Moving at the speed of light

[fredreload]

When people say you cannot survive moving at the speed of light, well, it generally means the short term acceleration towards that speed. What if you, increase your speed by 1m/s in the space vacuum, clear away of all debris. Just a vehicle that travels faster and faster by 1m/s in a straight path? Eventually you might accelerate past speed of light, and there would be no vibration from air pressure or gravity, just a straight path in space.

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

Edited March 15, 2018 by fredreload

[Strange]

11 minutes ago, fredreload said:

When people say you cannot survive moving at the speed of light

No one says that, because it is impossible to travel at the speed of light :) 

 

[fredreload]

1 minute ago, Strange said:

No one says that, because it is impossible to travel at the speed of light

 

It is theoretical

[Strange]

No it isn’t. But I will write more when I get home...

[koti]

19 minutes ago, fredreload said:

It is theoretical

Mass aproaches infinity when speed aproaches light speed. Think about it.

[fredreload]

37 minutes ago, koti said:

Mass aproaches infinity when speed aproaches light speed. Think about it.

If you are the observer. Maybe have a recorder moving close to the speed of light?

P.S Koti I got nothing against you, F=ma, acceleration is capped at 1m/s

Edited March 15, 2018 by fredreload

[geordief]

7 minutes ago, fredreload said:

If you are the observer. Maybe have a recorder moving close to the speed of light?

What would  be the purpose of this "recorder" ?

[fredreload]

5 minutes ago, geordief said:

What would  be the purpose of this "recorder" ?

Just something I thought of, it would be moving at the speed of light, or in the reference frame of the light looking at its surroundings. We can capture at 1 trillion frames per second from some Youtube post, but we'll have to reverse engineer this thing, I haven't come up with one =/. Before we sit in a shuttle that moves in the speed of light we'll probably have a recorder sitting in a shuttle moving at the speed of light, or a pet dog.

Edited March 15, 2018 by fredreload

[koti]

17 minutes ago, fredreload said:

If you are the observer. Maybe have a recorder moving close to the speed of light?

No. Mass aproaches infinity when speed aproaches c for a frame in which it is moving in.

[fredreload]

1 minute ago, koti said:

No. Mass aproaches infinity when speed aproaches c for a frame in which it is moving in.

Based on which equation?

[dimreepr]

31 minutes ago, fredreload said:

acceleration is capped at 1m/s

 

that's not acceleration, it's just a speed and not the fastest (not even close).

Time for school.

Edited March 15, 2018 by dimreepr

[geordief]

49 minutes ago, fredreload said:

Just something I thought of, it would be moving at the speed of light, or in the reference frame of the light looking at its surroundings. We can capture at 1 trillion frames per second from some Youtube post, but we'll have to reverse engineer this thing, I haven't come up with one =/. Before we sit in a shuttle that moves in the speed of light we'll probably have a recorder sitting in a shuttle moving at the speed of light, or a pet dog.

What would it be looking at?

 

EDIT:I missed that it  couldn't be "moving at the speed of light" -I misread you to say "moving at close to the speed of light"

Not what you meant ,was it?

Edited March 15, 2018 by geordief

[koti]

19 minutes ago, fredreload said:

Based on which equation?

When the speed of a mass aproaches c, it becomes harder to acclelerate that mass, more and more energy is needed to achieve further acceleration:

 

When the speed is c, the mass is infinite - which is a null statement because its impossible.

Edited March 15, 2018 by koti

[Eise]

1 hour ago, fredreload said:

When people say you cannot survive moving at the speed of light, well, it generally means the short term acceleration towards that speed. What if you, increase your speed by 1m/s in the space vacuum, clear away of all debris. Just a vehicle that travels faster and faster by 1m/s in a straight path? Eventually you might accelerate past speed of light, and there would be no vibration from air pressure or gravity, just a straight path in space.

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

Did you read your own linked article?

Quote

 

A half-myth: It gets harder to push a ship faster as it gets closer to the speed of light
This is a half-myth because it depends on the frame of reference. It is true for those watching from the planetary reference frame. For those experiencing the journey (in the ship's reference frame) it is not true. For both the planetary frame and the ship's reference frame, the ship will change speed in a Newtonian way—push it a little and it speeds up a little, push it a lot and it speeds up a lot. However, in the planetary frame the acceleration will reduce, due to the speed of light being the maximum speed of material objects.

From the ship's frame, the acceleration would continue at the same rate. However, due to Lorentz contraction, the galaxy around the ship would appear to become squashed in the direction of travel, and a destination many light years away would appear to become much closer. Traveling to this destination at subluminal speeds would become practical for the onboard travellers. Ultimately, from the ship's frame, it would be possible to reach anywhere in the observable universe, without the ship ever accelerating to light speed.

 

If you have any questions, please ask.

[Strange]

1 hour ago, fredreload said:

If you are the observer. 

It is relative to the observer that you are moving at close to the speed of light. It is the same observer who sees you mass increasing (and your acceleration decreasing).

Quote

P.S Koti I got nothing against you, F=ma, acceleration is capped at 1m/s

Let's assume you accelerate at a more comfortable 1 g (9.8 m/s²) so you get artificial Earth-like gravity. Then it would take you just under 1 year to reach the speed of light, if you apply traditional kinematics (v = at).

However, in relativity, it doesn't quite work like that. From the observer on Earth your rate of acceleration will gradually decrease and you will get closer and closer to the speed of light but never actually reach it (you will approach it asymptotically).

You can analyse this in terms of your relativistic mass increasing so that, according to F=ma, the constant force produces a decreasing acceleration. Or you can say it is because of the increasing time dilation as seen from Earth.

Either way, you can't reach the speed of light.

47 minutes ago, fredreload said:

Just something I thought of, it would be moving at the speed of light, or in the reference frame of the light looking at its surroundings

It wouldn't be moving at the speed of light, because nothing can travel at the speed of light.

Edited March 15, 2018 by Strange

[swansont]

1 hour ago, fredreload said:

If you are the observer. Maybe have a recorder moving close to the speed of light?

P.S Koti I got nothing against you, F=ma, acceleration is capped at 1m/s

F=ma is a non-relativistic approximation, and even then is not the whole story. F= dp/dt and p is (gamma)mv

IOW, the necessary force to change momentum by some amount increases with increasing speed, and diverges at v=c (all according to an outside observer)

[geordief]

14 minutes ago, Eise said:

Did you read your own linked article?

If you have any questions, please ask.

Is there any useful  distinction between an object being accelerated  using its own resources and one being accelerated externally (eg by use of solar radiation or a laser beam)

 

Is it just that in the former case resources get depleted very quickly whereas in the latter they are practically infinite? 

[swansont]

56 minutes ago, geordief said:

Is there any useful  distinction between an object being accelerated  using its own resources and one being accelerated externally (eg by use of solar radiation or a laser beam)

 

Is it just that in the former case resources get depleted very quickly whereas in the latter they are practically infinite? 

In the former case mass is not a constant, so dp/dt = m dv/dt + v dm/dt  (non-relativistic)

If mass is constant the second term vanishes and we have the familiar F = m dv/dt = ma

 

[koti]

1 hour ago, Eise said:

If you have any questions, please ask.

I have a related question Eise. How do I calculate how much heavier a battery is when its charged compared to when its discharged? 

[Janus]

2 hours ago, fredreload said:

When people say you cannot survive moving at the speed of light, well, it generally means the short term acceleration towards that speed. What if you, increase your speed by 1m/s in the space vacuum, clear away of all debris. Just a vehicle that travels faster and faster by 1m/s in a straight path? Eventually you might accelerate past speed of light, and there would be no vibration from air pressure or gravity, just a straight path in space.

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

The simple answer is that the universe works in such a way as to prevent your ever exceeding c relative to your starting point. 

You are essentially asking what prevents you from constantly accelerating at 1 m/s² until you exceed the speed of light.  If the Universe operated under the Rules of Newtonian physics, nothing.    After 7 years, 21 days, 20 hrs, 47 min and 38 sec, you would be moving faster than light. 

However, we don't live in a universe that follows Newtonian rules, but follows Relativistic ones instead. And one of those differences in rules is in how velocities add together.

Under Newton if you want to get the sum of two velocities, you simply add them together like this, w=u+v.

Thus if you were moving at 1 m/s relative to some reference and then added 1m/s to your current speed, you would be moving at 1+1=2m/s relative to the initial reference.

However, it turns out that this isn't correct. the right way to add the velocities is by

w= (u+v)/(1+uv/c²)

where c = the speed of light in a vacuum or 299,792,458 m/s

Now when you add 1 m/s to 1m/s you get a resultant velocity of 1.9999999999999999777469988789276 m/s  almost, but not quite 2 m/s

At low speeds, this doesn't amount to much, but as the speed increase, the difference starts to mount up.

If you were moving at 0.1c and increased your velocity by 0.1c, you would be moving at .198019802 c relative to the point you were initial moving at 0.1c relative to.

If you boost you speed by another 0.1c, you will now be moving at .2922330097c relative to the initial frame.

Do this 7 more times, and instead of moving at c relative to the initial frame like you would under Newton, you would be moving at 0.7629989373 c.

Each time you add change your speed by 0.1 c relative to your current speed as measured by you,  you add less than 0.1c total change in your velocity. And the closer you get to a total of c, the less change in total velocity you'll end up with, and no matter how you try and add up the velocities, the resultant velocity will always end up being less than c. 

[swansont]

35 minutes ago, koti said:

I have a related question Eise. How do I calculate how much heavier a battery is when its charged compared to when its discharged? 

Take the energy content and divide by c^2

Batteries tell you how long they will run, and at what current, e.g. 1 amp-hour. You also have a voltage.

E = Pt = IVT So 1 amp-hour at 1 V would be 3600 Joules. The mass difference would be 4 x 10^-14 kg

[koti]

19 minutes ago, swansont said:

Take the energy content and divide by c^2

Batteries tell you how long they will run, and at what current, e.g. 1 amp-hour. You also have a voltage.

E = Pt = IVT So 1 amp-hour at 1 V would be 3600 Joules. The mass difference would be 4 x 10^-14 kg

Much obliged.

[MigL]

Came into this kind of late, so all I can add is that it's all experimentally verified, and not just theoretical.

[koti]

On 3/15/2018 at 10:40 AM, Janus said:

The simple answer is that the universe works in such a way as to prevent your ever exceeding c relative to your starting point. 

You are essentially asking what prevents you from constantly accelerating at 1 m/s² until you exceed the speed of light.  If the Universe operated under the Rules of Newtonian physics, nothing.    After 7 years, 21 days, 20 hrs, 47 min and 38 sec, you would be moving faster than light. 

However, we don't live in a universe that follows Newtonian rules, but follows Relativistic ones instead. And one of those differences in rules is in how velocities add together.

Under Newton if you want to get the sum of two velocities, you simply add them together like this, w=u+v.

Thus if you were moving at 1 m/s relative to some reference and then added 1m/s to your current speed, you would be moving at 1+1=2m/s relative to the initial reference.

However, it turns out that this isn't correct. the right way to add the velocities is by

w= (u+v)/(1+uv/c²)

where c = the speed of light in a vacuum or 299,792,458 m/s

Now when you add 1 m/s to 1m/s you get a resultant velocity of 1.9999999999999999777469988789276 m/s  almost, but not quite 2 m/s

At low speeds, this doesn't amount to much, but as the speed increase, the difference starts to mount up.

If you were moving at 0.1c and increased your velocity by 0.1c, you would be moving at .198019802 c relative to the point you were initial moving at 0.1c relative to.

If you boost you speed by another 0.1c, you will now be moving at .2922330097c relative to the initial frame.

Do this 7 more times, and instead of moving at c relative to the initial frame like you would under Newton, you would be moving at 0.7629989373 c.

Each time you add change your speed by 0.1 c relative to your current speed as measured by you,  you add less than 0.1c total change in your velocity. And the closer you get to a total of c, the less change in total velocity you'll end up with, and no matter how you try and add up the velocities, the resultant velocity will always end up being less than c. 

As usual, very insightful, thank you for your post Janus.
 

Edited March 16, 2018 by Phi for All
Question removed by request to start a new thread

[fredreload]

Well the the point should be, what would happen when you achieve a speed faster than light. If nothing happens, well then there's nothing to look for. It could be that once you get pass the speed of light, time start going backwards? You'll need to be at a speed faster than time itself.