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the speed of light question

y0ssar1an22

a question that has puzzled me for a while...

1: car A and car B have a velocity towards each other of 100 kph. they are approaching each other is 200kph.

2: if car A and car B are doing the same, but at the speed of light why are they not approaching each other at (2)(speed of light)?

if the rules of physics hold for scenario 1, why not scarios 2?

is there a simple explanation here?

i dunno, maybe we just don't have an answer?

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Chancer3001

What we see is only light hitting our eyes.

So when we look at a distant planet we only see what light it emitted many many years ago for example.

If i start travelling towards that planet , does what i can see speed up?

Gregor Samsa

y0ssar1an22 wrote: »

your perception and experience of time is half of a static observer: has that been proven, or a conjecture?

i think infinity shouldn't be allowed. it essentially means 'going that way for a long time, but we really know' so lets call it quits'.

Time dilation has been demonstrated through experimentation:

https://en.m.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

It’s something that scientists have to take into account with certain aspects of interplanetary space travel, due to the very high speeds involved.

As for infinity, it’s a pretty important mathematical construct. It’s very different from a sequence of unknown length: it’s a sequence where you know the length has no end.

Here’s something to chew on. So the sequence of natural numbers (whole, positive numbers) is infinite - for any number you can think of, you can always add another number to it and go higher. So there’s no end to the sequence. But, the sequence of even numbers - which only contains every second natural number - is also infinite - 2,4,6,8 etc goes on forever. The even numbers are a subset of the natural numbers - they are contained with it and do not from it’s totality - yet both sets are infinite, and therefore one is not smaller or larger than the other.

Gregor Samsa

Chancer3001 wrote: »

What we see is only light hitting our eyes.

So when we look at a distant planet we only see what light it emitted many many years ago for example.

If i start travelling towards that planet , does what i can see speed up?

No, it doesn’t speed up, but the frequency is the light increases so you will see the object as more blue. If you were travelling away from the object, you’ll see it as more red. It’s the Doppler Effect, same as you will hear the siren of an ambulance coming towards you as a higher pitch than one static or going away from you. It’s much more pronounced and easier to observe with stars or galaxies rather than planets in our solar system, as the speeds involved are much greater, but it actually applies to anything you’re moving towards or away from at any speed.

[Deleted User]

The speed of light limit also doesn’t rule out getting from a to b faster than light you just can’t yourself exceed this speed but using things like worm holes or theoretical methods of bending or folding space you can in theory travel to places faster than light can. Even in Star Trek they need to be inside a “warp bubble” in order to achieve speeds faster than light and there is a theory about how something similar might be possible in reality - the Alcubierre drive.

It should also be noted that the universe already has clear examples of objects having move apart at speeds faster than light. Physicists have discovered based on their calculations (how they realise this is a very long answer) on the expansion of the universe from the Big Bang that objects are too far apart than would be possible even at the speed of light so this lead to the development of the theory of inflationary expansion. Which in a nutshell means that the space between objects expanded at speeds faster than the speed of light got a very short time. Because it was space that expanded between objects rather than the objects themselves moving apart no laws of physics are broken.

A good analogy would be to draw two dots beside each other on a deflated balloon. When you blow up the balloon the objects are now far apart but they haven’t moved rather than balloon has expanded and resulted in more space between then.

[Deleted User]

Gregor Samsa wrote: »

Time dilation has been demonstrated through experimentation:

https://en.m.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

It’s something that scientists have to take into account with certain aspects of interplanetary space travel, due to the very high speeds involved.

As for infinity, it’s a pretty important mathematical construct. It’s very different from a sequence of unknown length: it’s a sequence where you know the length has no end.

Here’s something to chew on. So the sequence of natural numbers (whole, positive numbers) is infinite - for any number you can think of, you can always add another number to it and go higher. So there’s no end to the sequence. But, the sequence of even numbers - which only contains every second natural number - is also infinite - 2,4,6,8 etc goes on forever. The even numbers are a subset of the natural numbers - they are contained with it and do not from it’s totality - yet both sets are infinite, and therefore one is not smaller or larger than the other.

Infinity plus 1. Yeah, got you snookered now :pac:

Giblet

y0ssar1an22 wrote: »

i always thought physics was essentially 1 + 1 = 2; a physical quantifiable 'thing' that you can solve for?'

it seems, there is so many unknowns, that people are happy to go along with the that, without any proof?

Maths is 1+1 = 2. You use Maths to build models in Physics, but it's just a model.

You can create many models for the same phenomena, depending on your need.

Every model is tested again and again to ensure it holds up under certain conditions and each can be used depending on how much accuracy you need. Newtonian models might represent 99% of how things work and has easier Maths to use, but we use different models for 99.9%, which require the Maths to get far more complex, therefore harder to use.

Science doesn't have proof, only Maths does, which is why Science adjusts. It's a good system.

Sky King

Did you hear about the supersonic fart?

You can smell it before you hear it.

Smiles35

There was a great thread on here years ago. A first poster came on chalenging everyone to explain the old Greek term Ehther. The best bit was he would sporaticly quote pieces from Einstiens private letters. Must have been these https://www.amazon.co.uk/Born-Einstein-Letters-1916-1955-Friendship-Uncertain/dp/1349729116

The long and the short of it is. I don't have to bother with those relative velocity diagrams anymore after that.

You, see. They can't actually measure the speed of light. I can accept that. As a man, I have a limitation.

ILoveYourVibes

y0ssar1an22 wrote: »

a question that has puzzled me for a while...

1: car A and car B have a velocity towards each other of 100 kph. they are approaching each other is 200kph.

2: if car A and car B are doing the same, but at the speed of light why are they not approaching each other at (2)(speed of light)?

if the rules of physics hold for scenario 1, why not scarios 2?

is there a simple explanation here?

i dunno, maybe we just don't have an answer?

They do ...its called superluminal speed or FTL ..(faster than the speed of light)

Thus the story ...

Actually he was faster than a speeding bullet ......but anyway...im talking junk!

blinding

Wanderer78 wrote: »

This stuff always fascinated me, but by fcuk is it a mind bender, physics is weird!

Perhaps it you thats weird and physics if fine !

ILoveYourVibes

blinding wrote: »

Perhaps it you thats weird and physics if fine !

am i fine too?:o

blinding

Chancer3001 wrote: »

What we see is only light hitting our eyes.

So when we look at a distant planet we only see what light it emitted many many years ago for example.

If i start travelling towards that planet , does what i can see speed up?

Not faster than the Speed of Light.

ILoveYourVibes

blinding wrote: »

Not faster than the Speed of Light.

I think he just enters a different time zone.

blinding

ILoveYourVibes wrote: »

am i fine too?:o

Oh Yeah !

c montgomery

y0ssar1an22 wrote: »

i always thought physics was essentially 1 + 1 = 2; a physical quantifiable 'thing' that you can solve for?'

it seems, there is so many unknowns, that people are happy to go along with the that, without any proof?

It's too complex an area to explain fully in a boards post. Relativity is one of the most tested theories in physics and its use is ubiquitous.
It took me years to get my head around it.

ILoveYourVibes

blinding wrote: »

Oh Yeah !

I wuv u. x

AllForIt

This is a very good lecture in this subject area even for a layperson to follow from Yale Uni.

Wanderer78

blinding wrote: »

Perhaps it you thats weird and physics if fine !

id happily accept, that both of us are weird, ive studied it for a while, it really is weird, and so am i

[Deleted User]

y0ssar1an22 wrote: »

a question that has puzzled me for a while...

1: car A and car B have a velocity towards each other of 100 kph. they are approaching each other is 200kph.

Nope, they aren't. They are approaching each other at 199.999999999998285... km/h according to relativistic velocity addition.
https://en.wikipedia.org/wiki/Velocity-addition_formula

I think you are confusing the idea that relativistic equations only apply when things are moving fast. In fact, they always apply, and Newtonian mechanics is simply a good approximation at low speeds.

Here is a graph of the above equation of your scenario of the speed of both cars being the same (u=v). Red is Newtonian and blue is Einstein. The x-axis is the speed of each car relative to a stationary observer (in units of speed of light) and the y-axis is the speed of each car according to each other (also in units of speed of light).

As each car approaches the speed of light relative to the observer, the speed of one car relative to the other incorrectly approaches twice the speed of light according to Newton (2 on the y-axis) and correctly approaches the speed of light according to Einstein (1 on the y-axis). Also, note that both agree well at low speeds and it's not that the relativistic equations "kick in" at some arbitrary high speed.

Eleven Benevolent Elephants

Time dilates and space contracts as you approach the speed of light.

Each car will be travelling at 99.999999999999 % the speed of light but they will still only approach each other at 99.999999999 %

Btw, the cars will never reach the speed of light, it will just keep getting heavier and heavier as it approaches c. Only massless objects can reach c, photons have no rest mass but do have mass simultaneously.

Wanderer78

oh the nerds are out, yippeee!

Tiger20

I haven't a clue what any of this is about, but enjoying trying to understand. A question that comes to my mind is this.....what and how would the speed of light mean/influence to a blind person? If the SOL is an observed phenomenon, then is it relevant to unobservation? Is the SOL therefore not a human construct, because to an atom it is irrelevant. At what about the thing called spooky something or other, (spooky science I think) where the actions of an object here can affect another apparently unconnected object billions of miles away at the same time. By whatever means these objects are connected, the connection must be faster than the SOL as the reaction is instantaneous.
And another question I have previously wondered is this. Say you are flying on a plane to a destination, ETA 2 hours from now. The place you are flying to currently exists, but does not yet exist relevant to you on the plane. It will only come into existence for you once you arrive. As such your destination is notional to you. So where does the time that you arrive at come from? Is it created as you fly there? Or does the time already exist in reality, just like your destination does, but you haven't experienced it yet. Therefore is all time not already in existence!
Dont know if what I am asking makes any sense to an uneducated mind like mine, but find it all pretty mind blowing.

EmmetSpiceland

Tiger20 wrote: »

At what about the thing called spooky something or other, (spooky science I think) where the actions of an object here can affect another apparently unconnected object billions of miles away at the same time. By whatever means these objects are connected, the connection must be faster than the SOL as the reaction is instantaneous.

Quantum entanglement. ‘Spooky action at a distance‘, is how Einstein referred to it.

blinding

EmmetSpiceland wrote: »

Quantum entanglement. ‘Spooky action at a distance‘, is how Einstein referred to it.

Which could suggest that either time or space does not exist in that realm or that neither exist. Which could mean I am right next to you / part of you / in you :eek::eek:

lawred2

Gregor Samsa wrote: »

There’s an interesting phenomenon called time dilation that happens the faster you travel. It’s not something you can notice at human speeds (unless you’re measuring with an incredibly accurate atomic clock), but the faster you go, the slower time goes relative to observers travelling slower than you. If you go at 90% of the speed of light, your perception and experience of time is half of a static observer. You’ll actually age half as slow as them. If you travel at the speed of light, for you, time stops, and you’re therefore bot able to observe anything in the universe. Basically at that speed, for you, nothing else exists except yourself, and time is infinite.

If you have any mass, your mass will also become infinite at the speed of light. It would therefore take an infinite amount of energy to get you there. Your length also reduces in the axis you’re travelling the faster you go. And again, the effect is infinite at the SOL.

So, if you were a solid object of any size, it would take infinite energy to get you to the speed of light, and once you got there, you’d have infinite mass, zero length, time would stop and to you the universe would cease to exist. This clearly means that it’s impossible for anything with mass to travel at the speed of light. It also shows that nothing can travel faster than light (it would take more than infinite energy to do it, which can’t exist, and you’d end up more than infinitely massive and less than zero in length - again, things that just can’t happen)

Fortunately, photons and other particles that do travel at that speed don’t have any mass, so they don’t have to worry about the physical effects.

That was brilliantly clear and eloquent. Nice one

blinding

Tiger20 wrote: »

I haven't a clue what any of this is about, but enjoying trying to understand. A question that comes to my mind is this.....what and how would the speed of light mean/influence to a blind person? If the SOL is an observed phenomenon, then is it relevant to unobservation? Is the SOL therefore not a human construct, because to an atom it is irrelevant. At what about the thing called spooky something or other, (spooky science I think) where the actions of an object here can affect another apparently unconnected object billions of miles away at the same time. By whatever means these objects are connected, the connection must be faster than the SOL as the reaction is instantaneous.
And another question I have previously wondered is this. Say you are flying on a plane to a destination, ETA 2 hours from now. The place you are flying to currently exists, but does not yet exist relevant to you on the plane. It will only come into existence for you once you arrive. As such your destination is notional to you. So where does the time that you arrive at come from? Is it created as you fly there? Or does the time already exist in reality, just like your destination does, but you haven't experienced it yet. Therefore is all time not already in existence!
Dont know if what I am asking makes any sense to an uneducated mind like mine, but find it all pretty mind blowing.

There has to be some sort of consistency to make it / fake it that the Matrix actually exists.

All of it may well be in the Imagination of something very small that invented the whole darn thing out of boredom ! !

[Deleted User]

Tiger20 wrote: »

I haven't a clue what any of this is about, but enjoying trying to understand. A question that comes to my mind is this.....what and how would the speed of light mean/influence to a blind person? If the SOL is an observed phenomenon, then is it relevant to unobservation? Is the SOL therefore not a human construct, because to an atom it is irrelevant. At what about the thing called spooky something or other, (spooky science I think) where the actions of an object here can affect another apparently unconnected object billions of miles away at the same time. By whatever means these objects are connected, the connection must be faster than the SOL as the reaction is instantaneous.
And another question I have previously wondered is this. Say you are flying on a plane to a destination, ETA 2 hours from now. The place you are flying to currently exists, but does not yet exist relevant to you on the plane. It will only come into existence for you once you arrive. As such your destination is notional to you. So where does the time that you arrive at come from? Is it created as you fly there? Or does the time already exist in reality, just like your destination does, but you haven't experienced it yet. Therefore is all time not already in existence!
Dont know if what I am asking makes any sense to an uneducated mind like mine, but find it all pretty mind blowing.

There is a lot to entangle there (pun intended), but I'll focus on the "spooky" bit you mentioned and leave the rest to others.

The spooky thing you are referring to is what is known as "spooky action at distance", i.e. quantum entanglement. When two particles that are created are entangled, something known as their "spin" will have opposite values. What these spin values actually are is inherently probabilistic, but if you measure the spin of one of the particles, you then therefore "instantly" know the spin of the other (regardless of the distance between both particles) as they are opposites, which seems to contradict the main premise of relativity, namely that nothing (including information) can travel faster than the speed of light.

However, this does not violate relativity. You do indeed instantly know what the spin of the second particle is, but this not because information has been transmitted instantaneously. The inherent probability of what the spin of the first particle is "entangled" with the inherent probability of what the spin of the other particle will be. Once the spin of the first particle is measured, the spin of the second particle is then known based on this probability. Information is not transmitted and, most importantly, entanglement cannot be used to intentionally transmit information at a speed greater than the speed of light as it is an inherently probabilistic phenomenon.

(It's obviously a bit more complicated than that, and I tried my best to not mention anything about a wave function collapsing, but hopefully that will do.

)

blinding

Deleted User wrote: »

There is a lot to entangle there (pun intended), but I'll focus on the "spooky" bit you mentioned and leave the rest to others.

The spooky thing you are referring to is what is known as "spooky action at distance", i.e. quantum entanglement. When two particles that are created are entangled, something known as their "spin" will have opposite values. What these spin values actually are is inherently probabilistic, but if you measure the spin of one of the particles, you then therefore "instantly" know the spin of the other (regardless of the distance between both particles) as they are opposites, which seems to contradict the main premise of relativity, namely that nothing (including information) can travel faster than the speed of light.

However, this does not violate relativity. You do indeed instantly know what the spin of the second particle is, but this not because information has been transmitted instantaneously. The inherent probability of what the spin of the first particle is "entangled" with the inherent probability of what the spin of the other particle will be. Once the spin of the first particle is measured, the spin of the second particle is know based on this probability. Information is not transmitted and, most importantly, entanglement cannot be used to transmit information at a speed greater than the speed of light due to this inherent probability.

Perhaps the Universe does not waste time / space on what it already knows !

skallywag

Gregor Samsa wrote: »

Time dilation has been demonstrated through experimentation:

https://en.m.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

It’s something that scientists have to take into account with certain aspects of interplanetary space travel, due to the very high speeds involved.

Closer to home Time Dilation needs to be factored into GPS systems to make them work correctly. Meaning the run of the mill GPS system in your car etc would not work correctly without adjusting for Time Dilation.

Here is an interesting read (albeit fiction) on Tachyons by the way ...

https://en.wikipedia.org/wiki/Timescape

Funkfield

Best thread on Boards in a while ☺️