothing that "really" happens.



It is consistent with GR that objects that could go that fast would view contraction of the rest of the universe. They would find their destination would be zero distance away and it would therefore take zero time to arrive. We see this that all massless particles (such as photons) appear to be immortal. They do not decay or age in any manner until interacting with the destination.



So, we have evidence that the conclusions of GR are correct.

GR has specific predictions that massless particles at the speed of light do not age during travel.

We have no evidence that contradicts this idea.



Time dilation appears to be a property of space and time, not a property of matter.

Answer 5

You do not have to go at the speed of light to experience time dilation. It start, in a very small way' as soon as you start to move.



This was proven using experiments on the space shuttle in the 90's. Thecspacecshuttle was the fastest MANNED object in existence at the time -- 17500 MPH. [the fastest ever was an Apollo moon shot at 25000 MPH]



Special high accuracy atomic Clocks were used, clocks based on the vibrations of a Cesium atom. One clock was kept van the ground, the other in the space shuttle.



Since the space shuttle travels at 17500 for several days at a time, a very small but measurable time dilation was measured.



Yes, the spacec shuttle adtronauts REALLY ARE a few fractions of a second younger than their friends on earth!

Answer 6

I think the idea is that since space and time are equivalent, the faster you go through space, the faster you go through time.



That said, it's not so much that there's time dilation at the speed of light as that there isn't time, period.

Answer 7

(1) An object doesn't need to accelerate to experience time dilation. It only needs to move at speeds close to speed of light, as viewed from external system of reference.



(2) Time dilation was experimentally proven.

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html

Also, if you don't take it into account, GPS is imprecise, so another confirmation.

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html



(3) Nothing that possesses rest mass can travel at the speed of light.



(4) If you're seriously interested in physics, I recommend taking a free course in special relativity.

http://ocw.mit.edu/courses/physics/8-20-introduction-to-special-relativity-january-iap-2005/

Answer 8

This has been verified already using high speed aircraft

Answer 9

LHC proved it occurs