Does anything travel at speed c in the atmosphere.

[jonathang]

I understand the electromagnetic spectrum travels below speed c in Earth’s atmosphere. Is there any part of the spectrum which remains at speed c, or indeed anything which travels at speed c in the atmosphere?

Thanks

 

[dauto]

The atmospheric effect on the speed of electromagnetic radiation becomes more and more negligible the higher the energy of the incoming photon. gamma rays will travel very close to c through the atmosphere.

 

[Claude Bile]

Most portions of the EM spectrum have a phase velocity in excess of c.

Some portions I suspect have a group velocity in excess of c, but are highly absorbing at these wavelengths - so you ultimately cannot trasmit information faster than c.

Claude.