Question

Neutrinos are experimentally determined to have an extremely small mass. Huge numbers of neutrinos are created in a supernova at the same time as massive amounts of light are first produced. When the 1987A supernova occurred in the Large Magellanic Cloud, visible primarily in the Southern Hemisphere and some 100,000 light-years away from Earth, neutrinos from the explosion were observed at about the same time as the light from the blast. How could the relative arrival times of neutrinos and light be used to place limits on the mass of neutrinos?

a) Neutrinos and light must always arrive simultaneously, limiting neutrino mass.

b) Neutrinos travel slower than light, allowing mass estimation from time delay.

c) Neutrinos and light travel independently, providing no mass information.

d) Light travels slower than neutrinos, allowing mass estimation from time delay.

Answer 1

The observation of neutrinos arriving from the 1987A supernova at nearly the same time as light suggests their mass must be very small, as they traveled close to the speed of light, allowing scientists to establish an upper limit on their mass.

Step-by-step explanation:

The observation that neutrinos from the 1987A supernova arrived at Earth approximately at the same time as light from the explosion allows scientists to place an upper limit on the mass of neutrinos. Since neutrinos have mass, they cannot travel at the speed of light, but if their mass is small enough, their speed can approach that of light. The fact that neutrinos were detected within hours of the light from the supernova implies that they must have traveled nearly as fast as light, thus indicating that their mass must be extremely small. The accurate measurement of the time difference between their arrival and the light's arrival can be used to constrain the mass of the neutrinos even further, using the principles of relativity.