China’s Large High Altitude Air Shower Observatory (LHAASO) has detected two photons with energies exceeding 1 peta-electron-volt (quadrillion electron-volts or PeV). The photon at 1.4 PeV is the highest energy photon ever observed.
The Voyager 1 spacecraft now at the immense distance of 18.5 billion kilometers (145 AU) from earth. In 2017, thrusters were operated by NASA to adjust the orientation of the spacecraft; the signal from the spacecraft took 19 hours and 35 minutes to reach an antenna in Goldstone, California.
Background radiation is a natural part of the environment. The largest source of background radiation exposure comes from the natural radioactivity in rocks and soil and the inhalation of naturally occurring radon that seeps from the ground into our buildings.
The observation of gravitational waves from cosmic events opens a dramatic new window on the universe. The first four events observed by gravitational waves were merging black holes with masses between 7.5 and 35 solar masses.
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