If time stops for something moving at light speed, then how do photons move?

a reply to: new_here
It gets a little complicated if you add up all the different motions. The milky way galaxy is moving one way, but it's rotating and we are in the part that's moving backwards relative to its motion so those two largest motions partially cancel each other out. Here's the speed of the Milky way:

Cosmic Microwave background

From the CMB data it is seen that our local group of galaxies (the galactic cluster that includes the Solar System's Milky Way Galaxy) appears to be moving at 627±22 km/s relative to the reference frame of the CMB

The speed of the Earth relative to the CMB is less for now, but once we rotate to the other side of the Milky way and the rotational velocity is in the same direction as the overall motion, we should be going faster than the Milky way:

the peculiar velocity of the Earth relative to the comoving cosmic rest frame as the planet moves at some 371 km/s

So you can say 371 km/s but of course there are smaller wiggling motions that pale in comparison such as the others you mentioned. For example the speed of the Earth's orbit around the sun is less than 1/10 of that, averaging just under 30 km/s. Speed due to Earth's rotation is faster than most airplanes but very slow relative to those and depends on latitude.

a reply to: Arbitrageur

Thanks, I've also thought about the fact that, as the Earth orbits the Sun, half of the year it is moving opposite (retrograde?) the direction that the Solar System is traveling, so the relative speed of the Earth-to-Galaxy must change 4 times in a year. Like, say, the Milky Way and Solar System progressing in one direction, but the Earth is going the opposite direction at one point as it traverses the Sun. Then it goes "lateral" before it whips around the Sun to play 'catch up' and actually must travel faster than the Sun to continue its orbit. Am I seeing this right in my head, lol?

Fascinating to think about... space, time, relative velocity, and how its experienced from various reference points. The Earth IS the center of the Universe, and everything DOES moves around it... when you name it the point of reference! Because in Space, everything is moving relative to everything else. We'd have to step outside of the Universe to see if there was anything completely anchored, immobile. Right?

I just made my brain hurt.

Nice thread s&f cheers

a reply to: new_here

Just taking the big 2, the expansion of the universe, and then the speed we move around inside the milky way, would overpower the relative speeds of things going on in our own solar system. Just saying.

a reply to: Arbitrageur

So, the faster you go the closer things appear to be to you?

Since moving near the speed of light would make a planet seem closer than just moving 10, 000 miles per hour, then maybe at light speed when time stops... there is no distance and it is everything is all one as Light?

originally posted by: arpgme
a reply to: Arbitrageur

So, the faster you go the closer things appear to be to you?

Since moving near the speed of light would make a planet seem closer than just moving 10, 000 miles per hour, then maybe at light speed when time stops... there is no distance and it is everything is all one as Light?

A naive extrapolation of what happens just under the speed of light to the speed of light might suggest that at first, but on closer examination we find this extrapolation to be flawed.

The reason in relativity is that in every reference frame, light must appear to travel at the speed of light. If you extrapolate as you suggest, light can't travel at the speed of light in the frame of reference of light because there would be no passage of time and thus no velocity, therefore such a frame of reference isn't consistent with the theory of relativity.

If a photon had mass then I would be more inclined to view light as a particle. Instead I view the mathematical concepts of the photon as an energy wave moving through a sea of electrons.

How does a wave at sea perceive the other waves nearby? The waves that you are in time and direction with will just look the same as you travel through the universe for billions of years or however long it takes for that wave to crash upon its shore. This is why we can see further back in time the further and deeper we look into space.

a reply to: arpgme

So you have a photon released from a star, a million plus light years in the past . The distance between that star and us contains a great deal of matter. The odds of it getting to our retina, must be in the billions to one . The Universe is diffused with hydrogen , not to mention all the rest of the dust . Where its energy could be expended and lost to us. Then theoretically, surely our observation of the Universe should be very limited, to a few light years at least, and not out to the billions.

Which makes it look like the Photon , when released and travelling at the speed of light, has exited Newtonian space, if time for it ceases relative to the rest of the Universe surely it has to, (Exit Newtonian space) that is. The Observation of the Photon, requires it to collide with a tool of consciousness, our eyes, or an intermediary acting as proxy for consciousness like a telescope. So how real and robust is our model of the Universe? doesn't it start to look like the Photon, has a preprogramed destination, when it re enters Newtonian space?

Well its all relativistic so it wasn't time that stopped everthing else moved is speeding away from the referemce point making it appear like it stopped but it hasn't not at all.

a reply to: kwakakev

This is why we can see further back in time the further and deeper we look into space.

You had me surfing your wave analogy right up until the last sentence. (This is no criticism or dismissal of your statement!) It is a plea for someone to please help me grasp this: How a location in Space (a Where) becomes a When! I get that a star I see in the night sky may have 'died' long ago yet its light is still travelling, thus I am seeing a star from the past that no longer exists. I understand the general concept of 'seeing the past' in space.

I do not get the 'further back in time, the further and deeper we look into space' aspect, which implies there is an actual location/region of space where the past, the history of everything IS. Are we talking about the location of the Big Bang? Because if all light travels at the same speed, why is there any remnant of 'old light' still there to be seen? Would it not have traveled away from the center at the same rate as we (our Solar System) did?

a reply to: arpgme

The theory of general relativity only applies to objects with mass and Photons have got no mass.

From an observers point of view, Time slows down around things of mass. The more mass, the more time appears to slow down. Objects gain mass the faster they go. Have an object of mass travelling close to the speed of light and they would gain huge amounts of mass and gravity. The more time would slow around them.

Photons have no mass.
No mass, No Gravity.
Time would appear normal around them.
No time dilation.

originally posted by: new_here
a reply to: Arbitrageur

Thanks, I've also thought about the fact that, as the Earth orbits the Sun, half of the year it is moving opposite (retrograde?) the direction that the Solar System is traveling, so the relative speed of the Earth-to-Galaxy must change 4 times in a year. Like, say, the Milky Way and Solar System progressing in one direction, but the Earth is going the opposite direction at one point as it traverses the Sun. Then it goes "lateral" before it whips around the Sun to play 'catch up' and actually must travel faster than the Sun to continue its orbit. Am I seeing this right in my head, lol?

Fascinating to think about... space, time, relative velocity, and how its experienced from various reference points. The Earth IS the center of the Universe, and everything DOES moves around it... when you name it the point of reference! Because in Space, everything is moving relative to everything else. We'd have to step outside of the Universe to see if there was anything completely anchored, immobile. Right?

I just made my brain hurt.

Therein lie the flaws and shortcomings of language. We mean to express something but sometimes we can't or confuse others with our words.

I can say "The Earth is flat," and I wouldn't be "wrong" from my perspective. For all I know the Earth is flat. Unless I go in an airplane or in a space shuttle to actually see the curvature of the Earth, I wouldn't know otherwise.

I could say the Earth's population is X... and I would be wrong because in the few seconds if me typing this sentence, the Earth's population has already gone up or down (+ or -) X.

originally posted by: JameSimon
a reply to: arpgme

The theory of general relativity only applies to objects with mass

Not true.

After all, one of the most important early experimental tests of general relativity was starlight deflection, a.k.a. gravitational lensing of light.

and Photons have got no mass.

True.

originally posted by: mbkennel

originally posted by: JameSimon
a reply to: arpgme

The theory of general relativity only applies to objects with mass

Not true.

After all, one of the most important early experimental tests of general relativity was starlight deflection, a.k.a. gravitational lensing of light.

and Photons have got no mass.

True.

If photons have no mass, which is right because they travel at the speed of light. Add in the fact because of this they are time locked, at the moment they start their , journey from some distant galaxy, how is it after some five billion years of travel, that some photons that were created at the same time arrive a few seconds apart on the detectors?. It cant be that, they have encountered space time distortions in the fabric of space, because it would have been the same for all the incoming packets. It can only mean that the inflation of the Universe after all this time has separated them , to cause the delay. Is the conclusion that, the Universe has inflated and separated them during the long journey.

So if they have no mass, then its not gravity pulling light into Black holes, it must be compression of space time, around the holes, that do it?

a reply to: anonentity
The metric expansion of space has an effect but not when we bounce a laser off a reflector on the moon and time how long it takes for the light to bounce back to Earth. That takes about 2 seconds in our frame of reference and inflation has no measurable effect.

The photon has no valid frame of reference so it doesn't make a lot of sense to say time stands still in the photon's reference frame.

A photon doesn't need mass for gravity to affect it.

physics.ucr.edu...

The force of gravity affects both light and all material bodies; since both carry energy, but only the bodies carry mass, it follows that gravity will affect anything carrying energy. This conclusion lies at the root of the construction of Einstein's equations which describe gravity.

originally posted by: Arbitrageur

A photon doesn't need mass for gravity to affect it.

It doesn't need a mass. It's got a donk.

Or a stress-energy tensor, which is about the same thing.

originally posted by: DaRAGE
From an observers point of view, Time slows down around things of mass. The more mass, the more time appears to slow down. Objects gain mass the faster they go. Have an object of mass travelling close to the speed of light and they would gain huge amounts of mass and gravity. The more time would slow around them.

Photons have no mass.
No mass, No Gravity.
Time would appear normal around them.
No time dilation.

Light is the vibration of some of the properties of space time, the electric and magnetic fields of space time. Unless a photon is absorbed by something it is immortal. It may also be a way of measuring the local time form some outside viewpoint. Light travels at 300,000,000 meters per second. How long that second is to what we experience is dependent on the local rate of time. Near massive objects the second is longer, in interstellar space the second can be much shorter.

I agree that there is no time dilation.

The earth does travel through space fast enough for there to be some time dilation effects.

a reply to: Arbitrageur

Time and Space are all relative. Theory of relativity anyone?

By analogy

Since a photon is without mass, time simply limits a photons velocity. Mass requires time for actions like kinetic energy or changes like decay to occur. A photon is just a vibration moving through the local time so it is not a "consumer" of time. Since photons do not "use" time then it cannot have dilation.