If light travels at 670 million miles per hour, then that means in one hour it will travel 670 million miles. At 2 hours it will travel 1214 million miles etc. This to me sounds like a measurement of time, just on such a huge scale that we can’t comprehend it. But in the grand scheme of the cosmos this is not that crazy of a scale. I would think it’s just saying light doesn’t experience time *relative* to us. But Einstein says no- no matter what, light’s speed doesn’t change and, what, relativity just doesn’t matter? It feels like a paradox
In: 222
If you are put in suspended animation while going on a trip of 5 light years, no matter how long it takes you don’t experience any time personally.
That is not the same exactly as what is going on with life but it is the same idea. Basically, nothing with mass can travel at the speed of light because as you approach the speed of light time slows down more and more and it takes more and more energy to accelerate. But any particle traveling at the speed of light is massless and not affected by this. Time still slows down for them though, and in fact slows down so much that it ceases to move altogether.
From the perspective of the photon, to the extent that 1 can imagine such a thing, the universe is a static picture and the photon is a line that exists in it.
Remember that when you’re talking about time (and distance) you always have to specify *whose perspective* you’re talking about. That is the very essence of relativity.
Something traveling at very near the speed of light travels a distance of roughly 670 million miles *per hour* as measured by *you*. That’s *your* hour and *your* 670 million mile measurements. To the travelers perspective those measurements of how far they traveled and how long it took are completely different. To them that same hour could be a few seconds and that 670 million miles just a few feet. Both observations are valid and correct. Two different observations of the same event are what form the basis of relativity.
The reason time and distance are relative is **because** the speed of light is invariant. The reason why you and I can’t agree on whether one hour of time has passed for my journey is because we both agree that the speed of light is moving the same speed, regardless of how fast we’re moving relative to each other.
If your standing on the side of the road and I drive past you and turn on my headlights we’ll both agree that we saw the beam of light move 186,000 miles in exactly one second. However when you think about it that doesn’t make sense because in that one second of time you saw that I moved and you didn’t. So how can the beam of light be 186,000 miles from you and 186,000 miles from me if neither of us are in the same spot by the time the clock strikes one second? The answer is time. You and I *do* see the beam of light travel for 186,000 miles from our perspective in exactly one second, we just don’t agree on what “one second” actually is. By the time you see one second tick on your clock you’ll notice that one second hasn’t yet ticked on mine.
A technically incorrect but simple layman’s way to answer your question is that light doesn’t experience time because the faster something moves (relative to you) the slower it’s clock ticks (relative to yours). The speed of light is the fastest anything can move in the universe, and it moves that speed relative to everything, so light would have a clock that doesn’t tick.
A more nuanced view is to say that it’s really not valid to say light does or doesn’t experience time because that would imply you could see the perspective of light at rest – AKA “standing still” – which is physically impossible. I don’t think this gets to the spirit of your question though. I think the answer that better addresses the spirit of your question is because *time* (and distance) is relative.
None knows if light experience time or not. It’s pure speculation.
What we know is that as you approach the speed of casuality(which is speed of light), everything around you speeds up, you basically go through years in seconds.
If you take those same equations and put your speed as the same of speed of light, then you get something that doesn’t even make sense, you have to divide by zero. So yeah it doesn’t really make sense to even think of time for a massless object like light.
Space contracts as you approach C so in your reference frame you observe it travelling at C over a certain distance but from the photons frame of reference it is emitted, travels zero distance and is absorbed instantaneously. Both reference frames are “true” it’s just that space and time warp to accommodate this, which is counterintuitive, but true
Ok, this is really going to be a stretch, but let’s take a stab at it.
Imagine for a second that you’re a fish sitting still at the bottom of a river. The river has a constant flow rate of, let’s say, 100 gallons a second, and from your frame of reference, this is how you define a second; the time it takes for 100 gallons to pass by you. As long as you’re sitting still, a second is what you would expect it to be.
If you hop into the current and start moving with the river, however, to an outside observer, you’re simply moving along with the river, and one second is one second. You’re not an outside observer, though, and to you, one second has passed only once 100 gallons of water have passed you. If you’re going half as fast as the river is flowing, then one second for you would be two seconds for the observer. To both of you, though, in that time frame, 100 gallons of water have passed you by. So you’re both correct.
Obviously, there are limitations to the analogy, but if we assumed that your biological processes (heartbeat, respiration, other fish stuff) were connected to the rate of water (time) passing you up, then those processes would depend on how quickly you were moving. The closer you get to the speed of the river, the slower your heart appears to beat to the observer, but for you, it’s still beating normally (once per second or what-have-you). If you were capable of going as fast as the river goes, then no water is passing by you, and one second for you will take, to the outside observer, an infinite amount of time to pass.
Sorry, I tried.
Time is a concept, light is a type of matter. We’re rotating on the Earth’s axis at 1,000 mph, orbiting the sun at 67,000 mph, and spiraling around in the Milky Way galaxy as it all collectively makes its way towards Andromeda at about 1.3 million miles per hour within the known universe. I would imagine light can’t experience time in approximately the same way we don’t sense all of the aforementioned items. It is humbling and awe-inspiring though! Also, mildly terrifying. Beware the lurking comet of doom, or quasars, or a banana peel.
Light doesn’t experience anything. A photon is only a carrier of information/energy, simply existing between its creation/emission and reception/absorption. The moment light interacts with any matter, it transmits its information/energy and ceases to exist.
First off, it’s impossible for anything with mass to reach the speed of light. But let’s allow it for this hypothetical.
Think of it like this, from your own perspective, there is no limit on how fast you can go. There is a speed so fast that you will reach your destination instantaneously, no matter how far it is. That’s what it’s like for light and why it experiences no time lapse while traveling. But because of special relativity, any outside observer would see you traveling at the fixed speed of light. Even an observer going 95% the speed of light would see you going the full speed of light relative to them, because the speed of light is a constant no matter how fast the observer is going, and that is all made possible because of time dilation.
Lots of questions from reading this thread.
At what point does time dilation come into effect – does it affect people who travel by vehicle compared to those who walk? If I spend my life travelling by the hyper train to work will I be younger than my twin at some point?
Is there not an ‘omnipresent’ time in the universe? Time experienced from relative perspectives being different but can we actually ‘zoom out’ and consider an overarching clock to things? E.g that chap zooming around has experienced 5 years, that slow one 25 years but really, EVERYTHING just went by for 1 day…?
As OP alludes to, is not the instantaneous nature of a photon’s existence not a paradox to its quantified speed to us? I wish to race alongside a photon as it goes on its way, am I travelling 670 mmph?
If you think of it this way, “Speed of Light = Speed of Time”, everything falls into place. “Speed of time” is really a concept, but, by equating the two, it wraps the theory of relativity up very nicely.
Latest Answers