# What is the maximum speed we can travel at through space?

#### Mart943

What is the maximum speed we can travel through space?

#### billslugg

The laws of physics limit speed to the speed of light, 299,792,458 m/s exactly. The meter is based upon the speed of light which is based on the second which is the amount of time it takes for 9,192,631,770 unperturbed ground-state hyperfine transitions of the cesium-133 atom.

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COLGeek

#### Mart943

The laws of physics limit speed to the speed of light, 299,792,458 m/s exactly. The meter is based upon the speed of light which is based on the second which is the amount of time it takes for 9,192,631,770 unperturbed ground-state hyperfine transitions of the cesium-133 atom.
Can you tell me what that is relative too?

#### billslugg

The speed of light, in a vacuum, is the same relative to any observer in an inertial (non-accelerating) frame of reference.
If the source is moving, their clock is running slower due to relativity. If the receiver is moving, space is Lorentz contracted. Both effects combine to make it such that no matter how fast the source or the observer are moving, each one measures the speed of a light beam to be exactly c.

Mart943

#### Mart943

Thank you for the enlightenment. Now another question on the same subject.
What or how is the maximum speed limited from going faster? I am referring to a physical object rather than light. The speed of light would appear to be merely a form of measurement of speed. If an object went faster than the speed of light it would perhaps split in 2 time zones?

#### billslugg

As an object with rest mass goes faster, it becomed endowed with more and more kinetic energy. Energy has mass, thus the object becomes more massive. This is "relativistic mass" and must be accelerated along with the rest mass. More mass requires more energy to accelerate thus becomes even more massive. If the object were to reach the speed of light it would be infinitely massive which is not possible, thus it cannot reach or exceed c.

Uhm!

#### Pogo

Yeah, it's a hard thing to wrap your head around, but, that's what relativity indicates. It's even been shown: a few years ago, a single nucleus (I forget what element) was detected that had a kinetic energy equivalent to a baseball pitch, doing the math, it relativistic mass pretty much agreed with relativity. So, it would take you humongous amounts of fuel to accelerate to anywhere near a small fraction of c.

Mart943

#### Mart943

So, there is reflected light and generated light? Our sun generates light, which our earth reflects. That is what I was taught. Am I correct in interpreting you to mean that our earth also generates light of its own accord? Also, all mass will generate its own light. After all, everything is traveling and not all in the same direction.

#### billslugg

Every object generates electromagnetic waves of a frequency depending on the temperature of the object.
The Sun generates EM waves in the visible spectrum since it is at 5,000°K. The Earth generates EM waves in the far infrared at 9 microns due to its temperature
of 20°C.
The ice cold deep sky at 3K radiates in the millimeter radio spectrum.
All objects can reflect light, to varying degrees.
As an object goes faster and faster and gains kinetic energy, it does not change temperature as measured by those on the object.
Those people seeing the object coming towards them see the light blue shifted to a higher temperature.
Those seeing it recede in the distance see it red shifted to a lower temperature.

#### Mart943

I'm sorry Bill, but you are blinding me with science. In my simple words, I suspect that the speed of the object is measured relative to its own origin. It's temperature , colour and other properties being determined relative to its origin and not where it actually is any time later. Every other place except the origin would perceive the object based upon its own location. Would this be correct?

#### billslugg

The speed of an object, the color of an object , the rate its clock is going and how far away it is, are all seen differently by every observer moving relative to it.

Speed, color, clock rate and distance are "relative" to different observers. There is only one thing that is always the same as measured by everyone and that is the speed of light. Everyting else looks different to each observer in a different frame of reference.

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#### Helio

I'm sorry Bill, but you are blinding me with science. In my simple words, I suspect that the speed of the object is measured relative to its own origin. It's temperature , colour and other properties being determined relative to its origin and not where it actually is any time later. Every other place except the origin would perceive the object based upon its own location. Would this be correct?
Yes.

At the turn of the century (early 1900s), the universe was getting much bigger with the idea that spiral nebulae were other galaxies, and extremely far away. Their speeds were an issue as well. So the view that space itself is an absolute frame of reference -- all speeds are to be judged relative to it -- began to create problems in the physics.

When Einstein fixed the speed of light to one single value (for any given medium, like space), then he solved this growing problem. He called his theory his "Invariance Theory" for this reason. He demonstrated that any reference frame, as you mentioned and often they are called "intertial frames", can each apply known physics without having to reference their speed with the space itself.

At least, this is what I read and I think I have it right.

#### karlp295

What is the maximum speed we can travel through space?
I believe it is 99.999999% of the speed of light, isn't it? Relative to a stationary point of course, whatever that means in the context of the Universe.

#### billslugg

The fastest particle observed in a cosmic ray shower has 23 nines. There is no limit to how many nines there can be.