Effect of CMB (cosmic microwave background) on objects at relativistic speeds

In summary, it is possible for an object to interact with the cosmic microwave background radiation, however, it is not just a significant fraction of c. The object would also be damaged by other forms of matter and radiation.
  • #1
rorix_bw
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A hypothetical question relating to

1) moving a physical object at a significant % of c.

2) interaction with the cosmic microwave background radiation

Is it the case that doppler effect and time dilation means that the CMB is going to be physically damaging to the object?

Further what would happen if a source of microwave energy (e.g. from a transmitter) was directed towards such an object?

This is from a sci-fi discussion, but I just got this idea and I don't know what would happen.
 
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  • #2
Sort of, but first off, it doesn't just have to be a significant fraction of c, it has to be ultrarelativistic, i.e., very, very close to c. Also, there are other forms of matter and radiation besides the CMB that would fry you much worse than the CMB. I think the interstellar medium (mostly hydrogen) would be the most damaging. Starlight from the forward direction would also be Doppler shifted into the gamma spectrum.
 
  • #3
rorix_bw said:
A hypothetical question relating to

1) moving a physical object at a significant % of c.

2) interaction with the cosmic microwave background radiation

Is it the case that doppler effect and time dilation means that the CMB is going to be physically damaging to the object?

I know that there is the possibility of some objects to interact with CMB. It is the case of high energy electrons that can react with CMB photon through inverse Compton scattering. This leads to a detectable distortion of CMB spectrum. It is a way used to detect clusters of galaxies and the anisotropies. This effect is called Sunyaev Zeldovich effect.
 
  • #4
A Doppler-shifted blackbody spectrum is itself a blackbody spectrum. So at about 150 m/s less than c (time dilation factor = 1000) the CMB will be a blackbody with a temperature around 2700 K, close to stellar surface temperatures.

bcrowell is pretty smart, so he may be right that matter will be a probelm before the CMB. I am not sure, I would have to see a calculation, but certainly the CMB isn't the only hazard to ultrarelativistic travel.
 
  • #5
Interesting, then I might be on the right track: beaming microwaves in all directions could possibly act as a shield against such a hyopthetical projectile. It's off topic for this thread however I guess. Although it seems to be correct that such projectiles would initiate a nuclear reaction on impact.

EDIT: I think i already mentioned hitting stray hydrogen atoms and space dust in that other thread.
 
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1. How does the CMB affect objects traveling at relativistic speeds?

The CMB, or cosmic microwave background, has a negligible effect on objects traveling at relativistic speeds. This is because the CMB is a uniform background radiation that is isotropic, meaning it is the same in all directions. As a result, objects moving at high speeds do not experience any noticeable changes in their motion due to the CMB.

2. Can the CMB cause time dilation for objects moving at relativistic speeds?

No, the CMB does not cause time dilation for objects traveling at relativistic speeds. Time dilation is caused by the relative velocity between two objects, not by any external radiation. While the CMB does have a specific reference frame in which it appears isotropic, this frame is not preferred over any other inertial frame of reference.

3. Is there any measurable effect of the CMB on objects moving at relativistic speeds?

The only measurable effect of the CMB on objects moving at relativistic speeds is the Doppler shift of the CMB radiation. This shift is due to the relative motion between the CMB and the moving object and can be measured as a change in the frequency of the CMB radiation. However, this effect is very small and is only significant for objects traveling at extremely high speeds, close to the speed of light.

4. Does the CMB affect the energy or momentum of objects at relativistic speeds?

No, the CMB does not affect the energy or momentum of objects traveling at relativistic speeds. The CMB is a low-energy radiation that does not have enough energy to significantly alter the energy or momentum of high-speed objects. Additionally, the CMB is isotropic, meaning it exerts equal force in all directions and therefore does not exert any net force on moving objects.

5. Can the CMB be used as a reference frame for objects at relativistic speeds?

No, the CMB cannot be used as a reference frame for objects moving at relativistic speeds. While the CMB is a unique reference frame in which the CMB radiation appears isotropic, it is not preferred over any other inertial frame of reference. Objects moving at high speeds can use any inertial frame as their reference frame, and the CMB does not provide any special advantages.

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