# What happens when objects travel at the speed of light?

• asutosh
in summary, people asking about what would happen when massive objects move at c are snubbed with a condescending one-liner?

#### asutosh

Hello ,

I have this question in my mind from long time. There are two travelers in two trains and one observer on ground(Stationary). One train is traveling at 99.99% speed of light and another train is traveling at speed of light . My question is that the person who is at light speed train what he is going to see ? How they are all going to see each other?

(sorry my English is not very good)

Regards,
Asutosh

Massive objects cannot travel at c. Your question has no answer.

Assume that the massive objects are traveling at c.

Non physical assumptions lead to nonsense results.

asutosh said:
Assume that the massive objects are traveling at c.
This assumption simply cannot be made within the framework of special relativity.

Alright instead of train make it as space shuttle which can travel @ c.

asutosh said:
Alright instead of train make it as space shuttle which can travel @ c.
Are you serious? Aren't space shuttles massive objects?

asutosh said:
Alright instead of train make it as space shuttle which can travel @ c.

Objects with mass cannot travel at c. It is physically impossible, you might as well be asking how many corners a square circle has.

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because we living in type0 civilization.

asutosh said:
because we living in type0 civilization.

The civilization I live in makes sense, perhaps you live in a different one.

JeffKoch said:
The civilization I live in makes sense, perhaps you live in a different one.
I don't know...have you heard Rick Perry speak lately? :tongue2:

asutosh said:
Alright instead of train make it as space shuttle which can travel @ c.
The problem with your original question isn't that trains are much slower than space shuttles. The problem is that you asked us to make an assumption that's logically inconsistent with special relativity. The assumptions of SR don't contradict each other, but they imply that massive particles have speeds <c in inertial frames. So when you asked us to assume that a massive object moves at c, you asked us to contradict the theory we were going to use to answer the question.

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asutosh said:
because we living in type0 civilization.

Unless you have a type∞ civilisation it's not going to happen it takes infinite energy or infinite time to accelerate an object with mass to c. Therefore it isn't possible.

Ok cool denge!

I have a question myself...

I've read a lot of threads where people ask questions about "what would happen..." when some mass/observer is "moving at c".

Why is it that responders pretend to act dumb and pretend that they don't understand the question, saying there is no answer, saying it is a non-physical assumption, does not compute... etc?

These responders know good and well that the uninitiated are asking a perfectly good question, but making a tiny error in their question's rigor when saying "going at c" rather than saying "approaching c", "almost c", "very close to c", "near c", or "99.99999998% of c"...

It only takes an additional phrase in the answer to clarify that "at c" is not possible for masses, but "as close to c as you want to get without getting there" is possible for thought experiments. Then the examination of the adjusted question may be considered physically/mathematically.

Why the snub rudeness to people that don't indicate they know the special insider way to properly phrase high speed mass questions concerning light dynamics?

If this was being done nicely to lead the questioner to the appropriate way to reform the question with alignment to rigor as in the Socratic method that would be fine, but the way people just drop the obtuse one liners and act like they don't have a clue as to what the question pertains just seems obnoxious.

When someone makes the "mass going at c" mistake, why not immediately suggest an adjustment to the thought experimental conditions to correct the lack of rigor and proceed, rather than snubbing the questioner with terse "pretended ignorance"?

bahamagreen said:
I have a question myself...

I've read a lot of threads where people ask questions about "what would happen..." when some mass/observer is "moving at c".

Why is it that responders pretend to act dumb and pretend that they don't understand the question, saying there is no answer, saying it is a non-physical assumption, does not compute... etc?
You are assuming that the OPs of these questions are simply using "at c" by mistake and really want to ask about "near c". In my experience this is not the case, rather such threads are down to a misunderstanding that traveling at c for a massive object is down to what is possible and not because we simply don't know how.

bahamagreen said:
When someone makes the "mass going at c" mistake, why not immediately suggest an adjustment to the thought experimental conditions to correct the lack of rigor and proceed, rather than snubbing the questioner with terse "pretended ignorance"?
Agreed. So, why didn't you do this rather than spending your whole post lecturing the rest of us here for being dumb and insensitive to the OP?

"...travelling at c for a massive object is down to what is possible..."

That phrases has no meaning to me.

Ryan_m_b said:
In my experience this is not the case, rather such threads are down to a misunderstanding that traveling at c for a massive object is down to what is possible and not because we simply don't know how.
bahamagreen said:
"...travelling at c for a massive object is down to what is possible..."

That phrases has no meaning to me.
What I mean is that in my experience the OP is of the understanding that the reason science says "nothing can travel at c" is down to our not being able to figure out how to do it yet. This is a common, but incorrect, understanding hence why I said it was a misunderstanding because most of the time OPs don't realize that it is physically not possible.

bapowell said:
Agreed. So, why didn't you do this rather than spending your whole post lecturing the rest of us here for being dumb and insensitive to the OP?

Don't you see that I did do just that? The correction is inherent within the criticism. Perhaps the OP now knows how to ask the question in a way that will attract polite and thoughtful answers? And perhaps those answering now have a nice technique with which to address questions that are flawed by lack of rigor?

bahamagreen said:
I have a question myself...

I've read a lot of threads where people ask questions about "what would happen..." when some mass/observer is "moving at c".

Why is it that responders pretend to act dumb and pretend that they don't understand the question, saying there is no answer, saying it is a non-physical assumption, does not compute... etc?

These responders know good and well that the uninitiated are asking a perfectly good question, but making a tiny error in their question's rigor when saying "going at c" rather than saying "approaching c", "almost c", "very close to c", "near c", or "99.99999998% of c"...

It only takes an additional phrase in the answer to clarify that "at c" is not possible for masses, but "as close to c as you want to get without getting there" is possible for thought experiments. Then the examination of the adjusted question may be considered physically/mathematically.

Why the snub rudeness to people that don't indicate they know the special insider way to properly phrase high speed mass questions concerning light dynamics?

If this was being done nicely to lead the questioner to the appropriate way to reform the question with alignment to rigor as in the Socratic method that would be fine, but the way people just drop the obtuse one liners and act like they don't have a clue as to what the question pertains just seems obnoxious.

When someone makes the "mass going at c" mistake, why not immediately suggest an adjustment to the thought experimental conditions to correct the lack of rigor and proceed, rather than snubbing the questioner with terse "pretended ignorance"?
The problem is that no matter how fast you are "going", that is, no matter how much you have accelerated in the past, when you measure the speed of light, it is still c, not some tiny fraction of c because you are "traveling at 99.999999998%c. So the reason why most people are asking the question about traveling at c is that they already know that going a tad bit under c is relatively the same as not moving at all.

Either way, people need to learn that you don't have to accelerate at all in order to "see" what it is like to travel at almost the speed of light, they can just transform a Frame of Reference in which they are at rest into a Frame of Reference that is moving at 99.99999998%c and see what happens to them. But they cannot transform into a Frame of Reference that is moving at c because the equations for the Lorentz Transformation have a factor that results in a division by zero when v=c.

bahamagreen said:
Don't you see that I did do just that? The correction is inherent within the criticism. Perhaps the OP now knows how to ask the question in a way that will attract polite and thoughtful answers? And perhaps those answering now have a nice technique with which to address questions that are flawed by lack of rigor?
I disagree with your assumption that the OP means "in the limit as v approaches c" versus "when v equals c". Perhaps you haven't been around the forums long enough to know that questions regarding what happens when v = c are quite common; questions regarding what happens when v approaches c no so much, because such questions are already addressed in terms of special relativity (which most people have a basic understanding of.) You are missing the point that people are typically keenly interested in understanding physics at the limits themselves -- they see the equations breaking down and get excited (how does a photon perceive time, for example, is a frequently asked question here, or what happens at the very center of a black hole, or what was the universe like at t=0.) So, it would be wise to reserve your judgment of those of us who have been on these forums for a while, and do care about the questions, and do spend time to answer them carefully and engagingly.

## 1. What is the speed of light?

The speed of light is a physical constant that represents the maximum speed at which anything in the universe can travel. It is approximately 299,792,458 meters per second in a vacuum.

## 2. What happens when an object reaches the speed of light?

According to Einstein's theory of relativity, as an object approaches the speed of light, its mass increases infinitely and it would require an infinite amount of energy to accelerate it further. This is why it is impossible for any object with mass to reach the speed of light.

## 3. Can light ever slow down?

In a vacuum, no. Light will always travel at the speed of light. However, in other mediums such as air or water, light can slow down due to interactions with the particles in those mediums.

## 4. What happens to time when objects travel at the speed of light?

According to the theory of relativity, time appears to slow down for an object as it approaches the speed of light. This phenomenon is known as time dilation and has been observed in experiments.

## 5. Is it possible to travel at the speed of light?

No, it is not possible for objects with mass to travel at the speed of light. However, it is theoretically possible for massless particles, such as photons, to travel at the speed of light.