# If we could travel at light speed, would travel be 'instantaneous' for us??

by Bad_Wolf 34 Replies latest social current

• ##### Simon
We know that as you approach the speed of light, time slows down, if you were in a spaceship, time goes by quicker on earth.

Not quite, it's that things are relative ... and exactly which is travelling? Against what point? If you are shooting off at the speed of light in a spaceship, for all intents the spaceship is still and Earth is shooting off at the speed of light. You both see time relative to the other.

The problem with all the "everyone else aged" movie plots is that it ignores the return journey, where the reverse would be happening.

if you were able to travel at the speed of light, and you were to go to a planet 1,000 light years away, would you/your body/the spaceship 'age' 1000 years to get there?

You would be experiencing time local to you passing at the same rate in exactly the same way that if you are in the fastest plane, you still age by the exact time that you are in that plane.

The trouble with thinking about time and space in this way is that you assume a "now". There is no universal time of events in the universe to happen before or after others - you simply see things relative to your own locality and the further you look, the further back in time (your time) you are seeing things, but people there would see things where you are being further back in time.

Stick to euclidean space, it's what we're good at.

• ##### waton
S:Stick to euclidean space, it's what we're good at.

or to repeat a hackneyed phrase:

There are only a handful of people in the world that really understand relativity, the speed of light, - -we are so privileged to have them on this forum.

• ##### Vidiot
Anders Anderson - " I saw that movie, but couldn't remember anything related to time dilation (or anything beyond Sandra Bullock outside a space station)."

You're thinking of Gravity.

Intersteller starred Matthew McConaughey.

• ##### Anders Andersen
The problem with all the "everyone else aged" movie plots is that it ignores the return journey, where the reverse would be happening.

No. Higher speed means slower passing of time (as compared to time passing as seen from the reference frame of those with the lower speed). The direction of travel has no influence on this. So both on the way out as the way back the high speed traveler will age slower than those left behind.

Such is the weirdness and counterintuitive effect of special relativity.

You're right though that in the reference frame of the high speed traveler time will pass at the same speed as usual.

• ##### Anders Andersen
Higher speed means slower passing of time (as compared to time passing as seen from the reference frame of those with the lower speed).

This is actually a very poor explanation by the way ðŸ¤£ðŸ¤£ðŸ¤£ Naturally both frames of reference are moving with regards to the other, and in each frame of reference it appears that time outside the own frame of reference moves slower.

Regardless, any high speed traveler will appear to have aged less than someone who didn't reach the high speeds. The apparent paradox is solved because the traveler experiences acceleration, which causes asymmetrical time dilation (whatever that may be lol)

Forgetting the part that we would need literally an infinite amount of energy to get to the speed of light in the first place, time would stand still for someone travelling at the speed of light. So from the traveller's point of view, they'll arrive at their destination at the very moment they hit the speed of light.

Is an infinite amount of energy truly needed or is that just an 'illusion' from the viewpoint of bystanders? If so then the math itself is also based on the viewpoint of bystanders. If TIME itself ceases when an object hits the speed of light, bystanders will see it blasting through space, but as you pointed out, when arriving their destination it is the instant they hit the speed of light for them. When hitting the speed of light, does the energy also cease to age or be consumed? If that's the case, then it's only the energy to approach and get close to the speed of light and there should be an adjustment for time dilation. The only easy way I can think to explain this concept would be if you were to build a fire and must heat it to 10,000 degrees and make it last for 5 years. Imagine degrees is speed and years is light years. If the energy is measured at 10,000 degrees and lasting 5 years, vs if it hits 10,000 degrees and the 5 years is instant since time stopped for it (thought from our perspective it's lasting for 5 years).

Not sure if this is considered when saying needing infinite energy to reach light speed or if this concept was not considered when those theories were made.

• ##### iwantoutnow

Anything traveling at the speed of light does not age.

So the light we see from distant galaxies is say 5 billion years old to us, but it has not aged since the photon was emitted during fusion in the sun it originated in.

We can never travel at the speed of light, it's not possible.

It's complicated and there are many relativistic issues, but generally the faster you go the more massive you become, requiring more energy go get that extra speed, making you more massive, requiring more energy...

The point is as you approach the speed of light, it's impossible to have enough energy to overcome your mass.

Keep in mind, the only things in the universe that travel at the speed of light are things that start at that speed.

Nothing starts off slow and builds to it. Gravity waves and Light in all its forms (gamma rays to Radio Waves)
ALL 0 Mass things:)

This is a great simple video.

Anything traveling at the speed of light does not age.
So the light we see from distant galaxies is say 5 billion years old to us, but it has not aged since the photon was emitted during fusion in the sun it originated in.
We can never travel at the speed of light, it's not possible.
It's complicated and there are many relativistic issues, but generally the faster you go the more massive you become, requiring more energy go get that extra speed, making you more massive, requiring more energy...
The point is as you approach the speed of light, it's impossible to have enough energy to overcome your mass.

The universe is said to be almost 14 billion light years old, because of detecting galaxies/mass from almost 14 billion light years away. That would mean when the universe originated, the mass was about instantly moved, meaning it had to be at speed of light or I've seen claimed faster. Then I've seen it explained about expansion, and the movement was as if everything was on a balloon, and the balloon (space) only expanded and what was on it, with it. But if that's only the case, then how do you get colliding galaxies and such? If you put a bunch of dots on a balloon and blow it up, they never touch each other, just move further away equally. So did mass at origin of universe move speed of light or faster? If so then it's not impossible, we just haven't figured it out yet.

• ##### iwantoutnow

The expansion of the universe (inflation) has nothing to do with speed of particles or waves.

But - there probably are galaxies past the edge of what we call the visible universe that RELATIVELY speaking are moving in relation to us faster than the speed of light.

Space expansion is exempt from the conversation of matter or energy or gravity moving.

Some great books that go into all this with you not needing to be a physicist are:

• Edge of the Universe: A Voyage to the Cosmic Horizon and Beyond
• Time Reborn: From the Crisis in Physics to the Future of the Universe
• Now: The Physics of Time - and the Ephemeral Moment That Einstein Could Not Explain
• The Universe: Leading Scientists Explore the Origin, Mysteries, and Future of the Cosmos

• ##### GLTirebiter

...time would stand still for someone traveling at the speed of light.

Considering the speed of light relative to what frame of reference (an appropriate pun in this context)? As Intrepid Spaceman Spiff accelerates to light speed (relative to us) and red-shifts into invisibility, he would seem to stop aging as observed here on Earth. But our inter-galactic hero experiences ordinary aging in his own frame of reference.

It all follows from there being no special reference point in space and time from which all measurements are made, and the total energy of the universe being independent of where you are and how fast you're moving when you measure it.

The models of Special and General Relativity seem strange and counter-intuitive, but they work, which is why they are accepted.

Project Gutenberg has an online copy of Einstein's own explanation, which is comprehensible to non-experts.